Ferredoxin 1 is essential for embryonic development and lipid homeostasis

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    eLife assessment

    The findings provided by Mohibi et al. are important to the field of lipid metabolism and cancer and provide insight for an in vivo role of FDX1. The evidence is solid, utilizing multiple modalities and both in vitro and in vivo lines of investigation.

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Abstract

Mammalian ferredoxin 1 and 2 (FDX1/2) belong to an evolutionary conserved family of iron-sulfur cluster containing proteins and act as electron shutters between ferredoxin reductase (FDXR) and numerous proteins involved in critical biological pathways. FDX1 is involved in biogenesis of steroids and bile acids, Vitamin A/D metabolism, and lipoylation of tricarboxylic acid (TCA) cycle enzymes. FDX1 has been extensively characterized biochemically but its role in physiology and lipid metabolism has not been explored. In this study, we generated Fdx1 -deficient mice and showed that knockout of both alleles of the Fdx1 gene led to embryonic lethality. We also showed that like Fdxr +/- +/-, Fdx1 +/- +/- had a shorter life span and were prone to steatohepatitis. However, unlike Fdxr +/- +/-, Fdx1 +/- +/- were not prone to spontaneous tumors. Additionally, we showed that FDX1 deficiency led to lipid droplet accumulation possibly via the ABCA1-SREBP1/2 pathway. Specifically, untargeted lipidomic analysis showed that FDX1 deficiency led to alterations in several classes of lipids, including cholesterol, triacylglycerides, acylcarnitines, ceramides, phospholipids and lysophospholipids. Taken together, our data indicate that FDX1 is essential for mammalian embryonic development and lipid homeostasis at both cellular and organismal levels.

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  1. eLife assessment

    The findings provided by Mohibi et al. are important to the field of lipid metabolism and cancer and provide insight for an in vivo role of FDX1. The evidence is solid, utilizing multiple modalities and both in vitro and in vivo lines of investigation.

  2. Reviewer #1 (Public Review):

    Mohibi et al. utilized genetic approaches to determine the role of FDX1 in the regulation of development, oncogenesis, and metabolism. The strengths of the current study are the utilization of both in vivo and in vitro methods coupled to classical biochemical/molecular biology tools and lipidomic screening. The data provided is convincing demonstrating genetic loss of even one allele of FDX1 promotes premature death, increased incidence of adenocarcinoma, and dysregulated lipid metabolism. The authors provide further mechanistic evidence showing enhanced SREBP2 activation, which could potentially be underlying the altered lipid metabolism observed in their model. These findings are likely to provide a novel target for the amelioration to lipid metabolic disorders as the authors show genetic overexpression of FDX1 can reduce intracellular lipid accumulation.

  3. Reviewer #2 (Public Review):

    In this manuscript, the Chen group aimed to understand the role of FDX1 in vivo. While its role in the biogenesis of steroids and bile acids, Vitamin A/D metabolism, and lipoylation of TCA enzymes has been extensively studied biochemically, its role in physiology and lipid metabolism is still unknown. The authors established a conditional Fdx1 KO mice and performed a series of experiments to demonstrate the physiological role of Fdx1 in mice. The obtained evidence convincingly supports the major conclusion of the study. The manuscript is well and concisely written.

    Strengths:
    • Solid data showing that Fdx1+/- mice are prone to steatohepatitis and Fdx1+/- cells accumulate lipids
    • Untargeted MS profiling the changes of lipids upon Fdx1 KO.
    • Clear evidence indicating that the ABCA1-SREBP1/2 pathway is involved in the function of Fdx1 in lipid metabolism.

    Weaknesses:
    • use of Fdx1+/- MEFs, instead of using Fdx1-/- MEFs, could be well justified.