Dosage Compensation in Drosophila: Evidence That daughterless and Sex-lethal Control X Chromosome Activity at the Blastoderm Stage of Embryogenesis

Genetics ◽  
1987 ◽  
Vol 117 (3) ◽  
pp. 477-485
Author(s):  
J Peter Gergen
Keyword(s):  
X Chromosome ◽  
Dosage Compensation ◽  
Lethal Gene ◽  
Gene Products ◽  
Lethal Control ◽  
Eye Color ◽  
Phenotypic Assay ◽  
Sex Lethal ◽  
Blastoderm Stage

ABSTRACT Dosage compensation is a mechanism that equalizes the expression of X chromosome linked genes in males, who have one X chromosome, with that in females, who have two. In Drosophila, this is achieved by the relative hyperactivation of X-linked genes in males, as was first shown by Muller using a phenotypic assay based on adult eye color. Several genes involved in regulating dosage compensation have been identified through the isolation of mutations that are sex-specific lethals. However, because of this lethality it is not straightforward to assay the relative roles of these genes using assays based on adult phenotypes. Here this problem is circumvented using an assay based on embryonic phenotypes. These experiments indicate that dosage compensation is established early in development and demonstrate that the daughterless and Sex-lethal gene products are involved in regulating X chromosome activity at the blastoderm stage of embryogenesis.

scholarly journals Differential effects of Sex-lethal mutations on dosage compensation early in Drosophila development.

Genetics ◽  
1994 ◽  
Vol 136 (3) ◽  
pp. 1051-1061
Author(s):  
M Bernstein ◽  
T W Cline
Keyword(s):  
Sex Determination ◽  
X Chromosome ◽  
Dosage Compensation ◽  
Rna Splicing ◽  
Lethal Gene ◽  
Loss Of Function ◽  
Developmental Pathway ◽  
Pathway Choice ◽  
Sex Lethal ◽  
Blastoderm Stage

Abstract In response to the primary sex determination signal, X chromosome dose, the Sex-lethal gene controls all aspects of somatic sex determination and differentiation, including X chromosome dosage compensation. Two complementary classes of mutations have been identified that differentially affect Sxl somatic functions: (1) those impairing the "early" function used to set developmental pathway choice in response to the sex determination signal and (2) those impairing "late" functions involved in maintaining the pathway choice independent of the initiating signal and/or in directing differentiation. This "early vs. late" distinction correlates with a switch in promoter utilization from SxlPe to SxlPm at the blastoderm stage and a corresponding switch from transcriptional to RNA splicing control. Here we characterize five partial-loss-of-function Sxl alleles to explore a distinction between "early vs. late" functioning of Sxl in dosage compensation. Assaying for dosage compensation during the blastoderm stage, we find that the earliest phase of the dosage compensation process is controlled by products of the early Sxl promoter, SxlPe. Hence, in addition to triggering the sexual pathway decision of cells, products derived from SxlPe also control early dosage compensation, the first manifestation of sexually dimorphic differentiation. The effects of mutant Sxl alleles on early dosage compensation are consistent with their previous categorization as early vs. late defective with respect to their effects on pathway initiation. Results reported here suggest that the dosage compensation regulatory genes currently known to function downstream of Sxl, genes known as the "male-specific lethals," do not control all aspects of dosage compensation either at the blastoderm stage or later in development. In the course of this study, we also discovered that the canonical early defective allele, Sxlf9, which is impaired in its ability to establish the female developmental pathway commitment, is likely to be defective in the stability and/or functioning of products derived from SxlPe, rather than in the ability of SxlPe to respond to the chromosomal sex determination signal.

Evidence that MSL-mediated dosage compensation in Drosophila begins at blastoderm

Development ◽  
1996 ◽  
Vol 122 (9) ◽  
pp. 2751-2760 ◽  
Author(s):  
A. Franke ◽  
A. Dernburg ◽  
G.J. Bashaw ◽  
B.S. Baker
Keyword(s):  
X Chromosome ◽  
Dosage Compensation ◽  
Dependent Manner ◽  
Gene Products ◽  
Histone H4 ◽  
Single Male ◽  
Somatic Tissues ◽  
Male Specific Lethal ◽  
Male Specific ◽  
Blastoderm Stage

