Inactivation of Wt1 causes pre-granulosa cell to steroidogenic cell transformation and defect of ovary development†

Generation of a Wt1 conditional deletion, nuclear red fluorescent protein reporter allele in the mouse

A Wt1 conditional deletion, nuclear red fluorescent protein (RFP) reporter allele was generated in the mouse by gene targeting in embryonic stem cells. Upon Cre-mediated recombination, a deletion allele is generated that expresses RFP in a Wt1-specific pattern. RFP expression was detected in embryonic and adult tissues known to express Wt1, including the kidney, mesonephros, and testis. In addition, RFP expression and WT1 co-localization was detected in the adult uterine stroma and myometrium, suggesting a role in uterine function. Crosses with Wnt7a-Cre transgenic mice that express Cre in the Müllerian duct epithelium activate Wt1-directed RFP expression in the epithelium of the oviduct but not the stroma and myometrium of the uterus. This new mouse strain should be a useful resource for studies of Wt1 function and marking Wt1-expressing cells.

Dysregulated RNA editing of EIF2AK2 in polycystic ovary syndrome: clinical relevance and functional implications

BACKGROUND

Polycystic ovary syndrome (PCOS) is a prevalent endocrine disorder affecting women of reproductive ages. Our previous study has implicated a possible link between RNA editing and PCOS, yet the actual role of RNA editing, its association with clinical features, and the underlying mechanisms remain unclear.

METHODS

Ten RNA-Seq datasets containing 269 samples of multiple tissue types, including granulosa cells, T helper cells, placenta, oocyte, endometrial stromal cells, endometrium, and adipose tissues, were retrieved from public databases. Peripheral blood samples were collected from twelve PCOS and ten controls and subjected to RNA-Seq. Transcriptome-wide RNA-Seq data analysis was conducted to identify differential RNA editing (DRE) between PCOS and controls. The functional significance of DRE was evaluated by luciferase reporter assays and overexpression in human HEK293T cells. Dehydroepiandrosterone and lipopolysaccharide were used to stimulate human KGN granulosa cells to evaluate gene expression.

RESULTS

RNA editing dysregulations across multiple tissues were found to be associated with PCOS in public datasets. Peripheral blood transcriptome analysis revealed 798 DRE events associated with PCOS. Through weighted gene co-expression network analysis, our results revealed a set of hub DRE events in PCOS blood. A DRE event in the eukaryotic translation initiation factor 2-alpha kinase 2 (EIF2AK2:chr2:37,100,559) was associated with PCOS clinical features such as luteinizing hormone (LH) and the ratio of LH over follicle-stimulating hormone. Luciferase assays, overexpression, and knockout of RNA editing enzyme adenosine deaminase RNA specific (ADAR) showed that the ADAR-mediated editing cis-regulated EIF2AK2 expression. EIAF2AK2 showed a higher expression after dehydroepiandrosterone and lipopolysaccharide stimulation, triggering changes in the downstrean MAPK pathway.

CONCLUSIONS

Our study presented the first evidence of cross-tissue RNA editing dysregulation in PCOS and its clinical associations. The dysregulation of RNA editing mediated by ADAR and the disrupted target EIF2AK2 may contribute to PCOS development via the MPAK pathway, underlining such epigenetic mechanisms in the disease.

P62 promotes FSH-induced antral follicle formation by directing degradation of ubiquitinated WT1

