Correlations Between BMPR-IB, BMP15, GDF9,MC4R, And Cast Gene Polymorphisms And Mutton Productivity Indicators In Bayanbulak, German Mutton Merino, And Duolang Sheep

Sheep breeding involves in improving growth and reproductive characteristics. To date many genes have been found to control these traits. BMPR-IB, BMP15, and GDF9, have been found to be the major genes that influence sheep reproductive capacity. Melanocortin-4receptor (MC4R) is a G-protein coupled receptor expressed in the brain, predominantly in the hypothalamus where it controls food intake, energy homeostasis and body weight. Calpastatin (CAST), one member of calpains system, is a specific inhibitor of calpains and is believed to be involved in the degradation of myofibrillar proteins in post-mortem proteolysis through regulating calpain activity, and hence it is implicated in meat tenderization.Here we used ligase detection reaction (LDR) and bioinformatics techniques to investigate the polymorphisms of BMPR-IB, BMP15, and GDF9genes in Bayanbulak (including low and high yielding groups), German Mutton Merino, and Duolang sheep, and correlated the polymorphisms with litter size. The polymorphisms of MC4R and CAST gene in German Mutton Merino were also determined, hoping to find clues to the marker assisted selection (MAS) in sheep production. This study included two experiments:I One hundred ordinary Bayanbulak sheep having single lamb (Flock B),20special Bayanbulak sheep having more than one lamb (Flock A), German Mutton Merino with complete lambing record in Inner Mongolia, and Bazhou Duolang sheep were studied using LDR to detect10SNPs in BMPR-IB, BMP15, and GDF9. The loci included FecB in BMPR-IB, FecXI, FecXB, FecXL, FecXH, FecXG, and FecXR in BMP15, and G1, G8, and FecTT in GDF9. The polymorphisms of BMPR-IB, BMP15, and GDF9were then compared among ordinary Bayanbulak group, special Bayanbulak group, German Mutton Merino, and Duolang Sheep. An association of the SNPs with litter size was subsequently conducted. II Lambs of German Mutton Merino in Inner Mongolia with complete record of production performance (including birth weight, back-fat, eye muscle area and average daily gain) were studied using LDR to detect SNPs in MC4R gene and the second exon of the CAST gene. An association of the SNPs with growth trait and meat performance. The results were as follows:1Polymorphisms of BMPR-IB gene in Bayanbulak, German Mutton Merino, and Duolang sheep, and its association with litter sizePolymorphisms of BMPR-1B/FecB gene were found in the Bayanbulak sheep. The genotypic frequency of the wild type (Fec++), heterozygous type (FecB+), and mutant (FecBB) were0.15,0.7, and0.15in flock A, and1.0,0, and0in flock B, respectively. The corresponding genotype frequency of wild type and mutation type were0.5,0.5in flock A and1.0,0.0in flock B, respectively. The independence test results of flock A and B suggested that the FecB locus significantly affects the litter size in the Bayanbulak sheep. BMPR-IB/FecB can be considered as the major gene that determines litter size in Bayanbulak sheep. Accordingly, this genetic marker may be used to improve litter size through MAS. No polymorphism of BMPR-IB/FecB mutation was found in German Mutton Merino and Duolang sheep. Therefore, the BMPR-IB/FecB mutation may not be correlated with the reproductive performance in the German Mutton Merino and Duolang sheep.2Polymorphisms of BMP15gene in Bayanbulak, German Mutton Merino, and Duolang sheep, and its association with litter sizeNo polymorphism was detected at FecX-I、FecXB、FecXL、FecXH、FecX and FecXR of BMP15gene in the above three breeds. Therefore, the six loci of the BMP15gene cannot be used as a genetic marker for litter size in the three sheep breeds.3Polymorphisms of GDF9gene in Bayanbulak, German Mutton Merino, and Duolang sheep, and its relation to litter sizeThe G1mutation was detected in the GDF9gene of Bayanbulak and German Mutton Merino sheep. However, FecG (G8) and FecTT mutations were not detected in the two sheep breeds. The polymorphism of G1mutation was moderate, and the locus was within the Hardy-Weinberg equilibrium in the two groups. No association of GDF9polymorphisms with litter size was found. There was no SNP of GDF9gene in Duolang sheep. These results indicated that the three site of GDF9gene does not significantly influence litter size of Bayanbulak, German Mutton Merino, and Duolang sheep.4Polymorphisms of MC4R gene in German Mutton Merino and its association with meat performanceFour SNPs of MC4R gene were detected in German Mutton Merino sheep, namely, G309A, G508A, G1232A, and T1456C. All SNPs were within Hardy-Weinberg equilibrium. The SNP G1232A was moderate polymorphic, whereas the other three were slightly polymorphic. The sheep with AA type at G309A SNP had higher back fat than those with GG type (P<0.01). The back fat of sheep with AG type was higher than those with GG type (P<0.05). The eye muscle area and birth weight of AA sheep were higher than those of AG and GG sheep (P<0.05). Sheep with AA and AG genotype at the SNP G1232A had higher back fat than those with GG type (P<0.05). Average daily gain of AA genotype sheep was higher than that of GG genotypes (P<0.05). These findings indicated that the MC4R gene might be the QTL that influences production traits or it is linkage to the QTL that controls the traits. The markers may be applied in the MAS.5Polymorphisms of CAST gene in German Mutton Merino and its association with meat performanceSeven SNPs of CAST gene were found in German Mutton Merino, namely, CAST3-1, CAST3-2, CAST3-3, CAST3-4, CAST7-1, CAST7-2, and CAST7-3. The statistical results showed that CAST3-2, CAST3-3, and CAST7-1were moderately polymorphic, whereas the other four SNPs were slightly polymorphic. The seven SNPs, however, were not significantly correlated to birth weight, average daily gain, back fat, eye muscle area. Further studies should be focused on find association of these SNPs with other production characteristcs.