Alternative titles; symbolsKERATIN, CUTICLE, ULTRAHIGH-SULFUR, 1; KRN1HGNC Approved Gene Symbol: KRTAP5-9Cytogenetic location: 11q13.4 Genomic coordinates (G...
Alternative titles; symbols
HGNC Approved Gene Symbol: KRTAP5-9
Cytogenetic location: 11q13.4 Genomic coordinates (GRCh38): 11:71,548,419-71,549,607 (from NCBI)
▼ Biochemical Features
Three proteins are encountered in hair keratin: high-sulfur, low-sulfur and high-tyrosine (Fraser et al., 1973). Human hair contains virtually none of the third type, but about 40% of the first (Gillespie and Frenkel, 1974).
By electrophoresis, Baden and Lee (1974) found polymorphism of one of the polypeptide chains of the alpha-fibrous proteins of human hair. A variant polypeptide was present in about 5% of Caucasians. Family studies showed codominant inheritance. No correlation with color, thickness or texture could be determined. Physical properties other than the electrophoretic ones were normal. A rather wide variability in hair from different individuals is indicated by quantitative amino acid composition, particularly of cysteine and tyrosine (Fraser et al., 1973). Certain portions of the molecule may require high specificity and therefore be restrictive in their composition, whereas others may be more permissive.
Hrdy et al. (1977) found the electrophoretic polymorphism to be limited to Caucasians. (It occurred in one black and one American Indian with presumed Caucasian admixture.) Six of 150 Caucasian samples showed the variant.
Marshall (1980, 1983) observed genetic variation in both the high-sulfur and the low-sulfur protein fractions of fingernails. Baden (1986) suggested that the low-sulfur variant of hair (Baden et al., 1975) may be the same as Marshall's low-sulfur variant of fingernails. For economic reasons, the protein and gene sequences for sheep wool keratins have been determined by Australian scientists. During development, as many as 50 to 100 keratin genes are active in the hair follicle. Hair keratin proteins are classified into 2 large groups, the intermediate filament (IF) proteins and the intermediate filament-associated, or matrix, proteins (IFAPs); within each group the proteins can be further classified into 2 or more families. The hair IF keratin genes comprise 2 families, designated type I and type II, with 4 major components in each.
MacKinnon et al. (1991) reported studies of the map location of hair IF keratin genes. The IFAP group of keratin proteins comprises several families, with most proteins containing a large number of cysteine residues. Genes encoding one of these families, known as the ultrahigh-sulfur keratin (UHSK) proteins because they contain more than 30% cysteine residues, were isolated and their site of expression mapped to human hair and wool cuticle by tissue in situ hybridization. By means of a somatic cell hybrid panel, MacKinnon et al. (1991) mapped a human hair cuticle ultrahigh-sulfur keratin gene (KRN1) to 11pter-q21. With the probe used, in situ hybridization pointed to localization in 2 regions of chromosome 11: the distal part of 11p15, most likely 11p15.5, and the distal part of 11q13, most likely 11q13.5. A probe from the 3-prime noncoding region of KRN1 mapped to 11q13.5. The sequence that mapped to 11p15.5 was termed KRN1-like (148022). Richard et al. (1991) described a high resolution radiation hybrid map of 11q12-q13, which placed KRN1 between SEA (165110) and a group of genes that were not separated out and included HSTF1 (164980).