Cell type signaling specificity of the neurodevelopmental disease-associated DYRK1A kinase

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PROJECT SUMMARY/ABSTRACT Mutations in DYRK1A, which encodes a ubiquitously expressed kinase that antagonizes the calcium- dependent calcineurin (CaN)/NFAT signaling pathway, have been reproducibly linked to neurodevelopmental disease. DYRK1A loss of function has been associated with syndromic intellectual disability and autism spectrum disorders (ASD), and increased DYRK1A activity is thought to underlie aspects of Down Syndrome pathophysiology. These genetic clues underscore DYRK1A dosage-dependent regulation of nervous system development; however, the precise mechanisms by which DYRK1A executes its roles in the developing brain remain poorly understood. Our long-term goal is to understand how DYRK1A acts in specific cell types of the embryonic cerebral cortex to influence the commitment of neural stem and progenitor cells to specific neural fates. In the proposed studies, we focus on NFAT-dependent transcriptional mechanisms as primary effectors of DYRK1A activity in neural stem cells and their progeny. We have found that deleting Dyrk1a specifically in the developing cortex differentially impacts calcium signaling in neural stem/progenitor cells and neurons of both the mouse and human. Loss of one or both copies of Dyrk1a results in dose-dependent cortical thinning, depletion of radial glia stem cells, reduced astrocyte abundance, neuronal cell death, and shifts in excitatory neuron differentiation. Our previous studies uncovered similar changes in the generation of excitatory neuron subtypes resulting from the mutation in the Cav1.2 calcium channel that gives rise to the syndromic ASD Timothy Syndrome. Imbalances in these same excitatory neuron types have also been linked to neuropsychiatric syndromes and channelopathies, hinting that calcium-regulated molecular mechanisms may represent a core substrate underlying cellular phenotypes in ASD and other neurodevelopmental disorders. In line with this idea, we have found that the effects of Dyrk1a deletion during cortical development are propagated by CaN/NFAT signaling, and we have used CUT&RUN sequencing to begin to identify targets of NFAT transcription factors in the developing brain. Building on these strong published and preliminary findings, the central objective of this proposal is to define cell type-specific mechanisms by which DYRK1A regulates the development of the cortex. The proposed research tests the ideas that NFAT transcriptional targets underlie deficits in stem cell maintenance and differentiation resulting from cortex-specific Dyrk1a inactivation (AIM 1), that DYRK1A and calcium signaling through CaN/NFAT play key roles in cortical astrogliogenesis (AIM 2), and that cell type-specific NFAT targets contribute to DYRK1A signaling specificity (AIM 3). These studies will build a foundation for future research expanding our knowledge of how calcium signaling regulates brain development and how ubiquitously expressed disease-relevant genes exert specific functions in different cell types. Our results will also provide therapeutic entry points for convergent intracellular mechanisms driving neurodevelopmental disorders.