In females, the pathophysiological mechanism of poor ovarian response (POR) is not fully understood. Considering the expression level of p62 was significantly reduced in the granulosa cells (GCs) of POR patients, this study focused on identifying the role of the selective autophagy receptor p62 in conducting the effect of follicle-stimulating hormone (FSH) on antral follicles (AFs) formation in female mice. The results showed that p62 in GCs was FSH responsive and that its level increased to a peak and then decreased time-dependently either in ovaries or in GCs after gonadotropin induction in vivo. GC-specific deletion of p62 resulted in subfertility, a significantly reduced number of AFs and irregular estrous cycles, which were same as pathophysiological symptom of POR. By conducting mass spectrum analysis, we found the ubiquitination of proteins was decreased, and autophagic flux was blocked in GCs. Specifically, the level of nonubiquitinated Wilms tumor 1 homolog (WT1), a transcription factor and negative controller of GC differentiation, increased steadily. Co-IP results showed that p62 deletion increased the level of ubiquitin-specific peptidase 5 (USP5), which blocked the ubiquitination of WT1. Furthermore, a joint analysis of RNA-seq and the spatial transcriptome sequencing data showed the expression of steroid metabolic genes and FSH receptors pivotal for GCs differentiation decreased unanimously. Accordingly, the accumulation of WT1 in GCs deficient of p62 decreased steroid hormone levels and reduced FSH responsiveness, while the availability of p62 in GCs simultaneously ensured the degradation of WT1 through the ubiquitin‒proteasome system and autophagolysosomal system. Therefore, p62 in GCs participates in GC differentiation and AF formation in FSH induction by dynamically controlling the degradation of WT1. The findings of the study contributes to further study the pathology of POR.

Characterization of Two Gonadal Genes, zar1 and wt1b, in Hermaphroditic Fish Asian Seabass (Lates calcarifer)

Zygote arrest-1 (Zar1) and Wilms' tumor 1 (Wt1) play an important role in oogenesis, with the latter also involved in testicular development and gender differentiation. Here, Lczar1 and Lcwt1b were identified in Asian seabass (Lates calcarifer), a hermaphrodite fish, as the valuable model for studying sex differentiation. The cloned cDNA fragments of Lczar1 were 1192 bp, encoding 336 amino acids, and contained a zinc-binding domain, while those of Lcwt1b cDNA were 1521 bp, encoding a peptide of 423 amino acids with a Zn finger domain belonging to Wt1b family. RT-qPCR analysis showed that Lczar1 mRNA was exclusively expressed in the ovary, while Lcwt1b mRNA was majorly expressed in the gonads in a higher amount in the testis than in the ovary. In situ hybridization results showed that Lczar1 mRNA was mainly concentrated in oogonia and oocytes at early stages in the ovary, but were undetectable in the testis. Lcwt1b mRNA was localized not only in gonadal somatic cells (the testis and ovary), but also in female and male germ cells in the early developmental stages, such as those of previtellogenic oocytes, spermatogonia, spermatocytes and spermatids. These results indicated that Lczar1 and Lcwt1b possibly play roles in gonadal development. Therefore, the findings of this study will provide a basis for clarifying the mechanism of Lczar1 and Lcwt1b in regulating germ cell development and the sex reversal of Asian seabass and even other hermaphroditic species.

Current progress on in vitro differentiation of ovarian follicles from pluripotent stem cells

Mammalian female reproduction requires a functional ovary. Competence of the ovary is determined by the quality of its basic unit-ovarian follicles. A normal follicle consists of an oocyte enclosed within ovarian follicular cells. In humans and mice, the ovarian follicles are formed at the foetal and the early neonatal stage respectively, and their renewal at the adult stage is controversial. Extensive research emerges recently to produce ovarian follicles in-vitro from different species. Previous reports demonstrated the differentiation of mouse and human pluripotent stem cells into germline cells, termed primordial germ cell-like cells (PGCLCs). The germ cell-specific gene expressions and epigenetic features including global DNA demethylation and histone modifications of the pluripotent stem cells-derived PGCLCs were extensively characterized. The PGCLCs hold potential for forming ovarian follicles or organoids upon cocultured with ovarian somatic cells. Intriguingly, the oocytes isolated from the organoids could be fertilized in-vitro. Based on the knowledge of in-vivo derived pre-granulosa cells, the generation of these cells from pluripotent stem cells termed foetal ovarian somatic cell-like cells was also reported recently. Despite successful in-vitro folliculogenesis from pluripotent stem cells, the efficiency remains low, mainly due to the lack of information on the interaction between PGCLCs and pre-granulosa cells. The establishment of in-vitro pluripotent stem cell-based models paves the way for understanding the critical signalling pathways and molecules during folliculogenesis. This article aims to review the developmental events during in-vivo follicular development and discuss the current progress of generation of PGCLCs, pre-granulosa and theca cells in-vitro.

