FREM1 Autosomal Recessive Disorders

Li C, Slavotinek A.

Publication Details

Estimated reading time: 18 minutes

Summary

Clinical characteristics.

FREM1 autosomal recessive disorders include Manitoba oculotrichoanal (MOTA) syndrome, bifid nose with or without anorectal and renal anomalies (BNAR syndrome), and isolated congenital anomalies of kidney and urinary tract (CAKUT).

  • MOTA syndrome is characterized by an aberrant hairline (unilateral or bilateral wedge-shaped extension of the anterior hairline from the temple region to the ipsilateral eye) and anomalies of the eyes (widely spaced eyes, anophthalmia/microphthalmia and/or cryptophthalmos, colobomas of the upper eyelid, and corneopalpebral synechiae), nose (bifid or broad nasal tip), abdominal wall (omphalocele or umbilical hernia), and anus (stenosis and/or anterior displacement of the anal opening). The manifestations and degree of severity vary even among affected members of the same family. Growth and psychomotor development are normal.
  • BNAR syndrome is characterized by a bifid or wide nasal tip, anorectal anomalies, and renal malformations (e.g., renal agenesis, renal dysplasia). Typically the eye manifestations of MOTA syndrome are absent.
  • FREM1-CAKUT was identified in one individual with bilateral vesicoureteral reflux (VUR) and a second individual with VUR and renal hypodysplasia.

Diagnosis/testing.

The diagnosis of a FREM1 autosomal recessive disorder is established in a proband by identification of biallelic pathogenic variants in FREM1 on molecular genetic testing.

Management.

Treatment of manifestations:

  • Intensive ocular lubrication to avoid exposure keratopathy before surgery is performed; release of synechiae between the eyelid and cornea; surgical intervention and/or prostheses for anophthalmia/microphthalmia and cryptophthalmos if warranted; supportive care for those with visual impairment
  • Rhinoplasty for notched ala nasi or bifid nose
  • Surgical closure of omphalocele; surgical or conservative management of umbilical hernia
  • Dilation for anal stenosis
  • Supportive treatment to preserve renal functions and electrolyte balance; dialysis and transplant if indicated in individuals with renal failure
  • Psychosocial support

Genetic counseling.

MOTA, BNAR syndrome, and FREM1-CAKUT are inherited in an autosomal recessive manner. At conception, each full sib of an affected individual has a 25% chance of being affected, a 50% chance of being an asymptomatic carrier, and a 25% chance of being unaffected and not a carrier. Once the FREM1 pathogenic variants have been identified in an affected family member, prenatal testing for a pregnancy at increased risk and preimplantation genetic testing are possible.

GeneReview Scope

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Table

Manitoba oculotrichoanal (MOTA) syndrome Bifid nose with or without anorectal and renal anomalies (BNAR syndrome)

Suggestive Findings

A FREM1 autosomal recessive disorder should be suspected in an individual with features of Manitoba oculotrichoanal (MOTA) syndrome, bifid nose with or without anorectal and renal anomalies (BNAR syndrome), and congenital anomalies of kidney and urinary tract (CAKUT).

MOTA syndrome

  • Widely spaced eyes
  • Aberrant anterior hairline extending to the ipsilateral eye (unilateral or bilateral); often wedge-shaped, but may also resemble a thin stripe or appear tongue-shaped
  • Ocular abnormalities including ipsilateral colobomas of the upper eyelid (sometimes referred to as a Tessier number 10 cleft by surgeons), corneopalpebral synechiae (i.e., adhesions between the eyelids and the cornea), and microphthalmia/anophthalmia and/or cryptophthalmos. Corneal clouding was described in one individual. The upper eyelid colobomas and cryptophthalmos are part of a spectrum of anomalies ranging from colobomas of the lid to eyelid coloboma plus corneopalpebral synechiae (also known as abortive cryptophthalmos) to complete cryptophthalmos [Nouby 2002]. Anomalies may be unilateral or bilateral; the severity may differ between the two eyes.
  • Absent or interrupted eyebrow ipsilateral to the eye defect
  • A bifid nose, a notch at the nasal tip, or a broad nose
  • Anal stenosis and/or anteriorly placed anus
  • Omphalocele or umbilical hernia
  • Family history consistent with autosomal recessive inheritance
  • Ethnic origin of aboriginal Oji-Cree

