Entry - *607423 - PROTEIN O-MANNOSYLTRANSFERASE 1; POMT1 - OMIM
* 607423

PROTEIN O-MANNOSYLTRANSFERASE 1; POMT1


Alternative titles; symbols

ROTATED ABDOMEN, DROSOPHILA, HOMOLOG OF; RT


HGNC Approved Gene Symbol: POMT1

Cytogenetic location: 9q34.13   Genomic coordinates (GRCh38) : 9:131,502,918-131,523,799 (from NCBI)


Gene-Phenotype Relationships
Location Phenotype Phenotype
MIM number
Inheritance Phenotype
mapping key
9q34.13 Muscular dystrophy-dystroglycanopathy (congenital with brain and eye anomalies), type A, 1 236670 AR 3
Muscular dystrophy-dystroglycanopathy (congenital with impaired intellectual development), type B, 1 613155 AR 3
Muscular dystrophy-dystroglycanopathy (limb-girdle), type C, 1 609308 AR 3

TEXT

Description

The POMT1 gene encodes protein O-mannosyltransferase, an enzyme that catalyzes O-mannosylation of proteins, an important protein modification in eukaryotes that is initiated by an evolutionarily conserved family of O-mannosyltransferases. POMT1 shares sequence similarity with protein O-mannosyltransferases of S. cerevisiae. In yeast, these enzymes are located in the endoplasmic reticulum (ER) and are required for cell integrity and cell wall rigidity. POMT1 also shows similarity to the Drosophila 'rotated abdomen' (rt) gene, which, when mutated, causes defects in myogenesis and muscle structure (Jurado et al., 1999).


Cloning and Expression

Using homology with Drosophila rt, Jurado et al. (1999) identified an EST for POMT1. By 5-prime cDNA walking performed by vector/insert PCR, and by anchor PCR of fetal brain RNA, they cloned the full-length POMT1 cDNA. The deduced 725-amino acid protein has a calculated molecular mass of about 82.5 kD. POMT1 contains 7 to 12 putative transmembrane regions and a C-terminal ER membrane retention signal. POMT1 shares 40% identity with rt, and it averages 54% similarity with the yeast Pmts. Northern blot analysis revealed a diffuse band of 3.1 to 3.2 kb in all tissues tested, with slightly stronger expression in skeletal muscle and heart. RNA dot blot analysis revealed ubiquitous expression, with maximum levels in testis and high levels in fetal brain and pituitary. By this method, expression in skeletal muscle and heart was not significantly higher than expression in other tissues. RT-PCR revealed several mRNA splice variants. Southern blot analysis indicated Pomt1 expression in all mammalian DNAs tested, as well as weak but specific signals in bird, reptile, and amphibian DNAs; no signal was detected in fish or plant DNAs.


Gene Structure

Jurado et al. (1999) determined that the POMT1 gene contains 20 exons and spans about 20 kb. The initiator ATG is located in exon 2. There are a variable number of 17- to 19-nucleotide tandem repeats within intron 13. Jurado et al. (1999) identified 8 different allelic variants carrying 36 to 56 repeats within normal chromosomes. The 56-repeat allele was the most frequent. Intron 2 also contains a (CA)n microsatellite.


Mapping

By somatic cell hybrid analysis, radiation hybrid analysis, and linkage analysis, Jurado et al. (1999) mapped the POMT1 gene to chromosome 9q34.1. The POMT1 locus is flanked by markers D9S260 and D9S7293 on 9q34 (Beltran-Valero de Bernabe et al., 2002).


Molecular Genetics

Mutation in the POMT1 gene can cause 3 different forms of muscular dystrophy-dystroglycanopathy (MDDG): a severe congenital form with brain and eye anomalies (type A1; MDDGA1, 236670), formerly designated Walker-Warburg syndrome (WWS) or muscle-eye-brain disease (MEB); a less severe congenital form with impaired intellectual development (type B1; MDDGB1; 613115); and a milder limb-girdle form (type C1; MDDGC1; 609308), previously designated LGMD2K (LGMDR11).

Beltran-Valero de Bernabe et al. (2002) identified several families in which Walker-Warburg syndrome (MDDGA1; 236670), a severe recessive congenital muscular dystrophy associated with defects in neuronal migration that produce complex brain and eye abnormalities, was caused by mutation in the POMT1 gene (see 607423.0001-607423.0003).

In a Japanese boy with Walker-Warburg syndrome, Kim et al. (2004) identified a homozygous 3-bp deletion in the POMT1 gene (607423.0004).

In 5 unrelated Turkish patients with autosomal recessive limb-girdle muscular dystrophy and mental retardation, but without structural brain abnormalities (MDDGC1; 609308), Balci et al. (2005) identified a homozygous founder mutation in the POMT1 gene (607423.0005).

Van Reeuwijk et al. (2006) identified compound heterozygous mutations in the POMT1 gene (see, e.g., 607423.0006-607423.0009) in 5 patients from 4 unrelated families with a milder form of WWS, referred to as 'congenital muscular dystrophy plus impaired intellectual development' (MDDGB1; 613155). Van Reeuwijk et al. (2006) also identified 7 novel mutations in the POMT1 gene in 7 unrelated patients with classic WWS.

In 3 unrelated patients with a severe form of congenital muscular dystrophy, D'Amico et al. (2006) identified compound heterozygous mutations in the POMT1 gene (607423.0010-607423.0014). None had structural brain abnormalities.

Bouchet et al. (2007) identified mutations in the POMT1 gene in 13 (32%) of 41 families in which at least 1 fetus had severe cobblestone cortex (type II lissencephaly), as observed in patients with WWS. The minimum diagnostic criteria included hydrocephalus, agyria, thickened leptomeninges filled with neuroglial ectopia, disorganized cortical ribbon, and cerebellar dysplasia. Mutations in the POMGNT1 (606822) and POMT2 (607439) genes were identified in 6 (15%) and 3 (7%) families, respectively. Overall, mutations were identified in 22 of 41 families included in the study. Definitive pathogenic mutations were not identified in the FKRP (606596), FKTN (607440), or LARGE (603590) genes.

Godfrey et al. (2007) identified POMT1 mutations in 8 of 92 patients with evidence of a muscular dystrophy due to defective glycosylation of alpha-dystroglycan (DAG1; 128239). One patient had WWS, 1 had MEB (607423.0015), 3 had congenital muscular dystrophy, and 3 had limb-girdle muscular dystrophy. All had low IQ and about half had structural brain abnormalities.

Mercuri et al. (2009) identified POMT1 mutations in 17 (21%) of 81 Italian patients with a dystroglycanopathy. Thirteen patients had muscular dystrophy, 2 had MEB, and 2 had WWS. Six patients had a normal MRI, 1 of whom had a severe dilated cardiomyopathy. All but 1 had mental retardation and microcephaly. No clear-cut genotype-phenotype correlations were observed; however, the more severe phenotypes appeared to be associated with mutations predicted to result in severe disruption of the gene.


