Cyclin B accumulation is critical to mitotic entry, while its degradation is required for mitotic exit. In early embryos and some cultured cells, cyclin B mRNA localizes around centrosomes and the spindle poles, suggesting that transcript localization and local translation may help drive mitotic division. I am systematically testing the role of cyclin B mRNA localization during early Drosophila embryogenesis.  Using time-lapse analysis of Drosophila embryos injected with fluorescent RNA derivatives, I was able to characterize cyclin B mRNA localization during the cell cycle in live embryos. Using this injection assay, I have also identified cis-acting sequence elements in the cyclin B 3’-UTR required for efficient particle formation and centrosome localization.

A. Endogenous cyclin B mRNA are revealed by fluorescent in situ hybridization (FISH). B.To assay localization in vivo, capped RNAs were synthesized in vitro in the presence of Cy3-UTP. Fluorescent cyclin B mRNAs (red) were injected into living embryos expressing GFP-DTACC (green, centrosome staining). Embryos are in interphase.

Project 2 - Post-transcriptional regulation of embryogenesis and cell cycle progression

In most metazoans, embryogenesis is initiated by a cleavage stage characterized by rapid division the absence of transcription. Post-transcriptional mechanisms are therefore critical to this initial phase of development. Cleavage terminates and zygotic gene expression is first required at the mid-blastula transition (MBT), which marks the switch from maternal to zygotic control of development. The timing of the MBT depends on the ratio of nuclei to cytoplasm and an uncharacterized maternal timer. I am interested in post-transcriptional regulation of the cleavage stage divisions and the transition from maternal to zygotic control of development at the Drosophila equivalent of the MBT.

beatrice.benoit@umassmed.edu

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In Drosophila melanogaster, the embryonic axes are specified during oogenesis through the asymmetric localization of protein and mRNA morphogens on a polarized microtubule network. Defects in axis specification during oogenesis lead to developmental defects resulting in female sterility or maternal effect lethality. Work from our lab has shown that mutations in genes involved in RNA silencing, including armitage, aubergine, maelstrom and spn-E disrupt microtubule polarization and posterior and dorsal-ventral morphogen localization resulting in patterning defects in the embryo (Cook et al, 2003). Interestingly, it has recently been observed that a subset of RNAi mutants, dcr-1 and loquatious, produce an earlier defect in germline stem cell maintenance (Hatfield et al, 2005; Foestemann et al, 2005). I am exploring the role of the RNAi machinery in embryonic patterning and germline stem cell maintenance using genetic, biochemical and immunofluorescence microscopy techniques.

carla.klattenhoff@umassmed.edu

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birgit.koppetsch@umassmed.edu

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I am interested in studying the mechanism of mitotic failure in Dicer mutant vertebrate cells. Dicer, an RNaseIII enzyme, is an important component of RNA mediated silencing and its absence leads to loss of centromeric silencing, defects in stem cell differentiation, microRNA (miRNA) processing defects, loss of transcriptional gene silencing (TGS), and cell death. I use Dicer-/- DT40 cells (chicken B-cell lymphoma cell line), and human colorectal cancer cells HCT116 for my studies.

jaspreet.khurana@umassmed.edu

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seongae.kwak@umassmed.edu

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My research interest is DNA repair and mutagenesis. DNA repair mechanisms are the key factors in the maintenance of genome integrity and stability, therefore defects in these pathways can lead to genetic diseases and cancer. In a previous lab I studied the molecular mechanisms of cytotoxicity induced by certain anticancer drugs such as cisplatin and methylating agents using bacterial model.

Presently my research is focused towards understanding the developmental role of RNA interference via repeat associated siRNA (rasiRNA) in fruit flies. Recently it has been shown that defects in components of rasiRNA pathway such as aubergine and armitage trigger accumulation of germline specific gamma-H2Av foci characteristic of DNA double strand breaks (Klattenhoff C. et al. 2007). Genetic analysis of this phenomenon indicated that the nature of these breaks is different from those induced during meiosis. Therefore it was concluded that the key developmental function of rasiRNA could be to suppress DNA damage signaling in the germline. Currently I am trying to understand the relationship between DNA damage signaling and rasiRNA interference in the protection of germline genome integrity in Drosophila melanogaster.

anetta.nowosielska@umassmed.edu

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With over 20 years of experience in Drosophila labs, I serve as an extra pair of hands in several of the lab projects with a strong focus on Drosophila genetics.  I’m supporting ongoing projects by creating double and triple mutants, as well as recombinants and transgenic flies. In addition to fly pushing, I help with  phenotypic analyses on mutant ovaries and embryos using confocal microscopy. At the bench I’ve been involved in cloning, expressing and purifying fusion proteins for antibody production.  I’m responsible for maintaining the lab fly stocks and I assist in daily maintenance of the lab.

nadine.schultz@umassmed.edu

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Under normal conditions, the G2/M damage checkpoint delays progression into mitosis to allow time for repair.  However, when checkpoint control fails and cells enter mitosis with DNA lesions, mitosis is aborted through a poorly understood process termed mitotic catastrophe. Drosophila syncytial embryos are ideal to assay the mitotic DNA damage response, since they readily enter mitosis in the presence of damage. However, the long term goal of studying the mitotic DNA damage response will be to understand this process in humans, where it might be a tumour suppressing response that serves to eliminate damaged cells with a checkpoint deficient genetic background. Taking advantage of both model systems, I am addressing which mechanisms cells use to abort mitosis in response to DNA lesions.

Before joining Bill's lab in 2004, I studied centrosome function during spindle assembly in Drosophila (EMBL, Germany, 1999-2004) and worked on proteome profiling of human bladder tumours (University of Aarhus, Denmark, 1997-1999).

hanne.varmark @umassmed.edu

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