Elsevier

Small Ruminant Research

Volume 154, September 2017, Pages 129-132
Small Ruminant Research

Short communication
Variation in the KAP6-1 gene in Chinese Tan sheep and associations with variation in wool traits

https://doi.org/10.1016/j.smallrumres.2017.08.001Get rights and content

Highlights

  • Four variants of KRTAP6-1 were found in Tan sheep, including two new variants.

  • A 57-bp deletion associated with increased MFD was not found in Tan sheep.

  • Variation in KRTAP6-1 associated with wool traits in Tan sheep.

Abstract

The keratin-associated protein KAP6-1 gene (KRTAP6-1) was investigated for its effect on wool traits in Chinese Tan sheep. Two previously identified KRTAP6-1 variants (A and B) and two newly identified KRTAP6-1 variants (D and E) were detected with frequencies of 28.9%, 57.1%, 10.3% and 3.7% for A, B, D and E, respectively. The KRTAP6-1 variant C, was not found in the Chinese Tan sheep. Variant D was found to be associated with increased straightened fibre-length at birth, while variant E was found to be associated with increased straightened fibre-length, the number of crimps and the degree of crimping at approximately 35 days post-partum (conventionally called “Er-mao”). Variant E was also associated with increased wool fibre growth rate from birth to Er-mao. These results suggest that variation in ovine KRTAP6-1 may affect wool traits in early life in Chinese Tan sheep.

Introduction

The keratin associated proteins (KAPs) are a structural component of wool fibres and form a matrix that cross-links with the intermediate filaments (Powell and Rogers, 1997). KAPs can be classified into three broad groups on the basis of their amino acid composition: the high glycine-tyrosine (HGT; 35–60 mol% glycine and tyrosine) KAPs, the high sulphur (HS; ≤30 mol% cysteine) KAPs and the ultra-high sulphur (UHS; >30 mol% cysteine) KAPs (Gong et al., 2016). Of these, the HGT-KAPs are predominantly found in the orthocortex of wool fibres and they vary in abundance both between and within breeds (Rogers, 2006, Gillespie, 1990). For example, wool from Lincoln sheep contains less than 1% by weight HGT-KAPs, while Merino wool has between 4% and 12% of HGT-KAPs by weight (Gillespie, 1990). Merino felting lustre (FL) mutant wool contains a low amount of HGT-KAPs (Gillespie and Darskus, 1971), and the expression of the HGT-KAP genes has been revealed to be down-regulated in FL mutant follicles (Li et al., 2009). This variation in the content of HGT-KAPs in wool fibres raises the question of whether these proteins affect the properties of wool.

Three HGT-KAP families have been identified in sheep: KAP6, KAP7 and KAP8 (Gong et al., 2016). KAP6 is a diverse KAP family with five genes identified to date (Zhou et al., 2016). Recently variation in one KAP6 gene (KRATP6-1) has been reported to affect wool fibre diameter-associated traits (Zhou et al., 2015).

Tan sheep are indigenous to China and they are recognised for producing long, curled or crimped, white wool by the early age of approximately 35 days. This is known as the age of “Er-mao” by Chinese people. Four wool crimp patterns have been described for wool at ‘Er-mao”, and these can be translated into “random curly”, “soft and big curly”, “walnut flower curly” and “Chinese string curly” (Tao et al., 2017). Variation in these traits affects the value of wool and lamb pelts in China. The genetic basis of these characteristics is currently unknown, hence the objective of this study was to characterize KRTAP6-1 in Chinese Tan sheep and investigate whether variation if present in the gene, affects wool traits of economic value in China.

Section snippets

Sheep investigated and wool traits recorded

Five hundred and twenty-nine Chinese Tan lambs from 23 sire-lines were investigated. The majority of the lambs were born as singles and only 14 of them were born as twins. These twins were removed from the association analyses and only the 515 single lambs were analysed.

As most rural Chinese wool and pelt producers do not have access to internationally standardised wool testing methods, they have devised and used their own methods to measure the wool traits that they are interested in and

Polymorphism of KRTAP6-1 in Chinese Tan sheep

SSCP analysis of PCR amplicons identified four alleles of KRTAP6-1 in the Chinese Tan sheep, including two previously identified variants (A and B) and two new variants (D and E) that have not been described previously (Fig. 1). Variant C (Zhou et al., 2015) was not found in these Tan sheep. Variant E was defined by a SNP that has not previously been described and was located upstream of the coding region. While variant D did not contain any new SNP, it had a sequence difference that appears to

Discussion

The identification of two additional variants of this gene takes the reported number of KRTAP6-1 variants from three to five, suggesting KRTAP6-1 is a polymorphic gene in sheep and confirming its effect on wool characteristics warrants further investigation.

