Abstract
Fibroblast growth factor 5 (FGF5) gene, a member of fibroblast growth factor superfamily, plays significant roles in the regulation of the hair growth cycle during the development of mammalian hair follicles as well as the skeletal muscle development. In this study, DNA sequencing was used to scan the putative SNPs within the full-length of FGF5 gene, and SNPscan high-throughput technique was applied in the individual genotyping of 604 crossbred sheep. 10 SNPs were identified within FGF5 gene while five of them located in intron 1 could be genotyped, namely SNP1 (g. 105914953 G > A), SNP2 (g. 105922232 T > C), SNP3 (g. 105922244 A > G), SNP4 (g. 105922334 A > T) and SNP5 (g. 105922340 G > T). All these SNPs were in accord with the Hardy-Weinberg equilibrium (P > 0.05), and displayed the moderate polymorphism with PIC values ranging from 0.302 to 0.374. Thereafter, the correlation analysis between each SNP locus and economic traits including wool length, greasy wool weight and growth performance of sheep was systematically implemented. In our results, SNP1, SNP3, SNP4 and SNP5 were significantly associated with wool length, greasy wool weight and growth traits of SG sheep (P < 0.05); SNP1, SNP2, SNP3, and SNP4 were significantly correlated with wool length and growth traits of SSG sheep (P < 0.05). Meanwhile, our study revealed a strong linkage disequilibrium (LD) relationship among these SNPs (r2 > 0.33), except for SNP3 and SNP4 sites (r2 = 0.30). Combination genotype analysis showed that combination genotypes were significantly associated with mean fiber diameter of SG (P < 0.05), and body weight trait of SSG (P < 0.01). The above findings suggested that these SNP loci might affect economic traits synergistically and could be regarded as potential molecular markers for improving both wool production and growth performance of fine-wool sheep, which lay a molecular foundation for the breeding of fine dual-purpose sheep thereby accelerating the pace of sheep breeding.
Highlights
Sheep, as an important source of wool, mutton and milk production, is economically influential in the textile and meat industry
According to our DNA sequencing and sequence alignments results based on 604 sheep samples, 10 putative Single nucleotide polymorphism (SNP) were identified within Fibroblast growth factor 5 (FGF5) gene while only five of them could be genotyped, namely SNP1 (g. 105914953 G > A), SNP2 (g. 105922232 T > C), SNP3 (g. 105922244 A > G), SNP4 (g. 105922334 A > T) and SNP5 (g. 105922340 G > T)
Previous studies have well-documented that different gene mutations can be linked with each other thereby affecting the economic traits of animals, such as litter size and growth performance of goats (Wang et al, 2019, 2020). Since all these five SNP loci are significantly associated with the economic traits of sheep, is there a certain synergistic effect among them? Based on this assumption, this study further analyzed the linkage disequilibrium (LD) relationship among these loci and the results revealed that there might be a strong linkage disequilibrium relationship among the five SNPs (r2 > 0.33), and the r2 value between SNP3 and SNP4 was close to the threshold of strong linkage disequilibrium state (r2 = 0.30), suggesting that all these five SNPs might play a synergistic role in the selection and breeding of sheep with both fine wool traits and improved growth performance
Summary
As an important source of wool, mutton and milk production, is economically influential in the textile and meat industry. Merino sheep crossing with local alpine fine-wool sheep can breed an excellent dual-purpose sheep, with good fine wool length and growth performance. SG and SSG sheep varieties have demonstrated good adaptabilities to local climate, improves growth rate and undegraded wool quality. Both their wool production and growth traits still need to be further improved. Taking full advantages of the MAS method, the exploration of crucial candidate genes and genetic markers related with wool production as well as growth performance is essential for the improvement of SG and SSG sheep varieties
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