Submitted to: Journal of Comparative Neurology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 12, 1997
Publication Date: N/A
Interpretive Summary: The development of the avian brain is dependent on many factor throughout adulthood. Many different cell types proliferate and migrate to different areas of the developing brain. In this study the effect of and tissue distribution of insulin-like growth factors 1 and 2 on specific cell types in the avian brain were assessed. It was determined that IGF-1 was found in radial cells, with IGF-2 in other cell types. Both growth factors promoted the migration of neurons from one area to another. These results demonstrated that IGF-1 regulates neuronal recruitment in the adult brain. These results will be of interest to other basic scientists.
In the adult songbird forebrain, neurons continue to be produced from precursor cells in the subependymal zone (SZ), from which they migrate upon radial guide fibers. The new neurons and their radial cell partners may co-derive from a common SZ progenitor, which may be the radial cell itself. We asked whether radial cells might provide trophic support for the migration or survival of newly generated neurons. We focused upon the insulin-like growth factors IGF-I and IGF-2, which have previously been shown to support the survival and differentiation of neural progenitor cells. We found that IGF-I immunoreactivity was expressed heavily by adult finch radial cells and their fibers. IGF-2 was expressed by parenchymal, astrocytes, and exhibited no radial cell expression. Despite their distinct distributions, IGF-I and IGF-2 exerted similar trophic effects on finch SZ cells in vitro. However, neither factor extended neuronal survival. These results suggest that in neurogenic regions of the adult avian forebrain, IGF-1 acts as a radial cell-associated neuronal specification and/or departure factor, which may serve to regulate neuronal recruitment into the adult brain.