A BAC contig map over the proximal ∼3.3 Mb region of horse chromosome 21

Abstract

A total of 207 BAC clones containing 155 loci were isolated and arranged into a map of linearly ordered overlapping clones over the proximal part of horse chromosome 21 (ECA21), which corresponds to the proximal half of the short arm of human chromosome 19 (HSA19p) and part of HSA5. The clones form two contigs – each corresponding to the respective human chromosomes – that are estimated to be separated by a gap of ∼200 kb. Of the 155 markers present in the two contigs, 141 (33 genes and 108 STS) were generated and mapped in this study. The BACs provide a 4–5× coverage of the region and span an estimated length of ∼3.3 Mb. The region presently contains one mapped marker per 22 kb on average, which represents a major improvement over the previous resolution of one marker per 380 kb obtained through the generation of a dense RH map for this segment. Dual color fluorescence in situ hybridization on metaphase and interphase chromosomes verified the relative order of some of the BACs and helped to orient them accurately in the contigs. Despite having similar gene order and content, the equine region covered by the contigs appears to be distinctly smaller than the corresponding region in human (3.3 Mb vs. 5.5–6 Mb) because the latter harbors a host of repetitive elements and gene families unique to humans/primates. Considering limited representation of the region in the latest version of the horse whole genome sequence EquCab2, the dense map developed in this study will prove useful for the assembly and annotation of the sequence data on ECA21 and will be instrumental in rapid search and isolation of candidate genes for traits mapped to this region.

Progress on horse genome project

“…101 个RH组, 分布于马的所有常染色体和X染色体 上 [20] 。Coleman等 [21] 利用RH图谱在ECA 17 确定 162 个表达序列标签(Expressed sequence tags, ESTs), 在 ECA X上确定 382 个表达序列标签。 Momozawa等 [22] [23] 报道了一个高 密度的马 22 号染色体的图谱, 其中包括 52 个特定 基因和 31 个微卫星标记。Wagner等 [24] [25] 。有效的BAC文库的出现使马 科学研究者可以初步发展涵盖马基因组较少区域的 BAC重叠群, 并且开发完整的马全基因组BAC重叠 群物理图谱。Boneker等 [26] 分离得到位于马染色体 2p16→p15 的COL9A2 基因的BAC克隆。Dierks等 [27] 从ECA 4q12-q22 区域的马BAC克隆中找出 29 个基 因关联的序列标记位点(Sequence tagged site, STS)。 Brinkmeyer-Langford等 [28]…”