SPATA33 is an autophagy mediator for cargo selectivity in germline mitophagy

Fortilin binds CTNNA3 and protects it against phosphorylation, ubiquitination, and proteasomal degradation to guard cells against apoptosis

Fortilin, a 172-amino acid polypeptide, is a multifunctional protein that interacts with various protein molecules to regulate their functions. Although fortilin has been shown to interact with cytoskeleton proteins such as tubulin and actin, its interactions with the components of adherens junctions remained unknown. Using co-immunoprecipitation western blot analyses, the proximity ligation assay, microscale thermophoresis, and biolayer interferometry, we here show that fortilin specifically interacts with CTNNA3 (α-T-catenin), but not with CTNNA1, CTNNA2, or CTNNB. The silencing of fortilin using small interfering RNA (siRNAfortilin) promotes the proteasome-mediated degradation of CTNNA3 in 293T cells. Using both fortilin-deficient THP1 cells and 293T cells that overexpress wild-type (WT), phospho-null (5A), and phospho-mimetic (5D) CTNNA3s, we also show that the absence of fortilin accelerates the phosphorylation of CTNNA3, leading to its ubiquitination and proteasome-mediated degradation. Further, the silencing of CTNNA3 using siRNACTNNA3 causes 293T cells to undergo apoptosis. These data suggest that fortilin guards the cells against apoptosis by positively regulating the pro-survival molecule CTNNA3 by protecting it against phosphorylation, ubiquitination, and proteasome-mediated degradation.

ZDHHC7-mediated S-palmitoylation of ATG16L1 facilitates LC3 lipidation and autophagosome formation

Macroautophagy/autophagy is a fundamental cellular catabolic process that delivers cytoplasmic components into double-membrane vesicles called autophagosomes, which then fuse with lysosomes and their contents are degraded. Autophagy recycles cytoplasmic components, including misfolded proteins, dysfunctional organelles and even microbial invaders, thereby playing an essential role in development, immunity and cell death. Autophagosome formation is the main step in autophagy, which is governed by a set of ATG (autophagy related) proteins. ATG16L1 interacts with ATG12-ATG5 conjugate to form an ATG12-ATG5-ATG16L1 complex. The complex acts as a ubiquitin-like E3 ligase that catalyzes the lipidation of MAP1LC3/LC3 (microtubule associated protein 1 light chain 3), which is crucial for autophagosome formation. In the present study, we found that ATG16L1 was subject to S-palmitoylation on cysteine 153, which was catalyzed by ZDHHC7 (zinc finger DHHC-type palmitoyltransferase 7). We observed that re-expressing ATG16L1 but not the S-palmitoylation-deficient mutant ATG16L1C153S rescued a defect in the lipidation of LC3 and the formation of autophagosomes in ATG16L1-KO (knockout) HeLa cells. Furthermore, increasing ATG16L1 S-palmitoylation by ZDHHC7 expression promoted the production of LC3-II, whereas reducing ATG16L1 S-palmitoylation by ZDHHC7 deletion inhibited the LC3 lipidation process and autophagosome formation. Mechanistically, the addition of a hydrophobic 16-carbon palmitoyl group on Cys153 residue of ATG16L1 enhances the formation of ATG16L1-WIPI2B complex and ATG16L1-RAB33B complex on phagophore, thereby facilitating the LC3 lipidation process and autophagosome formation. In conclusion, S-palmitoylation of ATG16L1 is essential for the lipidation process of LC3 and the formation of autophagosomes. Our research uncovers a new regulatory mechanism of ATG16L1 function in autophagy.Abbreviation: ABE: acyl-biotin exchange; ATG: autophagy related; Baf-A1: bafilomycin A1; 2-BP: 2-bromopalmitate; CCD: coiled-coil domain; co-IP: co-immunoprecipitation; CQ: chloroquine; EBSS: Earle's balanced salt solution; HAM: hydroxylamine; KO: knockout; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; NP-40: Nonidet P-40; PBS: phosphate-buffered saline; PE: phosphatidylethanolamine; PtdIns3K-C1: class III phosphatidylinositol 3-kinase complex I; PTM: post-translational modification; RAB33B: RAB33B, member RAS oncogene family; RB1CC1/FIP200: RB1 inducible coiled-coil 1; SDS: sodium dodecyl sulfate; SQSTM1/p62: sequestosome 1; TEM: transmission electron microscope; WD: tryptophan and aspartic acid; WIPI2B: WD repeat domain, phosphoinositide interacting 2B; WT: wild-type; ZDHHC: zinc finger DHHC-type palmitoyltransferase.

