Meeting Abstract

S9.11  Wednesday, Jan. 6  Cracking the code of the spiralian quartets: RNA segregation in Ilyanassa LAMBERT, J D; Univ. of Rochester dlamber2@mail.rochester.edu

In spiralian embryos, the animal-vegetal axis is divided into tiers of cells with similar developmental potentials. These tiers are quartets of micromeres that are born from the macromeres in the same cleavage cycle, or sets of four equivalent progeny of the members of a quartet. Different tiers have very different cleavage patterns and cell fates, but how these differences arise is unknown. In the Ilyanassa embryo, many RNAs are specifically localized to centrosomes and segregated during these cleavage cycles, and RNAs are segregated in a tier-specific way. Recent results from our lab (presented elsewhere) demonstrate the functional significance of segregated RNAs for the cells that inherit them. We have been examining the mechanisms that specifically localize and segregate RNAs to particular tiers. For two RNAs that are specifically localized to the first quartet, we mapped similar stem loop regions that are capable of recapitulating the localization patterns of the transcript, and found that deletion of these prevents RNA localization. Addition of a stem loop to a normally unlocalized RNA is sufficient to localize it. The same elements that mediate centrosomal localization are also segregated into the first quartet. We have also found that there is a distinct window in late cytokinesis and early interphase when localization to the centrosome can occur, and if an RNA is introduced after this window it will not localize to the interphase centrosomes or be segregated to the 1st quartet micromeres. These results suggest a model where RNAs destined for segregation to a particular tier are localized to the mother cell centrosome at least in part by specific secondary structural elements, and the diversity of RNA localization patterns observed is generated by combinations of different elements in particular transcripts.