Mice lacking desmin produce muscle fibers with Z disks and normal sarcomeric organization. However, the muscles are mechanically fragile and degenerate upon repeated contractions. We report here a human patient with severe generalized myopathy and aberrant intrasarcoplasmic accumulation of desmin intermediate filaments. Muscle tissue from this patient lacks the wild-type desmin allele and has a desmin gene mutation encoding a 7-aa deletion within the coiled-coil segment of the protein. We show that recombinant desmin harboring this deletion cannot form proper desmin intermediate filament networks in cultured cells, nor is it able to assemble into 10-nm filaments in vitro. These findings provide direct evidence that a mutation in desmin can cause human myopathies.

HLA-A and -B transplantation antigens can be expressed differentiafly at the basal level and in response to interferons (IFNs). To determine which DNA control elements and nuclear factors are responsible for these differences,HLA-A and -B upstream regulatory regions were used in expression and mobility-shift analyses. The HLA-A enhancer was found to contain two Rel (KBF/NF-#cB) binding motifs, while the HLA-B enhancer has only one and is transactivated less well by overexpression of the NF-#cB p65 subunit. transcription (13, 14). Overexpression of IRF-1 has been shown to increase the basal and IFN-induced levels of class I expression (15, 16).HLA-A and -B genes are highly homologous but exhibit locus-specific differences in both their transcribed (17) andThe publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.upstream regions (18,19) and are not tightly coordinated in their regulation. They can differ in basal and induced levels of expression, with cortical thymocytes and related thymomas such as MOLT-4, for example, expressing low levels of HLA-A but undetectable , while HLA-B loci respond more strongly to IFNs (21,22) and are subject to stronger suppression by c-myc expression (23). We report here that some of the locus-specific differences between the ENH and IRE of HLA-A and -B have significant effects on the binding of the Rel and IRF families of transcription factors and consequently on the regulation of the two loci. MATERIALS AND METHODSCell Culture, Transfection, and Chloramphenicol Acetyltransferase (CAT) Assays. MOLT4 and YHHH (24) cell lines were maintained in Dulbecco's modified Eagle's medium, and JM and Daudi in RPMI 1640 medium, all with 5% fetal bovine serum. Induction of NF-KB in JM cells was achieved by a 2-hr treatment with phytohemagglutinin (PHA, 5 ,ug/ml; Sigma) and phorbol 12,13-dibutyrate (PBt2, 50 nM; Sigma). Transfections and CAT assays were performed as described (25). Cells were harvested 20 hr after transfection. IFN-aA (kindly provided by M. Brunda, Hoffmann-La Roche) was added after transfection at 2000 units/ml where indicated.Plasmids. CAT reporters were produced by cloning synthetic oligonucleotides into an Sph I site introduced into the Bgl II site at the 5' end of the metallothionein promoter of pMCAT3 (26) and verified by double-stranded sequencing. The Rel p50 and p65 expression plasmids (27) were kindly provided by A. Baldwin (University of North Carolina, Chapel Hill) and the CMV-GalVP16 vector (28) by P. O'Hare (Marie Curie Research Institute, Oxted, Surrey, U.K.).Electrophoretic Mobility-Shift Assays. Nuclear extracts from cell lines were prepared (29) and mobility-shift assays were performed (25) as described. Baculovirus Expression of IRF-1 and IRF-2. Human IRF-1 and IRF-2 clones were obtained from the lymphoid lines HUT78 and MOLT-4, respectively, by two rounds of amplification by polymerase chain reaction...