FoxO3a eggs on fertility and aging

Bone Marrow-Derived Mesenchymal Stem Cells Reverse Radiotherapy-Induced Premature Ovarian Failure: Emphasis on Signal Integration of TGF-β, Wnt/β-Catenin and Hippo Pathways

Radiotherapy is an indispensable cancer treatment approach. However, it is associated with hazardous consequences on multiple organs characterized by insidious worsening severity over time. This study aimed to examine the potential therapeutic effects of bone marrow mesenchymal stem cells (BM-MSCs) in radiation-induced premature ovarian failure (POF). Exposing female rats to 3.2 Gy whole-body ϒ-rays successfully induced POF. One week later, a single intravenous injection of BM-MSCs (2*10⁶) cells was administered. BM-MSCs perfectly home to the damaged ovaries, enhanced ovarian follicle pool, and preserved the ovarian function manifested by restoring serum estradiol and follicle stimulating hormone levels, besides, rescuing the fertility outcomes of irradiated rats. These events have been associated with inhibiting ovarian apoptosis (Bax/Bcl2, caspase 3) and enhancing proliferation (PCNA). Interestingly, BM-MSCs reversed the inhibition of ovarian FOXO3 expression induced by radiation which resulted in increased primordial follicles stock. Moreover, BM-MSCs recovered the suppressed folliculogenesis process induced by radiation through upregulating FOXO1, GDF-9, and Fst genes expression accompanied by downregulating TGF-β which enhanced granulosa cells proliferation and secondary follicle development. Mechanistically, BM-MSCs miRNAs epigenetically upregulate Wnt/β-catenin and Hippo signaling pathways which are implicated in ovarian follicles growth and maturation. Therefore, BM-MSCs presented a ray of hope in the treatment of radiation-associated POF through genetic and epigenetic modulation of the integrated TGF-β, Wnt/β-catenin, and Hippo pathways which control apoptosis, proliferation, and differentiation of ovarian follicles.

Adiponectin Reduces Embryonic Loss Rate and Ameliorates Trophoblast Apoptosis in Early Pregnancy of Mice with Polycystic Ovary Syndrome by Affecting the AMPK/PI3K/Akt/FoxO3a Signaling Pathway

Reports in recent years have suggested that adiponectin (APN) improves insulin resistance and inhibits apoptosis by activating the AMP-activated protein kinase (AMPK) pathway and the PI3K/Akt signaling pathway after binding to its receptor. This study aims to explore the mechanism by which APN reduces embryo loss rate and trophoblast apoptosis in early pregnancy of mice with polycystic ovary syndrome (PCOS). PCOS mice were subcutaneously injected with APN (10 μg mg kg-1 day-1) on 11 consecutive days from the 3rd day of pregnancy onwards to observe the change of the embryo loss rate of PCOS mice induced by APN. Quantitative real-time PCR and Western blot were used to determine the relative expressions of mRNA and the proteins AMPK, PI3K, and Akt in mouse uterine tissue. At the same time, primary cultured mouse villous trophoblast cells were used to further explore the underlying mechanisms in vitro. APN significantly reduces the pregnancy loss rate of PCOS mice. At the same time, APN increases phosphorylation and mRNA expression levels of AMPK, PI3K, and Akt in PCOS mouse uterine tissue. In addition, trophoblast cells of model mice were treated with APN and inhibitors, and APN was found to reduce trophoblast cell apoptosis by affecting the phosphorylation levels of AMPK, PI3K, Akt, and FoxO3a proteins. APN reduces the embryo loss rate and ameliorates trophoblast apoptosis in PCOS mice by affecting the AMPK/PI3K/AKT/FoxO3a signaling pathway.

Expression Regulation and Physiological Role of Transcription Factor FOXO3a During Ovarian Follicular Development

In mammals, developing ovarian follicles transform from primordial follicles to primary follicles, secondary follicles, and mature follicles, accompanied by changes in follicular secretory functions. FoxO3a is a member of the forkhead transcription factor family (FoxO), which plays an important role in the cell cycle, DNA damage repair, apoptosis, oxidative stress, and energy metabolism. Recent studies have shown that FOXO3a is involved in the physiological regulation of follicular development and pathological progression of related ovarian diseases, which will provide useful concepts and strategies for retarding ovarian aging, prolonging the ovarian life span, and treating ovarian diseases. Therefore, the regulation of FOXO3a expression, as well as the physiological contribution during ovarian follicular development are detailed in this paper, presenting an important reference for the further study of ovarian biology.

