Histone H3 lysine 9 acetylation pattern suggests that X and B chromosomes are silenced during entire male meiosis in a grasshopper

Abstract

The facultative heterochromatic X chromosome in leptotene spermatocytes of the grasshopper Eyprepocnemis plorans showed marked hypoacetylation for lysine 9 in the H3 histone (H3-K9) with no sign of histone H2AX phosphorylation. Since H3-K9 hypoacetylation precedes the meiotic appearance of phosphorylated H2AX (γ-H2AX), which marks the beginning of recombinational DNA double-strand breaks (DSBs), it seems that meiotic sex-chromosome inactivation (MSCI) in this grasshopper occurs prior to the beginning of recombination and hence synapsis (which in this species begins later than recombination). In addition, all constitutively heterochromatic chromosome regions harbouring a 180-bp tandem-repeat DNA and rDNA (B chromosomes and pericentromeric regions of A chromosomes) were H3-K9 hypoacetylated at early leptotene even though they will synapse at subsequent stages. This also suggests that meiotic silencing in this grasshopper might be independent of synapsis. The H3-K9 hypoacetylated state of facultative and constitutive heterochromatin persisted during subsequent meiotic stages and was even apparent in round spermatids. Finally, the fact that B chromosomes are differentially hypoacetylated in testis and embryo interphase cells suggests that they might be silenced early in development and remain this way for most (or all) life-cycle stages.

Phosphorylation of Histone H3S10 in Animal Chromosomes: Is There a Uniform Pattern?

“…Phosphorylation and acetylation of histones are posttranslational modifications often acting synergistically [Novak and Corces, 2004]. Accordingly, H3K9 hypoacetylation has been observed in mice X chromosomes and in grasshopper X and B chromosomes associated with the phenomenon of meiotic silencing [Cabrero et al, 2007]. Our results suggest that H3S10 hypophosphorylation may also play a role in meiotic silencing in X and m chromosomes.…”

B-Chromosome Ribosomal DNA Is Functional in the Grasshopper Eyprepocnemis plorans

“…In E. plorans , the NOR activity observed by Cabrero et al [36] in the B 2 chromosome fused to the longest autosome was later shown to be related with undermethylation of the rDNA [40]. In addition, it has been shown that B chromosomes in this species are hypoacetylated for lysine 9 in the H3 histone [41].…”

Comparative Transcriptomics of Malaria Mosquito Testes: Function, Evolution, and Linkage

“…This phenomenon has been observed in diverse eukaryotes, including mammals (Richler et al 1992), grasshoppers (Cabrero et al 2007), and nematodes (Kelly et al 2002). Indeed, Magnusson et al (2012) showed than when active autosome testes promoters are placed onto the A. gambiae X, they largely fail to drive expression.…”