Analysis of the origin of Turner's syndrome using polymorphic DNA probes

Transplantation of human umbilical cord mesenchymal stem cells to treat premature ovarian failure

As one of the problems and diseases for women before 40 years, premature ovarian failure (POF) could be characterized by amenorrhea, low estrogen levels, infertility, high gonadotropin levels, and lack of mature follicles. Causes of the disease involve some genetic disorders, autoimmunity diseases, and environmental factors. Various approaches have been employed to treat POF, however with limited success. Today, stem cells are used to treat POF, since they have the potential to self-repair and regenerate, and are effective in treating ovarian failure and infertility. As mesenchymal stem cell (MSC) could simultaneously activate several mechanisms, many researchers consider MSC transplantation to be the best and most effective approach in cell therapy. A good source for mesenchymal stem cells is human umbilical cord (HUCMSC). Animal models with cyclophosphamide are required for stem cell treatment and performance of HUCMSC transplantation. Stem cell therapy could indicate the levels of ovarian markers and follicle-stimulating hormone receptor. It also increases ovarian weight, plasma E2 levels, and the amount of standard follicles. Herein, the causes of POF, effective treatment strategies, and the effect of HUCMSC transplantation for the treatment of premature ovarian failure are reviewed. Many studies have been conducted in this field, and the results have shown that stem cell treatment is an effective approach to treat infertility.

Genetics of Primary Ovarian Insufficiency

The diagnosis of primary ovarian insufficiency (POI) has untold effects on women and a better understanding alongside potential treatments are paramount to improve quality of life of these women. Various causes have been linked to the development of POI with genetics playing a key role. A better understanding of the genetics of POI could lead to earlier diagnosis and broaden fertility options. This chapter discusses previously known and more recently discovered genes that have been implicated in the development of POI. It explores the varying phenotypic expressions of some genes in different populations and areas for further research in the genetics of POI.

Epigenetics in Turner syndrome

Background

Monosomy of the X chromosome is the most frequent genetic abnormality in human as it is present in approximately 2% of all conceptions, although 99% of these embryos are spontaneously miscarried. In postnatal life, clinical features of Turner syndrome may include typical dysmorphic stigmata, short stature, sexual infantilism, and renal, cardiac, skeletal, endocrine and metabolic abnormalities.

Main text

Turner syndrome is due to a partial or total loss of the second sexual chromosome, resulting in the development of highly variable clinical features. This phenotype may not merely be due to genomic imbalance from deleted genes but may also result from additive influences on associated genes within a given gene network, with an altered regulation of gene expression triggered by the absence of the second sex chromosome. Current studies in human and mouse models have demonstrated that this chromosomal abnormality leads to epigenetic changes, including differential DNA methylation in specific groups of downstream target genes in pathways associated with several clinical and metabolic features, mostly on autosomal chromosomes. In this article, we begin exploring the potential involvement of both genetic and epigenetic factors in the origin of X chromosome monosomy. We review the dispute between the meiotic and post-zygotic origins of 45,X monosomy, by mainly analyzing the findings from several studies that compare gene expression of the 45,X monosomy to their euploid and/or 47,XXX trisomic cell counterparts on peripheral blood mononuclear cells, amniotic fluid, human fibroblast cells, and induced pluripotent human cell lines. From these studies, a profile of epigenetic changes seems to emerge in response to chromosomal imbalance. An interesting finding of all these studies is that methylation-based and expression-based pathway analyses are complementary, rather than overlapping, and are correlated with the clinical picture displayed by TS subjects.

Conclusions

The clarification of these possible causal pathways may have future implications in increasing the life expectancy of these patients and may provide informative targets for early pharmaceutical intervention.

Cytogenetic analysis of the retained products of conception after missed abortion following blastocyst transfer: a retrospective, large-scale, single-centre study

Cytogenetic analysis of the retained products of conception (POC) is the most effective test for identifying miscarriage causes. However, there has been no large-scale study limited to blastocyst transfer. This study retrospectively reports the findings of 1030 cases in which POC analysis was performed after missed abortion following single blastocyst transfer performed at the Shinbashi Yume Clinic. We identified 19.4% as normal karyotypes and 80.6% as aneuploid. These cases broke down into: 62.3% trisomy; 7.8% double trisomy; 0.5% triple or quadruple trisomy; 1.3% monosomy 21; 3.2% monosomy X; 0.1% 47,XXY; 1.0% polyploidy; 1.0% mixed; 1.1% embryonic mosaicism; and 2.4% structural anomalies. In samples with normal karyotypes, 49.5% were female while 50.5% were male. The occurrence of trisomy and double trisomy were both significantly more frequent in the ≥38 years group than in the ≤37 years group (P < 0.01). Trisomy was significantly more frequently associated with fetal heartbeat (P < 0.01); double trisomy, polyploidy and normal karyotype were significantly more frequent with no fetal heartbeat (P < 0.01). There was no significant difference in the frequency of chromosomal abnormalities between the number of miscarriages or blastocyst quality. Thus, POC cytogenetic testing is highly valuable for ascertaining the cause of miscarriage.

