Novel mutation in mitochondrial Elongation Factor EF-Tu associated to dysplastic leukoencephalopathy and defective mitochondrial DNA translation

Identification of key genes regulating brown adipose tissue thermogenesis in goat kids (Capra hircus) by using weighted gene co-expression network analysis

Brown adipose tissue (BAT) is crucial for the maintenance of body temperature in newborn animals through non-shivering thermogenesis (NST). However, which kind key genes involved in the regulation of BAT thermogenesis and the internal regulation mechanism of heat production in goat BAT were still unclear. In this study, we analyzed the perirenal adipose tissue transcriptome of Dazu black goats from 0, 7, 14, 21 and 28 days after birth using weighted gene co-expression network analysis (WGCNA) to identify key genes involved in the thermogenesis of BAT. Genes were classified into 22 co-expression modules by WGCNA. The turquoise module exhibited high gene expression in D0, with generally lower expression in the later dates. This pattern is consistent with the rapid color, morphological, and thermogenic changes observed in perirenal adipose tissue shortly after birth. GO functional annotation revealed that the genes in the turquoise module were significantly enriched in the mitochondrion, mitochondrial protein-containing complex, cytoplasm, and mitochondrial inner membrane. KEGG pathway enrichment analysis indicated that these genes were predominantly enriched in the signaling pathways of oxidative phosphorylation, thermogenesis, and TCA cycle. By combining the gene co-expression network analysis of the turquoise module genes and the differentially expression genes (DEG) analysis, we identified 5 candidate key genes (ACO2, MRPS27, IMMT, MRPL12, and TUFM) involved in regulation of perirenal adipose tissue thermogenesis. This finding offer candidate genes that in the regulation of BAT thermogenesis and body temperature maintenance in goat kids.

FAM210A: An emerging regulator of mitochondrial homeostasis

Mitochondrial homeostasis serves as a cornerstone of cellular function, orchestrating a delicate balance between energy production, redox status, and cellular signaling transduction. This equilibrium involves a myriad of interconnected processes, including mitochondrial dynamics, quality control mechanisms, and biogenesis and degradation. Perturbations in mitochondrial homeostasis have been implicated in a wide range of diseases, including neurodegenerative diseases, metabolic syndromes, and aging-related disorders. In the past decades, the discovery of numerous mitochondrial proteins and signaling has led to a more complete understanding of the intricate mechanisms underlying mitochondrial homeostasis. Recent studies have revealed that Family with sequence similarity 210 member A (FAM210A) is a novel nuclear-encoded mitochondrial protein involved in multiple aspects of mitochondrial homeostasis, including mitochondrial quality control, dynamics, cristae remodeling, metabolism, and proteostasis. Here, we review the function and physiological role of FAM210A in cellular and organismal health. This review discusses how FAM210A acts as a regulator on mitochondrial inner membrane to coordinate mitochondrial dynamics and metabolism.

A zebrafish tufm mutant model for the COXPD4 syndrome of aberrant mitochondrial function

Mitochondrial dysfunction is a critical factor leading to a wide range of clinically heterogeneous and often severe disorders due to its central role in generating cellular energy. Mutations in the TUFM gene are known to cause combined oxidative phosphorylation deficiency 4 (COXPD4), a rare mitochondrial disorder characterized by a comprehensive quantitative deficiency in mitochondrial respiratory chain (MRC) complexes. The development of a reliable animal model for COXPD4 is crucial for elucidating the roles and mechanisms of TUFM in disease pathogenesis and benefiting its medical management. In this study, we construct a zebrafish tufm-/- mutant that closely resembles the COXPD4 syndrome, exhibiting compromised mitochondrial protein translation, dysfunctional mitochondria with oxidative phosphorylation defects, and significant metabolic suppression of the tricarboxylic acid cycle. Leveraging this COXPD4 zebrafish model, we comprehensively validate the clinical relevance of TUFM mutations and identify probucol as a promising therapeutic approach for managing COXPD4. Our data offer valuable insights for understanding mitochondrial diseases and developing effective treatments.

