The epithelial C15ORF48/miR-147-NDUFA4 axis is an essential regulator of gut inflammation, energy metabolism, and the microbiome.

Chronic inflammation is epidemiologically linked to the pathogenesis of gastrointestinal diseases, including inflammatory bowel disease (IBD) and colorectal cancer (CRC). However, our understanding of the molecular mechanisms controlling gut inflammation remains insufficient, hindering the development of targeted therapies for IBD and CRC. In this study, we uncovered C15ORF48/miR-147 as a negative regulator of gut inflammation, operating through the modulation of epithelial cell metabolism. C15ORF48/miR-147 encodes two molecular products, C15ORF48 protein and miR-147-3p microRNA, which are predominantly expressed in the intestinal epithelium. C15ORF48/miR-147 ablation leads to gut dysbiosis and exacerbates chemically induced colitis in mice. C15ORF48 and miR-147-3p work together to suppress colonocyte metabolism and inflammation by silencing NDUFA4, a subunit of mitochondrial complex IV (CIV). Interestingly, the C15ORF48 protein, a structural paralog of NDUFA4, contains a unique C-terminal α-helical domain crucial for displacing NDUFA4 from CIV and its subsequent degradation. NDUFA4 silencing hinders NF-κB signaling activation and consequently attenuates inflammatory responses. Collectively, our findings have established the C15ORF48/miR-147-NDUFA4 molecular axis as an indispensable regulator of gut homeostasis, bridging mitochondrial metabolism and inflammation.

Mitochondrial respiratory chain component NDUFA4: a promising therapeutic target for gastrointestinal cancer.

Gastrointestinal cancer, one of the most common cancers, continues to be a major cause of mortality and morbidity globally. Accumulating evidence has shown that alterations in mitochondrial energy metabolism are involved in developing various clinical diseases. NADH dehydrogenase 1 alpha subcomplex 4 (NDUFA4), encoded by the NDUFA4 gene located on human chromosome 7p21.3, is a component of mitochondrial respiratory chain complex IV and integral to mitochondrial energy metabolism. Recent researchers have disclosed that NDUFA4 is implicated in the pathogenesis of various diseases, including gastrointestinal cancer. Aberrant expression of NDUFA4 leads to the alteration in mitochondrial energy metabolism, thereby regulating the growth and metastasis of cancer cells, indicating that it might be a new promising target for cancer intervention. This article comprehensively reviews the structure, regulatory mechanism, and biological function of NDUFA4. Of note, the expression and roles of NDUFA4 in gastrointestinal cancer including colorectal cancer, liver cancer, gastric cancer, and so on were discussed. Finally, the existing problems of NDUFA4-based intervention on gastrointestinal cancer are discussed to provide help to strengthen the understanding of the carcinogenesis of gastrointestinal cancer, as well as the development of new strategies for clinical intervention.

Transcriptional regulation of NDUFA4L2 by NFIB induces sorafenib resistance by decreasing reactive oxygen species in hepatocellular carcinoma.

Sorafenib is one a first-line therapeutic drugs for advanced hepatocellular carcinoma (HCC). However, only 30% of patients benefit from sorafenib due to drug resistance. We and other groups have revealed that nuclear factor I B (NFIB) regulates liver regeneration and carcinogenesis, but its role in drug resistance is poorly known. We found that NFIB was more upregulated in sorafenib-resistant SMMC-7721 cells compared to parental cells. NFIB knockdown not only sensitized drug-resistant cells to sorafenib but also inhibited the proliferation and invasion of these cells. Meanwhile, NFIB promoted the proliferation and invasion of HCC cells in vitro and facilitated tumor growth and metastasis in vivo. Knocking down NFIB synergetically inhibited tumor growth with sorafenib. Mechanically, gene expression profiling and subsequent verification experiments proved that NFIB could bind with the promoter region of a complex I inhibitor NDUFA4L2 and promote its transcription. Transcriptional upregulation of NDUFA4L2 by NFIB could thus inhibit the sorafenib-induced reactive oxygen species accumulation. Finally, we found that NFIB was highly expressed in HCC tissues, and high NFIB expression level was associated with macrovascular invasion, advanced tumor stage, and poor prognosis of HCC patients (n = 156). In summary, we demonstrated that NFIB could transcriptionally upregulate NDUFA4L2 to enhance both intrinsic and acquired sorafenib resistance of HCC cells by reducing reactive oxygen species induction.

