The MAST family of serine/threonine kinases has been implicated in a spectrum of human neurodevelopmental disorders, however, little is known about their biological function, regulation or targets. Mutations in MAST1 are associated with Mega-Corpus-Callosum Syndrome with Cerebellar Hypoplasia and Cortical Malformations (MCC-CH-CM), which is characterized by enlargement of the corpus callosum, epilepsy, and severe cognitive and motor impairment. We have undertaken whole brain phosphoproteomics on two unique mouse models (L278del, G510S) that recapitulate muliple aspects of this disease at P0. We identify peptides that are differentially phosphorylated in these mice.