The correct connection of neurons is a critical part of neural development. The growth of neurons to their targets has been shown to require dozens of genes in the nematode, Caenorhabditis elegans. One of those genes is uncoordinated-44 (
unc-44) that encodes a series of ankyrin proteins. Previous studies showed that the large AO13 ankyrin isoform, rather than the other isoforms is required for proper axonal guidance. To determine which molecules interact with UNC-44 and whether they form a signal transduction complex, the yeast two-hybrid system has been used. One bait, pDD5, was constructed by inserting the DNA coding for the carboxyl domain of AO13 ankyrin into plasmid pAS2-1. Transformation of pDD5 into yeast cells containing C. elegans library plasmids yielded positive colonies that were picked and DNA sequenced. Four of ten clones analyzed encode W08G11.4 which is related to the B56 or B' regulatory subunit of phosphatase 2A (PP2A). PP2A has been shown to be involved in many cellular processes by combining a limited number of catalytic (C) and adapter (A) subunits with a variety of regulatory (B, B', B'', and B''') subunits. The B-type subunits of PP2A determine the substrate specificity of PP2A phosphatase. PP2A containing the B56 regulatory subunit has been reported to be involved in axonal guidance in Drosophila.