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PubMed2026

TFAM organizes DNA into compact higher order structures.

TFAM (Transcription Factor A, Mitochondrial) is an essential human protein that plays two key roles in mitochondrial DNA (mtDNA) homeostasis. TFAM acts as a transcription factor that specifically binds to promoter regions, but it is also solely responsible for organizing mtDNA into nucleoids by nonspecifically covering the entire genome. Many studies have addressed TFAM in transcription regulation, but its role as a genome organizing entity is not well characterized. The current understanding of how TFAM compacts DNA into nucleoids is based on crystal structures of a TFAM monomer bound to short fragments of DNA (22-28 bp). However, this does not adequately reflect the biological role of TFAM in organizing the nucleoid where multiple TFAM molecules oligomerize on the 16.5 kb genome to form the nucleoid. Here, we present a biochemical and structural analysis of TFAM oligomerization on longer DNA. Our results show that TFAM compacts longer segments of DNA into higher order complexes that are homogenous yet exhibit continuous conformational dynamics.

Major classification: Biological sciences↗

PubMed2026

Mitochondrial Haplotype Shapes the Trajectory of Ovarian Aging in Genetically Heterogeneous Rats.

Ovarian aging leads to permanent reproductive senescence and systemic hormonal changes that predispose women to age-associated comorbidities. Despite these observations, the intrinsic mechanisms driving age-related ovarian decline are poorly defined. Mitochondrial DNA (mtDNA) mutations and instability are strongly associated with aging; however, it remains unknown if naturally occurring mitochondrial genetic variation influences the trajectory of ovarian aging. To address this, we compared two genetically heterogeneous rat cohorts (OKC-HETB and OKC-HETW) that differ in mitochondrial haplotype on a randomized but equivalently distributed nuclear background. The OKC-HETW haplotype was associated with accelerated loss of primordial follicles and pathological remodeling marked by fibrosis, macrophage infiltration, and multinucleated giant cells. These tissue-level pathologies were paralleled by mitochondrial dysfunction, characterized by decreased respiratory complex activity, ATP production, and mtDNA copy number. Mechanistically, we identified a haplotype-specific defect in mitochondrial genome maintenance. Although TFAM expression was normal, and total TFAM protein was elevated, OKC-HETW ovaries showed reduced mitochondrial TFAM abundance, TFAM-mtDNA binding, and TOMM20, suggesting that impaired TOMM20-mediated import is associated with compromised mitochondrial genomic stability. Longitudinal transcriptomic and proteomic analyses further indicate that mitochondrial haplotype influences the rate of ovarian aging, with OKC-HETW ovaries showing accelerated activation of inflammatory and fibrotic pathways alongside suppressed proteostasis and mitochondrial function. These defects corresponded to impairments in ovulation and a trend toward worsening oocyte quality. Collectively, our findings identify mitochondrial haplotype as a heritable modifier of ovarian aging rate that acts in concert with the nuclear genome, and a putative target for preserving ovarian function and female healthspan.

Animals↗

PubMed2026

Overlapping genetic etiology of pediatric and adult germ cell tumors.

BACKGROUND: Germ cell tumors are heterogeneous neoplasms arising from primordial germ cells. Although genome-wide association studies have identified numerous susceptibility loci for adult testicular germ cell tumors, the heritable basis of pediatric testicular germ cell tumors and germ cell tumors that arise outside the testes remain poorly understood. METHODS: We conducted a multi-ancestry genome-wide association study of pediatric germ cell tumors, including 1927 cases from the Germ Cell Tumor Epidemiology Study and 10 601 controls. Cases were diagnosed with testicular (n = 678), ovarian (n = 441), intracranial (n = 435), and extragonadal (n = 373) germ cell tumor between the ages of 0 and 19 years. RESULTS: We identified 4 loci reaching genome-wide significance, including variants near BAK1 (chr 6: rs3831846), SPRY4 (chr 5: rs12515244), DMRT1 (chromosome [chr] 9: rs10815910), and DEPTOR (chr 8: rs13277786). Additional genome-wide statistically significant associations were identified in subgroup analyses, including 6 loci for intracranial germ cell tumors (rs2758612 [PMF1/BGLAP], rs9854760 [PLCL2], rs6851498 [KIT], rs11816992 on chromosome 10, rs3830273 [TFAM], and rs13054014 [LZTR1]), 1 locus for testicular germ cell tumor (rs1907702 [KITLG]), and 1 locus for males (rs4610628 [MAD1L1]). After Bonferroni correction, 18 of 78 previously reported testicular germ cell tumor loci were significantly associated with germ cell tumor overall or in at least 1 subgroup with a particularly strong correlation between testicular germ cell tumor and intracranial germ cell tumor effect estimates (rho = 0.63, P = 5.5 × 10-10). Expression quantitative trait locus (QTL) analyses identified candidate genes in the regions identified on chromosome 6 (BAK1, LINC003366, and ITPR3) and chromosome 8 (DEPTOR and RP11-760H22.2). CONCLUSIONS: Our data support a role for germline genetic variation in the development of germ cell tumors in locations outside the testes and highlight shared genetic architecture across age group and tumor location.