NDUFA4 promotes the progression of head and neck paraganglioma by inhibiting ferroptosis.

NDUFA4 is a component of respiratory chain-oxidative phosphorylation pathway. NDUFA4 is highly expressed in tumor tissues, but little is known about the function of NDUFA4 in head and neck paraganglioma (HNPGL). We examined NDUFA4 expression in tissues from 10 HNPGL patients and 6 controls using qRT-PCR and Western blotting. NDUFA4 knockdown PGL-626 cells were established by using lentivirus infection and puromycin screening. Cell viability, ATP production, lipid reactive oxygen species, and mitochondrial membrane potential assays were performed to investigate the ferroptotic effects in NDUFA4 deficiency HNPGL cancer cells. Xenograft mouse model was created to detect the synergetic antitumor action between NDUFA4 deficiency and Metformin. NDUFA4 was upregulated in tumor tissues of HNPGL patients. NDUFA4 knockdown impaired the assembly of mitochondrial respiratory chain complexes and decreased the production of ATP and reduced cancer cell viability. Mechanistically, NDUFA4 knockdown increased cell ferroptosis, which further promoted Metformin-induced ferroptosis in PGL-626 cells. Therefore, NDUFA4 deficiency enhanced Metformin-mediated inhibition of the HNPGL progression in mice. In conclusion, NDUFA4 promotes the progression of HNPGL, and NDUFA4 knockdown enhances Metformin-mediated inhibition of the HNPGL progression in a mouse model.

Stable Isotope Labeling of Amino Acids in Flies (SILAF) Reveals Differential Phosphorylation of Mitochondrial Proteins Upon Loss of OXPHOS Subunits.

Drosophila melanogaster has been a workhorse of genetics and cell biology for more than a century. However, proteomic-based methods have been limited due to the complexity and dynamic range of the fly proteome and the lack of efficient labeling methods. Here, we advanced a chemically defined food source into direct stable-isotope labeling of amino acids in flies (SILAF). It allows for the rapid and cost-efficient generation of a large number of larvae or flies, with full incorporation of lysine-[13C6] after six labeling days. SILAF followed by fractionation and enrichment gave proteomic insights at a depth of 7196 proteins and 8451 phosphorylation sites, which substantiated metabolic regulation on enzymatic level. We applied SILAF to quantify the mitochondrial phosphoproteome of an early-stage leucine-rich PPR motif-containing protein (LRPPRC)-knockdown fly model of mitochondrial disease that almost exclusively affects protein levels of the oxidative phosphorylation (OXPHOS) system. While the mitochondrial compartment was hypo-phosphorylated, two conserved phosphosites on OXPHOS subunits NDUFB10 and NDUFA4 were significantly upregulated upon impaired OXPHOS function. The ease and versatility of the method actuate the fruit fly as an appealing model in proteomic and posttranslational modification studies, and it enlarges potential metabolic applications based on heavy amino acid diets.

NDUFA4 promotes cell proliferation by enhancing oxidative phosphorylation in pancreatic adenocarcinoma.

