Biology subjects

Menon, D. U.

Publications and source records attributed to Menon, D. U..

4 recordsLinked to original sources

bioRxiv2023

ARID1A governs the silencing of sex-linked transcription during male meiosis in the mouse

We present evidence implicating the BAF (BRG1/BRM Associated Factor) chromatin remodeler in meiotic sex chromosome inactivation (MSCI). By immunofluorescence (IF), the putative BAF DNA binding subunit, ARID1A (AT-rich Interaction Domain 1a), appeared enriched on the male sex chromosomes during diplonema of meiosis I. Those germ cells showing a Cre-induced loss of ARID1A were arrested in pachynema and failed to repress sex-linked genes, indicating a defective MSCI. Consistent with this defect, mutant sex chromosomes displayed an abnormal presence of elongating RNA polymerase II coupled with an overall increase in chromatin accessibility detectable by ATAC-seq. By investigating potential mechanisms underlying these anomalies, we identified a role for ARID1A in promoting the preferential enrichment of the histone variant, H3.3, on the sex chromosomes, a known hallmark of MSCI. Without ARID1A, the sex chromosomes appeared depleted of H3.3 at levels resembling autosomes. Higher resolution analyses by CUT&RUN revealed shifts in sex-linked H3.3 associations from discrete intergenic sites and broader gene-body domains to promoters in response to the loss of ARID1A. Several sex-linked sites displayed ectopic H3.3 occupancy that did not co-localize with DMC1 (DNA Meiotic Recombinase 1). This observation suggests a requirement for ARID1A in DMC1 localization to the asynapsed sex chromatids. We conclude that ARID1A-directed H3.3 localization influences meiotic sex chromosome gene regulation and DNA repair.

developmental biology↗

bioRxiv2021

RBBP4 modulates gene activity through acetylation and methylation of histone H3 lysine 27

RBBP4 is a core subunit of polycomb repressive complex 2 (PRC2) and HDAC1/2-containing complexes, which are responsible for histone H3 lysine 27 (H3K27) methylation and deacetylation respectively. However, the mechanisms by which RBBP4 modulates the functions of these complexes remain largely unknown. We generated viable mouse embryonic stem cell lines with RBBP4 mutations that disturbed methylation and acetylation of H3K27 on target chromatin and found that RBBP4 is required for PRC2 assembly and H3K27me3 establishment on target chromatin. Moreover, in the absence of EED and SUZ12, RBBP4 maintained chromatin binding on PRC2 loci, suggesting that the pre-existence of RBBP4 on nucleosomes serves to recruit PRC2 to restore H3K27me3 on newly synthesized histones. As such, disruption of RBBP4 function led to dramatic changes in transcriptional profiles. In spite of the PRC2 association, we found that transcriptional changes were more closely tied to the deregulation of H3K27ac rather than H3K27me3 where increased levels of H3K27ac were found on numerous cis-regulatory elements, especially putative enhancers. These data suggest that RBBP4 controls acetylation levels by adjusting the activity of HDAC complexes. As histone methylation and acetylation have been implicated in cancer and neural disease, RBBP4 could serve as a potential target for disease treatment.

genomics↗

bioRxiv2020

Mammalian SWI/SNF chromatin remodeler is essential for reductional meiosis in males

BRG1, a catalytic subunit of the mammalian SWI/SNF nucleosome remodeler is essential for male meiosis1. In addition to BRG1, multiple subunits (~10-14) some of which are mutually exclusive, constitute biochemically distinct SWI/SNF subcomplexes, whose functions in gametogenesis remain unknown. Here, we identify a role for the PBAF (Polybromo - Brg1 Associated Factor) complex in the regulation of meiotic cell division. The germ cell-specific depletion of PBAF specific subunit, ARID2 resulted in a metaphase-I arrest. Arid2cKO metaphase-I spermatocytes displayed defects in chromosome organization and spindle assembly. Additionally, mutant centromeres were devoid of Polo-like kinase1 (PLK1), a known regulator of the spindle assembly checkpoint (SAC)2. The loss of PLK1 coincided with an abnormal chromosome-wide expansion of centromeric chromatin modifications such as Histone H3 threonine3 phosphorylation (H3T3P) and Histone H2A threonine120 phosphorylation (H2AT120P) that are critical for chromosome segregation3,4. Consistent with the known role of these histone modifications in chromosome passenger complex (CPC) recruitment, Arid2cKO metaphase-I chromosomes display defects in CPC association. We propose that ARID2 facilitates metaphase-I exit by regulating spindle assembly and centromeric chromatin.

cell biology↗

bioRxiv2018

Mammalian SWI/SNF collaborates with a polycomb-associated protein to regulate male germ line transcription in the mouse

A deficiency in BRG1, the catalytic subunit of the SWI/SNF chromatin remodeling complex, results in a meiotic arrest during spermatogenesis. Here, we explore the causative mechanisms. BRG1 is preferentially enriched at active promoters of genes essential for spermatogonial pluripotency and meiosis. In contrast, BRG1 is also associated with the repression of somatic genes. Chromatin accessibility at these target promoters is dependent upon BRG1. These results favor a model where BRG1 coordinates spermatogenic transcription to ensure meiotic progression. In spermatocytes, BRG1 interacts with SCML2, a testes specific PRC1 factor that is associated with the repression of somatic genes. We present evidence to suggest that BRG1 and SCML2 concordantly regulate genes during meiosis. Furthermore, BRG1 is required for the proper localization of SCML2 and its associated deubiquitinase, USP7, to the sex chromosomes during pachynema. SCML2 associated, mono ubiquitination of histone H2A lysine 119 (H2AK119ub1) and acetylation of histone lysine 27 (H3K27ac) are elevated in Brg1cKO testes. Coincidentally, the PRC1 ubiquitin ligase, RNF2 is activated while a histone H2A/H2B deubiquitinase, USP3 is repressed. Thus, BRG1 impacts the male epigenome by influencing the localization and expression of epigenetic modifiers. This mechanism highlights a novel paradigm of co-operativity between SWI/SNF and PRC1.\n\nSummary statementBRG1, a catalytic subunit of SWI/SNF chromatin remodeling complex, interacts with SCML2 (Sex comb on midleg-like 2), a polycomb repressive 1 (PRC1) factor, to regulate transcription during spermatogenesis. This represents a novel paradigm of SWI/SNF-PRC1 co-operation during gametogenesis.

developmental biology↗