Genetic and molecular aspects of acromelic dysplasia

The acromelic dysplasia group includes three rare disorders: Weill-Marchesani syndrome (WMS), Geleophysic dysplasia (GD) and Acromicric dysplasia (AD) all characterized by short stature, short hands and stiff joints. The clinical overlap between the three disorders is striking. Indeed, in addition to the diagnostic criteria, they all share common features including delayed bone age, cone shaped epiphyses, thick skin and heart disease. In contrast, a microspherophakic lens seems to be a characteristic feature of WMS whereas hepatomegaly and a severe outcome are encountered only in the most severe forms of GD. Finally, WMS is transmitted either by an autosomal dominant or an autosomal recessive (AR) mode of inheritance, GD by an autosomal recessive mode of inheritance and AD by an autosomal dominant mode of inheritance. Using genetic approaches, we have identified the molecular basis of WMS and GD which both involved the same superfamily of proteins, the ADAMTS [A Disintegrin-like And Metalloproteinase domain (reprolysin type) with ThromboSpondin type 1 repeats (TSR)]. We have found ADAMTS10 mutations in the recessive form of WMS and Fibrillin 1 mutations in the dominant form of WMS. More recently, we have identified ADAMTSL2 mutations in GD. The function of ADAMTS1 0 and AD AMTSL 2 are unknown. But the findings of FBN1 and ADAMTS10 mutations in WMS suggest a direct link between the two proteins. Using a yeast double hybrid screen, we have identified LTBP1 (Latent TGFbeta Binding protein 1) as a partner of ADAMTSL2. The combination of these findings suggests that ADAMTS10 and ADAMTSL2 are both involved in the microfibrillar network.