Wanner R, Förster H H, Tilmans I, Mischke D
Institut für Experimentelle Onkologie und Transplantationsmedizin, Universitätsklinikum Rudolf Virchow, Freie Universität Berlin, F.R.G.
J Invest Dermatol. 1993 Jun;100(6):735-41. doi: 10.1111/1523-1747.ep12475671.
To appreciate point mutations in keratin genes as causes for hereditary epithelial diseases, the normal variation of these gene sequences in the population must be known. Because genetic polymorphism of keratins at the protein level due to allelic variation has been described for the type II keratins 4 and 5, we have analyzed their corresponding genes using single-strand conformation polymorphism gel electrophoresis and sequence analysis of polymerase chain reaction amplified genomic DNA. Although no sequence variations were found in the carboxyl-terminal and rod domains we were able to map the molecular differences among the alleles to their amino-terminal domains. In particular, we have identified three alleles of keratin 4. Two alleles differed by a nucleotide transition causing a neutral amino acid substitution (alanine to valine) and one allele had a 42-bp in-frame deletion corresponding to 14 amino acids within the V1 subdomain. Three alleles were also recognized for the keratin 5 locus, all being elicited by single nucleotide substitutions. Of these, only one altered the amino acid sequence, replacing an uncharged (glycine) with a charged (glutamic acid) amino acid in the H1 subdomain. Pedigree analyses in three families showed the alleles to be inherited as autosomal Mendelian traits. Thus, these normal alleles of keratins 4 and 5 will provide favorable polymorphic markers for linkage analysis directly within the cluster of type II keratin genes located on chromosome 12q to elucidate the potential involvement of these and other keratin genes in disorders of squamous cell differentiation.
为了认识角蛋白基因中的点突变是遗传性上皮疾病的病因，必须了解这些基因序列在人群中的正常变异情况。由于已经报道了Ⅱ型角蛋白4和5在蛋白质水平上因等位基因变异而产生的遗传多态性，我们使用单链构象多态性凝胶电泳和聚合酶链反应扩增的基因组DNA序列分析，对它们相应的基因进行了分析。虽然在羧基末端和杆状结构域未发现序列变异，但我们能够将等位基因之间的分子差异定位到它们的氨基末端结构域。特别是，我们鉴定出了角蛋白4的三个等位基因。两个等位基因因核苷酸转换而不同，导致中性氨基酸替代（丙氨酸替代缬氨酸），一个等位基因有一个42bp的框内缺失，对应于V1亚结构域内的14个氨基酸。角蛋白5基因座也识别出三个等位基因，均由单核苷酸替代引起。其中只有一个改变了氨基酸序列，在H1亚结构域中用带电荷的（谷氨酸）氨基酸替代了不带电荷的（甘氨酸）氨基酸。对三个家族的系谱分析表明，这些等位基因作为常染色体孟德尔性状遗传。因此，角蛋白4和5的这些正常等位基因将为直接在位于12q染色体上的Ⅱ型角蛋白基因簇内进行连锁分析提供有利的多态性标记，以阐明这些和其他角蛋白基因在鳞状细胞分化障碍中的潜在作用。
