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Salzler HR, Vandadi V, Matera AG. Set2 and H3K36 regulate the Drosophila male X chromosome in a context-specific manner, independent from MSL complex spreading. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.03.592390. [PMID: 38766267 PMCID: PMC11100620 DOI: 10.1101/2024.05.03.592390] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2024]
Abstract
Dosage compensation in Drosophila involves upregulating male X-genes two-fold. This process is carried out by the MSL (male-specific lethal) complex, which binds high-affinity sites and spreads to surrounding genes. Current models of MSL spreading focus on interactions of MSL3 (male-specific lethal 3) with histone marks; in particular, Set2-dependent H3 lysine-36 trimethylation (H3K36me3). However, Set2 might affect DC via another target, or there could be redundancy between canonical H3.2 and variant H3.3 histones. Further, it is difficult to parse male-specific effects from those that are simply X-specific. To discriminate among these possibilities, we employed genomic approaches in H3K36 (residue) and Set2 (writer) mutants. The results confirm a role for Set2 in X-gene regulation, but show that expression trends in males are often mirrored in females. Instead of global male-specific reduction of X-genes in Set2/H3K36 mutants, the effects were heterogeneous. We identified cohorts of genes whose expression was significantly altered following loss of H3K36 or Set2, but the changes were in opposite directions, suggesting that H3K36me states have reciprocal functions. In contrast to H4K16R controls, analysis of combined H3.2K36R/H3.3K36R mutants neither showed consistent reduction in X-gene expression, nor any correlation with MSL3 binding. Examination of other developmental stages/tissues revealed additional layers of context-dependence. Our studies implicate BEAF-32 and other insulator proteins in Set2/H3K36-dependent regulation. Overall, the data are inconsistent with the prevailing model wherein H3K36me3 directly recruits the MSL complex. We propose that Set2 and H3K36 support DC indirectly, via processes that are utilized by MSL but common to both sexes.
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Affiliation(s)
- Harmony R. Salzler
- Integrative Program for Biological and Genome Sciences, University of North Carolina, Chapel Hill, NC, USA
| | - Vasudha Vandadi
- Integrative Program for Biological and Genome Sciences, University of North Carolina, Chapel Hill, NC, USA
| | - A. Gregory Matera
- Integrative Program for Biological and Genome Sciences, University of North Carolina, Chapel Hill, NC, USA
- Department of Genetics, University of North Carolina, Chapel Hill, NC, USA
- Department of Biology, University of North Carolina, Chapel Hill, NC, USA
- RNA Discovery and Lineberger Comprehensive Cancer Centers, University of North Carolina, Chapel Hill, NC, USA
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van Heyningen V. Stochasticity in genetics and gene regulation. Philos Trans R Soc Lond B Biol Sci 2024; 379:20230476. [PMID: 38432316 PMCID: PMC10909507 DOI: 10.1098/rstb.2023.0476] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2023] [Accepted: 12/20/2023] [Indexed: 03/05/2024] Open
Abstract
Development from fertilized egg to functioning multi-cellular organism requires precision. There is no precision, and often no survival, without plasticity. Plasticity is conferred partly by stochastic variation, present inherently in all biological systems. Gene expression levels fluctuate ubiquitously through transcription, alternative splicing, translation and turnover. Small differences in gene expression are exploited to trigger early differentiation, conferring distinct function on selected individual cells and setting in motion regulatory interactions. Non-selected cells then acquire new functions along the spatio-temporal developmental trajectory. The differentiation process has many stochastic components. Meiotic segregation, mitochondrial partitioning, X-inactivation and the dynamic DNA binding of transcription factor assemblies-all exhibit randomness. Non-random X-inactivation generally signals deleterious X-linked mutations. Correct neural wiring, such as retina to brain, arises through repeated confirmatory activity of connections made randomly. In immune system development, both B-cell antibody generation and the emergence of balanced T-cell categories begin through stochastic trial and error followed by functional selection. Aberrant selection processes lead to immune dysfunction. DNA sequence variants also arise through stochastic events: some involving environmental fluctuation (radiation or presence of pollutants), or genetic repair system malfunction. The phenotypic outcome of mutations is also fluid. Mutations may be advantageous in some circumstances, deleterious in others. This article is part of a discussion meeting issue 'Causes and consequences of stochastic processes in development and disease'.
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Affiliation(s)
- Veronica van Heyningen
- UCL Institute of Ophthalmology, University College London, London, EC1V 9EL, UK
- MRC Human Genetics Unit, Institute of Genetics and Cancer, University of Edinburgh, Edinburgh EH4 2XU, UK
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Franco-Enzástiga Ú, Inturi NN, Natarajan K, Mwirigi JM, Mazhar K, Schlachetzki JC, Schumacher M, Price TJ. Epigenomic landscape of the human dorsal root ganglion: sex differences and transcriptional regulation of nociceptive genes. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.03.27.587047. [PMID: 38586055 PMCID: PMC10996669 DOI: 10.1101/2024.03.27.587047] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/09/2024]
Abstract
Gene expression is influenced by chromatin architecture via controlled access of regulatory factors to DNA. To better understand regulation of gene expression in the human dorsal root ganglion (hDRG) we used bulk and spatial transposase-accessible chromatin technology followed by sequencing (ATAC-seq). We detected a total of 3005 differentially accessible chromatin regions (DARs) between sexes using bulk ATAC-seq. DARs in female hDRG mapped mainly to the X chromosome. In males, DARs were found in autosomal genes. We also found differential transcription factor binding motifs within DARs. EGR1/3 and SP1/4 were abundant in females, and JUN, FOS and other AP-1 family members in males. With the aim of dissecting the open chromatin profile in hDRG neurons, we used spatial ATAC-seq. Consistent with our bulk ATAC-seq data, most of the DARs in female hDRG were located in X chromosome genes. Neuron cluster showed higher chromatin accessibility in GABAergic, glutamatergic, and interferon-related genes in females, and in Ca2+-signaling-related genes in males. Sex differences in open chromatin transcription factor binding sites in neuron-proximal barcodes were consistent with the bulk data, having EGR1 transcription factor activity in females and AP-1 family members in males. Accordingly, we showed higher expression of EGR1 in female hDRG compared to male with in-situ hybridization. Our findings point to epigenomic sex differences in the hDRG that likely underlie divergent transcriptional responses that determine mechanistic sex differences in pain.