Molecular characterization and expression analysis of foxo3l in response to exogenous hormones in black rockfish (Sebastes schlegelii)

As a crucial member of the Forkhead Box family, class O (FoxO) plays an essential role in growth, cell differentiation, metabolism, immunization, and apoptosis. Meanwhile, FoxO3 is the primary regulator and effective inhibitor of primordial follicle activation. In this study, seven foxo genes were identified in black rockfish (Sebastes schlegelii), including two foxo1 genes (foxo1a, foxo1b), two foxo3 genes (foxo3, foxo3l), one foxo4 gene, and two foxo6 genes (foxo6a, foxo6b). foxo3l was derived from teleost-specific whole-genome duplication events. Evaluation of tissue expression pattern revealed that foxo3l displayed sexually dimorphic expression with a high level in the ovary and spatial expression only in the cytoplasm of follicle cells and oocytes. When the ovaries were stimulated by estrogen and gonadotropin, foxo3l expression was remarkably reduced, and the effect of androgen was completely different. We considered that foxo3l lost its ability to inhibit follicular precocity because of mass ovulation by hormone stimulation, resulting in its decreased expression. Such evidence indicated that foxo3l is an important regulator of reproduction-related functions in black rockfish. This study provides new insights into foxo3l genes for further functional research in teleost.

Body mass index in relation to extracellular vesicle-linked microRNAs in human follicular fluid

OBJECTIVE

To study whether increased body mass index is associated with altered expression of extracellular vesicle microRNAs (EV-linked miRNAs) in human follicular fluid.

DESIGN

Cross-sectional study.

SETTING

Tertiary-care university-affiliated center.

PATIENT(S)

One hundred thirty-three women undergoing in vitro fertilization (IVF) were recruited from January 2014 to August 2016.

INTERVENTIONS(S)

None.

MAIN OUTCOME MEASURE(S)

EV-linked miRNAs were isolated from follicular fluid and their expression profiles were measured with the use of the Taqman Open Array Human miRNA panel. EV-linked miRNAs were globally normalized and inverse-normal transformed. Associations between body mass index (BMI) and EV-linked miRNA outcomes were analyzed by means of multivariate linear regression and principal component analysis.

RESULT(S)

Eighteen EV-linked miRNAs were associated with an increase in BMI after adjusting for age, ethnicity, smoking status, and batch effects. Hsa-miR-328 remained significant after false discovery rate adjustments. Principal component analyses identified the first principal component to account for 40% of the variation in our EV-linked miRNA dataset, and adjusted linear regression found that the first principal component was significantly associated with BMI after multiple testing adjustments. Using Kyoto Encyclopedia of Genes and Genomes enrichment analyses, we predicted gene targets of EV-linked miRNA in silico and identified PI3K-Akt signaling, ECM-receptor interaction, focal adhesion, FoxO signaling, and oocyte meiosis pathways.

CONCLUSION(S)

These results show that a 1-unit increase in BMI is associated with altered follicular fluid expression of EV-linked miRNAs that may influence follicular and oocyte developmental pathways. Our findings provide potential insight into a mechanistic explanation for the reduced fertility rates associated with increased BMI.

A way for in vitro/ex vivo egg production in mammals

Eggs are female germ cells that are required for producing offspring through sexual reproduction. In mammals, eggs are produced in the ovary and ovulated into the oviduct. It is well known that over 99% of eggs are degenerated without ovulation, so that many studies have attempted in vitro folliculogenesis to produce many eggs in different species for a few decades. Although many methods have been developed, a success of in vitro egg production with the resultant live birth of offspring has been limited, especially in livestock animals. More recently, we have succeeded in producing live pups derived from in vitro/ex vivo egg production in mice. This review aims to introduce our recent findings with a brief history of in vitro/ex vivo culture systems for follicles and ovaries.

Lower FOXO3 mRNA expression in granulosa cells is involved in unexplained infertility

AIM

The aim of this study was to investigate whether FOXO1 and FOXO3 mRNA expression in granulosa cells is the cause of unexplained infertility.

