Department of Animal Sciences, Georg-August-University, Göttingen, Germany.
Center for Integrated Breeding Research, Georg-August-University, Göttingen, Germany.
Sci Rep. 2019 Nov 25;9(1):17492. doi: 10.1038/s41598-019-53901-z.
Examples of living sheep-goat hybrids are rare, mainly due to incorrect chromosome pairing, which is thought to be the main cause for species incompatibility. This case represents the first report of a buck-ewe hybrid and the first mammalian hybrid to be analyzed with next generation sequencing. The buck-ewe hybrid had an intermediate karyotype to the parental species, with 57 chromosomes. Analysis of the blood transcriptomes of the hybrid and both parents revealed that gene expression levels differed between the hybrid and its parents. This could be explained in part by age-dependent differences in gene expression. Contribution to the geep transcriptome was larger from the paternal, compared to the maternal, genome. Furthermore, imprinting patterns deviated considerably from what is known from other mammals. Potentially deleterious variants appeared to be compensated for by monoallelic expression of transcripts. Hence, the data imply that the buck-ewe hybrid compensated for the phylogenetic distance between the parental species by several mechanisms: adjustment of gene expression levels, adaptation to imprinting incompatibilities, and selective monoallelic expression of advantageous transcripts. This study offers a unique opportunity to gain insights into the transcriptome biology and regulation of a hybrid mammal.
活羊-山羊杂种的例子很少见，主要是由于染色体配对不正确，这被认为是物种不相容的主要原因。本案例代表了首例报道的公绵羊-母山羊杂种，并首次使用下一代测序技术对哺乳动物杂种进行分析。公绵羊-母山羊杂种的染色体组型为中间型，有 57 条染色体。对杂种及其双亲的血液转录组分析表明，杂种与其双亲的基因表达水平存在差异。这部分可以用基因表达的年龄依赖性差异来解释。与母本相比，来自父本的基因组对杂种的基因表达贡献更大。此外，印迹模式与其他哺乳动物的已知模式有很大差异。潜在的有害变异似乎通过单等位基因表达的转录物得到了补偿。因此，这些数据表明，公绵羊-母山羊杂种通过几种机制来补偿亲种之间的系统发育距离：调整基因表达水平、适应印迹不相容性，以及有利转录物的选择性单等位基因表达。本研究为深入了解杂种哺乳动物的转录组生物学和调控提供了独特的机会。
