Dynamin 2 (DNM2) is a large GTPase involved in the release of nascent vesicles during endocytosis and intracellular membrane trafficking. Distinct DNM2 mutations, affecting the middle domain (MD) and the Pleckstrin homology domain (PH), have been identified in autosomal dominant centronuclear myopathy (CNM) and in the intermediate and axonal forms of the Charcot-Marie-Tooth peripheral neuropathy (CMT). We report here the first CNM mutation (c.1948G>A, p.E650 K) in the DNM2 GTPase effector domain (GED), leading to a slowly progressive moderate myopathy. COS7 cells transfected with DNM2 constructs harboring a disease-associated mutation in MD, PH, or GED show a reduced uptake of transferrin and low-density lipoprotein (LDL) complex, two markers of clathrin-mediated receptor endocytosis. A decrease in clathrin-mediated endocytosis was also identified in skin fibroblasts from one CNM patient. We studied the impact of DNM2 mutant overexpression on epidermal growth factor (EGF)-induced extracellular signal-regulated kinase 1 (ERK1) and ERK2 activation, known to be an endocytosis- and DNM2-dependent process. Activation of ERK1/2 was impaired for all the transfected mutants in COS7 cells, but not in CNM fibroblasts. Our results indicate that impairment of clathrin-mediated endocytosis may play a role in the pathophysiological mechanisms leading to DNM2-related diseases, but the tissue-specific impact of DNM2 mutations in both diseases remains unclear.

The blood–brain barrier (BBB), which forms the interface between the blood and the cerebral parenchyma, has been shown to be disrupted during retroviral-associated neuromyelopathies. Human T Lymphotropic Virus (HTLV-1) Associated Myelopathy/Tropical Spastic Paraparesis (HAM/TSP) is a slowly progressive neurodegenerative disease associated with BBB breakdown. The BBB is composed of three cell types: endothelial cells, pericytes and astrocytes. Although astrocytes have been shown to be infected by HTLV-1, until now, little was known about the susceptibility of BBB endothelial cells to HTLV-1 infection and the impact of such an infection on BBB function. We first demonstrated that human cerebral endothelial cells express the receptors for HTLV-1 (GLUT-1, Neuropilin-1 and heparan sulfate proteoglycans), both in vitro, in a human cerebral endothelial cell line, and ex vivo, on spinal cord autopsy sections from HAM/TSP and non-infected control cases. In situ hybridization revealed HTLV-1 transcripts associated with the vasculature in HAM/TSP. We were able to confirm that the endothelial cells could be productively infected in vitro by HTLV-1 and that blocking of either HSPGs, Neuropilin 1 or Glut1 inhibits this process. The expression of the tight-junction proteins within the HTLV-1 infected endothelial cells was altered. These cells were no longer able to form a functional barrier, since BBB permeability and lymphocyte passage through the monolayer of endothelial cells were increased. This work constitutes the first report of susceptibility of human cerebral endothelial cells to HTLV-1 infection, with implications for HTLV-1 passage through the BBB and subsequent deregulation of the central nervous system homeostasis. We propose that the susceptibility of cerebral endothelial cells to retroviral infection and subsequent BBB dysfunction is an important aspect of HAM/TSP pathogenesis and should be considered in the design of future therapeutics strategies.

An inappropriate cross talk between activated T lymphocytes infiltrating the CNS and neural cells can sustain the onset and progression of demyelination and axonal degeneration in neuroinflammatory diseases. To mimic this deleterious cross talk, we designed an experimental paradigm consisting of transient cocultures of T lymphocytes chronically activated by retrovirus infection (not virus productive) with human multipotent neural precursors or primary oligodendrocytes from rat brain. We showed that activated T lymphocytes induced apoptotic death of multipotent neural progenitors and immature oligodendrocytes after a progressive collapse of their process extensions. These effects were reminiscent of those induced by brain semaphorin on neural cells. Blockade by specific Abs of soluble CD100 (sCD100)/semaphorin 4D released by activated T cells, or treatment with rsCD100, demonstrated that this immune semaphorin has the ability to collapse oligodendrocyte process extensions and to trigger neural cell apoptosis, most likely through receptors of the plexin family. The specific presence of sCD100 in the cerebrospinal fluid and of CD100-expressing T lymphocytes in the spinal cord of patients suffering with neuroinflammatory demyelination pointed to the potential pathological effect of sCD100 in the CNS. Thus, our results show that CD100 is a new important element in the deleterious T cell-neural cell cross talk during neuroinflammation and suggest its role in demyelination or absence of remyelination in neuroinflammatory diseases including multiple sclerosis and human T lymphotropic virus type 1-associated myelopathy.

The worldwide geographic and ethnic clustering of patients with diseases related to human T-cell lymphotropic virus type I (HTLV-I) may be explained by the natural history of HTLV-I infection. The genetic characteristics of indigenous people in the Andes are similar to those of the Japanese, and HTLV-I is generally detected in both groups. To clarify the common origin of HTLV-I in Asia and the Andes, we analyzed HTLV-I provirus DNA from Andean mummies about 1,500 years old. Two of 104 mummy bone marrow specimens yielded a band of human beta-globin gene DNA 110 base pairs in length, and one of these two produced bands of HTLV-I-pX (open reading frame encoding p40x, p27x) and HTLV-I-LTR (long terminal repeat) gene DNA 159 base pairs and 157 base pairs in length, respectively. The nucleotide sequences of ancient HTLV-I-pX and HTLV-I-LTR clones isolated from mummy bone marrow were similar to those in contemporary Andeans and Japanese, although there was microheterogeneity in the sequences of some mummy DNA clones. This result provides evidence that HTLV-I was carried with ancient Mongoloids to the Andes before the Colonial era. Analysis of ancient HTLV-I sequences could be a useful tool for studying the history of human retroviral infection as well as human prehistoric migration.