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]. Here, FGFR3 is linked to thanatophoric dysplasia type 1.