Transforming growth factor-beta (TGF-beta) and programmed cell death in the vertebrate retina

Programmed cell death (PCD) is a precisely regulated phenomenon essential for the homeostasis of multicellular organisms. Developmental systems, particularly the nervous system, have provided key observations supporting the physiological role of PCD. We have recently shown that transforming growth factor-beta (TGF-beta) plays an important role in mediating ontogenetic PCD in the nervous system. As part of the central nervous system the developing retina serves as an ideal model system for investigating apoptotic processes during neurogenesis in vivo as it is easily accessible experimentally and less complex due to its limited number of different neurons. This review summarizes data indicating a pivotal role of TGF-beta in mediating PCD in the vertebrate retina. The following topics are discussed: expression of TGF-beta isoforms and receptors in the vertebrate retina, the TGF-beta signaling pathway, functions and molecular mechanisms of PCD in the nervous system, TGF-beta-mediated retinal apoptosis in vitro and in vivo, and interactions of TGF-beta with other pro- and anti-apoptotic factors.