Bifid nose with or without anorectal and renal anomalies (BNAR syndrome)

  • Median nose cleft or notch, or wide bulbous nasal tip
  • Anorectal anomalies (e.g., anal stenosis, anteriorly placed anus)
  • Renal malformations (e.g., renal agenesis, renal dysplasia)
  • Eye manifestations of MOTA syndrome typically absent

FREM1 congenital anomalies of kidney and urinary tract (CAKUT). Renal malformations (e.g., vesicoureteral reflux, renal hypodysplasia) [Kohl et al 2014]

Establishing the Diagnosis

The diagnosis of a FREM1 autosomal recessive disorder is established in a proband by identification of biallelic pathogenic (or likely pathogenic) variants in FREM1 on molecular genetic testing (see Table 1).

Note: (1) Per ACMG/AMP variant interpretation guidelines, the terms "pathogenic variants" and "likely pathogenic variants" are synonymous in a clinical setting, meaning that both are considered diagnostic and both can be used for clinical decision making [Richards et al 2015]. Reference to "pathogenic variants" in this section is understood to include any likely pathogenic variants. (2) Identification of biallelic FREM1 variants of uncertain significance (or of one known FREM1 pathogenic variant and one FREM1 variant of uncertain significance) does not establish or rule out the diagnosis.

Molecular genetic testing approaches can include a combination of gene-targeted testing (single-gene testing, multigene panel) and comprehensive genomic testing (chromosomal microarray analysis, exome sequencing, exome array, genome sequencing) depending on the phenotype.

Gene-targeted testing requires that the clinician determine which gene(s) are likely involved, whereas genomic testing does not. Because the phenotype of FREM1 autosomal recessive disorders is broad, individuals with the distinctive findings described in Suggestive Findings are likely to be diagnosed using gene-targeted testing (see Option 1), whereas those in whom the diagnosis of a FREM1 autosomal recessive disorder has not been considered are more likely to be diagnosed using genomic testing (see Option 2).

Option 1

When the phenotypic and laboratory findings suggest the diagnosis of a FREM1 autosomal recessive disorder, molecular genetic testing approaches can include single-gene testing or use of a multigene panel.

  • Single-gene testing
    • In individuals with Oji-Cree ancestry, gene-targeted deletion/duplication analysis to detect intragenic deletions or duplications of FREM1 may be considered first. If only one or no pathogenic variant is found, sequence analysis of FREM1 can be performed.
    • In individuals of other ethnicities, sequence analysis of FREM1 that detects small intragenic deletions/insertions and missense, nonsense, and splice site variants can be performed first. If only one or no pathogenic variant is found, deletion/duplication analysis of FREM1 can be performed.
  • A multigene panel that includes FREM1 and other genes of interest (see Differential Diagnosis) is most likely to identify the genetic cause of the condition while limiting identification of variants of uncertain significance and pathogenic variants in genes that do not explain the underlying phenotype. Note: (1) The genes included in the panel and the diagnostic sensitivity of the testing used for each gene vary by laboratory and are likely to change over time. (2) Some multigene panels may include genes not associated with the condition discussed in this GeneReview. (3) In some laboratories, panel options may include a custom laboratory-designed panel and/or custom phenotype-focused exome analysis that includes genes specified by the clinician. (4) Methods used in a panel may include sequence analysis, deletion/duplication analysis, and/or other non-sequencing-based tests. For this disorder a multigene panel that also includes deletion/duplication analysis is recommended (see Table 1).
    For an introduction to multigene panels click here. More detailed information for clinicians ordering genetic tests can be found here.

Option 2

When the diagnosis of a FREM1 autosomal recessive disorder is not considered because an individual has an atypical phenotype, comprehensive genomic testing (which does not require the clinician to determine which gene[s] are likely involved) is the best option. Exome sequencing is most commonly used; genome sequencing is also possible.

If exome sequencing is not diagnostic, exome array (when clinically available) may be considered to detect (multi)exon deletions or duplications that cannot be detected by sequence analysis.

For an introduction to comprehensive genomic testing click here. More detailed information for clinicians ordering genomic testing can be found here.

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Table 1.

