Alternative titles; symbols
HGNC Approved Gene Symbol: GRHL2
SNOMEDCT: 764995008;
Cytogenetic location: 8q22.3 Genomic coordinates (GRCh38): 8:101,492,439-101,681,200 (from NCBI)
| Location | Phenotype |
Phenotype MIM number |
Inheritance |
Phenotype mapping key |
|---|---|---|---|---|
| 8q22.3 | Corneal dystrophy, posterior polymorphous, 4 | 618031 | Autosomal dominant | 3 |
| Deafness, autosomal dominant 28 | 608641 | Autosomal dominant | 3 | |
| Ectodermal dysplasia/short stature syndrome | 616029 | Autosomal recessive | 3 |
Members of the grainyhead-like transcription factor family, such as GRHL2, have essential roles in epithelial morphogenesis and epidermal development (Han et al., 2011).
By PCR analysis of a human fetal cochlea cDNA library, Peters et al. (2002) cloned GRHL2, which they called TFCP2L3. The gene contains a 4,793-bp open reading frame encoding a protein of 625 amino acids that shares 34% identity in the DNA-binding region and 27% overall identity with TFCP2 (189889). Northern blot analysis of human tissues detected a major 6.5-kb transcript and a minor 8.4-kb transcript in prostate. Analysis of a human multiple tissue Northern blot confirmed that TFCP2L3 was highly expressed in the prostate, as well as the placenta, and also showed lower level expression in a variety of epithelial tissues such as thymus, kidney, lung, salivary gland, mammary gland, and digestive tract. Northern blot analyses and in situ hybridization studies showed that mouse Tfcp2l3 was expressed in many epithelial tissues, including cells lining the cochlear duct.
By RT-PCR, Liskova et al. (2018) detected GRHL2 expression in 2 different human corneal epithelial cell lines, but not in a corneal endothelial cell line or endothelial tissue, or in stromal fibroblasts. In a full-thickness corneal sample from a control individual, immunohistochemistry detected GRHL2 in the nuclei of epithelial cells, but not in the endothelium or stroma.
Peters et al. (2002) determined that the GRHL2 gene contains 16 exons.
Peters et al. (2002) identified the GRHL2 gene within the DFNA28 locus (608641) on chromosome 8q22.
Cellular life span is associated with maintenance of telomere length by telomerase, a ribonucleoprotein complex minimally composed of the protein subunit TERT (187270) and an RNA template (TERC; 602322). Chen et al. (2010) found that GRHL2 was expressed in nuclear fractions of growing normal human keratinocytes (NHKs) in culture, but that its nuclear expression was dramatically reduced during cell senescence. Ectopic overexpression of GRHL2 in NHKs increased telomerase activity and led to a significant extension of replicative life span, but it did not promote immortalization. GRHL2 increased expression of TERT and markers of cell growth, including PCNA (176740) and inactivating hyperphosphorylated RB (614041). GRHL2 overexpression also led to downregulation of GRHL1 (609786), GRHL3 (608317), and numerous genes involved in keratinocyte differentiation. In contrast, knockdown of GRHL2 repressed TERT and PCNA expression, telomerase activity, and cell proliferation. In a human tongue carcinoma cell line, knockdown of GRHL2 caused epithelial atrophy, reduced epithelial thickness, and loss of invasive phenotype. Knockdown of TERT in GRHL2-expressing cells abrogated the positive effect of GRHL2 on cell proliferation. GRHL2 directly bound the TERT promoter region near an SP1 (189906)-binding site and inhibited methylation of the CpG island. Knockdown of GRHL2 was associated with TERT promoter hypermethylation. Chen et al. (2010) concluded that GRHL2 enhances TERT expression in keratinocytes by an epigenetic mechanism, resulting in keratinocyte proliferation and increased cellular life span.
