Induction of female Sex-lethal RNA splicing in male germ cells: implications for Drosophila germline sex determination

Development ◽  
1997 ◽  
Vol 124 (24) ◽  
pp. 5033-5048 ◽  
Author(s):  
J.H. Hager ◽  
T.W. Cline
Keyword(s):  
Sex Determination ◽  
Germ Cells ◽  
Rna Splicing ◽  
Feedback Loop ◽  
Dose Effect ◽  
Male Germ Cells ◽  
Control Female ◽  
Sex Lethal ◽  
Specific Regulation ◽  
Female Specific

With a focus on Sex-lethal (Sxl), the master regulator of Drosophila somatic sex determination, we compare the sex determination mechanism that operates in the germline with that in the soma. In both cell types, Sxl is functional in females (2X2A) and nonfunctional in males (1X2A). Somatic cell sex is determined initially by a dose effect of X:A numerator genes on Sxl transcription. Once initiated, the active state of SXL is maintained by a positive autoregulatory feedback loop in which Sxl protein insures its continued synthesis by binding to Sxl pre-mRNA and thereby imposing the productive (female) splicing mode. The gene splicing-necessary factor (snf), which encodes a component of U1 and U2 snRNPs, participates in this RNA splicing control. Here we show that an increase in the dose of snf+ can trigger the female Sxl RNA splicing mode in male germ cells and can feminize triploid intersex (2X3A) germ cells. These snf+ dose effects are as dramatic as those of X:A numerator genes on Sxl in the soma and qualify snf as a numerator element of the X:A signal for Sxl in the germline. We also show that female-specific regulation of Sxl in the germline involves a positive autoregulatory feedback loop on RNA splicing, as it does in the soma. Neither a phenotypically female gonadal soma nor a female dose of X chromosomes in the germline is essential for the operation of this feedback loop, although a female X-chromosome dose in the germline may facilitate it. Engagement of the Sxl splicing feedback loop in somatic cells invariably imposes female development. In contrast, engagement of the Sxl feedback loop in male germ cells does not invariably disrupt spermatogenesis; nevertheless, it is premature to conclude that Sxl is not a switch gene in germ cells for at least some sex-specific aspects of their differentiation. Ironically, the testis may be an excellent organ in which to study the interactions among regulatory genes such as Sxl, snf, ovo and otu which control female-specific processes in the ovary.

scholarly journals sisterless A is required for the activation of Sex lethal in the germline

2019 ◽  
Author(s):  
Raghav Goyal ◽  
Ellen Baxter ◽  
Mark Van Doren
Keyword(s):  
Sex Determination ◽  
X Chromosome ◽  
Germ Cells ◽  
Specific Expression ◽  
Male Germ Cells ◽  
X Chromosomes ◽  
Dna Elements ◽  
Sex Lethal ◽  
Female Specific ◽  
Necessary And Sufficient

ABSTRACTIn Drosophila, sex determination in somatic cells has been well-studied and is under the control of the switch gene Sex lethal (Sxl), which is activated in females by the presence of two X chromosomes. Though sex determination is regulated differently in the germline versus the soma, Sxl is also necessary and sufficient for the female identity in germ cells. Loss of Sxl function in the germline results in ovarian germline tumors, a characteristic of male germ cells developing in a female soma. Further, XY (male) germ cells expressing Sxl are able to produce eggs when transplanted into XX (female) somatic gonads, demonstrating that Sxl is also sufficient for female sexual identity in the germline. As in the soma, the presence of two X chromosomes is sufficient to activate Sxl in the germline, but the mechanism for “counting” X chromosomes in the germline is thought to be different from the soma. Here we have explored this mechanism at both cis- and trans-levels. Our data support the model that the Sxl “establishment” promoter (SxlPE) is activated in a female-specific manner in the germline, as in the soma, but that the timing of SxlPE activation, and the DNA elements that regulate SxlPE are different from those in the soma. Nevertheless, we find that the X chromosome-encoded gene sisterless A (sisA), which helps activate Sxl in the soma, is also essential for Sxl activation in the germline. Loss of sisA function leads to loss of Sxl expression in the germline, and to ovarian tumors and germline loss. These defects can be rescued by the expression of Sxl, demonstrating that sisA lies upstream of Sxl in germline sex determination. We conclude that sisA acts as an X chromosome counting element in both the soma and the germline, but that additional factors that ensure robust, female-specific expression of Sxl in the germline remain to be discovered.