Animal Model

Willer et al. (2004) found that during embryogenesis, the mouse Pomt1 gene is prominently expressed in the neural tube, the developing eye, and the mesenchyme. They noted that these sites of expression correlate with those in which the main tissue alterations are observed in patients with Walker-Warburg syndrome. Willer et al. (2004) inactivated a Pomt1 allele by gene targeting in mouse embryonic stem cells and produced chimeras transmitting the defect allele to offspring. Although heterozygous mice were viable and fertile, the total absence of homozygous Pomt1 -/- pups among the progeny of heterozygous intercrosses indicated that this genotype is embryonic lethal. Analysis of the mutant phenotype revealed that homozygous null mice suffered developmental arrest around embryonic day (E) 7.5 and died between E7.5 and E9.5. The Pomt1 -/- embryos presented defects in the formation of the Reichert membrane, the first basement membrane to form in the embryo. The Reichert membrane is a thick multilayered membrane between the parietal endoderm cells and the trophoblast cells of rodents; it is thought to function to allow free access of nutrients to the embryo while excluding maternal cells (Salamat et al., 1995). The failure of this membrane to form in the Pomt1 -/- embryos appeared to be the result of abnormal glycosylation and maturation of dystroglycan that may impair recruitment of laminin (see 150320), a structural component required for the formation of Reichert membrane in rodents. Willer et al. (2004) concluded that the targeted disruption of Pomt1 in mouse represents an example of an engineered deletion of a known glycosyltransferase involved in O-mannosyl glycan synthesis.


ALLELIC VARIANTS ( 20 Selected Examples):

.0001 MUSCULAR DYSTROPHY-DYSTROGLYCANOPATHY (CONGENITAL WITH EYE AND BRAIN ANOMALIES), TYPE A, 1

POMT1, GLY76ARG
  
RCV000003394...

In a family with Walker-Warburg syndrome (MDDGA1; 236670), previously reported by Cormand et al. (2001), Beltran-Valero de Bernabe et al. (2002) identified a homozygous transition, 226G-A, in exon 3 of the POMT1 gene, predicting a gly76-to-arg (G76R) substitution. The parents were first cousins of Turkish origin. After 3 spontaneous abortions, a male was born presenting with severe hydrocephalus with dilatation of the third and fourth ventricles and minimal cortical development, no visible gyri, bifid cerebellum, and hypoplasia of the vermis and of the cerebellar hemispheres. A cerebellar cyst was observed. The corpus callosum appeared to be present. Microphthalmia on the left and exophthalmia on the right were noted. The genitalia were hypoplastic. Serum creatine kinase levels were highly elevated at more than 2,000 U/l. The patient died at age 7 months. Another affected child, whose DNA was used for genetic analysis, died 15 minutes after birth. She presented with severe hydrocephaly, encephalocele, and bilateral cleft lip.


.0002 MUSCULAR DYSTROPHY-DYSTROGLYCANOPATHY (CONGENITAL WITH EYE AND BRAIN ANOMALIES), TYPE A, 1

POMT1, GLN303TER
  
RCV000003395...

In affected members of 2 families of Turkish origin with Walker-Warburg syndrome (MDDGA1; 236670), previously reported by Cormand et al. (2001), Beltran-Valero de Bernabe et al. (2002) identified homozygosity for a 907C-T transition in exon 9 of the POMT1 gene, resulting in a gln303-to-ter (Q303X) substitution. Both families were consanguineous. In 1 family, 3 sibs had WWS: a girl who died at age 3 years and 2 fetuses. The deceased girl had cobblestone lissencephaly, microphthalmia, buphthalmos, megalocornea, glaucoma, and retinal dysplasia. Serum creatine kinase was increased. One fetus had an encephalocele. In the second family, there was 1 affected girl who died at age 2 months. She presented with severe hydrocephalic ventricular dilatation, hypoplasia of vermis and cerebellum, cyst formation in the posterior fossa, and a Dandy-Walker-like malformation. Eye malformations included bilateral buphthalmos, bilateral glaucoma, and hypertelorism. Serum CK levels were significantly increased.


.0003 MUSCULAR DYSTROPHY-DYSTROGLYCANOPATHY (CONGENITAL WITH EYE AND BRAIN ANOMALIES), TYPE A, 1

POMT1, 1-BP INS, 2110G
   RCV000003396

In a nonconsanguineous Italian family with Walker-Warburg syndrome (MDDGA1; 236670), Beltran-Valero de Bernabe et al. (2002) identified homozygosity for a frameshift mutation, 2110insG, in exon 20 of the POMT1 gene, which was predicted to cause a replacement of 44 highly conserved C-terminal amino acids by 26 irrelevant ones following val703.

Messina et al. (2008) and Mercuri et al. (2009) referred to this mutation as 2111insG, resulting in a frameshift (Ala704GlyfsTer27).


.0004 MUSCULAR DYSTROPHY-DYSTROGLYCANOPATHY (CONGENITAL WITH EYE AND BRAIN ANOMALIES), TYPE A, 1

POMT1, 3-BP DEL, 1260CCT
  
RCV000003397

In a Japanese boy with Walker-Warburg syndrome (MDDGA1; 236670), Kim et al. (2004) identified a homozygous 3-bp deletion (1260delCCT) in the POMT1 gene, resulting in the deletion of a highly conserved leucine at codon 421. The mutation was not identified in 100 Japanese controls. Prenatal studies showed a meningoencephalocele. At birth, the boy showed hypotonia, hydrocephalus, mild microphthalmia, and corneal clouding. Serum creatine kinase levels were markedly elevated to 600 to 31,000 IU/L. He had markedly delayed milestones, with inability to control his head, roll over, or sit. Brain MRI showed agyric frontal and temporo-occipital lobes mixed with pachygyric parietal cortex, as well as hypoplasia of the brainstem and cerebellum. Muscle biopsy showed marked increase in fatty tissue with evidence of necrosis and regeneration, hypoglycosylation of alpha-dystroglycan (DAG1; 128239), and defective laminin binding. Kim et al. (2004) noted that the patient showed exceptionally long survival for WWS, up to 3.5 years, and thus could be considered to have an intermediate phenotype between WWS and muscle-eye-brain disease; however, the presence of a meningoencephalocele was more consistent with WWS.


.0005 MUSCULAR DYSTROPHY-DYSTROGLYCANOPATHY (LIMB-GIRDLE), TYPE C, 1

POMT1, ALA200PRO
  
RCV000003399...

