Physical mapping of nine Xq translocation breakpoints and identification of XPNPEP2 as a premature ovarian failure candidate gene

Screening of premature ovarian insufficiency associated genes in Hungarian patients with next generation sequencing

BACKGROUND

Premature ovarian insuffiency (POI) is one of the main cause behind infertility. The genetic analysis of POI should be part of the clinical diagnostics, as several genes have been implicated in the genetic background of it. The aim of our study was to analyse the genetic background of POI in a Hungarian cohort.

METHODS

The age of onset was between 15 and 39 years. All patients had the 46,XX karyotype and they were prescreened for the most frequent POI associated FMR1 premutation. To identify genetic alterations next-generation sequencing (NGS) of 31 genes which were previously associated to POI were carried out in 48 unrelated patients from Hungary.

RESULTS

Monogenic defect was identified in 16.7% (8 of 48) and a potential genetic risk factor was found in 29.2% (14 of 48) and susceptible oligogenic effect was described in 12.5% (6 of 48) of women with POI using the customized targeted panel sequencing. The genetic analysis identified 8 heterozygous damaging and 4 potentially damaging variants in POI-associated genes. Further 10 potential genetic risk factors were detected in seven genes, from which EIF2B and GALT were the most frequent. These variants were related to 15 genes: AIRE, ATM, DACH2, DAZL, EIF2B2, EIF2B4, FMR1, GALT, GDF9, HS6ST2, LHCGR, NOBOX, POLG, USP9X and XPNPEP2. In six cases, two or three coexisting damaging mutations and risk variants were identified.

CONCLUSIONS

POI is characterized by heterogenous phenotypic features with complex genetic background that contains increasing number of genes. Deleterious variants, which were detected in our cohort, related to gonadal development (oogenesis and folliculogenesis), meiosis and DNA repair, hormonal signaling, immune function, and metabolism which were previously associated with the POI phenotype. This is the first genetic epidemiology study targeting POI associated genes in Hungary. The frequency of variants in different POI associated genes were similar to the literature, except EIF2B and GALT. Both of these genes potential risk factor were detected which could influence the phenotype, although it is unlikely that they can be responsible for the development of the disease by themselves. Advances of sequencing technologies make it possible to aid diagnostics of POI Since individual patients show high phenotypic variance because of the complex network controlling human folliculogenesis. Comprehensive NGS screening by widening the scope to genes which were previously linked to infertility may facilitate more accurate, quicker and cheaper genetic diagnoses for POI. The investigation of patient's genotype could support clinical decision-making process and pave the way for future clinical trials and therapies.

Current understanding of the genomic abnormities in premature ovarian failure: chance for early diagnosis and management

Premature ovarian failure (POF) is an insidious cause of female infertility and a devastating condition for women. POF also has a strong familial and heterogeneous genetic background. Management of POF is complicated by the variable etiology and presentation, which are generally characterized by abnormal hormone levels, gene instability and ovarian dysgenesis. To date, abnormal regulation associated with POF has been found in a small number of genes, including autosomal and sex chromosomal genes in folliculogenesis, granulosa cells, and oocytes. Due to the complex genomic contributions, ascertaining the exact causative mechanisms has been challenging in POF, and many pathogenic genomic characteristics have yet to be elucidated. However, emerging research has provided new insights into genomic variation in POF as well as novel etiological factors, pathogenic mechanisms and therapeutic intervention approaches. Meanwhile, scattered studies of transcriptional regulation revealed that ovarian cell function also depends on specific biomarker gene expression, which can influence protein activities, thus causing POF. In this review, we summarized the latest research and issues related to the genomic basis for POF and focused on insights gained from their biological effects and pathogenic mechanisms in POF. The present integrated studies of genomic variants, gene expression and related protein abnormalities were structured to establish the role of etiological genes associated with POF. In addition, we describe the design of some ongoing clinical trials that may suggest safe, feasible and effective approaches to improve the diagnosis and therapy of POF, such as Filgrastim, goserelin, resveratrol, natural plant antitoxin, Kuntai capsule et al. Understanding the candidate genomic characteristics in POF is beneficial for the early diagnosis of POF and provides appropriate methods for prevention and drug treatment. Additional efforts to clarify the POF genetic background are necessary and are beneficial for researchers and clinicians regarding genetic counseling and clinical practice. Taken together, recent genomic explorations have shown great potential to elucidate POF management in women and are stepping from the bench to the bedside.

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.

The Hypothesis of the Prolonged Cell Cycle in Turner Syndrome

Turner syndrome (TS) is a chromosomal disorder that is caused by a missing or structurally abnormal second sex chromosome. Subjects with TS are at an increased risk of developing intrauterine growth retardation, low birth weight, short stature, congenital heart diseases, infertility, obesity, dyslipidemia, hypertension, insulin resistance, type 2 diabetes mellitus, metabolic syndrome, and cardiovascular diseases (stroke and myocardial infarction). The underlying pathogenetic mechanism of TS is unknown. The assumption that X chromosome-linked gene haploinsufficiency is associated with the TS phenotype is questioned since such genes have not been identified. Thus, other pathogenic mechanisms have been suggested to explain this phenotype. Morphogenesis encompasses a series of events that includes cell division, the production of migratory precursors and their progeny, differentiation, programmed cell death, and integration into organs and systems. The precise control of the growth and differentiation of cells is essential for normal development. The cell cycle frequency and the number of proliferating cells are essential in cell growth. 45,X cells have a failure to proliferate at a normal rate, leading to a decreased cell number in a given tissue during organogenesis. A convergence of data indicates an association between a prolonged cell cycle and the phenotypical features in Turner syndrome. This review aims to examine old and new findings concerning the relationship between a prolonged cell cycle and TS phenotype. These studies reveal a diversity of phenotypic features in TS that could be explained by reduced cell proliferation. The implications of this hypothesis for our understanding of the TS phenotype and its pathogenesis are discussed. It is not surprising that 45,X monosomy leads to cellular growth pathway dysregulation with profound deleterious effects on both embryonic and later stages of development. The prolonged cell cycle could represent the beginning of the pathogenesis of TS, leading to a series of phenotypic consequences in embryonic/fetal, neonatal, pediatric, adolescence, and adulthood life.

Next Generation Sequencing Should Be Proposed to Every Woman With "Idiopathic" Primary Ovarian Insufficiency

Context

Primary ovarian insufficiency (POI) affects 1% of women under 40 years of age. POI is idiopathic in more than 70% of cases. Though many candidate genes have been identified in recent years, the prevalence and pathogenicity of abnormalities are still difficult to establish.

Objective

Our primary objective was to evaluate the prevalence of gene variations in a large prospective multicentric POI cohort. Our secondary objective was to evaluate the correlation between phenotype and genotype.