Pancreatic adenocarcinoma (PAAD) is the third leading cause of cancer-related deaths, with a 5-year relative survival rate of 6%. Hence, novel therapeutic targets need to be urgently explored for PAAD. Recently, oxidative phosphorylation (OXPHOS) has been identified to contribute to the development of PAAD. Nicotinamide adenine dinucleotide + hydrogen (NADH) dehydrogenase (ubiquinone) 1 alpha subcomplex 4 (NDUFA4) is known to affect the mitochondrial respiration pathway. However, the function of NDUFA4 in PAAD remains unclear. In this study, NDUFA4 expression was examined in samples from patients with PAAD using real-time polymerase chain reaction and immunohistochemical staining. Furthermore, cell proliferation and cell cycle were analyzed using Cell Counting Kit-8 assay and flow cytometry. A xenograft tumor model derived from a PAAD cell line was developed to validate the in vitro findings. NDUFA4 was observed to be upregulated in the PAAD samples, and high levels were associated with a poor survival rate. NDUFA4 knockdown reduced cell proliferation by inducing G1 arrest in SW1990 cells. Mechanistically, NDUFA4 knockdown decreased the oxygen consumption rate, cellular adenosine triphosphate level, mitochondrial complex IV activity, and protein levels of COX6C and COX5B, which indicated the suppression of OXPHOS. In contrast, NDUFA4 overexpression exerted the opposite effects. Finally, NDUFA4 knockdown significantly inhibited the growth of the xenograft tumor derived from the SW1990 cell line in vivo. Therefore, NDUFA4 contributes to PAAD proliferation by enhancing OXPHOS.

Mitochondrial NDUFA4L2 is a novel regulator of skeletal muscle mass and force.

The hypoxia-inducible nuclear-encoded mitochondrial protein NADH dehydrogenase (ubiquinone) 1 alpha subcomplex, 4-like 2 (NDUFA4L2) has been demonstrated to decrease oxidative phosphorylation and production of reactive oxygen species in neonatal cardiomyocytes, brain tissue and hypoxic domains of cancer cells. Prolonged local hypoxia can negatively affect skeletal muscle size and tissue oxidative capacity. Although skeletal muscle is a mitochondrial rich, oxygen sensitive tissue, the role of NDUFA4L2 in skeletal muscle has not previously been investigated. Here we ectopically expressed NDUFA4L2 in mouse skeletal muscles using adenovirus-mediated expression and in vivo electroporation. Moreover, femoral artery ligation (FAL) was used as a model of peripheral vascular disease to induce hind limb ischemia and muscle damage. Ectopic NDUFA4L2 expression resulted in reduced mitochondrial respiration and reactive oxygen species followed by lowered AMP, ADP, ATP, and NAD+ levels without affecting the overall protein content of the mitochondrial electron transport chain. Furthermore, ectopically expressed NDUFA4L2 caused a ~20% reduction in muscle mass that resulted in weaker muscles. The loss of muscle mass was associated with increased gene expression of atrogenes MurF1 and Mul1, and apoptotic genes caspase 3 and Bax. Finally, we showed that NDUFA4L2 was induced by FAL and that the Ndufa4l2 mRNA expression correlated with the reduced capacity of the muscle to generate force after the ischemic insult. These results show, for the first time, that mitochondrial NDUFA4L2 is a novel regulator of skeletal muscle mass and force. Specifically, induced NDUFA4L2 reduces mitochondrial activity leading to lower levels of important intramuscular metabolites, including adenine nucleotides and NAD+ , which are hallmarks of mitochondrial dysfunction and hence shows that dysfunctional mitochondrial activity may drive muscle wasting.

NDUFA4L2 in smooth muscle promotes vascular remodeling in hypoxic pulmonary arterial hypertension.

Pulmonary arterial hypertension (PAH) is characterized by a progressive increase in pulmonary vascular resistance and obliterative pulmonary vascular remodelling (PVR). The imbalance between the proliferation and apoptosis of pulmonary artery smooth muscle cells (PASMCs) is an important cause of PVR leading to PAH. Mitochondria play a key role in the production of hypoxia-induced pulmonary hypertension (HPH). However, there are still many issues worth studying in depth. In this study, we demonstrated that NADH dehydrogenase (ubiquinone) 1 alpha subcomplex 4 like 2 (NDUFA4L2) was a proliferation factor and increased in vivo and in vitro through various molecular biology experiments. HIF-1α was an upstream target of NDUFA4L2. The plasma levels of 4-hydroxynonene (4-HNE) were increased both in PAH patients and hypoxic PAH model rats. Knockdown of NDUFA4L2 decreased the levels of malondialdehyde (MDA) and 4-HNE in human PASMCs in hypoxia. Elevated MDA and 4-HNE levels might be associated with excessive ROS generation and increased expression of 5-lipoxygenase (5-LO) in hypoxia, but this effect was blocked by siNDUFA4L2. Further research found that p38-5-LO was a downstream signalling pathway of PASMCs proliferation induced by NDUFA4L2. Up-regulated NDUFA4L2 plays a critical role in the development of HPH, which mediates ROS production and proliferation of PASMCs, suggesting NDUFA4L2 as a potential new therapeutic target for PAH.