In 5 unrelated Turkish patients with limb-girdle muscular dystrophy and mental retardation (MDDGC1; 609308), some of whom were described by Dincer et al. (2003), Balci et al. (2005) identified a homozygous 598G-C transversion in exon 7 of the POMT1 gene, resulting in an ala200-to-pro (A200P) substitution in a highly conserved residue in loop 4 of a cytoplasmic domain of the protein. All patients were born of consanguineous parents. The mutation was not identified in 212 control chromosomes. Balci et al. (2005) noted that A200P was the first reported POMT1 mutation within the cytoplasmic domain and that the phenotype associated with this mutation is significantly milder than Walker-Warburg syndrome (MDDGA1; 236670), which is caused by other POMT1 mutations (see, e.g., 607423.0001). Most significantly, none of the patients with the A200P mutation had structural brain abnormalities on imaging that would signify a cortical migration defect. Haplotype analysis indicated that A200P is a common founder mutation.


.0006 MUSCULAR DYSTROPHY-DYSTROGLYCANOPATHY (CONGENITAL WITH IMPAIRED INTELLECTUAL DEVELOPMENT), TYPE B, 1

POMT1, GLY65ARG
  
RCV002286389...

In 2 Italian sibs with congenital muscular dystrophy plus impaired intellectual development (MDDGB1; 613155), originally reported by Villanova et al. (2000), van Reeuwijk et al. (2006) identified compound heterozygosity for 2 mutations in the POMT1 gene: a 193G-A transition, resulting in a gly65-to-arg (G65R) substitution, and a 1746G-C transversion, resulting in a trp582-to-cys (W582C; 607423.0007) substitution. The G65R substitution occurs within the protein mannosyltransferase (PMT) domain but is not highly conserved, whereas the W582C substitution affects a highly conserved residue in the endoplasmic reticulum domain. Van Reeuwijk et al. (2006) suggested that the relatively milder phenotype observed in these patients, compared to those with Walker-Warburg syndrome (MDDGA1; 236670) was due to some residual POMT1 activity.

Mercuri et al. (2009) identified a homozygous G65R mutation in an Italian patient with POMT1-related muscular dystrophy, microcephaly, and mental retardation. Brain MRI was normal. The G65R mutation was found in compound heterozygosity with another POMT1 mutation in 4 additional patients with a similar phenotype, although some had cerebellar hypoplasia.


.0007 MUSCULAR DYSTROPHY-DYSTROGLYCANOPATHY (CONGENITAL WITH IMPAIRED INTELLECTUAL DEVELOPMENT), TYPE B, 1

POMT1, TRP582CYS
  
RCV002286388...

For discussion of the trp582-to-cys (W582C) mutation in the POMT1 gene that was found in compound heterozygous state in patients with congenital muscular dystrophy plus impaired intellectual development (MDDGB1; 613155) by van Reeuwijk et al. (2006), see 607423.0006.


.0008 MUSCULAR DYSTROPHY-DYSTROGLYCANOPATHY (CONGENITAL WITH IMPAIRED INTELLECTUAL DEVELOPMENT), TYPE B, 1

POMT1, ARG514TER
  
RCV000760355...

In an Italian patient with congenital muscular dystrophy plus impaired intellectual development (MDDGB1; 613155), originally reported by Villanova et al. (2000), van Reeuwijk et al. (2006) identified compound heterozygosity for 2 mutations in the POMT1 gene: a 1540C-T transition, resulting in an arg514-to-ter (R514X) substitution in the 3-prime MIR region, and a 1770G-C transversion, resulting in gln590-to-his (Q590H; 607423.0009) substitution in a highly conserved residue. Van Reeuwijk et al. (2006) suggested that the relatively milder phenotype, compared to those with Walker-Warburg syndrome (MDDGA1; 236670), observed in this patient was due to some residual POMT1 activity.


.0009 MUSCULAR DYSTROPHY-DYSTROGLYCANOPATHY (CONGENITAL WITH IMPAIRED INTELLECTUAL DEVELOPMENT), TYPE B, 1

POMT1, GLN590HIS
  
RCV000175324...

For discussion of the gln590-to-his (Q590H) mutation in the POMT1 gene that was found in compound heterozygous state in a patient with congenital muscular dystrophy plus impaired intellectual development (MDDGB1; 613155) by van Reeuwijk et al. (2006), see 607423.0008.


.0010 MUSCULAR DYSTROPHY-DYSTROGLYCANOPATHY (CONGENITAL WITH IMPAIRED INTELLECTUAL DEVELOPMENT), TYPE B, 1

POMT1, GLY65ARG
   RCV002286389...

In 2 unrelated children with a severe form of muscular dystrophy (MDDGB1; 613155), D'Amico et al. (2006) identified compound heterozygosity for 2 mutations in the POMT1 gene. Both children had a gly64-to-arg (G65R) substitution in a moderately conserved residue, as well as another pathogenic POMT1 mutation, R541X (607423.0011) and Q590H (607423.0012), respectively.


.0011 MUSCULAR DYSTROPHY-DYSTROGLYCANOPATHY (CONGENITAL WITH IMPAIRED INTELLECTUAL DEVELOPMENT), TYPE B, 1

POMT1, ARG541TER
  
RCV000760355...

For discussion of the arg541-to-ter (R541X) mutation in the POMT1 gene that was found in compound heterozygous state in patients with a severe form of muscular dystrophy (MDDGB1; 613155) by D'Amico et al. (2006), see 607423.0010.


.0012 MUSCULAR DYSTROPHY-DYSTROGLYCANOPATHY (CONGENITAL WITH IMPAIRED INTELLECTUAL DEVELOPMENT), TYPE B, 1

POMT1, GLN590HIS
   RCV000175324...

For discussion of the gln590-to-his (Q590H) mutation in the POMT1 gene that was found in compound heterozygous state in patients with a severe form of muscular dystrophy (MDDGB1; 613155) by D'Amico et al. (2006), see 607423.0010.


.0013 MUSCULAR DYSTROPHY-DYSTROGLYCANOPATHY (CONGENITAL WITH IMPAIRED INTELLECTUAL DEVELOPMENT), TYPE B, 1

POMT1, ALA669THR
  
RCV000414180...

In a patient with a severe form of muscular dystrophy (MDDGB1; 613155), D'Amico et al. (2006) identified compound heterozygosity for an ala669-to-thr (A669T) substitution in a transmembrane domain and a splice site mutation (607423.0014) in the POMT1 gene. Bello et al. (2012) reported that this patient developed cardiomyopathy with moderate left ventricular dysfunction at age 17 years.


.0014 MUSCULAR DYSTROPHY-DYSTROGLYCANOPATHY (CONGENITAL WITH IMPAIRED INTELLECTUAL DEVELOPMENT), TYPE B, 1

POMT1, IVS12DS, G-A, +1
  
RCV001383583...

For discussion of the splice site mutation in the POMT1 gene that was found in compound heterozygous state in a patient with a severe form of muscular dystrophy (MDDGB1; 613155) by D'Amico et al. (2006), see 607423.0013.