METHODS

Thirty-one patients aged <40 years (13 with unexplained infertility and 18 with male partner infertility as a control group) whose serum anti-Müllerian hormone level was >0.5 ng/μL were enrolled in the study. All patients underwent oocyte retrieval under a short protocol from June 2012 to October 2013. Real-time PCR was carried out using mRNA extracted from granulosa cells retrieved from mature follicles. We compared FOXO1 and FOXO3 mRNA expression ratios in granulosa cells between the unexplained infertility group and the male infertility group. The relation between FOXO1 and FOXO3 mRNA expression ratios in granulosa cells and assisted reproduction technology clinical outcome was also examined.

RESULTS

FOXO3 mRNA expression ratio was significantly lower in the unexplained infertility group than in the male infertility group. Moreover, FOXO3 mRNA expression ratio showed a positive correlation with both the number of retrieved oocytes and serum anti-Müllerian hormone level. A positive correlation was also identified between FOXO1 mRNA expression and total dose of hMG. As well, the number of retrieved oocytes in the unexplained infertility group was statistically lower than that in the male infertility group.

CONCLUSION

A lower FOXO3 mRNA expression in granulosa cells leads to poor oocyte development in patients with unexplained infertility undergoing controlled ovarian stimulation for in vitro fertilization-embryo transfer.

Transplantation of UC-MSCs on collagen scaffold activates follicles in dormant ovaries of POF patients with long history of infertility

Premature ovarian failure (POF) is a refractory disease for clinical treatment with the goal of restoring fertility. In this study, umbilical cord mesenchymal stem cells on a collagen scaffold (collagen/UC-MSCs) can activate primordial follicles in vitro via phosphorylation of FOXO3a and FOXO1. Transplantation of collagen/UC-MSCs to the ovaries of POF patients rescued overall ovarian function, evidenced by elevated estradiol concentrations, improved follicular development, and increased number of antral follicles. Successful clinical pregnancy was achieved in women with POF after transplantation of collagen/UC-MSCs or UC-MSCs. In summary, collagen/UC-MSC transplantation may provide an effective treatment for POF.

The role of the PI3K-Akt signaling pathway in the developmental competence of bovine oocytes

The ovarian follicle encloses oocytes in a microenvironment throughout their growth and acquisition of competence. Evidence suggests a dynamic interplay among follicular cells and oocytes, since they are constantly exchanging “messages”. We dissected bovine ovarian follicles and recovered follicular cells (FCs—granulosa and cumulus cells) and cumulus-oocyte complexes (COCs) to investigate whether the PI3K-Akt signaling pathway impacted oocyte quality. Following follicle rupture, COCs were individually selected for in vitro cultures to track the follicular cells based on oocyte competence to reach the blastocyst stage after parthenogenetic activation. Levels of PI3K-Akt signaling pathway components in FCs correlated with oocyte competence. This pathway is upregulated in FCs from follicles with high-quality oocytes that are able to reach the blastocyst stage, as indicated by decreased levels of PTEN and increased levels of the PTEN regulators bta-miR-494 and bta-miR-20a. Using PI3K-Akt responsive genes, we showed decreased FOXO3a levels and BAX levels in lower quality groups, indicating changes in cell cycle progression, oxidative response and apoptosis. Based on these results, the measurement of levels of PI3K-Akt pathway components in FCs from ovarian follicles carrying oocytes with distinct developmental competences is a useful tool to identify putative molecular pathways involved in the acquisition of oocyte competence.

Disorganization of the germ cell pool leads to primary ovarian insufficiency

The mammalian ovary is an organ that controls female germ cell development, storing them and releasing mature oocytes for transporting to the oviduct. During the fetal stage, female germ cells change from a proliferative state to meiosis before forming follicles with the potential for the growth of surrounding somatic cells. Understanding of molecular and physiological bases of germ cell development in the fetal ovary contributed not only to the elucidation of genetic disorders in primary ovarian insufficiency (POI), but also to the advancement of novel treatments for patients with POI. Accumulating evidence indicates that mutations in NOBOX, DAZL and FIGLAgenes are associated with POI. In addition, cell biology studies revealed the important roles of these genes as essential translational factors for germ cell development. Recent insights into the role of the PI3K (phosphatidylinositol 3-kinase)-Akt signaling pathway in primordial follicle activation allowed the development of a new infertility treatment, IVA (in vitro activation), leading to successful pregnancy/delivery in POI patients. Furthermore, elucidation of genetic dynamics underlying female germ cell development could allow regeneration of oocytes from ES (embryonic stem)/iPS (induced pluripotent stem) cells in mammals. The purpose of this review is to summarize basic findings related to female germ cell development and potential clinical implications, especially focusing on POI etiologies. We also summarize evolving new POI therapies based on IVA as well as oocyte regeneration.

