SETDB1 Links the Meiotic DNA Damage Response to Sex Chromosome Silencing in Mice

Abstract

SummaryMeiotic synapsis and recombination ensure correct homologous segregation and genetic diversity. Asynapsed homologs are transcriptionally inactivated by meiotic silencing, which serves a surveillance function and in males drives meiotic sex chromosome inactivation. Silencing depends on the DNA damage response (DDR) network, but how DDR proteins engage repressive chromatin marks is unknown. We identify the histone H3-lysine-9 methyltransferase SETDB1 as the bridge linking the DDR to silencing in male mice. At the onset of silencing, X chromosome H3K9 trimethylation (H3K9me3) enrichment is downstream of DDR factors. Without Setdb1, the X chromosome accrues DDR proteins but not H3K9me3. Consequently, sex chromosome remodeling and silencing fail, causing germ cell apoptosis. Our data implicate TRIM28 in linking the DDR to SETDB1 and uncover additional factors with putative meiotic XY-silencing functions. Furthermore, we show that SETDB1 imposes timely expression of meiotic and post-meiotic genes. Setdb1 thus unites the DDR network, asynapsis, and meiotic chromosome silencing.

Detailed profiles of histone modification in male germ line cells of the young and aged mice

“…In this study, we confirmed accumulation of H3K79me3 on the sex chromosomes in spermatocytes at M phase. A similar localization of H3K9me3 has been shown in a previous study [27]. Moreover, H3K27ac was accumulated on XY body and sex chromosomes in spermatocytes and in round spermatids, respectively.…”

“…Those dotted signals matched with intense DAPI signals, indicating heterochroma tin areas. Consistent with a previous report [27], H3K9me3 exceptionally localized on the sex chromosome of M-phase spermatocytes at stage XII ( Fig. 6a, arrowhead 8).…”

“…At the pachytene stage of meiosis I, genes on sex chromosomes are transcriptionally shut down by meiotic sex chromosome inactiva tio n (MSCI), and reactivated after meiosis [29]. It is reported that H3K9me3 is involved in silencing of sex chromosomes in meiosis and that if there is no enrichment of H3K9me3, remodeling and silencing of sex chromosomes failed and cause germ cell apoptosis [27].…”

C. elegans BRC-1-BRD-1 functions at an early step of DSB processing and inhibits supernumerary crossovers during male meiosis

“…LU AND YU 2015). Accumulation of DNA damage response components are linked to the recruitment of SETDB1 methyltransferase for H3K9me3 enrichment and gene silencing (HIROTA et al 2018). While C. elegans ATR ortholog and to a lesser extent the related ATM checkpoint kinases are critical for targeting H3K9me2 to the hemizygous X chromosome in male germ cells, removal of BRC-1-BRD-1 had no effect on either the deposition of H3K9me2 or on gene silencing of the X chromosome (Fig 1), suggesting that BRC-1-BRD-1 does not mediate MSCI in C. elegans male meiosis.…”

“…The hemizygous X chromosome of C. elegans male germ cells undergoes modifications similar to the hemizygous regions of the X and Y of mammalian spermatocytes, including accumulation of repressive chromatin marks resulting in transcriptional silencing (KELLY et al 2002;REUBEN AND LIN 2002;BEAN et al 2004;MAINE 2010). A C. elegans SETBD1 histone methyltransferase, an ortholog of which has been shown to mediate MSCI in mammals (HIROTA et al 2018), and a small RNA pathway are important for silencing the X chromosome of male germ cells (SHE et al 2009;BESSLER et al 2010; CHECCHI AND ENGEBRECHT 2011). However, the role of many components required for MSCI in mammals, including the tumor suppressor E3 ubiquitin ligase BRCA1 and master checkpoint kinase ATR (TURNER et al 2004;ROYO et al 2013;BROERING et al 2014), have not been analyzed in C. elegans.…”