Molecular Genetic Testing Used in FREM1 Autosomal Recessive Disorders

Clinical Characteristics

Clinical Description

Manitoba Oculotrichoanal (MOTA) Syndrome

Ocular abnormalities include ipsilateral colobomas of the upper eyelid (sometimes referred to as a Tessier number 10 cleft by surgeons), corneopalpebral synechiae (i.e., adhesions between the eyelids and the cornea, also known as abortive cryptophthalmos), and microphthalmia/anophthalmia and/or cryptophthalmos. Anomalies may be unilateral or bilateral; the severity may differ between the two eyes.

Visual impairment may result directly from the ocular malformations or indirectly from exposure keratopathy. The long-term visual outcome depends on the severity of the ocular malformations and is poor for individuals with bilateral complete cryptophthalmos. In those with milder ocular malformations, such as upper eyelid colobomas, vision is typically intact.

Corneal clouding was described in one individual.

Anal anomalies include anal stenosis and/or anteriorly placed anus. No associated anomalies of the sacrum, vertebrae, or tethered cord have been reported. No affected individuals have had refractory constipation, fecal incontinence, or procedure-related stenosis or fistula.

Characteristic facial features include widely spaced eyes; an aberrant anterior hairline extending to the ipsilateral eye (unilateral or bilateral) that is often wedge-shaped but may also resemble a thin stripe or appear tongue-shaped; ipsilateral absent or interrupted eyebrow; and a broad nose or notched or bifid nasal tip.

Omphalocele or umbilical hernia has been reported in approximately one third of affected individuals. Conservative management or surgical intervention for omphalocele or umbilical hernia is usually well tolerated and outcomes are excellent. Long-term intestinal complications have not been described.

Other. Additional findings have been reported: renal pelviectasis, renal dysplasia, hydrometrocolpos and vaginal atresia, cutaneous syndactyly, and additional dysmorphic features (e.g., high forehead with a frontal upsweep of hair, dysplastic ears, maxillary hypoplasia, underdeveloped ala nasi, short philtrum, thin upper lip, and relative microstomia) [Slavotinek et al 2011, Mitter et al 2012, Nathanson et al 2013].

Growth and development. Individuals with MOTA syndrome assessed at various ages appear generally healthy with age-appropriate growth and cognition. Motor, social, and speech and language skills are typically normal, although development may be influenced by the presence of severe eye defects that lead to visual impairment.

The manifestations and degree of severity vary even among affected members of the same family.

Bifid Nose with or without Anorectal and Renal Anomalies (BNAR) Syndrome

BNAR syndrome was described by Al-Gazali et al [2002] and Alazami et al [2009] in ten individuals from three consanguineous families of Egyptian, Afghani, and Pakistani origin.

  • Craniofacial features. Broad and/or bifid nose (100%), widely spaced eyes, short and thick oral frenula
  • Renal malformations (e.g., bilateral renal agenesis, unilateral renal agenesis) in 6/9 individuals evaluated
  • Anorectal malformations (e.g., anteriorly placed anus, anal stenosis) in 2/9 individuals evaluated
  • Airway malformations in 2/8 individuals evaluated

FREM1 Congenital Anomalies of Kidney and Urinary Tract (CAKUT)

FREM1-CAKUT phenotype has been reported in an individual with bilateral vesicoureteral reflux (VUR) grade III and in another individual with right-sided VUR grade V in conjunction with right-sided renal hypodysplasia [Kohl et al 2014].

Other Phenotypes

The following other phenotypes have been reported in individuals with biallelic FREM1 pathogenic variants:

  • One individual with isolated congenital diaphragmatic hernia [Beck et al 2013]
  • One fetus with severe hydrocephalus and shortened limbs associated with novel FREM1 pathogenic variants [Yang et al 2017]

Genotype-Phenotype Correlations

Genotype-phenotype correlations have not been possible to date given the rarity of the condition and limited number of pathogenic variants described.

Prevalence

The prevalence of FREM1 autosomal recessive disorders are unknown. To date, the authors are aware of 27 published individuals with MOTA syndrome.