Transcriptional profiling of five isolated size-matched stages of human preantral follicles

Little is known of the early stages of human follicular development and the complex processes that regulate follicular growth. To identify genes of potential importance, we analysed follicle-related transcripts in five populations of isolated size-matched human preantral follicles by microarray analysis. Oocyte-specific genes were found to be the most abundant and differentially expressed transcripts and included germ cell transcription factors LHX8 and SOHLH2 which were significantly down-regulated during preantral follicle development. Differentially expressed genes also included transcription factors of NOTCH signalling, IGF2, orphan nuclear receptor LRH-1, and homeobox gene HOXA7, indicating potentially important regulatory roles for these genes during early human folliculogenesis. We also found that FSHR mRNA and protein were present in the earliest stages of preantral follicles, whereas LHR was absent. In conclusion, our data identify specific oocyte and somatic genes in small human follicles that impact early follicle growth, and provide foundation for further analysis of the signalling pathways involved in early human folliculogenesis.

Genome-wide association studies of age at menarche and age at natural menopause

Genome-wide association studies (GWAS) have been successful in uncovering genetic determinants of age at menarche and age at natural menopause. To date, more than 30 novel genetic loci have been identified in GWAS for age at menarche and 17 for age at natural menopause. These findings have stimulated a plethora of follow-up studies particularly with respect to the functional characterization of these novel loci and how these results can be translated into risk prediction. However, the genetic loci identified so far account for only a small fraction of the overall heritability. This review provides an overview of the current state of our knowledge of the genetic basis of menarche and menopause timing. It emphasizes recent GWAS results and outlines strategies for discovering the missing heritability and strategies to further our understanding of the underlying molecular mechanisms of the observed genetic associations.

High fat diet induced obesity alters ovarian phosphatidylinositol-3 kinase signaling gene expression

Insulin regulates ovarian phosphatidylinositol-3-kinase (PI3 K) signaling, important for primordial follicle viability and growth activation. This study investigated diet-induced obesity impacts on: (1) insulin receptor (Insr) and insulin receptor substrate 1 (Irs1); (2) PI3K components (Kit ligand (Kitlg), kit (c-Kit), protein kinase B alpha (Akt1) and forkhead transcription factor subfamily 3 (Foxo3a)); (3) xenobiotic biotransformation (microsomal epoxide hydrolase (Ephx1), Cytochrome P450 isoform 2E1 (Cyp2e1), Glutathione S-transferase (Gst) isoforms mu (Gstm) and pi (Gstp)) and (4) microRNA's 184, 205, 103 and 21 gene expression. INSR, GSTM and GSTP protein levels were also measured. Obese mouse ovaries had decreased Irs1, Foxo3a, Cyp2e1, MiR-103, and MiR-21 but increased Kitlg, Akt1, and miR-184 levels relative to lean littermates. These results support that diet-induced obesity potentially impairs ovarian function through aberrant gene expression.

The ovarian reserve in mammals: a functional and evolutionary perspective

The constitution and the control of the ovarian reserve is of importance in mammals and women. In particular, the number of primordial follicles at puberty is positively correlated with the number of growing follicles and their response to gonadotropin treatments. The size of this ovarian reserve depends on genes involved in germ cell proliferation and differentiation, sexual differentiation, meiosis, germ cell degeneration, formation of primordial follicles, and on a potential mechanism of self-renewal of germ stem cells. In this review, we present the state of the art of the knowledge of genes and factors involved in all these processes. We first focus on the almost 70 genes identified mainly by mouse invalidation models, then we discuss the most plausible hypothesis concerning the possibility of the existence of germ cell self-renewal by neo-oogenesis in animal species and human, with a special interest for the role of corresponding genes in evolutionary distinct model species. All of the genes pointed out here are candidates susceptible to explain fertility defects such as the premature ovarian failure in human.