Methods

Two hundred and sixty-nine well-phenotyped POI patients were screened for variants of 18 known POI genes (BMP15, DMC1, EIF2S2, FIGLA, FOXL2, FSHR, GDF9, GPR3, HFM1, LHX8, MSH5, NOBOX, NR5A1, PGRMC1, STAG3, XPNPEP2, BHLB, and FSHB) by next generation sequencing (NGS). Abnormalities were classified as "variant" or "variant of unknown signification" (VUS) according to available functional tests or algorithms (SIFT, Polyphen-2, MutationTaster).

Results

One hundred and two patients (38%) were identified as having at least 1 genetic abnormality. Sixty-seven patients (25%) presented at least 1 variant. Forty-eight patients presented at least 1 VUS (18%). Thirteen patients (5%) had combined abnormalities. NOBOX variants were the most common gene variants involved in POI (9%). Interestingly, we saw no significant differences in the previous family history of POI, ethnic origin, age at onset of POI, primary amenorrhea, or secondary menstrual disturbances between the different genotypes.

Conclusion

In our study, a high percentage of patients presented gene variants detected by NGS analysis (38%). Every POI patient should undergo NGS analysis to improve medical cares of the patients.

Novel Complex Unbalanced Dicentric X-Autosome Rearrangement in a Thoroughbred Mare with a Mild Effect on the Phenotype

Complex structural X chromosome abnormalities are rare in humans and animals, and not recurrent. Yet, each case provides a fascinating opportunity to evaluate X chromosome content and functional status in relation to the effect on the phenotype. Here, we report the first equine case of a complex unbalanced X-autosome rearrangement in a healthy but short in stature Thoroughbred mare. Studies of about 200 cells by chromosome banding and FISH revealed an abnormal 2n = 63,X,der(X;16) karyotype with a large dicentric derivative chromosome (der). The der was comprised of normal Xp material, a palindromic duplication of Xq12q21, and a translocation of chromosome 16 to the inverted Xq12q21 segment by the centromere, whereas the distal Xq22q29 was deleted from the der. Microsatellite genotyping determined a paternal origin of the der. While there was no option to experimentally investigate the status of X chromosome inactivation (XCI), the observed mild phenotype of this case suggested the following scenario to retain an almost normal genetic balance: active normal X, inactivated X-portion of the der, but without XCI spreading into the translocated chromosome 16. Cases like this present unique resources to acquire information about species-specific features of X regulation and the role of X-linked genes in development, health, and disease.

Diminished Ovarian Reserve in Girls and Adolescents with Trisomy X Syndrome

An extra X chromosome occurs in ~ 1 in 1000 females, resulting in a karyotype 47,XXX also known as trisomy X syndrome (TXS). Women with TXS appear to be at increased risk for premature ovarian insufficiency; however, very little research on this relationship has been conducted. The objective of this case-control study is to compare ovarian function, as measured by anti-mullerian hormone (AMH) levels, between girls with TXS and controls. Serum AMH concentrations were compared between 15 females with TXS (median age 13.4 years) and 26 controls (median age 15.1 years). Females with TXS had significantly lower serum AMH compared to controls (0.7 ng/mL (IQR 0.2-1.7) vs 2.7 (IQR 1.3-4.8), p < 0.001). Additionally, girls with TXS were much more likely to have an AMH below the 2.5th percentile for age with 67% of them meeting these criteria (OR 11, 95% CI 2.3-42). Lower AMH concentrations in females with TXS may represent an increased risk for primary ovarian insufficiency in these patients and potentially a narrow window of opportunity to pursue fertility preservation options. Additional research is needed to understand the natural history of low AMH concentrations and future risk of premature ovarian insufficiency in girls with TXS.

Sex chromosomes-linked single-gene disorders involved in human infertility

Human infertility is a healthcare problem that has a worldwide impact. Genetic causes of human infertility include chromosomal aneuploidies and rearrangements and single-gene defects. The sex chromosomes (X and Y) are critical players in human fertility since they contain several genes essential for sex determination and reproductive traits for both men and women. This paper provides a review of the most common sex chromosomes-linked single-gene disorders involved in human infertility and their corresponding phenotypes. In addition to the Y-linked SRY gene, which mutations may cause XY gonadal dysgenesis and sex reversal, the deletions of genes present in AZF regions of the Y chromosome (DAZ, RBMY, DBY and USP9Y genes) are implicated in varying degrees of spermatogenic dysfunction. Furthermore, a list of X-linked genes (KAL1, NR0B1, AR, TEX11, FMR1, PGRMC1, BMP15 and POF1 and 2 regions genes (XPNPEP2, POF1B, DACH2, CHM and DIAPH2)) were reported to have critical roles in pubertal and reproductive deficiencies in humans, affecting only men, only women or both sexes. Mutations in these genes may be transmitted to the offspring by a dominant or a recessive inheritance.

A case of 46,XX dysgenesis and marked tall stature; the need for caution in interpreting array comparative genomic hybridization (CGH)

BACKGROUND

Gonadal dysgenesis with an apparently normal 46,XX karyotype is a rare cause of hypergonadotrophic hypogonadism. Tall stature is not a widely recognized association.

CASE REPORT

A 15-year-old girl presented with primary amenorrhoea. Examination showed a non-dysmorphic girl of normal intellect with no breast development (Tanner stage B1P4A1) who was tall compared with her parents: height standard deviation score (SDS) +1.56 vs. midparental height of +0.23 SDS, and slim build (weight -0.13 SDS). Investigations showed a 46,XX karyotype, elevated gonadotropins (FSH 119 and LH 33.7 IU/L), serum estradiol <5 pmol/L, uterine length 3.75 cm with cylindrical shape, and absent ovaries on ultrasound. Initially, a 364055-bp deletion on Xp21.2 was reported on array CGH. However, repeat analysis using BlueGnome CytoChip ISCA 4x180k v2.0 array was normal. With oral ethinyl estradiol induction puberty progressed to B4P4A2 but aged 18.4 years, the patient was remarkably tall with height SDS +2.88, weight SDS +0.97.

CONCLUSIONS

Caution is needed in interpreting small changes with array CGH, particularly with the older assays. We postulate that the genetic change causing 46,XX gonadal dysgenesis in our patient may have also resulted in unsuppressed somatic growth. More critical height assessment, including parental height measurement, of future patients with 46,XX gonadal dysgenesis is recommended in order to determine whether or not a true association with tall stature may be present in certain cases.

