Data from: Parent-of-origin growth effects and the evolution of hybrid inviability in dwarf hamsters

Mammalian hybrids often show abnormal growth, indicating that developmental inviability may play an important role in mammalian speciation. Yet, it is unclear if this recurrent phenotype reflects a common genetic basis. Here, we describe extreme parent-of-origin-dependent growth in hybrids from crosses between two species of dwarf hamsters, Phodopus campbelli and Phodopus sungorus. One cross type resulted in massive placental and embryonic overgrowth, severe developmental defects, and maternal death. Embryos from the reciprocal cross were viable and normal sized, but adult hybrid males were relatively small. These effects are strikingly similar to patterns from several other mammalian hybrids. Using comparative sequence data from dwarf hamsters and several other hybridizing mammals, we argue that extreme hybrid growth can contribute to reproductive isolation during the early stages of species divergence. Next, we tested if abnormal growth in hybrid hamsters was associated with disrupted genomic imprinting. We found no association between imprinting status at several candidate genes and hybrid growth, though two interacting genes involved in embryonic growth did show reduced expression in overgrown hybrids. Collectively, our study indicates that growth-related hybrid inviability may play an important role in mammalian speciation but that the genetic underpinnings of these phenotypes remain unresolved.

哺乳动物杂交后代常出现生长异常，这表明发育不可存活性可能在哺乳动物物种形成过程中发挥重要作用。然而，这种反复出现的表型是否存在共同的遗传基础，目前仍不明确。本研究报道了坎贝尔侏儒仓鼠（Phodopus campbelli）与草原侏儒仓鼠（Phodopus sungorus）杂交后代中出现的极端亲本起源依赖性生长表型。其中一种杂交组合的后代会出现严重的胎盘与胚胎过度生长、严重发育缺陷，甚至导致母本死亡；反交组合的胚胎则可正常存活且体型正常，但成年杂交雄性个体体型相对偏小。这些表型与其他数种哺乳动物杂交后代的相关模式极为相似。利用侏儒仓鼠及其他数种杂交哺乳动物的比较序列数据，本研究认为极端杂交生长表型可在物种分化早期推动生殖隔离的形成。随后，本研究检测了杂交仓鼠的生长异常是否与基因组印记（genomic imprinting）紊乱相关。尽管在过度生长的杂交后代中，两个参与胚胎生长的互作基因的表达量出现下调，但本研究并未发现多个候选基因的印记状态与杂交生长异常存在关联。综上，本研究表明与生长相关的杂交不可存活性可能在哺乳动物物种形成中发挥重要作用，但此类表型的遗传基础仍有待进一步阐明。