Deciphering the mechanism involved in brain hemorrhages induced by ALK1-NRP1 deletion

Objectifs

The aim of this internship is to understand how defects in the axon guidance signaling pathway can lead to brain microhemorrhages in a mouse model of a rare vascular disease (Rendu-Osler) in order to propose new therapeutic approaches.

Résumé

ALK1 is a receptor mainly expressed on endothelial cells, which is necessary for proper vascular quiescence. Indeed, mutations of ALK1 are involved in a rare autosomal dominant vascular disease named Rendu-Osler or HHT (hereditary hemorrhagic telangiectasia) characterized by brain vascular malformations. In a mouse model where Alk1 is deleted in endothelial cell (Alk1iECKO), RNAseq analysis revealed crosstalk with the axon guidance semaphorin/neuropilin (NRP1)/plexin signaling pathway. Interestingly, we observed that invalidating NRP1 with anti-NRP1 antibody in our Alk1iECKO mouse model induces brain hemorrhages within a week. The objectives of this internship are to:
1) Characterize by electron microscopy and immunofluorescence the brain vascular defects induced by this treatment.
2) Decipher the molecular signaling leading to brain hemorrhages using brain primary endothelial cells.

Méthodes

Microscopy techniques including Transmission electron microscopy, immunofluorescence.
Cell culture, molecular biology (RNA extraction and qPCR), and biochemistry (Western blot, proteomic) Mouse model.

Référence

Desroches-Castan A, Koca D, Liu H, Roelants C, Resmini L, Ricard N, Bouvard C, Chaumontel N, Tharaux PL, Tillet E, Battail C, Lenoir O, Bailly S. BMP9 is a key player in endothelial identity and its loss is sufficient to induce arteriovenous malformations. Cardiovasc Res. 2024. doi: 10.1093/cvr/cvae052. PMID: 38502919. 

Al Tabosh T, Liu H, Koça D, Al Tarrass M, Tu L, Giraud S, Delagrange L, Beaudoin M, Rivière S, Grobost V, Rondeau-Lutz M, Dupuis O, Ricard N, Tillet E, Machillot P, Salomon A, Picart C, Battail C, Dupuis-Girod S, Guignabert C, Desroches-Castan A, Bailly S. Impact of heterozygous ALK1 mutations on the transcriptomic response to BMP9 and BMP10 in endothelial cells from hereditary hemorrhagic telangiectasia and pulmonary arterial hypertension donors. Angiogenesis. 2024. doi: 10.1007/s10456-023-09902-8.

Hermann R, Shovlin CL, Kasthuri RS, Serra M, Eker OF, Bailly S, Buscarini E, Dupuis-Girod S. Hereditary haemorrhagic telangiectasia. Nat Rev Dis Primers. 2025. doi: 10.1038/s41572-024-00585-z.

Domaines d'expertise requis

Cellular biology, physiology, signaling

Contact

Agnès Desroches-Castan (Research Engineer,Inserm, HDR) and Louane Despas (PhD student)
Email : agnes.castaninserm.fr
Téléphone : 04 38 78 64 44