A fetal whole ovarian culture model for the evaluation of CrVI-induced developmental toxicity during germ cell nest breakdown

Prenatal exposure to endocrine disrupting chemicals (EDCs), including bisphenol A, dioxin, pesticides, and cigarette smoke, has been linked to several ovarian diseases such as premature ovarian failure (POF) and early menopause in women. Hexavalent chromium (CrVI), one of the more toxic heavy metals, is widely used in more than 50 industries. As one of the world's leading producers of Cr compounds, the U.S. is facing growing challenges in protecting human health against adverse effects of CrVI. Our recent findings demonstrated that in vivo CrVI exposure during gestational period caused POF in F1 offspring. Our current research focus is three-fold: (i) to identify the effect of CrVI on critical windows of great vulnerability of fetal ovarian development; (ii) to understand the molecular mechanism of CrVI-induced POF; (iii) to identify potential intervention strategies to mitigate or inhibit CrVI effects. In order to accomplish these goals we used a fetal whole ovarian culture system. Fetuses were removed from the normal pregnant rats on gestational day 13.5. Fetal ovaries were cultured in vitro for 12 days, and treated with or without 0.1 ppm potassium dichromate (CrVI) from culture day 2-8, which recapitulated embryonic day 14.5-20.5, in vivo. Results showed that CrVI increased germ cell/oocyte apoptosis by increasing caspase 3, BAX, p53 and PUMA; decreasing BCL2, BMP15, GDF9 and cKIT; and altering cell cycle regulatory genes and proteins. This model system may serve as a potential tool for high throughput testing of various drugs and/or EDCs in particular to assess developmental toxicity of the ovary.

Genetics of primary ovarian insufficiency: new developments and opportunities

BACKGROUND

Primary ovarian insufficiency (POI) is characterized by marked heterogeneity, but with a significant genetic contribution. Identifying exact causative genes has been challenging, with many discoveries not replicated. It is timely to take stock of the field, outlining the progress made, framing the controversies and anticipating future directions in elucidating the genetics of POI.

METHODS

A search for original articles published up to May 2015 was performed using PubMed and Google Scholar, identifying studies on the genetic etiology of POI. Studies were included if chromosomal analysis, candidate gene screening and a genome-wide study were conducted. Articles identified were restricted to English language full-text papers.

RESULTS

Chromosomal abnormalities have long been recognized as a frequent cause of POI, with a currently estimated prevalence of 10-13%. Using the traditional karyotype methodology, monosomy X, mosaicism, X chromosome deletions and rearrangements, X-autosome translocations, and isochromosomes have been detected. Based on candidate gene studies, single gene perturbations unequivocally having a deleterious effect in at least one population include Bone morphogenetic protein 15 (BMP15), Progesterone receptor membrane component 1 (PGRMC1), and Fragile X mental retardation 1 (FMR1) premutation on the X chromosome; Growth differentiation factor 9 (GDF9), Folliculogenesis specific bHLH transcription factor (FIGLA), Newborn ovary homeobox gene (NOBOX), Nuclear receptor subfamily 5, group A, member 1 (NR5A1) and Nanos homolog 3 (NANOS3) seem likely as well, but mostly being found in no more than 1-2% of a single population studied. Whole genome approaches have utilized genome-wide association studies (GWAS) to reveal loci not predicted on the basis of a candidate gene, but it remains difficult to locate causative genes and susceptible loci were not always replicated. Cytogenomic methods (array CGH) have identified other regions of interest but studies have not shown consistent results, the resolution of arrays has varied and replication is uncommon. Whole-exome sequencing in non-syndromic POI kindreds has only recently begun, revealing mutations in the Stromal antigen 3 (STAG3), Synaptonemal complex central element 1 (SYCE1), minichromosome maintenance complex component 8 and 9 (MCM8, MCM9) and ATP-dependent DNA helicase homolog (HFM1) genes. Given the slow progress in candidate-gene analysis and relatively small sample sizes available for GWAS, family-based whole exome and whole genome sequencing appear to be the most promising approaches for detecting potential genes responsible for POI.

CONCLUSION

Taken together, the cytogenetic, cytogenomic (array CGH) and exome sequencing approaches have revealed a genetic causation in ∼20-25% of POI cases. Uncovering the remainder of the causative genes will be facilitated not only by whole genome approaches involving larger cohorts in multiple populations but also incorporating environmental exposures and exploring signaling pathways in intragenic and intergenic regions that point to perturbations in regulatory genes and networks.

Risks associated with premature ovarian failure in Han Chinese women

In this retrospective study, the relationship between demographic characteristics, past medical history, general lifestyle habits and susceptibility of premature ovarian failure (POF) in Han Chinese population was investigated. Five hundred and fifty-three patients with POF and 400 women with normal ovarian function were recruited. A questionnaire was designed to gather information from responders. Logistic regression was carried out to calculate odds ratios (OR), 95% confidence intervals (95% CI) and P-values. History of pelvic surgery, mumps, having relatives with menstrual abnormalities and exposure to chemical agents were significantly associated with increased risk of POF (OR 5.53 [2.15 to 14.23]; 3.26 [2.38 to 4.47]; 28.12 [8.84 to 89.46]; 4.47 [2.09 to 9.58]). Vegetarian diet, tea and mineral water consumption reduced the risk of POF (OR 0.27 [0.19 to 0.37]; 0.04 [0.03 to 0.07]; 0.63 [0.47 to 0.85], respectively). Heredity, pelvic surgery, mumps and exposure to chemical agents were identified as risk factors for POF, whereas vegetarian diet, tea consumption and mineral water drinking were protective. Therefore, genetic consultation could help those women whose relatives manifested an early or premature menopause to avoid the consequences of possible premature ovarian function cessation. Avoidance of exposure to endocrine disrupters and flavonoids intake should be considered.

Identifying a novel role for X-prolyl aminopeptidase (Xpnpep) 2 in CrVI-induced adverse effects on germ cell nest breakdown and follicle development in rats

Environmental exposure to endocrine-disrupting chemicals (EDCs) is one cause of premature ovarian failure (POF). Hexavalent chromium (CrVI) is a heavy metal EDC widely used in more than 50 industries, including chrome plating, welding, wood processing, and tanneries. Recent data from U.S. Environmental Protection Agency indicate increased levels of Cr in drinking water from several American cities, which potentially predispose residents to various health problems. Recently, we demonstrated that gestational exposure to CrVI caused POF in F1 offspring. The current study was performed to identify the molecular mechanism behind CrVI-induced POF. Pregnant rats were treated with 25 ppm of potassium dichromate from Gestational Day (GD) 9.5 to GD 14.5 through drinking water, and the fetuses were exposed to CrVI through transplacental transfer. Ovaries were removed from the fetuses or pups on Embryonic Day (ED) 15.5, ED 17.5, Postnatal Day (PND) 1, PND 4, or PND 25, and various analyses were performed. Results showed that gestational exposure to CrVI: 1) increased germ cell/oocyte apoptosis and advanced germ cell nest (GCN) breakdown; 2) increased X-prolyl aminopeptidase (Xpnpep) 2, a POF marker in humans, during GCN breakdown; 3) decreased Xpnpep2 during postnatal follicle development; and 4) increased colocalization of Xpnpep2 with Col3 and Col4. We also found that Xpnpep2 inversely regulated the expression of Col1, Col3, and Col4 in all the developmental stages studied. Thus, CrVI advanced GCN breakdown and increased follicle atresia in F1 female progeny by targeting Xpnpep2.