Epg5 deficiency leads to primary ovarian insufficiency due to WT1 accumulation in mouse granulosa cells

Primary ovarian insufficiency (POI), also known as premature ovarian failure, is an ovarian defect in humans characterized by the premature depletion of ovarian follicles before the age of 40. However, the mechanisms underlying POI remain largely unknown. Here, we show that knockout of Epg5 (ectopic P-granules autophagy protein 5 homolog (C. elegans)) results in subfertility in female mice, which exhibit a POI-like phenotype. Single-cell RNA sequencing analysis revealed that the knockout of Epg5 affected the differentiation of granulosa cells (GCs). Further investigation demonstrated that knockout of Epg5 blocks macroautophagic/autophagic flux, resulting in the accumulation of WT1 (WT1 transcription factor), an essential transcription factor for GCs, suggesting WT1 needs to be selectively degraded by the autophagy pathway. We found that the insufficient degradation of WT1 in the antral follicular stage contributes to reduced expression of steroidogenesis-related genes, thereby disrupting GC differentiation. Collectively, our studies show that EPG5 promotes WT1 degradation in GCs, indicating that the dysregulation of Epg5 in GCs can trigger POI pathogenesis.Abbreviations: 3-MA, 3-methyladenine; CHX, cycloheximide; CQ, chloroquine; EPG5, ectopic P-granules autophagy protein 5 homolog (C. elegans); GC, granulosa cell; MAP1LC3/LC3, microtubule-associated protein 1 light chain 3; MII, metaphase II; POI, primary ovarian insufficiency; PB1, polar body 1; SQSTM1/p62, sequestosome 1; WT1, WT1 transcription factor.

Dissecting the fate of Foxl2-expressing cells in fetal ovary using lineage tracing and single-cell transcriptomics

Gonad somatic cells acquire sex-specific fates during sex determination. In XX gonad, a subset of somatic cells expresses Foxl2 after sex determination which is considered the progenitor of granulosa cells. However, whether these cells also contribute to other cell types at later developmental stages is unknown. In the present study, the cell fate of Foxl2-expressing cells in fetal ovaries was analyzed by lineage tracing and single-cell transcriptomics. We found that Foxl2-expressing cells gave rise to three cell types at later developmental stages, including granulosa cells, theca-interstitial cells, and stromal cells. Series single-cell RNA sequencing revealed FOXL2-positive cells were divided into two clusters at P0. One group further differentiated into granulosa cells and Theca-G (Theca-interstitial cells derived from granulosa) at P14. Another group was classified as stromal cell lineage, then a small portion of them further differentiated into 3β-HSD-positive Theca-S (Theca-interstitial cells derived from stroma). Cyp17a1 was expressed in Theca-S, but not in Theca-G. This study demonstrated that Folx2-expressing cells in XX gonad after sex determination are multipotent and theca-interstitial cells are derived from different progenitors. Our data provided an important resource, at single-cell resolution, for a better understanding of somatic cell differentiation in ovary development.

Polycomb subunit Pcgf2 mediates ovulation and fertility through transcriptional regulation progesterone receptor

Ovarian follicles are the fundamental structure to support oocyte development, which provides mature oocytes for offspring. This process requires granulosa cells (GCs) to respond to the midcycle surge of hormones, leading to GC proliferation and differentiation by a series of genes' transcriptional expression changes. Epigenetic mediator, Polycomb Repressive Complex 1 (PRC1) has been reported to function in fetal ovarian development. However, its functional relevance to folliculogenesis and ovulation remains unknown. In this study, we demonstrated that GC-selective depletion of PCGF2, a key component of PRC1, led to the loss of follicles, ovulation defects, and a lengthened estrus cycle, resulting in subfertility in female mice. The expression of PCGF2 is in the GCs of growing follicles and increases after human chorionic gonadotropin (hCG) stimulation. PCGF2 bound to the promoter of the key ovulation gene progesterone receptor (Pgr) and upregulated the expression of Pgr by targeting the epigenetic modification of H2AK119ub1 after hCG surge. Consistently, the expression of downstream genes of Pgr also sharply decreased, which resulted in the follicular rupture failed and oocyte entrapped in corpus luteum in GC-specific Pcgf2 knockout mice. Together, our study identified that PCGF2 is essential for folliculogenesis and ovulation via modulating hormone receptor expression.

