Molecular Mechanism of Fat Deposition in Beef Cattle

本研究采用分子遗传学和统计遗传学相结合的方法，对牛组织中脂肪形成的分子机制，特别是日本黑牛肌肉内脂肪积累的特点进行了研究，并利用分子遗传学的方法分离了与脂肪细胞分化和脂肪积累调控相关的牛基因，分析了这些基因的表达和功能调控系统。此外，我们还研究了检测其基因在牛背最长肌组织中表达的方法。对肥育前后牛脂肪组织中基因表达的鉴定导致分离出这些基因，这些基因在肥育的脂肪组织中表达上调。克隆了前脂肪细胞特异表达的Pref-1的两个亚型。制备了抗Pref-1重组蛋白的抗血清，有望作为脂肪细胞di…早期过程的标志物对C/EBP家族和PPARg有更多的区分。用免疫组织化学方法检测了这些可能的标志物在牛背最长肌组织中的表达。此外，我们还分离了瘦素基因，瘦素基因是维持脂肪持续储存的反馈环的一部分，基因转染实验表明瘦素基因的表达受到C/EBP转录因子的激活。模拟研究表明，群体中主基因的存在取决于主基因的方差估计是否与零有显着差异。将该检测方法应用于日本黑牛群体屠体性状的实际记录，表明大理石花纹和皮下脂肪厚度性状存在主效基因，支持该检测方法的实用性。结合分子遗传学和统计遗传分析的研究结果，这两种研究方法的结合将为育种改良开辟一条新的途径。因此，我们相信，这项研究资助将有助于获得大量基础知识，为开发新的育种方法提供帮助。较少

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