Early embryonic development relies on maternally encoded gene products. In Drosophila, such maternal proteins and RNAs are loaded into the egg during oogenesis, and they regulate multiple events in early embryonic development. As the number of nuclei rapid ly increases after fertilization, there is a maternal to zygotic transition (MZT), in which the soma suddenly becomes transcriptionally active, and many of the maternally encoded products are rapidly degraded.
Although the MZT (also known in other organism s as midblastula transition) is a crucial transition during the early embryonic development, the molecular mechanisms controlling it are poorly understood. In contrast to the soma that becomes transcriptionally active during the blastoderm stage germ cell s remain transcriptionally repressed until later stages of embryonic development (Van Doren et al., 1998). This delay appears to be important for germ line segregation and avoidance of somatic differentiation. Yet, both somatic and germ cells appear to utilize a similar transcriptional regulatory apparatus. Germ cells are transcriptionally repressed because of additional germ-line specific pathways. We have shown that polar granule component (pgc) is specifically required for germ cells transcriptional repression (Martinho et al., 2004).
The main aim of this proposal is to study the molecular mechanisms responsible for early transcriptional activation and germ-line segregation during early embryonic development. This proposal contains three specific research goals:
1) Characterization of the molecular mechanisms responsible for transcriptional activation of the quiescent zygotic genome during MZT,
2) characterization of the differences and similarities between somatic and germ-line transcriptional activation,
3) further characterization of germ-line specific pathways (e.g., pgc) required for segregation of the germ-line and avoidance of somatic differentiation.
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