Genetics of female infertility due to anomalies of the ovary and mullerian ducts

Genetic factors are pivotal in reproductive development and subsequent reproductive processes. If disturbed, infertility can occur. In the female, genetic factors affecting the ovary and the uterus are not uncommon causes of infertility. Terminal deletions on the X long arm and X short arm and X chromosomal mosaicism have long been accepted as causes of premature ovarian failure (POF). Responsible genes on the X have not yet elucidated. Attractive candidate genes for POF also exist on autosomes, and in over a dozen genes molecular perturbations are documented in non-syndromic POF. The most common single-gene cause of POF is premutation carriers for FMR1 (fragile X syndrome). As other candidate genes and additional ethnic groups are interrogated, the proportion of POF cases due to single-gene mutation will increase. Among uterine anomalies, incomplete mullerian fusion is most common. Increased recurrence risks for first-degree relatives confirm a role for genetic factors; interrogation of candidate genes is under way.

Turner syndrome masquerading as normal early puberty

Approximately 50% of patients with Turner syndrome (TS) have complete loss of one X chromosome, whereas the rest of the patients with TS display mosaicism or structural abnormalities of the X chromosome. Most well-known common features are short stature and gonadal failure. Approximately one third of girls with TS may enter spontaneous puberty, but only half those completed with menarche. However, some atypical features of TS have been described. Many studies have been conducted to verify and delineate proposed loci for genes pertaining to the TS phenotype, and correlations between karyotype and phenotype. A few rare cases of precocious puberty with TS have been described. Here we describe a case of TS with the Xp22.1 deletion presenting with short final stature, early normal onset of spontaneous puberty, and Graves' disease, without short stature during puberty.

Cytogenetic analysis of 179 Iranian women with premature ovarian failure

The importance of chromosomal abnormalities in etiology of premature ovarian failure (POF) is well known but in many cases, POF still remains idiopathic. We investigated the frequency and type of chromosomal aberrations in Iranian women diagnosed with idiopathic POF. Standard cytogenetic analysis was carried out in a total of 179 patients. Karyotype analysis of these patients revealed that 161 (89.95%) patients had normal female karyotype and 18 (10.05%) patients had abnormal karyotypes. The abnormal karyotypes included sex reverse sex determining region Y (SRY) negative (five Cases), X chromosome mosaicism (five cases), abnormal X chromosomes (three cases), abnormal autosomes (three cases) and X-autosome translocation (two cases). The overall prevalence of chromosomal abnormalities was 10.05% in this first large-scale report of chromosomal aberrations in Iranian women with POF. The results confirm previous observations and emphasis on the critical role of X chromosome abnormalities as one of the possible etiologies for POF.

Premature ovarian failure risk factors in an Iranian population

Background

The aim of this study was to determine possible correlates of premature ovarian failure (POF) in an Iranian population.

Methods

In a case-control study, 80 patients with POF were compared with 80 controls enrolled from the same setting during 2007–2008. A food diary was used to assess food consumption habits.

Results

Mean age of starting ovarian failure symptoms was 19.3 ± 5.7 years and mean age of menopause was 22.6 ± 6.3 years. Familial coincidence was observed in 16 POF patients versus no one in the control group (P < 0.05). POF patients had lower frequency of both eating red meat and fish when compared with controls (P < 0.001). POF and control subjects consumed similar amounts of dairy products, being 5.3 ± 3.2 times per week in POF and 5.6 ± 2.1 times in the control groups.

Conclusion

In this study, an association between POF and lower red meat or fish consumption was found.

Contemporary genetic technologies and female reproduction

BACKGROUND

The Fifth Evian Annual Reproduction (EVAR) Workshop Meeting discussed knowledge regarding contemporary genetics in female reproduction.

METHODS

Specialist reproductive medicine clinicians and geneticists delivered presentations based on published literature and current research. The content of this report is based on the expert presentations and subsequent group discussions that took place during this Workshop.

RESULTS

Numerous ovarian genes with a role in infertility have been identified. Future challenges for genetic screening of patients, such as those with polycystic ovary syndrome, primary ovarian insufficiency or endometriosis, include the identification of high-throughput strategies and how to apply these findings to infertile patients. The identification of high-quality embryos in IVF using objective technologies remains a high priority in order to facilitate single-embryo transfer. Gene expression profiling of cumulus cells surrounding the oocyte, and proteomic and metabolomic approaches in embryo culture media may significantly improve non-invasive embryo quality assessment.

CONCLUSIONS

The way forward in advancing the knowledge of genes involved in reproduction was considered to be through genome-wide association studies involving large numbers of patients. Establishing international collaboration is required to enable the application of such technologies in sufficient numbers of patients.

Sex-dependent and race-dependent association of XPNPEP2 C-2399A polymorphism with angiotensin-converting enzyme inhibitor-associated angioedema

BACKGROUND

Angioedema is a rare adverse effect of angiotensin-converting enzyme (ACE) inhibitors, which occurs more commonly in women and black Americans. Angioedema is thought to result from decreased degradation of vasoactive peptides. During ACE inhibition, bradykinin is primarily inactivated by aminopeptidase P (APP). Earlier studies have provided conflicting data with regard to serum APP activity in patients with a history of ACE inhibitor-associated angioedema. A single nucleotide polymorphism, -2399C>A (rs3788853, C-2399A), in XPNPEP2, the X-linked gene that encodes membranous APP, has been reported to associate with APP activity.

OBJECTIVE

To test the hypothesis that the relationship between XPNPEP2 C-2399A genotype and APP activity or ACE inhibitor-associated angioedema is sex-dependent and race-dependent.

METHODS

We compared C-2399A genotype frequencies in 169 cases with a history of ACE inhibitor-associated angioedema and 397 ACE inhibitor-exposed controls. Controls were prespecified to be 50% white, 50% black, and 50% women. Cases and controls were group matched for age and smoking.

RESULTS

XPNPEP2 C-2399A genotype associated with serum APP activity in both men and women. Serum APP activity was lower in men than in women, independent of genotype. XPNPEP2 -2399 A/ genotype was associated with an increased risk of angioedema in men [odds ratio 2.17 (1.09-4.32), P=0.03] in multivariate analysis. The A/ genotype was associated with angioedema in black men (P=0.03) but not in white men.

