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 6

TBX3 regulates VLDL secretion through regulating cholesterol homeostasis.

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TBX3 regulates VLDL secretion through regulating cholesterol homeostasis...
(A) Western blots showing Tbx3 KO and overexpression in H2.35 cells. (B) Heatmaps from in vitro CUT&RUN (left) and in vivo ChIP-Seq for TBX3 binding loci. (C) Genomic tracks of VLDL secretion and cholesterol biosynthesis genes showing TBX3 binding in vitro and in vivo. (D) Gene Ontology pathway enrichment analysis from overlapping in vitro and in vivo TBX3 binding sites. (E) Relative secretion of Gaussia luciferase from Tbx3-KO and overexpression H2.35 cell lines. (F) Venn diagram showing the overlap of genes that are transcriptionally upregulated during MASLD in Tbx3-KO livers and have a TBX3 binding site in vitro and in vivo. (G) Hdlbp genomic tracks showing TBX3 binding in vitro and in vivo. (H) Western blot showing HDLBP expression in Tbx3-overexpressing H2.35 cells. (I) qPCR of Hdlbp mRNA levels in livers from Tbx3-KO mice fed a WD for 4 weeks. (J) Western blot showing HDLBP protein levels in livers from Tbx3-KO mice (top) or Tbx3-overexpressing mice (bottom) fed a WD for 4 weeks. (K) Western blot showing Tbx3 and Hdlbp double knockout (DKO) in vivo and triglyceride secretion assay from Tbx3/Hdlbp DKO mice fed a WD for 2 weeks (sgLacZ/sgNT, n = 7; sgLacZ/sgHdlbp, n = 7; sgTbx3/sgNT, n = 7; sgTbx3/sgHdlbp, n = 8). (L) qPCR of cholesterol biosynthesis genes from Tbx3-KO or -WT mice fed a WD for 4 weeks. Significance of the difference in plasma triglycerides among all groups at 180 minutes after P407 injection in K was calculated using a 2-way ANOVA with Tukey’s post hoc test. *P < 0.05; **P < 0.01; ***P < 0.001.