Regulation of Gene Expression by Thyroid Hormone in Cultured Astrocytes: Transcriptional Targets and Factors Influencing the Genomic Response

Astrocytes mediate the action of thyroid hormone in the brain on other neural cells through the production of the active hormone triiodothyronine (T3) from its precursor thyroxine (T4). T3 has also many effects on the astrocytes in vivo and in culture, but whether these actions are directly mediated by transcriptional regulation is not clear. In this work, we have analyzed the genomic response to T3 of cultured astrocytes isolated from the postnatal mouse cerebral cortex, using RNA sequencing. Cultured astrocytes express relevant genes of thyroid hormone metabolism and action encoding type 2 deiodinase (Dio2), Mct8 transporter (Slc16a2), T3 receptors (Thra1 and Thrb), and nuclear corepressor (Ncor1) and coactivator (Ncoa1). T3 changed the expression of 668 genes (4.5% of expressed genes), of which 117 genes (0.8% of expressed genes) were primary, transcriptional responses. The Wnt and Notch pathways were down-regulated at the post-transcriptional level. Comparison with the effect of T3 on astrocyte-enriched genes in mixed cerebrocortical cultures isolated from fetal cortex revealed that the response to T3 is influenced by the degree of astrocyte maturation, and that in agreement with its physiological effects, T3 promotes the transition between the fetal and adult patterns of gene expression. To analyze the genomic response to T3 of cultured astrocytes, isolated from the postnatal mouse cerebral cortex, using RNA sequencing.