CORTICAL FOXP2 · Functional role of Foxp2 and Caspr2 in the cortex

The identification of genomic variants associated with common neurodevelopmental syndromes is rapidly advancing. Recent estimates suggest that hundreds of genes are likely to contribute to susceptibility to a specific syndrome. Inherent in this hypothesis is the convergence of associated variants on common molecular networks mediating specific endophenotypes such as disturbed speech and language development across clinically distinct categories. Highly penetrant mutations account for only a fraction of language-related pathologies but are essential for understanding the common neurobiological underpinnings of these disorders.Rare mutations affecting the FOXP2 transcription factor cause a monogenic speech and language disorder. Mice carrying an identical point mutation to that observed in affected patients have been generated (Foxp2+/R552H mice) but the functional significance of Foxp2 expression in cortical neurons in not known. We will characterize Foxp2-expressing cortical neurons and investigate the functional impact of the mutation at the cellular, synaptic and network level. Furthermore, FOXP2 binds to and dramatically down-regulates CNTNAP2, a gene that encodes the neurexin Caspr2 and was recently associated with several language disorders. Using CNTNAP2+/- mice we will assess the functional consequences of decreased Caspr2 expression in Foxp2-expressing neurons. We will also attempt to rescue the cellular phenotype observed in Foxp2+/R552H mice by reexpressing Foxp2 or downregulating its target genes in adult animals. Finally, Foxp2 is expressed in a fraction of neurons derived from human induced pluripotent stem cells (iPSC). Using iPSC-derived neurons as disease models is challenging since different neuronal subtypes are differentially sensitive to a mutation. We will FACS-sort and characterize Foxp2+ neurons derived from human iPSCs to establish a cellular model of the Foxp2-related disorder.