CONCLUSION

APP activity is lower in men and the XPNPEP2 C-2399A polymorphism associates with ACE inhibitor-associated angioedema in men but not women.

Variable expression of the Fragile X Mental Retardation 1 (FMR1) gene in patients with premature ovarian failure syndrome is not dependent on number of (CGG)n triplets in exon 1

BACKGROUND

Increased expression of the Fragile X Mental Retardation 1 (FMR1) gene in blood cells has been claimed to be associated with variable (CGG)(n) triplet numbers in the 5' untranslated region of this gene. Increased CGG triplet numbers, including that of the so-called premutation range (n= 55-200), were shown to have a risk of <26% to impair ovarian reserve leading to primary ovarian insufficiency and premature ovarian failure (POF).

METHODS

DNA and RNA samples were isolated from 74 patients with idiopathic POF to evaluate quantitatively the expression of FMR1 in leukocytes and CGG triplet number on FMR1 gene alleles. mRNA levels were normalized and compared with those of control women. Expression of the encoded protein (FMRP) was analysed by immunohistochemistry on ovarian biopsy tissue sections.

RESULTS

A large variance of the FMR1 transcript level was found in the leukocyte RNA samples, but only in patients with POF, and this variability did not correlate to variance of CGG triplet numbers found on both FMR1 alleles (19 < n > 90). During normal folliculogenesis, FMRP is predominantly expressed in granulosa cells.

CONCLUSIONS

Our data suggest that FMR1 expression during human folliculogenesis is probably a quantitative trait. Proper function of FMRP in granulosa cells seems to depend on an optimal transcript level. All women with CGG triplet numbers outside the range associated with normal folliculogenesis (26 < n > 34) are therefore expected to have a relaxed FMR1 transcription control. FMR1 transcript levels in leukocytes might therefore be diagnostic for altered FMRP levels in granulosa cells, which will affect the process of folliculogenesis.

Breakpoint determination of X;autosome balanced translocations in four patients with premature ovarian failure

Premature ovarian failure (POF) is a disorder characterized by amenorrhea and elevated serum gonadotropins before 40 years of age. As X chromosomal abnormalities are often recognized in POF patients, defects of X-linked gene may contribute to POF. Four cases of POF with t(X;autosome) were genetically analyzed. All the translocation breakpoints were determined at the nucleotide level. Interestingly, COL4A6 at Xq22.3 encoding collagen type IV alpha 6 was disrupted by the translocation in one case, but in the remaining three cases, breakpoints did not involve any X-linked genes. According to the breakpoint sequences, two translocations had microhomology of a few nucleotides and the other two showed insertion of 3-8 nucleotides with unknown origin, suggesting that non-homologous end-joining is related to the formation of all the translocations.

Analysis of X chromosome genomic DNA sequence copy number variation associated with premature ovarian failure (POF)

BACKGROUND

Premature ovarian failure (POF) is a heterogeneous disease defined as amenorrhoea for >6 months before age 40, with an FSH serum level >40 mIU/ml (menopausal levels). While there is a strong genetic association with POF, familial studies have also indicated that idiopathic POF may also be genetically linked. Conventional cytogenetic analyses have identified regions of the X chromosome that are strongly associated with ovarian function, as well as several POF candidate genes. Cryptic chromosome abnormalities that have been missed might be detected by array comparative genomic hybridization.

METHODS

In this study, samples from 42 idiopathic POF patients were subjected to a complete end-to-end X/Y chromosome tiling path array to achieve a detailed copy number variation (CNV) analysis of X chromosome involvement in POF. The arrays also contained a 1 Mb autosomal tiling path as a reference control. Quantitative PCR for selected genes contained within the CNVs was used to confirm the majority of the changes detected. The expression pattern of some of these genes in human tissue RNA was examined by reverse transcription (RT)-PCR.

RESULTS

A number of CNVs were identified on both Xp and Xq, with several being shared among the POF cases. Some CNVs fall within known polymorphic CNV regions, and others span previously identified POF candidate regions and genes.

CONCLUSIONS

The new data reported in this study reveal further discrete X chromosome intervals not previously associated with the disease and therefore implicate new clusters of candidate genes. Further studies will be required to elucidate their involvement in POF.

Aging of the human ovary and testis

Aging is associated with structural and functional alterations in all organs of the human body. The aging of gonads represents in this respect a special case, because these organs are not functional for the whole lifespan of an individual and their normal function is not indispensable for functions of the rest of the body. Ovarian function lasts for the reproductive life of a woman, i.e., from menarche until menopause. The testicular endocrine function, in contrast, begins already in utero, is interrupted between neonatal life and puberty, and continues thereafter along with spermatogenesis, with only slight decline, until old age. The aging processes of the ovary and testis are therefore very different. We describe in this review the structural and functional alterations in the human ovary and testis upon aging. Special emphasis will be given to clinically significant alterations, which in women concern the causes and consequences of the individual variability of fertility during the latter part of the reproductive age. The clinically important aspect of testicular aging entails the decline of androgen production in aging men.

The mutations and potential targets of the forkhead transcription factor FOXL2

Mutations of FOXL2, a gene encoding a forkhead transcription factor, have been shown to cause the blepharophimosis-ptosis-epicanthus inversus syndrome (BPES). This genetic disorder is characterized by eyelid and mild craniofacial abnormalities that can appear associated with premature ovarian failure. FOXL2 is one of the earliest ovarian markers and it offers, along with its targets, an excellent model to study ovarian development and function in normal and pathological conditions. In this review we summarize recent data concerning FOXL2, its mutations and its potential targets. Indeed, many mutations have been described in the coding sequence of FOXL2. Among them, polyalanine expansions and premature nonsense mutations have been shown to induce protein aggregation. In the context of the ovary, FOXL2 has been suggested to be involved in the regulation of cholesterol and steroid metabolism, apoptosis, reactive oxygen species detoxification and inflammation processes. The elucidation of the impact of FOXL2 mutations on its function will allow a better understanding of the pathogenic mechanisms underlying the BPES phenotype.

Recent advances in the study of genes involved in non-syndromic premature ovarian failure

Premature ovarian failure (POF) is a common pathology leading to infertility affecting about 1% of women under 40 years old. In POF patients, the ovarian dysfunction is characterized by the lack of the ovarian response to close a negative feedback loop on the synthesis of pituitary gonadotropins. Although the majority of cases are considered as idiopathic, diverse aetiologies have been associated, including genetic factors. Up to now, the potential genetic causes of non-syndromic POF have been established mainly by genetic linkage analysis of familial cases or by the screening of mutations in candidate genes based on animal models. Here, we review recent advances in the study of candidate genes.

