Three recessive genes for congenital osteopetrosis in Norway rat.

In the rat, the autosomal recessive toothless (t1) mutation exhibits an acute form of osteopetrosis. This gene is not an allele of either ia or op that causes respectively, a transitory and acute form of the disease. Comparative radiographic study of t1/t1 and op/op mutants reveals some differences in respect to the size and shape of long bones. In contrast to op/op mutants, homozygous t1/t1 animals failed to respond to either parabiosis or bone marrow transplants.