Using ATAC-seq analysis, Jacobs et al. (2018) profiled open chromatin across a cohort of inbred Drosophila strains, and found that a Grh-binding site can causally determine the in vivo accessibility of an enhancer-sized region, predicting the presence of potential chromatin regulators for chromatin accessibility. In Drosophila eye-antennal discs, evaluation of the occupancy of Grh-binding sites showed that whenever a region with a Grh motif was accessible, Grh was stably bound there, suggesting that Grh plays a key role in the accessible chromatin landscape of epithelial cells. Further analysis showed that Grh-binding sites are necessary for enhancer accessibility, and Grh binding opens its target enhancers but does not directly activate them. Evolutionary conservation analysis identified some candidate co-transcription factors such as Atonal (Ato; see 601461), indicating that the activity of enhancers primed through Grh binding requires the recruitment of additional factors. Loss-of-function and gain-of-function experiments showed that deletion of Grh causes the loss of DNA accessibility but ectopic expression recovers it, demonstrating that Grh is a 'pioneer factor' that is sufficient to directly and specifically open its target regions in different tissues. Investigation of the local sequence context around the Grh motifs revealed that, like other pioneer factors, Grh preferentially binds to DNA sites in regions that have a high intrinsic affinity for nucleosomes. Jacobs et al. (2018) showed that the 3 Grh-like transcription factors GRHL1, GRHL2, and GRHL3 have similar functions in human cells.
Autosomal Dominant Nonsyndromic Deafness 28
In a large American family with an autosomal dominant form of progressive nonsyndromic sensorineural hearing loss (DFNA28; 608641), Peters et al. (2002) identified a mutation in the GRHL2 gene (608576.0001).
In affected members of a large 5-generation family segregating autosomal dominant postlingual hearing loss with a highly variable age of onset and progression, Vona et al. (2013) identified heterozygosity for a splice site mutation in the GRHL2 gene (608576.0002).
Ectodermal Dysplasia/Short Stature Syndrome
In affected individuals from 2 unrelated consanguineous Kuwaiti families with short stature and ectodermal defects (ECTDS; 616029), Petrof et al. (2014) identified homozygosity for 2 different missense mutations in the GRHL2 gene, Y398H (608576.0003) and I482K (608576.0004). The mutations, which segregated with disease in each family, were not found in controls.
Posterior Polymorphous Corneal Dystrophy 4
In 4 Czech families and 2 British families with posterior polymorphous corneal dystrophy (PPCD4; 618031), Liskova et al. (2018) identified heterozygosity for mutations in intron 1 of the GRHL2 gene (see, e.g., 608576.0005 and 608576.0006) that segregated with disease and were not found in public variant databases. Functional analysis indicated that the mutants significantly increased promoter activity of the intron 1 regulatory region compared to wildtype GRLH2.
Associations Pending Confirmation
See 612448 for discussion of a possible association between variation in the GRHL2 gene and age-related hearing impairment.
Using a gene trap strategy, Han et al. (2011) developed a line of zebrafish with a disruption of the Grhl2b gene. Homozygous Grhl2b mutant embryos appeared grossly normal, including apparently normal patterning and specification of otic vesicles and differentiation of hair cells. However, Grhl2b mutant embryos had enlarged otocysts, thinner otic epithelia, and smaller or eliminated otoliths. Later, Grhl2b mutant fish showed abnormal swimming behavior and reduced survival compared with wildtype. Morpholino-mediated knockdown of Grhl2b in zebrafish resulted in similar defects in otic development. Han et al. (2011) found that zebrafish Grhl2b was required for normal otic expression of the apical junction protein claudin-b (see CLDN4; 602909) and the basolateral junction protein Epcam (185535). Overexpression of wildtype mouse or human GRHL2, but not human GRHL2 with the 1609insC mutation (608576.0001), rescued claudin-b and Epcam expression and otic development in Grhl2b mutant embryos. Han et al. (2011) concluded that, while Grhl2b is widely expressed in the developing zebrafish, it is uniquely critical for inner ear development.
In affected members of a large American family with an autosomal dominant form of progressive nonsyndromic sensorineural hearing loss (DFNA28; 608641), Peters et al. (2002) identified a 1-bp insertion in exon 14 of the GRHL2 gene, 1609insC, resulting in a frameshift with a premature stop codon following 10 novel codons.