The functions of Wt1 in mouse gonad development and somatic cells differentiation

Wilms' tumour 1 (Wt1) encodes a zinc finger nuclear transcription factor which is mutated in 15-20% of Wilms' tumor, a pediatric kidney tumor. Wt1 has been found to be involved in the development of many organs. In gonads, Wt1 is expressed in genital ridge somatic cells before sex determination, and its expression is maintained in Sertoli cells and granulosa cells after sex determination. It has been demonstrated that Wt1 is required for the survival of the genital ridge cells. Homozygous mutation of Wt1 causes gonad agenesis. Recent studies find that Wt1 plays important roles in lineage specification and maintenance of gonad somatic cells. In this review, we will summarize the recent research works about Wt1 in gonadal somatic cell differentiation.

Autophagy regulates differentiation of ovarian granulosa cells through degradation of WT1

Ovarian granulosa cells (GCs) proliferate and differentiate along with follicular growth, and this is indispensable for oocyte development and female fertility. Although the role of macroautophagy/autophagy in ovarian function has been reported, its contribution to the regulation of GC characteristics remains elusive. The siRNA-mediated knockdown of two key autophagy-related genes ATG5 and BECN1 and the autophagy inhibitor chloroquine were used to interfere with autophagy in GCs. Inhibition of autophagy both genetically and pharmacologically resulted in decreased expression of genes associated with GC differentiation, including CYP19A1/Aromatase and FSHR, as well as in reduced estradiol synthesis. Mechanistically, when autophagy was disrupted, the transcription factor WT1 accumulated in GCs due to its insufficient degradation by the autophagic pathway, and this inhibited GC differentiation. Finally, decreased expression of several autophagy-related genes, as well as reduced LC3-II:LC3-I and elevated SQSTM1/p62 protein levels, which are indications of decreased autophagy, were detected in GCs from biochemical premature ovarian insufficiency patients. In summary, our study reveals that autophagy regulates the differentiation of ovarian GCs by degrading WT1 and that insufficient autophagy might be involved in ovarian dysfunction.

Whole exome sequencing identified a rare WT1 loss-of-function variant in a non-syndromic POI patient

BACKGROUND

Premature ovarian insufficiency (POI) is a highly heterogeneous disease, and up to 25% of cases can be explained by genetic causes. The transcription factor WT1 has long been reported to play a crucial role in ovary function. Wt1-mutated female mice exhibited POI-like phenotypes.

METHODS AND RESULTS

In this study, whole exome sequencing (WES) was applied to find the cause of POI in Han Chinese women. A nonsense variant in the WT1 gene: NM_024426.6:c.1387C>T(p.R463*) was identified in a non-syndromic POI woman. The variant is a heterozygous de novo mutation that is very rare in the human population. The son of the patient inherited the mutation and developed Wilms' tumor and urethral malformation at the age of 7. According to the American College of Medical Genetics and Genomics and the Association for Molecular Pathology (ACMG/AMP) guidelines, the novel variant is categorized as pathogenic. Western blot analysis further demonstrated that the WT1 variant could produce a truncated WT1 isoform in vitro.

CONCLUSIONS

A rare heterozygous nonsense WT1 mutant is associated with non-syndromic POI and Wilms' tumor. Our finding characterized another pathogenic WT1 variant, providing insight into genetic counseling.

Understanding Transcriptomic and Serological Differences between Forced Molting and Natural Molting in Laying Hens

Molting is natural adaptation to climate change in all birds, including chickens. Forced molting (FM) can rejuvenate and reactivate the reproductive potential of aged hens, but the effect of natural molting (NM) on older chickens is not clear. To explore why FM has a dramatically different effect on chickens compared with NM, the transcriptome analyses of the hypothalamus and ovary in forced molted and natural molted hens at two periods with feathers fallen and regrown were performed. Additionally, each experimental chicken was tested for serological indices. The results of serological indices showed that growth hormone, thyroid stimulating hormone, and thyroxine levels were significantly higher (p < 0.05) in forced molted hens than in natural molted hens, and calcitonin concentrations were lower in the forced molted than in the natural molted hens. Furthermore, the transcriptomic analysis revealed a large number of genes related to disease resistance and anti-aging in the two different FM and NM periods. These regulatory genes and serological indices promote reproductive function during FM. This study systematically revealed the transcriptomic and serological differences between FM and NM, which could broaden our understanding of aging, rejuvenation, egg production, and welfare issues related to FM in chickens.