Based on the number of individuals identified to date in the aboriginal Oji-Cree community of the Island Lake region of northern Manitoba, Canada, which had a population of 4,685 in 1996 and 2,020 in 2001 [First Nation Profiles 2004], the incidence of MOTA syndrome in that population is estimated at 2:1,000-6:1,000 births; however, this may be an underestimate in this population, as a few presumably affected individuals have also been identified through family histories of affected individuals, and some milder cases may not have come to medical attention. All affected individuals from the Island Lake region identified to date are presumed to be related.

Differential Diagnosis

The following disorders should be considered in the differential diagnosis of Manitoba oculotrichoanal (MOTA) syndrome and bifid nose with or without anorectal and renal anomalies (BNAR) syndrome (Table 2).

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Table 2.

Disorders to Consider in the Differential Diagnosis of MOTA Syndrome and BNAR Syndrome

FREM1 congenital anomalies of kidney and urinary tract (CAKUT). Isolated CAKUT has been associated with more than 20 genes to date and may be inherited in an autosomal dominant, autosomal recessive, or multifactorial manner [Nicolaou et al 2015]. The genetic etiology in most individuals with isolated CAKUT is unknown [Kohl et al 2014].

Management

Evaluations Following Initial Diagnosis

To establish the extent of disease and needs in an individual diagnosed with a FREM1 autosomal recessive disorder, the evaluations summarized in Table 3, Table 4, or Table 5 (depending on the phenotype) are recommended if they have not already been performed as part of the evaluation that led to the diagnosis:

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Table 3.

Recommended Evaluations Following Initial Diagnosis in Individuals with MOTA Syndrome

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Table 4.

Recommended Evaluations Following Initial Diagnosis in Individuals with BNAR Syndrome

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Table 5.

Recommended Evaluations Following Initial Diagnosis in Individuals with FREM1-CAKUT

Treatment of Manifestations

Treatment of FREM1 autosomal recessive disorders consists primarily of surgical intervention with procedures tailored to the specific needs of the individual. A multidisciplinary team comprising a clinical geneticist, general surgeon, ophthalmologist, otolaryngologist, plastic surgeon, and social worker is preferred for optimal management.

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Table 6.

Treatment of Manifestations in Individuals with FREM1 Autosomal Recessive Disorders

Evaluation of Relatives at Risk

See Genetic Counseling for issues related to testing of at-risk relatives for genetic counseling purposes.

Therapies Under Investigation

Search ClinicalTrials.gov in the US and EU Clinical Trials Register in Europe for access to information on clinical studies for a wide range of diseases and conditions. Note: There may not be clinical trials for this disorder.

Genetic Counseling

Genetic counseling is the process of providing individuals and families with information on the nature, mode(s) of inheritance, and implications of genetic disorders to help them make informed medical and personal decisions. The following section deals with genetic risk assessment and the use of family history and genetic testing to clarify genetic status for family members; it is not meant to address all personal, cultural, or ethical issues that may arise or to substitute for consultation with a genetics professional. —ED.

Mode of Inheritance

Manitoba oculotrichoanal (MOTA) syndrome, bifid nose with or without anorectal and renal anomalies (BNAR syndrome), and FREM1 congenital anomalies of kidney and urinary tract (CAKUT) are inherited in an autosomal recessive manner.

Risk to Family Members

Parents of a proband

  • The parents of an affected child are obligate heterozygotes (i.e., carriers of one FREM1 pathogenic variant).
  • Heterozygotes (carriers) are not affected with MOTA, BNAR, or FREM1-CAKUT. To date, heterozygous parents of individuals with MOTA, BNAR, or FREM1-CAKUT have not been reported to have FREM1 trigonocephaly (see Genetically Related Disorders).

Sibs of a proband

  • At conception, each sib of an affected individual has a 25% chance of being affected, a 50% chance of being heterozygous, and a 25% chance of being unaffected and not a carrier.
  • Heterozygotes (carriers) are not affected with MOTA, BNAR, or FREM1-CAKUT. To date, heterozygous sibs of individuals with MOTA, BNAR, or FREM1-CAKUT have not been reported to have FREM1 trigonocephaly (see Genetically Related Disorders).

Offspring of a proband. The offspring of an individual with a FREM1 autosomal recessive disorder are obligate heterozygotes (carriers) for a FREM1 pathogenic variant.

Other family members. Each sib of the proband's parents is at a 50% risk of being a carrier of a FREM1 pathogenic variant.

