Expression of a single ICAM-1 isoform on T cells is sufficient for development of experimental autoimmune encephalomyelitis.

Intercellular adhesion molecule-1 (ICAM-1) plays an important role in leukocyte trafficking, induction of cellular immune responses, and immunological synapse formation. As a member of the immunoglobulin superfamily of adhesion proteins, ICAM-1 is composed of repeating Ig-like domains, a transmembrane domain, and short cytoplasmic tail that participates in intracellular signaling events. At least seven ICAM-1 protein isoforms are generated by alternative splicing, however little is known regarding their immunobiology. We have previously shown using different lines of ICAM-1 mutant mice (Icam1(tm1Jcgr) and Icam1(tm1Bay) ) that expression of alternatively spliced ICAM-1 isoforms can significantly influence the disease course during the development of EAE. In this study, we show using a newly developed transgenic mouse (CD2-Icam1(D4del) /Icam1(null) ) that T-cell-specific expression of a single ICAM-1 isoform composed of Ig domains 1, 2, 3, and 5 can mediate the initiation and progression of EAE. Our results indicate that the ICAM-1 isoform lacking Ig domain 4 can drive pathogenesis in demyelinating disease and may be a novel therapeutic target for treating multiple sclerosis.

Stac3 is a component of the excitation-contraction coupling machinery and mutated in Native American myopathy.

Excitation-contraction coupling, the process that regulates contractions by skeletal muscles, transduces changes in membrane voltage by activating release of Ca(2+) from internal stores to initiate muscle contraction. Defects in excitation-contraction coupling are associated with muscle diseases. Here we identify Stac3 as a novel component of the excitation-contraction coupling machinery. Using a zebrafish genetic screen, we generate a locomotor mutation that is mapped to stac3. We provide electrophysiological, Ca(2+) imaging, immunocytochemical and biochemical evidence that Stac3 participates in excitation-contraction coupling in muscles. Furthermore, we reveal that a mutation in human STAC3 is the genetic basis of the debilitating Native American myopathy (NAM). Analysis of NAM stac3 in zebrafish shows that the NAM mutation decreases excitation-contraction coupling. These findings enhance our understanding of both excitation-contraction coupling and the pathology of myopathies.

Experimental cerebral malaria develops independently of endothelial expression of intercellular adhesion molecule-1 (icam-1).

Cerebral malaria (CM) is a severe clinical complication of Plasmodium falciparum malaria infection and is characterized by a high fatality rate and neurological damage. Sequestration of parasite-infected red blood cells in brain microvasculature utilizes host- and parasite-derived adhesion molecules and is an important factor in the development of CM. ICAM-1, an alternatively spliced adhesion molecule, is believed to be critical on endothelial cells for infected red blood cell sequestration in CM. Using ICAM-1 mutant mice, we found that the full-length ICAM-1 isoform is not required for development of murine experimental CM (ECM) and that ECM phenotype varies with the combination of ICAM-1 isoforms expressed. Furthermore, we observed development of ECM in transgenic mice expressing ICAM-1 only on leukocytes, indicating that endothelial cell expression of this adhesion molecule is not required for disease pathogenesis. We propose that ICAM-1-dependent cellular aggregation, independent of ICAM-1 expression on the cerebral microvasculature, contributes to ECM.

Exome analysis of two limb-girdle muscular dystrophy families: mutations identified and challenges encountered.

The molecular diagnosis of muscle disorders is challenging: genetic heterogeneity (>100 causal genes for skeletal and cardiac muscle disease) precludes exhaustive clinical testing, prioritizing sequencing of specific genes is difficult due to the similarity of clinical presentation, and the number of variants returned through exome sequencing can make the identification of the disease-causing variant difficult. We have filtered variants found through exome sequencing by prioritizing variants in genes known to be involved in muscle disease while examining the quality and depth of coverage of those genes. We ascertained two families with autosomal dominant limb-girdle muscular dystrophy of unknown etiology. To identify the causal mutations in these families, we performed exome sequencing on five affected individuals using the Agilent SureSelect Human All Exon 50 Mb kit and the Illumina HiSeq 2000 (2×100 bp). We identified causative mutations in desmin (IVS3+3A>G) and filamin C (p.W2710X), and augmented the phenotype data for individuals with muscular dystrophy due to these mutations. We also discuss challenges encountered due to depth of coverage variability at specific sites and the annotation of a functionally proven splice site variant as an intronic variant.