rno-miR-128-3p promotes apoptosis in rat granulosa cells (GCs) induced by norepinephrine through Wilms tumor 1 (WT1)

The mechanism related to ovarian follicular is complex, which has not been fully elucidated. Abundant reports have confirmed that the ovarian function development is closely related to sympathetic innervation. As one of the major neurotransmitters, norepinephrine (NE) is considered an effective regulator of ovarian functions like granulosa cell (GC) apoptosis. However, the mechanism between NE and GC apoptosis in rat is still unclear. In our study, GCs were isolated and cultured in vitro with NE treatment. The apoptosis of GCs was facilitated by NE. Wilms tumor 1 (WT1) was found to be significantly downregulated in GCs after NE treatment, and overexpression of WT1 repressed apoptosis in rat GCs induced by NE. rno-miR-128-3p was found to be significantly enhanced by NE in GCs, and inhibition of rno-miR-128-3p repressed apoptosis in rat GCs induced by NE. Mechanistically, rno-miR-128-3p interacted with WT1 and repressed its expression. In summary, inhibition of rno-miR-128-3p may enhance WT1 expression, and then repress NE-induced apoptosis in rat GCs. Our research may provide a new insight for the improvement of ovarian follicular development.

PRMT5 regulates ovarian follicle development by facilitating Wt1 translation

Protein arginine methyltransferase 5 (Prmt5) is the major type II enzyme responsible for symmetric dimethylation of arginine. Here, we found that PRMT5 was expressed at high level in ovarian granulosa cells of growing follicles. Inactivation of Prmt5 in granulosa cells resulted in aberrant follicle development and female infertility. In Prmt5-knockout mice, follicle development was arrested with disorganized granulosa cells in which WT1 expression was dramatically reduced and the expression of steroidogenesis-related genes was significantly increased. The premature differentiated granulosa cells were detached from oocytes and follicle structure was disrupted. Mechanism studies revealed that Wt1 expression was regulated by PRMT5 at the protein level. PRMT5 facilitated IRES-dependent translation of Wt1 mRNA by methylating HnRNPA1. Moreover, the upregulation of steroidogenic genes in Prmt5-deficient granulosa cells was repressed by Wt1 overexpression. These results demonstrate that PRMT5 participates in granulosa cell lineage maintenance by inducing Wt1 expression. Our study uncovers a new role of post-translational arginine methylation in granulosa cell differentiation and follicle development.

Infertility in women can be caused by many factors, such as defects in the ovaries. An important part of the ovaries for fertility are internal structures called follicles, which house early forms of egg cells. A follicle grows and develops until the egg is finally released from the ovary into the fallopian tube, where the egg can then be fertilised. In the follicle, an egg is surrounded by other types of cells, such as granulosa cells. The egg and neighbouring cells must maintain healthy contacts with each other, otherwise the follicle can stop growing and developing, potentially causing infertility.

The development of a follicle depends on an array of proteins. For example, the transcription factor WT1 controls protein levels by activating other genes and their proteins and is produced in high numbers by granulosa cells at the beginning of follicle development. Although WT1 levels dip towards the later stages of follicle development, insufficient levels can lead to defects. So far, it has been unclear how levels of WT1in granulose cells are regulated.

Chen, Dong et al. studied mouse follicles to reveal more about the role of WT1 in follicle development. The researchers measured protein levels in mouse granulosa cells as the follicles developed, and discovered elevated levels of PRMT5, a protein needed for egg cells to form and survive in the follicles. Blocking granulosa cells from producing PRMT5 led to abnormal follicles and infertility in mice. Moreover, mice that had been engineered to lack PRMT5 developed abnormal follicles, where the egg and surrounding granulosa cells were not attached to each other, and the granulosa cells had low levels of WT1. Further experiments revealed that PRMT5 controlled WT1 levels by adding small molecules called methyl groups to another regulatory protein called HnRNPA1.

