Results and Discussion
Genetic Variants
A 500 bp PCR product for the CAST1 locus was observed, which was the same size as the PCR product from ovine (Roberts et al., 1996). Single strand conformation polymorphism analysis detected genetic variants for the CAST1 locus; two alleles (A and B) were observed (Figure 1). A 1,600 bp PCR product was generated using the CAPN4L4 locus; genetic variants were observed with Hha I restriction enzyme (Figure 2). Allele frequencies were calculated as 0.27 and 0.73 for the A and B allele of CAST1, and 0.67 and 0.33 for the A and B allele of CAPN4L4, respectively.
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| Figure 1. The PCR-SSCP polymorphism in domain L of the bovine CAST1 locus, demonstrating three genotypes (AA, AB, and BB). the SSCP was conducted at 10OC for 14 hours using 0.5 X mutation detection enhancement (MDE) gels. | Figure 2. The PCR-RFLP polymorphism for CAPN4L4 locus of bovine calpain IV after digestion with Hha I at 37OC for 3 hours, demonstrating three genotypes (AA, AB, and BB). |
Effects of Genotypes
Statistical significance was observed for the effects of the CAST1 genotypes on ONW, W56, and OFW (Tables 1 and 2). The CAPN4L4 genotypes had a significant effect on WW (Table 1). The CAST1 genotypes explained some variation in W28 (P = 0.09) and W42 (P = 0.06). Least significant differences were observed for ONW at the CAST1 locus. The least squares mean of the BB genotype (215.02 kg) was significantly different from that of the AA (205.43 kg) and AB (212.78 kg) genotypes. Least significant differences for W56 were also observed at the CAST1 locus with the BB genotype having the highest mean. The BB CAST1 genotype tended to have the highest mean for all of the weight traits. This genotype may be a good marker to use in marker assisted selection programs. At the CAPN4L4 locus, least significant differences were observed for WW. The least squares mean of the AA genotype was significantly different from the means of the other genotypes.
According to Cottin et al. (1994), the calpain system was detected in the early cell culture growth stage, and interacted with IGF-I. The calpain system may be a cofactor for increasing muscle differentiation. Barnoy et al. (1999) and Hitomi et al. (2000) also suggested that the calpain system is associated with the initial stages of cell differentiation. Therefore, the calpain system may be involved in the process of growth at early embryonic developmental stages or late skeletal muscle developmental stages. Genetic variants of CAST1 in this study accounted for some variation in weight and also tended to be associated with postweaning growth. The CAST1 genotypes tended to influence IGF56 (P = 0.08), but no significant effects on IGF-I traits were found for either locus (Table 3).
Conclusions
Least significant differences among CAST1 genotypes were found for ONW (BB>AB>AA), W56 (BB>AB>AA), and OFW (BB>AB>AA). However, no significant differences for weight traits other than WW were observed among CAPN4L4 genotypes. Neither CAST1 nor CAPN4L4 genotypes influenced IGF-I concentration. These results imply that calpain and calpastatin genotypes explain some variation in weight, and that the calpain and calpastatin genotypes may be used in marker assisted selection programs.