scholarly journals Both Loss-of-Function and Gain-of-Function Mutations in snf Define a Role for snRNP Proteins in Regulating Sex-lethal Pre-mRNA Splicing in Drosophila Development

Genetics ◽  
1996 ◽  
Vol 144 (1) ◽  
pp. 95-108
Author(s):  
Helen K Salz ◽  
Thomas W Flickinger
Keyword(s):  
Sex Determination ◽  
Rna Splicing ◽  
Loss Of Function ◽  
Functional Homology ◽  
Snrnp Protein ◽  
A Cell ◽  
Sex Lethal ◽  
Mutant Phenotypes ◽  
Female Specific ◽  
Male Specific

Abstract The Drosophila snf gene encodes a protein with functional homology to the mammalian UlA and U2B″ snRNP proteins. Studies, based on the analysis of three viable alleles, have suggested a role for snf in establishing the female-specific splicing pattern of the sex determination switch gene, Sex-lethal. Here, we show that the non-sex-specific lethal null allele is required for female sex determination, arguing against the formal possibility that the viable alleles disrupt a function unrelated to snf's wild-type function. Moreover, we find snf is required for normal cell growth and/or survival, as expected for a protein involved in a cell-vital process such as RNA splicing. We also show that of the three viable alleles only one, snfJA2, is a partial loss-of-function mutation. The other two viable alleles, snf1621 and snfe8H, encode antimorphic proteins. We find the antimorphic proteins are mislocalized and correlate their mislocalization with their molecular lesions and mutant phenotypes. Finally, we provide genetic evidence that the antimorphic alleles interfere with the autoregulatory splicing function of the Sex-lethal protein. Based on these studies we suggest a model in which the snRNP protein, Snf, functions with Sex-lethal to block recognition of the regulated male-specific exon.

scholarly journals The Drosophila sex determination gene snf is utilized for the establishment of the female-specific splicing pattern of Sex-lethal.

Genetics ◽  
1993 ◽  
Vol 134 (3) ◽  
pp. 801-807
Author(s):  
E B Albrecht ◽  
H K Salz
Keyword(s):  
Sex Determination ◽  
Rna Splicing ◽  
Null Allele ◽  
Early Embryogenesis ◽  
Wild Type ◽  
Female Progeny ◽  
Splicing Pattern ◽  
Late Embryogenesis ◽  
Sex Lethal ◽  
Female Specific

Abstract The Drosophila snf gene is a positive regulator of the sex determination gene Sex-lethal in both the germline and the soma. Its role in the soma is only evident when the probability of Sex-lethal activation has been reduced. For instance, in an otherwise wild-type background, females homozygous for a weak snf mutation produce both male and female progeny; however, when mated to males hemizygous for a null allele of Sex-lethal, they produce only male progeny. We demonstrate that the lack of female progeny is due to aberrant Sex-lethal regulation in late embryogenesis. In these mutant embryos, there is little accumulation of the late female-specific spliced RNAs and proteins. In contrast, in early embryogenesis, Sex-lethal regulation is not affected. The accumulation of both the early Sex-lethal transcripts and proteins is normal. These results suggest that the wild-type product of snf plays an important role in establishing the female-specific RNA splicing pattern of Sex-lethal. Whether snf influences the female-specific splice site choice directly or indirectly remains to be determined.

scholarly journals Sex determination in Drosophila: sis-b, a major numerator element of the X:A ratio in the soma, does not contribute to the X:A ratio in the germ line