A very rare presentation of mitochondrial elongation factor Tu deficiency-TUFM mutation and literature review

OBJECTIVES

The mitochondrial elongation factor Tu (EF-Tu), encoded by the TUFM gene, is a GTPase, which is part of the mitochondrial protein translation mechanism. If it is activated, it delivers the aminoacyl-tRNAs to the mitochondrial ribosome. Here, a patient was described with a homozygous missense variant in the TUFM [c.1016G>A (p.Arg339Gln)] gene. To date, only six patients have been reported with bi-allelic pathogenic variants in TUFM, leading to combined oxidative phosphorylation deficiency 4 (COXPD4) characterized by severe early-onset lactic acidosis, encephalopathy, and cardiomyopathy.

CASE PRESENTATION

The patient presented here had the phenotypic features of TUFM-related disease, lactic acidosis, hypotonia, liver dysfunction, optic atrophy, and mild encephalopathy.

CONCLUSIONS

We aimed to expand the clinical spectrum of pathogenic variants of TUFM.

TUFM in health and disease: exploring its multifaceted roles

The nuclear-encoded mitochondrial protein Tu translation elongation factor, mitochondrial (TUFM) is well-known for its role in mitochondrial protein translation. Originally discovered in yeast, TUFM demonstrates significant evolutionary conservation from prokaryotes to eukaryotes. Dysregulation of TUFM has been associated with mitochondrial disorders. Although early hypothesis suggests that TUFM is localized within mitochondria, recent studies identify its presence in the cytoplasm, with this subcellular distribution being linked to distinct functions of TUFM. Significantly, in addition to its established function in mitochondrial protein quality control, recent research indicates a broader involvement of TUFM in the regulation of programmed cell death processes (e.g., autophagy, apoptosis, necroptosis, and pyroptosis) and its diverse roles in viral infection, cancer, and other disease conditions. This review seeks to offer a current summary of TUFM's biological functions and its complex regulatory mechanisms in human health and disease. Insight into these intricate pathways controlled by TUFM may lead to the potential development of targeted therapies for a range of human diseases.

Molecular pathways in mitochondrial disorders due to a defective mitochondrial protein synthesis

Mitochondria play a central role in cellular metabolism producing the necessary ATP through oxidative phosphorylation. As a remnant of their prokaryotic past, mitochondria contain their own genome, which encodes 13 subunits of the oxidative phosphorylation system, as well as the tRNAs and rRNAs necessary for their translation in the organelle. Mitochondrial protein synthesis depends on the import of a vast array of nuclear-encoded proteins including the mitochondrial ribosome protein components, translation factors, aminoacyl-tRNA synthetases or assembly factors among others. Cryo-EM studies have improved our understanding of the composition of the mitochondrial ribosome and the factors required for mitochondrial protein synthesis and the advances in next-generation sequencing techniques have allowed for the identification of a growing number of genes involved in mitochondrial pathologies with a defective translation. These disorders are often multisystemic, affecting those tissues with a higher energy demand, and often present with neurodegenerative phenotypes. In this article, we review the known proteins required for mitochondrial translation, the disorders that derive from a defective mitochondrial protein synthesis and the animal models that have been established for their study.

Illuminating mitochondrial translation through mouse models

Mitochondria are hubs of metabolic activity with a major role in ATP conversion by oxidative phosphorylation (OXPHOS). The mammalian mitochondrial genome encodes 11 mRNAs encoding 13 OXPHOS proteins along with 2 rRNAs and 22 tRNAs, that facilitate their translation on mitoribosomes. Maintaining the internal production of core OXPHOS subunits requires modulation of the mitochondrial capacity to match the cellular requirements and correct insertion of particularly hydrophobic proteins into the inner mitochondrial membrane. The mitochondrial translation system is essential for energy production and defects result in severe, phenotypically diverse diseases, including mitochondrial diseases that typically affect postmitotic tissues with high metabolic demands. Understanding the complex mechanisms that underlie the pathologies of diseases involving impaired mitochondrial translation is key to tailoring specific treatments and effectively targeting the affected organs. Disease mutations have provided a fundamental, yet limited, understanding of mitochondrial protein synthesis, since effective modification of the mitochondrial genome has proven challenging. However, advances in next generation sequencing, cryoelectron microscopy, and multi-omic technologies have revealed unexpected and unusual features of the mitochondrial protein synthesis machinery in the last decade. Genome editing tools have generated unique models that have accelerated our mechanistic understanding of mitochondrial translation and its physiological importance. Here we review the most recent mouse models of disease pathogenesis caused by defects in mitochondrial protein synthesis and discuss their value for preclinical research and therapeutic development.