In Drosophila equalization of the amounts of gene products produced by X-linked genes in the two sexes is achieved by hypertranscription of the single male X chromosome. This process, dosage compensation, is controlled by a set of male-specific lethal (msl) genes, that appear to act at the level of chromatin structure. The properties of the MSL proteins have been extensively studied in the polytene salivary gland chromosomes where they bind to the same set of sites along the male X chromosome in a co-dependent manner. Here we report experiments that show that the MSL proteins first associate with the male X chromosome as early as blastoderm stage, slightly earlier than the histone H4 isoform acetylated at lysine 16 is detected on the X chromosome. MSL binding to the male X chromosome is observed in all somatic tissues of embryos and larvae. Binding of the MSLs to the X chromosome is also interdependent in male embryos and prevented in female embryos by the expression of Sex-lethal (Sxl). A delayed onset of binding of the MSLs in male progeny of homozygous mutant msl-1 or mle mothers coupled with the previous finding that such males have an earlier lethal phase supports the idea that msl-mediated dosage compensation begins early in embryogenesis. Other results show that the maleless (MLE) protein on embryo and larval chromosomes differs in its reactivity with antibodies; the functional significance of this finding remains to be explored.

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

Development ◽  
1995 ◽  
Vol 121 (10) ◽  
pp. 3245-3258 ◽  
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.

Genetic evidence that the sans fille locus is involved in Drosophila sex determination.

Genetics ◽  
1988 ◽  
Vol 120 (1) ◽  
pp. 159-171
Author(s):  
B Oliver ◽  
N Perrimon ◽  
A P Mahowald
Keyword(s):  
Sex Determination ◽  
Dosage Compensation ◽  
Germ Line ◽  
Ovarian Tumors ◽  
Lethal Gene ◽  
Nurse Cells ◽  
Loss Of Function ◽  
Wild Type ◽  
Sex Lethal

Abstract Females homozygous for sans fille1621 (= fs(1)1621) have an abnormal germ line. Instead of producing eggs, the germ-line cells proliferate forming ovarian tumors or excessive numbers of nurse cells. The Sex-lethal gene product(s) regulate the branch point of the dosage compensation and sex determination pathways in the soma. The role of Sex-lethal in the germ line is not clear but the germ line of females homozygous for female sterile Sex-lethal alleles or germ-line clones of loss-of-function alleles are characterized by ovarian tumors. Females heterozygous for sans fille1621 or Sex-lethal are phenotypically wild type with respect to viability and fertility but females trans-heterozygous for sans fille1621 and Sex-lethal show ovarian tumors, somatic sexual transformations, and greatly reduced viability.

scholarly journals Transposon insertions causing constitutive Sex-lethal activity in Drosophila melanogaster affect Sxl sex-specific transcript splicing.

Genetics ◽  
1995 ◽  
Vol 139 (2) ◽  
pp. 631-648
Author(s):  
M Bernstein ◽  
R A Lersch ◽  
L Subrahmanyan ◽  
T W Cline
Keyword(s):  
Drosophila Melanogaster ◽  
X Chromosome ◽  
Dosage Compensation ◽  
Rna Splicing ◽  
Wild Type ◽  
Gain Of Function ◽  
Positive Regulators ◽  
Sex Lethal ◽  
Male Specific ◽  
Transposon Insertions

Abstract Sex-lethal (Sxl) gene products induce female development in Drosophila melanogaster and suppress the transcriptional hyperactivation of X-linked genes responsible for male X-chromosome dosage compensation. Control of Sxl functioning by the dose of X-chromosomes normally ensures that the female-specific functions of this developmental switch gene are only expressed in diplo-X individuals. Although the immediate effect of X-chromosome dose is on Sxl transcription, during most of the life cycle "on" vs. "off" reflects alternative Sxl RNA splicing, with the female (productive) splicing mode maintained by a positive feedback activity of SXL protein on Sxl pre-mRNA splicing. "Male-lethal" (SxlM) gain-of-function alleles subvert Sxl control by X-chromosome dose, allowing female Sxl functions to be expressed independent of the positive regulators upstream of Sxl. As a consequence, SxlM haplo-X animals (chromosomal males) die because of improper dosage compensation, and SxlM chromosomal females survive the otherwise lethal effects of mutations in upstream positive regulators. Five independent spontaneous SxlM alleles were shown previously to be transposon insertions into what was subsequently found to be the region of regulated sex-specific Sxl RNA splicing. We show that these five alleles represent three different mutant types: SxlM1, SxlM3, and SxlM4. SxlM1 is an insertion of a roo element 674 bp downstream of the translation-terminating male-specific exon. SxlM3 is an insertion of a hobo transposon (not 297 as previously reported) into the 3' splice site of the male exon, and SxlM4 is an insertion of a novel transposon into the male-specific exon itself. We show that these three gain-of-function mutants differ considerably in their ability to bypass the sex determination signal, with SxlM4 being the strongest and SxlM1 the weakest. This difference is also reflected in effects of these mutations on sex-specific RNA splicing and on the rate of appearance of SXL protein in male embryos. Transcript analysis of double-mutant male-viable SxlM derivatives in which the SxlM insertion is cis to loss-of-function mutations, combined with other results reported here, indicates that the constitutive character of these SxlM alleles is a consequence of an alteration of the structure of the pre-mRNA that allows some level of female splicing to occur even in the absence of functional SXL protein. Surprisingly, however, most of the constitutive character of SxlM alleles appears to depend on the mutant alleles' responsiveness, perhaps greater than wild-type, to the autoregulatory splicing activity of the wild-type SXL proteins they produce.

