As in the case of spondyloepimetaphyseal dysplasia (SEMD) and multiple epiphyseal dysplasias (MEDs), mutations in the matrilin-3 gene cause an aberrant response towards TGF-β and the differentiation of ATDC5 chondroprogenitor cells. The gene discussed is MATN3; the disease is spondyloepimetaphyseal dysplasia.