Mutations affecting the cytoplasmic functions of the co-chaperone DNAJB6 cause limb-girdle muscular dystrophy.

Limb-girdle muscular dystrophy type 1D (LGMD1D) was linked to chromosome 7q36 over a decade ago, but its genetic cause has remained elusive. Here we studied nine LGMD-affected families from Finland, the United States and Italy and identified four dominant missense mutations leading to p.Phe93Leu or p.Phe89Ile changes in the ubiquitously expressed co-chaperone DNAJB6. Functional testing in vivo showed that the mutations have a dominant toxic effect mediated specifically by the cytoplasmic isoform of DNAJB6. In vitro studies demonstrated that the mutations increase the half-life of DNAJB6, extending this effect to the wild-type protein, and reduce its protective anti-aggregation effect. Further, we show that DNAJB6 interacts with members of the CASA complex, including the myofibrillar myopathy-causing protein BAG3. Our data identify the genetic cause of LGMD1D, suggest that its pathogenesis is mediated by defective chaperone function and highlight how mutations in a ubiquitously expressed gene can exert effects in a tissue-, isoform- and cellular compartment-specific manner.

Myocilin and optineurin coding variants in Hispanics of Mexican descent with POAG.

Coding variants in both myocilin (MYOC) and optineurin (OPTN) are reported risk factors for primary open-angle glaucoma (POAG) in many populations. This study investigated the contribution of MYOC and OPTN coding variants in Hispanics of Mexican descent with and without POAG. We conducted a case-control study of unrelated POAG cases and nonglaucomatous controls in a population of Hispanics of Mexican descent. Ascertainment criteria for POAG included the presence of glaucomatous optic neuropathy with associated visual field loss and the absence of secondary causes of glaucoma. Controls had normal optic nerves, visual fields and intraocular pressure. All coding exons of MYOC and OPTN were sequenced. The data set consisted of 88 POAG cases and 93 controls. A novel nonsynonymous coding variant (R7H) in the first exon of MYOC was identified. Other identified variants in MYOC and OPTN have been previously described and do not seem to contribute to POAG risk. This is the first comprehensive study of MYOC and OPTN in Hispanics of Mexican descent with POAG. Neither MYOC nor OPTN sequence variants seem to have a major role in the etiology of POAG in this population.

Elevated serum-soluble interleukin-2 receptor levels in patients with anaplastic large cell lymphoma.

Levels of serum soluble interleukin 2 receptor (sIL-2R) provide a reliable marker of disease activity in patients with hairy cell leukemia and adult T-cell leukemia/lymphoma. The malignant cells in patients with anaplastic large cell lymphoma (ALCL) express CD30 and are usually positive for expression of CD25. We measured serum sIL-2R and soluble CD30 (sCD30) levels in patients with ALCL treated with EPOCH (etoposide, prednisone, Oncovin, Cytoxan, hydroxydaunorubicin) infusional chemotherapy. Serum sCD30 levels were elevated and decreased in response to therapy as previously reported. Serum sIL-2R levels were elevated in 7 of 9 patients with ALCL and decreased in response to treatment. Baseline serum sIL-2R levels varied but correlated well with serum sCD30 levels (r = 0.97). Patients positive for the anaplastic lymphoma kinase (ALK) gene showed elevated sIL-2R levels, whereas those negative for ALK had normal serum sIL-2R levels and their tumors lacked CD25 expression. Serum sIL-2R levels were elevated in both patients with recurrent disease.