THE DEVELOPMENT OF SEXUAL DIMORPHISM IN THE DROSOPHILA GONAD
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Date
2006-08-03T15:30:02Z
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Johns Hopkins University
Abstract
Throughout the animal kingdom, sex-specific development is used to create different
forms in males and females. Sexual dimorphism is important for successful reproduction
both on social and biological levels, but is especially vital in the gonad, which must be
sexually dimorphic so it can support germline differentiation into sperm and eggs.
In Drosophila, adult testes and ovaries are highly specialized organs that can
serve as good models for studying sex-specific gonadogenesis, however, it is not well
understood how sexual dimorphism is initially established in the embryo. In this thesis I
present an analysis of how differences between the male and female somatic gonad are
brought about during early development. I have observed that the Drosophila gonad is
already sexually dimorphic at the time of its initial formation, and have characterized two
sex-specific cell types termed the male-specific somatic gonadal precursors (msSGPs)
and the pigment cell precursors. msSGPs and pigment cells give rise to specific adult
testis cell types and express Sox100B, a homolog of Sox9, a factor required for
mammalian sex determination. These two cell types employ different cellular
mechanisms, such as apoptosis and cell-cell signaling, to ensure sexual dimorphism in the
gonad. Sex-specific gonad development relies on positional information provided by the
homeotic genes and proper sexual identity downstream of the sex determination gene
doublesex. The sexually dimorphic behavior of msSGPs and pigment cells appears to be
controlled non-autonomously, which is distinct from cell-autonomous sex determination
that has been reported for most other Drosophila somatic tissues. Finally, I have
analyzed the function of Sox100B in gonad development, and have found a role in adult
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testis formation, suggesting that there is a conserved molecular mechanism for regulating
sexual dimorphism between flies and mammals.
These results demonstrate many common features between Drosophila and
mammalian gonadogenesis. Thus, despite vast differences in initial sex determination
between species, these data strongly support a hypothesis that the downstream regulation
of sexual dimorphism in the gonad is an evolutionarily conserved process at the cellular
and molecular levels.
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Keywords
Drosophila, Sexual dimorphism, Pigment cells, Gonad, Sox 9, msSGPs