RAB37-mediated autophagy guards ovarian homeostasis and function

Loss of ovarian homeostasis is associated with ovary dysfunction and female diseases; however, the underlying mechanisms responsible for the establishment of homeostasis and its function in the ovary have not been fully elucidated. Here, we showed that conditional knockout of Rab37 in oocytes impaired macroautophagy/autophagy proficiency in the ovary and interfered with follicular homeostasis and ovary development in mice. Flunarizine treatment upregulated autophagy, thus rescuing the impairment of follicular homeostasis and ovarian dysfunction in rab37 knockout mice by reprogramming of homeostasis. Notably, both the E2F1 and EGR2 transcription factors synergistically activated Rab37 transcription and promoted autophagy. Thus, RAB37-mediated autophagy ensures ovary function by maintaining ovarian homeostasis.Abbreviations: AMH: anti-Mullerian hormone; ATG: autophagy related; BECN1: beclin 1; cKO: conditional knockout; Cre: cyclization recombination enzyme; dpp: days postpartum; E2: estradiol; E2F1: E2F transcription factor 1; EBF1: EBF transcription factor 1; EGR2: early growth response 2; FSH: follicle stimulating hormone; LH: luteinizing hormone; mpp: months postpartum; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; RAB37: RAB37, member RAS oncogene family; SQSTM1: sequestosome 1; TFEB: transcription factor EB; Zp3: zona pellucida glycoprotein 3.

Divergent transcriptomic profiles in depressed individuals with hyper- and hypophagia implicating inflammatory status

BACKGROUND

Major Depressive Disorder (MDD) is a heterogenous and etiologically complex disease often presenting with divergent appetitive phenotypes including Hyperphagic MDD (characterized by an increased appetite) and Hypophagic MDD (characterized by a decrease in appetite) which are closely related to comorbidities, including cardiometabolic disorders. Hyperphagia is associated with atypical depression, decreased stress-hormone signaling, a pro-inflammatory status, hypersomnia, and poorer clinical outcomes. Yet, our understanding of associated biological correlates of Hyperphagic and Hypophagic MDD remain fragmented.

METHODS

We performed an exploratory study on peripheral blood RNA profiling using bulk RNAseq in unmedicated individuals with Hyperphagic and Hypophagic MDD (n = 7 and n = 13, respectively).

RESULTS

At baseline, we discovered an increased expression of TADA2B in hyperphagic MDD with the significant enrichment of 72 gene ontology pathways mainly related to inflammation. In addition, we used the Maastricht Acute Stress Task to uncover stress-related transcriptomic profiles in Hyper- and Hypophagic MDD and discovered the upregulation of CCDC196 and the downregulation of SPATA33 in hyperphagic MDD. Gene ontology enrichment analysis after stress exposure showed pathways related to ribosomal activity.

LIMITATIONS

The present findings are tempered primarily by the limited sample size, which requires independent replication of this exploratory study. However, stringent methods controlling for false positive findings mitigate the risk associated with sample size limitations.

DISCUSSION

Limitations notwithstanding, findings suggest that hyper- and hypophagic MDD is associated with divergent RNA expression profiles in peripheral blood that are amplified by exposure to a controlled stress test. Our findings in a well-controlled study provide evidence for peripheral markers of a relevant endophenotype of MDD.

