Biology subjects

Henstridge, D. C.

Publications and source records attributed to Henstridge, D. C..

4 recordsLinked to original sources

bioRxiv2026

Inducible Impairment of Polymerase Gamma Activity in Cardiomyocytes Promotes Severe Cardiomyopathy with Cardiac Hepatopathy

Mitochondrial dysfunction is a hallmark feature of heart failure (HF) and cardiomyopathy, with substantial human and preclinical evidence suggesting that congenital mitochondrial defects can directly drive these conditions. Despite these strong links, not all individuals with mitochondrial disease develop cardiomyopathy, and therefore the precise mitochondrial defects that initiate cardiac pathology in this setting remain incompletely understood. Here, we describe a novel mouse model that induces progressive deterioration in mtDNA integrity specifically in cardiomyocytes. This model was generated through a post developmental, cardiomyocyte specific deletion of the exonuclease domain of Polymerase Gamma (PolG), impairing its ability to repair mtDNA. Strikingly, from just 16 weeks post-induction these mice displayed progressive worsening of cardiac output, ejection fraction, global strain and blood pressure culminating in premature death at 28-30 weeks post-mutation. Morphologically, these mice displayed cardinal features of hypertrophic cardiomyopathy with enlarged hearts, ventricles and cardiac fibrosis - but little evidence of congestive HF. We also demonstrate using various transcriptional and proteomic readouts, that signalling pathways characteristic of cardiomyopathy were activated. Interestingly, prior to substantial declines in cardiac function, we detect robust activation of the integrated stress response (ISR) in PolGMut mice, and major rewiring of mitochondrial folate metabolism pathways, suggesting that these pathways underpin the developing pathology. Lastly, we also observed a striking hepatopathy phenotype in mutant mice reminiscent of that observed in patients with HF, a condition not robustly recapitulated previously in other mouse models. Thus, our data establish a direct link between mtDNA instability leading to chronic activation of the ISR and rewiring of folate metabolism in cardiomyocytes, subsequently driving a severe cardiac phenotype associated with hepatopathy.

physiology↗

bioRxiv2024

Skeletal Muscle Specific PolG Dysfunction Activates the Integrated Stress Response and Promotes a Cachexia like Phenotype

During mitochondrial damage, information is relayed between the mitochondria and nucleus to coordinate precise responses to preserve cellular health. One such pathway is the mitochondrial integrated stress response (mtISR), which is specifically activated by mitochondrial DNA (mtDNA) damage. However, the causal molecular signals responsible for this activation remain elusive. A gene often associated with mtDNA mutations/deletions is Polg1, which encodes the mitochondrial DNA Polymerase {gamma} (PolG). Here, we describe what is to our knowledge the first conditional muscle specific model of PolG mutation, and demonstrate a rapid development of mitochondrial dysfunction and cachexia in these animals from [~]5 months of age. Detailed molecular profiling of muscles demonstrated robust activation of the mtISR, likely mediated upstream by the HRI/DELE1 stress pathway. This was accompanied by striking alterations to the mitochondrial folate cycle and its metabolites, strongly implying imbalanced folate intermediates as a previously unrecognised pathology driving the mtISR in mitochondrial disease.

physiology↗

bioRxiv2022

Class IIa HDACs reprogram mitochondrial metabolism to inhibit apoptosis and ferroptosis in response to lipotoxicity

Lipotoxicity, the accumulation of lipids in non-adipose tissues, alters the metabolic transcriptome and mitochondrial metabolism in skeletal muscle. The mechanisms involved remain poorly understood. Here we show that lipotoxicity increased histone deacetylase 4 (HDAC4) and histone deacetylase 5 (HDAC5), which reduced the expression of metabolic genes and oxidative metabolism in skeletal muscle, resulting in increased non-oxidative glucose metabolism. This metabolic reprogramming was also associated with impaired apoptosis and ferroptosis responses, and preserved muscle cell viability in response to lipotoxicity. Mechanistically, increased HDAC4 and 5 decreased acetylation of p53 at K120, a modification required for transcriptional activation of apoptosis. Redox drivers of ferroptosis derived from oxidative metabolism were also reduced. The relevance of this pathway was demonstrated by overexpression of loss-of-function HDAC4 and HDAC5 mutants in skeletal muscle of obese db/db mice, which enhanced oxidative metabolic capacity, increased apoptosis and ferroptosis and reduced muscle mass. This study identifies HDAC4 and HDAC5 as repressors of skeletal muscle oxidative metabolism, which is linked to inhibition of cell death pathways and preservation of muscle integrity in response to lipotoxicity.

cell biology↗

bioRxiv2021

Detailed metabolic phenotyping of four tissue specific Cas9 transgenic mouse lines

CRISPR/Cas9 technology has revolutionized gene editing and fast tracked our capacity to manipulate genes of interest for the benefit of both research and therapeutic applications. Whilst many advances have, and continue to be made in this area, perhaps the most utilized technology to date has been the generation of knockout cells, tissues and animals by taking advantage of Cas9 function to promote indels in precise locations in the genome. Whilst the advantages of this technology are many fold, some questions still remain regarding the effects that long term expression of foreign proteins such as Cas9, have on mammalian cell function. Several studies have proposed that chronic overexpression of Cas9, with or without its accompanying guide RNAs, may have deleterious effects on cell function and health. This is of particular concern when applying this technology in vivo, where chronic expression of Cas9 in tissues of interest may promote disease-like phenotypes and thus confound the investigation of the effects of the gene of interest. Although these concerns remain valid, no study to our knowledge has yet to demonstrate this directly. Thus, in this study we used the lox-stop-lox (LSL) spCas9 ROSA26 transgenic (Tg) mouse line to generate four tissue-specific Cas9-Tg models with expression in the heart, liver, skeletal muscle and adipose tissue. We performed comprehensive phenotyping of these mice up to 20-weeks of age and subsequently performed molecular analysis of their organs. We demonstrated that Cas9 expression in these tissues had no detrimental effect on whole body health of the animals, nor did it induce any tissue-specific effects on energy metabolism, liver health, inflammation, fibrosis, heart function or muscle mass. Thus, our data suggests that these models are suitable for studying the tissue specific effects of gene deletion using the LSL-Cas9-Tg model, and that phenotypes observed utilizing these models can be confidently interpreted as being gene specific, and not confounded by the chronic overexpression of Cas9.

molecular biology↗