Development ◽  
1993 ◽  
Vol 117 (2) ◽  
pp. 763-767 ◽  
Author(s):  
M. Steinmann-Zwicky
Keyword(s):  
Sex Determination ◽  
Germ Cells ◽  
Germ Line ◽  
Somatic Cells ◽  
Present Evidence ◽  
Primary Signal ◽  
Sex Lethal

In soma and germ cells of Drosophila, the X:A ratio builds a primary signal for sex determination, and in both tissues Sex-lethal (Sxl) function is required for cells to enter the female pathway. In somatic cells of XX animals, the products of X-chromosomal elements of the X:A ratio activate Sxl. Here I show that sisterless-b (sis-b), which is the X-chromosomal element of the somatic X:A ratio that has best been analysed, is not required for oogenesis. I also present evidence that Sxl function might not be sufficient to direct germ cells into the female pathway. These results show that the elements forming the X:A ratio in the germ line are different from the elements forming the X:A ratio in the soma and they suggest that, in the germ line, Sxl might not be regulated by the X:A ratio.

A Theoretical Model for the Regulation of Sex-lethal, a Gene That Controls Sex Determination and Dosage Compensation in Drosophila melanogaster

Genetics ◽  
2003 ◽  
Vol 165 (3) ◽  
pp. 1355-1384
Author(s):  
Matthieu Louis ◽  
Liisa Holm ◽  
Lucas Sánchez ◽  
Marcelle Kaufman
Keyword(s):  
Drosophila Melanogaster ◽  
Theoretical Model ◽  
Sex Determination ◽  
Numerical Simulations ◽  
Cell Fate ◽  
Regulatory Gene ◽  
Experimental Studies ◽  
Formal Basis ◽  
Sex Lethal ◽  
Specific Regulation

Abstract Cell fate commitment relies upon making a choice between different developmental pathways and subsequently remembering that choice. Experimental studies have thoroughly investigated this central theme in biology for sex determination. In the somatic cells of Drosophila melanogaster, Sex-lethal (Sxl) is the master regulatory gene that specifies sexual identity. We have developed a theoretical model for the initial sex-specific regulation of Sxl expression. The model is based on the well-documented molecular details of the system and uses a stochastic formulation of transcription. Numerical simulations allow quantitative assessment of the role of different regulatory mechanisms in achieving a robust switch. We establish on a formal basis that the autoregulatory loop involved in the alternative splicing of Sxl primary transcripts generates an all-or-none bistable behavior and constitutes an efficient stabilization and memorization device. The model indicates that production of a small amount of early Sxl proteins leaves the autoregulatory loop in its off state. Numerical simulations of mutant genotypes enable us to reproduce and explain the phenotypic effects of perturbations induced in the dosage of genes whose products participate in the early Sxl promoter activation.

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 Regulated splicing of the Drosophila sex-lethal male exon involves a blockage mechanism.

1993 ◽  
Vol 13 (3) ◽  
pp. 1408-1414 ◽  
Author(s):  
J I Horabin ◽  
P Schedl
Keyword(s):  
Drosophila Melanogaster ◽  
Alternative Splicing ◽  
Sex Determination ◽  
Splice Site ◽  
Feedback Loop ◽  
Splice Sites ◽  
Alternate Splicing ◽  
Sequence Context ◽  
Sex Lethal ◽  
Hodgkin Cell

