Alternative titles; symbols
HGNC Approved Gene Symbol: CNBP
SNOMEDCT: 715317001; ICD10CM: G71.11;
Cytogenetic location: 3q21.3 Genomic coordinates (GRCh38) : 3:129,167,827-129,183,896 (from NCBI)
| Location | Phenotype |
Phenotype MIM number |
Inheritance |
Phenotype mapping key |
|---|---|---|---|---|
| 3q21.3 | Myotonic dystrophy 2 | 602668 | Autosomal dominant | 3 |
The ZNF9 protein contains 7 zinc finger domains and is believed to function as an RNA-binding protein (Liquori et al., 2001).
Cholesterol homeostasis is maintained in part by negative feedback regulation of the genes for proteins involved in cholesterol synthesis and the cellular uptake of cholesterol. The apparent coordinate regulation of several such genes, including HMG-CoA reductase (142910), HMG-CoA synthase (142940), farnesylpyrophosphate synthetase (134629), and the LDL receptor (606945) suggest that these genes may be regulated by a common trans-acting factor that is able to 'sense' the levels of cellular sterols. In a search for such a trans-acting factor, Rajavashisth et al. (1989) identified a cDNA that encodes a 19-kD protein containing 7 highly conserved zinc finger repeats with remarkable sequence similarity to the finger domains of the family of retroviral nucleic acid-binding proteins (NBPs). They designated the protein cellular NBP (CNBP). In common with the viral NBPs, CNBP appeared to have a strong preference for single-stranded DNA.
By Northern blot analysis, Shimizu et al. (2003) found that Cnbp was expressed throughout mouse embryonic development. CNBP was expressed in all human tissues and cell lines examined, with highest levels in brain and kidney. The authors used whole-mount in situ hybridization and immunohistochemical analysis to evaluate Cnbp expression form pregastrulation to organogenesis stages of mouse embryogenesis. At embryonic day 5.5 (E5.5), Cnbp expression was initially symmetric and uniform in the epiblast and in the extraembryonic visceral endoderm. At E7.5, Cnbp expression became asymmetrical and localized to all 3 germ layer regions of the anterior conceptus. From E9.0 to E11.5, Cnbp was expressed in brain, early craniofacial structures, limb buds, and somites. Regions of highest expression in the face included cranial and caudal regions of the mandibular prominences, budding maxillary prominences, and roof of the stomodeum. In the distal limb region, at E13.0, Cnbp protein lined the outer regions of developing phalanges within cell nuclei.
Chen et al. (2018) found that mouse Cnbp mRNA was constitutively expressed in numerous tissues, with enrichment in spleen, lung, and muscle. Immunofluorescence analysis of mouse macrophages showed that endogenous Cnbp localized predominantly in cytoplasm at steady state.
Lusis et al. (1990) assigned the CNBP gene to chromosome 3 by Southern analysis of DNAs from mouse/human somatic cell hybrids and regionalized the gene to 3q13.3-q24 by in situ hybridization.
Shimizu et al. (2003) mapped the mouse Cnbp gene to chromosome 6D1-D2.
Using reporter assays, Shimizu et al. (2003) showed that mouse Cnbp functioned as a transactivator of the Myc promoter. Overexpression of Cnbp in P19 embryonic carcinoma cells upregulated Myc expression and enhanced cell proliferation.
Wei et al. (2018) found that recombinant human CNBP interacted with alpha-dystroglycan (DAG1; 128239). This interaction was increased in myotonic dystrophy-2 (DM2; 602668) myofibers.
Using quantitative immunofluorescence of cross-sectional muscle from DM2 patients and controls, Wei et al. (2018) found that CNBP localized predominantly in cytoplasm of control fibers, whereas it localized predominantly in membrane of DM2 fibers. Immunofluorescence analysis of skeletal muscle sections from wildtype and Cnbp-knockout mouse muscle showed that Cnbp localized in nuclei and cytoplasm. Like in human muscle, Cnbp was also detected in the membrane region of mouse fibers.
Using confocal microscopy of mouse bone marrow-derived macrophages (BMDMs), Chen et al. (2018) found that of Cnbp was exclusively cytosolic and excluded from the nuclear compartment in resting cells. Upon stimulation, Cnbp translocated to nucleus, and Cnbp nuclear translocation was identified as a common signal downstream of multiple pattern recognition receptors. BMDMs from Cnbp-deficient mice exhibited impaired inducible expression and production of Il12-beta (IL12B; 161561). Levels of Il10 (124092) were higher in Cnbp-deficient BMDMs, but Cnbp-mediated Il12 production occurred independently of Il10 production. Cnbp was found to regulate nuclear translocation of Rel (164910) and binding of Rel to the Il12b promoter to turn it on. Cnbp protected mice against infection with Toxoplasma gondii, as demonstrated by failure of Cnbp-deficient mice to produce Il12 and IFN-gamma (IFNG; 147570) responses, resulting in reduced Th1 immune response and inability to control parasite replication.
