Our seemingly diverse interests are all connected: We have discovered the requirement of selenoproteins for appropriate brain function. Our research is now focused on delineating how GABAergic interneurons specifically depend on selenoproteins. The codon-specific analysis of selenoprotein translation brought us to the analysis of the impact of tRNA isopentenylation on translation and its effects on brain development. Thyroid hormones are required for development and function of the brain. We study mechanisms of regulation of local thyroid hormone availability involving hormone transport and local deiodination. Several of our mouse models display epilepsy and movement disorders and are related to rare diseases in humans.