Guo J, Du L-X, Ma Y-H, Guan W-J, Li H-B, Zhao Q-J, Li X, Rao S-Q
Division of Animal Resources and Conservation, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100094, China.
Anim Genet. 2005 Aug;36(4):331-6. doi: 10.1111/j.1365-2052.2005.01310.x.
It is generally believed that domestic sheep have two maternal lineages (haplotypes A and B), based on mitochondrial DNA analysis. In the present study, we provide evidence that a novel maternal lineage (haplotype C) is exhibited in Chinese native sheep. To verify this finding, 231 samples were collected from six Chinese local breeds, which cover the vast geographical region of sheep inhabitation in China. For comparison, 50 samples were collected from two Western breeds collected in China. Mitochondrial DNA was screened by PCR single-strand conformational polymorphism (SSCP), leading to the identification of novel band patterns in ND2 and ND4 genes in the Chinese breeds. Interestingly, mutations at the two loci were in strong linkage disequilibrium. Direct sequencing of the DNA fragments revealed a non-synonymous substitution in ND2. Furthermore, two synonymous mutations were identified by comparisons of the novel type (haplotype C) and the established types (haplotypes A and B). The entire mitochondrial control region for 55 samples was then sequenced to construct a phylogenetic tree and median joining network. Both the tree and network demonstrated a topology of three groups, which is in consistent with the SSCP analysis. Unlike Western breeds, Chinese breeds are composed mainly of haplotypes A and B, but with a small fraction of haplotype C. According to Fu's test and mismatch distribution, haplotype C has not been subject to a recent population expansion. Based on these results, we propose a novel origin for Chinese sheep.
基于线粒体DNA分析，一般认为家养绵羊有两个母系谱系（单倍型A和B）。在本研究中，我们提供证据表明中国本土绵羊呈现出一种新的母系谱系（单倍型C）。为验证这一发现，从六个中国地方品种收集了231个样本，这些品种覆盖了中国绵羊栖息的广大地理区域。作为比较，从在中国收集的两个西方品种中收集了50个样本。通过PCR单链构象多态性（SSCP）筛选线粒体DNA，在中国品种的ND2和ND4基因中鉴定出了新的条带模式。有趣的是，这两个位点的突变处于强连锁不平衡状态。对DNA片段进行直接测序，发现在ND2中有一个非同义替换。此外，通过比较新型（单倍型C）和已确定类型（单倍型A和B），鉴定出两个同义突变。然后对55个样本的整个线粒体控制区进行测序，以构建系统发育树和中介连接网络。树和网络都显示出三组的拓扑结构，这与SSCP分析一致。与西方品种不同，中国品种主要由单倍型A和B组成，但有一小部分单倍型C。根据Fu氏检验和错配分布，单倍型C最近没有经历群体扩张。基于这些结果，我们提出了中国绵羊的一个新起源。
