Poster abstracts
Poster number 103 submitted by Zachary Morrow
Exploring the function of Cdc5l during zebrafish segmentation
Zachary T. Morrow ( Dept. of Molecular Genetics, The Ohio State University), Thomas L. Gallagher ( Dept. of Molecular Genetics, The Ohio State University), Kiel T. Tietz ( Dept. of Molecular Genetics, The Ohio State University), Jasmine M. McCammon (Department of Molecular & Cell Biology, University of California, Berkeley), Sharon L. Amacher ( Dept. of Molecular Genetics, The Ohio State University)
Abstract:
Vertebrate segmentation is controlled by the segmentation clock, a molecular oscillator that regulates gene expression and cycles rapidly. Oscillating genes include hairy/Enhancer of split-related (her or Hes) genes, which encode transcriptional repressors that auto-inhibit their own expression. To achieve and maintain cycling, the segmentation clock is regulated at many levels, including post-transcriptional mechanisms that influence rates of mRNA export, decay, and translation. In a zebrafish screen for genes involved in oscillatory expression, we identified the honu locus as an important component of post-transcriptional regulation. Using genome-wide SNP association mapping, we molecularly identified the honu lesion as a nonsense mutation in the gene encoding the splicing factor Cdc5l. Cdc5l is a core component of the NineTeen Complex (NTC) and plays an important role in pre-mRNA splicing and mitotic progression in mammalian and yeast cells. In honu mutants, cyclic transcripts that are normally cleared rapidly during segmentation accumulate instead, and only about half the normal number of segments form. Using an intron-based probe that distinguishes nascent from mature her1 transcript by in situ hybridization, we find that transcriptional regulation of her1 is normal in honu mutants, and surprisingly, RT-PCR analysis indicates that her1 transcript is spliced normally. Therefore, her1 and likely other cyclic transcripts accumulate post-splicing upon loss of Cdc5l. High resolution imaging of her1 mRNA in honu mutants reveals a pronounced nuclear accumulation defect, suggesting that mRNA export is compromised and may arise due to improper pre-mRNA processing. We are currently investigating the nature and extent of mRNA processing defects in honu mutants to understand the developmental role of Cdc5l and to provide insight into why certain tissues and/or transcripts are particularly sensitive to loss of a core component of the spliceosome.
Keywords: Splicing, Development