Protein O-mannose kinase that specifically mediates phosphorylation at the 6-position of an O-mannose of the trisaccharide (N-acetylgalactosamine (GalNAc)-beta-1,3-N-acetylglucosamine (GlcNAc)-beta-1,4-mannose) to generate phosphorylated O-mannosyl trisaccharide (N-acetylgalactosamine-beta-1,3-N-acetylglucosamine-beta-1,4-(phosphate-6-)mannose). Phosphorylated O-mannosyl trisaccharide is a carbohydrate structure present in alpha-dystroglycan (DAG1), which is required for binding laminin G-like domain-containing extracellular proteins with high affinity. Only shows kinase activity when the GalNAc-beta-3-GlcNAc-beta-terminus is linked to the 4-position of O-mannose, suggesting that this disaccharide serves as the substrate recognition motif (By similarity). 3-O-[beta-D-GalNAc-(1->3)-beta-D-GlcNAc-(1->4)-alpha-D-Man]-L-Thr-[protein] + ATP = 3-O-[beta-D-GalNAc-(1->3)-beta-D-GlcNAc-(1->4)-(O-6-P-alpha-D-Man)]-Thr-[protein] + ADP + H(+) Hydrocephaly: mutant mice exhibit dome-shaped heads of varying severity. Surviving mutant mice display numerous behavioral abnormalities: tremors, and inverted screen testing show 5 of 8 falling off, suggesting impaired motor strength. Impaired sensorimotor gating/attention is suggested by decreased prepulse inhibition, and impaired learning/memory is detected with trace aversive conditioning testing. In testing nociception, decreased paw flinching is observed during both formalin phases, suggesting decreased sensitivity to acute and tonic pain. Histologically, the most obvious changes are hydrocephalus in 4 of 5 and cerebellar dysplasia in all 5. Abnormalities in neuronal migration are evident in other parts of the brain; in the cerebral cortex, there is disorganization of cortical neuron layers, and the dentate gyrus of the hippocampus has a scalloped appearance. The cerebellar dysplasia is characterized by multifocal disorganization of cerebellar cortical neurons, with clusters of external granular neurons being scattered on the surface of the cerebellum and multifocally within the molecular layer of the cerebellum. In some regions, there is incomplete separation of cerebellar folia, and Purkinje cell. neurons were occasionally found in the molecular layer. Belongs to the protein kinase superfamily. Ser/Thr protein kinase family. STKL subfamily. Although related to the Ser/Thr protein kinase family, has no protein kinase activity and acts as a mannose kinase instead.