Novel Tu translation elongation factor, mitochondrial (TUFM) homozygous variant in a consanguineous family with premature ovarian insufficiency

Premature ovarian insufficiency (POI) is a clinical syndrome of ovarian dysfunction characterized by cessation of menstruation occurring before the age of 40 years. The genetic causes of idiopathic POI remain unclear. Here we recruited a POI patient from a consanguineous family to screen for potential pathogenic variants associated with POI. Genetic variants of the pedigree were screened using whole-exome sequencing analysis and validated through direct Sanger sequencing. A homozygous variant in TUFM (c.524G>C: p.Gly175Ala) was identified in this family. TUFM (Tu translation elongation factor, mitochondrial) is a nuclear-encoded mitochondrial protein translation elongation factor that plays a critical role in maintaining normal mitochondrial function. The variant position was highly conserved among species and predicted to be disease causing. Our in vitro functional studies demonstrated that this variant causes decreased TUFM protein expression, leading to mitochondrial dysfunction and impaired autophagy activation. Moreover, we found that mice with targeted Tufm variant recapitulated the phenotypes of human POI. Thus, this is the first report of a homozygous pathogenic TUFM variant in POI. Our findings highlighted the essential role of mitochondrial genes in folliculogenesis and ovarian function maintenance.

TUFM variants lead to white matter abnormalities mimicking multiple sclerosis

BACKGROUND AND PURPOSE

Defects in the mitochondrial respiratory chain (MRC) can lead to combined MRC dysfunctions (COXPDs) with heterogenous genotypes and clinical features. We report a patient carrying heterozygous variants in the TUFM gene who presented with clinical features compatible with COXPD4 and radiological findings mimicking multiple sclerosis (MS).

METHODS

A 37-year-old French Canadian woman was investigated for recent onset of gait and balance problems. Her previous medical history included recurrent episodes of hyperventilation associated with lactic acidosis during infections, asymptomatic Wolff-Parkinson-White syndrome, and nonprogressive sensorineural deafness.

RESULTS

Neurological examinations revealed fine bilateral nystagmus, facial weakness, hypertonia, hyperreflexia, dysdiadochokinesia, dysmetria, and ataxic gait. Brain magnetic resonance imaging (MRI) showed multifocal white matter abnormalities in cerebral white matter as well as cerebellar hemispheres, brainstem, and middle cerebellar peduncles, some of which mimicked MS. Analysis of native-state oxidative phosphorylation showed a combined decrease in CI/CII, CIV/CII, and CVI/CII. Exome sequencing detected two heterozygous TUFM gene variants. Little clinical progression was noted over a 5-year follow-up. Brain MRI remained unchanged.

CONCLUSIONS

Our report broadens the phenotypic and radiological spectrum of TUFM-related disorders by adding milder, later onset forms to the previously known early onset, severe presentations. The presence of multifocal white matter abnormalities can be misinterpreted as due to acquired demyelinating diseases, and thus TUFM-related disorders should be added to the list of mitochondrial MS mimickers.