.0015 MUSCULAR DYSTROPHY-DYSTROGLYCANOPATHY (CONGENITAL WITH EYE AND BRAIN ANOMALIES), TYPE A, 1

POMT1, 2-BP DEL, 2179TC
  
RCV000003408...

In a patient with muscle-eye-brain disease (MDDGA1; 236670), Godfrey et al. (2007) identified a homozygous 2-bp deletion in the POMT1 gene (2179delTC), predicted to result in a frameshift. Although clinical details were limited, the patient had prenatal onset, increased serum creatine kinase, contractures, congenital glaucoma, microcephaly, and low IQ. Brain MRI showed hydrocephalus, brainstem involvement, white matter abnormalities, cerebellar hypoplasia, and cerebellar cysts.


.0016 MOVED TO 607423.0003


.0017 MUSCULAR DYSTROPHY-DYSTROGLYCANOPATHY (CONGENITAL WITH EYE AND BRAIN ANOMALIES), TYPE A, 1

POMT1, 3-BP DEL, 418ATG
  
RCV000003410

In an Italian patient with muscle-eye-brain disease (MDDGA1; 236670), Mercuri et al. (2009) identified compound heterozygosity for 2 mutations in the POMT1 gene: a 3-bp deletion (418delATG) and a 1-bp duplication (2167dupG; 607423.0018). The mutations were predicted to result in a deletion of met140 and a frameshift, respectively. Although clinical details were limited, the patient had microcephaly, mental retardation, myopia, and seizures, achieved sitting only, and had significantly increased serum creatine kinase with decreased alpha-dystroglycan staining on muscle biopsy.


.0018 MUSCULAR DYSTROPHY-DYSTROGLYCANOPATHY (CONGENITAL WITH EYE AND BRAIN ANOMALIES), TYPE A, 1

POMT1, 1-BP DUP, 2167G
  
RCV000003411...

For discussion of the 1-bp duplication in the POMT1 gene (2167dupG) that was found in compound heterozygous state in a patient with muscle-eye-brain disease (MDDGA1; 236670) by Mercuri et al. (2009), see 607423.0017.


.0019 MUSCULAR DYSTROPHY-DYSTROGLYCANOPATHY (LIMB-GIRDLE), TYPE C, 1

POMT1, ASN144ASP
  
RCV000032629

In a 20-year-old man with limb-girdle muscular dystrophy (MDDGC1; 609308), Bello et al. (2012) identified compound heterozygosity for 2 mutations in the POMT1 gene: a 430A-G transition resulting in an asn144-to-asp (N144D) substitution at a conserved residue in a transmembrane helix, and a 1241C-T transition resulting in a thr414-to-met (T414M; 607423.0020) substitution at a conserved residue in an MIR domain. Neither mutation was found in 110 control chromosomes. Both mutations were predicted to be destabilizing or pathogenic. The patient had normal psychomotor development, mild cognitive impairment, and proximal muscle weakness, and developed cardiomyopathy at age 12 years.


.0020 MUSCULAR DYSTROPHY-DYSTROGLYCANOPATHY (LIMB-GIRDLE), TYPE C, 1

POMT1, THR414MET
  
RCV000032630

For discussion of the thr414-to-met (T414M) mutation in the POMT1 gene that was found in compound heterozygous state in a patient with limb-girdle muscular dystrophy (MDDGC1; 609308) by Bello et al. (2012), see 607423.0019.


REFERENCES

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  14. van Reeuwijk, J., Maugenre, S., van den Elzen, C., Verrips, A., Bertini, E., Muntoni, F., Merlini, L., Scheffer, H., Brunner, H. G., Guicheney, P., van Bokhoven, H. The expanding phenotype of POMT1 mutations: from Walker-Warburg syndrome to congenital muscular dystrophy, microcephaly, and mental retardation. Hum. Mutat. 27: 453-459, 2006. [PubMed: 16575835, related citations] [Full Text]

  15. Villanova, M., Mercuri, E., Bertini, E., Sabatelli, P., Morandi, L., Mora, M., Sewry, C., Brockington, M., Brown, S. C., Ferreiro, A., Maraldi, N. M., Toda, T., Guicheney, P., Merlini, L., Muntoni, F. Congenital muscular dystrophy associated with calf hypertrophy, microcephaly and severe mental retardation in three Italian families: evidence for a novel CMD syndrome. Neuromusc. Disord. 10: 541-547, 2000. [PubMed: 11053679, related citations] [Full Text]

  16. Willer, T., Prados, B., Falcon-Perez, J. M., Renner-Muller, I., Przemeck, G. K. H., Lommel, M., Coloma, A., Valero, M. C., Hrabe de Angelis, M., Tanner, W., Wolf, E., Strahl, S., Cruces, J. Targeted disruption of the Walker-Warburg syndrome gene Pomt1 in mouse results in embryonic lethality. Proc. Nat. Acad. Sci. 101: 14126-14131, 2004. Note: Erratum: Proc. Nat. Acad. Sci. 101: 16081 only, 2004. [PubMed: 15383666, images, related citations] [Full Text]


Cassandra L. Kniffin - updated : 2/4/2013
Cassandra L. Kniffin - updated : 11/8/2010
Cassandra L. Kniffin - updated : 11/1/2007
Cassandra L. Kniffin - updated : 9/17/2007
Cassandra L. Kniffin - updated : 5/18/2006
Cassandra L. Kniffin - updated : 4/13/2005
Victor A. McKusick - updated : 12/2/2004
Cassandra L. Kniffin - updated : 8/27/2004
Victor A. McKusick - updated : 12/23/2002
Creation Date:
Patricia A. Hartz : 12/13/2002
carol : 08/19/2020
carol : 10/09/2019
carol : 09/25/2018
joanna : 06/29/2016
alopez : 4/30/2015
mcolton : 4/17/2015
carol : 10/24/2014
carol : 10/20/2014
mcolton : 10/16/2014
carol : 10/15/2014
carol : 8/5/2013
carol : 7/12/2013
carol : 2/7/2013
ckniffin : 2/4/2013
terry : 9/28/2011
ckniffin : 11/17/2010
carol : 11/10/2010
ckniffin : 11/8/2010
ckniffin : 12/4/2009
wwang : 11/26/2007
wwang : 11/5/2007
ckniffin : 11/1/2007
wwang : 9/24/2007
ckniffin : 9/17/2007
wwang : 5/24/2006
ckniffin : 5/18/2006
tkritzer : 4/14/2005
ckniffin : 4/13/2005
carol : 12/21/2004
carol : 12/14/2004
tkritzer : 12/10/2004
terry : 12/2/2004
tkritzer : 9/7/2004
ckniffin : 8/27/2004
carol : 12/23/2002
terry : 12/23/2002
mgross : 12/17/2002
mgross : 12/13/2002

