Stop codons were introduced into all three reading frames of the intronless gene by the insertion a translation frameshift linker into the amino-terminal centromere DNA-binding domain. An IRES-neomycin selection marker was inserted in the 3' untranslated region upstream of the poly adenylation signal. RT-PCR analysis of heterozygous mutant mice showed the expression of a truncated transcript. Mice possessing both this allele and Cenpbtm2Khac were shown to lack transcript and protein was not detected by immunofluorescence staining of metaphase chromosomes. (J:47171)