Meeting Abstract

P3.48  Wednesday, Jan. 6  IoTis11 is Segregated into Ventral Third Quartet Cells of the Ilyanassa Embryo and is Required for Their Development CHAN, X. Y.*; LAMBERT, J. D.; University or Rochester; University of Rochester xinyichan@gmail.com

During embryogenesis, all animals employ asymmetric cell division to specify cell fates, but there are relatively few cases where the functionally relevant segregated molecules have been identified, and it is not clear if a conserved mechanism underlies asymmetric cell division across animal kingdom. Spiralian embryos seem to be particularly reliant on asymmetric cell division for embryonic patterning, since most early divisions are unequal and generate cells with distinct fates. In Ilyanassa embryos, RNA segregation is widespread, but it is unknown whether this has functional consequences for embryonic patterning. IoTis11 is a zinc finger-encoding transcript that was recovered in a screen for segregated RNAs in early cell divisions. It is segregated into 3rd quartet micromeres and restricted to 3a and 3b cells of the 3rd quartet, suggesting that IoTis11 is important for normal development of these cells. Ablation of 3a and 3b always prevented the development of the esophagus and digestive glands, and frequently impaired development of the velum, foot and stomodeum. Lineage tracing shows that 3a and 3b directly contribute to all these organs except the digestive glands, suggesting that previously unrecognized signaling from 3a and 3b is necessary for development of these organs. Knockdown of IoTis11 by morpholino generated larvae with similar phenotypes as 3a and 3b ablation: they had no esophagus, occasionally lacked digestive glands and had abnormal velum, foot, and stomodeum. This result shows that IoTis11, a segregated RNA, is specifically required for differentiation of 3a and 3b cells, and supports the idea that widespread RNA segregation in the Ilyanassa embryo is important for establishing the normal pattern of cell fates.