Fluoride impairs mitochondrial translation by targeting miR-221-3p/c-Fos/RMND1 axis contributing to neurodevelopment defects

Evidence suggests that fluoride-induced neurodevelopment damage is linked to mitochondrial disorder, yet the detailed mechanism remains unclear. A cohort of Sprague-Dawley rats developmentally exposed to sodium fluoride (NaF) was established to simulate actual exposure of human beings. Using high-input proteomics and small RNA sequencing technology in rat hippocampus, we found mitochondrial translation as the most striking enriched biological process after NaF treatment, which involves the differentially expressed Required Meiotic Nuclear Division 1 homolog (RMND1) and neural-specific miR-221-3p. Further experiments in vivo and in vitro neuroendocrine pheochromocytoma (PC12) cells demonstrated that NaF impaired mitochondrial translation and function, as shown by declined mitochondrial membrane potential and inhibited expression of mitochondrial translation factors, mitochondrial translation products, and OXPHOS complexes, which was concomitant with decreased RMND1 and transcription factor c-Fos in mRNA and proteins as well as elevated miR-221-3p. Notably, RMND1 overexpression alleviated the NaF-elicited mitochondrial translation impairment by up-regulating translation factors, but not vice versa. Interestingly, ChIP-qPCR confirmed that c-Fos specifically controls the RMND1 transcription through direct binding with Rmnd1 promotor. Interference of gene expression verified c-Fos as an upstream positive regulator of RMND1, implicating in fluoride-caused mitochondrial translation impairment. Furthermore, dual-luciferase reporter assay evidenced that miR-221-3p targets c-Fos by binding its 3' untranslated region. By modulating the miR-221-3p expression, we identified miR-221-3p as a critical negative regulator of c-Fos. More importantly, we proved that miR-221-3p inhibitor improved mitochondrial translation and mitochondrial function to combat NaF neurotoxicity via activating the c-Fos/RMND1 axis, whereas miR-221-3p mimic tended towards opposite effects. Collectively, our data suggest fluoride impairs mitochondrial translation by dysregulating the miR-221-3p/c-Fos/RMND1 axis to trigger mitochondrial dysfunction, leading to neuronal death and neurodevelopment defects.

TUFM is involved in Alzheimer's disease-like pathologies that are associated with ROS

Mitochondrial Tu translation elongation factor (TUFM or EF-Tu) is part of the mitochondrial translation machinery. It is reported that TUFM expression is reduced in the brain of Alzheimer's disease (AD), suggesting that TUFM might play a role in the pathophysiology. In this study, we found that TUFM protein level was decreased in the hippocampus and cortex especially in the aged APP/PS1 mice, an animal model of AD. In HEK cells that stably express full-length human amyloid-β precursor protein (HEK-APP), TUFM knockdown or overexpression increased or reduced the protein levels of β-amyloid protein (Aβ) and β-amyloid converting enzyme 1 (BACE1), respectively. TUFM-mediated reduction of BACE1 was attenuated by translation inhibitor cycloheximide (CHX) or α-[2-[4-(3,4-Dichlorophenyl)-2-thiazolyl]hydrazinylidene]-2-nitro-benzenepropanoic acid (4EGI1), and in cells overexpressing BACE1 constructs deleting the 5' untranslated region (5'UTR). TUFM silencing increased the half-life of BACE1 mRNA, suggesting that RNA stability was affected by TUFM. In support, transcription inhibitor Actinomycin D (ActD) and silencing of nuclear factor κB (NFκB) failed to abolish TUFM-mediated regulation of BACE1 protein and mRNA. We further found that the mitochondria-targeted antioxidant TEMPO diminished the effects of TUFM on BACE1, suggesting that reactive oxygen species (ROS) played an important role. Indeed, cellular ROS levels were affected by TUFM knockdown or overexpression, and TUFM-mediated regulation of apoptosis and Tau phosphorylation at selective sites was attenuated by TEMPO. Collectively, TUFM protein levels were decreased in APP/PS1 mice. TUFM is involved in AD pathology by regulating BACE1 translation, apoptosis, and Tau phosphorylation, in which ROS plays an important role.

