Fujiwara A, Abe S, Yamaha E, Yamazaki F, Yoshida M C
Laboratory of Cytogenetics, Graduate School of Environmental Earth Science, Hokkaido University, Sapporo 060, Japan.
Chromosoma. 1997 Jun;106(1):44-52. doi: 10.1007/s004120050223.
Chromosome elimination through chromosome loss and partial deletion is known to be one of the causes of embryonic inviability in some salmonid interspecific hybrids. Using fluorescence in situ hybridization and related techniques, including whole chromosome painting and comparative genomic hybridization, parental origin of eliminated chromosomes was identified in the inviable hybrids between masu salmon (Ms, Oncorhynchus masou) female and rainbow trout (Rb, O. mykiss) male at the early embryonic stage prior to death. In these hybrids, the haploid Rb chromosome number decreased to nearly half, whereas the Ms chromosomes were retained as one or occasionally two full haploid complements. The Rb chromosomes were also involved in the frequently observed fragments and micronuclei. Whereas the occurrence of fragments was constant throughout the observed period, chromosome loss occurred mainly from just after fertilization to the blastulae stage. In tissue sections and cell spreads of late blastula, some Rb chromosomes were trapped in the midzone from ana- to telophase, resulting in micronuclei at the subsequent interphase. Micronuclei and mitotic abnormalities were also observed in the androgenetic haploid hybrids. However, such abnormalities were seldom or never observed in the viable reciprocal hybrids. The present findings suggest that the paternal Rb chromosomes in the inviable hybrids are preferentially eliminated through mitotic abnormalities during early embryogenesis, owing to a possible incompatibility between the maternal Ms cytoplasm and paternal Rb genome.
通过染色体丢失和部分缺失导致的染色体消除是一些鲑科种间杂种胚胎致死的原因之一。利用荧光原位杂交及相关技术，包括全染色体涂染和比较基因组杂交，在死亡前的早期胚胎阶段，对马苏大麻哈鱼（Ms，Oncorhynchus masou）雌鱼和虹鳟（Rb，O. mykiss）雄鱼杂交产生的不可存活杂种中被消除染色体的亲本来源进行了鉴定。在这些杂种中，单倍体Rb染色体数量减少到近一半，而Ms染色体则保留为一个或偶尔两个完整的单倍体组。Rb染色体也参与了频繁观察到的片段和微核的形成。在整个观察期内，片段的出现是恒定的，而染色体丢失主要发生在受精后到囊胚期。在晚期囊胚的组织切片和细胞铺片中，一些Rb染色体在有丝分裂的后期到末期被困在中间区，导致随后间期出现微核。在雄核发育单倍体杂种中也观察到了微核和有丝分裂异常。然而，在可存活的反交杂种中很少或从未观察到这种异常。目前的研究结果表明，由于母本Ms细胞质与父本Rb基因组之间可能存在不相容性，不可存活杂种中的父本Rb染色体在胚胎早期发育过程中通过有丝分裂异常被优先消除。