A transgenic mouse expressing miR-210 in proximal tubule cells shows mitochondrial alteration: possible association of miR-210 with a shift in energy metabolism.

Previously we reported that the microRNA miR-210 is aberrantly upregulated in clear cell renal cell carcinoma (ccRCC) via deregulation of the VHL-HIF pathway. In the present study, to investigate the biological impact of miR-210 in ccRCC tumorigenesis, we developed a transgenic mouse line expressing miR-210 in proximal tubule cells under control of the mouse SGLT2/Slc5a2 promoter. Light microscopy revealed desquamation of the tubule cells and regeneration of the proximal tubule, suggesting that miR-210 expression led to damage of the proximal tubule cells. Electron microscopy revealed alterations to the mitochondria in proximal tubule cells, with marked reduction of the mitochondrial inner membrane, which is the main site of ATP production via oxidative phosphorylation (OxPhos). An additional in vitro study revealed that this loss of the inner membrane was associated with downregulation of Iscu and Ndufa4, the target genes of miR-210, suggesting that the miR-210-ISCU/NDUFA4 axis may affect mitochondrial energy metabolism. Furthermore, metabolome analysis revealed activation of anaerobic glycolysis in miR-210-transfected cells, and consistent with this the secretion of lactate, the final metabolite of anaerobic glycolysis, was significantly increased. Lactate concentration was higher in the kidney cortex of transgenic mice relative to wild-type mice, although the difference was not significant (p = 0.070). On the basis of these findings, we propose that miR-210 may induce a shift of energy metabolism from OxPhos to glycolysis by acting on the mitochondrial inner membrane. In addition to activation of glycolysis, we observed activation of the pentose phosphate pathway (PPP) and an increase in the total amount of amino acids in miR-210-transfected cells. This may help cells synthesize nucleotides and proteins for building new cells. These results suggest that miR-210 may be involved in the metabolic changes in the early stage of ccRCC development, helping the cancer cells to acquire growth and survival advantages. © 2020 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Evaluating the clinical significance of SHMT2 and its co-expressed gene in human kidney cancer.

BACKGROUND: Kidney cancer is one of the most common cancers in the world. It is necessary to clarify its underlying mechanism and find its prognostic biomarkers. Current studies showed that SHMT2 may be participated in several kinds of cancer. METHODS: Our studies investigated the expression of SHMT2 in kidney cancer by Oncomine, Human Protein Atlas database and ULCAN database. Meanwhile, we found its co-expression gene by cBioPortal online tool and validated their relationship in A498 and ACHN cells by cell transfection, western blot and qRT-PCR. Besides these, we also explored their prognostic values via the Kaplan-Meier plotter database in different types of kidney cancer patients. RESULTS: SHMT2 was found to be increased in 7 kidney cancer datasets, compared to normal renal tissues. For the cancer stages, ages and races, there existed significant difference in the expression of SHMT2 among different groups by mining of the UALCAN database. High SHMT2 expression is associated with poor overall survival in patients with kidney cancer. Among all co-expressed genes, NDUFA4L2 and SHMT2 had a high co-expression efficient. SHMT2 overexpression led to the increased expression of NDUFA4L2 at both mRNA and protein levels. Like SHMT2, overexpressed NDUFA4L2 also was associated with worse overall survival in patients with kidney cancer. CONCLUSION: Based on above results, overexpressed SHMT2 and its co-expressed gene NDUFA4L2 were all correlated with the prognosis in kidney cancer. The present study might be benefit for better understanding the clinical significance of SHMT2 and provided a potential therapeutic target for kidney cancer in future.

Long non-coding RNA MIF-AS1 promotes gastric cancer cell proliferation and reduces apoptosis to upregulate NDUFA4.