ISWI chromatin remodeling in ovarian somatic and germ cells: revenge of the NURFs

Chromatin has emerged as an important regulator of gene expression, interposed between cell signaling pathways and transcriptional machinery. It participates in transmitting extra- and intra-cellular signals that coordinate ovarian events: ovarian follicle development, the meiotic maturation of the oocyte that precedes ovulation, and the ovulatory process and consequent luteinization. Recent evidence from model organisms and mammals suggests that chromatin signaling is achieved, in part, by imitation switch (ISWI) ATP-dependent chromatin-remodeling complexes. This review highlights a role for complexes containing the ISWI ATPase sucrose nonfermenting-2h (Snf2h) in proliferation in somatic and germ cells and also in meiosis in germ cells. Moreover, complexes containing the Snf2l ATPase dictate the differentiation of somatic cells and act in the induction of the terminal phases of meiosis in the oocyte.

Weight deficit at birth and Turner's syndrome

Turner's syndrome (TS) is one of the most frequent diseases accompanied by growth deficiency. Though developmental disorders have been observed in the fetal period, there has been disagreement as to whether short stature is frequent in newborn girls with Turner's syndrome. Hence we attempted to determine the incidence of 'small for gestational age' in TS compared with healthy newborns girls delivered at term above -2 SD (body length and weight) for gestational age. The medical records of 548 girls with TS recruited from Polish university and district hospitals were screened, with 468 of them delivered at term (gestational age > or =38 weeks) being included in this study. Mean weight (+/- SD) at birth was 2963 +/- 444 g, which was below the normal value for gestational age in nearly 90%. The mean birth weight deficiency was 600 g, but exceeded 1000 g in over 10%. When a newborn girl delivered at term has a marked weight deficit, Turner's syndrome should be considered. This is especially so when the girl is a product of a first pregnancy, when routine karyotyping is recommended. The condition may arise from a partial dysfunction of a gene or genes on the X-chromosome involved in the control of fetal growth.

Epigenetic control of the critical region for premature ovarian failure on autosomal genes translocated to the X chromosome: a hypothesis

Chromosomal rearrangements in Xq are frequently associated to premature ovarian failure (POF) and have contributed to define a POF "critical region" from Xq13.3 to Xq26. Search for X-linked genes responsible for the phenotype has been elusive as most rearrangements did not interrupt genes and many were mapped to gene deserts. We now report that ovary-expressed genes flanked autosomal breakpoints in four POF cases analyzed whose X chromosome breakpoints interrupted a gene poor region in Xq21, where no ovary-expressed candidate genes could be found. We also show that the global down regulation in the oocyte and up regulation in the ovary of X-linked genes compared to the autosomes is mainly due to genes in the POF "critical region". We thus propose that POF, in X;autosome balanced translocations, may not only be caused by haploinsufficiency, but also by a oocyte-specific position effect on autosomal genes, dependent on dosage compensation mechanisms operating on the active X chromosome in mammals.

L’insuffisance ovarienne prématurée

Premature ovarian failure (POF) is defined by at least four months of amenorrhea with elevated gonadotropins (usually above 40 UI/L) detected on two occasions a few weeks apart, in a woman before the age of 40. It occurs in 1 out of 10,000 in women below the age of 20, 1/1,000 below 30 and 1% in women before the age of 40. In 80% of POF cases, the etiology is unknown, except for Turner syndrome. The different etiologies identified are 1) iatrogenic following chemotherapy and/or radiotherapy, 2) autoimmune, 3) viral, 4) genetic (RFSH, FOXL2, FRAXA, BMP15, GDF9, GALT, 17 hydroxylase...). Management of these patients includes hormone replacement therapy in order to avoid an increase in cardiovascular risk and osteoporosis related to hypoestrogenism. Infertility is common, as only 3 to 10% of the patients will have natural conception. When fertility is desired, women with POF should be oriented towards oocyte donation centers. Research is currently performed in order to identify new genes involved in POF.

A Case of 46,X,der(X)t(X;X)(q22.1;p11) Xq22.1→Xqter in a 12-Year-Old Girl with Premature Ovarian Failure

Premature ovarian failure due to Xp duplication and Xq deletion has been reported in four patients, the youngest of whom was 18 years old. The diagnosis has been made with new techniques for genetic analysis, such as comparative genomic hybridization and fluorescence in situ hybridization. We report the youngest case (a 12-year-old who presented with irregular menses), of premature ovarian failure due to Xp duplication and Xq deletion and the first with 46,X,der(X)t(X;X)(q22.1;p11). The diagnosis was made using C-banding and fluorescent in situ hybridization with locus-specific probes. This case highlights the need to use advanced genetic strategies to determine karyotypic and phenotypic abnormalities.

Ectopic nucleolus organizer regions in a patient with premature ovarian failure

OBJECTIVE

To present a case of premature ovarian failure (POF) and a complex chromosomal rearrangement involving band Xq21.

DESIGN

Case report.

SETTING

Department of cytogenetics, general analysis laboratory.

PATIENT(S)

A woman with POF and a complex translocation involving chromosomes X and 2 and a nucleolus organizer region (NOR) structure inserted in the critical region Xq21.

INTERVENTION(S)

Chromosomal analysis, NOR banding, hysteroscopy.

MAIN OUTCOME MEASURE(S)

Fluorescence in situ hybridization, comparative genome hybridization, human androgen receptor gene technique.

RESULT(S)

Four mechanisms may explain a causal relationship between the phenotype of the patient and her chromosome constitution. The presence of a NOR structure at the breakpoint of chromosome X suggests a complex reorganization and is of interest per se.

CONCLUSION(S)

Cytogenetic analysis is essential in women with unexplained POF and may provide valuable information on the chromosome location of critical regions implicated in ovarian function. However, in very complex reorganizations such as that described herein, classical cytogenetic techniques must be combined with molecular techniques to achieve a more complete characterization of the anomaly.

Disruption of POF1B binding to nonmuscle actin filaments is associated with premature ovarian failure

Premature ovarian failure (POF) is characterized by elevated gonadotropins and amenorrhea in women aged <40 years. In a Lebanese family with five sisters who received the diagnosis of POF, we established linkage to the long arm of the X chromosome (between Xq21.1 and Xq21.3.3), using whole-genome SNP typing and homozygosity-by-descent mapping. By sequencing one candidate gene within that region, POF1B, we identified a point mutation localized in exon 10. This substitution of a nucleotide (G-->A), at position 1123, results in an arginine-->glutamine mutation of the protein sequence at position 329 (mutation R329Q). All the affected family members were homozygous for the mutation, whereas the unaffected members were heterozygous. Because POF1B shares high homology with the tail portion of the human myosin, we assessed the ability of both wild-type and mutant POF1B proteins to bind nonmuscle actin filaments in vitro. We found that the capacity of the mutant protein to bind nonmuscle actin filaments was diminished fourfold compared with the wild type, suggesting a function of POF1B in germ-cell division. Our study suggests that a homozygous point mutation in POF1B influences the pathogenesis of POF by altering POF1B binding to nonmuscle actin filaments.

