Genes repressed by GDNF
The genes down-regulated by the glial cell-line-derived neurotrophic factor may account for the factor's inhibition of neurite growth.
Glial cell line-derived neurotrophic factor (GDNF) has differential trophic effects on postnatal or embryonic dorsal root ganglion (DRG) cells. In the December 4 Proceedings of the National Academy of Sciences, Sten Linnarsson and colleagues from the Karolinska Institute in Stockholm, Sweden, describe the use of oligonucleotide microarrays to analyse gene regulation by GDNF signalling (Proc Natl Acad Sci USA 2001, 98:14681-14686).
They cultured DRGs from embryonic or postnatal mice and treated them with GDNF. Microarray analysis identified 195 genes that were regulated by GDNF. Linnarsson et al. also found 310 genes that changed more than five-fold between samples taken at embryonic day 14 and postnatal day 14 (39% of which were also GDNF-regulated). A number of genes related to the cytoskeleton or cell adhesion were down-regulated by GDNF at both ages.
This result prompted Linnarsson et al. to measure the effect of GDNF on neurite extension, and they noted a marked suppression of neurite initiation and growth by the neurotrophic factor.