Perspectives in Pediatric Pathology, Chapter 5. Gonadal Dysgenesis

One of the most challenging areas in pediatric testicular pathology is the appropriate understanding and pathological diagnosis of disorders of sexual development (DSD), and in particular, the issue of gonadal dysgenesis. Here we present the main concepts necessary for their understanding and appropriate classification, with extensive genetic correlations.

Development of mammalian ovary

Pre-natal and early post-natal ovarian development has become a field of increasing importance over recent years. The full effects of perturbations of ovarian development on adult fertility, through environmental changes or genetic anomalies, are only now being truly appreciated. Mitigation of these perturbations requires an understanding of the processes involved in the development of the ovary. Herein, we review some recent findings from mice, sheep, and cattle on the key events involved in ovarian development. We discuss the key process of germ cell migration, ovigerous cord formation, meiosis, and follicle formation and activation. We also review the key contributions of mesonephric cells to ovarian development and propose roles for these cells. Finally, we discuss polycystic ovary syndrome, premature ovarian failure, and pre-natal undernutrition; three key areas in which perturbations to ovarian development appear to have major effects on post-natal fertility.

Effect of the parental origin of the X-chromosome on the clinical features, associated complications, the two-year-response to growth hormone (rhGH) and the biochemical profile in patients with turner syndrome

Background

It is possible that genes on the X chromosome are expressed differently depending of its parental origin. The objective of this study was to determine the influence of the parental origin of the X-chromosome on phenotypic variability, response to rhGH and on the biochemical profile of TS patients.

Methods

This was a cross-sectional multicenter correlational study carried out over three years in six Latin-American university hospitals. Unrelated 45,X TS patients (n =  93; 18.3 ± 8.5 years )) were evaluated. A subgroup (n =  34) of the patients were prospectively treated with rhGH over two years. DNA profiles of patients and their mothers were compared to determine the parental origin of the retained X-chromosome through 10 polymorphic X-chromosome-STRs. The association with clinical features, biochemical profiles and anthropometric data at the beginning and after two years of rhGH treatment was determined.

Results

Seventy two percent of patients retained the maternal X chromosome (Xm). A trend towards significance between maternal height and patients final height (p ≤ 0.07) in 45,Xm subjects was observed. There was no correlation between paternal height and patient height. No differences were detected between both groups in regard to dysmorphic features, classical malformations or increase in the height-SDS after rhGH. There were higher levels of triglycerides, total and LDL cholesterol in patients >20 years who retained the Xm.

Conclusions

The parental origin of the retained X chromosome may influence lipid metabolism in TS patients, but its effect on growth seems to be minimal. No parental-origin-effect on the phenotypic features, associated anomalies and on the growth response to rhGH was found in 45,X TS individuals.

Chromosomal abnormalities & oxidative stress in women with premature ovarian failure (POF)

Background & objectives:

Premature ovarian failure (POF) is defined as the cessation of ovarian function under the age of 40 yr and is characterized by amenorrhoea, hypoestrogenism and elevated serum gonadotrophin levels. The cause of POF remains undetermined in majority of the cases. This study was aimed to investigate the type and frequency of cytogenetic abnormalities in patients with idiopathic POF and also to study the role of oxidative stress in such cases.

Methods:

Seventy five women with idiopathic POF were included in this study. Chromosome analysis was done in peripheral blood lymphocytes by conventional GTG banding to identify numerical or structural abnormalities. Cytogenetically normal cases were investigated for reactive oxygen species (ROS) levels in their blood by luminol-chemiluminescence assay.

Results:

Eighteen chromosomal anomalies were identified in POF patients (24%). Majority of the cases were found to have X-chromosome abnormalities (28%). Overall median ROS range was found to be significantly higher (P<0.01) in POF patients [50480 (120,132966) RLU/min] compared to controls [340 (120,5094) RLU/min]. Among these, 50 per cent of the POF patients had higher ROS levels, 20 per cent had medium elevation and 30 per cent were found to have normal values comparable to controls.