Forkhead family transcription factor FoxO and neural differentiation

The Forkhead Box subgroup O (FoxO) transcription factor family is one of the most important downstream targets of the phosphatidylinositol 3-kinase/protein kinase B signaling pathway playing an important role in many biological functions including transcriptional regulation of cellular differentiation. Neuronal differentiation is a complex process which involves many signaling pathways and molecular mechanisms. Interestingly, recent studies indicate that the FoxO family is involved in a number of signaling pathways regulating cell differentiation. The actions occur at different stages in the differentiation process and by differing mechanisms. This review will focus on FoxO as a novel transcription factor in neural differentiation.

Relative expression of genes encoding SMAD signal transduction factors in human granulosa cells is correlated with oocyte quality

PURPOSE

To determine the expression of SMAD transcripts in human granulosa cells.

METHODS

Luteinized mural granulosa cells were harvested from forty women undergoing oocyte retrieval, and RNAs were isolated. SMAD expression levels were determined by polymerase chain reaction (PCR) and quantitative real-time PCR (q-RTPCR).

RESULTS

SMAD1-7 and 9 are expressed in human granulosa cells, with SMAD2, 3 and 4 showing the highest expression levels. Peak estradiol (E2) levels correlated with the number of oocytes retrieved during IVF. Oocyte number showed no correlation with SMAD expression levels or ratios. Fertilization rates also did not correlate with the expression levels of individual SMADs, but did correlate with higher SMAD4:SMAD3 ratios (p = 0.0062) and trended with SMAD4:SMAD2 (p = 0.0698).

CONCLUSIONS

SMAD transcripts are differently expressed in human granulosa cells, where they may mediate TGF-beta superfamily signaling during folliculogenesis and ovulation. Further, the relative expression ratios of SMAD2, 3 and 4 may differentially affect fertilization rate.

FOXO3 knockdown accelerates development of bovine primordial follicles

The objective of the present study was to elucidate the involvement of FOXO3 in the activation of bovine primordial follicles. In immunohistochemistry, FOXO3 was detected in all of the oocytes in primordial and primary follicles. The FOXO3 decreased after treatment with FOXO3 small interfering RNAs (siRNAs). Ovarian tissues containing dominantly primordial follicles were treated with FOXO3 siRNAs and then xenografted to severe combined immune deficiency (SCID) mice. Two months after xenografting, some primordial follicles developed to the secondary and tertiary stages, and the total percentage of these developing follicles (secondary and tertiary follicles: 18 ± 7%) was higher than in the control grafts treated with control siRNA (7 ± 1%). It is thought that bovine primordial follicle activation is regulated by the FOXO3-dependent mechanism and that knockdown of FOXO3 induces the release of primordial follicles from FOXO3 suppression, initiating their growth.

Knockdown of FOXO3 induces primordial oocyte activation in pigs

Mammalian ovaries are endowed with a large number of primordial follicles, each containing a nongrowing oocyte. Only a small population of primordial oocytes (oocytes in primordial follicles) is activated to enter the growth phase throughout a female's reproductive life. Little is known about the mechanism regulating the activation of primordial oocytes. Here, we found that the primordial oocytes from infant pigs (10- to 20-day-old) grew to full size at 2 months after xenografting to immunodeficient mice, whereas those from prepubertal pigs (6-month-old) survived without initiation of their growth even after 4 months; thereafter, they started to grow and reached full size after 6 months. These results suggest that the mechanism regulating the activation of primordial oocytes in prepubertal pigs is different from that in infant pigs. In this regard, the involvement of FOXO3, a forkhead transcription factor, was studied. In prepubertal pigs, FOXO3 was detected in almost all (94±2%) primordial oocyte nuclei, and in infant pigs, 42±7% primordial oocytes were FOXO3 positive. At 4 months after xenografting, the percentage of FOXO3-positive primordial oocytes from prepubertal pigs had decreased to the infant level. Further, siRNA was designed to knock down porcine FOXO3. FOXO3-knockdown primordial follicles from prepubertal pigs developed to the antral stage accompanied by oocyte growth at 2 months after xenografting. These results suggest that primordial oocytes are dormant in prepubertal pigs by a FOXO3-related mechanism to establish a nongrowing oocyte pool in the ovary, and that a transient knockdown of the FOXO3 activates the primordial oocytes to enter the growth phase.