X-linked premature ovarian failure: a complex disease

Involvement of the X chromosome in premature ovarian failure was demonstrated by the relatively frequent chromosomal rearrangements in patients, but the requirement of two X chromosomes for ovarian function was quite unexplained until recently. Review of the data on chromosomal rearrangements suggests that several genes along the X chromosomes contribute to ovarian function. In most instances, no single X chromosome gene has a causative role in premature ovarian failure, and the phenotype is likely to derive from the additive effect of X-linked and non-X-linked factors. Recent data on a small group of balanced X-autosome translocations showed that X-linked premature ovarian failure might also be caused by a different mechanism, namely position effect of the X chromosome on non-X-linked genes, and suggest a peculiar organization of the X chromosome during oogenesis.

Validation of growth charts for girls with Turner syndrome

Growth charts, which describe the natural course of growth in Turner syndrome (TS) patients, are commonly used in studies in lieu of control groups. While analysing data, various charts produce different final height estimations and height-gain predictions. The choice of an appropriate chart should be the first task when assessing effects of growth hormone treatment. The purpose of this study was to establish the most appropriate growth chart for the subsequent analysis of growth rate in the patients with TS observed initially for a short time without treatment in our clinic. We propose the criteria that a standardised chart should meet. The obtained height-standardised values (height standard deviation score -- Ht SDS) should represent normal distribution with a mean of 0 and standard deviation of 1; their initial mean value and mean change in these values during observation without treatment should not be different from 0. We studied 62 untreated girls with TS using three different growth charts. The values of Ht SDS based on the Lyon chart showed a significant difference from normal distribution (p < 0.05). Only the mean value of an initiaent from 0 (p = 0.088). The mean change of the Ht SDS value based on Lyon and Ranke charts during the follow-up period was not statistically different from 0 (p > 0.05), whereas the difference was statistically significant when the Wisniewski chart was used. Only the Ranke chart correctly characterised TS girls in our clinic. This analysis indicates the importance of careful selection of an appropriate growth chart for an observed population, before applying it to evaluate the effects of hormonal therapy.

Premature ovarian failure

Premature ovarian failure (POF) causing hypergonadotrophic hypogonadism occurs in 1% of women. In majority of cases the underlying cause is not identified. The known causes include: (a) Genetic aberrations, which could involve the X chromosome or autosomes. A large number of genes have been screened as candidates for causing POF; however, few clear causal mutations have been identified. (b) Autoimmune ovarian damage, as suggested by the observed association of POF with other autoimmune disorders. Anti-ovarian antibodies are reported in POF by several studies, but their specificity and pathogenic role are questionable. (c) Iatrogenic following surgical, radiotherapeutic or chemotherapeutic interventions as in malignancies. (d) Environmental factors like viral infections and toxins for whom no clear mechanism is known. The diagnosis is based on finding of amenorrhoea before age 40 associated with FSH levels in the menopausal range. Screening for associated autoimmune disorders and karyotyping, particularly in early onset disease, constitute part of the diagnostic work-up. There is no role of ovarian biopsy or ultrasound in making the diagnosis. Management essentially involves hormone replacement and infertility treatment, the only proven means for the latter being assisted conception with donated oocytes. Embryo cryopreservation, ovarian tissue cryopreservation and oocyte cryopreservation hold promise in cases where ovarian failure is foreseeable as in women undergoing cancer treatments.

A susceptibility gene for premature ovarian failure (POF) maps to proximal Xq28

Terminal deletions of the long arm of the human X chromosome have been described in women with premature ovarian failure (POF). We report here the molecular characterization of an inherited deletion in two affected women and in their mother. The two daughters presented secondary amenorrhea at 17 or 22 years respectively, while the mother was fertile. She had four children, but she eventually had premature menopause at 43 years of age. The fine molecular analysis of the deletion showed that the three women carried an identical deletion. We conclude that the phenotypic difference within the family must be attributed to genetic or environmental factors and not to the presence of different extent deletions. By comparison with other deletions in the region, we map a susceptibility gene for POF to 4.5 Mb, in the distal part of Xq.

Mutation analysis of two candidate genes for premature ovarian failure, DACH2 and POF1B

BACKGROUND

Balanced X;autosome translocations interrupting the 'critical region' of the long arm of the human X chromosome are often associated with premature ovarian failure (POF). However, the mechanisms leading to X-linked ovarian dysfunction are largely unknown, as the majority of the X chromosome breakpoints have been mapped to gene-free genomic regions. A few genes have been found to be interrupted, but their role has never been clarified.

METHODS AND RESULTS

By fine mapping of the X chromosome breakpoint of an X;autosome balanced translocation, we identified a new interrupted gene, POF1B. We performed a mutation analysis of POF1B and of another gene previously identified, DACH2, localized approximately 700 kb distal in Xq21, in a cohort of >200 Italian POF patients. Rare mutations were found in patients in both genes.

CONCLUSIONS

Our findings could not demonstrate any involvement of POF1B, but suggest that rare mutations in the DACH2 gene may have a role in the POF phenotype.

Premature ovarian failure and fragile X premutation: a study on 45 women

OBJECTIVE

The aim of this study was to test for the presence of the fragile X (FRAXA) premutation a group of women with early menopause.

STUDY DESIGN

45 women with idiopathic premature ovarian failure (POF), five with a familial and 40 with a sporadic form, were screened for the presence of FRAXA premutation. A control group of 28 women >45 years, with one or more children and no signs of POF, was also studied.

RESULTS

We found three cases of fragile X premutations in women all belonging to the group with sporadic POF.

CONCLUSION

Our results seems to confirm previous observations on the non random association between POF and FRAXA premutation.

Fertility, sex determination, and the X chromosome

Because of its function, the X chromosome has a special status in mammalian genomes, with the specific occurrence of genes that influence both female and male fertility. Long ago, the XO karyotype (Turner syndrome) was associated with infertility, proving the correlation between normal X chromosome dosage and normal female fertility. Nevertheless, the search for specific X-borne fertility genes was not completely successful and suggested, instead, that female X-linked fertility, for example, depends upon groups of X-linked genes. Conversely, X-linked hyperfertility has been observed in sheep, where a mutation in BMP15 leads to a hyperfertile phenotype, but only in the heterozygous state. Many male fertility genes map to the X chromosome, consistent with a genetic model developed in the early 1990s. Ironically, NR0B1 (formerly DAX1), once presented as the paradigm of genes responsible for ovarian development and function, is probably one of these male fertility factors and is active in the maintenance of spermatogenesis. Indeed, duplications of this gene on the human X chromosome lead to XY sex reversal, as NR0B1 is able to counterbalance the effect in humans. Nevertheless, invalidation experiments in mice demonstrate the effect of this factor on male germ-cell production.