Interpretation & conclusions:

X-chromosome anomalies were found to be the major contributor of POF. Oxidative stress may be the underlying aetiology in idiopathic premature ovarian failure. Thus the results of this study highlight the role of cytogenetic abnormalities and supraphysiological levels of ROS in causation of idiopathic POF. But the role of oxidative stress needs to be confirmed by other studies on patients from different geographical areas and from different ethnicities.

Pathogenesis and causes of premature ovarian failure: an update

Premature ovarian failure (POF) affects 1% of young women. This condition has significant psychological sequelae and major health implications. POF seriously interferes with fertility and family planning. Diverse etiologies are associated with POF. Literature review related to the causes and pathogenesis of POF, cited between the year 1900 and May 2010. POF may be either spontaneous or induced. The known causes include: Genetic disorders, which could involve the X chromosome or autosomes. However, the growing body of literature demonstrates a list of newly discovered mutations that may be responsible for causing POF. Most of these mutations are extremely rare, and most cases of POF are still considered to be idiopathic.Autoimmune causes; there is some evidence of an association of POF with lymphocytic oophoritis and other autoimmune disorders. Antiovarian antibodies are reported in POF, but their specificity and pathogenic role are obscure.Iatrogenic causes; chemotherapy, radiotherapy and pelvic surgery can lead to POF.Infectious Causes; some viral and microbial infections can be followed by POF.Environmental toxins, such as cigarette smoking are reported as risk factors of spontaneous POF.Idiopathic; in most cases, no identifiable etiology can be recognized after complete evaluation.

Genetically modified mouse models for premature ovarian failure (POF)

Premature ovarian failure (POF) is a complex disorder that affects approximately 1% of women. POF is characterized by the depletion of functional ovarian follicles before the age of 40 years, and clinically, patients may present with primary amenorrhea or secondary amenorrhea. Although some genes have been hypothesized to be candidates responsible for POF, the etiology of most of the cases is idiopathic, with the underlying causes still unidentified because of the heterogeneity of the disease. In this review, we consider some mutant mouse models that exhibit phenotypes which are comparable to human POF, and we suggest that the use of these mouse models may help us to gain a better understanding of the molecular mechanisms underlying POF in humans.

Aetiology of premature ovarian failure

Premature ovarian failure (POF) is the occurrence of hypergonadotropic hypoestrogenic amenorrhoea in women under the age of 40 years. POF is idiopathic in 74–90% of cases but can be familial (4–33%) or sporadic. The known causes are: genetic aberrations; autoimmune ovarian damage; iatrogenic following surgery, radiotherapy or chemotherapy; environmental factors (viruses, toxins, etc.); and metabolic (galactosaemia, 17 OH deficiency, etc.) Genetic aberrations could involve the X chromosome (monosomy, trisomy or translocations) or be autosomal. Genetic mechanisms include reduced gene dosage and non-specific chromosome effect impairing meiosis, decreasing the pool of primordial follicles and increasing atresia due to apoptosis or failure of follicle maturation. The genes for POF-1 are localized to Xq 21.3–Xq27 and for POF-2 to Xq13.3–21.1. The FMR1 gene is responsible for the fragile X syndrome. It occurs due to CGG expansion of more than 55 repeats at the 5′UTR (Xq 27.3), which is associated with gene silence resulting in mental retardation in males, and POF in female carriers. Autoimmune ovarian damage is caused by the alteration of T-cell subsets and T-cell-mediated injury, increase of autoantibody producing B-cells and a low number of effector supressor/cytotoxic lymphocyte and a decrease of number and activity of natural killer cells. POF can be associated with other non-endocrine and endocrine diseases. The mutations of AIRE gene are responsible for polyendocrinopathies (APS I–III). As the cause of POF is unknown in the majority of cases and the number of women with POF is increasing, the primary goal of scientific groups worldwide should be focused on the study of the aetiology of POF.

Paternally derived der(7)t(Y;7)(p11.1 approximately 11.2;p22.3)dn in a mosaic case with Turner syndrome

An unusual mosaic karyotype was detected in a 6-year-old female patient with clinical diagnosis of Turner syndrome (TS). Cytogenetic and molecular cytogenetic studies revealed besides a cell line with 45,X a second cell line where the short arm of the Y-chromosome was translocated onto the short arm of a chromosome 7; karyotype: 45,X,der(7)t(Y;7)(p11.1 approximately 11.2;p22.3)/45,X. To delineate the mechanisms of rearrangement and karyotypic evolution in this case, further studies were performed. A maternal origin of the X-chromosome and biparental origin of both chromosomes 7 were determined by microsatellite analysis. Furthermore, using parental-origin-determination fluorescence in situ hybridization (pod-FISH) it could be established that the derivative chromosome 7 was of paternal origin. Overall, this is to the best of our knowledge the first report of such a complex mosaic TS karyotype.

