Lack of MTTP Activity in Pluripotent Stem Cell-Derived Hepatocytes and Cardiomyocytes Abolishes apoB Secretion and Increases Cell Stress

Publication date: 16 May 2017
Source:Cell Reports, Volume 19, Issue 7
Author(s): Ying Liu, Donna M. Conlon, Xin Bi, Katherine J. Slovik, Jianting Shi, Hailey I. Edelstein, John S. Millar, Ali Javaheri, Marina Cuchel, Evanthia E. Pashos, Jahangir Iqbal, M. Mahmood Hussain, Robert A. Hegele, Wenli Yang, Stephen A. Duncan, Daniel J. Rader, Edward E. Morrisey
Abetalipoproteinemia (ABL) is an inherited disorder of lipoprotein metabolism resulting from mutations in microsomal triglyceride transfer protein (MTTP). In addition to expression in the liver and intestine, MTTP is expressed in cardiomyocytes, and cardiomyopathy has been reported in several ABL cases. Using induced pluripotent stem cells (iPSCs) generated from an ABL patient homozygous for a missense mutation (MTTP^R46G), we show that human hepatocytes and cardiomyocytes exhibit defects associated with ABL disease, including loss of apolipoprotein B (apoB) secretion and intracellular accumulation of lipids. MTTP^R46G iPSC-derived cardiomyocytes failed to secrete apoB, accumulated intracellular lipids, and displayed increased cell death, suggesting intrinsic defects in lipid metabolism due to loss of MTTP function. Importantly, these phenotypes were reversed after the correction of the MTTP^R46G mutation by CRISPR/Cas9 gene editing. Together, these data reveal clear cellular defects in iPSC-derived hepatocytes and cardiomyocytes lacking MTTP activity, including a cardiomyocyte-specific regulated stress response to elevated lipids.

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Teaser

Liu et al. use patient-specific iPSCs and CRISPR/Cas9 genome editing to uncover the functional consequences of MTTP mutations in human hepatocytes and cardiomyocytes. They find that MTTP is required for apoB secretion and that its absence results in increased cell stress in cardiomyocytes.


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