Carrier Detection

Carrier testing for at-risk relatives requires prior identification of the FREM1 pathogenic variants in the family.

Related Genetic Counseling Issues

Family planning

  • The optimal time for determination of genetic risk, clarification of carrier status, and discussion of the availability of prenatal/preimplantation genetic testing is before pregnancy.
  • It is appropriate to offer genetic counseling (including discussion of potential risks to offspring and reproductive options) to young adults who are affected, are carriers, or are at risk of being carriers.

DNA banking. Because it is likely that testing methodology and our understanding of genes, pathogenic mechanisms, and diseases will improve in the future, consideration should be given to banking DNA from probands in whom a molecular diagnosis has not been confirmed (i.e., the causative pathogenic mechanism is unknown). For more information, see Huang et al [2022].

Prenatal Testing and Preimplantation Genetic Testing

Molecular genetic testing. Once the FREM1 pathogenic variants have been identified in an affected family member, prenatal and preimplantation genetic testing are possible.

Pregnancies at high a priori risk. Ultrasound examination may be diagnostic of Manitoba oculotrichoanal (MOTA) syndrome if findings such as omphalocele, cryptophthalmos, anophthalmia/microphthalmia, widely spaced eyes, and/or a wide nose are detected. However, mild findings may be difficult to detect on prenatal imaging.

Pregnancies at low a priori risk. Chromosome analysis and possibly DNA-based testing for other specific disorders with findings similar to MOTA syndrome should be considered when omphalocele and craniofacial features associated with MOTA syndrome are identified on fetal ultrasound examination in a pregnancy not known to be at risk for MOTA syndrome.

Differences in perspective may exist among medical professionals and within families regarding the use of prenatal testing. While most centers would consider use of prenatal testing to be a personal decision, discussion of these issues may be helpful.

Resources

GeneReviews staff has selected the following disease-specific and/or umbrella support organizations and/or registries for the benefit of individuals with this disorder and their families. GeneReviews is not responsible for the information provided by other organizations. For information on selection criteria, click here.

Molecular Genetics

Information in the Molecular Genetics and OMIM tables may differ from that elsewhere in the GeneReview: tables may contain more recent information. —ED.

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Table A.

FREM1 Autosomal Recessive Disorders : Genes and Databases

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Table B.

OMIM Entries for FREM1 Autosomal Recessive Disorders (View All in OMIM)

Molecular Pathogenesis

The FREM1 protein is a member of the FRAS1/FREM family of extracellular matrix proteins that are located in the sublamina densa of epithelial basement membranes during embryogenesis [Pavlakis et al 2011]. FREM1 forms a ternary complex with FRAS1, FREM2, and FREM3, which have similar functional domains and structures [Pavlakis et al 2011]. The ternary complex is critical for maintenance of epithelial-mesenchymal cohesion during embryonic development in mammals [Pavlakis et al 2011]. FREM1 pathogenic variants in humans are predicted to disturb the interactions with the proteins in this complex, although the levels of FRAS1 and FREM2 are not decreased [Vissers et al 2011]. Loss or disruption of the ternary complex is thought to reduce epithelial-mesenchymal adhesion during development, with subsequent generation of the characteristic clinical findings associated with Fraser syndrome and the FREM1 autosomal recessive disorders [Chacon-Camacho et al 2017].

Mechanism of disease causation. All pathogenic variants reported to date in FREM1 are hypothesized to result in loss of function.

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Table 7.

Notable FREM1 Pathogenic Variants

Chapter Notes

Author History

Albert E Chudley, MD, FRCPC, FCCMG; University of Manitoba (2011-2019)
Chumei Li, MD, PhD, FRCPC, FCCMG (2008-present)
Anne Slavotinek, MBBS, PhD (2011-present)

Revision History

  • 9 May 2019 (sw) Comprehensive update posted live
  • 13 October 2011 (me) Comprehensive update posted live
  • 9 July 2008 (me) Review posted live
  • 16 May 2008 (cl) Original submission