In Drosophila melanogaster, sex determination in somatic cells is controlled by a cascade of genes whose expression is regulated by alternative splicing [B. S. Baker, Nature (London) 340:521-524, 1989; J. Hodgkin, Cell 56:905-906, 1989]. The master switch gene in this hierarchy is Sex-lethal. Sex-lethal is turned on only in females, and an autoregulatory feedback loop which controls alternative splicing maintains this state (L. R. Bell, J. I. Horabin, P. Schedl, and T. W. Cline, Cell 65:229-239, 1991; L. N. Keyes, T. W. Cline, and P. Schedl, Cell 68:933-943, 1992). Sex-lethal also promotes female differentiation by controlling the splicing of RNA from the next gene in the hierarchy, transformer. Sosnowski et al. (B. A. Sosnowski, J. M. Belote, and M. McKeown, Cell 58:449-459, 1989) have shown that the mechanism for generating female transformer transcripts is not through the activation of the alternative splice site but by the blockage of the default splice site. We have tested whether an activation or a blockage mechanism is involved in Sex-lethal autoregulation. The male exon of Sex-lethal with flanking splice sites was placed into the introns of heterologous genes. Our results support the blockage mechanism. The poly(U) run at the male exon 3' splice site is required for sex-specific splicing. However, unlike transformer, default splicing to the male exon is sensitive to the sequence context within which the exon resides. This and the observation that the splice signals at the exon are suboptimal are discussed with regard to alternate splicing.

scholarly journals Genetic evidence that the ovo locus is involved in Drosophila germ line sex determination.

Genetics ◽  
1990 ◽  
Vol 125 (3) ◽  
pp. 535-550 ◽  
Author(s):  
B Oliver ◽  
D Pauli ◽  
A P Mahowald
Keyword(s):  
Drosophila Melanogaster ◽  
Sex Determination ◽  
Sexual Identity ◽  
Gene Product ◽  
Germ Cells ◽  
Germ Line ◽  
Partial Transformation ◽  
Loss Of Function ◽  
Lethal Allele ◽  
Sex Lethal

Abstract Zygotically contributed ovo gene product is required for the survival of female germ cells in Drosophila melanogaster. Trans-allelic combinations of weak and dominant ovo mutations (ovoD) result in viable germ cells that appear to be partially transformed from female to male sexual identity. The ovoD2 mutation is partially suppressed by many Sex-lethal alleles that affect the soma, while those that affect only the germ line fail to interact with ovoD2. One of two loss-of-function ovo alleles is suppressed by a loss-of-function Sex-lethal allele. Because ovo mutations are germ line dependent, it is likely that ovo is suppressed by way of communication between the somatic and germ lines. A loss-of-function allele of ovo is epistatic to germ line dependent mutations in Sex-lethal. The germ line dependent sex determination mutation, sans fille, and ovoD mutations show a dominant synergistic interaction resulting in partial transformation of germ line sexual identity. The ovo locus appears to be involved in germ line sex determination and is linked in some manner to sex determination in the soma.

scholarly journals Function of Drosophila ovo+ in germ-line sex determination depends on X-chromosome number

Development ◽  
1994 ◽  
Vol 120 (11) ◽  
pp. 3185-3195 ◽  
Author(s):  
B. Oliver ◽  
J. Singer ◽  
V. Laget ◽  
G. Pennetta ◽  
D. Pauli
Keyword(s):  
Sex Determination ◽  
Zinc Finger Protein ◽  
Germ Line ◽  
Protein S ◽  
In Ovo ◽  
X Chromosomes ◽  
Sex Lethal ◽  
Xx Males ◽  
High Level ◽  
Female Specific

Germ-line sex determination in Drosophila melanogaster requires an assessment of the number of X chromosomes as measured against autosomal standards (XX = female, X = male) and signaling from the soma. Both of these sex determination cues are required for female-specific Sex-lethal+ function in germ cells. The ovo+ locus encodes zinc finger protein(s) required for female-specific splicing of Sex-lethal+ pre-mRNA, making ovo+ a candidate function acting between the two principal cues and Sex-lethal+. We have made ovo reporter genes and find that they show high activity in the germ line of females and low activity in the germ line of males. XY flies transformed into somatic females do not show high levels of reporter activity, while XX flies transformed into somatic males do. This shows that high level ovo+ expression depends on the number of X chromosomes, not the somatic sexual signals. The requirement for ovo+ function is restricted to XX flies. Mutations in ovo have no effect on XY males, X0 males or XY females, but have pronounced effects on germ cell viability in XX females, XX females with sex transformed germ lines, and XX males indicating that ovo+ gene products are required for events occurring only in flies with two X chromosomes.

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