MTFP1 controls mitochondrial fusion to regulate inner membrane quality control and maintain mtDNA levels.

Mitochondrial dynamics play a critical role in cell fate decisions and in controlling mtDNA levels and distribution. However, the molecular mechanisms linking mitochondrial membrane remodeling and quality control to mtDNA copy number (CN) regulation remain elusive. Here, we demonstrate that the inner mitochondrial membrane (IMM) protein mitochondrial fission process 1 (MTFP1) negatively regulates IMM fusion. Moreover, manipulation of mitochondrial fusion through the regulation of MTFP1 levels results in mtDNA CN modulation. Mechanistically, we found that MTFP1 inhibits mitochondrial fusion to isolate and exclude damaged IMM subdomains from the rest of the network. Subsequently, peripheral fission ensures their segregation into small MTFP1-enriched mitochondria (SMEM) that are targeted for degradation in an autophagic-dependent manner. Remarkably, MTFP1-dependent IMM quality control is essential for basal nucleoid recycling and therefore to maintain adequate mtDNA levels within the cell.

HIF1A-dependent overexpression of MTFP1 promotes lung squamous cell carcinoma development by activating the glycolysis pathway.

Introduction: Mitochondrial fission process 1 (MTFP1) is an inner mitochondrial membrane (IMM) protein implicated in the development and progression of various tumors, particularly lung squamous cell carcinoma (LUSC). This study aims to provide a more theoretical basis for the treatment of LUSC. Methods: Through bioinformatics analysis, MTFP1 was identified as a novel target gene of HIF1A. MTFP1 expression in LUSC was examined using The Cancer Genome Atlas (TCGA), Gene Expression Omnibus (GEO), and Proteomics Data Commons (PDC) databases. The Kaplan-Meier plotter (KM plotter) database was utilized to evaluate its correlation with patient survival. Western blot and chromatin immunoprecipitation (ChIP) assays were employed to confirm the regulatory relationship between MTFP1 and HIF1A. Additionally, cell proliferation, colony formation, and migration assays were conducted to investigate the mechanism by which MTFP1 enhances LUSC cell proliferation and metastasis. Results: Our findings revealed that MTFP1 overexpression correlated with poor prognosis in LUSC patients(P < 0.05). Moreover, MTFP1 was closely associated with hypoxia and glycolysis in LUSC (R = 0.203; P < 0.001, R = 0.391; P < 0.001). HIF1A was identified as a positive regulator of MTFP1. Functional enrichment analysis demonstrated that MTFP1 played a role in controlling LUSC cell proliferation. Cell proliferation, colony formation, and migration assays indicated that MTFP1 promoted LUSC cell proliferation and metastasis by activating the glycolytic pathway (P < 0.05). Conclusions: This study establishes MTFP1 as a novel HIF1A target gene that promotes LUSC growth by activating the glycolytic pathway. Investigating MTFP1 may contribute to the development of effective therapies for LUSC patients, particularly those lacking targeted oncogene therapies.

MiR-125b-5p Targets MTFP1 to Inhibit Cell Proliferation, Migration, and Invasion and Facilitate Cell Apoptosis in Endometrial Carcinoma.

MicroRNAs (miRNAs) are recognized as latent diagnostic, prognostic, and therapeutic biomarkers for endometrial carcinoma (EC). We attempted to discuss function and mechanism of miR-125b-5p in EC cell progression. This study manifested a decreased miR-125b-5p level and an increased mitochondrial fission process 1 (MTFP1) level in EC, and there was an inverse correlation between them. Moreover, in vitro assays were performed. The results denoted that miR-125b-5p could target a putative binding site on MTFP1 3'UTR to reduce MTFP1 expression, thereby repressing cell malignant behaviors. Besides, the promoting impact of MTFP1 overexpression on malignant phenotypes of EC cells could be restored by miR-125b-5p up-regulation. Considering, our investigation exhibited that miR-125b-5p curbed EC cell malignant phenotypes through targeting MTFP1. This study generates a fresh functional mechanism for EC occurrence and progression, which also lays the groundwork for clinical therapies.

Reduced mitochondrial size in hippocampus and psychiatric behavioral changes in the mutant mice with homologous mutation of Timm8a1-I23fs49X.

