The homeobox gene irx1a is required for the propagation of the neurogenic waves in the zebrafish retina.
Neurogenesis in the compound eyes of Drosophila and the camera eyes of vertebrates spreads in a wave-like fashion. In both phyla, waves of hedgehog expression are known to drive the wave of neuronal differentiation. The mechanism controlling the propagation of hedgehog expression during retinogenesis of the vertebrate eye is poorly understood. The Iroquois homeobox genes play important roles in Drosophila eye development; they are required for the up-regulation of hedgehog expression during propagation of the morphogenetic furrow. Here, we show that the zebrafish Iroquois homolog irx1a is expressed during retinogenesis and knockdown of irx1a results in a retinal phenotype strikingly similar to those of sonic hedgehog (shh) mutants. Analysis of shh-GFP transgene expression in irx1a knockdown retinas revealed that irx1a is required for the propagation of shh expression through the retina. Transplantation experiments illustrated that the effects of irx1a on shh expression are both cell-autonomous and non-cell-autonomous. Our results reveal a role for Iroquois genes in controlling hedgehog expression during vertebrate retinogenesis.
Cheng
Chi Wa
CW
Department of Biology and Chemistry, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong, China.
Yan
Carol Hiu Mei
CH
Hui
Chi-chung
CC
Strähle
Uwe
U
Cheng
Shuk Han
SH
D000818:Animals; D030801:Animals, Genetically Modified; D002454:Cell Differentiation; D005123:Eye / Q000196:embryology*; D005128:Eye Diseases / Q000235:genetics / Q000378:metabolism; D005346:Fibroblast Growth Factors / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D053823:Hedgehog Proteins / Q000235:genetics / Q000378:metabolism; D018398:Homeodomain Proteins / Q000235:genetics* / Q000378:metabolism; D012160:Retina / Q000166:cytology / Q000196:embryology* / Q000378:metabolism; D012165:Retinal Ganglion Cells / Q000378:metabolism*; D015398:Signal Transduction; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D015027:Zebrafish; D029961:Zebrafish Proteins / Q000235:genetics* / Q000378:metabolism
D053823:Hedgehog Proteins; D018398:Homeodomain Proteins; D014157:Transcription Factors; D029961:Zebrafish Proteins; C501593:irx1a protein, zebrafish; D005346:Fibroblast Growth Factors