Meeting Abstract

P1.48  Thursday, Jan. 3  The role of transcription in centrosomal localization during development of the mud snail Ilyanassa obsoleta. COOLEY, J.R.*; NAGY, L.M.; University of Arizona; University of Arizona cooley@u.arizona.edu

Through a unique developmental process in the marine mud snail, Ilyanassa obsoleta, mRNAs are asymmetrically inherited via centrosomal localization by the daughter micromere (Lambert and Nagy, 2002). The regulatory control of this dynamic localization is unknown. To investigate whether zygotic transcription is required for any aspect of the mRNA localization, we blocked transcription with Actinomycin-D (Act-D) and assayed mRNA localization and abundance using in situ hybridization and Real Time PCR (RT-PCR). If transcription were required for the dynamic pattern of localization, we would expect to see an absence of centrosomally localized mRNA and reduced levels of mRNA when treated with Act-D. We assayed a total of 11 genes, including Ilyanassa Wnt, Hox, Dpp, Eve, Tld and 40S orthologs for their spatial and quantitative dynamics through early development. Of these, we found that 6 are present at the 1-cell stage and are therefore likely maternally supplied. Of the remaining 5 genes, 3 are transcribed by 45 hours of development and the remaining 2 were transcribed by 96 hours of development. Surprisingly, all 6 of the mRNAs at the 1-cell stage are present at relatively similar levels to one another. We also found that while transcription is not required to maintain overall levels of mRNA, transcription is required to maintain centrosomal localization of mRNAs in some, but not all, cell lineages. Lastly, we found that centrosomal localization is not required to protect messages from degradation. Taken together, these data suggest that localization of mRNA to the centrosome is not dependent on concentration, suggesting that there is an active mechanism for mRNA localization.