Variation in ovine KRTAP8-2 and its association with wool characteristics in Pakistani sheep

The keratin-associated proteins (KAPs) are structural components of wool fibres and variation in genes encoding KAPs may affect wool characteristics. Variation in the KAP gene KRTAP8-2 was investigated in five sheep breeds and crosses in Pakistan. A new sequence of the gene (named variant C) was found, along with the already reported variants A and B. In general linear mixed models (GLMMs) analysing the effect of the presence and absence of these variants on wool traits, the presence of B was found to be associated (P = 0.028) with lower mean staple length (MSL), where the predicted MSL of wool from sheep without B (39.3 ± 8.35 mm) was higher than wool from sheep with B (34.7 ± 9.33 mm). The predicted mean standard deviation of medullation (MeSD) of wool from sheep with variant A (11.2 ± 4.98 %) was lower than wool from sheep without A (32.7 ± 11.80 %), and wool from sheep with B (18.7 ± 8.06 %) had higher predicted MeSDs than wool from sheep without B (10.9 ± 5.06 %). The predicted mean coefficient of variation of medullation (CVMed) of wool from sheep with A (38.6 ± 5.80 %) was lower than wool from sheep without A (88.4 ± 21.21 %), and wool from sheep with B (57.5 ± 12.17 %) had higher predicted CVMed than wool from sheep without B (38.0 ± 6.15 %). In GLMMs analysing genotype differences, the predicted MeSD of wool from sheep of genotype AA (11.1 ± 5.02 %) was lower (P = 0.001) than for wool from sheep of genotype AB (12.9 ± 8.72 %) and BB (33.0 ± 11.88 %), and the CVMed of wool from sheep with genotype AA (37.8 ± 6.17 %) was lower (P < 0.001) than wool from sheep with genotypes AB (43.7 ± 14.23 %) and BB (89.0 ± 21.23 %). Variation in KRTAP8-2 appears to be associated with some important wool traits, but this requires further investigation in more sheep of differing breed