This review provides an overview of the current methods for quantifying mitochondrial ultrastructure, including cristae morphology, mitochondrial contact sites, and recycling machinery and a guide to ...utilizing electron microscopy to effectively measure these organelles. Quantitative analysis of mitochondrial ultrastructure is essential for understanding mitochondrial biology and developing therapeutic strategies for mitochondrial-related diseases. Techniques such as transmission electron microscopy (TEM) and serial block face-scanning electron microscopy, as well as how they can be combined with other techniques including confocal microscopy, super-resolution microscopy, and correlative light and electron microscopy are discussed. Beyond their limitations and challenges, we also offer specific magnifications that may be best suited for TEM analysis of mitochondrial, endoplasmic reticulum, and recycling machinery. Finally, perspectives on future quantification methods are offered.
•Suggestions for transmission electron microscopy measurement of mitochondria, their contact sites, and recycling machinery.•Measurement techniques for mitochondria, their contact sites, recycling machinery, endoplasmic reticulum, and Golgi Apparatus.•Critique of the current literature regarding TEM quantification and considerations for future 3D analysis.•TEM from our laboratory across a range of tissues demonstrating the functional impact of these literature-backed suggestions.
Transmission electron microscopy (TEM) is widely used as an imaging modality to provide high-resolution details of subcellular components within cells and tissues. Mitochondria and endoplasmic ...reticulum (ER) are organelles of particular interest to those investigating metabolic disorders. A straightforward method for quantifying and characterizing particular aspects of these organelles would be a useful tool. In this protocol, we outline how to accurately assess the morphology of these important subcellular structures using open source software
, originally developed by the National Institutes of Health (NIH). Specifically, we detail how to obtain mitochondrial length, width, area, and circularity, in addition to assessing cristae morphology and measuring mito/endoplasmic reticulum (ER) interactions. These procedures provide useful tools for quantifying and characterizing key features of sub-cellular morphology, leading to accurate and reproducible measurements and visualizations of mitochondria and ER.
Abstract
Choosing a mentor requires a certain level of introspection for both the mentor and the mentee. The dynamics of mentorship may change depending on the academic status of the mentee. ...Regardless, mentors should help their trainees grow both academically and professionally. The success of an individual in the fields of science, technology, engineering, mathematics, and medicine (STEMM) depends on more than intellectual capacity; a holistic view encompassing all factors that contribute to scientific achievement is all-important. Specifically, one new method scientists can adopt is quotients, which are scales and techniques that can be used to measure aptitude in a specific area. In this paper, we focus on these factors and how to grow one’s adversity quotient (AQ), social quotient (SQ), and personal growth initiative scale (PGIS). We also look at how mentors can better understand the biases of their trainees. In addressing this, mentors can help trainees become more visible and encourage other trainees to become allies through reducing biases.
Quotients that contribute to success are discussed, and suggestions in the context of COVID-19 are provided to facilitate student success in science, technology, engineering, mathematics, and medicine (STEMM).
Mitochondria and peroxisomes are both dynamic signaling organelles that constantly undergo fission. While mitochondrial fission and fusion are known to coordinate cellular metabolism, proliferation, ...and apoptosis, the physiological relevance of peroxisome dynamics and the implications for cell fate are not fully understood. DRP1 (dynamin‐related protein 1) is an essential GTPase that executes both mitochondrial and peroxisomal fission. Patients with de novo heterozygous missense mutations in the gene that encodes DRP1, DNM1L, present with encephalopathy due to mitochondrial and peroxisomal elongation (EMPF). EMPF is a devastating neurodevelopmental disease with no effective treatment. To interrogate the molecular mechanisms by which DRP1 mutations cause developmental defects, we are using patient‐derived fibroblasts and iPSC‐derived models from patients with mutations in different domains of DRP1 who present with clinically disparate conditions. Using super resolution imaging, we find that patient cells, in addition to displaying elongated mitochondrial and peroxisomal morphology, present with aberrant cristae structure. Given the direct link between cristae morphology and oxidative phosphorylation efficiency, we explored the impact of these mutations on cellular energy production. Patient cells display a lower coupling efficiency of the electron transport chain, increased proton leak, and Complex III deficiency. In addition to these metabolic abnormalities, mitochondrial hyperfusion results in hyperpolarized mitochondrial membrane potential. Intriguingly, human fibroblasts are capable of cellular reprogramming into iPSCs and appear to display peroxisome‐mediated mitochondrial adaptations that could help sustain these cell fate transitions. Understanding the mechanism by which DRP1 mutations cause cellular dysfunction will give insight into the role of mitochondrial and peroxisome dynamics in neurodevelopment.
While some established undergraduate summer programs are effective across many institutions, these programs may only be available to some principal investigators or may not fully address the diverse ...needs of incoming undergraduates. This article outlines a 10-week science, technology, engineering, mathematics, and medicine (STEMM) education program designed to prepare undergraduate students for graduate school through a unique model incorporating mentoring dyads and triads, cultural exchanges, and diverse activities while emphasizing critical thinking, research skills, and cultural sensitivity. Specifically, we offer a straightforward and adaptable guide that we have used for mentoring undergraduate students in a laboratory focused on mitochondria and microscopy, but which may be customized for other disciplines. Key components include self-guided projects, journal clubs, various weekly activities such as mindfulness training and laboratory techniques, and a focus on individual and cultural expression. Beyond this unique format, this 10-week program also seeks to offer an intensive research program that emulates graduate-level experiences, offering an immersive environment for personal and professional development, which has led to numerous achievements for past students, including publications and award-winning posters.
