Identification Of Novel Mutations On Pachyonychia Congenita Type 1

Background Pachyonychia congenita(PC) is an autosomal dominant disorder that usually develops in early infancy.The major features of the syndrome are hypertrophic nail dystrophy,palmoplantar keratoderma and oral leucokeratosis,accompanied by other ectodermal defects according to subtypes.Specifically,PC-1 has been shown to be caused by mutations in keratins K6a and K16.In contrast,PC-2 has been associated with mutations in K6b and K17.K6/K16 are co-expressed in a number of differentiated epithelial structures,including palmoplantar epidermis,mucosal epithelia,follicular keratinocytes and nail bed;whereas K17 is expressed in the pilosebaceous unit and basal appendageal keratinocytes.To date,over 33 mutations in the K6a and K16 gene have been identified,the majority of these mutations are missense mutations. Comparison between genotype and phenotype failed to yield any clear correlation between the nature of the mutation and the clinical features of PC.In the present study, we have collected four familials and four sporadics with PC-1,and examined the K6a and K16 genes mutation by direct sequencing.Objective To Analyzes the K6a/K16 genes mutation in Chinese patients with PC-1 and to explore the relationship between the genetype and phenotype of PC-1.Methods Genomic DNA was extracted from peripheral blood of the patient with PC-1 and 100 unrelated normal persons.The whole coding region of the K6a/K16 genes were amplified using long-range polymerase chain reaction(PCR),then nested PCR were used to amplify the mutation 'hot-spot' of the K6a/K16 genes.The PCR products were directly sequenced to detect the mutation.Result Seven missense mutations(N171K,F174S×2,Q166P,1178N,A463P, Y468H)and a delection mutation(N172del)of the K6a polypeptide were identified in the patiem.But not in the healthy individuals from family and 100 unrelated normal individuals.Conclusion We described these mutations of K6a Q166P,K6a N171K,K6a F174S, K6a Q166P,K6a I178N,K6a A463P,K6a Y468H,which caused me disease and provided further evidence that the helix boundary motif sequences of K6a is a mutation 'hot—spot'.