In affected members of a large 5-generation family segregating autosomal dominant postlingual hearing loss with a highly variable age of onset and progression (DFNA28; 608641), Vona et al. (2013) identified heterozygosity for a c.1258-1G-A transition in intron 9 of the GRHL2 gene, creating a new 3-prime AG splice site that is shifted by only 1 nucleotide in the 3-prime direction, which causes heterozygous deletion of the first guanine in exon 10 and predicts a premature termination codon in exon 13 (Gly420GlufsTer111). The mutation was present in heterozygosity in the proband's affected mother but was not found in his unaffected father, and it was detected in 4 other family members with hearing loss as well as 2 family members under the age of 44 who had not yet developed hearing loss.
In a brother and sister from a consanguineous Kuwaiti family with ectodermal dysplasia/short stature syndrome (ECTDS; 616029), Petrof et al. (2014) identified homozygosity for a c.1192T-C transition in exon 9 of the GRHL2 gene, resulting in a tyr398-to-his (Y398H) substitution within the DNA-binding domain. The mutation was not found in unaffected family members, in 260 ethnically matched controls, in approximately 1,200 control in-house exomes, or in the 1000 Genomes Project database.
In 2 sisters and a sister and brother from 2 sibships in a consanguineous Kuwaiti family with ectodermal dysplasia/short stature syndrome (ECTDS; 616029), Petrof et al. (2014) identified homozygosity for a c.1445T-A transversion in exon 11 of the GRHL2 gene, resulting in an ile482-to-lys (I482K) substitution within the DNA-binding domain. The mutation was not found in unaffected family members, in 260 ethnically matched controls, in approximately 1,200 control in-house exomes, or in the 1000 Genomes Project database. Quantitative PCR in cultured patient keratinocytes showed reduced expression, and immunoblotting of whole-cell lysates revealed markedly reduced or undetectable amounts of GRHL2. Confocal microscopy of immortalized patient keratinocytes showed that the I482K mutant cells had a less cuboidal, elongated phenotype and failed to form intact cell junctions compared to wildtype cells. There was a reduction in cell-membrane labeling for E-cadherin (CDH1; 192090) at the adherens junctions and for zona occludens-2 (TJP2; 607709) at the tight junctions compared to controls. Mutant GRHL2 staining showed fragmented punctate nuclear localization rather than localization to the cell-cell contact areas and within the nucleus, as with wildtype GRHL2.
In 4 Czech families (C15, C23, C26, and C33) with posterior polymorphous corneal dystrophy (PPCD4; 618031), Liskova et al. (2018) identified heterozygosity for a c.20+544G-T transversion (c.20+544G-T, NM_024915) (chr8:101,493,333G-T, GRCh38) within a conserved promoter region in intron 1 of the GRHL2 gene, involving a specific base known to be a bivalent histone modification site as well as a location marking a DNase I hypersensitive site and CTCF binding site. In 3 of the families, the mutation segregated with disease and haplotype analysis suggested that the mutation arose from a common ancestor; in the fourth family (C33), the mutation was shown to have arisen de novo in the proband. The mutation was not found in the gnomAD, 1000 Genomes Project, UK 10K, GoNL, or Kaviar databases. Functional analysis in transfected HEK293 cells showed that the mutant significantly increased promoter activity of the intron 1 regulatory region compared to wildtype GRHL2. Immunohistochemical analysis of a full-thickness corneal sample from an affected individual in family C23 revealed ectopic expression of GRHL2 in endothelial cell nuclei. In addition, differences in levels of epithelial, mesenchymal, and endothelial markers that were observed between patient and control corneal tissue indicated that PPCD4 endothelial cells were in transition to an epithelial-like cell type or had already diverged.
