| Myostatin is a new member of the TGF-p superfamily. It is specifically expressed in skeletal muscle cells and functions as a negative regulator of skeletal muscle growth. Leptin receptor is a member of type I cytokine receptor superfamily and plays an important role in fatty acid metabolism. This study was designed and aimed to identify the single nucleotide polymorphisms (SNPs) of both myostatin gene and leptin receptor gene in various breeds including Beijing Youji, Baierji, Shiqiza, Dwarf Yellow Chickens, Mini Yellow Chickens, Huiyang Huxuji, Recessive White Chickens, AA, Hyline Layer, Fat line (FL) and Leanness line (LL).The 17 pairs of primers for myostatin gene were designed based on the chicken genomic sequence. Five SNPs were identified in the chicken myostatin gene by PCR-SSCP and sequencing. Three of them were in the 5'-regulatory region and 2 were in the 3'-regulatory region of the myostatin gene in different chicken lines. The sequence data showed that one of the three SNPs localized in the 5'-regulatory region was due to 3 single point mutations (G304A, A322G, C334T, respectively), other two single point mutations were G167A and T177C, respectively. Two SNPs found in the 3'-regulatory region of the myostatin gene were A to T (7263) and A to G (6935). Population genetic analysis indicated that genotype frequency of the P60/P61 SNPs in Beijing youji was quite different from those of other tested chicken lines. Frequency of the BB genotype was very high (0.70) while the AA genotype was only 0.033 in Beijing youji population. The genotype frequency (P93/P94) was significantly different in the tested chicken lines (P<0.01). Frequency of the EE genotype in Beijing Youji was lower than those in the other lines, while frequency of the EE genotype in Baierji and Hyline Layer was higher than the others. Frequency of allele C (P80/P81) in nine breeds was higher than that of allele D. Frequency of genotype MM (P76/P77) was low, and that of MN was high in seven breeds.In addition, we investigated the association of the SNPs identified in the chicken myostatin gene with production traits in the F2 population derived from broilers crossing to Silky. The results indicated that AA birds had higher abdominal fat weight (AFW) (P<).05), abdominal fat percentage (AFP) and birth weight (BW) and breast muscle weight (BMW) of EF birds was higher than that of EE birds (PO.05). There were significant different between CC and DD birds on the breast muscle weight (P<0.05) and breast muscle percentages (P<0.01). These data suggest that SNPs identified in the myostatin gene could be used as agenetic marker for marker assisted selection on chicken growth traits.The myostatin cDNAs were also cloned from duck, goose, pigeon and quail skeletal muscle tissue and sequence analysis indicated that nucleotide acid homologies among the birds, between birds and mammalians and between birds and fishes were more than 92%, 80% and 60%, respectively. Amino acid similarities among the birds were 96%-98% and among birds and mammalians were 88-92%. The 5'-regulatory regions of the myostatin gene was also cloned and sequenced from duck (1323bp), goose (1328bp) and quail (1391bp). The nucleotide acid homology between chicken and duck, goose, quail are 62.3%, 69.2% and 76.6%, respectively. The TATA box and CCAAT box are respectively identified at -34bp and -77bp upon the putative transcription initial sites. Meanwhile, the phylogenetic tree of the different species depend on myostatin cDNA sequence was also depicted.Tissue specific expression of the myostatin gene was also investigated in duck, goose, pigeon and quail by Northern blot analysis. It was found that myostatin gene was specifically expressed in skeletal muscle.The primers for OBR exon 9 were designed based on chicken genomic sequence and the SNPs were detected by PCR-SSCP and sequence. One silence mutant SNPs (Cl 167A in cds) was found within all breeds. The results of population genetic analysis showed that the frequency of AA genotype in Beijing Youji was significantl... |
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