unc-3 encodes the C. elegans orthologue of a family of variant mammalian HLH transcription factors, the OLF/Ebf proteins, which determine aspects of terminal differentiation in neuronal and hematopoietic cells. Mutations in
unc-3 result in a defect in VA and VB motor neuron differentiation such that VA and VB neurons can adopt a VC-like fate as assayed by expression of a Plin11gfp reporter and the FMRF-amide neuropeptide, two characteristics of VC neurons.
unc-3 is expressed in ASI chemosensory neurons and ventral nerve cord motor neurons. To examine the role of UNC-3 during neuronal differentiation, we used a yeast two-hybrid assay to identify proteins that interact with the C-terminal region of UNC-3, which contains the single helix domain of UNC-3. We identified F11A10.3, a protein that contains a RING domain. We have begun to characterize the F11A10.3 gene and the interaction between UNC-3 and F11A10.3.Using the two hybrid assay we have mapped the interaction domain in F11A10.3 to the RING domain. Significance of the interaction has not yet been elucidated. The F11A10.3 protein is encoded by the downstream gene in a two gene operon. We have obtained a deletion allele,
n4275, which removes the start codon and the first 133 amino acids of the predicted protein.
n4275 mutants are homozygous viable, Egl and Mab. HSN-specific transcriptional GFP reporter showed that the HSNs are abnormal in
n4275 mutants, a possible explanation for the Egl phenotype. In addition, ray 1 in the mail tail is anteriorly positioned causing the Mab phenotype. A similar defect was reported in mutants of the Semaphorin/Plexin pathway that is required for the migration of ray 1. The migration defects of both HSNs and ray 1 suggest a role for F11A10.3 in or parallel to the Smp/Plx pathway for migration of the affected cells. We are currently trying to find the role of F11A10.3 in the Smp/Plx pathway. Transgenic worms expressing a GFP translational reporter of F11A10.3 gene showed that F11A10.3 is expressed in the nuclei of most cells and particularly in the nucleoli of a subset of hypodermal nuclei. Ubiquitous expression allows doing biochemical analysis of the protein. After confirming the expression pattern with antibody staining we will try to purify the complex and identify the partners of F11A10.3.