Mitophagy and spermatogenesis: Role and mechanisms

The mitophagy process, a type of macroautophagy, is the targeted removal of mitochondria. It is a type of autophagy exclusive to mitochondria, as the process removes defective mitochondria one by one. Mitophagy serves as an additional level of quality control by using autophagy to remove superfluous mitochondria or mitochondria that are irreparably damaged. During spermatogenesis, mitophagy can influence cell homeostasis and participates in a variety of membrane trafficking activities. Crucially, it has been demonstrated that defective mitophagy can impede spermatogenesis. Despite an increasing amount of evidence suggesting that mitophagy and mitochondrial dynamics preserve the fundamental level of cellular homeostasis, little is known about their role in developmentally controlled metabolic transitions and differentiation. It has been observed that male infertility is a result of mitophagy's impact on sperm motility. Furthermore, certain proteins related to autophagy have been shown to be present in mammalian spermatozoa. The mitochondria are the only organelle in sperm that can produce reactive oxygen species and finally provide energy for sperm movement. Furthermore, studies have shown that inhibited autophagy-infected spermatozoa had reduced motility and increased amounts of phosphorylated PINK1, TOM20, caspase 3/7, and AMPK. Therefore, in terms of reproductive physiology, mitophagy is the removal of mitochondria derived from sperm and the following preservation of mitochondria that are exclusively maternal.

Mitophagy in mammalian follicle development and health

Mitophagy, the cellular process that removes damaged mitochondria, plays a crucial role in maintaining normal cell functions. It is deeply involved in the entire process of follicle development and is associated with various ovarian diseases. This review aims to provide a comprehensive overview of mitophagy regulation, emphasizing its role at different stages of follicular development. Additionally, the study illuminates the relationship between mitophagy and ovarian diseases, including ovary aging (OA), primary ovarian insufficiency (POI), and polycystic ovary syndrome (PCOS). A detailed understanding of mitophagy could reveal valuable insights and novel strategies for managing female ovarian reproductive health.

Organellophagy regulates cell death:A potential therapeutic target for inflammatory diseases

BACKGROUND

Dysregulated alterations in organelle structure and function have a significant connection with cell death, as well as the occurrence and development of inflammatory diseases. Maintaining cell viability and inhibiting the release of inflammatory cytokines are essential measures to treat inflammatory diseases. Recently, many studies have showed that autophagy selectively targets dysfunctional organelles, thereby sustaining the functional stability of organelles, alleviating the release of multiple cytokines, and maintaining organismal homeostasis. Organellophagy dysfunction is critically engaged in different kinds of cell death and inflammatory diseases.

AIM OF REVIEW

We summarized the current knowledge of organellophagy (e.g., mitophagy, reticulophagy, golgiphagy, lysophagy, pexophagy, nucleophagy, and ribophagy) and the underlying mechanisms by which organellophagy regulates cell death.

KEY SCIENTIFIC CONCEPTS OF REVIEW

We outlined the potential role of organellophagy in the modulation of cell fate during the inflammatory response to develop an intervention strategy for the organelle quality control in inflammatory diseases.

RPGR is a guanine nucleotide exchange factor for the small GTPase RAB37 required for retinal function via autophagy regulation

Although the small GTPase RAB37 acts as an organizer of autophagosome biogenesis, the upstream regulatory mechanism of autophagy via guanosine diphosphate (GDP)-guanosine triphosphate (GTP) exchange in maintaining retinal function has not been determined. We found that retinitis pigmentosa GTPase regulator (RPGR) is a guanine nucleotide exchange factor that activates RAB37 by accelerating GDP-to-GTP exchange. RPGR directly interacts with RAB37 via the RPGR-RCC1-like domain to promote autophagy through stimulating exchange. Rpgr knockout (KO) in mice leads to photoreceptor degeneration owing to autophagy impairment in the retina. Notably, the retinopathy phenotypes of Rpgr KO retinas are rescued by the adeno-associated virus-mediated transfer of pre-trans-splicing molecules, which produce normal Rpgr mRNAs via trans-splicing in the Rpgr KO retinas. This rescue upregulates autophagy through the re-expression of RPGR in KO retinas to accelerate GDP-to-GTP exchange; thus, retinal homeostasis reverts to normal. Taken together, these findings provide an important missing link for coordinating RAB37 GDP-GTP exchange via the RPGR and retinal homeostasis by autophagy regulation.

