This transgene expresses Cre recombinase under the control of the collagen II (Col2a1) promoter, which directs expression in all cartilagenous structures at E12.5, as well as the facial mesenchyme and the CNS. At E13.5, Cre-recombinase activity is detected in the skeletal structures of the developing appendicular, axial and cranial skeleton, such as long bones of limbs, ribs, vertebrae and skull base, as well as in the epithelial cells of kidney, pancreas, lungs, intestine and ovary.