Background: Deafness-dystonia-optic neuronopathy (DDON) syndrome, a condition that predominantly affects males, is caused by mutations in translocase of mitochondrial inner membrane 8A (TIMM8A)/deafness dystonia protein 1 (DDP1) gene and characterized by progressive deafness coupled with other neurological abnormalities. In a previous study, we demonstrated the phenotype of male mice carrying the hemizygous mutation of Timm8a1-I23fs49X. In a follow-up to that study, this study aimed to observe the behavioral changes in the female mutant (MUT) mice with homologous mutation of Timm8a1 and to elucidate the underlying mechanism for the behavioral changes. Materials and methods: Histological analysis, transmission electron microscopy (EM), Western blotting, hearing measurement by auditory brainstem response (ABR), and behavioral observation were compared between the MUT mice and wild-type (WT) littermates. Results: The weight of the female MUT mice was less than that of the WT mice. Among MUT mice, both male and female mice showed hearing impairment, anxiety-like behavior by the elevated plus maze test, and cognitive deficit by the Morris water maze test. Furthermore, the female MUT mice exhibited coordination problems in the balance beam test. Although the general neuronal loss was not found in the hippocampus of the MUT genotype, EM assessment indicated that the mitochondrial size showing as aspect ratio and form factor in the hippocampus of the MUT strain was significantly reduced compared to that in the WT genotype. More importantly, this phenomenon was correlated with the upregulation of translation of mitochondrial fission process protein 1(Mtfp1)/mitochondrial 18 kDa protein (Mtp18), a key fission factor that is a positive regulator of mitochondrial fission and mitochondrial size. Interestingly, significant reductions in the size of the uterus and ovaries were noted in the female MUT mice, which contributed to significantly lower fertility in the MUT mice. Conclusion: Together, a homologous mutation in the Timm8a1 gene caused the hearing impairment and psychiatric behavioral changes in the MUT mice; the latter phenotype might be related to a reduction in mitochondrial size regulated by MTP18.

Long non-coding RNA MIR4435-2HG/microRNA-125a-5p axis is involved in myocardial ischemic injuries.

This study aimed to investigate whether and how long non-coding RNA (lncRNA) MIR4435-2 host gene (MIR4435-2HG) involved in acute myocardial ischemia/reperfusion (I/R). Blood samples were collected from acute myocardial infarction (AMI) patients to detect MIR4435-2HG expression. In vivo myocardial I/R mice model and in vitro H2O2-induced oxidative stress model were established. Echocardiography, TUNEL assay and lactate dehydrogenase (LDH) detection were performed to assess heart infarction and myocardium apoptosis. Relationship among microRNA-125a-5p (miR-125a-5p), MIR4435-2HG and Mitochondrial fission protein 1 (MTFP1) was predicted by Targetscan and verified by luciferase reporter assay. MIR4435-2HG was notably upregulated in AMI patients, myocardial I/R mice and H2O2-treated cells. Knockdown of MIR4435-2HG notably alleviated infraction volume, ejection fraction (EF) and fractional shortening (FS) levels, cell apoptosis portion and pro-apoptotic cleaved-caspase-3 and Cyt c expression caused by myocardial I/R and oxidative stress, as well as improved cardiomyocytes viability. Transfection with miR-125a-5p alleviated MIR4435-2HG-caused cardiomyocytes apoptosis during oxidative stress. MiR-125a-5p overexpression decreased luciferase activity of the wild-type MIR4435-2HG compared with the mutated MIR4435-2HG. The expression levels of MTFP1 were elevated in myocardium from MI mice model and H2O2-treated AC16 cardiomyocytes. In addition, miR-125a-5p overexpression inhibited MTFP1 expression, and could stimulate the wild-type MTFP1 promoter luciferase activity but not the mutated one. Our findings revealed the role of MIR4435-2HG in MI-induced myocardium injury and cardiomyocytes apoptosis, disclosed a novel MIR4435-2HG/miR-125a-5p regulatory axis during myocardial I/R, and thus identified a potential target for the therapy of myocardial IR injury.

Gene expression based profiling of pleomorphic xanthoastrocytoma highlights two prognostic subgroups.

BACKGROUND: Pleomorphic xanthoastrocytomas (PXAs) are rare, accounting for less than 1% of astrocytomas, and commonly occur in young patients. The majority are WHO grade II. A fraction of tumors that present or recur with malignant change are classified as anaplastic (APXA, grade III). Limited data are available on their molecular characteristics. METHODOLOGY: Genome-wide expression profiling of 14 PXA and 6 APXAs was performed by microarray. Among differentially expressed genes (DEGs), Cyclin-Dependent Kinase 14 (CDK14) and Mitochondrial Fission Process 1 (MTFP1) were validated by qRT PCR. RESULT: Unsupervised hierarchical clustering revealed two distinct molecular clusters (Cluster 1: 10 PXA, 3 APXA and Cluster 2: 4 PXA, 3 APXA) with grade II and III tumors distributed in both highlighting molecular heterogeneity within the same grade. There was an insignificant difference in age, sex, immunohistochemical profile, frequency of BRAF mutation, or CDKN2A deletion among the two clusters. Significantly, worse progression-free survival was observed in cluster 2 (P=0.003). mRNA profiling-based prediction of recurrence was superior to and independent of histological grade, BRAF mutation, or CDKN2A deletion status. A total of 10 upregulated and 418 downregulated genes were identified between the PXA clusters. qRT-PCR validation of CDK14 (upregulated in cluster 2) and MTFP1 (upregulated in cluster 1) showed strong concordance with expression array data. CONCLUSION: This is the first comprehensive study highlighting distinct molecular subgroups of PXA. The differentially expressed genes between two clusters may potentially be used for developing histology independent classification schemes, prognostication and may serve as prospective therapeutic targets for PXA patients.

Transcriptome Profiling of Developing Ovine Fat Tail Tissue Reveals an Important Role for MTFP1 in Regulation of Adipogenesis.

