Heterochromatic breaks move to the nuclear periphery to continue recombinational repair

Heterochromatin mostly comprises repeated sequences prone to harmful ectopic recombination during double-strand break (DSB) repair. In Drosophila cells, ‘safe’ homologous recombination (HR) repair of heterochromatic breaks relies on a specialized pathway that relocalizes damaged sequences away from the heterochromatin domain before strand invasion. Here we show that heterochromatic DSBs move to the nuclear periphery to continue HR repair. Relocalization depends on nuclear pore and inner nuclear membrane proteins (INMPs) that anchor repair sites to the nuclear periphery via the Smc5/6-interacting proteins STUbL/RENi. Both the initial block to HR progression inside the heterochromatin domain, and the targeting of repair sites to the nuclear periphery, rely on SUMO and SUMO E3 ligases. This study reveals a critical role for SUMOylation in the spatial and temporal regulation of HR repair in heterochromatin, and identifies the nuclear periphery as a specialized site for heterochromatin repair in a multicellular eukaryote

Glutamate Receptor Antibodies in Autoimmune Central Nervous System Disease: Basic Mechanisms, Clinical Features, and Antibody Detection.

Immune-mediated inflammation of the brain has been recognized for more than 50 years, although the initial descriptions were mainly thought to be secondary to an underlying neoplasm. Some of these paraneoplastic encephalitides express serum antibodies, but these were not thought to be pathogenic but instead have a T-cell-mediated pathophysiology. Over the last two decades, several pathogenic antibodies against neuronal surface antigens have been described in autoimmune encephalitis, which are amenable to immunotherapy. Several of these antibodies are directed against glutamate receptors (GluRs). NMDAR encephalitis (NMDARE) is the most common of these antibodies, and patients often present with psychosis, hallucinations, and reduced consciousness. Patients often progress on to develop confusion, seizures, movement disorders, autonomic instability, and respiratory depression. Although initially described as exclusively occurring secondary to ovarian teratoma (and later other tumors), non-paraneoplastic forms are increasingly common, and other triggers like viral infections are now well recognized. AMPAR encephalitis is relatively less common than NMDARE but is more likely to paraneoplastic. AMPAR antibodies typically cause limbic encephalitis, with patients presenting with confusion, disorientation, memory loss, and often seizures. The syndromes associated with the metabotropic receptor antibodies are much rarer and often can be paraneoplastic-mGluR1 (cerebellar degeneration) and mGluR5 (Ophelia syndrome) being the ones described in literature.With the advance in molecular biology techniques, it is now possible to detect these antibodies using cell-based assays with high sensitivity and specificity, especially when coupled with brain tissue immunohistochemistry and binding to live cell-based neurons. The rapid and reliable identification of these antibodies aids in the timely treatment (either in the form of identifying/removing the underlying tumor or instituting immunomodulatory therapy) and has significantly improved clinical outcome in this otherwise devastating group of conditions