Meeting Abstract

91.4  Thursday, Jan. 7  Asymmetric RNA segregation as a patterning mechanism in Ilyanassa RABINOWITZ, J.S.*; LAMBERT, J.D.; University of Rochester jrabinow@mail.rochester.edu

Asymmetric cell divisions are required by multicellular organisms to generate tissue diversity during early development. Spiral cleaving embryos undergo highly stereotyped divisions where large macromeres divide asymmetrically to produce several small micromeres with specified fates. In at least one representative of this group, the snail Ilyanassa, RNAs localize to macromere centrosomes and become asymmetrically segregated into the daughter micromeres. ~3% of RNAs in Ilyanassa undergo this mode of asymmetric cell division, suggesting that these RNAs may be important for normal micromere development. We have been examining one segregated RNA, IoLR5 (Ilyanassa obsoleta Localized RNA 5), to see if it is required for the development of the cells that inherit it. IoLR5 RNA segregates to the first quartet micromeres, which are specified to become the eyes and parts of the velum. The IoLR5 protein is translated in cells from this lineage and is later detected in specific cells in the developing head near the eye primordia and several other regions of the head and velum. Knockdown of translation using morpholino oligonucleotides (MOs) has demonstrated a role for IoLR5 in development of the eyes and the velum. Injected animals typically develop with either 1 or 0 eyes and small velar lobes. The eye and velum defects seen in IoLR5 MO injected animals are rescued by coinjection of a MO-resistant IoLR5 mRNA. As IoLR5 RNA segregates to the first quartet during development, this finding provides evidence that asymmetrically segregated RNAs are important for the lineages that inherit them.