* 607423

PROTEIN O-MANNOSYLTRANSFERASE 1; POMT1


Alternative titles; symbols

ROTATED ABDOMEN, DROSOPHILA, HOMOLOG OF; RT


HGNC Approved Gene Symbol: POMT1

SNOMEDCT: 720523006;  


Cytogenetic location: 9q34.13   Genomic coordinates (GRCh38) : 9:131,502,918-131,523,799 (from NCBI)


Gene-Phenotype Relationships

Location Phenotype Phenotype
MIM number
Inheritance Phenotype
mapping key
9q34.13 Muscular dystrophy-dystroglycanopathy (congenital with brain and eye anomalies), type A, 1 236670 Autosomal recessive 3
Muscular dystrophy-dystroglycanopathy (congenital with impaired intellectual development), type B, 1 613155 Autosomal recessive 3
Muscular dystrophy-dystroglycanopathy (limb-girdle), type C, 1 609308 Autosomal recessive 3

TEXT

Description

The POMT1 gene encodes protein O-mannosyltransferase, an enzyme that catalyzes O-mannosylation of proteins, an important protein modification in eukaryotes that is initiated by an evolutionarily conserved family of O-mannosyltransferases. POMT1 shares sequence similarity with protein O-mannosyltransferases of S. cerevisiae. In yeast, these enzymes are located in the endoplasmic reticulum (ER) and are required for cell integrity and cell wall rigidity. POMT1 also shows similarity to the Drosophila 'rotated abdomen' (rt) gene, which, when mutated, causes defects in myogenesis and muscle structure (Jurado et al., 1999).


Cloning and Expression

Using homology with Drosophila rt, Jurado et al. (1999) identified an EST for POMT1. By 5-prime cDNA walking performed by vector/insert PCR, and by anchor PCR of fetal brain RNA, they cloned the full-length POMT1 cDNA. The deduced 725-amino acid protein has a calculated molecular mass of about 82.5 kD. POMT1 contains 7 to 12 putative transmembrane regions and a C-terminal ER membrane retention signal. POMT1 shares 40% identity with rt, and it averages 54% similarity with the yeast Pmts. Northern blot analysis revealed a diffuse band of 3.1 to 3.2 kb in all tissues tested, with slightly stronger expression in skeletal muscle and heart. RNA dot blot analysis revealed ubiquitous expression, with maximum levels in testis and high levels in fetal brain and pituitary. By this method, expression in skeletal muscle and heart was not significantly higher than expression in other tissues. RT-PCR revealed several mRNA splice variants. Southern blot analysis indicated Pomt1 expression in all mammalian DNAs tested, as well as weak but specific signals in bird, reptile, and amphibian DNAs; no signal was detected in fish or plant DNAs.


Gene Structure

Jurado et al. (1999) determined that the POMT1 gene contains 20 exons and spans about 20 kb. The initiator ATG is located in exon 2. There are a variable number of 17- to 19-nucleotide tandem repeats within intron 13. Jurado et al. (1999) identified 8 different allelic variants carrying 36 to 56 repeats within normal chromosomes. The 56-repeat allele was the most frequent. Intron 2 also contains a (CA)n microsatellite.


Mapping

By somatic cell hybrid analysis, radiation hybrid analysis, and linkage analysis, Jurado et al. (1999) mapped the POMT1 gene to chromosome 9q34.1. The POMT1 locus is flanked by markers D9S260 and D9S7293 on 9q34 (Beltran-Valero de Bernabe et al., 2002).


Molecular Genetics

Mutation in the POMT1 gene can cause 3 different forms of muscular dystrophy-dystroglycanopathy (MDDG): a severe congenital form with brain and eye anomalies (type A1; MDDGA1, 236670), formerly designated Walker-Warburg syndrome (WWS) or muscle-eye-brain disease (MEB); a less severe congenital form with impaired intellectual development (type B1; MDDGB1; 613115); and a milder limb-girdle form (type C1; MDDGC1; 609308), previously designated LGMD2K (LGMDR11).

Beltran-Valero de Bernabe et al. (2002) identified several families in which Walker-Warburg syndrome (MDDGA1; 236670), a severe recessive congenital muscular dystrophy associated with defects in neuronal migration that produce complex brain and eye abnormalities, was caused by mutation in the POMT1 gene (see 607423.0001-607423.0003).

In a Japanese boy with Walker-Warburg syndrome, Kim et al. (2004) identified a homozygous 3-bp deletion in the POMT1 gene (607423.0004).

In 5 unrelated Turkish patients with autosomal recessive limb-girdle muscular dystrophy and mental retardation, but without structural brain abnormalities (MDDGC1; 609308), Balci et al. (2005) identified a homozygous founder mutation in the POMT1 gene (607423.0005).

Van Reeuwijk et al. (2006) identified compound heterozygous mutations in the POMT1 gene (see, e.g., 607423.0006-607423.0009) in 5 patients from 4 unrelated families with a milder form of WWS, referred to as 'congenital muscular dystrophy plus impaired intellectual development' (MDDGB1; 613155). Van Reeuwijk et al. (2006) also identified 7 novel mutations in the POMT1 gene in 7 unrelated patients with classic WWS.

In 3 unrelated patients with a severe form of congenital muscular dystrophy, D'Amico et al. (2006) identified compound heterozygous mutations in the POMT1 gene (607423.0010-607423.0014). None had structural brain abnormalities.

Bouchet et al. (2007) identified mutations in the POMT1 gene in 13 (32%) of 41 families in which at least 1 fetus had severe cobblestone cortex (type II lissencephaly), as observed in patients with WWS. The minimum diagnostic criteria included hydrocephalus, agyria, thickened leptomeninges filled with neuroglial ectopia, disorganized cortical ribbon, and cerebellar dysplasia. Mutations in the POMGNT1 (606822) and POMT2 (607439) genes were identified in 6 (15%) and 3 (7%) families, respectively. Overall, mutations were identified in 22 of 41 families included in the study. Definitive pathogenic mutations were not identified in the FKRP (606596), FKTN (607440), or LARGE (603590) genes.

Godfrey et al. (2007) identified POMT1 mutations in 8 of 92 patients with evidence of a muscular dystrophy due to defective glycosylation of alpha-dystroglycan (DAG1; 128239). One patient had WWS, 1 had MEB (607423.0015), 3 had congenital muscular dystrophy, and 3 had limb-girdle muscular dystrophy. All had low IQ and about half had structural brain abnormalities.

Mercuri et al. (2009) identified POMT1 mutations in 17 (21%) of 81 Italian patients with a dystroglycanopathy. Thirteen patients had muscular dystrophy, 2 had MEB, and 2 had WWS. Six patients had a normal MRI, 1 of whom had a severe dilated cardiomyopathy. All but 1 had mental retardation and microcephaly. No clear-cut genotype-phenotype correlations were observed; however, the more severe phenotypes appeared to be associated with mutations predicted to result in severe disruption of the gene.


