G-to-A spontaneous mutation in exon 2 of the gene locus resulted in a non-conservative glutamic acid-to-lysine substitution at residue 26 in the beta-propeller domain of the protein. This residue was in a surface-exposed loop12 adjacent to a region that in the related protein Coro1B has been indicated to be an actin-binding site. The mutant protein was found to not localize to the leading edge of migrating T cells in the manner that the endogenous protein does. Immunoblot analysis showed that the abundance of the mutant protein in homozygote thymocytes was similar to the endogenous protein in wild-type controls.