Regulation of Prospero protein cortical association and asymmetric localization. C.-Y. Peng ^1,2, H. Dou ², L. Manning ¹, S. Fuerstenberg ¹, R. Albertson ¹, C. Doe ¹. 1) Inst. of Neuroscience, Univ. of Oregon, Eugene, OR; 2) Neurscience Program, Univ. of Illinois, Urbana, IL.

   During Drosophila neurogenesis, stem cells called neuroblasts go through repeated asymmetric cell divisions that give rise to renewed neuroblasts and smaller precursors called ganglion mother cells (GMCs). Several molecules have been identified to asymmetrically segregated during all neuroblast divisions, one of which is the homeodomain transcription factor Prospero (Pros) protein. Pros is first found at the apical cortex in interphase neuroblasts, and is translocated to the basal cortex during mitosis. After the neuroblast division, the protein is found briefly at the GMC cell cortex before it enters the GMC nucleus and specifes the GMC cell fate.
   To identify new components involved in the cortical association and asymmetric localization of Pros, we screened through a collection of 2nd and 3rd chromosome deficiency lines for deletions causing mislocalization of Pros in mitotic neuroblasts using immunofluorescence and confocal microscopy. Out of 144 initial deficiency lines, we identified 10 that show mislocalization of Pros during neuroblast divisions. Excluding deficiencies that uncover known genes in the pathway (Miranda and Inscuetable) and genes involved in cell cycle (string and pebble), 5 deficiencies contain candidate or novel genes that may regulate Pros cortical association and asymmetric localization. We will present a summary of the screen as well as detailed analysis of one or more candidate genes from the screen.