Part of exon and intron 2 were replaced with a neo cassette. The absence of transcript was confirmed by whole mount in situ hybridization using E8.5 embryos. An aberrant transcript lacking the 471 N-terminal amino acids is produced from an initiation site in exon 3. The lack of the full-length protein product and presence of a shorter peptide lacking the N-terminus was confirmed by western blot analysis on embryonic fibroblasts derived from E8.5 embryos.