Identification of Caprine KRTAP28-1 and Its Effect on Cashmere Fiber Diameter

The keratin-associated proteins (KAPs) are constituents of cashmere fibers and variation in many KAP genes (KRTAPs) has been found to be associated with fiber traits. The gene encoding the high-sulphur KAP28-1 has been described in sheep, but it has not been identified in the goat genome. In this study, a 255-bp open reading frame on goat chromosome 1 was identified using a search of similar sequence to ovine KRTAP28-1, and that would if transcribed and translated encode a high sulphur KAP. Based on the analysis of polymerase chain reaction (PCR) amplicons for the goat nucleotide sequences in 385 Longdong cashmere goats in China, five unique banding patterns were detected using single-stranded conformational polymorphism (SSCP). These represented five DNA sequences (named variants A to E) and they had the highest resemblance to KRTAP28-1 sequences from sheep, suggesting A-E are variants of caprine KRTAP28-1. DNA sequencing revealed a 2 or 4-bp deletion and eleven nucleotide sequence differences, including four non-synonymous substitutions. Of the four common variants (A, B, C and D) found in these goats, the presence of variant A was associated with decreased mean fiber diameter and this effect appeared to be additive. These results indicate that caprine KRTAP28-1 variation might have value as a molecular marker for reducing cashmere mean fiber diameter.