bims-mireme Biomed News
on Mitochondria in regenerative medicine
Issue of 2021‒06‒13
eight papers selected by
Brian Spurlock
University of Alabama at Birmingham

  1. Methods Mol Biol. 2021 ;2310 47-56
      Mouse embryonic stem cells (mESCs) can be grown in culture, recapitulating the different states of pluripotency of their in vivo counterparts, with notably different metabolic profiles. mESCs in a naïve pluripotent state present an ambivalent metabolism, using both glycolysis and oxidative phosphorylation as energy sources. Here, we describe a method to evaluate the oxidative function of naïve mESCs using the Seahorse Extracellular Flux Analyzer coupled to flow cytometry analysis of mitochondrial transmembrane potential using the TMRM fluorescence probe, thus assessing both oxygen consumption and mitochondrial membrane potential. This may be a useful protocol for understanding how mitochondrial oxidative function and potential of mESCs change in certain circumstances, and how is it related with various pluripotency/differentiation phenotypes.
    Keywords:  Metabolism; Mitochondrial Transmembrane potential; Pluripotency; Seahorse; Stem cells
  2. Methods Mol Biol. 2021 ;2275 247-263
      Mitochondrial physiology and metabolism are closely linked to replication and transcription of mitochondrial DNA (mtDNA). However, the characterization of mtDNA processing is poorly defined at the single-cell level. We developed mTRIP (mitochondrial Transcription and Replication Imaging Protocol), an imaging approach based on modified fluorescence in situ hybridization (FISH), which simultaneously reveals mitochondrial structures committed to mtDNA initiation of replication as well as the mitochondrial RNA (mtRNA) content at the single-cell level in human cells. Also specific RNA regions, rather than global RNA, can be tracked with mTRIP. In addition, mTRIP can be coupled to immunofluorescence for in situ protein tracking, or to MitoTracker, thereby allowing for simultaneous labeling of mtDNA, mtRNA, and proteins or mitochondria, respectively. Altogether, qualitative and quantitative alterations of the dynamics of mtDNA processing are detected by mTRIP in human cells undergoing physiological changes, as well as stress and dysfunction. mTRIP helped elucidating mtDNA processing alterations in cancer cells, and has a potential for diagnostic of mitochondrial diseases.
    Keywords:  DNA replication; FISH; Imaging; Mitochondrial DNA; Mitochondrial disease; Single-cell; Transcription; mTRIP
  3. Development. 2021 Jun 01. pii: dev199609. [Epub ahead of print]148(11):
      The intimate relationships between cell fate and metabolism have long been recognized, but a mechanistic understanding of how metabolic pathways are dynamically regulated during development and disease, how they interact with signalling pathways, and how they affect differential gene expression is only emerging now. We summarize the key findings and the major themes that emerged from the virtual Keystone Symposium 'Metabolic Decisions in Development and Disease' held in March 2021.
    Keywords:  Cell fate; Development; Metabolic plasticity; Metabolism; Nutrition
  4. Methods Mol Biol. 2021 ;2275 415-432
      The cross talk between mitochondrial dynamic structure, determined primarily by mitochondrial fission and fusion events, and mitochondrial function of energetics, primarily ATP and ROS production, is widely appreciated. Understanding the mechanistic details of such cross talk between mitochondrial structure and function needs integrated quantitative analyses between mitochondrial dynamics and energetics. Here we describe our recently designed approach of mito-SinCe2 that involves high resolution confocal microscopy of genetically expressed ratiometric fluorescent probes targeted to mitochondria, and its quantitative analyses. Mito-SinCe2 analyses allows for quantitative analyses of mitochondrial structure-function relationship in single cells toward understanding the role of mitochondria and their heterogeneity in various physiological and pathological conditions.
    Keywords:  ATP; Confocal Microscopy; Fission; Fusion; Mitochondrial Dynamics; Mitochondrial Energetics; Quantitative analyses; Ratiometric Probes; Redox State; Single Cell; Structure–Function Relationships
  5. Front Cell Dev Biol. 2021 ;9 653828
      It has become apparent that our textbook illustration of singular isolated organelles is obsolete. In reality, organelles form complex cooperative networks involving various types of organelles. Light microscopic and ultrastructural studies have revealed that mitochondria-endoplasmic reticulum (ER) contact sites (MERCSs) are abundant in various tissues and cell types. Indeed, MERCSs have been proposed to play critical roles in various biochemical and signaling functions such as Ca2+ homeostasis, lipid transfer, and regulation of organelle dynamics. While numerous proteins involved in these MERCS-dependent functions have been reported, how they coordinate and cooperate with each other has not yet been elucidated. In this review, we summarize the functions of mammalian proteins that localize at MERCSs and regulate their formation. We also discuss potential roles of the MERCS proteins in regulating multiple organelle contacts.
    Keywords:  ER; mammalian protein; mitochondria; organelle contact sites; tether
  6. Nature. 2021 Jun;594(7862): S16-S17
    Keywords:  Cardiovascular biology; Drug discovery; Stem cells
  7. Adv Protein Chem Struct Biol. 2021 ;pii: S1876-1623(21)00025-0. [Epub ahead of print]126 307-343
      The maintenance of cellular homeostasis involves the participation of multiple organelles, such as the endoplasmic reticulum (ER) and mitochondria. Specifically, ER plays a key role in calcium (Ca2+) storage, lipid synthesis, protein folding, and assembly, while mitochondria are the "energy factories" and provide energy to drive intracellular processes. Hence, alteration in ER or mitochondrial homeostasis has detrimental effects on cell survival, being linked to the triggering of apoptosis, a programmed form of cell death. Besides, ER stress conditions affect mitochondria functionality and vice-versa, as ER and mitochondria communicate via mitochondria-associated ER membranes (MAMs) to carry out a number of fundamental cellular functions. It is not surprising, thus, that also MAMs perturbations are involved in the regulation of apoptosis. This chapter intends to accurately discuss the involvement of MAMs in apoptosis, highlighting their crucial role in controlling this delicate cellular process.
    Keywords:  Apoptosis; Bioenergetics; Calcium signaling; ER-mitochondria contact sites; MAMs; Organelle tethering