Transforming growth factor-beta and bone morphogenetic proteins: cooperative players in chick and murine programmed retinal cell death.
Transforming growth factor-beta (TGF-beta) and bone morphogenetic protein (BMP) are extracellular molecules known to mediate programmed cell death (PCD) in the developing retina. In the present study, we investigated the expression profiles and activity levels of ligands and receptors of the TGF-beta and BMP4 family during the physiological PCD periods of the developing chick and mouse retina and possible interactions of both proapoptotic molecules in mediating apoptosis in chick and murine retinal whole-mount cultures. Immunocytochemical double-labeling studies with the established ganglion cell marker Islet revealed overlapping expression patterns for TGF-beta and BMP4 ligands and receptors on the surface of retinal ganglion cells. The biphasic peak of activity and expression levels of TGF-beta and BMP4 ligands and receptors, revealed by Western blots and mink lung epithelial cell (MLEC) assays, coincided with the two main periods of retinal chick and murine PCD. In organotypic retinal cultures, we were able to increase apoptosis over basal levels by application of recombinant TGF-beta or BMP4. Double-factor treatment induced an additional increase of apoptosis, suggesting a cooperation of both proapoptotic pathways. A significant increase in the number of apoptotic cells in the ganglion cell layer was observed in a TUNEL staining of retinal whole mounts treated with recombinant TGF-beta or BMP4, suggesting a concerted action of both factors in triggering ganglion cell death. Blockage experiments revealed that both pathways do not interact at the ligand, receptor, or Smad protein level but converge at the transcriptional level of the TGF-beta immediate-early response gene TIEG and the transcriptional coactivator Gcn5.
Franke
Andreas G
AG
Department of Neuroanatomy, Center of Anatomy, University of Goettingen, 37075 Goettingen, Germany.
Gubbe
Christian
C
Beier
Marion
M
Duenker
Nicole
N
D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D015153:Blotting, Western; D019485:Bone Morphogenetic Proteins / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000096:biosynthesis; D002642:Chick Embryo; D004268:DNA-Binding Proteins / Q000096:biosynthesis; D015870:Gene Expression; D020869:Gene Expression Profiling; D051548:Histone Acetyltransferases / Q000096:biosynthesis; D006801:Humans; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D051379:Mice; D009924:Organ Culture Techniques; D012160:Retina / Q000196:embryology*; D012165:Retinal Ganglion Cells / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014157:Transcription Factors / Q000096:biosynthesis; D016212:Transforming Growth Factor beta / Q000378:metabolism*
D019485:Bone Morphogenetic Proteins; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; D051548:Histone Acetyltransferases