Comprehensive application of an mtDsRed2-Tg mouse strain for mitochondrial imaging

Generation of a Transgenic Mouse Model for Investigating Mitochondria in Sperm

Mitochondria play a crucial role in sperm development; however, the mechanisms regulating their function in sperm remain poorly understood. Developing a method to regulate the expression of a target gene within the mitochondria of sperm is a vital step in this area of research. In this study, we aimed to create a system for expressing a transgene in the mitochondria of sperm. As a proof of concept, we generated transgenic mice that express green fluorescent protein (GFP) fused with a mitochondrial localization signal (MLS) driven by the phosphoglycerate kinase 2 (PGK2) promoter, which facilitates the transgene expression in the sperm. Although the PGK2 promoter has previously shown to drive gene expression in spermatocytes and spermatids, the novelty of our approach lies in the combination of PGK2-driven MLS-GFP expression to study mitochondria in vivo. We established two founder lines of transgenic mice through pronuclear microinjection, and MLS-GFP expression was confirmed in the mitochondria of sperm cells using fluorescence microscopy and flow cytometry. Consequently, we provide a novel platform for investigating mitochondrial function in sperm, where GFP can be substituted with other genes of interest to examine their effects on mitochondria. This system specifically targets sperm mitochondria, offering an innovative approach for studying mitochondrial function in vivo.

Targeting mitochondrial shape: at the heart of cardioprotection

There remains an unmet need to identify novel therapeutic strategies capable of protecting the myocardium against the detrimental effects of acute ischemia-reperfusion injury (IRI), to reduce myocardial infarct (MI) size and prevent the onset of heart failure (HF) following acute myocardial infarction (AMI). In this regard, perturbations in mitochondrial morphology with an imbalance in mitochondrial fusion and fission can disrupt mitochondrial metabolism, calcium homeostasis, and reactive oxygen species production, factors which are all known to be critical determinants of cardiomyocyte death following acute myocardial IRI. As such, therapeutic approaches directed at preserving the morphology and functionality of mitochondria may provide an important strategy for cardioprotection. In this article, we provide an overview of the alterations in mitochondrial morphology which occur in response to acute myocardial IRI, and highlight the emerging therapeutic strategies for targeting mitochondrial shape to preserve mitochondrial function which have the future therapeutic potential to improve health outcomes in patients presenting with AMI.

Lung epithelial endoplasmic reticulum and mitochondrial 3D ultrastructure: a new frontier in lung diseases

It has long been appreciated that the endoplasmic reticulum (ER) and mitochondria, organelles important for regular cell function and survival, also play key roles in pathogenesis of various lung diseases, including asthma, fibrosis, and infections. Alterations in processes regulated within these organelles, including but not limited to protein folding in the ER and oxidative phosphorylation in the mitochondria, are important in disease pathogenesis. In recent years it has also become increasingly apparent that organelle structure dictates function. It is now clear that organelles must maintain precise organization and localization for proper function. Newer microscopy capabilities have allowed the scientific community to reveal, via 3D imaging, that the structure of these organelles and their interactions with each other are a main component of regulating function and, therefore, effects on the disease state. In this review, we will examine how 3D imaging through techniques could allow advancements in knowledge of how the ER and mitochondria function and the roles they may play in lung epithelia in progression of lung disease.

The mito::mKate2 mouse: A far-red fluorescent reporter mouse line for tracking mitochondrial dynamics in vivo

Mitochondria are incredibly dynamic organelles that undergo continuous fission and fusion events to control morphology, which profoundly impacts cell physiology including cell cycle progression. This is highlighted by the fact that most major human neurodegenerative diseases are due to specific disruptions in mitochondrial fission or fusion machinery and null alleles of these genes result in embryonic lethality. To gain a better understanding of the pathophysiology of such disorders, tools for the in vivo assessment of mitochondrial dynamics are required. It would be particularly advantageous to simultaneously image mitochondrial fission-fusion coincident with cell cycle progression. To that end, we have generated a new transgenic reporter mouse, called mito::mKate2 that ubiquitously expresses a mitochondria localized far-red mKate2 fluorescent protein. Here we show that mito::mKate2 mice are viable and fertile and that mKate2 fluorescence can be spectrally separated from the previously developed Fucci cell cycle reporters. By crossing mito::mKate2 mice to the ROSA26R-mTmG dual fluorescent Cre reporter line, we also demonstrate the potential utility of mito::mKate2 for genetic mosaic analysis of mitochondrial phenotypes.

T cells mediate autoantibody-induced cutaneous inflammation and blistering in epidermolysis bullosa acquisita

T cells are key players in autoimmune diseases by supporting the production of autoantibodies. However, their contribution to the effector phase of antibody-mediated autoimmune dermatoses, i.e., tissue injury and inflammation of the skin, has not been investigated. In this paper, we demonstrate that T cells amplify the development of autoantibody-induced tissue injury in a prototypical, organ-specific autoimmune disease, namely epidermolysis bullosa acquisita (EBA) – characterized and caused by autoantibodies targeting type VII collagen. Specifically, we show that immune complex (IC)-induced inflammation depends on the presence of T cells – a process facilitated by T cell receptor (TCR)γδ and NKT cells. Because tissue damage in IC-induced inflammation is neutrophil-dependent, we further analyze the interplay between T cells and neutrophils in an experimental model of EBA. We demonstrate that T cells not only enhance neutrophil recruitment into the site of inflammation but also interact with neutrophils in lymphatic organs. Collectively, this study shows that T cells amplify the effector phase of antibody-induced tissue inflammation.

Mitochondrial Dynamics and Metabolic Regulation

Mitochondrial morphology varies tremendously across cell types and tissues, changing rapidly in response to external insults and metabolic cues, such as nutrient status. The many functions of mitochondria have been intimately linked to their morphology, which is shaped by ongoing events of fusion and fission of outer and inner membranes (OM and IM). Unopposed fission causes mitochondrial fragmentation, which is generally associated with metabolic dysfunction and disease. Unopposed fusion results in a hyperfused network and serves to counteract metabolic insults, preserve cellular integrity, and protect against autophagy. Here, we review the ways in which metabolic alterations convey changes in mitochondrial morphology and how disruption of mitochondrial morphology impacts cellular and organismal metabolism.