Identification of a weight loss-associated causal eQTL in MTIF3 and the effects of MTIF3 deficiency on human adipocyte function
Genetic variation at the MTIF3 (Mitochondrial Translational Initiation Factor 3) locus has been robustly associated with obesity in humans, but the functional basis behind this association is not known. Here, we applied luciferase reporter assay to map potential functional variants in the haplotype block tagged by rs1885988 and used CRISPR-Cas9 to edit the potential functional variants to confirm the regulatory effects on MTIF3 expression. We further conducted functional studies on MTIF3-deficient differentiated human white adipocyte cell line (hWAs-iCas9), generated through inducible expression of CRISPR-Cas9 combined with delivery of synthetic MTIF3-targeting guide RNA. We demonstrate that rs67785913-centered DNA fragment (in LD with rs1885988, r2>0.8) enhances transcription in a luciferase reporter assay, and CRISPR-Cas9 edited rs67785913 CTCT cells show significantly higher MTIF3 expression than rs67785913 CT cells. Perturbed MTIF3 expression led to reduced mitochondrial respiration and endogenous fatty acid oxidation, as well as altered expression of mitochondrial DNA-encoded genes and proteins, and disturbed mitochondrial OXPHOS complex assembly. Furthermore, after glucose restriction, the MTIF3 knockout cells retained more triglycerides than control cells. This study demonstrates an adipocyte function-specific role of MTIF3, which originates in the maintenance of mitochondrial function, providing potential explanations for why MTIF3 genetic variation at rs67785913 is associated with body corpulence and response to weight loss interventions.
All data generated or analyzed in this study are included in the figures and the source data files. Source data files are provided for Figures 3 and 4, and for Figure 3-figure supplement 1.
Article and author information
European Research Council (ERC-2015-CoG -681742 NASCENT)
- Paul Franks
- Hindrik Mulder
- Paul Franks
- Hindrik Mulder
China Scholarship Council (201708420158)
- Mi Huang
The Albert Påhlsson Foundation
- Sebastian Kalamajski
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
- Marcus M Seldin, University of California, Irvine, United States
- Received: October 12, 2022
- Preprint posted: October 17, 2022 (view preprint)
- Accepted: March 5, 2023
- Accepted Manuscript published: March 6, 2023 (version 1)
- Version of Record published: March 17, 2023 (version 2)
© 2023, Huang et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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