The addition of methyl groups to genes or their proteins is an important modification that takes place in many processes within a cell. Chen, Dong et al. reveal that this activity also plays a key role in maintaining healthy follicle development in mice, and that PRMT5 is necessary for controlling WT1. Identifying all of the intricate mechanism involved in regulating follicle development is important for finding ways to combat infertility.

WT1 Pathogenic Variants are Associated with a Broad Spectrum of Differences in Sex Development Phenotypes and Heterogeneous Progression of Renal Disease

Wilms' tumor suppressor gene 1 (WT1) plays an essential role in urogenital and kidney development. Heterozygous germline pathogenic allelic variants of WT1 have been classically associated with Denys-Drash syndrome (DDS) and Frasier syndrome (FS). Usually, exonic pathogenic missense variants in the zinc finger region are the cause of DDS, whereas pathogenic variants affecting the canonic donor lysine-threonine-serine splice site in intron 9 cause FS. Phenotypic overlap between WT1 disorders has been frequently observed. New WT1 variant-associated phenotypes, such as 46,XX testicular/ovarian-testicular disorders of sex development (DSD) and primary ovarian insufficiency, have been reported. In this report, we describe the phenotypes and genotypes of 7 Brazilian patients with pathogenic WT1 variants. The molecular study involved Sanger sequencing and massively parallel targeted sequencing using a DSD-associated gene panel. Six patients (5 with a 46,XY karyotype and 1 with a 46,XX karyotype) were initially evaluated for atypical genitalia, and a 46,XY patient with normal female genitalia sought medical attention for primary amenorrhea. Germ cell tumors were identified in 2 patients, both with variants affecting alternative splicing of WT1 between exons 9 and 10. Two pathogenic missense WT1 variants were identified in two 46,XY individuals with Wilms' tumors; both patients were <1 year of age at the time of diagnosis. A novel WT1 variant, c.1453_1456 (p.Arg485Glyfs*14), was identified in a 46,XX patient with testicular DSD. Nephrotic proteinuria was diagnosed in all patients, including 3 who underwent renal transplantation after progressing to end-stage kidney disease. The expanding phenotypic spectrum associated with WT1 variants in XY and XX individuals confirms their pivotal role in gonadal and renal development as well as in tumorigenesis, emphasizing the clinical implications of these variants in genetic diagnosis.

Retinoic Acid Induced Protein 14 (Rai14) is dispensable for mouse spermatogenesis

BACKGROUND

Retinoic Acid Induced Protein 14 (Rai14) is an evolutionarily conserved gene that is highly expressed in the testis. Previous experiments have reported that small interfering RNA (siRNA)-mediated gene knockdown (KD) of Rai14 in rat testis disrupted spermatid polarity and transport. Of note, a gene knockout (KO) model is considered the "gold standard" for in vivo assessment of crucial gene functions. Herein, we used CRISPR/Cas9-based gene editing to investigate the in vivo role of Rai14 in mouse testis.

METHODS

Sperm concentration and motility were assayed using a computer-assisted sperm analysis (CASA) system. Histological and immunofluorescence (IF) staining and transmission electron microscopy (TEM) were used to visualize the effects of Rai14 KO in the testes and epididymides. Terminal deoxynucleotidyl transferase-dUTP nick-end labeling (TUNEL) was used to determine apoptotic cells. Gene transcript levels were calculated by real-time quantitative PCR.

RESULTS

Rai14 KO in mice depicted normal fertility and complete spermatogenesis, which is in sharp contrast with the results reported previously in a Rai14 KD rat model. Sperm parameters and cellular apoptosis did not appear to differ between wild-type (WT) and KO group. Mechanistically, in contrast to the well-known role of Rai14 in modulating the dynamics of F-actin at the ectoplasmic specialization (ES) junction in the testis, morphological changes of ES junction exhibited no differences between Rai14 KO and WT testes. Moreover, the F-actin surrounded at the ES junction was also comparable between the two groups.

CONCLUSION

In summary, our study demonstrates that Rai14 is dispensable for mouse spermatogenesis and fertility. Although the results of this study were negative, the phenotypic information obtained herein provide an enhanced understanding of the role of Rai14 in the testis, and researchers may refer to these results to avoid conducting redundant experiments.