scholarly journals Regulation of behavioral and pheromonal aspects of sex determination in Drosophila melanogaster by the Sex-lethal gene.

Genetics ◽  
1989 ◽  
Vol 123 (3) ◽  
pp. 535-541 ◽  
Author(s):  
L Tompkins ◽  
S P McRobert
Keyword(s):  
Drosophila Melanogaster ◽  
Sexual Behavior ◽  
Sex Determination ◽  
Ectopic Expression ◽  
Lethal Gene ◽  
Gene Products ◽  
Morphological Aspects ◽  
Sex Lethal ◽  
Normal Males ◽  
Female Specific

Abstract We have shown that the Sex-lethal (Sxl) gene, which controls morphological aspects of sex determination in Drosophila melanogaster, also regulates sexual behavior. Chromosomal males that are hemizygous for a deletion of the entire Sxl locus perform normal courtship and synthesize the two courtship-inhibiting pheromones that normal males make. However, ectopic expression of female-specific Sex-lethal gene products drastically alters chromosomal males' ability to perform and elicit courtship and increases the probability that they will synthesize a courtship-stimulating pheromone or fail to synthesize one of the inhibitory pheromones. These observations suggest that male sexual behavior is a consequence of the Sxl gene's being functionally inactive in haplo-X flies.

scholarly journals Two Classes of Dosage Compensation Complex Binding Elements along Caenorhabditis elegans X Chromosomes

2009 ◽  
Vol 29 (8) ◽  
pp. 2023-2031 ◽  
Author(s):  
Timothy A. Blauwkamp ◽  
Gyorgyi Csankovszki
Keyword(s):  
Caenorhabditis Elegans ◽  
X Chromosome ◽  
Dosage Compensation ◽  
Gene Products ◽  
Dosage Compensation Complex ◽  
X Chromosomes ◽  
Linked Gene ◽  
Unknown Mechanism

ABSTRACT Dosage compensation equalizes X-linked gene products between the sexes. In Caenorhabditis elegans, the dosage compensation complex (DCC) binds both X chromosomes in XX animals and halves the transcription from each. The DCC is recruited to the X chromosomes by a number of loci, rex sites, and is thought to spread from these sites by an unknown mechanism to cover the rest of the chromosome. Here we describe a novel class of DCC-binding elements that we propose serve as “way stations” for DCC binding and spreading. Both rex sites and way stations comprise strong foci of DCC binding on the native X chromosome. However, rex sites maintain their ability to bind large amounts of DCC even on X duplications detached from the native X, while way stations do not. These results suggest that two distinct classes of DCC-binding elements facilitate recruitment and spreading of the DCC along the X chromosome.

scholarly journals A Plasmid Model System Shows that Drosophila Dosage Compensation Depends on the Global Acetylation of Histone H4 at Lysine 16 and Is Not Affected by Depletion of Common Transcription Elongation Chromatin Marks

2007 ◽  
Vol 27 (22) ◽  
pp. 7865-7870 ◽  
Author(s):  
Ruth Yokoyama ◽  
Antonio Pannuti ◽  
Huiping Ling ◽  
Edwin R. Smith ◽  
John C. Lucchesi
Keyword(s):  
X Chromosome ◽  
Dosage Compensation ◽  
Regulatory Mechanism ◽  
Model System ◽  
Special Role ◽  
Gene Products ◽  
Histone H4 ◽  
Linked Gene ◽  
Experimental Approaches ◽  
Transcriptional Units

