Amy V. Kaucher

Background Premature ovarian insufficiency (POI) is characterized by the progressive decline of ovarian function before the age of 40 years, classically presenting with menstrual irregularities paired with elevated FSH, affecting approximately 1-4% of women worldwide. The aetiology is complex and causes range from chromosomal and autoimmune factors to iatrogenic forms, but most non-syndromic cases are thought to have a genetic basis. To date, numerous genes have been implicated, and familial clustering strongly supports high heritability. However, despite technological advances, it is difficult to identify causal genetic variants for most patients, indicating that many cases of POI could have a polygenic background. Given the significant impact of POI on fertility and health, a comprehensive synthesis of current genetic findings is needed. Objective and rationale The objective of this systematic review is to provide a comprehensive synthesis of genes and genomic regions implicated in non-syndromic POI. The primary outcome was genes or genetic loci associated with POI. Contrary to earlier systematic reviews on female infertility, we included both monogenic and polygenic studies, as well as patients with primary and secondary amenorrhea, to provide an overview of the diverse genetic landscape of non-syndromic POI. Search methods A systematic literature search was conducted in PubMed, Scopus, Web of Science, and Embase. Publications up to 13 February 2026 that investigated genetic causes of non-syndromic POI and were written in English were included. Studies limited to animal experimentation were excluded, as were reviews, meta-analyses, and non-peer reviewed material, such as abstracts and conference proceedings. Outcomes This systematic review identified 432 eligible studies from an initial pool of 5,586 records, encompassing both hypothesis-free and candidate-gene approaches, including a total of 47,680 individuals with non-syndromic POI. Across all studies, 859 genes and 102 unique genomic regions were implicated in POI. Most studies were classified as candidate-gene investigations, whereas approximately one-in-six studies employed hypothesis-free approaches. Quality assessment of hypothesis-free studies showed primarily moderate to poor methodological quality. From the hypothesis-free studies, 422 genes were linked to non-syndromic POI, 120 of which clustered with functionality in DNA recombination. Twenty-five genes showed moderate genetic evidence for a role in POI and were enriched in pathways related to meiosis, DNA repair, and female gamete development. Despite substantial research activity, approximately nine out of ten non-syndromic patients remained without a recognised genetic aetiology. Wider implications As most patients with non-syndromic POI lack a single causal variant, evidence suggests the condition with secondary amenorrhea could be largely polygenic and shaped by the combined effects of multiple genetic factors and their interaction with non-genetic influences. A focus on monogenic causes could overlook patients with high polygenic burden. Future genetic studies on POI should examine both monogenic and polygenic risk variants and investigate genetic differences across POI subtypes. Such strategies will be critical for improving genetic diagnosis, risk stratification, and the development of personalized reproductive care. Registration number Prospero - CRD42023469800

Pathogenic variants in FANCM have been implicated in premature ovarian insufficiency, suggesting a critical role for FANCM in early germline development. To investigate this gene’s function in a controlled system, we evaluated whether a mouse in vitro primordial germ cell (PGC) model could be used to interrogate the consequences of FANCM loss on germ cell specification. Using CRISPR-Cas9 gene editing, we introduced a premature stop codon into exon 1 of Fancm in mouse embryonic stem cells. These edited cells were differentiated into epiblast-like cells and subsequently into primordial germ cell-like cells (PGCLCs), which were assessed for their developmental competence. After successful generation of in vitro -derived PGCLCs, we found that loss of FANCM markedly reduced PGCLC formation, consistent with previously reported in vivo phenotypes. Our findings demonstrate that this in vitro system provides a tractable platform for dissecting gene function in otherwise inaccessible stages of germline development. Moreover, our data suggest that FANCM is required at the earliest stages of PGC specification, potentially as early as the developmental window equivalent to embryonic day 8.5, a period not previously examined in vivo .

Menopause not only signifies the end of a woman’s reproductive life, but also brings about significant changes in both mental and physical health due to hormonal changes. Age of natural menopause (ANM) and reproductive lifespan is determined by the formation and subsequent depletion of follicles in females. In this study, we identified a robust association between a common functional missense variant in PARP1 and age at menopause in a sample of 201,323 women. Using an in vitro model to generate primordial germ cells - the precursors of sperm and oocytes- we report that Parp1 affects PGCs in two different ways. Our identified missense variant (V762A) significantly reduces the germ cell population by enhanced DNA binding resulting in increased apoptosis. Conversely, deletion of Parp1 results in an increased population of PGCs and proteomic analysis revealed that transcription factors that drive PGC formation show increased expression in precursor cells. This is caused by increased transcription of Rhox genes ( Rhox2A , Rhox6 and Rhox9 ), implicating Parp1 in downregulation of genes that determine PGC fate. We propose that Parp1 regulates PGC fate and that its increased chromatin association (‘trapping’) causes a decreased population of PGCs, thereby providing a molecular cause of the earlier onset menopause on female carriers of the variant.