The HIF-1/ BNIP3 pathway mediates mitophagy to inhibit the pyroptosis of fibroblast-like synoviocytes in rheumatoid arthritis

BACKGROUND

Synovial hypoxia, a critical pathological characteristic of rheumatoid arthritis (RA), significantly contributes to synovitis and synovial hyperplasia. In response to hypoxic conditions, fibroblast-like synoviocytes (FLS) undergo adaptive changes involving gene expression modulation, with hypoxia-inducible factors (HIF) playing a pivotal role. The regulation of BCL2/adenovirus e1B 19 kDa protein interacting protein 3 (BNIP3) and nucleotide-binding oligomerization segment-like receptor family 3 (NLRP3) expression has been demonstrated to be regulated by HIF-1. The objective of this study was to examine the molecular mechanism that contributes to the aberrant activation of FLS in response to hypoxia. Specifically, the interaction between BNIP3-mediated mitophagy and NLRP3-mediated pyroptosis was conjointly highlighted.

METHODS

The research methodology employed Western blot and immunohistochemistry techniques to identify the occurrence of mitophagy in synovial tissue affected by RA. Additionally, the levels of mitophagy under hypoxic conditions were assessed using Western blot, immunofluorescence, quantitative polymerase chain reaction (qPCR), and CUT&Tag assays. Pyroptosis was observed through electron microscopy, fluorescence microscopy, and Western blot analysis. Furthermore, the quantity of reactive oxygen species (ROS) was measured. The silencing of HIF-1α and BNIP3 was achieved through the transfection of short hairpin RNA (shRNA) into cells.

RESULTS

In the present study, a noteworthy increase in the expression of BNIP3 and LC3B was observed in the synovial tissue of patients with RA. Upon exposure to hypoxia, FLS of RA exhibited BNIP3-mediated mitophagy and NLRP3 inflammasome-mediated pyroptosis. It appears that hypoxia regulates the expression of BNIP3 and NLRP3 through the transcription factor HIF-1. Additionally, the activation of mitophagy has been observed to effectively inhibit hypoxia-induced pyroptosis by reducing the intracellular levels of ROS.

CONCLUSION

In summary, the activation of FLS in RA patients under hypoxic conditions involves both BNIP3-mediated mitophagy and NLRP3 inflammasome-mediated pyroptosis. Additionally, mitophagy can suppress hypoxia-induced FLS pyroptosis by eliminating ROS and inhibiting the HIF-1α/NLRP3 pathway.

ABHD12 contributes to tumorigenesis and sorafenib resistance by preventing ferroptosis in hepatocellular carcinoma

Sorafenib induces ferroptosis, making it a useful treatment against advanced liver hepatocellular carcinoma (LIHC). However, sorafenib resistance is extremely common among LIHC patients. Here, we used a comprehensive approach to investigate the effects of ABHD12, which regulates tumorigenesis and sorafenib resistance in LIHC. We validated ABHD12 expression was upregulated in LIHC tissue, which correlated with worse overall survival and related to tumor size or stage. ABHD12 facilitated a pro-tumorigenic phenotype involving increased cell proliferation, migration, and clonogenicity as well as sorafenib resistance. Knockout of ABHD12 sensitized liver cancer cells to sorafenib-induced ferroptosis. Co-delivery of sorafenib and ABHD12 inhibitor into a nude mouse model enhanced therapeutic efficacy for LIHC. Our study demonstrates that ABHD12 contributes to tumor growth and sorafenib resistance in liver cancer, which indicate the promising potential of ABHD12 in diagnosis and prognosis as well as highlight the potential therapeutic applications for co-delivery of sorafenib and ABHD12 inhibitor.

Divergent transcriptomic profiles in depressed individuals with hyper- and hypophagia implicating inflammatory status

Major Depressive Disorder (MDD) is a heterogenous and etiologically complex disease encompassing a broad spectrum of psychopathology, presumably arising from distinct pathophysiological mechanisms. Divergent appetitive phenotypes including Hyperphagic MDD (characterized by an increased appetite) and Hypophagic MDD (characterized by a decrease in appetite) are important clinical characteristics that are closely related to comorbidities, including cardiometabolic disorders. Prior evidence supports the notion that hyperphagia is associated with atypical depression, decreased stress-hormone signaling, a pro-inflammatory status, hypersomnia, and poorer clinical outcomes. Yet, our understanding of the underlying mechanisms of Hyperphagic and Hypophagic MDD is limited, and knowledge of associated biological correlates of these endophenotypes remain fragmented. We performed an exploratory study on peripheral blood RNA profiling using bulk RNAseq in unmedicated individuals with Hyperphagic and Hypophagic MDD (n=8 and n=13, respectively) and discovered individual genes and gene pathways associated with appetitive phenotypes. In addition, we used the Maastricht Acute Stress Task to uncover stress-related transcriptomic profiles in Hyper- and Hypophagic MDD.