Liquori et al. (2001) demonstrated that a CCTG repeat expansion in intron 1 of the ZNF9 gene is responsible for myotonic dystrophy-2 (DM2; 602668). The range of expanded allele sizes is extremely broad, from 75 to approximately 11,000 CCTG repeats. The mean repeat length is about 5,000. The expanded ZNF9 RNA accumulates in discrete foci within the nucleus. ZNF9 contains 7 zinc finger domains and is thought to be an RNA-binding protein. It is broadly expressed, with the most abundant expression in heart and skeletal muscle, 2 tissues prominently affected in DM2. The similarity of mechanism of mutation between DM2 and DM1 (160900) is striking: a trinucleotide repeat expansion in the 3-prime untranslated region of the DMPK gene (605377) is responsible for DM1. Clinical and molecular parallels between DM1 and DM2 indicate that microsatellite expansions in RNA can themselves be pathogenic.
To investigate the ancestral origins of the DM2 CCTG expansion, Liquori et al. (2003) used 19 short tandem repeat markers flanking the repeat tract to compare haplotypes of 71 families with genetically confirmed DM2. All the families were white, and most were of northern European/German descent; a single family was from Afghanistan. A common interval that was shared by all families with DM2 immediately flanked the repeat, extending up to 216 kb telomeric and 119 kb centromeric of the CCTG expansion. Liquori et al. (2003) examined haplotypes of 228 control chromosomes and identified a potential premutation allele with 20 uninterrupted CCTG repeats on a haplotype that was identical to the most common affected haplotype. The data suggested that the predominant northern European ancestry of families with DM2 resulted from a common founder and that the loss of interruptions within the CCTG portion of the repeat tract may predispose alleles to further expansion. To gain insight into possible function of the repeat tract, the authors looked for evolutionary conservation. The complex repeat motif and flanking sequences within intron 1 were found to be conserved among human, chimpanzee, gorilla, mouse, and rat, suggesting a conserved biologic function.
Bachinski et al. (2003) noted that multiple families, predominantly of German descent, with clinically variable presentations of myotonic dystrophy that included proximal myotonic myopathy (PROMM; 602668) and DM2, but without the DM1 CCTG expansion, had been reported. They presented evidence of linkage to 3q21 and confirmation of the CCTG expansion mutation in intron 1 of ZNF9 in 17 kindreds of European origin with PROMM and proximal myotonic dystrophy from geographically distinct populations. They found a single shared haplotype of at least 132 kb among patients from the different populations. With the exception of the CCTG expansion, the available markers indicated that the DM2 haplotype is identical to the most common haplotype in normal individuals, a situation reminiscent of that seen in DM1. Taken together, these data suggested a single founding mutation in DM2 patients of European origin. Bachinski et al. (2003) estimated the age of the founding haplotype and of the DM2 CCTG expansion mutation to be 200 to 540 generations.
Bachinski et al. (2009) identified 3 classes of large non-DM2 repeat alleles: short interrupted alleles of up to CCTG(24) with 2 interruptions, long interrupted alleles of up to CCTG(32) with up to 4 interruptions, and uninterrupted alleles of CCTG(22-33) with lengths of 92 to 132 bp. Large non-DM2 alleles above 40 repeats were more common among African Americans (8.5%) than European Caucasians (less than 2%). Uninterrupted alleles were significantly more unstable than interrupted alleles (p = 10(-4) to 10(-7)). SNP analysis was consistent with the hypothesis that all large alleles occurred on the same haplotype as the DM2 expansion. Bachinski et al. (2009) concluded that unstable uninterrupted CCTG(22-33) alleles may represent a premutation allele pool for DM2 full mutations.
Wei et al. (2018) generated Cnbp-knockout mice on a pure C57BL background and found that some homozygous Cnbp knockout mice survived until 16 to 20 months of age. Cnbp-knockout mice were small at birth and remained smaller during their life span compared with wildtype. Some Cnbp-knockout mice were weak and died during the first month after birth. Skeletal muscle of Cnbp-knockout mice contained small and thin fibers, with some containing centralized nuclei. Loss of Cnbp also affected sarcomeric structure. Histologic analysis demonstrated that homozygous Cnbp-knockout mice had muscle atrophy at a young age, whereas heterozygous mice exhibited severe muscle loss only at advanced age. Cnbp-knockout skeletal muscle showed alterations in proteins encoded by TOP-containing mRNAs and proteins regulating muscle contraction.
Liquori et al. (2001) found that myotonic dystrophy-2 (DM2; 602668) is caused by a CCTG expansion in intron 1 of the ZNF9 gene. Expanded alleles ranged from 75 to approximately 11,000 CCTG repeats, with a mean of about 5,000 repeats. Repeat length expands with age. Expansion sizes in the blood of affected children are usually shorter than in their parents (reverse anticipation): the time-dependent somatic variation of repeat size complicates interpretation of this difference. No significant correlation between age of onset and expansion size was observed.
