Meiosis in Hybrids: Looking for the Order in Disorder

The study of gametogenesis in hybrids between intraspecific chromosomal forms or distinct species is mainly aimed at identifying the successful outcome of the process to produce balanced, viable gametes. At the same time, deviations from typical meiotic progression patterns may provide a pivotal mechanism for speciation.

The long history of studying the process of gametogenesis and the development of methodological approaches have helped clarify the cytological and molecular processes that occur during meiosis. Since the early 1980s, Prof. Oxana Kolomiets has been studying meiosis in various species, including mole voles Ellobius, with a focus on chromosome synapsis and other key events during prophase I. Research on hybrids from different chromosomal forms of mole voles has uncovered notable differences in how meiosis progresses and its impact on fertility. In cases where Robertsonian translocations exhibit incomplete homology, various chromosomal multivalents form during prophase I. These configurations are often so complex that the chance of producing balanced gametes appears minimal. Moreover, there were also variations in the formation of trivalents. These discrepancies are thought to arise due to the involvement of distinct chromosomes in Robertsonian translocations, which lead to alterations in the spatial structure of the nucleus. Autosomes and sex chromosomes can exhibit disparities in trajectories of movement, synapsis, and recombination in meiosis. These disparities manifest most distinctly in hybrids, where atypical interchromosomal interactions, including those between sex chromosomes and autosomes, occur. Such interactions are absent in normal meiocytes, highlighting the altered meiotic processes in hybrids.

Chromosomal rearrangements, such as Robertsonian translocations, neocentromeres, and dicentric chromosomes, alter nuclear architecture, leading to meiotic irregularities that disrupt the progression of meiosis and gametogenesis. Meiotic irregularities cause variation in hybrid fertility. The analysis of meiosis I prophase turns out to be highly efficient for understanding the mechanisms of speciation.