Oxytocin may have promise as a treatment for neuropsychiatric disorders. Its therapeutic effect may depend on its ability to enter the brain and bind to the oxytocin receptor. To date, the brain tissue penetrance of intranasal oxytocin has not been demonstrated. In this nonhuman primate study, we administer deuterated oxytocin intranasally and intravenously to rhesus macaques and measure, with mass spectrometry, concentrations of labeled (exogenously administered) and endogenous oxytocin in 12 brain regions two hours after oxytocin administration. Labeled oxytocin is quantified after intranasal (not intravenous) administration in brain regions (orbitofrontal cortex, striatum, brainstem, and thalamus) that lie in the trajectories of the olfactory and trigeminal nerves. These results suggest that intranasal administration bypasses the blood–brain barrier, delivering oxytocin to specific brain regions, such as the striatum, where oxytocin acts to impact motivated behaviors. Further, high concentrations of endogenous oxytocin are in regions that overlap with projection fields of oxytocinergic neurons.

Genome editing tools have revolutionized the generation of genetically modified animals including livestock. In particular, the domestic pig is a proven model of human physiology and an agriculturally important species. In this study, we utilized the CRISPR/Cas9 system to edit theNANOS2gene in pig embryos to generate offspring with mono-allelic and bi-allelic mutations. We found thatNANOS2knockout pigs phenocopy knockout mice with male specific germline ablation but other aspects of testicular development are normal. Moreover, male pigs with one intactNANOS2allele and female knockout pigs are fertile. From an agriculture perspective,NANOS2knockout male pigs are expected to serve as an ideal surrogate for transplantation of donor spermatogonial stem cells to expand the availability of gametes from genetically desirable sires.

Precise separation of spermatogonial stem cells (SSCs) from progenitor spermatogonia that lack stem cell activity and are committed to differentiation remains a challenge. To distinguish between these spermatogonial subtypes, we identified genes that exhibited bimodal mRNA levels at the single cell level among undifferentiated spermatogonia from the Postnatal Day 6 (P6) mouse testis, including Tspan8, Epha2 and Pvr, each of which encode cell-surface proteins useful for cell selection. Transplantation studies provided definitive evidence that a TSPAN8-high subpopulation is enriched for SSCs. RNA-seq analyses identified genes differentially expressed between TSPAN8-high and -low subpopulations that clustered into multiple biological pathways potentially involved in SSC renewal or differentiation, respectively. Methyl-seq analysis identified hypomethylated domains in the promoters of these genes in both subpopulations that colocalized with peaks of histone modifications defined by ChIP-seq analysis. Taken together, these results demonstrate functional heterogeneity among mouse undifferentiated spermatogonia and point to key biological characteristics that distinguish SSCs from progenitor spermatogonia.

Hypoxic, hyperosmotic, and genotoxic stress slow mouse trophoblast stem cell (mTSC) proliferation, decrease potency/stemness, and increase differenti

The maintenance of cycling cell lineages relies on undifferentiated subpopulations consisting of stem and progenitor pools. Features that delineate these cell types are undefined for many lineages, including spermatogenesis, which is supported by an undifferentiated spermatogonial population. Here, we generated a transgenic mouse line in which spermatogonial stem cells are marked by expression of an inhibitor of differentiation 4 (Id4)-green fluorescent protein (Gfp) transgene. We found that Id4-Gfp⁺ cells exist primarily as a subset of the type A_single pool, and their frequency is greatest in neonatal development and then decreases in proportion during establishment of the spermatogenic lineage, eventually comprising ∼2% of the undifferentiated spermatogonial population in adulthood. RNA sequencing analysis revealed that expression of 11 and 25 genes is unique for the Id4-Gfp⁺/stem cell and Id4-Gfp⁻/progenitor fractions, respectively. Collectively, these findings provide the first definitive evidence that stem cells exist as a rare subset of the A_single pool and reveal transcriptome features distinguishing stem cell and progenitor states within the mammalian male germline.

Continuity of cycling cell lineages relies on the activities of undifferentiated stem cell-containing subpopulations. Transition to a differentiating state must occur periodically in a fraction of the population to supply mature cells, coincident with maintenance of the undifferentiated state in others to sustain a foundational stem cell pool. At present, molecular mechanisms regulating these activities are poorly defined for most cell lineages. Spermatogenesis is a model process that is supported by an undifferentiated spermatogonial population and transition to a differentiating state involves attained expression of the KIT receptor. We found that impaired function of the X chromosome-clustered microRNAs 221 and 222 (miR-221/222) in mouse undifferentiated spermatogonia induces transition from a KIT^– to a KIT⁺ state and loss of stem cell capacity to regenerate spermatogenesis. Both Kit mRNA and KIT protein abundance are influenced by miR-221/222 function in spermatogonia. Growth factors that promote maintenance of undifferentiated spermatogonia upregulate miR-221/222 expression; whereas exposure to retinoic acid, an inducer of spermatogonial differentiation, downregulates miR-221/222 abundance. Furthermore, undifferentiated spermatogonia overexpressing miR-221/222 are resistant to retinoic acid-induced transition to a KIT⁺ state and are incapable of differentiation in vivo. These findings indicate that miR-221/222 plays a crucial role in maintaining the undifferentiated state of mammalian spermatogonia through repression of KIT expression.