Long non-coding RNA MIF-AS1 (lncMIF-AS1) has been found to be upregulated in the tumor tissues of gastric cancer; however, its importance for the progression of gastric cancer remains unknown. Thus, the present study was designed to determine the role of the lncMIF-AS1-based signal transduction pathway in mediating the proliferation and apoptosis of gastric cancer cells. Differentially expressed lncRNAs and mRNAs were screened out using microarray analysis, based on the published data (GSE63288), and validated using quantitative RT-PCR. Target relationships between lncRNA-micro RNA (miRNA) and miRNA-mRNA were predicted by bioinformatics analysis and verified by dual-luciferase reporter assay. Protein expression of NDUFA4, COX6C and COX5B was detected by western blot. Cell proliferation, cell cycle and apoptosis were determined using colony formation assay and flow cytometry analysis. Oxidative phosphorylation in gastric cancer cells was assessed by levels of oxygen consumption and ATP synthase activity. Expression of lncMIF-AS1 and NDUFA4 were upregulated in gastric cancer tissues and cells as compared with non-cancerous gastric tissues and cells (P < .05). MiR-212-5p was identified as the most important miRNA linker between lncMIF-AS1 and NDUFA4, which was negatively regulated by lncMIF-AS1 and its depletion is the main cause of NDUFA4 overexpression (P < .01). The upregulated expression of NDUFA4 then greatly promoted the proliferation and decreased the apoptosis of gastric cancer cells through activation of the oxidative phosphorylation pathway. Taken together, the present study implies that inhibition of lncMIF-AS1/miR-212-5p/NDUFA4 signal transduction may provide a promising therapeutic target for the treatment of gastric cancer.

LncRNA MAFG-AS1 promotes the progression of colorectal cancer by sponging miR-147b and activation of NDUFA4.

Researchers have shown that long noncoding RNAs (lncRNAs) are closely associated with the pathogenesis of colorectal cancer (CRC). In here, we aimed to explore the function of lncRNA MAFG-AS1 in tumorigenesis of CRC. Firstly, we found that the expression of MAFG-AS1 was upregulated in CRC tissues and positively correlated with the advanced tumor stage. A reciprocal repression was found between MAFG-AS1 and miR-147b. The expression of miR-147b was downregulated in CRC tissues and inversely correlated with MAFG-AS1. Both the low-expression of miR-147b expression and the advanced tumor stage were independent factor for poor survival probability. Furthermore, overexpression of MAFG-AS1 promoted cell proliferation, cell cycle progression, and invasion, and inhibited apoptosis, while transduction of miR-147b partially reversed the effect of MAFG-AS1 on cellular processes. Consistently, stable over-expression of MAFG-AS1 contributed to the growth of colon cancer cell xenografts in vivo. NDUFA4 was identified as a direct target of miR-147b and knockdown of NDUFA4 abolished the oncogenic role of miR-147b inhibitor. Besides, MAFG-AS1 contributed to cell glycolysis by sponging miR-147b and activation of NDUFA4, causing an upregulation of PDK1, PFK1 and PKM2. Taken together, our study suggested that MAFG-AS1 functions as a novel oncogenic lncRNA in the development of CRC by regulating miR-147b/NDUFA4.

Induction of the mitochondrial NDUFA4L2 protein by HIF-1a regulates heart regeneration by promoting the survival of cardiac stem cell.

The adult mammalian heart doesn't regenerate after cardiomyocyte injury, which was mainly caused by the severe and persistent effects of cardiomyopathy. Recently, some studies reported that the mammalian heart can regenerate under low oxygen environment. However, the mechanism that the mammalian heart can regenerate remains unknown. Here, we used cardiac stem cells (CSCs) to be planted in serum-free medium under hypoxia environment to understand the mechanism of HIF1α/NDUFA4L2 in the regulation of hypoxia-alleviated apoptosis. Our results revealed that hypoxia can alleviated CSCs apoptosis. Hypoxia inhibited the level of cleaved-caspase3 and stimulated the expression of stabilized HIF-1α. DMOG promotes the survival of CSCs and the protein expression of NDUFA4L2. 2-ME repressed the survival of CSCs and the protein expression of NDUFA4L2. CHIP assay showed that HIF-1α regulated the survival of CSCs by augmenting the combination of HIF-1α and NDUFA4L2's HRE. Knockdown of NDUFA4L2 reversed the role of hypoxia in the survival of CSCs. Taken together, hypoxia promotes the viability of CSCs in serum-free medium by HIF-1α/NDUFA4L2 signaling pathway.

