Requirement of Male-Specific Dosage Compensation in Drosophila Females—Implications of Early X Chromosome Gene Expression

Abstract Abnormalities in chromosome number have the potential to disrupt the balance of gene expression and thereby decrease organismal fitness and viability. Such abnormalities occur in most solid tumors and also cause severe developmental defects and spontaneous abortions. In contrast to the imbalances in chromosome dose that cause pathologies, the difference in X-chromosome dose used to determine sexual fate across diverse species is well tolerated. Dosage compensation mechanisms have evolved in such species to balance X-chromosome gene expression between the sexes, allowing them to tolerate the difference in X-chromosome dose. This review analyzes the chromosome counting mechanism that tallies X-chromosome number to determine sex (XO male and XX hermaphrodite) in the nematode Caenorhabditis elegans and the associated dosage compensation mechanism that balances X-chromosome gene expression between the sexes. Dissecting the molecular mechanisms underlying X-chromosome counting has revealed how small quantitative differences in intracellular signals can be translated into dramatically different fates. Dissecting the process of X-chromosome dosage compensation has revealed the interplay between chromatin modification and chromosome structure in regulating gene expression over vast chromosomal territories.

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Assessment of X Chromosome Dosage Compensation in Caenorhabditis elegans by Phenotypic Analysis of lin-14

Genetics ◽

10.1093/genetics/117.4.657 ◽

1987 ◽

Vol 117 (4) ◽

pp. 657-670

Author(s):

Leslie DeLong ◽

Lawrence P Casson ◽

Barbara J Meyer

Keyword(s):

Gene Expression ◽

Caenorhabditis Elegans ◽

X Chromosome ◽

Dosage Compensation ◽

Phenotypic Expression ◽

Transcript Level ◽

Phenotypic Analysis ◽

Linked Gene ◽

Chromosome Gene ◽

The Difference

ABSTRACT Caenorhabditis elegans compensates for the difference in X chromosome gene dose between males (XO) and hermaphrodites (XX) through a mechanism that equalizes the levels of X-specific mRNA transcripts between the two sexes. We have devised a sensitive and quantitative genetic assay to measure perturbations in X chromosome gene expression caused by mutations that affect this process of dosage compensation. The assay is based on quantitating the precocious alae phenotype caused by a mutation that reduces but does not eliminate the function of the X-linked gene lin-14. We demonstrate that in diploid animals the lin-14 gene is dosage compensated between XO and XX animals. In XXX diploid animals, however, lin-14 expression is not compensated, implying that the normal dosage compensation mechanism in C. elegans lacks the capacity to compensate completely for the additional X chromosome in triplex animals. Using the lin-14 assay we compare the effects of mutations in the genes dpy-21, dpy-26, dpy-27, dpy-28, and dpy-22 on X-linked gene expression. Additionally, in the case of dpy-21 we correlate the change in phenotypic expression of lin-14 with a corresponding change in the lin-14 mRNA transcript level.

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Induction and inhibition of Drosophila X chromosome gene expression are both impeded by the dosage compensation complex

10.1101/2021.11.22.469548 ◽

2021 ◽

Author(s):

Richard P Meisel ◽

Danial Asgari ◽

Florencia Schlamp ◽

Robert L Unckless

Keyword(s):

Gene Expression ◽

X Chromosome ◽

Dosage Compensation ◽

Reproductive Tract ◽

Sex Chromosome ◽

Accessory Gland ◽

Gene Content ◽

Dosage Compensation Complex ◽

Specific Expression ◽

Chromosome Gene

Sex chromosome gene content frequently differs from that of the autosomes, a phenomenon that can be informative of the effects of chromatin environment, sex-specific selection, recombination, and ploidy on genome evolution. For example, the Drosophila X chromosome is depauperate in genes with male-biased expression or limited expression in specific tissues—in particular those expressed in the accessory gland of the male reproductive tract. Multiple hypotheses have been put forth to explain the unique gene content of the X chromosome, including selection against male-beneficial X-linked alleles, expression limits imposed by the haploid dosage of the X in males, and interference by the dosage compensation complex (DCC) on expression in males. Here, we investigate these hypotheses by examining differential gene expression in Drosophila melanogaster following several treatments known to have widespread transcriptomic effects: bacterial infection, viral infection, and abiotic stress. We found that genes that are induced (up-regulated) by these biotic and abiotic treatments are frequently under-represented on the X chromosome, but so are those that are repressed (down-regulated) following treatment. We further show that whether a gene is bound by the DCC in males can largely explain the paucity of both up- and down-regulated genes on the X chromosome. Specifically, genes that are bound by the DCC are unlikely to be up- or down-regulated after treatment. Moreover, genes that are closer to a high-affinity site where the DCC is thought to initiate binding to the X chromosome experience a smaller change in expression following treatment. This relationship, however, could partially be explained by a correlation between differential expression and breadth of expression across tissues. Nonetheless, our results suggest that DCC binding, or the associated chromatin modifications, inhibit both up- and down-regulation of X chromosome gene expression within specific contexts. This effect could explain why the Drosophila X chromosome is depauperate in genes with tissue-specific expression, in addition to the paucity of X-linked genes differentially expressed after biotic or abiotic treatments. We propose multiple possible mechanisms of action for the effect, including a role of Males absent on the first (Mof), a component of the DCC, as a dampener of gene expression variance in both males and females.