Fat-tail sheep exhibit a unique trait whereby substantial adipose tissue accumulates in the tail, a phenotype that is advantageous in many agroecological environments. In this study, we conducted histological assays, transcriptome analysis and functional assays to examine morphogenesis, characterize gene expression, and elucidate mechanisms that regulate fat tail development. We obtained the microstructure of tail before and after fat deposition, and demonstrated that measurable fat deposition occurred by the 80-day embryo (E80) stage, earlier than other tissues. Transcriptome profiling revealed 1,058 differentially expressed genes (DEGs) with six markedly different expression trends. GSEA enrichment and other downstream analyses showed important roles for genes and pathways involving in metabolism and that mitochondrial components were specifically overexpressed in the fat tail tissue of the 70-day embryo (E70). One hundred and eighty-three genes were further identified by leading edge gene analysis, among which, 17 genes have been reported in previous studies, including EEF1D, MTFP1, PPP1CA, PDGFD. Notably, the MTFP1 gene was highly correlated with the expression of other genes and with the highest enrichment score and gene expression change. Knockdown of MTFP1 in isolated adipose derived stem cells (ADSCs) inhibited cell proliferation and migration ability, besides, promoted the process of adipogenesis in vitro.

MTFP1 overexpression promotes the growth of oral squamous cell carcinoma by inducing ROS production.

Mitochondrial fission process 1 (MTFP1) is a novel nuclear-encoded protein that promotes mitochondrial fission. Increasing lines of evidence indicate that increased mitochondrial fission is involved in carcinogenesis and tumor progression. However, the expression and biological effects of MTFP1 in cancer development is still unclear, especially in oral squamous cell carcinoma (OSCC). In this study, we first evaluated the expression of MTFP1 in 12-paired OSCC tumor and peritumor tissues. We then explored the effects of MTFP1 knockdown or overexpression on cell growth by cell proliferation, colony formation, cell cycle, and cell apoptosis assays. Furthermore, the mechanisms by which MTFP1 promoted OSCC cell growth were explored. Our results showed that MTFP1 is frequently overexpressed in OSCC tissues. Functional experiments revealed that MTFP1 promoted the growth of OSCC cells by inducing the progression of cell cycle and suppressing cell apoptosis. Mechanistically, MTFP1 overexpression-mediated mitochondrial fragmentation and subsequent ROS production was found to be involved in the promotion of OSCC cell growth. Collectively, our study demonstrates that MTFP1 plays a critical oncogenic role in OSCC carcinogenesis, which may serve as a potential therapeutic target in the treatment of this malignance.

DARPins recognizing mTFP1 as novel reagents for in vitro and in vivo protein manipulations.

Over the last few years, protein-based affinity reagents have proven very helpful in cell and developmental biology. While many of these versatile small proteins can be expressed both in the intracellular and extracellular milieu in cultured cells and in living organisms, they can also be functionalized by fusing them to different protein domains in order to regulate or modulate their target proteins in diverse manners. For example, protein binders have been employed to degrade, trap, localize or enzymatically modify specific target proteins. Whereas binders to many endogenous proteins or small protein tags have been generated, several affinity reagents against fluorescent proteins have also been created and used to manipulate target proteins tagged with the corresponding fluorescent protein. Both of these approaches have resulted in improved methods for cell biological and developmental studies. While binders against GFP and mCherry have been previously isolated and validated, we now report the generation and utilization of designed ankyrin repeat proteins (DARPins) against the monomeric teal fluorescent protein 1 (mTFP1). Here we use the generated DARPins to delocalize Rab proteins to the nuclear compartment, in which they cannot fulfil their regular functions anymore. In the future, such manipulations might enable the production of acute loss-of-function phenotypes in different cell types or in living organisms based on direct protein manipulation rather than on genetic loss-of-function analyses.

Knockdown of Mtfp1 can minimize doxorubicin cardiotoxicity by inhibiting Dnm1l-mediated mitochondrial fission.

The long-term usage of doxorubicin (DOX) is largely limited due to the development of severe cardiomyopathy. Many studies indicate that DOX-induced cardiac injury is related to reactive oxygen species generation and ultimate activation of apoptosis. The role of novel mitochondrial fission protein 1 (Mtfp1) in DOX-induced cardiotoxicity remains elusive. Here, we report the pro-mitochondrial fission and pro-apoptotic roles of Mtfp1 in DOX-induced cardiotoxicity. DOX up-regulates the Mtfp1 expression in HL-1 cardiac myocytes. Knockdown of Mtfp1 prevents cardiac myocyte from undergoing mitochondrial fission, and subsequently reduces the DOX-induced apoptosis by preventing dynamin 1-like (Dnm1l) accumulation in mitochondria. In contrast, when Mtfp1 is overexpressed, a suboptimal dose of DOX can induce a significant percentage of cells to undergo mitochondrial fission and apoptosis. These data suggest that knocking down of Mtfp1 can minimize the cardiomyocytes loss in DOX-induced cardiotoxicity. Thus, the regulation of Mtfp1 expression could be a novel therapeutic approach in chemotherapy-induced cardiotoxicity.