Tethering ATG16L1 or LC3 induces targeted autophagic degradation of protein aggregates and mitochondria

Proteolysis-targeting chimeras (PROTACs) based on the ubiquitin-proteasome system have made great progress in the field of drug discovery. There is mounting evidence that the accumulation of aggregation-prone proteins or malfunctioning organelles is associated with the occurrence of various age-related neurodegenerative disorders and cancers. However, PROTACs are inefficient for the degradation of such large targets due to the narrow entrance channel of the proteasome. Macroautophagy (hereafter referred to as autophagy) is known as a self-degradative process involved in the degradation of bulk cytoplasmic components or specific cargoes that are sequestered into autophagosomes. In the present study, we report the development of a generalizable strategy for the targeted degradation of large targets. Our results suggested that tethering large target models to phagophore-associated ATG16L1 or LC3 induced targeted autophagic degradation of the large target models. Furthermore, we successfully applied this autophagy-targeting degradation strategy to the targeted degradation of HTT65Q aggregates and mitochondria. Specifically, chimeras consisting of polyQ-binding peptide 1 (QBP) and ATG16L1-binding peptide (ABP) or LC3-interacting region (LIR) induced targeted autophagic degradation of pathogenic HTT65Q aggregates; and the chimeras consisting of mitochondria-targeting sequence (MTS) and ABP or LIR promoted targeted autophagic degradation of dysfunctional mitochondria, hence ameliorating mitochondrial dysfunction in a Parkinson disease cell model and protecting cells from apoptosis induced by the mitochondrial stress agent FCCP. Therefore, this study provides a new strategy for the selective proteolysis of large targets and enrich the toolkit for autophagy-targeting degradation.Abbreviations: ABP: ATG16L1-binding peptide; ATG16L1: autophagy related 16 like 1; ATTEC: autophagy-tethering compound; AUTAC: autophagy-targeting chimera; AUTOTAC: autophagy-targeting chimera; Baf A1: bafilomycin A1; BCL2: BCL2 apoptosis regulator; CALCOCO2/NDP52: calcium binding and coiled-coil domain 2; CASP3: caspase 3; CPP: cell-penetrating peptide; CQ: chloroquine phosphate; DAPI: 4',6-diamidino-2-phenylindole; DCM: dichloromethane; DMF: N,N-dimethylformamide; DMSO: dimethyl sulfoxide; EBSS: Earle's balanced salt solution; FCCP: carbonyl cyanide 4-(trifluoromethoxy)phenylhydrazone; FITC: fluorescein-5-isothiocyanate; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; GFP: green fluorescent protein; HEK293: human embryonic kidney 293; HEK293T: human embryonic kidney 293T; HPLC: high-performance liquid chromatography; HRP: horseradish peroxidase; HTT: huntingtin; LIR: LC3-interacting region; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MFF: mitochondrial fission factor; MTS: mitochondria-targeting sequence; NBR1: NBR1 autophagy cargo receptor; NLRX1: NLR family member X1; OPTN: optineurin; P2A: self-cleaving 2A peptide; PB1: Phox and Bem1p; PBS: phosphate-buffered saline; PE: phosphatidylethanolamine; PINK1: PTEN induced kinase 1; PRKN: parkin RBR E3 ubiquitin protein ligase; PROTACs: proteolysis-targeting chimeras; QBP: polyQ-binding peptide 1; SBP: streptavidin-binding peptide; SDS-PAGE: sodium dodecyl sulfate-polyacrylamide gel electrophoresis; SPATA33: spermatogenesis associated 33; TIMM23: translocase of inner mitochondrial membrane 23; TMEM59: transmembrane protein 59; TOMM20: translocase of outer mitochondrial membrane 20; UBA: ubiquitin-associated; WT: wild type.

