Vozdova Miluse, Fröhlich Jan, Kubickova Svatava, Sebestova Hana, Rubes Jiri
Veterinary Research Institute, Central European Institute of Technology, Brno, Czech Republic.
Cytogenet Genome Res. 2017;152(2):73-80. doi: 10.1159/000478684. Epub 2017 Jul 20.
Recently, the reticulated giraffe (G. reticulata) was identified as a distinct species, which emphasized the need for intensive research in this interesting animal. To shed light on the meiotic process as a source of biodiversity, we analysed the frequency and distribution of meiotic recombination in 2 reticulated giraffe males. We used immunofluorescence detection of synaptonemal complex protein (SYCP3), meiotic double strand breaks (DSB, marked as RAD51 foci) in leptonema, and crossovers (COs, as MLH1 foci) in pachynema. The mean number of autosomal MLH1 foci per cell (27), which resulted from a single, distally located MLH1 focus observed on most chromosome arms, is one of the lowest among mammalian species analysed so far. The CO/DSB conversion ratio was 0.32. The pseudoautosomal region was localised in the Xq and Yp termini by FISH and showed an MLH1 focus in 83% of the pachytene cells. Chromatin structures corresponding to the nucleolus organiser regions were observed in the pachytene spermatocytes. The results are discussed in the context of known data on meiosis in Cetartiodactyla, depicting that the variation in CO frequency among species of this taxonomic group is mostly associated with their diploid chromosome number.
最近，网纹长颈鹿（G. reticulata）被确认为一个独特的物种，这凸显了对这种有趣动物进行深入研究的必要性。为了阐明减数分裂过程作为生物多样性的一个来源，我们分析了2只网纹长颈鹿雄性个体减数分裂重组的频率和分布。我们使用免疫荧光检测联会复合体蛋白（SYCP3）、细线期的减数分裂双链断裂（DSB，标记为RAD51灶点）以及粗线期的交叉（COs，作为MLH1灶点）。每个细胞中常染色体MLH1灶点的平均数量（27个），这是由于在大多数染色体臂上观察到单个位于远端的MLH1灶点所致，是迄今为止分析的哺乳动物物种中最低的之一。CO/DSB转化率为0.32。通过荧光原位杂交（FISH）将假常染色体区域定位在Xq和Yp末端，并且在83%的粗线期细胞中显示有一个MLH1灶点。在粗线期精母细胞中观察到了与核仁组织区相对应的染色质结构。我们将在鲸偶蹄目减数分裂已知数据的背景下讨论这些结果，表明该分类群物种间CO频率的变化大多与其二倍体染色体数相关。
