Emery-Dreifuss muscular dystrophy (EDMD) is an X-linked recessive disorder characterized by slowly progressing contractures, wasting of skeletal muscle and cardiomyopathy. Heart block is a frequent cause of death. The disease gene has been mapped to distal Xq28. Among many genes in this region, we selected eight transcripts expressed at high levels in skeletal muscle, heart and/or brain as the best candidates for the disease. We now report, in all five patients studied, unique mutations in one of the genes, STA: these mutations result in the loss of all or part of the protein. The EDMD gene encodes a novel serine-rich protein termed emerin, which contains a 20 amino acid hydrophobic domain at the C terminus, similar to that described for many membrane proteins of the secretory pathway involved in vesicular transport.