Animal Model

Willer et al. (2004) found that during embryogenesis, the mouse Pomt1 gene is prominently expressed in the neural tube, the developing eye, and the mesenchyme. They noted that these sites of expression correlate with those in which the main tissue alterations are observed in patients with Walker-Warburg syndrome. Willer et al. (2004) inactivated a Pomt1 allele by gene targeting in mouse embryonic stem cells and produced chimeras transmitting the defect allele to offspring. Although heterozygous mice were viable and fertile, the total absence of homozygous Pomt1 -/- pups among the progeny of heterozygous intercrosses indicated that this genotype is embryonic lethal. Analysis of the mutant phenotype revealed that homozygous null mice suffered developmental arrest around embryonic day (E) 7.5 and died between E7.5 and E9.5. The Pomt1 -/- embryos presented defects in the formation of the Reichert membrane, the first basement membrane to form in the embryo. The Reichert membrane is a thick multilayered membrane between the parietal endoderm cells and the trophoblast cells of rodents; it is thought to function to allow free access of nutrients to the embryo while excluding maternal cells (Salamat et al., 1995). The failure of this membrane to form in the Pomt1 -/- embryos appeared to be the result of abnormal glycosylation and maturation of dystroglycan that may impair recruitment of laminin (see 150320), a structural component required for the formation of Reichert membrane in rodents. Willer et al. (2004) concluded that the targeted disruption of Pomt1 in mouse represents an example of an engineered deletion of a known glycosyltransferase involved in O-mannosyl glycan synthesis.


ALLELIC VARIANTS 20 Selected Examples):

.0001   MUSCULAR DYSTROPHY-DYSTROGLYCANOPATHY (CONGENITAL WITH EYE AND BRAIN ANOMALIES), TYPE A, 1

POMT1, GLY76ARG
SNP: rs28941782, ClinVar: RCV000003394, RCV001171882, RCV005055501

In a family with Walker-Warburg syndrome (MDDGA1; 236670), previously reported by Cormand et al. (2001), Beltran-Valero de Bernabe et al. (2002) identified a homozygous transition, 226G-A, in exon 3 of the POMT1 gene, predicting a gly76-to-arg (G76R) substitution. The parents were first cousins of Turkish origin. After 3 spontaneous abortions, a male was born presenting with severe hydrocephalus with dilatation of the third and fourth ventricles and minimal cortical development, no visible gyri, bifid cerebellum, and hypoplasia of the vermis and of the cerebellar hemispheres. A cerebellar cyst was observed. The corpus callosum appeared to be present. Microphthalmia on the left and exophthalmia on the right were noted. The genitalia were hypoplastic. Serum creatine kinase levels were highly elevated at more than 2,000 U/l. The patient died at age 7 months. Another affected child, whose DNA was used for genetic analysis, died 15 minutes after birth. She presented with severe hydrocephaly, encephalocele, and bilateral cleft lip.


.0002   MUSCULAR DYSTROPHY-DYSTROGLYCANOPATHY (CONGENITAL WITH EYE AND BRAIN ANOMALIES), TYPE A, 1

POMT1, GLN303TER
SNP: rs119462981, gnomAD: rs119462981, ClinVar: RCV000003395, RCV001813941, RCV003231073, RCV003764521

In affected members of 2 families of Turkish origin with Walker-Warburg syndrome (MDDGA1; 236670), previously reported by Cormand et al. (2001), Beltran-Valero de Bernabe et al. (2002) identified homozygosity for a 907C-T transition in exon 9 of the POMT1 gene, resulting in a gln303-to-ter (Q303X) substitution. Both families were consanguineous. In 1 family, 3 sibs had WWS: a girl who died at age 3 years and 2 fetuses. The deceased girl had cobblestone lissencephaly, microphthalmia, buphthalmos, megalocornea, glaucoma, and retinal dysplasia. Serum creatine kinase was increased. One fetus had an encephalocele. In the second family, there was 1 affected girl who died at age 2 months. She presented with severe hydrocephalic ventricular dilatation, hypoplasia of vermis and cerebellum, cyst formation in the posterior fossa, and a Dandy-Walker-like malformation. Eye malformations included bilateral buphthalmos, bilateral glaucoma, and hypertelorism. Serum CK levels were significantly increased.


.0003   MUSCULAR DYSTROPHY-DYSTROGLYCANOPATHY (CONGENITAL WITH EYE AND BRAIN ANOMALIES), TYPE A, 1

POMT1, 1-BP INS, 2110G
ClinVar: RCV000003396

In a nonconsanguineous Italian family with Walker-Warburg syndrome (MDDGA1; 236670), Beltran-Valero de Bernabe et al. (2002) identified homozygosity for a frameshift mutation, 2110insG, in exon 20 of the POMT1 gene, which was predicted to cause a replacement of 44 highly conserved C-terminal amino acids by 26 irrelevant ones following val703.

Messina et al. (2008) and Mercuri et al. (2009) referred to this mutation as 2111insG, resulting in a frameshift (Ala704GlyfsTer27).


.0004   MUSCULAR DYSTROPHY-DYSTROGLYCANOPATHY (CONGENITAL WITH EYE AND BRAIN ANOMALIES), TYPE A, 1

POMT1, 3-BP DEL, 1260CCT
SNP: rs587777818, ClinVar: RCV000003397

In a Japanese boy with Walker-Warburg syndrome (MDDGA1; 236670), Kim et al. (2004) identified a homozygous 3-bp deletion (1260delCCT) in the POMT1 gene, resulting in the deletion of a highly conserved leucine at codon 421. The mutation was not identified in 100 Japanese controls. Prenatal studies showed a meningoencephalocele. At birth, the boy showed hypotonia, hydrocephalus, mild microphthalmia, and corneal clouding. Serum creatine kinase levels were markedly elevated to 600 to 31,000 IU/L. He had markedly delayed milestones, with inability to control his head, roll over, or sit. Brain MRI showed agyric frontal and temporo-occipital lobes mixed with pachygyric parietal cortex, as well as hypoplasia of the brainstem and cerebellum. Muscle biopsy showed marked increase in fatty tissue with evidence of necrosis and regeneration, hypoglycosylation of alpha-dystroglycan (DAG1; 128239), and defective laminin binding. Kim et al. (2004) noted that the patient showed exceptionally long survival for WWS, up to 3.5 years, and thus could be considered to have an intermediate phenotype between WWS and muscle-eye-brain disease; however, the presence of a meningoencephalocele was more consistent with WWS.


