Cytoglobin regulates ventricular morphogenesis and diastolic function through NO-sGC-cGMP signaling during development.

AimsHypoplastic left heart syndrome (HLHS) is a severe congenital heart disease characterized by ventricular hypoplasia and impaired cardiac function. Clinically, inhaled nitric oxide (NO) therapy is used to reduce pulmonary vascular resistance and improve cardiopulmonary stability in HLHS patients. However, whether NO signaling contributes to HLHS pathogenesis remains unknown. Cytoglobin (CYGB) is a heme protein traditionally thought to limit NO bioavailability. Unexpectedly, our recent work shows that CYGB/Cygb enhances NO signaling through activation of the nitric oxide synthase-soluble guanylate cyclase (sGC)-cyclic guanosine monophosphate (cGMP) signaling pathway. In zebrafish embryos, Cygb-dependent NO signaling is required for normal cilia motility and for the establishment of correct cardiac laterality. Here, our aim was to determine whether Cygb-dependent NO-sGC signaling linked to cilia function regulates cardiac morphogenesis and contributes to ventricular hypoplasia in HLHS. Methods and ResultsWe found that loss of Cygb (cygb2) in zebrafish disrupts NO-sGC signaling during cardiogenesis, altering cardiac progenitor organization and migration within the anterior lateral plate mesoderm (ALPM). Disruption of these processes impairs heart tube morphogenesis, thereby producing a compact ventricle with increased wall thickness despite preserved cardiomyocyte number, reduced ventricle size and decreased stroke volume, recapitulating key features of HLHS. Genetic disruption of the sGC -subunit (gucy1a1) and pharmacological NO scavenging phenocopy the cygb2 mutant phenotype, resulting in reduced cGMP levels, compact ventricular architecture and decreased stroke volume (SV). Consistently, restoration of NO-sGC signaling in cygb2 mutants rescues early cardiac progenitor patterning, ventricular morphology and SV. ConclusionsThese findings identify Cygb-dependent NO-sGC signaling as a critical developmental pathway for ventricular development and performance, temporally linking cardiac progenitor dynamics to cilia-dependent signaling associated with left-right patterning. This study further suggests that pharmacological activation of sGC may provide a therapeutic strategy for hypoplastic ventricular disease. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=187 HEIGHT=200 SRC="FIGDIR/small/711730v1_ufig1.gif" ALT="Figure 1"> View larger version (58K): org.highwire.dtl.DTLVardef@e266corg.highwire.dtl.DTLVardef@fca897org.highwire.dtl.DTLVardef@1a06fc2org.highwire.dtl.DTLVardef@93acd_HPS_FORMAT_FIGEXP M_FIG C_FIG