NeMo

The nuclear envelope is the site of poorly understood interactions with chromatin and chromosomal regions. Defects in the organization of the nuclear envelope cause complex perturbations in gene regulation in so-called laminopathies. Likewise, during development, the precise regulation of transcription may require controlled interactions with the nuclear envelope. We have identified Char, a new nuclear envelope protein in Drosophila, essential for nuclear envelope morphogenesis and nuclear anchoring at the cell cortex. In mutants, the spatial organization of chromatin is affected and transcriptional activation in the zygote is also perturbed. Thus, the early Drosophila embryo proves a very interesting system to study how the polarized morphogenesis of the nuclear envelope controls both chromatin organization and transcription in the zygote. Char provides a remarkable entry point in the study of this process. The aim of this project is exploit the strength of this system to identify new components of this poorly understood pathway. To that end, we will combine genetic, biochemical, microscopic and bioinformatics approaches. We will first identify new genes underlying NE morphogenesis, in order to link cytoplasmic determinants (MT, centrosomes) and nucleoplasmic components (Char, Lamin). We will perform a genetic screen and look for molecular partners of Char. Second, we will study the link between NE morphogenesis and transcription. This involves exploring the organization and dynamics of chromosomal and chromatin in wild type and char mutant embryos, as well as transcription of zygotically induced and repressed genes. We will also test the role of microtubules and centrosomes in these processes. Finally, in collaboration with Denis Thieffry, we will search for cis-regulatory elements common to distinct sub-classes of zygotically activated genes as well as associated with char regulated genes. This project will rely on statistical analysis of transcriptome data and on computational comparative analysis of genomic sequences. Candidate motifs identified with these approaches will be tested in vivo through the construction of reporter systems under the control of identified regulatory elements. The integration of these projects will allow us to identify new genes important for nuclear envelope-associated transcriptional regulation and to assemble them in a pathway starting with cytoplasmic organizing determinants, including components of the nuclear envelope and impinging on regulatory motifs important for transcriptional regulation.