Somatic mutations in TBX3 promote hepatic clonal expansion by accelerating VLDL secretion
Gregory Mannino, Gabriella Quinn, Min Zhu, Zixi Wang, Xun Wang, Boyuan Li, Meng-Hsiung Hsieh, Thomas Mathews, Lauren Zacharias, Wen Gu, Purva Gopal, Natalia Brzozowska, Peter Campbell, Matt Hoare, Glen Liszczak, Hao Zhu
Gregory Mannino, Gabriella Quinn, Min Zhu, Zixi Wang, Xun Wang, Boyuan Li, Meng-Hsiung Hsieh, Thomas Mathews, Lauren Zacharias, Wen Gu, Purva Gopal, Natalia Brzozowska, Peter Campbell, Matt Hoare, Glen Liszczak, Hao Zhu
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Research Article Cell biology Gastroenterology

Somatic mutations in TBX3 promote hepatic clonal expansion by accelerating VLDL secretion

Abstract

Somatic mutations that increase clone fitness or resist disease are positively selected, but the impact of these mutations on organismal health remains unclear. We previously showed that Tbx3 deletion increases hepatocyte fitness within fatty livers. Here, we detected TBX3 somatic mutations in patients with metabolic dysfunction–associated steatotic liver disease (MASLD). In mice, Tbx3 deletion protected against, whereas Tbx3 overexpression exacerbated, MASLD. Tbx3 deletion reduced lipid overload by accelerating VLDL secretion. Choline-deficient diets, which block VLDL secretion, abrogated this protective effect. TBX3 transcriptionally suppressed the conventional secretory pathway and cholesterol biosynthesis. Hdlbp is a direct target of TBX3 that is responsible for the altered VLDL secretion. In contrast to wild-type TBX3, the TBX3 I155S and A280S mutations found in patients failed to suppress VLDL secretion. In conclusion, TBX3 mutant clones expand during MASLD through increased lipid disposal, demonstrating that clonal fitness can benefit the liver at the cost of hyperlipidemia.

Authors

Gregory Mannino, Gabriella Quinn, Min Zhu, Zixi Wang, Xun Wang, Boyuan Li, Meng-Hsiung Hsieh, Thomas Mathews, Lauren Zacharias, Wen Gu, Purva Gopal, Natalia Brzozowska, Peter Campbell, Matt Hoare, Glen Liszczak, Hao Zhu

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Figure 7

Human TBX3 point mutations are loss-of-function.

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Human TBX3 point mutations are loss-of-function. (A) Western blot for V5...
(A) Western blot for V5 from WT H2.35 cells transfected with WT or mutant TBX3. (B) Immunofluorescence for V5 from WT H2.35 cells transfected with WT or mutant TBX3. (C) Relative secretion of Gaussia luciferase from WT H2.35 24 hours after cotransfection with a Gaussia luciferase expression plasmid along with WT or mutant Tbx3 expression plasmid. The significance in C was calculated using a 1-way ANOVA comparing each group to the Tbx3 WT group and corrected with Dunnett’s post hoc test. (D) Representative immunohistochemistry images of V5+ cells in livers of WT C57BL/6 mice 1 week after AAV injection expressing GFP, WT Tbx3, or Tbx3 harboring the I155S or A280S mutation. Scale bars: 500 μm. (E) Triglyceride secretion assay after 2 weeks of WD feeding from mice from D (GFP, n = 12; Tbx3 WT, n = 17; Tbx3 I155S, n = 17; Tbx3 A280S, n = 17). Two mice from the I155S group were excluded because of technical issues. The results displayed are an aggregation of 2 independent experiments. (F) Quantification of the triglyceride secretion rate of mice from D. The results displayed are an aggregation of 2 independent experiments. (G) Liver weight (left), body weight (middle), and liver/body weight ratios of WT C57BL/6 mice injected with AAV expressing GFP, WT Tbx3, or Tbx3 harboring the I155S or A280S mutations fed a WD for 12 weeks. (H) Representative H&E images of mice from G. Scale bars: 500 μm, left panels; 100 μm, right panels. Significance of the difference in plasma triglycerides among all groups at 180 minutes after P407 injection in E was calculated using a 2-way ANOVA with Tukey’s post hoc test. The statistics displayed in E represent significance of each group compared with the Tbx3-WT group. Significance of the difference in triglyceride secretion rates and the difference in liver weight, body weight, and liver/body weight ratio comparing each group to Tbx3 WT in F and G was done using a 1-way ANOVA with Tukey’s post hoc test. *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001.