NDUFA4L2 protects against ischaemia/reperfusion-induced cardiomyocyte apoptosis and mitochondrial dysfunction by inhibiting complex I.

Myocardial ischaemia/reperfusion (I/R) injury may cause the apoptosis of cardiomyocytes as well as mitochondrial dysfunction. The aims of the present study were to investigate whether NADH dehydrogenase 1 alpha subcomplex subunit 4-like 2 (NDUFA4L2) on myocardial ischaemia-reperfusion (I/R) injury and the underlying molecular mechanism. The hypoxia-reperfusion (H/R) model was established in vitro using H9c2 cells to simulate I/R injury. NDUFA4L2 and complex I expression levels were detected using RT-PCR and western blot. The apoptosis of H9c2 cells was evaluated by flow cytometry and the expression of Bax and Bcl-2 was detected by western blot. The mitochondrial function was assessed by ATP concentration, mPTP opening and cytochrome c (cyto C) expression. Our data indicated that NDUFA4L2 expression was significantly down-regulated in myocardial H/R injury. Overexpression of NDUFA4L2 led to a dramatic prevention of H/R-induced apoptosis accompanied by a decrease in the expression of Bax and an increase in the expression of Bcl-2. Meanwhile, augmentation of NDUFA4L2 dramatically prevented mitochondrial dysfunction caused by H/R as reflecting in the increased ATP concentration, delayed mPTP opening, as well as down-regulated cyto C expression. Moreover, complex I activation was heightened and negatively regulated by NDUFA4L2. Silencing complex I conspicuously attenuated cell apoptosis and mitochondrial dysfunction. Taken together, our findings demonstrated that NDUFA4L2 protects against H/R injury by preventing myocardium apoptosis and mitochondrial dysfunction via the complex I, and may be a potential therapeutic approach for attenuating myocardial I/R injury.

NDUFA4L2 expression predicts poor prognosis in clear cell renal cell carcinoma patients.

BACKGROUND: NDUFA4L2 is overexpressed in VHL-deficient cell lines and neuroblastoma. The clinical significance of NDUFA4L2 in clear cell renal cell carcinoma (ccRCC) has not been well studied. Therefore, we evaluated the prognostic value of NDUFA4L2 in ccRCC patients. METHODS: In our study, NDUFA4L2 expression in 86 cases of ccRCC and adjacent normal tissues was monitored by immunohistochemistry, semi-quantitative RT-PCR, and Western blot analyses. The relationship between NDUFA4L2 expression and the clinical features of ccRCC was assessed. RESULTS: The results showed that NDUFA4L2 protein expression was found to be higher in ccRCC tissues 81.4% (70/86) than in normal tissues 26.7% (23/86) (p = 0.021). The average level of NDUFA4L2 mRNA expression was found to be 122.23 ± 6.018 and 21.34 ± 1.036 in ccRCC tissue and adjacent normal tissue (p < 0.001). NDUFA4L2 expression levels were correlated with some clinical features of ccRCC. Multivariate analysis showed NDUFA4L2 expression was an independent prognostic factor for ccRCC patients. CONCLUSIONS: Our study has provided the significant clinical relevance of NDUFA4L2 in ccRCC and suggested that ccRCC patients with NDUFA4L2 overexpression may be suitable as a potential therapeutic target for ccRCC patients.

Integrative analysis identifies oxidative stress biomarkers in non-alcoholic fatty liver disease via machine learning and weighted gene co-expression network analysis.