.0005   MUSCULAR DYSTROPHY-DYSTROGLYCANOPATHY (LIMB-GIRDLE), TYPE C, 1

POMT1, ALA200PRO
SNP: rs119462982, gnomAD: rs119462982, ClinVar: RCV000003399, RCV000179928, RCV001264826, RCV001385876, RCV001813942, RCV003234890, RCV003472966

In 5 unrelated Turkish patients with limb-girdle muscular dystrophy and mental retardation (MDDGC1; 609308), some of whom were described by Dincer et al. (2003), Balci et al. (2005) identified a homozygous 598G-C transversion in exon 7 of the POMT1 gene, resulting in an ala200-to-pro (A200P) substitution in a highly conserved residue in loop 4 of a cytoplasmic domain of the protein. All patients were born of consanguineous parents. The mutation was not identified in 212 control chromosomes. Balci et al. (2005) noted that A200P was the first reported POMT1 mutation within the cytoplasmic domain and that the phenotype associated with this mutation is significantly milder than Walker-Warburg syndrome (MDDGA1; 236670), which is caused by other POMT1 mutations (see, e.g., 607423.0001). Most significantly, none of the patients with the A200P mutation had structural brain abnormalities on imaging that would signify a cortical migration defect. Haplotype analysis indicated that A200P is a common founder mutation.


.0006   MUSCULAR DYSTROPHY-DYSTROGLYCANOPATHY (CONGENITAL WITH IMPAIRED INTELLECTUAL DEVELOPMENT), TYPE B, 1

POMT1, GLY65ARG
SNP: rs119462983, gnomAD: rs119462983, ClinVar: RCV002286389, RCV002512705, RCV003460408

In 2 Italian sibs with congenital muscular dystrophy plus impaired intellectual development (MDDGB1; 613155), originally reported by Villanova et al. (2000), van Reeuwijk et al. (2006) identified compound heterozygosity for 2 mutations in the POMT1 gene: a 193G-A transition, resulting in a gly65-to-arg (G65R) substitution, and a 1746G-C transversion, resulting in a trp582-to-cys (W582C; 607423.0007) substitution. The G65R substitution occurs within the protein mannosyltransferase (PMT) domain but is not highly conserved, whereas the W582C substitution affects a highly conserved residue in the endoplasmic reticulum domain. Van Reeuwijk et al. (2006) suggested that the relatively milder phenotype observed in these patients, compared to those with Walker-Warburg syndrome (MDDGA1; 236670) was due to some residual POMT1 activity.

Mercuri et al. (2009) identified a homozygous G65R mutation in an Italian patient with POMT1-related muscular dystrophy, microcephaly, and mental retardation. Brain MRI was normal. The G65R mutation was found in compound heterozygosity with another POMT1 mutation in 4 additional patients with a similar phenotype, although some had cerebellar hypoplasia.


.0007   MUSCULAR DYSTROPHY-DYSTROGLYCANOPATHY (CONGENITAL WITH IMPAIRED INTELLECTUAL DEVELOPMENT), TYPE B, 1

POMT1, TRP582CYS
SNP: rs119462984, ClinVar: RCV002286388, RCV002512704

For discussion of the trp582-to-cys (W582C) mutation in the POMT1 gene that was found in compound heterozygous state in patients with congenital muscular dystrophy plus impaired intellectual development (MDDGB1; 613155) by van Reeuwijk et al. (2006), see 607423.0006.


.0008   MUSCULAR DYSTROPHY-DYSTROGLYCANOPATHY (CONGENITAL WITH IMPAIRED INTELLECTUAL DEVELOPMENT), TYPE B, 1

POMT1, ARG514TER
SNP: rs119462985, gnomAD: rs119462985, ClinVar: RCV000760355, RCV001851614, RCV002286390, RCV005041976

In an Italian patient with congenital muscular dystrophy plus impaired intellectual development (MDDGB1; 613155), originally reported by Villanova et al. (2000), van Reeuwijk et al. (2006) identified compound heterozygosity for 2 mutations in the POMT1 gene: a 1540C-T transition, resulting in an arg514-to-ter (R514X) substitution in the 3-prime MIR region, and a 1770G-C transversion, resulting in gln590-to-his (Q590H; 607423.0009) substitution in a highly conserved residue. Van Reeuwijk et al. (2006) suggested that the relatively milder phenotype, compared to those with Walker-Warburg syndrome (MDDGA1; 236670), observed in this patient was due to some residual POMT1 activity.


.0009   MUSCULAR DYSTROPHY-DYSTROGLYCANOPATHY (CONGENITAL WITH IMPAIRED INTELLECTUAL DEVELOPMENT), TYPE B, 1

POMT1, GLN590HIS
SNP: rs119462986, gnomAD: rs119462986, ClinVar: RCV000175324, RCV002286391, RCV003323349, RCV003764522

For discussion of the gln590-to-his (Q590H) mutation in the POMT1 gene that was found in compound heterozygous state in a patient with congenital muscular dystrophy plus impaired intellectual development (MDDGB1; 613155) by van Reeuwijk et al. (2006), see 607423.0008.


.0010   MUSCULAR DYSTROPHY-DYSTROGLYCANOPATHY (CONGENITAL WITH IMPAIRED INTELLECTUAL DEVELOPMENT), TYPE B, 1

POMT1, GLY65ARG
ClinVar: RCV002286389, RCV002512705, RCV003460408

In 2 unrelated children with a severe form of muscular dystrophy (MDDGB1; 613155), D'Amico et al. (2006) identified compound heterozygosity for 2 mutations in the POMT1 gene. Both children had a gly64-to-arg (G65R) substitution in a moderately conserved residue, as well as another pathogenic POMT1 mutation, R541X (607423.0011) and Q590H (607423.0012), respectively.


.0011   MUSCULAR DYSTROPHY-DYSTROGLYCANOPATHY (CONGENITAL WITH IMPAIRED INTELLECTUAL DEVELOPMENT), TYPE B, 1

POMT1, ARG541TER
SNP: rs119462985, gnomAD: rs119462985, ClinVar: RCV000760355, RCV001851614, RCV002286390, RCV005041976

For discussion of the arg541-to-ter (R541X) mutation in the POMT1 gene that was found in compound heterozygous state in patients with a severe form of muscular dystrophy (MDDGB1; 613155) by D'Amico et al. (2006), see 607423.0010.


.0012   MUSCULAR DYSTROPHY-DYSTROGLYCANOPATHY (CONGENITAL WITH IMPAIRED INTELLECTUAL DEVELOPMENT), TYPE B, 1

POMT1, GLN590HIS
ClinVar: RCV000175324, RCV002286391, RCV003323349, RCV003764522

For discussion of the gln590-to-his (Q590H) mutation in the POMT1 gene that was found in compound heterozygous state in patients with a severe form of muscular dystrophy (MDDGB1; 613155) by D'Amico et al. (2006), see 607423.0010.


