A novel basic helix-loop-helix (bHLH) transcriptional repressor, NeuroAB, expressed in bipolar and amacrine cells in the chick retina.
Basic helix-loop-helix (bHLH) transcription factors are implicated in cell fate determination and differentiation in neurogenesis. We identified a novel chick bHLH transcription factor, NeuroAB. A phylogenetic tree prepared from bHLH sequences suggested that NeuroAB belongs to the BETA3 group in the Atonal-related protein family (ARPs). In situ hybridization and immunostaining indicated that NeuroAB is expressed predominantly in postmitotic bipolar cells and GABAergic amacrine cells in the retina. Reporter and DNA pull down assays indicated that NeuroAB functions as a transcriptional repressor by binding to the E-box sequence, and its activity is modulated by phosphorylation at a specific serine residue that fits the consensus phosphorylation site for glycogen synthase kinase 3beta (GSK3beta). Since members of the BETA3 group possess this consensus site, it is suggested that their activities are commonly regulated by GSK3beta or other kinases bearing the same substrate specificity. We found that the expression of GSK3beta is spatially and temporally regulated in the developing retina; its strong expression was observed in ganglion cells from E8 and a subset of amacrine cells from E12. These findings suggest that NeuroAB is involved in the maturation and maintenance of bipolar cells and GABAergic amacrine cells and regulation by GSK3beta plays an important role in retinogenesis.
Ohkawara
Takeshi
T
Division of Molecular Neurobiology, National Institute for Basic Biology, and Department of Molecular Biomechanics, Graduate University for Advanced Studies, Okazaki 444-8787, Japan.
Shintani
Takafumi
T
Saegusa
Chika
C
Yuasa-Kawada
Junichi
J
Takahashi
Masakazu
M
Noda
Masaharu
M
D025042:Amacrine Cells / Q000166:cytology / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D002642:Chick Embryo / Q000033:anatomy & histology / Q000502:physiology; D004268:DNA-Binding Proteins / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D038362:Glycogen Synthase Kinase 3 / Q000235:genetics / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D018257:Helix-Loop-Helix Motifs; D006801:Humans; D017403:In Situ Hybridization; D008969:Molecular Sequence Data; D010802:Phylogeny; D011485:Protein Binding; D012097:Repressor Proteins / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D012160:Retina / Q000166:cytology* / Q000196:embryology / Q000378:metabolism; D014158:Transcription, Genetic
D004268:DNA-Binding Proteins; D012097:Repressor Proteins; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; D038362:Glycogen Synthase Kinase 3