Mitochondrial Protein Translation: Emerging Roles and Clinical Significance in Disease

Mitochondria are one of the most important organelles in cells. Mitochondria are semi-autonomous organelles with their own genetic system, and can independently replicate, transcribe, and translate mitochondrial DNA. Translation initiation, elongation, termination, and recycling of the ribosome are four stages in the process of mitochondrial protein translation. In this process, mitochondrial protein translation factors and translation activators, mitochondrial RNA, and other regulatory factors regulate mitochondrial protein translation. Mitochondrial protein translation abnormalities are associated with a variety of diseases, including cancer, cardiovascular diseases, and nervous system diseases. Mutation or deletion of various mitochondrial protein translation factors and translation activators leads to abnormal mitochondrial protein translation. Mitochondrial tRNAs and mitochondrial ribosomal proteins are essential players during translation and mutations in genes encoding them represent a large fraction of mitochondrial diseases. Moreover, there is crosstalk between mitochondrial protein translation and cytoplasmic translation, and the imbalance between mitochondrial protein translation and cytoplasmic translation can affect some physiological and pathological processes. This review summarizes the regulation of mitochondrial protein translation factors, mitochondrial ribosomal proteins, mitochondrial tRNAs, and mitochondrial aminoacyl-tRNA synthetases (mt-aaRSs) in the mitochondrial protein translation process and its relationship with diseases. The regulation of mitochondrial protein translation and cytoplasmic translation in multiple diseases is also summarized.

The Power of Yeast in Modelling Human Nuclear Mutations Associated with Mitochondrial Diseases

The increasing application of next generation sequencing approaches to the analysis of human exome and whole genome data has enabled the identification of novel variants and new genes involved in mitochondrial diseases. The ability of surviving in the absence of oxidative phosphorylation (OXPHOS) and mitochondrial genome makes the yeast Saccharomyces cerevisiae an excellent model system for investigating the role of these new variants in mitochondrial-related conditions and dissecting the molecular mechanisms associated with these diseases. The aim of this review was to highlight the main advantages offered by this model for the study of mitochondrial diseases, from the validation and characterisation of novel mutations to the dissection of the role played by genes in mitochondrial functionality and the discovery of potential therapeutic molecules. The review also provides a summary of the main contributions to the understanding of mitochondrial diseases emerged from the study of this simple eukaryotic organism.

A novel TUFM homozygous variant in a child with mitochondrial cardiomyopathy expands the phenotype of combined oxidative phosphorylation deficiency 4

Translation of mitochondrial-specific DNA is required for proper mitochondrial function and energy production. For this purpose, an elaborate network of dedicated molecular machinery including initiation, elongation and termination factors exists. We describe a patient with an unusual phenotype and a novel homozygous missense variant in TUFM (c.344A>C; p.His115Pro), encoding mtDNA translation elongating factor Tu (EFTu). To date, only four patients have been reported with bi-allelic mutations in TUFM, leading to combined oxidative phosphorylation deficiency 4 (COXPD4) characterized by severe early-onset lactic acidosis and progressive fatal infantile encephalopathy. The patient presented here expands the phenotypic features of TUFM-related disease, exhibiting lactic acidosis and dilated cardiomyopathy without progressive encephalopathy. This warrants the inclusion of TUFM in differential diagnosis of metabolic cardiomyopathy. Cases that further refine genotype-phenotype associations and characterize the molecular basis of mitochondrial disorders allow clinicians to predict disease prognosis, greatly impacting patient care, as well as provide families with reproductive planning options.

Recent Progress on Gold-Nanocluster-Based Fluorescent Probe for Environmental Analysis and Biological Sensing

Gold nanoclusters (AuNCs) are one of metal nanoclusters, which play a pivotal role in the recent advances in the research of fluorescent probes for their fluorescence effect. They are favored by most researchers due to their strong stability in fluorescence and adjustability in fluorescence wavelength when compared to traditional organic fluorescent dyes. In this review, we introduce various synthesis strategies of gold-nanocluster-based fluorescent probes and summarize their application for environmental analysis and biological sensing. The use of gold-nanocluster-based fluorescent probes for the analysis of heavy metals and inorganic and organic pollutants is covered in the environmental analysis while biological labeling, imaging, and detection are presented in biological sensing.