Studies on the Mechanism of Genetic Control for Fat Depositon in Cattle

脂肪沉积的遗传和环境控制对牛肉生产非常重要。为了研究脂肪沉积的遗传机制，采用分子遗传学和统计遗传学的方法，克隆了牛C/EBPα、C/EBPβ、C/EBP Delta和PPAR Gamma2基因，并对其进行了序列分析。这些基因与小鼠的基因有很高的相似性。对牛C/EBPα基因启动子的分析表明，C/EBP结合序列和USF结合序列在牛中并不保守，提示牛C/EBPα基因表达调控机制不同。这些特征在牛C/EBPα启动子中在日本黑牛和日本棕牛之间是保守的。此外，我们还克隆了牛ob基因，用统计分析的方法研究了多少个基因座对牛肉大理石纹有影响，以及受这一性状影响的主基因是否存在。熊本县日本褐牛群体中存在对大理石花纹有较大影响的分离主效基因。在该群体中的一些家系中也检测到了分离主基因。本研究表明，分子遗传学和统计遗传学相结合的方法是阐明脂肪沉积遗传机制的有力工具。

Genetic and environmental controls of fat deposition are important for beef production. To study the genetic mechanism of fat deposition, molecular genetics and statistical genetics were adopted.With the molecular genetics approach, bovine C/EBP alpha, C/EBP beta, C/EBP delta and PPAR gamma2 genes, that encode transcription factors regulating the adipocyte differentiation, were cloned and sequenced. These genes have the high similarities with the mouse genes. The analysis of bovine C/EBP alpha promoter revealed that C/EBP binding and USF binbing sequences, which were important elements of C/EBP alpha gene regulation in mouse and human, were not conserved in cattle, suggesting different mechanism for regulation of bovine C/EBP alpha gene expression. These features in bovine C/EBP alpha promoter were conserved between Japanese Black and Japanese Brown cattles. Moreover, bovine ob gene was cloned.With the statistical gentetic approach, we investigated how many loci affected the marbling in beef and also whether major gene affected by this trait is present or not. The presence of segregating major gene which has large effect on marbling was expected in Japanese Brown cattle population of Kumamoto Prefecture. Segregating major gene was also detected in some families within that population. Then, this approach is expected as the clue of quantitative trait loci (QTL) analysis with genetic marker.It is revealed from this study that the joint approach with both molecular and statistical genetics is a very powerful tool to elucidate the genetic mechanism of fat deposition.