Divergent transcriptomic profiles in depressed individuals with hyper- and hypophagia implicating inflammatory status

Major Depressive Disorder (MDD) is a heterogenous and etiologically complex disease encompassing a broad spectrum of psychopathology, presumably arising from distinct pathophysiological mechanisms. Divergent appetitive phenotypes including Hyperphagic MDD (characterized by an increased appetite) and Hypophagic MDD (characterized by a decrease in appetite) are important clinical characteristics that are closely related to comorbidities, including cardiometabolic disorders. Prior evidence supports the notion that hyperphagia is associated with atypical depression, decreased stress-hormone signaling, a pro-inflammatory status, hypersomnia, and poorer clinical outcomes. Yet, our understanding of the underlying mechanisms of Hyperphagic and Hypophagic MDD is limited, and knowledge of associated biological correlates of these endophenotypes remain fragmented. We performed an exploratory study on peripheral blood RNA profiling using bulk RNAseq in unmedicated individuals with Hyperphagic and Hypophagic MDD (n=8 and n=13, respectively) and discovered individual genes and gene pathways associated with appetitive phenotypes. In addition, we used the Maastricht Acute Stress Task to uncover stress-related transcriptomic profiles in Hyper- and Hypophagic MDD.

Role of Macroautophagy in Mammalian Male Reproductive Physiology

Physiologically, autophagy is an evolutionarily conserved and self-degradative process in cells. Autophagy carries out normal physiological roles throughout mammalian life. Accumulating evidence shows autophagy as a mechanism for cellular growth, development, differentiation, survival, and homeostasis. In male reproductive systems, normal spermatogenesis and steroidogenesis need a balance between degradation and energy supply to preserve cellular metabolic homeostasis. The main process of autophagy includes the formation and maturation of the phagophore, autophagosome, and autolysosome. Autophagy is controlled by a group of autophagy-related genes that form the core machinery of autophagy. Three types of autophagy mechanisms have been discovered in mammalian cells: macroautophagy, microautophagy, and chaperone-mediated autophagy. Autophagy is classified as non-selective or selective. Non-selective macroautophagy randomly engulfs the cytoplasmic components in autophagosomes that are degraded by lysosomal enzymes. While selective macroautophagy precisely identifies and degrades a specific element, current findings have shown the novel functional roles of autophagy in male reproduction. It has been recognized that dysfunction in the autophagy process can be associated with male infertility. Overall, this review provides an overview of the cellular and molecular basics of autophagy and summarizes the latest findings on the key role of autophagy in mammalian male reproductive physiology.

Germline stem cells in human

The germline cells are essential for the propagation of human beings, thus essential for the survival of mankind. The germline stem cells, as a unique cell type, generate various states of germ stem cells and then differentiate into specialized cells, spermatozoa and ova, for producing offspring, while self-renew to generate more stem cells. Abnormal development of germline stem cells often causes severe diseases in humans, including infertility and cancer. Primordial germ cells (PGCs) first emerge during early embryonic development, migrate into the gentile ridge, and then join in the formation of gonads. In males, they differentiate into spermatogonial stem cells, which give rise to spermatozoa via meiosis from the onset of puberty, while in females, the female germline stem cells (FGSCs) retain stemness in the ovary and initiate meiosis to generate oocytes. Primordial germ cell-like cells (PGCLCs) can be induced in vitro from embryonic stem cells or induced pluripotent stem cells. In this review, we focus on current advances in these embryonic and adult germline stem cells, and the induced PGCLCs in humans, provide an overview of molecular mechanisms underlying the development and differentiation of the germline stem cells and outline their physiological functions, pathological implications, and clinical applications.

Genetic landscape of a large cohort of Primary Ovarian Insufficiency: New genes and pathways and implications for personalized medicine

Background

Primary Ovarian Insufficiency (POI), a public health problem, affects 1-3.7% of women under 40 yielding infertility and a shorter lifespan. Most causes are unknown. Recently, genetic causes were identified, mostly in single families. We studied an unprecedented large cohort of POI to unravel its molecular pathophysiology.

Methods

375 patients with 70 families were studied using targeted (88 genes) or whole exome sequencing with pathogenic/likely-pathogenic variant selection. Mitomycin-induced chromosome breakages were studied in patients’ lymphocytes if necessary.

