Characterization of HAM-1 in the asymmetric division of C. elegans neuroblasts

HAM-1 (HSN abnormal migration) is a novel protein implicated in asymmetric cell division (ACD) of many C. elegans neuroblasts. HAM-1 is localized at cell peripheries and becomes asymmetrically distributed during mitosis. However, little is known about how it regulates ACDs. I have analyzed a series of protein truncations to determine sequences important for HAM-1 function and localization. Results indicate that the C-terminus is essential for function and N-terminal sequences are required for peripheral association. HAM-1 was also observed in the nucleus, a finding not previously reported. Deletion of a predicted nuclear localization signal partially disrupted nuclear targeting and function of the protein. This and other bioinformatics analyses suggest a possible nuclear role for HAM-1. Previous studies have proposed potential interactions between HAM-1 and the Wnt pathway. In this study, mutations in ham-1 and several Wnt signalling components were shown to produce opposing defects in the lineage generating the PLM neuron.