Falência ovariana prematura: aspectos atuais

A falência ovariana prematura (FOP) acomete aproximadamente 1:1000 mulheres antes dos 30 anos, 1:250 em torno dos 35 anos e de 1:100 aos 40 anos. Manifesta-se como amenorréia primária ou amenorréia secundária, não podendo ser considerada definitiva em todas as pacientes, uma vez que a concepção espontânea pode ocorrer em até 5-10% das FOP. Na maioria dos casos apresenta-se na forma esporádica, pois apenas 5% apresentam história familial. Entre as causas conhecidas estão as alterações cromossômicas, dos genes ligados ao cromossomo X e cromossomos autossômicos, doenças autoimunes, alterações tóxicas e iatrogênicas. Com relativa freqüência, a causa etiológica não é obtida, sendo então denominada de idiopática. O diagnóstico da FOP é feito baseado na história clínica e níveis elevados do hormônio folículo estimulante (FSH), sendo posteriormente investigadas as causas mais específicas. O manejo clínico visa o suporte emocional, o tratamento hormonal com estrogênios e progestogênios, a abordagem da infertilidade e a prevenção de co-morbidades como a osteoporose e potencial maior risco cardiovascular.

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.

Parental origin of normal X chromosomes in Turner syndrome patients with various karyotypes: implications for the mechanism leading to generation of a 45,X karyotype

The parental origin of the X chromosome of 45,X females has been the subject of many studies, and most of them have shown that the majority (60-80%) of the X chromosomes are maternal in origin. However, studies on the parental origin of normal X chromosomes are relatively limited for Turner syndrome (TS) females with sex chromosome aberrations. In this study, we used PCR-based typing of highly polymorphic markers and an assay of methylation status of the androgen receptor gene to determine the parental origin of normal X chromosomes in 50 unbiased TS females with a variety of karyotypes. Our results showed a higher paternal meiotic error rate leading to the generation of abnormal sex chromosomes, especially in the case of del(Xp) and abnormal Y chromosomes. Isochromosome Xq and ring/marker X chromosomes, on the other hand, were equally likely the result of both maternal and paternal meiotic errors. A thorough review of previous results, together with our data suggests, that the majority of TS karyotype are caused by paternal meiotic errors that generate abnormal sex chromosomes, and that most 45,X cells are generated by mitotic loss of these abnormal sex chromosomes, resulting in maternal X dominance in these cells.

Microsatellite analysis in Turner syndrome: parental origin of X chromosomes and possible mechanism of formation of abnormal chromosomes

Turner syndrome is a chromosomal disorder in which all or part of one X chromosome is missing. The meiotic or mitotic origin of most cases remains unknown due to the difficulty in detecting hidden mosaicism and to the lack of meiotic segregation studies. We analyzed 15 Turner patients, 10 with a 45,X whereas the rest had a second cell line with abnormal X-chromosomes: a pseudodicentric, an isochromosome, one large and one small ring, and the last with a long arm deletion. Our aims were: to detect X cryptic mosaicism in patients with a 45,X constitution; to determine the parental origin of the abnormality; to infer the zygotic origin of the karyotype and to suggest the timing and mechanism of the error(s) leading to the formation of abnormal X chromosomes from maternal origin. Molecular investigation did not revealed heterozygosity for any microsatellite, excluding X mosaicism in the 45,X cases. Parental origin of the single X chromosome was maternal in 90% of these patients. Three of the structurally abnormal Xs were maternally derived whereas the other two were paternal. These results allowed us to corroborate breakpoints in these abnormal X chromosomes and suggest that the pseudodicentric chromosome originated from post-zygotic sister chromatid exchange, whereas the Xq deleted chromosome probably arose after a recombination event during maternal meiosis.

