Mutations in the Keratin 85 (KRT85/Hhb5) Gene Underlie Pure Hair and Nail Ectodermal Dysplasia
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Y Shimomura et al. Mutations in the KRT85 Gene Mutations in the Keratin 85 (KRT85/hHb5) Gene Underlie Pure Hair and Nail Ectodermal Dysplasia Journal of Investigative Dermatology (2010) 130, 892–895; doi:10.1038/jid.2009.341; published online 29 October 2009 TO THE EDITOR monilethrix hair (Ito et al., 1990). Never- ence sequences (NCBI accession num- Pure hair and nail ectodermal dysplasia theless, it suggests abnormal keratiniza- ber: NG_008353). We identified (PHNED; OMIM 602032) is a con- tion of the hair shaft. As compared with homozygous mutations in the KRT85 in genital disorder characterized by Family A, affected individuals in Family both families. All affected individuals in hypotrichosis and nail dystrophy. The B show a more severe phenotype. They Family A are homozygous for a deletion disease can show either an autosomal display complete alopecia with diffuse mutation c.1448_1449delCT in exon 9 dominant (Barbareschi et al., 1997) or follicular papules on the scalp (Figure of the KRT85 gene, which was not autosomal recessive (Calzavara-Pinton 1g). Facial and body hairs are also reported previously and is predicted to et al., 1991) inheritance pattern. The absent. Furthermore, the tips of nails result in a frameshift at codon 483 and a autosomal recessive form has been show severe deformities (Figure 1h). premature termination codon 18 amino mapped to chromosome 17p12–q21.2 Affected individuals in both families acid residues downstream of the muta- (Naeem et al., 2006a) and 12p11.1– show normal facial features, teeth, and tion (p.Pro483ArgfsX18) (Figure 2a, b). q21.1 (Naeem et al., 2006b, 2007), sweating, and do not show palmoplantar Screening assays with the restriction which contain the type I and type II hyperkeratosis. enzyme NlaIV confirmed that the muta- keratin clusters, respectively. One After obtaining informed consent, tion completely co-segregates with the homozygous mutation in a type II hair we collected peripheral blood samples disease phenotype, and 100 healthy keratin gene KRT85, previously known from members of both families and 100 control individuals from Pakistan do as hHb5, was recently identified in population-matched unrelated healthy not carry the mutation (data not shown). a consanguineous Pakistani family with control individuals in EDTA-containing Since the mutation is located within the autosomal recessive PHNED (Naeem tubes (under institutional approval last exon of the KRT85 gene, aberrant et al., 2006b). However, the clinical and in adherence to the Declaration transcripts with the PTC may be ex- characteristics and the molecular basis of Helsinki Principles). Genomic DNA pressed, and a truncated K85 protein of the disease have been poorly under- was isolated from these samples accor- would be generated. The altered amino stood to date. In this study, we identi- ding to standard techniques. On the acid sequences in C-terminus of the fied two consanguineous Pakistani basis of the clinical features, we diag- mutant K85 protein are largely different families with PHNED and found two nosed both families as PHNED. We first from those of the wild-type K85 protein. distinct homozygous mutations in the performed genotyping using micro- In particular, the mutant protein lacks KRT85 gene in both families. satellite markers around the type I two cysteine residues at amino acid We analyzed two consanguineous keratin cluster on chromosome 17q21 positions 489 and 498 (Figure 2b). Pakistani families, designated as Families and type II keratin cluster on chromo- Therefore, the mutant protein with an A and B, with several affected indivi- some 12q13. The results excluded abnormal tail domain would deleter- duals. Both families show autosomal linkage to the type I keratin cluster in iously affect heterodimer formation. recessive inheritance of the disease both families (data not shown), and The affected individual in Family B trait (Figure 1a). All affected individuals suggested linkage of both families is homozygous for a G-to-A substitu- in both families have shown hypotricho- to the type II keratin cluster (Figure tion at position 233 in exon 1 of the sis and nail dystrophy since birth, but 1a). In particular, critical recombina- KRT85 gene (c.233G4A), which leads there is a difference in severity between tion events were detected between to the transition from arginine to the two families. In Family A, all affected markers D12S398 and D12S1618 in histidine at amino acid position 78 individuals show sparse hair and affected individual IV-1 of family A, as (p.Arg78His) (Figure 2c). This mutation diffuse follicular papules on the scalp well as between markers D12S368 and was previously identified in a Pakistani (Figure 1b-d). Facial and body hair is D12S398 in unaffected individual III-2 family with PHNED, which shows less dense overall. In addition, distal of family A, which