Findings

A high-yield of 29.3% supports a clinical genetic diagnosis of POI. In addition, we found strong evidence of pathogenicity for nine genes not previously related to a Mendelian phenotype or POI: ELAVL2, NLRP11, CENPE, SPATA33, CCDC150, CCDC185, including DNA repair genes: C17orf53(HROB), HELQ, SWI5 yielding high chromosomal fragility. We confirmed the causal role of BRCA2, FANCM, BNC1, ERCC6, MSH4, BMPR1A, BMPR1B, BMPR2, ESR2, CAV1, SPIDR, RCBTB1 and ATG7 previously reported in isolated patients/families. In 8.5% of cases, POI is the only symptom of a multi-organ genetic disease. New pathways were identified: NF-kB, post-translational regulation, and mitophagy (mitochondrial autophagy), providing future therapeutic targets. Three new genes have been shown to affect the age of natural menopause supporting a genetic link.

Interpretation

We have developed high-performance genetic diagnostic of POI, dissecting the molecular pathogenesis of POI and enabling personalized medicine to i) prevent/cure comorbidities for tumour/cancer susceptibility genes that could affect life-expectancy (37.4% of cases), or for genetically-revealed syndromic POI (8.5% of cases), ii) predict residual ovarian reserve (60.5% of cases). Genetic diagnosis could help to identify patients who may benefit from the promising in vitro activation-IVA technique in the near future, greatly improving its success in treating infertility.

Funding

Université Paris Saclay, Agence Nationale de Biomédecine.

SPATA33 affects the formation of cell adhesion complex by interacting with CTNNA3 in TM4 cells

Communication between Sertoli cell is essential during spermatogenesis and testicular development in mice, and the dynamic balance of this communication is regulated by some adhesion proteins. In this study, we found that SPATA33 and CTNNA3 were involved in this process. Quantitative real-time PCR and western blotting showed similar trend of expression of two proteins in the testis of mice of different ages. Subsequently, CRISPR-Cas9 technique was used to prepare Spata33 knockout cell lines with TM4 cells, cell wound scratch assay showed that Spata33 gene knockout affected cell migration, and flow cytometry assay showed that Spata33 knockout resulted in a decreased percentage of G1 phase cells in TM4 cell line. In addition, phalloidin staining assay showed that Spata33 gene knockout disrupted the formation of F-actin. Moreover, the protein immunoprecipitation experiment showed the interaction between SPATA33 and CTNNA3, which affected the interaction between CTNNA3 and CTNNB1. SPATA33 inhibits the formation of CDH1-CTNNB1-CTNNA3 complex through its interaction with CTNNA3, thus weakening adhesion between Sertoli cell and promoting cell migration.

Non-coding RNAs: New players in mitophagy and neurodegeneration

Mitophagy controls mitochondrial quality to maintain cellular homeostasis, while aberrations in this process are responsible for neurodegenerative diseases. Mitophagy is initiated through the recruitment of autophagosomes in a ubiquitin-dependent or ubiquitin-independent manner under different stress conditions. Although the detailed molecular mechanisms of how mitophagy processes influence neurodegeneration remain largely uncharacterized, there is mounting evidence indicating that non-coding RNAs (ncRNAs), a variety of endogenous regulators, including microRNAs and long non-coding RNAs, extensively participate in mitophagy processes and play pivotal roles in the aging process and neurodegenerative diseases. Here, we reviewed the major mitophagy pathways modulated by some classical and newly found ncRNAs and summarized the diverse mechanisms in a regulatory network. We also discussed the generalizability of ncRNAs in the development of common neurodegenerative diseases related to proteotoxicity and the importance of mitophagy in the pathogenesis of these diseases. In summary, we propose that ncRNAs act as linkers between mitophagy and neurodegeneration, showing the potential therapeutic application of mitophagy regulation mediated by ncRNAs in neurodegenerative diseases.