Associations were revealed between variation in KRTAP6-1 and various wool traits of value in Chinese markets. At Er-mao, a longer straightened fibre-length, a higher crimp number and a higher degree of crimping were found to be associated

Conflict of interest statement

The authors have declared that no conflict of interest exists.

Acknowledgments

The financial support from the Lincoln University Gene-Marker Laboratory and the Ningxia Special Breeding Program are acknowledged. We thank the support of the AGMARDT Postdoctoral Fellowship to Hua Gong, and the technical support from Seung Byun and Qian Fang.

References (16)

There are more references available in the full text version of this article.

Cited by (20)

  • Skin transcriptome analysis identifies the key genes underlying fur development in Chinese Tan sheep in the birth and Er-mao periods

    2022, Gene
    Citation Excerpt :

    The Chinese Tan sheep, which is mainly distributed in Ningxia Province and adjacent areas, is one of the most important sheep breeds used for the production of high-quality fur (Kang et al., 2013) and famous worldwide for its meat, wool, and fur. Tan sheep fur, commonly known as Er-mao fur, is from the pelt of the lamb approximately 35 d after birth (which is traditionally called the age at Er-mao) (Tao et al., 2017). At this time, the fur is thin and soft with good thermal performance, and its wool is curved like waves; Chinese Tan sheep wool is thus said to “nine bay”.

  • Differentially phosphorylated proteins in the crimped and straight wool of Chinese Tan sheep

    2021, Journal of Proteomics
    Citation Excerpt :

    Four different crimp patterns have been described for Tan sheep wool, and these translate to ‘random curly’, ‘soft and big curly’, ‘Chinese string curly’ and ‘walnut flower curly’, with the last being the most popular in markets [2]. Despite there having been some research investigating the genes that affect wool fibre traits in Tan sheep [1–4], little is known of what underpins the unique characteristics of Tan sheep wool. Tan sheep wool undergoes changes in crimp characteristics after Er-mao, with the crimp pattern becoming less well defined, and the value of the fur declining [2].

  • Variation in the ovine KAP8-1 gene affects wool fibre uniformity in Chinese Tan sheep

    2019, Small Ruminant Research
    Citation Excerpt :

    Recently studies have suggested that variation in KAP genes affects wool crimping and growth in the early life of Tan sheep. Tao et al. (2017a) reported that variation in KRTAP6-1 was associated with straightened fibre-length (when the fibre is put under sufficient tension to remove the crimp pattern) at birth and at Er-mao, and with crimp number and degree of crimping in the fine wool fibres at Er-mao. Variation in KRTAP8-2 has been associated with straightened fibre-length and the degree of crimping in the fine fibres at Er-mao (Tao et al., 2017b).

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

    2019, Molecular Phylogenetics and Evolution
    Citation Excerpt :

    The KRTAPs are intron-less genes, with small coding sequences of less than 1 kb in length) (Rogers and Schweizer, 2005; Gong et al., 2016; Stein, 2004; Torrents et al., 2003). In addition, the KRTAPs show high levels of population variation, with all known KRTAP genes being polymorphic in sheep (Gong et al., 2016, 2010b; Zhou et al., 2016), where they are well studied because of their roles in determining wool phenotypes (Li et al., 2017a, 2017b, 2017c; Tao et al., 2017a, 2017b; Zhou et al., 2015). Despite this variation, it has been reported that some KRTAP genes show a pattern of concerted evolution between the paralogous gene copies (Khan et al., 2014; Rogers et al., 1994; Wu et al., 2008).

  • A keratin-associated protein (KAP) gene that is associated with variation in cashmere goat fleece weight

    2018, Small Ruminant Research
    Citation Excerpt :

    In goats only eleven KRTAPs from eight families have been described (Wang et al., 2017a), with sequence variation in three (KRTAP13-1, KRTAP8-2 and KRTAP20-2), being reported to be associated with cashmere quantity and quality traits (Fang et al., 2010; Liu et al., 2007; Wang et al., 2017a respectively). Contrastingly in sheep; associations between variation in fibre traits and variation in KRTAPs have been described for KRTAP1-2 (Gong et al., 2015), KRTAP6-1 (Zhou et al., 2015; Tao et al., 2017b), KRTAP6-3 (Li et al., 2017b), KRTAP8-2 (Tao et al., 2017a), KRTAP22-1 (Li et al., 2017a) and KRTAP26-1 (Li et al., 2017c). The genetic similarity between sheep and goats suggests that more KRTAPs can be found in the caprine genome, and that if these genes contain sequence variation, then it might affect cashmere fibre traits.

View all citing articles on Scopus
View full text