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Study of Dosage Compensation in Drosophila

Genetics ◽

10.1093/genetics/165.3.1167 ◽

2003 ◽

Vol 165 (3) ◽

pp. 1167-1181

Author(s):

Pei-Wen Chiang ◽

David M Kurnit

Keyword(s):

Gene Expression ◽

X Chromosome ◽

Dosage Compensation ◽

Qpcr Assay ◽

Male And Female ◽

Multiple Genes ◽

Chromosomal Changes ◽

Regulatory Effects

Abstract Using a sensitive RT-QPCR assay, we analyzed the regulatory effects of sex and different dosage compensation mutations in Drosophila. To validate the assay, we showed that regulation for several genes indeed varied with the number of functional copies of that gene. We then confirmed that dosage compensation occurred for most genes we examined in male and female flies. Finally, we examined the effects on regulation of several genes in the MSL pathway, presumed to be involved in sex-dependent determination of regulation. Rather than seeing global alterations of either X chromosomal or autosomal genes, regulation of genes on either the X chromosome or the autosomes could be elevated, depressed, or unaltered between sexes in unpredictable ways for the various MSL mutations. Relative dosage for a given gene between the sexes could vary at different developmental times. Autosomal genes often showed deranged regulatory levels, indicating they were in pathways perturbed by X chromosomal changes. As exemplified by the BR-C locus and its dependent Sgs genes, multiple genes in a given pathway could exhibit coordinate regulatory modulation. The variegated pattern shown for expression of both X chromosomal and autosomal loci underscores the complexity of gene expression so that the phenotype of MSL mutations does not reflect only simple perturbations of genes on the X chromosome.

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Absence of X-chromosome dosage compensation in the primordial germ cells of Drosophila embryos

Scientific Reports ◽

10.1038/s41598-021-84402-7 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Ryoma Ota ◽

Makoto Hayashi ◽

Shumpei Morita ◽

Hiroki Miura ◽

Satoru Kobayashi

Keyword(s):

X Chromosome ◽

Germ Cells ◽

Dosage Compensation ◽

Sex Chromosome ◽

Primordial Germ Cells ◽

Histone H4 ◽

X Chromosomes ◽

Essential Components ◽

Msl Complex ◽

Male Specific

AbstractDosage compensation is a mechanism that equalizes sex chromosome gene expression between the sexes. In Drosophila, individuals with two X chromosomes (XX) become female, whereas males have one X chromosome (XY). In males, dosage compensation of the X chromosome in the soma is achieved by five proteins and two non-coding RNAs, which assemble into the male-specific lethal (MSL) complex to upregulate X-linked genes twofold. By contrast, it remains unclear whether dosage compensation occurs in the germline. To address this issue, we performed transcriptome analysis of male and female primordial germ cells (PGCs). We found that the expression levels of X-linked genes were approximately twofold higher in female PGCs than in male PGCs. Acetylation of lysine residue 16 on histone H4 (H4K16ac), which is catalyzed by the MSL complex, was undetectable in these cells. In male PGCs, hyperactivation of X-linked genes and H4K16ac were induced by overexpression of the essential components of the MSL complex, which were expressed at very low levels in PGCs. Together, these findings indicate that failure of MSL complex formation results in the absence of X-chromosome dosage compensation in male PGCs.

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The msl-2 dosage compensation gene of Drosophila encodes a putative DNA-binding protein whose expression is sex specifically regulated by Sex-lethal

Development ◽

10.1242/dev.121.10.3245 ◽

1995 ◽

Vol 121 (10) ◽

pp. 3245-3258 ◽

Cited By ~ 6

Author(s):

G.J. Bashaw ◽

B.S. Baker

Keyword(s):

Dna Binding ◽

X Chromosome ◽

Dosage Compensation ◽

Ring Finger ◽

The Other ◽

Male Specific Lethal ◽

Alternatively Spliced ◽

Sex Lethal ◽

Specific Regulation ◽

Male Specific

In Drosophila dosage compensation increases the rate of transcription of the male's X chromosome and depends on four autosomal male-specific lethal genes. We have cloned the msl-2 gene and shown that MSL-2 protein is co-localized with the other three MSL proteins at hundreds of sites along the male polytene X chromosome and that this binding requires the other three MSL proteins. msl-2 encodes a protein with a putative DNA-binding domain: the RING finger. MSL-2 protein is not produced in females and sequences in both the 5′ and 3′ UTRs are important for this sex-specific regulation. Furthermore, msl-2 pre-mRNA is alternatively spliced in a Sex-lethal-dependent fashion in its 5′ UTR.

