GIMAP5 maintains liver sinusoidal endothelial cell identity and prevents portal hypertension

Chronic liver disease is a major leading cause of portal hypertension that affects approximately 1.5 billion people globally. We show that GIMAP5, a small organellar GTPase, is selectively expressed in liver endothelial cells and human GIMAP5 deficiency causes portal hypertension with capillarization of liver sinusoidal endothelial cells (LSECs). LSEC capillarization is recapitulated in GIMAP5 loss-of-function (LOF) mice, and upon conditional Gimap5 deletion in endothelial cells. Single cell RNA-sequencing analyses reveals replacement of LSECs with capillarized endothelial cells and expansion of liver lymphatic endothelial cells in GIMAP5 LOF mice, and places GIMAP5 upstream of GATA4, a transcription factor required for LSEC-specification. Our studies reveal that GIMAP5 prevents portal hypertension by maintaining LSEC identity and suggest that LSEC is an induced endothelial cell state. single cell RNA-sequencing of sorted (CD45-CD31+) liver endothelial cells isolated from Gimap5sph/+ and Gimap5sph/sph mice