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Affiliation(s)
- Úrzula Franco-Enzástiga
- Center for Advanced Pain Studies, School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, Texas 75080
| | - Nikhil N. Inturi
- Center for Advanced Pain Studies, School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, Texas 75080
| | - Keerthana Natarajan
- Center for Advanced Pain Studies, School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, Texas 75080
| | - Juliet M. Mwirigi
- Center for Advanced Pain Studies, School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, Texas 75080
| | - Khadja Mazhar
- Center for Advanced Pain Studies, School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, Texas 75080
| | - Johannes C.M. Schlachetzki
- Department of Cellular and Molecular Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0651, USA
| | - Mark Schumacher
- Department of Anesthesia and Perioperative Care and the UCSF Pain and Addiction Research Center, University of California, San Francisco, California, 94143 USA
| | - Theodore J. Price
- Center for Advanced Pain Studies, School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, Texas 75080
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Malcore RM, Kalantry S. A Comparative Analysis of Mouse Imprinted and Random X-Chromosome Inactivation. EPIGENOMES 2024; 8:8. [PMID: 38390899 PMCID: PMC10885068 DOI: 10.3390/epigenomes8010008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2024] [Revised: 02/01/2024] [Accepted: 02/06/2024] [Indexed: 02/24/2024] Open
Abstract
The mammalian sexes are distinguished by the X and Y chromosomes. Whereas males harbor one X and one Y chromosome, females harbor two X chromosomes. To equalize X-linked gene expression between the sexes, therian mammals have evolved X-chromosome inactivation as a dosage compensation mechanism. During X-inactivation, most genes on one of the two X chromosomes in females are transcriptionally silenced, thus equalizing X-linked gene expression between the sexes. Two forms of X-inactivation characterize eutherian mammals, imprinted and random. Imprinted X-inactivation is defined by the exclusive inactivation of the paternal X chromosome in all cells, whereas random X-inactivation results in the silencing of genes on either the paternal or maternal X chromosome in individual cells. Both forms of X-inactivation have been studied intensively in the mouse model system, which undergoes both imprinted and random X-inactivation early in embryonic development. Stable imprinted and random X-inactivation requires the induction of the Xist long non-coding RNA. Following its induction, Xist RNA recruits proteins and complexes that silence genes on the inactive-X. In this review, we present a current understanding of the mechanisms of Xist RNA induction, and, separately, the establishment and maintenance of gene silencing on the inactive-X by Xist RNA during imprinted and random X-inactivation.
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Affiliation(s)
- Rebecca M Malcore
- Department of Human Genetics, University of Michigan Medical School, Ann Arbor, MI 48105, USA
| | - Sundeep Kalantry
- Department of Human Genetics, University of Michigan Medical School, Ann Arbor, MI 48105, USA
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Butler J, Dale N. X-linked Charcot Marie Tooth mutations alter CO 2 sensitivity of connexin32 hemichannels. Front Cell Neurosci 2023; 17:1330983. [PMID: 38188670 PMCID: PMC10771293 DOI: 10.3389/fncel.2023.1330983] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Accepted: 12/07/2023] [Indexed: 01/09/2024] Open
Abstract
Connexin32 (Cx32) is expressed in myelinating Schwann cells. It forms both reflexive gap junctions, to facilitate transfer of molecules from the outer to the inner myelin layers and hemichannels at the paranode to permit action potential-evoked release of ATP into the extracellular space. Loss of function mutations in Cx32 cause X-linked Charcot Marie Tooth disease (CMTX), a slowly developing peripheral neuropathy. The mechanistic links between Cx32 mutations and CMTX are not well understood. As Cx32 hemichannels can be opened by increases in PCO2, we have examined whether CMTX mutations alter this CO2 sensitivity. By using Ca2+ imaging, dye loading and genetically encoded ATP sensors to measure ATP release, we have found 5 CMTX mutations that abolish the CO2 sensitivity of Cx32 hemichannels (A88D, 111-116 Del, C179Y, E102G, V139M). Others cause a partial loss (L56F, R220Stop, and R15W). Some CMTX mutations have no apparent effect on CO2 sensitivity (R15Q, L9F, G12S, V13L, V84I, W133R). The mutation R15W alters multiple additional aspects of hemichannel function including Ca2+ and ATP permeability. The mutations that abolish CO2 sensitivity are transdominant and abolish CO2 sensitivity of co-expressed Cx32WT. We have shown that Schwannoma RT4 D6P2T cells can release ATP in response to elevated PCO2 via the opening of Cx32. This is consistent with the hypothesis that the CO2 sensitivity of Cx32 may be important for maintenance of healthy myelin. Our data, showing a transdominant effect of certain CMTX mutations on CO2 sensitivity, may need to be taken into account in any future gene therapies for this condition.
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Affiliation(s)
| | - Nicholas Dale
- School of Life Sciences, University of Warwick, Coventry, United Kingdom
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