Sex determination: insights from the silkworm
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Doublesex
Melanogaster
Sexual Differentiation
Splicing factor
Doublesex
Sexual Differentiation
Sex reversal
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Doublesex
Sexual Differentiation
Flutamide
Sex reversal
Progestin
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ABSTRACT The hermaphrodite (her) gene is necessary for sexual differentiation in Drosophila. Our characterization of her’s zygotic function suggests that one set of female-specific terminal differentiation genes, the yolk protein (yp) genes, is transcriptionally activated by two separate pathways. One is a female-specific pathway, which is positively regulated by the female-specific doublesex protein (DSXF). The other is a non-sex-specific pathway, that is positively regulated by HER. The HER pathway is prevented from functioning in males by the action of the male-specific doublesex protein (DSXM). The HER and DSX pathways also function independently to control downstream target genes in the precursor cells that give rise to the vaginal teeth and dorsal anal plate of females, and the lateral anal plates of males. However, a female-specific pathway that is dependent on both DSXF and HER controls the female- specific differentiation of the foreleg bristles and tergites 5 and 6, and the male-specific differentiation of these tissues does not require the suppression of HER’s function by DSXM.
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Sexual Differentiation
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ABSTRACT Sex determination is controlled by global regulatory genes, such as tra-1 in Caenorhabditis elegans, Sex lethal in Drosophila, or Sry in mammals. How these genes coordinate sexual differentiation throughout the body is a key unanswered question. tra-1 encodes a zinc finger transcription factor, TRA-1A, that regulates, directly or indirectly, all genes required for sexual development. mab-3 (male abnormal 3), acts downstream of tra-1 and is known to be required for sexual differentiation of at least two tissues. mab-3 directly regulates yolk protein transcription in the intestine and specifies male sense organ differentiation in the nervous system. It encodes a transcription factor related to the products of the Drosophila sexual regulator doublesex (dsx), which also regulates yolk protein transcription and male sense-organ differentiation. The similarities between mab-3 and dsx led us to suggest that some aspects of sex determination may be evolutionarily conserved. Here we find that mab-3 is also required for expression of male-specific genes in sensory neurons of the head and tail and for male interaction with hermaphrodites. These roles in male development and behavior suggest further functional similarity to dsx. In male sensory ray differentiation we find that MAB-3 acts synergistically with LIN-32, a neurogenic bHLH transcription factor. Expression of LIN-32 is spatially restricted by the combined action of the Hox gene mab-5 and the hairy homolog lin-22, while MAB-3 is expressed throughout the lateral hypodermis. Finally, we find that mab-3 transcription is directly regulated in the intestine by TRA-1A, providing a molecular link between the global regulatory pathway and terminal sexual differentiation.
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Sexual Differentiation
Testis determining factor
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In contrast to many developmental processes, sex-determining mechanisms show no clear evolutionary conservation among phyla. However, recent studies indicate that some downstream products of sex determination genes are functionally similar in diverse species. To date, numerous conserved genes involving gonadal sex differentiation have been examined in the teleost fish Nile tilapia (Oreochromis niloticus). Morphogenesis during gonadal differentiation is also conserved, as is evident in the differentiation and development of parenchyma/medullary cells (testis cord) and follicles. Therefore, it is important to understand the mechanisms of gonadal sex differentiation from the perspective of the relationship between conserved gene expression cascades and morphogenesis during gonadal sex differentiation. This article reviews the expression profiles of male- and female-related genes involved in histogenesis during sex differentiation in tilapia and discusses gene function in gonadal sex differentiation, especially the role of endogenous estrogens for ovarian differentiation.
Sexual Differentiation
Doublesex
Nile tilapia
Sex reversal
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ABSTRACT The zygotic function of the hermaphrodite (her) gene of Drosophila plays an important role in sexual differentiation. Our molecular genetic characterization of her suggests that her is expressed sex non-specifically and independently of other known sex determination genes and that it acts together with the last genes in the sex determination hierarchy, doublesex and intersex, to control female sexual differentiation. Consistent with such a terminal function in sexual differentiation, her encodes a protein with C2H2-type zinc fingers. The her zinc fingers are atypical and similar to the even-numbered zinc fingers of ZFY and ZFX proteins in humans and other vertebrates.
Doublesex
Sexual Differentiation
Hermaphrodite
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Abstract doublesex (dsx) is unusual among the known sex-determination genes of Drosophila melanogaster in that functional homologs are found in distantly related species. In flies, dsx occupies a position near the bottom of the sex determination hierarchy. It is expressed in male- and female-specific forms and these proteins function as sex-specific transcription factors. In the studies reported here, we have ectopically expressed the female Dsx protein (DsxF) from a constitutive promoter and examined its regulatory activities independent of other upstream factors involved in female sex determination. We show that it functions as a positive regulator of female differentiation and a negative regulator of male differentiation. As predicted by the DNA-binding properties of the Dsx protein, DsxF and DsxM compete with each other for the regulation of target genes. In addition to directing sex-specific differentiation, DsxF plays an important role in sexual behavior. Wild-type males ectopically expressing DsxF are actively courted by other males. This acquisition of feminine sex appeal is likely due to the induction of female pheromones by DsxF. More extreme behavioral abnormalities are observed when DsxF is ectopically expressed in dsx- XY animals; these animals are not only courted by, but also copulate with, wild-type males. Finally, we provide evidence that intersex is required for the feminizing activities of DsxF and that it is not regulated by the sex-specific splicing cascade.
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Sexual Differentiation
Sexual dimorphism
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By comparing Bombyx mori with the sex-determination system of the model insect Drosophila melanogaster,we presented the molecular structures and roles of Bombyx mori W and Z chromosome and the molecular regulatory mechanism of Bombyx mori doublesex,a hierarchy regulation gene in somatic cells for elucidation the research status of the mechanism of Bombyx mori sex regulation.
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Bombyx
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The doublesex (dsx) gene regulates somatic sexual differentiation in both sexes in Drosophila melanogaster. dsx has active but opposite negative regulatory functions in males and females. In males, the dsx locus represses the genes responsible for female sexual differentiation; male differentiation functions, not being repressed, are expressed. Conversely, in females, the dsx locus represses the genes involved in male sexual differentiation and the female sexual differentiation functions, not being repressed, are expressed. We have molecularly cloned the dsx locus by chromosomal walking and localized the gene within the cloned region by determining the positions of breakpoints of chromosomal rearrangements broken in dsx and in closely flanking regions. The dsx locus is about 40 kb in size. Its DNA is unique and appears to be organized in the same way in genomes of males and females. There is a developmentally and sexually regulated set of transcripts produced by the dsx locus. During the larval period, two sex-nonspecific dsx transcripts are produced. At the end of the larval period, these transcripts disappear and are replaced by a set of male-specific and female-specific transcripts. In adults, an additional male-specific transcript appears. Because genetic analysis has shown that transcription of the dsx locus must occur during the pupal period for proper sexual differentiation, we infer that the sex-specific transcripts seen during the pupal period correspond to the sex determination regulatory functions defined by mutational analysis. The regulation of dsx expression and possible roles of the other dsx transcripts are discussed.
Doublesex
Sexual Differentiation
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Doublesex
Sexual dimorphism
Sexual Differentiation
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