scRNA-seq reveals the diversity of the developing cardiac cell lineage and molecular players in heart rhythm regulation

Llgl1 mediates timely epicardial emergence and establishment of an apical laminin sheath around the trabeculating cardiac ventricle

“…We confirmed expression of laminin subunits in the epicardium along with an epicardial requirement for apical laminin deposition. In line with this, scRNA-seq analysis at 72 hpf has identified lamc1 as a marker of epicardial identity ( Abu Nahia et al, 2024 ), and transcriptomic analysis of wt1a mutants identified a downregulation of ECM components including lama5 ( Boezio et al, 2023 ). We speculate that epicardially-deposited apical laminin could promote ventricular morphogenesis and help to maintain wall integrity and directionality of CM delamination during early trabeculation.…”

“…5P,R ), confirming the epicardium as the source of laminin deposited on the ventricular surface. Conversely, wt1a morphants retained deposition of laminin at the basal CM surface, likely from earlier expression and deposition of laminin by either myocardial or endocardial cells ( Derrick et al, 2021a ; Abu Nahia et al, 2024 ), which was unaffected by later epicardial development.…”

“…This raises further questions about whether the CM extrusion defects in llgl1 mutants are secondary to epicardial defects or represent a direct role for llgl1 in CMs regulating wall integrity. llgl1 is expressed relatively broadly throughout the embryo ( Clark et al, 2012 ), and single cell RNA-sequencing (scRNA-seq) analysis of the developing heart at 48 hpf and 72 hpf reveal it is expressed at low levels in both myocardial and epicardial cells ( Abu Nahia et al, 2024 ), suggesting it could play a role in both cell types.…”