Contraception targets in Mammalian ovarian development

In the human ovary, early in pre-natal life, oocytes are surrounded by pre-granulosa follicular cells to form primordial follicles. These primordial oocytes remain dormant, often for decades, until recruited into the growing pool throughout a woman's adult reproductive years. Activation of follicle growth and subsequent development of growing oocytes in pre-antral follicles are major biological checkpoints that determine an individual females reproductive potential. In the past decade, great strides have been made in the elucidation of the molecular and cellular mechanisms underpinning maintenance of the quiescent primordial follicle pool and initiation and development of follicle growth. Gaining an in-depth knowledge of the intracellular signalling systems that control oocyte preservation and follicle activation has significant implications for improving female reproductive productivity and alleviating infertility. It also has application in domestic animal husbandry, feral animal population control and contraception in women.

The mammalian ovary from genesis to revelation

Two major functions of the mammalian ovary are the production of germ cells (oocytes), which allow continuation of the species, and the generation of bioactive molecules, primarily steroids (mainly estrogens and progestins) and peptide growth factors, which are critical for ovarian function, regulation of the hypothalamic-pituitary-ovarian axis, and development of secondary sex characteristics. The female germline is created during embryogenesis when the precursors of primordial germ cells differentiate from somatic lineages of the embryo and take a unique route to reach the urogenital ridge. This undifferentiated gonad will differentiate along a female pathway, and the newly formed oocytes will proliferate and subsequently enter meiosis. At this point, the oocyte has two alternative fates: die, a common destiny of millions of oocytes, or be fertilized, a fate of at most approximately 100 oocytes, depending on the species. At every step from germline development and ovary formation to oogenesis and ovarian development and differentiation, there are coordinated interactions of hundreds of proteins and small RNAs. These studies have helped reproductive biologists to understand not only the normal functioning of the ovary but also the pathophysiology and genetics of diseases such as infertility and ovarian cancer. Over the last two decades, parallel progress has been made in the assisted reproductive technology clinic including better hormonal preparations, prenatal genetic testing, and optimal oocyte and embryo analysis and cryopreservation. Clearly, we have learned much about the mammalian ovary and manipulating its most important cargo, the oocyte, since the birth of Louise Brown over 30 yr ago.

Role of neurotrophic factors in early ovarian development

Much is known about the endocrine hormonal mechanisms controlling ovarian development. More recently, attention has focused on identifying regulatory pathways that, operating within the ovarian microenvironment, contribute to the acquisition of ovarian reproductive competence. Within this framework, the concept has developed that neurotrophins (NTs) and their Trk tyrosine kinase receptors, long thought to be exclusively required for the development of the nervous system, are also involved in the control of ovarian maturation. The ovary of several species, including rodents, sheep, cows, nonhuman primates, and humans, produce NTs and express both the high-affinity receptors and the common p75 (NTR) receptor required for signaling. Studies in humans and rodents have shown that this expression is initiated during fetal life, before the formation of primordial follicles. Gene targeting approaches have identified TrkB, the high-affinity receptor for neurotrophin-4/5 and brain-derived neurotrophic factor, as a signaling module required for follicular assembly, early follicular growth, and oocyte survival. A similar approach has shown that nerve growth factor contributes independently to the growth of primordial follicles into gonadotropin-responsive structures. Altogether, these observations indicate that NTs are important contributors to the gonadotropin-independent process underlying the formation and initiation of ovarian follicular growth.

Awakening the oocyte: controlling primordial follicle development

Oocytes are sequestered in primordial follicles before birth and remain quiescent in the ovary, often for decades, until recruited into the growing pool throughout the reproductive years. Therefore, activation of follicle growth is a major biological checkpoint that controls female reproductive potential. However, we are only just beginning to elucidate the cellular mechanisms required for either maintenance of the quiescent primordial follicle pool or initiation of follicle growth. Understanding the intracellular signalling systems that control oocyte maintenance and activation has significant implications for improving female reproductive productivity and longevity in mammals, and has application in domestic animal husbandry, feral animal population control and infertility in women.

