The physiological and pathological functions of VEGFR3 in cardiac and lymphatic development and related diseases

Abstract

Vascular endothelial growth factor receptors (VEGFRs) are part of the evolutionarily conserved VEGF signalling pathways that regulate the development and maintenance of the body's cardiovascular and lymphovascular systems. VEGFR3, encoded by the FLT4 gene, has an indispensable and well-characterized function in development and establishment of the lymphatic system. Autosomal dominant VEGFR3 mutations, that prevent the receptor functioning as a homodimer, cause one of the major forms of hereditary primary lymphoedema; Milroy disease. Recently, we and others have shown that FLT4 variants, distinct to those observed in Milroy disease cases, predispose individuals to Tetralogy of Fallot, the most common cyanotic congenital heart disease, demonstrating a novel function for VEGFR3 in early cardiac development. Here, we examine the familiar and emerging roles of VEGFR3 in the development of both lymphovascular and cardiovascular systems, respectively, compare how distinct genetic variants in FLT4 lead to two disparate human conditions, and highlight the research still required to fully understand this multifaceted receptor.

Keywords: Angiogenesis and lymphangiogenesis; Congenital heart disease; Heart development; Primary lymphoedema; Vascular endothelial growth factor receptors.

Figure 1

Structures, interactions, physiological roles, and associated diseases of VEGFR family members. Schematic showing the interactions of the three VEGFRs with each other and their ligands at the plasma membrane. Their expression pattern, physiological roles and pathologies associated with their levels or dysfunction are also shown. Ig, immunoglobulin-like domain; SS, disulphide bond.

Figure 2

VEGFR3 signalling during lymphangiogenesis and Milroy disease. Ligand binding and VEGFR3 homodimerization during lymphangiogenesis results in activation of downstream signalling pathways in LECs or precursor endothelial cells (A). The dominant negative mutations of the kinase domain of VEGFR3 in Milroy disease result in reduction of downstream signalling following ligand binding due to loss of autophosphorylation and thus consequent disruption of lymphangiogenesis (B). *Mutations in the kinase domain of VEGFR3 that inactivate the receptor’s catalytic activity; pY, phosphotyrosine; SS, disulphide bond; description of protein abbreviations in main text.

Figure 3

VEGFR3 functions with VEGFR2 and NRP2. Heterodimerization of VEGFR3 and VEGFR2 and activation by VEGFA or VEGFC regulates multiple biological processes in endothelial and endothelial-derived cell lines (A). Association of VEGFR3 homodimers with NRP2 and activation of VEGFR3 by its cognate ligands and NRP2 by VEGFA modulates VEGFR3 function (B). SS, disulphide bond.

Figure 4

Developmental timing of cardiovascular and lymphovascular system development. Developmental timings in both human and mouse of cardiovascular and lymphovascular development, aligned with the Carnegie stages of embryonic development. For references, see main text.

Figure 5

Comparison of VEGFR3 mutations between Milroy disease and TOF. The characterized VEGFR3 mutations known to cause Milroy disease (missense or small in frame deletions, blue dots) are compared to those that predispose to TOF (missense, predicted highly damaging to protein function, scaled combined annotation-dependent depletion score ≥20; previously unobserved in the general population, absent from the gnomAD database, green dots; or truncating, i.e. nonsense, frameshifts and splice donor or acceptor site nucleotide changes, red dots). The location of the de novo point mutant C51W is indicated beneath. References in the main text. Ig, immunoglobulin-like domain; SP, signal peptide; TMD, transmembrane domain.