The sorting and assembly machinery (SAM) Complex is responsible for assembling β-barrel proteins in the mitochondrial membrane. Comprising three subunits, Sam35, Sam37, and Sam50, the SAM complex ...connects the inner and outer mitochondrial membranes by interacting with the mitochondrial contact site and cristae organizing system complex. Sam50, in particular, stabilizes the mitochondrial intermembrane space bridging (MIB) complex, which is crucial for protein transport, respiratory chain complex assembly, and regulation of cristae integrity. While the role of Sam50 in mitochondrial structure and metabolism in skeletal muscle remains unclear, this study aims to investigate its impact. Serial block-face-scanning electron microscopy and computer-assisted 3D renderings were employed to compare mitochondrial structure and networking in Sam50-deficient myotubes from mice and humans with wild-type (WT) myotubes. Furthermore, autophagosome 3D structure was assessed in human myotubes. Mitochondrial metabolic phenotypes were assessed using Gas Chromatography-Mass Spectrometry-based metabolomics to explore differential changes in WT and Sam50-deficient myotubes. The results revealed increased mitochondrial fragmentation and autophagosome formation in Sam50-deficient myotubes compared to controls. Metabolomic analysis indicated elevated metabolism of propanoate and several amino acids, including ß-Alanine, phenylalanine, and tyrosine, along with increased amino acid and fatty acid metabolism in Sam50-deficient myotubes. Furthermore, impairment of oxidative capacity was observed upon Sam50 ablation in both murine and human myotubes, as measured with the XF24 Seahorse Analyzer. Collectively, these findings support the critical role of Sam50 in establishing and maintaining mitochondrial integrity, cristae structure, and mitochondrial metabolism. By elucidating the impact of Sam50-deficiency, this study enhances our understanding of mitochondrial function in skeletal muscle.
Abstract
Disability remains an underacknowledged and underdiscussed topic in science, technology, engineering, mathematics, and medicine (STEMM). Social stigma and fear of negative outcomes have ...resulted in a consistent lack of disclosure. Disabilities cause social and professional difficulties for those that have them. While some faculty can be allies, past literature shows that steps must be taken to make disabilities visible in STEMM at both student and faculty levels. Here, we offer suggestions to better support faculty and students in enhancing the outcomes of individuals who have invisible disabilities. Critically, techniques such as abolishing stigma, universal learning, and better mentoring may improve the challenges faced by those who self-identify as an individual with a disability.
We discuss disability in science, technology, engineering, mathematics, and medicine, why faculty and students with a disability remain underresourced, and potential solutions to increase universal design and representation of individuals with a disability.
Mitochondria and endoplasmic reticulum (ER) contact sites (MERCs) are protein‐ and lipid‐enriched hubs that mediate interorganellar communication by contributing to the dynamic transfer of Ca2+, ...lipid, and other metabolites between these organelles. Defective MERCs are associated with cellular oxidative stress, neurodegenerative disease, and cardiac and skeletal muscle pathology via mechanisms that are poorly understood. We previously demonstrated that skeletal muscle‐specific knockdown (KD) of the mitochondrial fusion mediator optic atrophy 1 (OPA1) induced ER stress and correlated with an induction of Mitofusin‐2, a known MERC protein. In the present study, we tested the hypothesis that Opa1 downregulation in skeletal muscle cells alters MERC formation by evaluating multiple myocyte systems, including from mice and Drosophila, and in primary myotubes. Our results revealed that OPA1 deficiency induced tighter and more frequent MERCs in concert with a greater abundance of MERC proteins involved in calcium exchange. Additionally, loss of OPA1 increased the expression of activating transcription factor 4 (ATF4), an integrated stress response (ISR) pathway effector. Reducing Atf4 expression prevented the OPA1‐loss‐induced tightening of MERC structures. OPA1 reduction was associated with decreased mitochondrial and sarcoplasmic reticulum, a specialized form of ER, calcium, which was reversed following ATF4 repression. These data suggest that mitochondrial stress, induced by OPA1 deficiency, regulates skeletal muscle MERC formation in an ATF4‐dependent manner.
Following Opa1‐deficiency in skeletal muscle, increases in ATF4 induce changes in mitochondria‐endoplasmic reticulum contact sites.
Cover Image, Volume 239, Number 4, April 2024 Hinton, Antentor; Katti, Prasanna; Mungai, Margaret ...
Journal of cellular physiology,
April 2024, 2024-04-00, 20240401, Letnik:
239, Številka:
4
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Inside Front Cover Caption: The cover image is based on the Research Article ATF4‐dependent increase in mitochondrial‐endoplasmic reticulum tethering following OPA1 deletion in skeletal muscle by ...Antentor Hinton Jr. et al., https://doi.org/10.1002/jcp.31204.
Featured Cover Vue, Zer; Garza‐Lopez, Edgar; Neikirk, Kit ...
Aging cell,
December 2023, Letnik:
22, Številka:
12
Journal Article
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Cover legend: The cover image is based on the Research Article 3D reconstruction of murine mitochondria reveals changes in structure during aging linked to the MICOS complex by Zer Vue et al., ...https://doi.org/10.1111/acel.14009
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