Glial enriched gene expression profiling identifies novel factors regulating the proliferation of specific glial subtypes in the Drosophila brain.
Bottom Line: Analysis of the differentially regulated genes in these tissues shows that the expression of known glial genes is significantly increased in both cases.Conversely, the expression of neuronal genes is significantly decreased.These studies provide new insight into the genes and molecular pathways that regulate the proliferation of specific glial subtypes in the Drosophila post-embryonic brain.
Affiliation: Wolfson Centre for Age-Related Diseases, King's College London, Guy's Campus, London SE1 1UL, UK.Show MeSH
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Mentions: Although several of the genes whose expression was significantly increased in both HtlACT and InR overexpressing CNS tissue had been previously shown to function in glia, we sought to experimentally test the efficacy of the microarray datasets as a source of genes that are expressed in cortex glia and/or surface glia (perineurial and sub-perineurial glia) in the brain. We focused on TFs, as these frequently play important roles in gliogenesis. The expression of 21 TFs was significantly increased in HtlACT overexpressing tissue (Table 1), while the expression of 10 TFs was significantly increased in InR overexpressing tissue (Table 2). Fifteen of the TFs whose expression was increased in HtlACT overexpressing tissue were not increased in InR tissue (Table 1), while four (kni, kay, Usf and ci) were unique to InR overexpressing tissue (Table 2). We tested antibodies against several of the TFs identified (Dorsal, Krüppel, Knirps, cubitus interruptus, FoxO and Mef2), but these gave either weak staining or high background staining in the larval brain (data not shown). However, a GFP fusion of kayak showed expression in both cortex and surface glia in the larval brain (Fig. 3A). Also, a lacZ enhancer trap in hairy (hE11) showed clear β-galactosidase expression specifically in cortex glia (Fig. 3B). Moreover, inhibition of glial proliferation by knock-down of htl using repo-Gal4 caused a dramatic reduction in the number of hairy expressing glia (Fig. 3C). These results further validate the glial enriched gene expression datasets as a source of glial-expressed genes and also as a means of identifying genes whose expression is specific at least to cortex glia.
Affiliation: Wolfson Centre for Age-Related Diseases, King's College London, Guy's Campus, London SE1 1UL, UK.