In a sister and brother from a British family (B5) with posterior polymorphous corneal dystrophy (PPCD4; 618031), Liskova et al. (2018) identified heterozygosity for a 1-bp deletion (c.20+133delA, NM_024915) (chr8:101,492,922delA, GRCh38) within a conserved regulatory region in intron 1 of the GRHL2 gene. The mutation was not found in their unaffected mother or sister, or in 210 Czech controls; DNA from their unaffected deceased father was unavailable. Functional analysis in transfected HEK293 cells showed that the mutant significantly increased promoter activity of the intron 1 regulatory region compared to wildtype GRHL2.
Chen, W., Dong, Q., Shin, K.-H., Kim, R. H., Oh, J.-E., Park, N.-H., Kang, M. K. Grainyhead-like 2 enhances the human telomerase reverse transcriptase gene expression by inhibiting DNA methylation at the 5-prime-CpG island in normal human keratinocytes. J. Biol. Chem. 285: 40852-40863, 2010. [PubMed: 20938050] [Full Text: https://doi.org/10.1074/jbc.M110.103812]
Han, Y., Mu, Y., Li, X., Xu, P., Tong, J., Liu, Z., Ma, T., Zeng, G., Yang, S., Du, J., Meng, A. Grhl2 deficiency impairs otic development and hearing ability in a zebrafish model of the progressive dominant hearing loss DFNA28. Hum. Molec. Genet. 20: 3213-3226, 2011. [PubMed: 21610158] [Full Text: https://doi.org/10.1093/hmg/ddr234]
Jacobs, J., Atkins, M., Davie, K., Imrichova, H., Romanelli, L., Christiaens, V., Hulselmans, G., Potier, D., Wouters, J., Taskiran, I. I., Paciello, G., Gonzalez-Blas, C. B., Koldere, D., Aibar, S., Halder, G., Aerts, S. The transcription factor grainy head primes epithelial enhancers for spatiotemporal activation by displacing nucleosomes. Nature Genet. 50: 1011-1020, 2018. [PubMed: 29867222] [Full Text: https://doi.org/10.1038/s41588-018-0140-x]
Liskova, P., Dudakova, L., Evans, C. J., Rojas Lopez, K. E., Pontikos, N., Athanasiou, D., Jama, H., Sach, J., Skalicka, P., Stranecky, V., Kmoch, S., Thaung, C., Filipec, M., Cheetham, M. E., Davidson, A. E., Tuft, S. J., Hardcastle, A. J. Ectopic GRHL2 expression due to non-coding mutations promotes cell state transition and causes posterior polymorphous corneal dystrophy 4. Am. J. Hum. Genet. 102: 447-459, 2018. [PubMed: 29499165] [Full Text: https://doi.org/10.1016/j.ajhg.2018.02.002]
Peters, L. M., Anderson, D. W., Griffith, A. J., Grundfast, K. M., San Agustin, T. B., Madeo, A. C., Friedman, T. B., Morell, R. J. Mutation of a transcription factor, TFCP2L3, causes progressive autosomal dominant hearing loss, DFNA28. Hum. Molec. Genet. 11: 2877-2885, 2002. [PubMed: 12393799] [Full Text: https://doi.org/10.1093/hmg/11.23.2877]
Petrof, G., Nanda, A., Howden, J., Takeichi, T., McMillan, J. R., Aristodemou, S., Ozoemena, L., Liu, L., South, A. P., Pourreyron, C., Dafou, D., Proudfoot, L. E., Al-Ajmi, H., Akiyama, M., McLean, W. H. I., Simpson, M. A., Parsons, M., McGrath, J. A. Mutations in GRHL2 result in an autosomal-recessive ectodermal dysplasia syndrome. Am. J. Hum. Genet. 95: 308-314, 2014. [PubMed: 25152456] [Full Text: https://doi.org/10.1016/j.ajhg.2014.08.001]
Vona, B., Nanda, I., Neuner, C., Muller, T., Haaf, T. Confirmation of GRHL2 as the gene for the DFNA28 locus. Am. J. Med. Genet. 161A: 2060-2065, 2013. [PubMed: 23813623] [Full Text: https://doi.org/10.1002/ajmg.a.36017]