The reference OMIM entry for this protein is 608245

Keratin 71, type ii; krt71
K71
Kb34
Keratin 6, inner root sheath, 1; krt6irs1
K6irs1

DESCRIPTION

KRT71 belongs to a family of type II keratins that are specifically expressed in the inner root sheath of hair follicles (Langbein et al., 2003).

CLONING

By searching for sequences similar to mouse K6irs1, followed by PCR and screening of a human scalp cDNA library, Langbein et al. (2002) cloned KRT71, which they called K6IRS1. The deduced 523-amino acid protein has a calculated molecular mass of 57.3 kD. K6IRS1 has a central alpha-helical rod domain and shares approximately 92% amino acid identity with mouse K6irs1. In situ hybridization and indirect immunofluorescence of human hair follicles demonstrated K6IRS1 expression in the Henle and Huxley layers and in the cuticle of the inner root sheath. In all 3 layers, expression of K6IRS1 began above the germinative cell pool and terminated higher up in the follicle with the asynchronous terminal differentiation of each cell layer. K6IRS1 was also detected in the pseudopods of specialized Huxley cells, termed 'Flugelzellen,' which means 'winged cells.' Along with Henle cells, Flugelzellen form a continuous desmosomal anchorage to the companion layer of the outer root sheath. By in situ hybridization of plucked beard hair follicles, Langbein et al. (2003) found colocalization of K6IRS1 and K6IRS4 (608248) in broad and slender foot processes of Flugelzellen above and below the level of Henle cell differentiation. Fujimoto et al. (2012) performed double indirect immunofluorescence on normal human scalp skin sections with anti-K71 and anti-LIPH (607365) antibodies and observed abundant expression of LIPH in all 3 layers of the inner root sheath of human hair follicles, which finely overlapped with K71.

GENE STRUCTURE

Langbein et al. (2002) determined that the KRT71 gene contains 9 exons and spans about 9.2 kb.

MAPPING

By genomic sequence analysis, Langbein et al. (2003) mapped the KRT71 gene to chromosome 12q13, within a cluster of keratin genes and pseudogenes.

MOLECULAR GENETICS

In affected members of a 3-generation Japanese family segregating autosomal dominant woolly hair/hypotrichosis (HYPT13; 615896), Fujimoto et al. (2012) identified heterozygosity for a missense mutation in the KRT71 gene (F141C; 608245.0001). Functional analysis showed that the mutant protein resulted in mislocalization and severely affected heterodimer formation with type I keratins.

ANIMAL MODEL

Peters et al. (2003) described 'reduced coat-3' (Rco3), a spontaneous recessive mouse mutation. Heterozygous Rco3 mice appeared normal and were indistinguishable from wildtype littermates. Homozygous Rco3 mice were vital and fertile and had a normal life expectancy, but they developed severe alopecia. Rco3 homozygotes were first identified by their curly whiskers around 9 days postpartum. All types of hairs in Rco3 homozygotes were malformed with kinks and twists and could be plucked without force. Histologic analysis revealed that the hair shaft malformations were secondary to defective keratinization of the Henle and Huxley layers of the inner root sheath. Where the wildtype Henle layer showed keratinization, that of Rco3 homozygotes showed accumulation of homogeneous, electron-dense type I keratin aggregates and absence of filament bundles. Peters et al. (2003) identified the Rco3 mutation as a 10-bp deletion in the K6irs1 gene that caused a frameshift after 58 codons, resulting in a K6irs1 protein lacking 422 C-terminal amino acids, including t ... More on the omim web site

Subscribe to this protein entry history

Feb. 23, 2019: Protein entry updated
Automatic update: model status changed

Oct. 20, 2018: Protein entry updated
Automatic update: OMIM entry 608245 was added.

Oct. 19, 2018: Additional information
Initial protein addition to the database. This entry was referenced in Bryk and co-workers. (2017).