In this study, we describe the identification of caprine KRTAP28-1 and the detection of nucleotide sequence variation in this gene. However, KAP28-1 (or its encoding gene KRTAP28-1) has been not identified in goats up to now. This suggests that KRTAP28-1 is polymorphic and that the effect of variation in KRTAP28-1 on fiber traits is worthy of investigation in other species. Six variants of the gene, containing eight sequence variations have been reported, and associations between ovine KRTAP28-1 genotype and mean fiber diameter have been found. The KRTAP28-1 gene, which encodes for a high sulphur KAP protein, has been described in sheep. Of the KAP genes identified in goats, variation in five KRTAPs ( KRTAP8-2, KRTAP13-1, KRTAP20-1, KRTAP20-2 and KRTAP24-1) has been found to affect cashmere traits including mean fiber diameter, cashmere weight and crimped fiber length. ![]() However, only 14 KRTAPs from 10 families have been identified in goats, with this suggesting that many of the KAP genes found in humans and sheep, remain to be identified. For example, at least 80 functional KRTAPs from 25 families and 36 KRTAPs from 19 families have been reported in humans and sheep respectively. They have been further subdivided into KAP families.Ĭompared to humans and sheep, the number of KAP genes ( KRTAPs) identified to date in the goat genome is relatively small. According to their amino acid composition, mammalian KAPs have historically been distributed into three broad groups: the high glycine/tyrosine (HGT 35−60 mol% glycine and tyrosine), the high sulphur (HS ≤30 mol% cysteine) and the ultra-high sulphur (UHS >30 mol% cysteine) KAPs. The KAPs are proteins that typically have either a high content of cysteine, or of both glycine and tyrosine. It is believed that both types of protein play important roles in governing the properties of the fibers. The former is assembled into intermediate filaments (IFs), while the latter cross-link the keratins in the IFs to form a semi-rigid matrix. Ĭashmere fibers are proteinaceous and consist of keratins and keratin-associated proteins (KAPs). Compared to other cashmere goat breeds, the Longdong cashmere goat has a lower mean fiber diameter, but also has a reduced fleece weight. The number of Longdong cashmere goats in China is approximately 1.6 million. It is used for both cashmere and meat production and is well adapted to harsh environments including desert and other arid regions. The Longdong cashmere goat is a breed that has been created as a cross between the Liaoning cashmere goat, the Inner Mongolian cashmere goat and the Ziwuling black goat. The Gansu province of China is the main region of cashmere goat breeding in China, and it is home to well-known cashmere goat breeds including the Hexi cashmere goat, the Longdong cashmere goat and the Zhongwei goat. China is the largest producer of cashmere fiber, producing a third to a half of total global cashmere production, and this is widely exported. ![]() As a consequence of its physical properties, the price of cashmere is generally much higher than that of wool. These results indicate that caprine KRTAP28-1 variation might have value as a molecular marker for reducing cashmere mean fiber diameter.Ĭashmere fiber is produced by the secondary fiber follicles of cashmere goats. 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. DNA sequencing revealed a 2 or 4-bp deletion and eleven nucleotide sequence differences, including four non-synonymous substitutions. 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. Based on the analysis of polymerase chain reaction amplicons for the goat nucleotide sequences in 385 Longdong cashmere goats in China, five unique banding patterns were detected using single strand conformation polymorphism analysis. 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. The gene encoding the high-sulphur KAP28-1 has been described in sheep, but it has not been identified in the goat genome. 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.
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