The alphaCGRP sequence was disrupted by replacement of exon 5 with a PGK-neo cassette leaving the calcitonin (CT) sequence uninterrupted. RT-PCR analysis confirmed the absence of alphaCGRP expression in mutant mice while CT expression appears unaffected. Immunohistochemical analysis did not detect alphaCGRP protein in the spinal cords of mutant animals, but thyroid gland samples stain positive for CT.