Deciphering mechanobiology in human diseases by developing a TMEM63B channelopathy mouse model

SUMMARY Cells rely on precise sensing and prompt responses to mechanical and osmotic changes to maintain functionality and survival. Recent breakthroughs, including the identification of mechanosensitive and osmo-sensitive ion channels, have revolutionized our understanding of cellular responses to these

stimuli. Despite this, the pathophysiological mechanisms of these processes in disease remain elusive. In this application, we aim to address this knowledge gap by creating a mouse model with a human gain-of-function V44M mutation of TMEM63B, a newly discovered mechano- and osmo-sensing ion channel. The V44M TMEM63B channelopathy is associated with a diverse range of human

symptoms, including epilepsy, intellectual disabilities, and distinctive blood cell disorders. Our preliminary studies revealed an unexpected trait of the V44M mutation. This channelopathy mutation not only alter the ion channel activity of TMEM63B but also bestows a novel function that has been lost in

TMEM63 proteins during evolution. Specifically, the V44M mutation enables lipid scrambling - the bidirectional translocation of lipids across cell membranes. This function is reminiscent of the capabilities seen in TMEM63B's evolutionary cousins, the TMEM16 lipid scramblases. To explore the in vivo implications of this mutation in human diseases, we propose creating a TMEM63B-V44M knockin

mouse with controlled cell-type specific expression. This model will allow specifically dissect the mutated ion channel's role and its newfound lipid transport property across various cell types and disease contexts. Post-validation with our robust functional assays in this application, this mouse line

will be made available to researchers across diverse disciplines including hematology, neurobiology, and more. This pioneering TMEM63B channelopathy mouse model will be invaluable to uncover the unknown pathophysiology of this mysterious mechano- and osmo-sensing ion channels in health and disease and shine light on therapeutics to treat TMEM63B related diseases.