MORECULAR GENETICAL INVESTIGATION AND DNA DIAGNOSTIC SYSTEM FOR BOVINE CHONDRODYSPLASTIC DWARFISM

本研究的目的是鉴定牛软骨发育不良侏儒症的基因，并建立该疾病的DNA诊断系统。据报道，遗传性软骨发育不良侏儒症发生在日本棕色牛的特定种群中。患病动物表现为四肢长骨软骨内成骨功能不足，无其他相关改变。通过调查患病动物的家系，揭示了一种常染色体隐性遗传特征。在本研究中，我们利用微卫星标记和来自商业畜群的患病动物的单父系半同胞家族（n=82），通过连锁分析绘制了该疾病的致病位点。连锁分析显示，bcd位点与牛6号染色体上的标记位点之间存在显著的连锁。bcd位点定位于微卫星标记BP7和BM9257之间。牛与人的遗传图谱比较表明，牛6号染色体大部分与人4号染色体4p16.3 ~ 4q25段同源。该片段涉及几个候选基因，包括负责人类软骨发育不全的FGFR3基因。为了确定牛6号染色体与人类4号染色体之间的确切关系，我们利用牛仓鼠辐射杂交面板进行了辐射杂交作图。由此构建了包含33个功能基因和32个微卫星标记的牛6号染色体辐射杂交图谱。将牛6号染色体与人4号染色体的辐射杂交图谱进行比较，发现人4号染色体与牛6号染色体对应的区域存在bcd位点。

The aim of the present study is to identify the gene responsible for bovine chondrodysplatic dwarfism and establish the DNA diagnosis system for the disease. A hereditary chondrodysplastic dwarfism has been reported in the particular population of Japanese Brown cattle. Affected animal shows an insufficiency of endochondral ossification at long bones of the limbs and no other associated changes. An autosomal recessive trait of inheritance has been revealed by investigating pedigrees of the affected animals.In the present study, we mapped the locus responsible for the disease by linkage analysis using microsatellite markers and a single paternal half-sib family (n=82) of affected animals obtained from commercial herds. The linkage analysis revealed a significant linkage between the locus, referred as bcd, and marker loci on bovine Chromosome 6. The bcd locus was mapped between microsatellite markers BP7 and BM9257. A comparison of genetic maps between bovine and human indicates that the majority of bovine chromosome 6 is homologous to the segment of human chromosome 4 between 4p16.3 to 4q25. The segment involves several candidate genes including FGFR3 gene which is responsible for human achondroplasia. To determine exact relation between bovine chromosome 6 and human chromosome 4, we performed radiation hybrid mapping using the bovine hamster radiation hybrid panel. Consequently, a comprehensive radiation hybrid map of bovine chromosome 6 consisting with 33 functional genes and 32 microsatellite markers was constructed. A comparison between the radiation hybrid map of bovine chromosome 6 and human chromosome 4 revealed the region of human chromosome 4 corresponding to the region of bovine chromosome 6 in which the bcd locus is localized.