Characterization of ANGPT2 mutations associated with primary lymphedema

Sci Transl Med. 2020 Sep 9;12(560):eaax8013. doi: 10.1126/scitranslmed.aax8013.

Veli-Matti Leppänen ¹ ², Pascal Brouillard ³, Emilia A Korhonen ⁴, Tuomas Sipilä ⁴, Sawan Kumar Jha ², Nicole Revencu ⁵, Veerle Labarque ⁶, Elodie Fastré ⁷, Matthieu Schlögel ⁷, Marie Ravoet ⁵, Amihood Singer ⁸, Claudia Luzzatto ⁹, Donatella Angelone ¹⁰, Giovanni Crichiutti ¹¹, Angela D'Elia ¹¹, Jaakko Kuurne ⁴, Harri Elamaa ¹², Gou Young Koh ¹³ ¹⁴, Pipsa Saharinen ⁴ ², Miikka Vikkula ³ ¹⁵, Kari Alitalo ¹ ²

Affiliations

1 Wihuri Research Institute, Biomedicum Helsinki, Haartmaninkatu 8, 00290 Helsinki, Finland. miikka.vikkula@uclouvain.be kari.alitalo@helsinki.fi.
2 Translational Cancer Medicine Program, Faculty of Medicine and Helsinki Institute of Life Science, 00014 University of Helsinki, Finland.
3 Human Molecular Genetics, de Duve Institute, University of Louvain, 1200 Brussels, Belgium. miikka.vikkula@uclouvain.be kari.alitalo@helsinki.fi.
4 Wihuri Research Institute, Biomedicum Helsinki, Haartmaninkatu 8, 00290 Helsinki, Finland.
5 Center for Human Genetics, Cliniques universitaires Saint-Luc, University of Louvain, 1200 Brussels, Belgium.
6 Centre for Molecular and Vascular Biology, University of Leuven, 3000 Leuven, Belgium.
7 Human Molecular Genetics, de Duve Institute, University of Louvain, 1200 Brussels, Belgium.
8 Barzilai Medical Center, 78306 Ashekelon, Israel.
9 Padova University Hospital, 35128 Padova, Italy.
10 A. Gemelli Hospital, 00168 Roma, Italy.
11 Azienda Ospedaliero-Universitaria Santa Maria della Misericordia, 33100 Udine, Italy.
12 Oulu Centre for Cell-Matrix Research, Faculty of Biochemistry and Molecular Medicine, Biocenter Oulu, University of Oulu, 90220 Oulu, Finland.
13 Center for Vascular Research, Institute of Basic Science (IBS), 34141 Daejeon, Republic of Korea.
14 Graduate School of Medical Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), 34141 Daejeon, Republic of Korea.
15 Walloon Excellence in Lifesciences and Biotechnology (WELBIO), University of Louvain, 1200 Brussels, Belgium.

PMID: 32908006 DOI: 10.1126/scitranslmed.aax8013

Abstract

Primary lymphedema is caused by developmental and functional defects of the lymphatic vascular system that result in accumulation of protein-rich fluid in tissues, resulting in edema. The 28 currently known genes causing primary lymphedema can explain <30% of cases. Angiopoietin 1 (ANGPT1) and ANGPT2 function via the TIE1-TIE2 (tyrosine kinase with immunoglobulin-like and epidermal growth factor-like domains 1 and 2) receptor complex and α5β1 Integrin to form an endothelial cell signaling pathway that is critical for blood and lymphatic vessel formation and remodeling during embryonic development, as well as for homeostasis of the mature vasculature. By screening a cohort of 543 individuals affected by primary lymphedema, we identified one heterozygous de novo ANGPT2 whole-gene deletion and four heterozygous ANGPT2 missense mutations. Functional analyses revealed three missense mutations that resulted in decreased ANGPT2 secretion and inhibited the secretion of wild-type (WT)-ANGPT2, suggesting that they have a dominant-negative effect on ANGPT2 signaling. WT-ANGPT2 and soluble mutants T299M and N304K activated TIE1 and Tie2 in an autocrine assay in human lymphatic endothelial cells. Molecular modeling and biophysical studies showed that amino-terminally truncated ANGPT subunits formed asymmetrical homodimers that bound Tie2 in a 2:1 ratio. The T299M mutant, located in the dimerization interphase, showed reduced Integrin α5 binding, and its expression in mouse skin promoted hyperplasia and dilation of cutaneous lymphatic vessels. These results demonstrate that primary lymphedema can be associated with ANGPT2 mutations and provide insights into TIE1 and Tie2 activation mechanisms.

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