.0013   MUSCULAR DYSTROPHY-DYSTROGLYCANOPATHY (CONGENITAL WITH IMPAIRED INTELLECTUAL DEVELOPMENT), TYPE B, 1

POMT1, ALA669THR
SNP: rs119462987, gnomAD: rs119462987, ClinVar: RCV000414180, RCV000694423, RCV002286394, RCV003460409

In a patient with a severe form of muscular dystrophy (MDDGB1; 613155), D'Amico et al. (2006) identified compound heterozygosity for an ala669-to-thr (A669T) substitution in a transmembrane domain and a splice site mutation (607423.0014) in the POMT1 gene. Bello et al. (2012) reported that this patient developed cardiomyopathy with moderate left ventricular dysfunction at age 17 years.


.0014   MUSCULAR DYSTROPHY-DYSTROGLYCANOPATHY (CONGENITAL WITH IMPAIRED INTELLECTUAL DEVELOPMENT), TYPE B, 1

POMT1, IVS12DS, G-A, +1
SNP: rs1051679985, gnomAD: rs1051679985, ClinVar: RCV001383583, RCV002286395, RCV003472967, RCV005055502

For discussion of the splice site mutation in the POMT1 gene that was found in compound heterozygous state in a patient with a severe form of muscular dystrophy (MDDGB1; 613155) by D'Amico et al. (2006), see 607423.0013.


.0015   MUSCULAR DYSTROPHY-DYSTROGLYCANOPATHY (CONGENITAL WITH EYE AND BRAIN ANOMALIES), TYPE A, 1

POMT1, 2-BP DEL, 2179TC
SNP: rs587777819, ClinVar: RCV000003408, RCV000150016, RCV000587199, RCV005041977

In a patient with muscle-eye-brain disease (MDDGA1; 236670), Godfrey et al. (2007) identified a homozygous 2-bp deletion in the POMT1 gene (2179delTC), predicted to result in a frameshift. Although clinical details were limited, the patient had prenatal onset, increased serum creatine kinase, contractures, congenital glaucoma, microcephaly, and low IQ. Brain MRI showed hydrocephalus, brainstem involvement, white matter abnormalities, cerebellar hypoplasia, and cerebellar cysts.


.0016   MOVED TO 607423.0003


.0017   MUSCULAR DYSTROPHY-DYSTROGLYCANOPATHY (CONGENITAL WITH EYE AND BRAIN ANOMALIES), TYPE A, 1

POMT1, 3-BP DEL, 418ATG
SNP: rs587777820, ClinVar: RCV000003410

In an Italian patient with muscle-eye-brain disease (MDDGA1; 236670), Mercuri et al. (2009) identified compound heterozygosity for 2 mutations in the POMT1 gene: a 3-bp deletion (418delATG) and a 1-bp duplication (2167dupG; 607423.0018). The mutations were predicted to result in a deletion of met140 and a frameshift, respectively. Although clinical details were limited, the patient had microcephaly, mental retardation, myopia, and seizures, achieved sitting only, and had significantly increased serum creatine kinase with decreased alpha-dystroglycan staining on muscle biopsy.


.0018   MUSCULAR DYSTROPHY-DYSTROGLYCANOPATHY (CONGENITAL WITH EYE AND BRAIN ANOMALIES), TYPE A, 1

POMT1, 1-BP DUP, 2167G
SNP: rs398124245, ClinVar: RCV000003411, RCV000081487, RCV000546035, RCV000778874, RCV001391256, RCV002496244, RCV002512706, RCV003225921, RCV003398430, RCV003447841

For discussion of the 1-bp duplication in the POMT1 gene (2167dupG) that was found in compound heterozygous state in a patient with muscle-eye-brain disease (MDDGA1; 236670) by Mercuri et al. (2009), see 607423.0017.


.0019   MUSCULAR DYSTROPHY-DYSTROGLYCANOPATHY (LIMB-GIRDLE), TYPE C, 1

POMT1, ASN144ASP
SNP: rs397514501, ClinVar: RCV000032629

In a 20-year-old man with limb-girdle muscular dystrophy (MDDGC1; 609308), Bello et al. (2012) identified compound heterozygosity for 2 mutations in the POMT1 gene: a 430A-G transition resulting in an asn144-to-asp (N144D) substitution at a conserved residue in a transmembrane helix, and a 1241C-T transition resulting in a thr414-to-met (T414M; 607423.0020) substitution at a conserved residue in an MIR domain. Neither mutation was found in 110 control chromosomes. Both mutations were predicted to be destabilizing or pathogenic. The patient had normal psychomotor development, mild cognitive impairment, and proximal muscle weakness, and developed cardiomyopathy at age 12 years.


.0020   MUSCULAR DYSTROPHY-DYSTROGLYCANOPATHY (LIMB-GIRDLE), TYPE C, 1

POMT1, THR414MET
SNP: rs397515400, gnomAD: rs397515400, ClinVar: RCV000032630

For discussion of the thr414-to-met (T414M) mutation in the POMT1 gene that was found in compound heterozygous state in a patient with limb-girdle muscular dystrophy (MDDGC1; 609308) by Bello et al. (2012), see 607423.0019.


REFERENCES

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Contributors:
Cassandra L. Kniffin - updated : 2/4/2013
Cassandra L. Kniffin - updated : 11/8/2010
Cassandra L. Kniffin - updated : 11/1/2007
Cassandra L. Kniffin - updated : 9/17/2007
Cassandra L. Kniffin - updated : 5/18/2006
Cassandra L. Kniffin - updated : 4/13/2005
Victor A. McKusick - updated : 12/2/2004
Cassandra L. Kniffin - updated : 8/27/2004
Victor A. McKusick - updated : 12/23/2002

Creation Date:
Patricia A. Hartz : 12/13/2002

Edit History:
carol : 08/19/2020
carol : 10/09/2019
carol : 09/25/2018
joanna : 06/29/2016
alopez : 4/30/2015
mcolton : 4/17/2015
carol : 10/24/2014
carol : 10/20/2014
mcolton : 10/16/2014
carol : 10/15/2014
carol : 8/5/2013
carol : 7/12/2013
carol : 2/7/2013
ckniffin : 2/4/2013
terry : 9/28/2011
ckniffin : 11/17/2010
carol : 11/10/2010
ckniffin : 11/8/2010
ckniffin : 12/4/2009
wwang : 11/26/2007
wwang : 11/5/2007
ckniffin : 11/1/2007
wwang : 9/24/2007
ckniffin : 9/17/2007
wwang : 5/24/2006
ckniffin : 5/18/2006
tkritzer : 4/14/2005
ckniffin : 4/13/2005
carol : 12/21/2004
carol : 12/14/2004
tkritzer : 12/10/2004
terry : 12/2/2004
tkritzer : 9/7/2004
ckniffin : 8/27/2004
carol : 12/23/2002
terry : 12/23/2002
mgross : 12/17/2002
mgross : 12/13/2002