Expression of forkhead transcription factors in human granulosa cells

Members of the forkhead box O1 (FOXO) family of transcription factors are expressed in granulosa cells during various stages of follicle development, and evidence from rodent and other model systems suggests that they may be involved in regulating follicular activation and oocyte maturation. In this report, we show that FOXO1, FOXO3, and FOXO4 are expressed in human luteinized mural granulosa cells, which may suggest that these transcription factors are also involved in human folliculogenesis and luteinization.

Genetic correlates of longevity and selected age-related phenotypes: a genome-wide association study in the Framingham Study

BACKGROUND

Family studies and heritability estimates provide evidence for a genetic contribution to variation in the human life span.

METHODS

We conducted a genome wide association study (Affymetrix 100K SNP GeneChip) for longevity-related traits in a community-based sample. We report on 5 longevity and aging traits in up to 1345 Framingham Study participants from 330 families. Multivariable-adjusted residuals were computed using appropriate models (Cox proportional hazards, logistic, or linear regression) and the residuals from these models were used to test for association with qualifying SNPs (70, 987 autosomal SNPs with genotypic call rate > or =80%, minor allele frequency > or =10%, Hardy-Weinberg test p > or = 0.001).

RESULTS

In family-based association test (FBAT) models, 8 SNPs in two regions approximately 500 kb apart on chromosome 1 (physical positions 73,091,610 and 73, 527,652) were associated with age at death (p-value < 10(-5)). The two sets of SNPs were in high linkage disequilibrium (minimum r2 = 0.58). The top 30 SNPs for generalized estimating equation (GEE) tests of association with age at death included rs10507486 (p = 0.0001) and rs4943794 (p = 0.0002), SNPs intronic to FOXO1A, a gene implicated in lifespan extension in animal models. FBAT models identified 7 SNPs and GEE models identified 9 SNPs associated with both age at death and morbidity-free survival at age 65 including rs2374983 near PON1. In the analysis of selected candidate genes, SNP associations (FBAT or GEE p-value < 0.01) were identified for age at death in or near the following genes: FOXO1A, GAPDH, KL, LEPR, PON1, PSEN1, SOD2, and WRN. Top ranked SNP associations in the GEE model for age at natural menopause included rs6910534 (p = 0.00003) near FOXO3a and rs3751591 (p = 0.00006) in CYP19A1. Results of all longevity phenotype-genotype associations for all autosomal SNPs are web posted at http://www.ncbi.nlm.nih.gov/projects/gap/cgi-bin/study.cgi?id=phs000007 webcite.

CONCLUSION

Longevity and aging traits are associated with SNPs on the Affymetrix 100K GeneChip. None of the associations achieved genome-wide significance. These data generate hypotheses and serve as a resource for replication as more genes and biologic pathways are proposed as contributing to longevity and healthy aging.

Infertility caused by retardation of follicular development in mice with oocyte-specific expression of Foxo3a

In recent years, mammalian oocytes have been proposed to have important roles in the orchestration of ovarian follicular development and fertility. To determine whether intra-oocyte Foxo3a, a component of the phosphatidylinositol 3-kinase (PI3K) signaling pathway, influences follicular development and female fertility, a transgenic mouse model was generated with constitutively active Foxo3a expressed in oocytes. We found that the female transgenic mice were infertile, which was caused by retarded oocyte growth and follicular development, and anovulation. Further mechanistic studies revealed that the constitutively active Foxo3a in oocytes caused a dramatic reduction in the expression of bone morphogenic protein 15 (Bmp15), connexin 37 and connexin 43, which are important molecules for the establishment of paracrine and gap junction communications in follicles. Foxo3a was also found to facilitate the nuclear localization of p27(kip1) in oocytes, a cyclin-dependent kinase (Cdk) inhibitor that may serve to inhibit oocyte growth. The results from the current study indicate that Foxo3a is an important intra-oocyte signaling molecule that negatively regulates oocyte growth and follicular development. Our study may therefore give some insight into oocyte-borne genetic aberrations that cause defects in follicular development and anovulation in human diseases, such as premature ovarian failure.

