Identification And Tissue Expression Of Novel Family Genes KRTAP And Their Effects On Cashmere Traits In Goats

Cashmere is one of the main products of goat industry Keratin-associated proteins(KAPs),encoded by KRTAP family genes,which are important structural proteins that determine the quality of cashmere fibers.The variation and expression of genes in this family are related to cashmere traits,but limited in cashmere yield.Longdong cashmere goats were used to explore the new genes of KRTAP family and analyzed their influence on cashmere mean fiber diameter(MFD),cashmere yield,fiber length using the method of PCR-SSCP,RT-qPCR and situ hybridized.By detecting the differential expression of KRTAP gene in goat skin tissue and the expression sites in hair follicles to explored the expression characteristics of KRTAP gene in goat cashmere and wool from the histomorphology.(1)A BLAST search were used to search for homology sequences in goat genome.There were total of five new members of KRTAPs were identified,including KRTAP6-2,KRTAP6-3,KRTAP22-2,KRTAP21-1 and KRTAP21-2.These five new genes are tentatively located on the caprine chromosome 1,and between KRTAP8-2 and KRTAP20-2.(2)The genetic characteristics of the six KRTAPs genes and their effects on cashmere are as follows:(1)PCR-SSCP analysis of KRTAP6-2 revealed five alleles(A to E)in 230 Longdong cashmere goats.Eleven SNPs including two non-synonymous SNPs in the coding sequence,a three-nucleotide sequence variation,and a 12-bp insertion were found among these five sequences.The present of alleles D was detected to be correlated to decreased MFD(p < 0.01),MFD with genotypes AD and BD was significantly lower than that of AA,AB,AC and BB(p < 0.01).(2)Six alleles(A to F)of KRTAP6-3 were revealed in 337 goats.Three SNPs including two non-synonymous SNPs in coding sequence,and a 45-bp deletion were found among these six sequences.The present of alleles C was detected to be correlated toreduce MFD(P﹤0.01),and MFD with AC genotype was higher than that of AA and AB genotype(P﹤0.05).(3)Three alleles(A to C)of KRTAP21-1were revealed in 245 goats.Eleven SNPs were found among these three alleles,with nine SNPs including five non-synonymous in the coding sequence.The present of alleles A can significantly reduce MFD(P﹤0.01).(4)Four alleles(A to D)of KRTAP21-2 were revealed in 356 goats.Eight SNPs including five non-synonymous in the coding sequence,a 45-bp insertion were found among these four sequences.The present of alleles D can significantly reduce MFD(P﹤0.01),and MFD with AD genotype was lower than that of AA,AB,AC,BB and BC genotype(P < 0.01).(5)Four alleles(A to D)of KRTAP22-2 were revealed in 348 goats.Four SNPs including two non-synonymous in the coding sequence,a 6-bp insertion were found among these four sequences.The present of alleles B can significantly increase MFD(P< 0.05),and MFD with AB genotype was significantly higher than that of AA and AC genotype(P< 0.01).(6)Three alleles(A to C)of KRTAP8-1 were revealed in 249 goats.Two synonymous SNPs were found among three alleles.The absent of variant B can significantly increase the cashmere weight(P<0.01).(3)In situ hybridization results showed that KRTAP6-3,KRTAP21-2 and KRTAP22-2 gene were strongly expressed in the cortex and inner root sheath of the primary and secondary hair follicles,as well as in the dermal papilla and hair matrix cells,in addition,KRTAP21-2 and KRTAP22-2 gene were also expressed in the medulla of primary hair follicles during the anagen stages,and the signal expression at the sites described above was weakened during the telogen stages.It demonstrated that KAP6-3,KAP21-2 and KAP22-2 were important structure proteins of wool and cashmere.In summary,five new KRTAPs members KRTAP6-2,KRTAP6-3,KRTAP22-2,KRTAP21-1 and KRTAP21-2 were identified in goat,and tentatively located on goat chromosome 1.These five genes and KRTAP8-1 gene have different effects on cashmere fiber diameter and cashmere yield,respectively,which can be used as molecular marker genes for cashmere traits.