Missense mutations in MORC2 cause neuropathies including spinal muscular atrophy and Charcot–Marie–Tooth disease. We recently identified MORC2 as an effector of epigenetic silencing by the human silencing hub (HUSH). Here we report the biochemical and cellular activities of MORC2 variants, alongside crystal structures of wild-type and neuropathic forms of a human MORC2 fragment comprising the GHKL-type ATPase module and CW-type zinc finger. This fragment dimerizes upon binding ATP and contains a hinged, functionally critical coiled-coil insertion absent in other GHKL ATPases. We find that dimerization and DNA binding of the MORC2 ATPase module transduce HUSH-dependent silencing. Disease mutations change the dynamics of dimerization by distinct structural mechanisms: destabilizing the ATPase-CW module, trapping the ATP lid, or perturbing the dimer interface. These defects lead to the modulation of HUSH function, thus providing a molecular basis for understanding MORC2-associated neuropathies.

Missense mutations in MORC2 cause neuropathies including spinal muscular atrophy and Charcot-Marie-Tooth disease. We recently identified MORC2 as an effector of epigenetic silencing by the HUSH complex. Here we report the biochemical and cellular activities of MORC2 variants, alongside crystal structures of wild-type and neuropathic forms of a human MORC2 fragment comprising the GHKL-type ATPase module and CW-type zinc finger. This fragment dimerizes upon binding ATP and contains a hinged, functionally critical coiled coil insertion absent in other GHKL ATPases. We find that dimerization and DNA binding of the MORC2 ATPase module transduce HUSH-dependent silencing. Disease mutations change the dynamics of dimerization by distinct structural mechanisms: destabilizing the ATPase-CW module, trapping the ATP lid or perturbing the dimer interface. These defects lead to modulation of HUSH function, thus providing a molecular basis for understanding MORC2-associated neuropathies.All rights reserved. No reuse allowed without permission.(which was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.

This study aimed to evaluate the performance of the Unyvero P50 pneumonia assay, the first 'sample-in, answer-out' system for rapid identification of pathogens and antibiotic resistance markers directly from clinical specimens. Overall, Unyvero P50 displayed very good sensitivity (>95%); however, specificity was low (33%) mainly because 40% of the specimens were reported as normal flora. Specifically, one or more pathogens were identified in 28 of them. From a detailed analysis of 42 specimens selected at random, 76% of the additionally reported pathogens were confirmed present in primary specimens. Detection of selected resistance markers was compared to routine phenotypic susceptibility testing, supplemented with Checkpoints microarray system, PCR and sequencing. Concordance was mixed, primarily due to issues with panel's choice of markers and detection of some intrinsic beta-lactamases. Finally, we offer a critical analysis of the assay's microbial panel and resistance markers and provide suggestions for improvement.