A gene trap containing a beta-geo reporter inserted into the sequences after exon 9, resulting in a truncated protein in which 10 of the 11 zinc fingers are lost. Real time PCR analysis revealed no detectable mRNA in the heart of E12.5 homozygous mutant embryos. Western blot analysis confirmed the absence of protein expression of both the full-length (Casz1a) and shorter (Casz1b) isoform in E14.5 whole heart lysates. (J:242127)