This mutation was discovered in a screen of G3 progeny of N-ethyl, N-nitrosourea-treated male mice for morphological defects at embryonic day (e) 9.5. It has been identified as a T-o-G transversion (GRCm39:chr16:62651104A>C) in the splice donor sequence of exon 2 which has been shown by RT-PCR to result in exclusion of this exon from mature transcripts and thus of most of a putative GTPase domain, including four consensus nucleotide binding sites, from the encoded protein. Immunoblot analysis reveals the absence of either normally-present protein isoform in mutant embryos. (J:120712)