Keratin 35 (KRT35)

Together with the 6 conserved introns expected in the region encoding the alpha-helical domain, the HA5 gene has 7 introns. The predicted 425-amino acid HA5 protein contains a C-terminal domain with 8 cysteine and 10 proline residues. Its N-terminal domain lacks sequence homology with the N-terminal domains of HA1 (KRTHA1), HA3A (KRTHA3A), HA3B (KRTHA3B), and HA4 (KRTHA4), all of which are closely conserved in length and sequence. Northern blot analysis detected a 1.8-kb HA5 transcript in human scalp but not in hairless epidermis. In situ hybridization detected HA5 transcripts mainly in supramatricial cells and lowermost cortical cells of the hair bulb, indicating that HA5 is expressed early in hair morphogenesis; transcripts were not detected in the cuticle.