Genetic Variation And Expression Profile Of Bovine BMP8b Gene

Bone morphogenetic protein8b (BMP8b) belongs to the transforming growth factor β(TGF-β) superfamily, and it regulates various biological processes based on the emergingevidence, such as primordial germ cell (PGC) generation, bone metabolism, and so on. Lately,a new study in mouse shows that BMP8b is highly expressed in brown adipose tissues (BAT),and it can increase BAT thermogenesis. Also it displays a robust response to high-fat diet(HFD) with increasing4-fold expression in BAT. Moreover, Bmp8b-/-mice have impairedthermogenesis and are susceptible to diet-induced obesity, making BMP8b an importantregulator of energy balance. Consequently, it is reasonable to take BMP8b gene as a newcandidate for growth and development. To date, there have been few reports on bovineBMP8b. Here, to get some molecular markers for beef cattle breeding program, we detectedSNPs of bovine BMP8b and analyzed the association between SNPs and growth traits. Also,the mRNA expression pattern and bioinformatic characters of bovine BMP8b were analyzed,so as to increase our understanding of the physiological role of bovine BMP8b.1. Genetic variation of bovine BMP8b geneDNA pooling and forced PCR-RFLP were used for bovine BMP8b gene sequencing ofthree Chinese cattle breeds, including Qinchuan cattle, Jiaxia cattle and Chinese Holstein, intotal of800cattle. Five novel SNPs (g.-242C>T, g.2164C>T, g.2639T>C, g.2900C>G, andg.10817C>T) were revealed according to the sequencing results. Among these variants,g.-242C>T was in5′-flanking regulatory region, and g.2164C>T, g.2900C>G, andg.10817C>T were located at intron1,3,4, respectively. The g.2639T>C locus was located atexon3, which resulted in a silent mutation (91Asp>Asp). Genetic diversity, linkagedisequilibrium and haplotypes were analysed as well. However, the result showed there weregreat differences between the three cattle breeds. These differences might be partly attributedto the variations of genetic background and selection pressure.The association analysis showed that the g.-242C>T mutation had significant effects onchest breadth, body length and body weight of QC population and body height, chest girth, rump length and body weight of JX cattle(P <0.05), and TC genotype had negative effects ongrowth traits, so individuals with this genotype should be discarded; the g.2164C>T locus hadsignificant effects on body height, body length, body weight, hip width and rump length ofQC cattle and body weight of JX cattle(P <0.05), and CC and TC ones had betterperformance than TT ones, so individuals with TT genotype should be discarded as well;g.2639T>C locus had significant effects on body weight of QC population and hip width,rump length and body weight of JX cattle (P <0.05), and CC ones had better performancethan TT and TC ones, so individuals with CC genotype should be kept. However, there werenot significant effects on growth traits of both the two breeds in g.2900C>G and g.10817C>Tloci (P>0.05). In conclusion, g.-242C>T, g.2164C>T and g.2639T>C loci could be used asmolecular markers in early marker assisted selection.2. The expression profile of bovine BMP8b geneIn this study, qRT-PCR was used to reveal the expression profile of bovine BMP8b gene,including its spatial and temporal expression and the effects of dietary energy density andmutation on its mRNA expression level in subcutaneous white adipose tissue. The resultsshowed that the transcript expression of bovine BMP8b was extraordinarily high in whiteadipose tissue (WAT) compared with it in all other examined tissues (heart, liver, spleen, lung,kidney, stomach, intestine, muscle) and it rose with increasing dietary energy level (P <0.05)(A treatment:8.9MJ/kg, B treatment:10.4MJ/kg, C treatment:11.3MJ/kg), whichimplicated potential key role of bovine BMP8b in regulating white adipocyte development.We also found that BMP8b mutation affected its mRNA expression, i.e. individuals withg.-242C>T-TC genotype had a higher mRNA expression than g.-242C>T-CC individuals inWAT (P <0.05). Collectively, these findings possibly provided new insight into thephysiological role of bovine BMP8b in white adipocyte development.2. The bioinformatic characters of bovine BMP8bTo have a further understanding of its structure and function, we reveal the bioinformaticcharacters of bovine BMP8b, including the analysis of its properties and prediction ofphosphoric site, transmembrance helix, secondary structure, and so on. And the resultsindicated that the grand average of hydropathicity of bovine BMP8b was-0.365, so it mightclassed as hydrophilic protein; it had sufficient phosphoric sites; it had a inside-to-outsidetransmembrance helix from201thamino acid to223thamino acid; And there no signal peptidein bovine BMP8b; Among the secondary structures of bovine BMP8b, helix accounted for7.74%, β-strand accounted for21.89%, loop accounted for70.37%.