Identification of a tumour suppressor network opposing nuclear Akt function

The proto-oncogene AKT (also known as PKB) is activated in many human cancers, mostly owing to loss of the PTEN tumour suppressor. In such tumours, AKT becomes enriched at cell membranes where it is activated by phosphorylation. Yet many targets inhibited by phosphorylated AKT (for example, the FOXO transcription factors) are nuclear; it has remained unclear how relevant nuclear phosphorylated AKT (pAKT) function is for tumorigenesis. Here we show that the PMLtumour suppressor prevents cancer by inactivating pAKT inside the nucleus. We find in a mouse model that Pml loss markedly accelerates tumour onset, incidence and progression in Pten-heterozygous mutants, and leads to female sterility with features that recapitulate the phenotype of Foxo3a knockout mice. We show that Pml deficiency on its own leads to tumorigenesis in the prostate, a tissue that is exquisitely sensitive to pAkt levels, and demonstrate that Pml specifically recruits the Akt phosphatase PP2a as well as pAkt into Pml nuclear bodies. Notably, we find that Pml-null cells are impaired in PP2a phosphatase activity towards Akt, and thus accumulate nuclear pAkt. As a consequence, the progressive reduction in Pml dose leads to inactivation of Foxo3a-mediated transcription of proapoptotic Bim and the cell cycle inhibitor p27(kip1). Our results demonstrate that Pml orchestrates a nuclear tumour suppressor network for inactivation of nuclear pAkt, and thus highlight the importance of AKT compartmentalization in human cancer pathogenesis and treatment.

Ovarian aging and menopause: current theories, hypotheses, and research models

Aging of the reproductive system has been studied in numerous vertebrate species. Although there are wide variations in reproductive strategies and hormone cycle components, many of the fundamental changes that occur during aging are similar. Evolutionary hypotheses attempt to explain why menopause occurs, whereas cellular hypotheses attempt to explain how it occurs. It is commonly believed that a disruption in the hypothalamic-pituitary-gonadal axis is responsible for the onset of menopause. Data exist to demonstrate that the first signs of menopause occur at the level of the brain or the ovary. Thus, finding an appropriate and representative animal model is especially important for the advancement of menopause research. In primates, there is a gradual decline in the function of the hypothalamic-pituitary-gonadal (HPG) axis ultimately resulting in irregularities in menstrual cycles and increasingly sporadic incidence of ovulation. Rodents also exhibit a progressive deterioration in HPG axis function; however, they also experience a period of constant estrus accompanied by intermittent ovulations, reduced progesterone levels, and elevated circulating estradiol levels. It is remarkable to observe that females of other classes also demonstrate deterioration in HPG axis function and ovarian failure. Comparisons of aging in various taxa provide insight into fundamental biological mechanisms of aging that could underlie reproductive decline.

Activation of Akt (PKB) and suppression of FKHRL1 in mouse and rat oocytes by stem cell factor during follicular activation and development

Although communications between mammalian oocytes and their surrounding granulosa cells mediated by the Kit-Kit ligand (KL, or stem cell factor, SCF) system have been proven to be crucial for follicular development, Kit downstream signaling pathways in mammalian oocytes are largely unknown. In this study, by using ovaries and isolated oocytes from postnatal mice and rats, we demonstrated for the first time that components of the PI3 kinase pathway, the serine/threonine kinase Akt (PKB) which enhances cellular proliferation and survival, and an Akt substrate FKHRL1 which is a transcription factor that leads to apoptosis and cell cycle arrest, are expressed in mammalian oocytes. By using an in vitro oocytes culture system, we found that oocytes-derived Akt and FKHRL1 are regulated by SCF. Treatment of cultured oocytes with SCF cannot only rapidly phosphorylate and activate Akt, but also simultaneously phosphorylate and may therefore functionally suppress FKHRL1, through the action of PI3 kinase. Together with our in situ hybridization and immunohistochemistry data that Akt and FKHRL1 are mostly expressed in oocytes in primordial and primary ovaries and reports that FKHRL1 gene-deficient mice exhibited excessive activation from primordial to primary follicles as well as enlarged oocyte sizes, we suppose that in mammalian oocytes, actions of granulosa cell derived SCF on primordial to primary follicle transition and subsequent follicle development may involve activation of Akt and inhibition of FKHRL1 activities in oocytes. The role of oocyte's Akt may be to enhance follicle development and the role of oocyte's FKHRL1 may be to inhibit follicle development. We propose that the cascade from granulosa cell SCF to oocyte Kit-PI3 kinase-Akt-FKHRL1 may play an important role to regulate the growth rate of mammalian oocytes and hypothetically also the oocyte secretion of factors that may regulate the activation and early development of ovarian follicles.