Winnier AR, Meir JY, Ross JM, Tavernarakis N, Driscoll M, Ishihara T, Katsura I, Miller DM. UNC-4/UNC-37-dependent repression of motor neuron-specific genes controls synaptic choice in Caenorhabditis elegans.
Genes Dev 1999;
13:2774-86. [PMID:
10557206 PMCID:
PMC317130 DOI:
10.1101/gad.13.21.2774]
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Abstract
The UNC-4 homeoprotein and the Groucho-like corepressor UNC-37 specify synaptic choice in the Caenorhabditis elegans motor neuron circuit. In unc-4 mutants, VA motor neurons are miswired with inputs from interneurons normally reserved for their lineal sisters, the VB motor neurons. Here we show that UNC-4 and UNC-37 function together in VA motor neurons to repress VB-specific genes and that this activity depends on physical contact between UNC-37 and a conserved Engrailed-like repressor domain (eh1) in UNC-4. Missense mutations in the UNC-4 eh1 domain disrupt interactions between UNC-4 and UNC-37 and result in the loss of UNC-4-dependent repressor activity in vivo. A compensatory amino acid substitution in UNC-37 suppresses specific unc-4 alleles by restoring physical interactions with UNC-4 as well as UNC-4-dependent repression of VB-specific genes. We propose that repression of VB-specific genes by UNC-4 and UNC-37 is necessary for the creation of wild-type inputs to VA motor neurons. The existence of mammalian homologs of UNC-4 and UNC-37 indicates that a similar mechanism could regulate synaptic choice in the vertebrate spinal cord.
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