Background: Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease globally, with the potential to progress to non-alcoholic steatohepatitis (NASH), cirrhosis, and even hepatocellular carcinoma. Given the absence of effective treatments to halt its progression, novel molecular approaches to the NAFLD diagnosis and treatment are of paramount importance. Methods: Firstly, we downloaded oxidative stress-related genes from the GeneCards database and retrieved NAFLD-related datasets from the GEO database. Using the Limma R package and WGCNA, we identified differentially expressed genes closely associated with NAFLD. In our study, we identified 31 intersection genes by analyzing the intersection among oxidative stress-related genes, NAFLD-related genes, and genes closely associated with NAFLD as identified through Weighted Gene Co-expression Network Analysis (WGCNA). In a study of 31 intersection genes between NAFLD and Oxidative Stress (OS), we identified three hub genes using three machine learning algorithms: Least Absolute Shrinkage and Selection Operator (LASSO) regression, Support Vector Machine - Recursive Feature Elimination (SVM-RFE), and RandomForest. Subsequently, a nomogram was utilized to predict the incidence of NAFLD. The CIBERSORT algorithm was employed for immune infiltration analysis, single sample Gene Set Enrichment Analysis (ssGSEA) for functional enrichment analysis, and Protein-Protein Interaction (PPI) networks to explore the relationships between the three hub genes and other intersecting genes of NAFLD and OS. The distribution of these three hub genes across six cell clusters was determined using single-cell RNA sequencing. Finally, utilizing relevant data from the Attie Lab Diabetes Database, and liver tissues from NASH mouse model, Western Blot (WB) and Reverse Transcription Quantitative Polymerase Chain Reaction (RT-qPCR) assays were conducted, this further validated the significant roles of CDKN1B and TFAM in NAFLD. Results: In the course of this research, we identified 31 genes with a strong association with oxidative stress in NAFLD. Subsequent machine learning analysis and external validation pinpointed two genes: CDKN1B and TFAM, as demonstrating the closest correlation to oxidative stress in NAFLD. Conclusion: This investigation found two hub genes that hold potential as novel targets for the diagnosis and treatment of NAFLD, thereby offering innovative perspectives for its clinical management.

Elevated of NDUFA4L2 expression in colon adenocarcinoma is correlated with an unfavorable prognosis and increased immune cell infiltration.

Background: Colon adenocarcinoma (COAD) is a prevalent malignancy worldwide, yet, its underlying pathogenesis and genetic characteristics are still unclear. Previous studies have suggested that NADH dehydrogenase 1 alpha subcomplex subunit 4-like 2 (NDUFA4L2) may affect tumor progression across various cancers. However, this effect on COAD has rarely been reported. Thus, this study investigated NDUFA4L2's prognostic and diagnostic relevance and explored its potential connection with immune cell infiltration in COAD. Methods: To achieve this, RNA sequencing data from Cancer Genome Atlas (TCGA) was analyzed to assess NDUFA4L2's prognostic value in COAD, and factors relevant to the prognosis of COAD, including NDUFA4L2, were scrutinized using Kaplan-Meier analyses as well as univariate and multivariate Cox regression. A nomogram model was created to project prognosis based on the results of multivariate Cox analysis. Furthermore, gene set enrichment analysis (GSEA) was employed to pinpoint key NDUFA4L2-related pathways, and single-sample GSEA (ssGSEA) on TCGA data was employed to investigate the connections of NDUFA4L2 with cancer immune infiltrations. Results: Our findings revealed significant associations of high NDUFA4L2 expression with poor overall survival, progression-free interval, and disease-specific survival of COAD patients. GSEA indicated close links of NDUFA4L2 with several signaling pathways implicated in tumorigenesis, including extracellular matrix receptor interaction, the intestinal immune network for immunoglobulin A production, natural killer (NK) cell-mediated cytotoxicity, pathways in cancer, cell adhesion molecules, mitogen-activated protein kinase signaling pathway, Hedgehog signaling pathway, transforming growth factor beta signaling pathway, and chemokine signaling pathway. Additionally, ssGSEA identified a positive link between increased NDUFA4L2 expression and higher infiltration degree of various immune cells, such as immature dendritic cells, macrophages, NK cells and dendritic cells. Conclusions: Collectively, our findings demonstrate the association of increased NDUFA4L2 expression with adverse prognosis and heightened immune cell infiltration in COAD patients.

