Identification of the ovine keratin-associated protein KAP1-2 gene (KRTAP1-2)

Abstract

Keratin-associated proteins (KAPs) are a major component of wool and other keratin-containing tissues. While four KAP1-n proteins have been identified in sheep, only three genes have been described encoding KAP1-1, KAP1-3 and KAP1-4. Here, we used a sequence conserved across the known KAP1-n genes to search the inaugural Ovine Genome Sequence (v1.0) and identified a new KAP1-n sequence on chromosome 11. PCR amplification of this sequence revealed an open reading frame of 474-bp that putatively encodes a polypeptide sequence very similar to the previously described ovine KAP1-2 protein and suggests that the newly identified sequence represents the previously unidentified KAP1-2 gene (KRTAP1-2). Its expression in skin was confirmed by PCR, and the mRNA was localized to the cortex of the mid-keratinization zone of a growing wool fibre using a gene-specific probe and in situ hybridization. PCR-SSCP analysis of KRTAP1-2 revealed nine unique banding patterns representing nine different DNA sequences. One sequence was identical to, and the other eight were homologous to, the sequence identified above, suggesting that they were allelic variants of ovine KRTAP1-2. There were ten single nucleotide substitutions identified, although only three of these were non-synonymous and would potentially result in amino acid changes. The variation identified here may influence the expression or protein structure of KAP1-2 and consequently wool structure and wool traits.

Identification of the keratin-associated protein 13-3 (KAP13-3) gene in sheep

“…These ovine HS-KAP genes are KRTAP1-1 [5], KRTAP1-2 [6], KRTAP1-3 [5], KRTAP1-4 [5], KRTAP3-2 [7], KRTAP3-3 [7] and KRTAP11-1 [8]. Many homologues of the human HS-KAP genes remain unidentified in sheep.…”

Unravelling the proteome of wool: Towards markers of wool quality traits

“…Both for the keratins and KAPs, one of the main problems is the high degree of homology (based on % sequence identity) found within each family, which can be as high as 92% between some members of the Type I keratins and 85% among the Type II keratins. Similar degrees of homology have been also observed for the KAPs and here the situation is further complicated by the existence of polymorphism in some families, notably KAP1.1 [10], KAP1.2 [11], KAP1.3 [12], KAP5.4 [13], KAP7.1, KAP8.1 [14] and KAP11.1 [15]. Nevertheless, studies have provided evidence of distinctive variation of some of these proteins both within and between breeds [16].…”

Contrasting patterns of coding and flanking region evolution in mammalian keratin associated protein-1 genes

“…Previously, the KRTAP1 genes of sheep were shown to contain a variable number of occurrences of a QTSCCQPXXX decapeptide tandem repeat in the N-terminal region of the protein (R ogers et al . 1994; G ong et al . 2011; G ong et al .…”

“…2008; G ong et al . 2010a; G ong et al . 2011) were used to search the genomes of cattle, horses, rabbits and African elephants using BLAST with default parameters, and the genes retrieved were identified by sequence identity within both the coding and flanking regions ( Table S1 ).…”

“…Intra-specific variation was assessed using three sequences for KRTAP1-1 (I tenge -M weza et al . 2007), eleven sequences for KRTAP1-2 (G ong et al . 2011; G ong et al .…”