This allele is a derivative of Col1a1tm1Jcm in which the loxP-flanked stop-neomycin selection cassette was removed by mating mice carrying Col1a1tm1Jcm to mice expressing Cre recombinase under the control of an EIIa promoter. F2 mice of this cross were screened for deletion of the cassette sequences. RT-PCR analysis and northern blots confirmed the expression of the mutant allele. Western blot analysis confirmed that the mutant protein was expressed in skin of homozygous mice.