Small-molecule functional rescue of PIEZO1 channel variants associated with generalised lymphatic dysplasia

Generalised Lymphatic Dysplasia (GLD) is characterised by widespread lymphoedema, with at least one of the following: fetal hydrops, intestinal or pulmonary lymphangiectasia, pleural effusions, pericardial effusions and ascites. Satisfactory medical therapies are lacking. A genetic association has been identified that prevents expression or surface trafficking of PIEZO1, a subunit of mechanically activated calcium-permeable channels. However, PIEZO1 is a large and highly polymorphic gene and interpretation of variants identified in this gene can be challenging. PIEZO1-related GLD with non-immune fetal hydrops is autosomal recessive, however, heterozygous variants in PIEZO1 (often gain-of-function) causing Dehydrated Hereditary Stomatocytosis (DHS) (a relative mild anaemia), may also present with perinatal non-immune hydrops (not caused by anaemia). Here we sought to develop methods to confirm pathogenicity of missense variants of uncertain significance in PIEZO1, to gain deeper understanding and pharmacological solutions. Four novel GLD-associated missense variants in PIEZO1 are identified that express and surface localise as full-length protein but with reduced or abolished mechanically activated channel function. Yoda1, a small-molecule agonist, functionally rescues the channels and their physiological regulation by mechanical force and hypo-osmolality. The GLD-associated variants mediate intracellular calcium release as well as calcium entry, suggesting two pools of channels and opportunity for increased rescue through access to the intracellular pool. New Yoda1 analogues are also identified that improve rescue. The functional assays have assisted the interpretation of the variants of uncertain significance as the data suggest loss of PIEZO1 force sensing as a cause of the GLD observed in the patients. The potential to pharmacologically overcome the loss of force sensing was demonstrated and supports the concept of stimulation of PIEZO1 with an agonist to address wide-ranging problems of lymphatic insufficiency. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=93 SRC="FIGDIR/small/23292554v1_ufig1.gif" ALT="Figure 1"> View larger version (30K): org.highwire.dtl.DTLVardef@2f514eorg.highwire.dtl.DTLVardef@831480org.highwire.dtl.DTLVardef@1b6ee1forg.highwire.dtl.DTLVardef@cb6757_HPS_FORMAT_FIGEXP M_FIG C_FIG HIGHLIGHTSO_LIPreviously unrecognised variants in PIEZO1 that associate with GLD are identified and characterised and pathogenicity confirmed C_LIO_LIThe variants encode single amino acid changes that inhibit PIEZO1 channel activation by physiological mechanical forces C_LIO_LIA small-molecule agonist rescues the channels and their physiological regulation C_LIO_LIVariants are partly intracellular, suggesting an opportunity for improved rescue through the use of intracellular-acting agonists C_LIO_LINew agonists are identified that improve rescue, suggesting routes to medical therapies for GLD and potentially other disorders of lymphatic insufficiency C_LI