The Groucho-like transcription factor UNC-37 functions with the neural specificity gene unc-4 to govern motor neuron identity in C. elegans

Abstract

Groucho and Tup1 are members of a conserved family of WD repeat proteins that interact with specific transcription factors to repress target genes. Here we show that mutations in WD domains of the Groucho-like protein, UNC-37, affect a motor neuron trait that also depends on UNC-4, a homeodomain protein that controls neuronal specificity in Caenorhabditis elegans. In unc-4 mutants, VA motor neurons assume the pattern of synaptic input normally reserved for their lineal sister cells, the VB motor neurons; the loss of normal input to the VAs produces a distinctive backward movement defect. Substitution of a conserved residue (H to Y) in the fifth WD repeat in unc-37(e262) phenocopies the Unc-4 movement defect. Conversely, an amino acid change (E to K) in the sixth WD repeat of UNC-37 is a strong suppressor of unc-37(e262) and of specific unc-4 missense mutations. We have previously shown that UNC-4 expression in the VA motor neurons specifies the wild-type pattern of presynaptic input. Here we demonstrate that UNC-37 is also expressed in the VAs and that unc-37 activity in these neurons is sufficient to restore normal movement to unc-37(e262) animals. We propose that UNC-37 and UNC-4 function together to prevent expression of genes that define the VB pattern of synaptic inputs and thereby generate connections specific to the VA motor neurons. In addition, we show that the WD repeat domains of UNC-37 and of the human homolog, TLE1, are functionally interchangeable in VA motor neurons which suggests that this highly conserved protein domain may also specify motor neuron identity and synaptic choice in more complex nervous systems.

unc-37/Groucho and lsy-22/AES repress Wnt target genes in C. elegans asymmetric cell divisions

“…This allows the study of the roles of each subfamily member without redundancy precluding analysis. Previous work on unc-37/Groucho and lsy-22/AES shows they are widely, if not constitutively, expressed from the 4-cell embryonic stage through larval stage 4 (Flowers et al, 2010; Pflugrad, Meir, Barnes, & Miller, 1997). C. elegans Groucho and AES homologs also regulate proper cell fate decisions.…”

Transcription Factors That Control Behavior—Lessons From C. elegans

“…Synaptic patterns in the VA and VB neurons are controlled by the TFs UNC-4, UNC-37, and CEH-12 (Von Stetina et al, 2007). UNC-4 and UNC-37 are expressed in VA neurons and suppress CEH-12, a homeobox TF that regulates VB specific genes (Miller and Niemeyer, 1995;Pflugrad et al, 1997). CEH-12 is only expressed in the VB motor neurons and is likely required for generating the VB synaptic pattern (Von Stetina et al, 2007).…”

CO2and compressive immobilization of C. elegans on-chip

“…The integrated unc-4::gpf strain 35 was used to monitor GFP fluorescence from the VA motorneurons. Wild type worms were C. elegans Bristol strain N2.…”