Abstract
Heat shock 70 kDa protein 8 (HSPA8) and erb-b2 receptor tyrosine kinase 2 (ERBB2) were the promising candidates for milk protein concentration in dairy cattle revealed through previous RNA sequencing (RNA-Seq) study. The objective of this post-RNA-Seq study was to confirm genetic effects of HSPA8 and ERBB2 on milk protein concentration in a large Chinese Holstein population and to evaluate the genetic effects of both genes on other milk production traits. There were 2 single-nucleotide polymorphisms (SNPs) identified for HSPA8 and 11 SNPs for ERBB2 by sequencing 17 unrelated Chinese Holstein sires. The SNP-rs136632043 in HSPA8 had significant associations with all five milk production traits (p = 0.0086 to p < 0.0001), whereas SNP-rs132976221 was remarkably associated with three yield traits (p < 0.0001). Nine (ss1996900615, rs109017161, rs109122971, ss1996900614, rs110133654, rs109941438, rs110552983, rs133031530, and rs109763505) of 11 SNPs in ERBB2 were significantly associated with milk protein percentage (p = 0.0177 to p < 0.0001). A 12 Kb haplotype block was formed in ERBB2 and haplotype associations revealed similar effects on milk protein traits. Our findings confirmed the significant genetic effects of HSPA8 and ERBB2 on milk protein concentration and other milk production traits and SNP phenotypic variances above 1% may serve as genetic markers in dairy cattle breeding programs.
Highlights
Molecular selective breeding strategies have been widely applied in animal breeding to improve the important economic traits of livestock
Our initial RNA sequencing (RNA-Seq) study revealed that heat shock 70 kDa protein 8 (HSPA8) and erb-b2 receptor tyrosine kinase 2 (ERBB2) were candidate genes affecting milk protein traits in dairy cows [10]
Two single-nucleotide polymorphisms (SNPs) of rs136632043 and rs132976221 were identified for HSPA8 gene, with one located in the 30 regulatory region (30 -UTR) and the other located in the intron (Table 1)
Summary
Molecular selective breeding strategies have been widely applied in animal breeding to improve the important economic traits of livestock. Identification of key genes or causal variations for economic traits is prerequisite to perform molecular selective breeding strategies [1,2]. Milk protein concentration is an important index to evaluate the nutritional value in cow’s milk. Limited key genes or variations for milk protein concentration were found in dairy cattle [3,4,5,6,7,8,9]. Our initial RNA sequencing (RNA-Seq) study revealed that heat shock 70 kDa protein 8 (HSPA8) and erb-b2 receptor tyrosine kinase 2 (ERBB2) were candidate genes affecting milk protein traits in dairy cows [10].
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