ABSTRACTDosage compensation refers to the equalization of most X-linked gene products between males, which have one X chromosome and a single dose of X-linked genes, and females, which have two X's and two doses of such genes. We developed a plasmid-based model of dosage compensation that allows new experimental approaches for the study of this regulatory mechanism. InDrosophila melanogaster, an enhanced rate of transcription of the X chromosome in males is dependent upon the presence of histone H4 acetylated at lysine 16. This chromatin mark occurs throughout active transcriptional units, leading us to the conclusion that the enhanced level of transcription is achieved through an enhanced rate of RNA polymerase elongation. We used the plasmid model to demonstrate that enhancement in the level of transcription does not depend on other histone marks and factors that have been associated with the process of elongation, thereby highlighting the special role played by histone H4 acetylated at lysine 16 in this process.

scholarly journals Production of X0 clones in XX females of Drosophila

1991 ◽  
Vol 57 (1) ◽  
pp. 23-28 ◽  
Author(s):  
Daniel Bachiller ◽  
Lucas Sánchez
Keyword(s):  
X Chromosome ◽  
Larval Stage ◽  
Rare Event ◽  
The State ◽  
X Chromosomes ◽  
Larval Stages ◽  
Sex Lethal ◽  
Blastoderm Stage ◽  
State Of Activity

SummaryThe experiments reported here are aimed at determining whether mutations deleting the function of the Sex-lethal (Sxl) gene are able to suppress the lethality of X0 clones, induced in females after the time when the state of activity of Sxl is irreversibly fixed by the ratio of the number of X chromosomes to sets of autosomes (X: A). This analysis was carried out by comparing the frequency of induced male clones (X0 constitution) in SxlfLS/ + and Sxl+/Sxl+ females, following irradiation at blastoderm and larval stages. The genotype used in these experiments, however, could also give rise to 2X; 2A cells homozygous for SxlfLS, and such cells would also differentiate male structures. To minimize this possibility, we have constructed a genotype made up of a ring and a rod X chromosome. In such ring-rod females the production of 2X; 2A clones homozygous for SxlfLS is a rather rare event, if possible at all. X0 male clones were produced in both types of females following irradiation at blastoderm stage, while X0 male clones were only observed in SxlfLS/ + females when irradiation took place at larval stage. In this latter case, the only X0 male clones were those that contained the SxlfLS mutation. These results support the idea of Sánchez & Nöthiger (1983) that the X: A signal irreversibly sets the state of activity of Sxl at blastoderm stage, and in addition show that X0 clones generated after that time are viable if they contain a Sxl− mutation. These results are compatible with the idea of Sxl being the only gene that responds to the X:A signal.

scholarly journals The Drosophila MSL Complex Acetylates Histone H4 at Lysine 16, a Chromatin Modification Linked to Dosage Compensation

2000 ◽  
Vol 20 (1) ◽  
pp. 312-318 ◽  
Author(s):  
Edwin R. Smith ◽  
Antonio Pannuti ◽  
Weigang Gu ◽  
Arnd Steurnagel ◽  
Richard G. Cook ◽  
...  
Keyword(s):  
X Chromosome ◽  
Dosage Compensation ◽  
Chromatin Modification ◽  
Gene Products ◽  
Histone H4 ◽  
Linked Gene ◽  
Rna Transcripts ◽  
Msl Complex ◽  
Males And Females

ABSTRACT In Drosophila, dosage compensation—the equalization of most X-linked gene products in males and females—is achieved by a twofold enhancement of the level of transcription of the X chromosome in males relative to each X chromosome in females. A complex consisting of at least five gene products preferentially binds the X chromosome at numerous sites in males and results in a significant increase in the presence of a specific histone isoform, histone 4 acetylated at lysine 16. Recently, RNA transcripts (roX1 and roX2) encoded by two different genes have also been found associated with the X chromosome in males. We have partially purified a complex containing MSL1, -2, and -3, MOF, MLE, and roX2 RNA and demonstrated that it exclusively acetylates H4 at lysine 16 on nucleosomal substrates. These results demonstrate that the MSL complex is responsible for the specific chromatin modification characteristic of the X chromosome in Drosophila males.

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