Humans↗

PubMed2026

Overexpression of TCF7L2 promotes the viability and migration of MHCC-97H human hepatocellular carcinoma cells by upregulating MT-ND4L.

BACKGROUND: Hepatocellular carcinoma (HCC) is a highly aggressive cancer with high metabolic adaptability. TCF7L2, a transcription factor implicated in type 2 diabetes and cancer, is overexpressed in HCC. However, its specific role in HCC metabolic reprogramming is not well defined. We aimed to elucidate the previously unrecognized molecular mechanisms through which TCF7L2 impacts HCC progression. METHODS: To investigate the function of TCF7L2, a stable MHCC-97H cell line with TCF7L2 overexpression was established via lentiviral transduction. Cell viability and migration were assessed by Cell Counting Kit-8 (CCK-8) and Transwell assays. Transcriptomic profiling [RNA sequencing (RNA-seq)] was performed to identify differentially expressed genes (DEGs). Functional enrichment analysis [Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), Gene Set Enrichment Analysis (GSEA)] and bioinformatics promoter analysis (the JASPAR CORE database) were conducted. Clinical correlations, survival analysis, and tumor microenvironment (TME) interrogation were performed using The Cancer Genome Atlas Liver Hepatocellular Carcinoma (TCGA-LIHC) cohort and single-cell datasets [Human Protein Atlas (HPA), CellChat]. Drug sensitivity was predicted via the Genomics of Drug Sensitivity in Cancer (GDSC) database. RESULTS: TCF7L2 overexpression significantly promoted HCC cell proliferation and migration. Transcriptomic analysis revealed that TCF7L2 drives a profound metabolic shift, with key enrichments in lipid homeostasis, fatty acid β-oxidation, and the PI3K/Akt pathway. Mechanistically, TCF7L2 directly binds to the promoter of CPT1A, the rate-limiting enzyme of fatty acid oxidation, and indirectly upregulates the mitochondrial gene MT-ND4Lvia a strong positive correlation with the mitochondrial transcription factor TFAM. In clinical cohorts, TCF7L2 was overexpressed in HCC and its expression correlated positively with MT-ND4L, MKI67, and SNAI1, and served as a predictor of poor overall survival (OS). Furthermore, TCF7L2-high tumors were enriched in hepatic progenitor cell (HPC)-like niches, mediated by enhanced ANGPTL4 signaling. High TCF7L2 expression predicted increased sensitivity to PI3K/mTOR pathway inhibitors. CONCLUSIONS: TCF7L2 acts as a master metabolic regulator in HCC, coordinating lipid catabolism and mitochondrial biogenesis to drive aggressive tumor behavior. It further remodels the TME towards an HPC-like state and predicts sensitivity to metabolic-targeted therapies. These findings identify TCF7L2 as a key prognostic biomarker and a promising therapeutic target.

MHCC-97H hepatocellular carcinoma cells (MHCC-97H ↗

PubMed2026

EPS8 Differentially Regulates Antioxidant Defense and Mitochondrial Homeostatic Signaling in LNCaP and Enzalutamide-resistant LNCaP Cells.

BACKGROUND/AIM: Epidermal growth factor receptor pathway substrate 8 (EPS8) is an adaptor protein implicated in tumor progression and therapeutic resistance; however, its role in mitochondrial homeostatic signaling and antioxidant regulation remains unclear. This study examined the effects of EPS8 modulation in lymph node carcinoma of the prostate (LNCaP) and enzalutamide-resistant LNCaP (LNCaP-Enz) cells. MATERIALS AND METHODS: LNCaP-Enz cells were generated by long-term exposure to enzalutamide and maintained in 5 μM enzalutamide. EPS8 expression was modulated by plasmid-mediated overexpression or shRNA-mediated knockdown. Superoxide dismutase (SOD) activity and cellular adenosine triphosphate (ATP) levels were measured using colorimetric assays. Mitochondrial membrane potential (ΔΨm) was evaluated using JC-1 fluorescence, and mitochondrial staining patterns were qualitatively examined using MitoTracker Green staining. Protein expression associated with antioxidant defense, mitochondrial dynamics, mitochondrial stress response, mitochondrial biogenesis, and AMP-activated protein kinase (AMPK)-mammalian target of rapamycin (mTOR) signaling was analyzed by western blotting. RESULTS: EPS8 overexpression increased SOD activity and the expression of SOD1 and SOD2, whereas EPS8 knockdown reduced these antioxidant parameters. Conversely, EPS8 silencing increased cellular ATP levels and enhanced JC-1 red fluorescence patterns. EPS8 silencing increased MFN1 and OPA1 expression and reduced DRP1 expression, consistent with a fusion-associated mitochondrial profile. EPS8 silencing also increased SIRT1, PGC-1α, NRF1, TFAM, p-AMPK/AMPK, and p-mTOR/mTOR, but reduced HSP60, LONP1, ATF5, and CEBPβ expression. CONCLUSION: EPS8 differentially regulates SOD-associated antioxidant capacity and mitochondrial homeostatic signaling in LNCaP-based cell models. Further studies are required to determine whether EPS8 modulation affects enzalutamide responsiveness.

Humans↗