HLH-14 is a C. elegans achaete-scute protein that promotes neurogenesis through asymmetric cell division.
Achaete-Scute basic helix-loop-helix (bHLH) proteins promote neurogenesis during metazoan development. In this study, we characterize a C. elegans Achaete-Scute homolog, HLH-14. We find that a number of neuroblasts express HLH-14 in the C. elegans embryo, including the PVQ/HSN/PHB neuroblast, a cell that generates the PVQ interneuron, the HSN motoneuron and the PHB sensory neuron. hlh-14 mutants lack all three of these neurons. The fact that HLH-14 promotes all three classes of neuron indicates that C. elegans proneural bHLH factors may act less specifically than their fly and mammalian homologs. Furthermore, neural loss in hlh-14 mutants results from a defect in an asymmetric cell division: the PVQ/HSN/PHB neuroblast inappropriately assumes characteristics of its sister cell, the hyp7/T blast cell. We argue that bHLH proteins, which control various aspects of metazoan development, can control cell fate choices in C. elegans by regulating asymmetric cell divisions. Finally, a reduction in the function of hlh-2, which encodes the C. elegans E/Daughterless bHLH homolog, results in similar neuron loss as hlh-14 mutants and enhances the effects of partially reducing hlh-14 function. We propose that HLH-14 and HLH-2 act together to specify neuroblast lineages and promote neuronal fate.
Frank
C Andrew
CA
Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720-3204, USA.
Baum
Paul D
PD
Garriga
Gian
G
D000595:Amino Acid Sequence; D000818:Animals; D030801:Animals, Genetically Modified; D001483:Base Sequence; D051792:Basic Helix-Loop-Helix Proteins; D019521:Body Patterning / Q000235:genetics; D017173:Caenorhabditis elegans / Q000196:embryology*; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism*; D002455:Cell Division / Q000502:physiology; D017124:Conserved Sequence; D017931:DNA Primers; D004625:Embryo, Nonmammalian / Q000502:physiology; D017353:Gene Deletion; D018257:Helix-Loop-Helix Motifs; D008969:Molecular Sequence Data; D009046:Motor Neurons / Q000166:cytology / Q000502:physiology; D005810:Multigene Family; D009420:Nervous System / Q000166:cytology / Q000196:embryology*; D009474:Neurons / Q000166:cytology / Q000502:physiology; D009475:Neurons, Afferent / Q000166:cytology / Q000502:physiology; D016133:Polymerase Chain Reaction; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
D051792:Basic Helix-Loop-Helix Proteins; D029742:Caenorhabditis elegans Proteins; D017931:DNA Primers; D014157:Transcription Factors; C483688:HLH-14 protein, C elegans; C106514:HLH-2 protein, C elegans