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X chromosome gene dosage compensation in female mammals

Seminars in Developmental Biology ◽

10.1006/sedb.1993.1015 ◽

1993 ◽

Vol 4 (2) ◽

pp. 129-139 ◽

Cited By ~ 9

Author(s):

Giuseppe Borsani ◽

Andrea Ballabio

Keyword(s):

X Chromosome ◽

Dosage Compensation ◽

Gene Dosage ◽

Chromosome Gene

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Drosophila Male-Specific Lethal 2 Protein Controls Sex-Specific Expression of the roX Genes

Genetics ◽

10.1093/genetics/166.4.1825 ◽

2004 ◽

Vol 166 (4) ◽

pp. 1825-1832 ◽

Cited By ~ 1

Author(s):

Barbara P Rattner ◽

Victoria H Meller

Keyword(s):

Gene Expression ◽

Transcriptional Regulation ◽

X Chromosome ◽

Specific Expression ◽

Linked Gene ◽

Male And Female ◽

Male Specific Lethal ◽

Msl Complex ◽

Male Specific ◽

Rox Rna

Abstract The MSL complex of Drosophila upregulates transcription of the male X chromosome, equalizing male and female X-linked gene expression. Five male-specific lethal proteins and at least one of the two noncoding roX RNAs are essential for this process. The roX RNAs are required for the localization of MSL complexes to the X chromosome. Although the mechanisms directing targeting remain speculative, the ratio of MSL protein to roX RNA influences localization of the complex. We examine the transcriptional regulation of the roX genes and show that MSL2 controls male-specific roX expression in the absence of any other MSL protein. We propose that this mechanism maintains a stable MSL/roX ratio that is favorable for localization of the complex to the X chromosome.

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Dosage Compensation and Gene Expression of the X Chromosome in Sheep

G3 Genes|Genome|Genetics ◽

10.1534/g3.118.200815 ◽

2018 ◽

Vol 9 (1) ◽

pp. 305-314 ◽

Cited By ~ 2

Author(s):

Jingyue (Ellie) Duan ◽

Kaleigh Flock ◽

Nathanial Jue ◽

Mingyuan Zhang ◽

Amanda Jones ◽

...

Keyword(s):

Gene Expression ◽

X Chromosome ◽

Dosage Compensation

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Zinc Finger Protein Zn72D Promotes Productive Splicing of the maleless Transcript

Molecular and Cellular Biology ◽

10.1128/mcb.01415-07 ◽

2007 ◽

Vol 27 (24) ◽

pp. 8760-8769 ◽

Cited By ~ 9

Author(s):

Kathleen A. Worringer ◽

Barbara Panning

Keyword(s):

Gene Expression ◽

Rna Polymerase Ii ◽

Zinc Finger ◽

X Chromosome ◽

Dosage Compensation ◽

Fluorescent Protein ◽

Zinc Finger Protein ◽

General Factor ◽

Finger Protein ◽

Msl Complex

ABSTRACT In organisms with sex chromosomes, dosage compensation equalizes gene expression between the sexes. In Drosophila melanogaster males, the male-specific lethal (MSL) complex of proteins and two noncoding roX RNAs coat the X chromosome, resulting in a twofold transcriptional upregulation to equalize gene expression with that of females. How MSL complex enrichment on the X chromosome is regulated is not well understood. We performed an RNA interference screen to identify new factors required for dosage compensation. Using a Drosophila Schneider S2 cell line in which green fluorescent protein (GFP)-tagged MSL2 localizes to the X chromosome, we assayed ∼7,200 knockdowns for their effects on GFP-MSL2 distribution. One factor identified is the zinc finger protein Zn72D. In its absence, the MSL complex no longer coats the X chromosome. We demonstrate that Zn72D is required for productive splicing of the transcript for the MSL protein Maleless, explaining the dosage compensation defect. However, Zn72D is required for the viability of both sexes, indicating its functions are not sex specific. Consistent with this, Zn72D colocalizes with elongating RNA polymerase II, implicating it as a more general factor involved in RNA metabolism.

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