TGF-b1, 2 AND 3 ACTIVATING MUTATIONS DO NOT INCREASE SUSCEPTIBILITY TO EXPERIMENTALLY INDUCED LIVER FIBROSIS IN MICE

Details

Supervisors

Lucas, Sophie ; Michiels, Camille

Faculty

Faculté de pharmacie et des sciences biomédicales

Degree label

Master [120] en sciences biomédicales, à finalité approfondie

Abstract

enTGF-β1, β2, and β3 are pleiotropic cytokines belonging to the TGF-β superfamily. They are involved in various cellular processes such as differentiation, proliferation, and migration, and are well known for their immunosuppressive and pro-fibrotic effects. These cytokines are produced in a latent form and must be activated to perform their biological functions. Genetic analysis carried out by Professor Nisha Limaye's laboratory (de Duve Institute) on patients with familial systemic scleroderma (SSc) identified a rare variant of the gene encoding TGF-β2 (p.Val67Met) in two of these patients. My host laboratory was able to demonstrate that this variant, as well as the corresponding mutations in TGF-β1V77M and TGF-β3V69M, spontaneously increased TGF-β activation in vitro and in vivo, highlighting the activating nature of these mutations. However, no obvious spontaneous fibrotic or autoimmune disease was observed in mice in whose genomes these mutations were introduced using CRISPR-Cas9 technology. As part of this project, we sought to determine whether the activating mutations Tgf-β1V77M, Tgf-β2V67M, and Tgf-β3V69M could increase the susceptibility of mice to developing experimental liver fibrosis using a well-established model of injections of a hepatotoxic agent, carbon tetrachloride (CCl4). Specifically, we used a chronic model (6 weeks of CCl4 exposure) and an acute model (single injection of CCl4) in Tgfb1V77M/V77M, Tgfb2V67M/V67M, or Tgfb3V69M/V69M mice and their littermate controls. These models induced detectable TGF-β activity in vivo as well as hepatic fibrosis, as shown by histology and increased expression of pro-fibrotic genes (e.g., Col1a1, Col1a2) in the liver. However, no differences were observed between mutant and control mice in terms of TGF-β activity, except at 7 days in Tgfb3V69M/V69M mice, and although this did not translate into more severe fibrosis. Based on these observations, we can conclude that the activating mutations Tgf-β1V77M, Tgf-β2V67M, and Tgf-β3V69M do not increase the susceptibility of mice to develop liver fibrosis. We conclude that the effect of the mutations on TGF-β activity is too weak to influence the phenotype of the mice on its own.