Dlx2 homeobox gene transcriptional regulation of Trkb neurotrophin receptor expression during mouse retinal development.
Dlx homeobox genes are first expressed in embryonic retina at E11.5. The Dlx1/Dlx2 null retina has a reduced ganglion cell layer (GCL), with loss of late-born differentiated retinal ganglion cells (RGCs) due to increased apoptosis. TrkB signaling is proposed to regulate the dynamics of RGC apoptosis throughout development. DLX2 expression markedly precedes the onset of TrkB expression in the GCL; TrkB co-expression with Dlx2 and RGC markers is well-established by E13.5. In the Dlx1/Dlx2 null retina, TrkB expression is significantly reduced by E16.5. We demonstrated that DLX2 binds to a specific region of the TrkB promoter in retinal neuroepithelium during embryogenesis. In vitro confirmation and the functional consequences of DLX2 binding to this TrkB regulatory region support TrkB as a Dlx2 transcriptional target. Furthermore, ectopic Dlx2 expression in retinal explants activates TrkB expression and Dlx2 knockdown in primary retinal cultures results in reduced TrkB expression. RGC differentiation and survival require the coordinated expression of transcription factors. This study establishes a direct transcriptional relationship between a homeodomain protein involved in RGC differentiation and a neurotrophin receptor implicated in RGC survival. Signaling mediated by TrkB may contribute to survival of late-born RGCs whose terminal differentiation is regulated by Dlx gene function.
de Melo
Jimmy
J
Department of Human Anatomy and Cell Science, University of Manitoba, Winnipeg, Manitoba, Canada.
Zhou
Qing-Ping
QP
Zhang
Qi
Q
Zhang
Shunzhen
S
Fonseca
Mario
M
Wigle
Jeffrey T
JT
Eisenstat
David D
DD
D025042:Amacrine Cells / Q000378:metabolism; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002478:Cells, Cultured; D004742:Enhancer Elements, Genetic; D018507:Gene Expression Regulation, Developmental; D018398:Homeodomain Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000235:genetics* / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D011401:Promoter Regions, Genetic; D011505:Protein-Tyrosine Kinases / Q000235:genetics* / Q000378:metabolism; D034622:RNA Interference; D012160:Retina / Q000196:embryology* / Q000378:metabolism; D012165:Retinal Ganglion Cells / Q000378:metabolism*; D014157:Transcription Factors / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation; D020813:Receptor, trkB
D018398:Homeodomain Proteins; D008562:Membrane Glycoproteins; D011505:Protein-Tyrosine Kinases; D014157:Transcription Factors; C088334:Distal-less homeobox proteins; C064371:Ntrk2 protein, mouse; D020813:Receptor, trkB