DNA methylation changes induced by BDE-209 are related to DNA damage response and germ cell development in GC-2spd

Decabrominated diphenyl ether (BDE-209) is generally utilized in multiple polymer materials as common brominated flame retardant. BDE-209 has been listed as persistent organic pollutants (POPs), which was considered to be reproductive toxin in the environment. But it still remains unclear about the effects of BDE-209 on DNA methylation and the induced-male reproductive toxicity. Due to the extensive epigenetic regulation in germ line development, we hypothesize that BDE-209 exposure impacts the statue of DNA methylation in spermatocytes in vitro. Therefore, the mouse GC-2spd (GC-2) cells were used for the genome wide DNA methylation analysis after treated with 32 μg/mL BDE-209 for 24 hr. The results showed that BDE-209 caused genomic methylation changes with 32,083 differentially methylated CpGs in GC-2 cells, including 16,164 (50.38%) hypermethylated and 15,919 (49.62%) hypomethylated sites. With integrated analysis of DNA methylation data and functional enrichment, we found that BDE-209 might affect the functional transcription in cell growth and sperm development by differential gene methylation. qRT-PCR validation demonstrated the involvement of p53-dependent DNA damage response in the GC-2 cells after BDE-209 exposure. In general, our findings indicated that BDE-209-induced genome wide methylation changes could be interrelated with reproductive dysfunction. This study might provide new insights into the mechanisms of male reproductive toxicity under the environmental exposure to BDE-209.

SPATA33 localizes calcineurin to the mitochondria and regulates sperm motility in mice

Calcineurin is a target of immunosuppressive drugs such as cyclosporine A and tacrolimus. In the immune system, calcineurin interacts with NFAT via the PxIxIT motif to activate T cells. In contrast, little is known about the proteins that interact with a testis-enriched calcineurin that is essential for sperm motility and male fertility. Here, we discovered that calcineurin interacts with SPATA33 via a PQIIIT sequence in the testis. Further analyses reveal that SPATA33 plays critical roles in sperm motility and male fertility. Our finding sheds new light on the molecular mechanisms of sperm motility regulation and the etiology of human male fertility. Furthermore, it may help us not only understand reproductive toxicities but also develop nonhormonal male contraceptives.

Calcineurin is a calcium-dependent phosphatase that plays roles in a variety of biological processes including immune responses. In spermatozoa, there is a testis-enriched calcineurin composed of PPP3CC and PPP3R2 (sperm calcineurin) that is essential for sperm motility and male fertility. Because sperm calcineurin has been proposed as a target for reversible male contraceptives, identifying proteins that interact with sperm calcineurin widens the choice for developing specific inhibitors. Here, by screening the calcineurin-interacting PxIxIT consensus motif in silico and analyzing the function of candidate proteins through the generation of gene-modified mice, we discovered that SPATA33 interacts with sperm calcineurin via a PQIIIT sequence. Spata33 knockout mice exhibit reduced sperm motility because of an inflexible midpiece, leading to impaired male fertility, which phenocopies Ppp3cc and Ppp3r2 knockout mice. Further analysis reveals that sperm calcineurin disappears from the mitochondria in the Spata33 knockout testis. In addition, immunoprecipitation analysis indicates that sperm calcineurin interacts with not only SPATA33 but also the mitochondrial protein VDAC2. These results indicate that SPATA33 localizes calcineurin to the mitochondria and regulates sperm motility.

Mitophagy in carcinogenesis, drug resistance and anticancer therapeutics

The mitochondrion is an organelle that plays a vital role in energy production, cytoplasmic protein degradation and cell death. Mitophagy is an autophagic procedure that specifically clears damaged mitochondria and maintains its homeostasis. Emerging evidence indicates that mitophagy is involved in many physiological processes, including cellular homeostasis, cellular differentiation and nerve protection. In this review, we describe the regulatory mechanisms of mitophagy in mammals and yeasts and highlight the recent advances relevant to its function in carcinogenesis and drug resistance. Finally, a section has been dedicated to describing the role of mitophagy in anticancer therapeutics, which is a new frontier that offers a precise and promising strategy.

SPATA33 functions as a mitophagy receptor in mammalian germline

Mitophagy is an essential mechanism in maintaining cellular homeostasis, in which damaged and superfluous mitochondria are selectively degraded by the autophagy-lysosome pathway. Our recent study revealed that SPATA33 functions as a novel receptor for mitophagy in the priming of mitochondria for degradation in male germline cells. SPATA33 directly mediates the interaction of the outer mitochondrial membrane protein VDAC2 with the autophagy machinery component ATG16L1 during mitophagy. Upon starvation induction, SPATA33 can promote mitophagy as an autophagy receptor. Thus, SPATA33 confers cargo selectivity during mitophagy in germline cells. These findings provide new insights into selective autophagy and mitochondrial homeostasis.