References

Literature Cited

  • Alazami AM, Shaheen R, Alzahrani F, Snape K, Saggar A, Brinkmann B, Bavi P, Al-Gazali LI, Alkuraya FS. FREM1 mutations cause bifid nose, renal agenesis, and anorectal malformations syndrome. Am J Hum Genet. 2009;85:414–8. [PMC free article: PMC2771533] [PubMed: 19732862]

  • Al-Gazali LI, Bakir M, Hamud OA, Gerami S. An autosomal recessive syndrome of nasal anomalies associated with renal and anorectal malformations. Clin Dysmorphol. 2002;11:33–8. [PubMed: 11822703]

  • Beck TF, Veenma D, Shchelochkov OA, Yu Z, Kim BJ, Zaveri HP, van Bever Y, Choi S, Douben H, Bertin TK, Patel PI, Lee B, Tibboel D, de Klein A, Stockton DW, Justice MJ, Scott DA. Deficiency of FRAS1-related extracellular matrix 1 (FREM1) causes congenital diaphragmatic hernia in humans and mice. Hum Mol Genet. 2013;22:1026–38. [PMC free article: PMC3561915] [PubMed: 23221805]

  • Chacon-Camacho OF, Zenker M, Schanze D, Ledesma-Gil J, Zenteno JC. Novel FREM1 mutations in a patient with MOTA syndrome: clinical findings, mutation update and review of FREM1-related disorders literature. Eur J Med Genet. 2017;60:190–4. [PubMed: 28111185]

  • First Nation Profiles. Indigenous and Northern Affairs Canada website. 2004. Accessed 5-23-23.

  • Huang SJ, Amendola LM, Sternen DL. Variation among DNA banking consent forms: points for clinicians to bank on. J Community Genet. 2022;13:389–97. [PMC free article: PMC9314484] [PubMed: 35834113]

  • Jones KL. Frontonasal dysplasia sequence. In: Smith’s Recognizable Patterns of Human Malformation. 6 ed. Philadelphia, PA: Elsevier Saunders; 2006:1268-9.

  • Kohl S, Hwang DY, Dworschak GC, Hilger AC, Saisawat P, Vivante A, Stajic N, Bogdanovic R, Reutter HM, Kehinde EO, Tasic V, Hildebrandt F. Mild recessive mutations in six Fraser syndrome-related genes cause isolated congenital anomalies of the kidney and urinary tract. J Am Soc Nephrol. 2014;25:1917–22. [PMC free article: PMC4147986] [PubMed: 24700879]

  • McGregor L, Makela V, Darling SM, Vrontou S, Chalepakis G, Roberts C, Smart N, Rutland P, Prescott N, Hopkins J, Bentley E, Shaw A, Roberts E, Mueller R, Jadeja S, Philip N, Nelson J, Francannet C, Perez AA, Megarband A, Kerr B, Wainwright B, Woolf AS, Winter RM, Scambler PJ. Fraser syndrome and mouse blebbed phenotype caused by mutations in FRAS1/Fras1 encoding a putative extracellular matrix protein. Nat Genet. 2003;34:203–8. [PubMed: 12766769]

  • Mitter D, Schanze D, Sterker I, Müller D, Till H, Zenker M. MOTA syndrome: molecular genetic confirmation of the diagnosis in a newborn with previously unreported clinical features. Mol Syndromol. 2012;3:136–9. [PMC free article: PMC3473350] [PubMed: 23112756]

  • Nathanson J, Swarr DT, Singer A, Liu M, Chinn A, Jones W, Hurst J, Khalek N, Zackai E, Slavotinek A. Novel FREM1 mutations expand the phenotypic spectrum associated with Manitoba-oculo-tricho-anal (MOTA) syndrome and bifid nose renal agenesis anorectal malformations (BNAR) syndrome. Am J Med Genet A. 2013;161A:473–8. [PMC free article: PMC3581754] [PubMed: 23401257]

  • Nicolaou N, Renkema KY, Bongers EM, Giles RH, Knoers NV. Genetic, environmental, and epigenetic factors involved in CAKUT. Nat Rev Nephrol. 2015;11:720–31. [PubMed: 26281895]

  • Nouby G. Congenital upper eyelid coloboma and cryptophthalmos. Ophthal Plast Reconstr Surg. 2002;18:373–7. [PubMed: 12352825]

