Exclusion of stromelysin-1, stromelysin-2, interstitial collagenase and fibronectin genes as the mutant loci in a family with recessive epidermolysis bullosa dystrophica and a form of cerebellar ataxia

The interstitial collagenase gene (CLG), one of the main candidates in severe generalized recessive epidermolysis bullosa dystrophica (SGREBD), is closely linked to the stromelysin-1 (STMY1) and stromelysin-2 (STMY2) genes. These three loci map on chromosome 11 (q21-q22.3), where they constitute a cluster of genes coding for metalloproteinases involved in the degradation of the extracellular matrix (ECM). A recessive form of cerebellar ataxia of post-puberal onset (CLA1) has also been assigned to chromosome 11 (q14-q21). Since useful restriction fragment length polymorphisms (RFLPs) for the CLG gene are not available, we have studied the inheritance of the marker TaqI RFLP of the STMY1 gene in a North Italian family with a child affected by SGREBD, and his two sisters showing cerebellar ataxia (CA) of post-puberal onset. We have also studied the MspI RFLP of the fibronectin gene (FN1), which is located on chromosome 2q34-q36, and which codes for non-collagenous matrix proteins. Since we did not observe the segregation of the pathological phenotypes with STMY1 and FN1 RFLPs, we excluded the involvement of these genes in both the SGREBD and CA present in this family. The exclusion of the STMY1 gene indicates that the mutation causing SGREBD cannot be located in the CLG and/or STMY2 genes because of their proximity to the STMY1 locus. These data also indicate that the CA form here reported is not attributable to alterations in regions close to the collagenase cluster on chromosome 11.