text: GPR126 is necessary for Schwann cell myelination. Knockouts of this adhesion GPCR in both Danio rerio and Mus musculus result in an arrest at the promyelinating stage. Schwann cells arise from the neural crest, which migrates to peripheral nerves to form either myelinating or non-myelinating cells.  In GPR126 knockouts, these precursor cells develop to the promyelinating stage, where they have wrapped approximately 1.5 times.  Myelination is arrested at the promyelinating stage and in fish no myelin basic protein can be detected.  In fish this can be rescued by adding forskolin during development, which rescues myelin basic protein expression.