Cell-surface peptidases

The cell surface has various functions: communicating with other cells, integrating into the tissue, and interacting with the extracellular matrix. Proteases play a key role in these processes. This review focuses on cell-surface peptidases (ectopeptidases, oligopeptidases) that are involved in the inactivation or activation of extracellular regulatory peptides, hormones, paracrine peptides, cytokines, and neuropeptides. The nomenclature of cell-surface peptidases is explained in relation to other proteases, and information is provided on membrane anchoring, catalytic sites, regulation, and, in particular, on their physiological and pharmacological importance. Furthermore, nonenzymatic (binding) functions and participation in intracellular signal transduction of cell surfaces peptidases are described. An overview on the different cell-surface peptidases is given, and their divergent functions are explained in detail. An example of actual pharmacological importance, dipeptidyl-peptidase IV (CD26), is discussed.

Ovarian differentiation and human embryo quality. 1. Molecular and morphogenetic homologies between oocytes and embryos in Drosophila, C. elegans, Xenopus and mammals

Knowledge on the formation of oocytes and follicles in Drosophila, C. elegans and Xenopus, and the genetic regulation of polarities and embryo growth, has been related to comparable data in mammalian oocytes and embryos. Initially, details of the nature of the regulatory processes in the non-mammals are described, with considerable attention being paid to the role of individual genes and their specific functions. The molecular genetic aspects of these developmental processes are discussed in detail. Attention then turns to mammals, to identify, describe and evaluate their homologies with the lower animals and flies. Several of these homologies are described, including genes regulating primary ovarian failure and various aspects of early embryonic growth. The polarized distribution of genes in mammalian oocytes and embyros is discussed, together with the implications in the form of differentiation in the early embryo. Morphogenetic systems operative during follicle maturation, fertilization and cleavage are described and related to similar processes in lower forms. These events include ooplasmic and pronuclear rotations, the form of ooplasmic inheritance in early blastomeres and the establishment of embryonic axes. Models of early mammalian development are considered.

Sex-specific gene expression during meiotic prophase I: Xlr (X linked, lymphocyte regulated), not its male homologue Xmr (Xlr related, meiosis regulated), is expressed in mouse oocytes

The Xmr (Xlr related, meiosis regulated) gene product is abundantly expressed in primary spermatocytes and is notably associated with nonrecombining segments of sex chromosomes in the XY body. Here we determined whether Xmr was expressed in meiotic oocytes. This was done by reverse transcription-polymerase chain reaction and cDNA sequencing, Western blot analysis, and immunocytochemistry. Unexpectedly, no Xmr message was detected in mouse fetal oocytes. Instead, Xlr (X linked, lymphocyte regulated), a closely related gene expressed in fetal thymus cells at the time of antigen-receptor gene rearrangement, was expressed in oocytes throughout meiotic prophase I. These findings indicate a sex-specific expression of two closely related members of the Xlr gene family during meiotic prophase I. The XLR protein may provide a useful marker for studies on chromatin condensation or DNA recombination in oocytes. In addition, because of the localization of the Xlr sequence family on the mouse X chromosome, the human equivalent of Xlr is a candidate gene for premature ovarian failure.

Genes and translocations involved in POF

Changes at a single autosomal locus and many X-linked loci have been implicated in women with gonadal dysgenesis [premature ovarian failure (POF) with deficits in ovarian follicles]. For the chromosome 3 locus, a forkhead transcription factor gene (FOXL2) has been identified, in which lesions result in decreased follicles by haploinsufficiency. In contrast, sporadic X; autosomal translocations are distributed at many points on the X, but concentrate in a critical region on Xq. The association of the breakpoints with genes involved in ovarian function is thus far weak (in four analyzed cases) and has not been related to pathology in other POF patients. While many more translocations can be analyzed in detail as the human genome sequence is refined, it remains possible that translocations like X monosomy (Turner syndrome) lead to POF not by interrupting specific genes important in ovarian development, but by causing aberrations in pairing or X-inactivation during folliculogenesis. It is noted that the critical region has unusual features, neighboring the X-inactivation center and including an 18 Mb region of very low recombination. These suggest that chromosome dynamics in the region may be sensitive to structural changes, and when modified by translocations might provoke apoptosis at meiotic checkpoints. Choices among models for the etiology of POF should be feasible based on studies of ovarian follicle development and attrition in mouse models. Studies would prominently include gene expression profiling of developmental-specific pathways in nascent ovaries with controlled levels of Foxl2 and interacting proteins, or with defined changes in the X chromosome.

Turner's syndrome in adulthood

Turner's syndrome is the most common chromosomal abnormality in females, affecting 1:2,500 live female births. It is a result of absence of an X chromosome or the presence of a structurally abnormal X chromosome. Its most consistent clinical features are short stature and ovarian failure. However, it is becoming increasingly evident that adults with Turner's syndrome are also susceptible to a range of disorders, including osteoporosis, hypothyroidism, and renal and gastrointestinal disease. Women with Turner's syndrome have a reduced life expectancy, and recent evidence suggests that this is due to an increased risk of aortic dissection and ischemic heart disease. Up until recently, women with Turner's syndrome did not have access to focused health care, and thus quality of life was reduced in a significant number of women. All adults with Turner's syndrome should therefore be followed up by a multidisciplinary team to improve life expectancy and reduce morbidity.

X/autosomal translocations in the Xq critical region associated with premature ovarian failure fall within and outside genes

Premature ovarian failure curtails female reproductive life and is often linked to balanced Xq/autosomal translocations in a critical region. We mapped regions around translocations at the edges of this zone (one in Xq13.3, two in Xq26) in large-insert clones and analyzed their sequence. One Xq26 region is extensively transcribed and, in agreement with a recent independent analysis, the breakpoint interrupts a gene that encodes a widely expressed peptidase. In contrast 430 kb around the second Xq26 breakpoint has no putative or detected gene content. In 260 kb around the Xq13 translocation, the breakpoint falls among a cluster of repetitive elements at least 59 kb from the only detected gene (a rarely expressed T-box family transcription factor). We discuss our results in relation to models that ascribe premature ovarian failure to interruption of ovarian genes or to a failure of interactions involving DNA of the critical region during follicle development.