MAST4 (microtubule associated serine/threonine kinase family member 4) is a serine/threonine protein kinase containing a kinase domain and a PDZ domain that plays critical roles in cellular signaling and cytoskeletal regulation 1. The protein functions as a key regulator of primary ciliary resorption by phosphorylating Tctex-1 at threonine 94, which promotes actin remodeling and ciliary pocket membrane endocytosis during cell cycle-dependent ciliary disassembly 2. MAST4 is involved in multiple signaling pathways, including interaction with PTEN to regulate the PI3K-Akt-mTOR pathway and downstream cytokine expression 3. In pancreatic cancer, nuclear MAST4 interacts with AKT3 to phosphorylate FOXO3, promoting chemoresistance and poor prognosis 4. The gene shows estrogen-responsive expression and negatively regulates myeloma bone disease through modulation of osteoclast formation 3. Clinically, de novo variants in MAST4 are associated with neurodevelopmental disorders characterized by developmental delay and infantile spasms 5, and variants contribute to genetic generalized epilepsy susceptibility 6. MAST4 expression is regulated by glucocorticoids and DNA methylation patterns associated with diet quality, linking it to cardiometabolic health 78.