Cell cycle arrest despite the increase of cyclin D1 expression have been reported in primary chondrocyte cultures from patients with thanatophoric dysplasia type I, a lethal chondrodysplasia caused by activating mutations of the FGFR3 [Laplantine et al., 2002; Dailey et al., 2003; Schibler et al., 2009]. This evidence concerns the gene CCND1 and thanatophoric dysplasia type 1.