Liquori et al. (2003) and Bachinski et al. (2003) provided evidence for a founder effect of the CCTG(n) expansion in European populations.
Saito et al. (2008) reported a Japanese woman with DM2 who had a heterozygous expanded ZNF9 CCTG allele of 3,400 repeats. Haplotype analysis showed a background distinct from that observed in European patients, indicating a different ancestral origin of the mutation in this patient.
Bachinski, L. L., Czernuszewicz, T., Ramagli, L. S., Suominen, T., Shriver, M. D., Udd, B., Siciliano, M. J., Krahe, R. Premutation allele pool in myotonic dystrophy type 2. Neurology 72: 490-497, 2009. [PubMed: 19020295] [Full Text: https://doi.org/10.1212/01.wnl.0000333665.01888.33]
Bachinski, L. L., Udd, B., Meola, G., Sansone, V., Bassez, G., Eymard, B., Thornton, C. A., Moxley, R. T., Harper, P. S., Rogers, M. T., Jurkat-Rott, K., Lehmann-Horn, F., and 11 others. Confirmation of the type 2 myotonic dystrophy (CCTG)n expansion mutation in patients with proximal myotonic myopathy/proximal myotonic dystrophy of different European origins: a single shared haplotype indicates an ancestral founder effect. Am. J. Hum. Genet. 73: 835-848, 2003. [PubMed: 12970845] [Full Text: https://doi.org/10.1086/378566]
Chen, Y., Sharma, S., Assis, P. A., Jiang, Z., Elling, R., Olive, A. J., Hang, S., Bernier, J., Huh, J. R., Sassetti, C. M., Knipe, D. M., Gazzinelli, R. T., Fitzgerald, K. A. CNBP controls IL-12 gene transcription and Th1 immunity. J. Exp. Med. 215: 3136-3150, 2018. [PubMed: 30442645] [Full Text: https://doi.org/10.1084/jem.20181031]
Liquori, C. L., Ikeda, Y., Weatherspoon, M., Ricker, K., Schoser, B. G. H., Dalton, J. C., Day, J. W., Ranum, L. P. W. Myotonic dystrophy type 2: human founder haplotype and evolutionary conservation of the repeat tract. Am. J. Hum. Genet. 73: 849-862, 2003. [PubMed: 14505273] [Full Text: https://doi.org/10.1086/378720]
Liquori, C. L., Ricker, K., Moseley, M. L., Jacobsen, J. F., Kress, W., Naylor, S. L., Day, J. W., Ranum, L. P. W. Myotonic dystrophy type 2 caused by a CCTG expansion in intron 1 of ZNF9. Science 293: 864-867, 2001. [PubMed: 11486088] [Full Text: https://doi.org/10.1126/science.1062125]
Lusis, A. J., Rajavashisth, T. B., Klisak, I., Heinzmann, C., Mohandas, T., Sparkes, R. S. Mapping of the gene for CNBP, a finger protein, to human chromosome 3q13.3-q24. Genomics 8: 411-414, 1990. Note: Erratum: Genomics 9: 564 only, 1991. [PubMed: 2249857] [Full Text: https://doi.org/10.1016/0888-7543(90)90303-c]
Rajavashisth, T. B., Taylor, A. K., Andalibi, A., Svenson, K. L., Lusis, A. J. Identification of a zinc finger protein that binds to the sterol regulatory element. Science 245: 640-643, 1989. [PubMed: 2562787] [Full Text: https://doi.org/10.1126/science.2562787]
Saito, T., Amakusa, Y., Kimura, T., Yahara, O., Aizawa, H., Ikeda, Y., Day, J. W., Ranum, L. P. W., Ohno, K., Matsuura, T. Myotonic dystrophy type 2 in Japan: ancestral origin distinct from Caucasian families. Neurogenetics 9: 61-63, 2008. [PubMed: 18057971] [Full Text: https://doi.org/10.1007/s10048-007-0110-4]
Shimizu, K., Chen, W., Ashique, A. M., Moroi, R., Li, Y.-P. Molecular cloning, developmental expression, promoter analysis and functional characterization of the mouse CNBP gene. Gene 307: 51-62, 2003. [PubMed: 12706888] [Full Text: https://doi.org/10.1016/s0378-1119(03)00406-2]
Wei, C., Stock, L., Schneider-Gold, C., Sommer, C., Timchenko, N. A., Timchenko, L. Reduction of cellular nucleic acid binding protein encoded by a myotonic dystrophy type 2 gene causes muscle atrophy. Molec. Cell. Biol. 38: e00649-17, 2018. Note: Electronic Article. [PubMed: 29735719] [Full Text: https://doi.org/10.1128/MCB.00649-17]