allowed the interval complete alopecia and severe nail ends of nails are irregularly shaped of linkage to be narrowed to 1.26 Mb dystrophy (Naeem et al., 2006b). and break easily (Figure 1e). It is flanked by markers D12S368 and It is noteworthy that Family B also noteworthy that the patients’ scalp hair D12S1618 (Figure 1a). The KRT85 gene exhibits severe hair and nail pheno- shows fragility. Scanning electron micro- resides in this region. types, which may suggest that the scopy showed that the thickness of We next sequenced the KRT85 mutation p.Arg78His would disrupt the hair shaft was inconsistent (Figure gene in affected individuals from both the function of the K85 protein 1f). The variation in hair diameter did not families using gene-specific primers, more severely than the mutation show a periodic pattern as observed in which were designed based on refer- p.Pro483ArgfsX18. Including the two 892 Journal of Investigative Dermatology (2010), Volume 130 Y Shimomura et al. Mutations in the KRT85 Gene a Family A Family B I I II II III III IV IV V Type II keratin gene cluster bcd e f 98.2 µm 78.2 µm 89.1 µm f g Figure 1. Pedigrees and clinical appearance of two Pakistani families with PHNED. (a) Pedigrees and results of haplotype analysis. The linked haplotypes are indicated in red, and critical recombination events are indicated by arrows. (b–e) Clinical features of affected individuals in Family A. (f) SEM observation of hair of an affected individual in Family A. Bar ¼ 100 mm. (g, h) Clinical features of affected individuals in Family B. Note that affected individuals in Family B show a more severe phenotype than those in Family A. families in this report, only three cases with KRT85 mutations will be The K85 protein is abundantly families with two distinct KRT85 muta- required to determine clear genotype–- expressed in the matrix, precortex, tions have been identified. Additional phenotype correlations. cortex, and cuticle of the hair shaft www.jidonline.org 893 Y Shimomura et al. Mutations in the KRT85 Gene 481 482 483 484 485 V A R L L 481 482 483 484 485 G T GGGCCC A CCCTTG 481 482 483 484 485 VAARLL V PPSSVAPD GGGGTTCCCCCCA TTG G T GGCCCC GGAACCCTTTGGCCCCGG CCCTT Patient Carrier Control individual wild type 481 VAPDSCAPCQPRSSSFSCGSSRSVRFA* 507 mutant 481 VARLLCPLPASFLQLQLRE* 499 76 77 78 79 80 76 77 78 79 80 C GHSF CGRS F TTGGGC AAACC G CCTTTGGGCAA CCCC G G T A/A homozygous G/G homozygous patient control individual Figure 2. Identification of mutations in the KRT85 gene. (a) A novel homozygous mutation c.1448_1449delCT (p.Pro483ArgfsX18) in the KRT85 gene in Family A. The deleted nucleotides are boxed. (b) Comparison of amino acid sequences between wild-type and the mutant K85 proteins with the mutation p.Pro483ArgfsX18. Amino acid position 483, where the frameshift occurs, is indicated by an arrow. Cysteine residues at positions 489 and 498 in wild-type protein are in blue. Asterisks, stop codon. (c) A homozygous mutation c.233G4A (p.Arg78His) in the KRT85 gene in Family B. (Langbein et al., 2001), as well as the crucial role of K85 in the (AMC). YS is supported by a Research Career Development Award from the Dermatology in the keratogenous zone of the nail keratinization of hair and nails in Foundation. matrix (Perrin et al., 2004). The keratins humans. form the intermediate filaments that Yutaka Shimomura1, Muhammad 1 1 anchor to desmosomal components CONFLICT OF INTEREST Wajid , Mazen Kurban , 2 and maintain the tissue integrity The authors state no conflict of interest. Nobuyuki Sato and (Coulombe and Omary, 2002). We Angela M. Christiano1,3 postulate that dysfunction of K85 1 ACKNOWLEDGMENTS Department of Dermatology, Columbia protein would lead to disruption of University, New York, New York, USA; We gratefully acknowledge the family members 2 keratin intermediate filament formation for having participated in this study. We thank Department of Dermatology, Niigata and abnormal desmosomal assembly Ha Mut Lam for excellent technical assistance. University School of Medicine, Niigata, Japan and 3Department of Genetics and in hair and nails. Our findings not This work was supported by US Public Health Service National Institutes of Health grant Development, Columbia University, only expand the limited spectrum of R01AR44924 from the National Institute of New York, New York, USA KRT85 mutations but also underscore Arthritis and Musculoskeletal and Skin Diseases E-mail: [email protected] 894 Journal of Investigative Dermatology (2010), Volume 130 S Lopez et al. Specific Immunological Response to Budesonide Ito M, Hashimoto K, Katsuumi K, Sato Y (1990) Naeem M, Wajid M, Lee K, Leal SM, Ahmad W REFERENCES Pathogenesis of monilethrix: computer (2006b) A mutation in the hair matrix and Barbareschi M, Cambiaghi S, Crupi AC, Tadini G stereography and electron microscopy. cuticle keratin KRTHB5 gene causes ecto- (1997) Family with ‘‘pure’’ hair–nail ectoder- J Invest Dermatol 95:186–94 dermal dysplasia of hair and nail type. J Med mal dysplasia.