  • Pavlakis E, Chiotaki R, Chalepakis G. The role of Fras1/Frem proteins in the structure and function of the basement membrane. Int J Biochem Cell Biol. 2011;43:487–95. [PubMed: 21182980]

  • Richards S, Aziz N, Bale S, Bick D, Das S, Gastier-Foster J, Grody WW, Hegde M, Lyon E, Spector E, Voelkerding K, Rehm HL, et al. Standards and guidelines for the interpretation of sequence variants: a joint consensus recommendation of the American College of Medical Genetics and Genomics and the Association for Molecular Pathology. Genet Med. 2015;17:405–24. [PMC free article: PMC4544753] [PubMed: 25741868]

  • Seah LL, Choo CT, Fong KS. Congenital upper lid colobomas: management and visual outcome. Ophthal Plast Reconstr Surg. 2002;18:190–5. [PubMed: 12021649]

  • Slavotinek AM, Baranzini SE, Schanze D, Labelle-Dumais C, Short KM, Chao R, Yahyavi M, Bijlsma EK, Chu C, Musone S, Wheatley A, Kwok PY, Marles S, Fryns JP, Maga AM, Hassan MG, Gould DB, Madireddy L, Li C, Cox TC, Smyth I, Chudley AE, Zenker M. Manitoba-oculo-tricho-anal (MOTA) syndrome is caused by mutations in FREM1. J Med Genet. 2011;48:375–82. [PMC free article: PMC4294942] [PubMed: 21507892]

  • Slavotinek AM, Tifft CJ. Fraser syndrome and cryptophthalmos: review of the diagnostic criteria and evidence for phenotypic modules in complex malformation syndromes. J Med Genet. 2002;39:623–33. [PMC free article: PMC1735240] [PubMed: 12205104]

  • Swinkels ME, Simons A, Smeets DF, Vissers LE, Veltman JA, Pfundt R, de Vries BB, Faas BH, Schrander-Stumpel CT, McCann E, Sweeney E, May P, Draaisma JM, Knoers NV, van Kessel AG, van Ravenswaaij-Arts CM. Clinical and cytogenetic characterization of 13 Dutch patients with deletion 9p syndrome: delineation of the critical region for a consensus phenotype. Am J Med Genet A. 2008;146A:1430–8. [PubMed: 18452192]

  • Twigg SRF, Kan R, Babbs C, Bochukova EG, Robertson SP, Wall SA, Morriss-Kay GM, Wilkie AOM. Mutations of ephrin-B1 (EFNB1), a marker of tissue boundary formation, cause craniofrontonasal syndrome. Proc Nat Acad Sci. 2004;101:8652–7. [PMC free article: PMC423250] [PubMed: 15166289]

  • Vissers LE, Cox TC, Maga AM, Short KM, Wiradjaja F, Janssen IM, Jehee F, Bertola D, Liu J, Yagnik G, Sekiguchi K, Kiyozumi D, van Bokhoven H, Marcelis C, Cunningham ML, Anderson PJ, Boyadjiev SA, Passos-Bueno MR, Veltman JA, Smyth I, Buckley MF, Roscioli T. Heterozygous mutations of FREM1 are associated with an increased risk of isolated metopic craniosynostosis in humans and mice. PLoS Genet. 2011;7:e1002278. [PMC free article: PMC3169541] [PubMed: 21931569]

  • Vrontou S, Petrou P, Meyer BI, Galanopoulos VK, Imai K, Yanagi M, Chowdhury K, Scambler PJ, Chalepakis G. Fras1 deficiency results in cryptophthalmos, renal agenesis and blebbed phenotype in mice. Nat Genet. 2003;34:209–14. [PubMed: 12766770]

  • Wieland I, Jakubiczka S, Muschke P, Cohen M, Thiele H, Gerlach KL, Adams RH, Wieacker P. Mutations of the ephrin-B1 gene cause craniofrontonasal syndrome. Am J Hum Genet. 2004;74:1209–15. [PMC free article: PMC1182084] [PubMed: 15124102]

  • Yang YD, Huang LY, Yan JM, Han J, Zhang Y, Li DZ. Novel FREM1 mutations are associated with severe hydrocephalus and shortened limbs in a prenatal case. Eur J Obstet Gynecol Reprod Biol. 2017;215:262–4. [PubMed: 28622873]