Molecular Mechanism of Fat Deposition in Beef Cattle

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In this study, we have performed both molecular genetic and statistical genetic analyses, in order to elucidate molecular mechanism underlying adipogenesis in bovine tissues, particularly, intramuscular fat accumulation characteristic of Japanese Black Cattle.Using molecular genetic approach, we have isolated the bovine genes responsible for adipocyte differentiation and regulation of fat accumulation, and analyzed regulation system for expression and function of their genes. Furthermore, we have examined the method to detect expression of their genes in bovine longissimus muscle tissue. Characterization of gene expression in bovine adipose tissue before and after fattening resulted in isolation of the genes, of which expression is upregulated in fattened adipose tissue. Two isoforms of Pref-1, expressed specifically in preadipocyte, were isolated as cDNA clones. Antisera against recombinant proteins of Pref-1 were produced, which is expected as marker for early process of adipocyte di … More fferentiation as well as C/EBP family and PPARg. Expression of these possible markers in bovine longissimus muscle tissue was examined with immunohistochemical approach using the antisera. Moreover, we isolated the gene for leptin, which acts as part of a feedback loop to maintain constant stores of fat, and gene transfection experiment revealed that expression of leptin gene is activated by C/EBP transcription factor.Using statistical genetic approach, we have established the method for detection of major genes responsible for quantitative trait, which is based on Bayes estimation of mixed inheritance model with Gibbs sampling. Simulation study indicated that existence of major genes in population is dependent on whether estimation of variance of major genes differ significantly from zero. Application of this detection method to actual records of carcass traits in population of Japanese Black Cattle suggested existence of major genes responsible for marbling and subcutaneous fat thickness traits, supporting usefulness of the detection method.Considering the research results of both molecular genetic and statistical genetic analyses, combination of the two research approach will open up an novel way of breeding improvement. Thus, we believe that this research grant is helpful for obtaining a large number of underlying knowledge for development of new breeding methods. Less