Biallelic NDUFA4 Deletion Causes Mitochondrial Complex IV Deficiency in a Patient with Leigh Syndrome.

Oxidative phosphorylation involves a complex multi-enzymatic mitochondrial machinery critical for proper functioning of the cell, and defects herein cause a wide range of diseases called "primary mitochondrial disorders" (PMDs). Mutations in about 400 nuclear and 37 mitochondrial genes have been documented to cause PMDs, which have an estimated birth prevalence of 1:5000. Here, we describe a 4-year-old female presenting from early childhood with psychomotor delay and white matter signal changes affecting several brain regions, including the brainstem, in addition to lactic and phytanic acidosis, compatible with Leigh syndrome, a genetically heterogeneous subgroup of PMDs. Whole genome sequencing of the family trio identified a homozygous 12.9 Kb deletion, entirely overlapping the NDUFA4 gene. Sanger sequencing of the breakpoints revealed that the genomic rearrangement was likely triggered by Alu elements flanking the gene. NDUFA4 encodes for a subunit of the respiratory chain Complex IV, whose activity was significantly reduced in the patient's fibroblasts. In one family, dysfunction of NDUFA4 was previously documented as causing mitochondrial Complex IV deficiency nuclear type 21 (MC4DN21, OMIM 619065), a relatively mild form of Leigh syndrome. Our finding confirms the loss of NDUFA4 function as an ultra-rare cause of Complex IV defect, clinically presenting as Leigh syndrome.

Ndufa4 Regulates the Proliferation and Apoptosis of Neurons via miR-145a-5p/Homer1/Ccnd2.

The Dandy-Walker malformation (DWM) is characterized by neuron dysregulation in embryonic development; however, the regulatory mechanisms associated with it are unclear. This study aimed to investigate the role of NADH dehydrogenase 1 alpha subcomplex 4 (NDUFA4) in regulating downstream signaling cascades and neuronal proliferation and apoptosis. Ndufa4 overexpression promoted the proliferation of neurons and inhibited their apoptosis in vitro, which underwent reverse regulation by the Ndufa4 short hairpin RNAs. Ndufa4-knockout (KO) mice showed abnormal histological alterations in the brain tissue, in addition to impaired spatial learning capacity and exploratory activity. Ndufa4 depletion altered the microRNA expressional profiles of the cerebellum: Ndufa4 inhibited miR-145a-5p expression both in the cerebellum and neurons. miR-145a-5p inhibited the proliferation of neurons and promoted their apoptosis. Ndufa4 promoted and miR-145a-5p inhibited the expression of human homer protein homolog 1 and cyclin D2 in neurons. Thus, Ndufa4 promotes the proliferation of neurons and inhibits their apoptosis by inhibiting miR-145a-5p, which directly targets and inhibits the untranslated regions of Homer1 and Ccnd2 expression.

REEP1 Preserves Motor Function in SOD1G93A Mice by Improving Mitochondrial Function via Interaction with NDUFA4.

A decline in the activities of oxidative phosphorylation (OXPHOS) complexes has been consistently reported in amyotrophic lateral sclerosis (ALS) patients and animal models of ALS, although the underlying molecular mechanisms are still elusive. Here, we report that receptor expression enhancing protein 1 (REEP1) acts as an important regulator of complex IV assembly, which is pivotal to preserving motor neurons in SOD1G93A mice. We found the expression of REEP1 was greatly reduced in transgenic SOD1G93A mice with ALS. Moreover, forced expression of REEP1 in the spinal cord extended the lifespan, decelerated symptom progression, and improved the motor performance of SOD1G93A mice. The neuromuscular synaptic loss, gliosis, and even motor neuron loss in SOD1G93A mice were alleviated by increased REEP1 through augmentation of mitochondrial function. Mechanistically, REEP1 associates with NDUFA4, and plays an important role in preserving the integrity of mitochondrial complex IV. Our findings offer insights into the pathogenic mechanism of REEP1 deficiency in neurodegenerative diseases and suggest a new therapeutic target for ALS.