This phenotypic mutant was identified in an ENU mutagenesis screen at the Baylor College of Medicine. Genomic sequencing revealed a T-to-C base-pair change in that resulted in a p.Ser192Pro amino acid substitution in the Twist box of the encoded protein. A mutant protein is expressed from this allele, but in an immunoprecipitation assay, CC mutant protein interacted poorly with Runx2 compared to the wild-type protein. (J:90056)