Drosophila Yemanuclein is a cohesin and synaptonemal complex associated protein

Abstract

Meiosis is characterized by two chromosome segregation rounds (meiosis I and II), which follow a single round of DNA replication, resulting in haploid genome formation. Chromosome reduction occurs at meiosis I. It relies on key structures, such as chiasmata, which are formed by repair of double-strand breaks (DSBs) between the homologous chromatids. In turn, to allow for segregation of homologs, chiasmata rely on the maintenance of sister chromatid cohesion. In most species, chiasma formation requires the prior synapsis of homologous chromosome axes, which is mediated by the synaptonemal complex, a tripartite proteinaceous structure specific to prophase I of meiosis. Yemanuclein (Yem) is a maternal factor that is crucial for sexual reproduction. It is required in the zygote for chromatin assembly of the male pronucleus, where it acts as a histone H3.3 chaperone in complex with Hira. We report here that Yem associates with the synaptonemal complex and the cohesin complex. A genetic interaction between yem 1 (V478E) and the Spo11 homolog mei-W68, modified a yem 1 dominant effect on crossover distribution, suggesting that Yem has an early role in meiotic recombination. This is further supported by the impact of yem mutations on DSB kinetics. A Hira mutation gave a similar effect, presumably through disruption of Hira-Yem complex.

Drosophilaenhancer-Gal4 lines show ectopic expression during development

“…It is plausible that this feature might reflect sex differences in chromatin structure at the LN2 locus or in the repertoire of binding transcription factors involved in sex determination. The speculations proposed here for the LN2 enhancer of Sxl would be akin to the genomic specializations described for general sex determination in plants and animals including Drosophila [43][44][45]. In any case, it seems that the mechanisms that underlie unstable enhancer expression are diverse but not unspecific.…”

Genetic background impacts the timing of synaptonemal complex breakdown in Drosophila melanogaster

“…Previous work with c(3)G 68 heterozygotes found no changes in recombination compared to wild-type controls (Miller 2020). However, c(3)G 1 heterozygotes have been reported to exhibit increased recombination in some genetic intervals (Hinton 1966;Meyer et al 2014). It is also possible that this variation in recombination phenotype may be the effect of minor variations in genetic background: Hinton assessed X chromosome recombination using different multiply marked X chromosomes and showed that recombination was not consistently altered in c(3)G 1 heterozygotes compared to controls when different X chromosomes were tested (Hinton 1966).…”