[Analysis of chondrocyte differentiation using chondrocyte-specific genetically modified mice].

Knockout mice are used to study physiological function of the gene, while transgenic mice expressing a high level of the transgene are used to examine pharmacological action of the gene. Genes can be deleted not only in chondrocytes, but also at various steps during the process of chondrocyte differentiation in conditional knockout mice. Conditional transgenic mouse system is available in cases in which conventional transgenic mouse lines cannot be established due to early lethality. It is possible that Cre-mediated recombination occurs at loxP sites in osteoblasts of chondrocyte-specific conditional knockout mice, suggesting that bone phenotype should be carefully analyzed and discussed.