Lack of expression of XIST from a small ring X chromosome containing the XIST locus in a girl with short stature, facial dysmorphism and developmental delay

A 46,X,r(X) karyotype was found in a three and a half year old girl with short stature, facial dysmorphism and developmental delay. The clinical findings were consistent with the phenotype described in a limited number of patients with small ring X chromosomes lacking the XIST locus, a critical player in the process of X chromosome inactivation. Surprisingly, in our patient, fluorescent in situ hybridisation demonstrated that the XIST locus was present on the ring X. However, expression studies showed that there was no XIST transcript in peripheral blood cells, suggesting that the ring X had not been inactivated. This was confirmed by the demonstration that both of the patient's alleles for the androgen receptor gene were unmethylated, and that both of the patient's ZXDA alleles were expressed. The active nature of the ring X would presumably result in overexpression of genes that may account for the developmental delay observed for the patient. Using polymorphic markers along the X chromosome, the ring X was determined to be of paternal origin with one breakpoint in the long arm between DXS8037 and XIST and one in the short arm in Xp11.2 between DXS1126 and DXS991. To attempt to determine why the XIST gene failed to be expressed, the promoter region was sequenced and found to have a base change at the same location as a variant previously associated with nonrandom X chromosome inactivation. This mutation was not seen in over one hundred normal X chromosomes examined; however, it was observed in the paternal grandmother who did not show substantial skewing of X chromosome inactivation.

Ovarian differentiation and gonadal failure

Ovarian failure can result from several different genetic mechanisms-X chromosomal abnormalities, autosomal recessive genes causing various types of XX gonadal dysgenesis, and autosomal dominant genes. The number and precise location of loci on the X are still under investigation, but it is clear that, in aggregate, these genes are responsible for ovarian maintenance, given that monosomy X shows germ cells that undergo accelerated atresia. Despite recent hypotheses, at present there is no evidence for a gene directing primary ovarian differentiation; this process may be constitutive. Phenotypic/karyotypic correlation and limited molecular confirmation have long shown that proximal Xp and proximal Xq contain regions of the most importance to ovarian maintenance. Terminal deletions at Xp11 result in 50% primary amenorrhea and 50% premature ovarian failure or fertility. Deletions at Xq13 usually produce primary amenorrhea. Terminal deletions nearer the telomeres on either Xp of Xq bring about premature ovarian failure more often than complete ovarian failure. The X-linked zinc finger gene (ZFX) and diaphanous 2 Drosophila homologue (DIAPH2) are the only candidate genes for ovarian maintenance that map to the X chromosome. Additional, as yet unidentified, genes along the X chromosome must be involved. The search for these genes in humans is hampered by the lack of candidate genes that map to the X chromosome, the scarcity of patients with fortuitous autosomal translocations, and small pedigrees, which hinder mapping of the loci. In addition, difficulties with human germ cell research also make it challenging to dissect genes important to ovarian development. Autosomal genes also are involved in ovarian differentiation and gonadal failure. Follicle-stimulating hormone receptor and ataxia telangiectasia are examples of autosomal genes known to cause human ovarian failure. Transgenic mouse models point to many other candidate autosomal genes, and sequencing of the human homologues in affected women should lead to the discovery of new genes responsible for human ovarian failure. Identification, functional analysis, and mapping of novel genes specifically expressed in the ovary of mice and women eventually should lead to fruitful dissection of essential genes in mammalian ovarian development and maintenance.

Retarded postimplantation development of X0 mouse embryos: impact of the parental origin of the monosomic X chromosome

About 12-17% of the embryos obtained by mating mice carrying the In(X)1H or Paf mutations are of the 39,X (X0) genotype. Depending on the mutant mice used for mating, the monosomic X chromosome can be inherited from the paternal (XP) or the maternal (XM) parent. The XP0 embryos display developmental retardation at gastrulation and early organogenesis. XP0 embryos also display poor development of the ectoplacental cone, which is significantly smaller in size and contains fewer trophoblasts than XX siblings. In contrast, XM0 embryos develop normally and are indistinguishable from XX littermates. In both types of X0 embryos, an X-linked lacZ transgene is expressed in nearly all cells in both the embryonic and the extraembryonic tissues, suggesting that X inactivation does not occur when only one X is present. Of particular significance is the maintenance of an active XP chromosome in the extraembryonic tissues where normally the paternal X chromosome is preferentially inactivated in XX embryos. The differential impact of the inheritance of X chromosomes from different parents on the development of the X0 embryos raises the possibility that the XP is less capable than the XM in providing the appropriate dosage of X-linked activity that is necessary to support normal development of the embryo and the ectoplacental cone. Alternatively, the development of the XP0 embryo may be compromised by the lack of activity of one or several X-linked genes which are expressed only from the maternal X chromosome. Without the activity of these genes, embryonic development may be curtailed even though all other loci on the XP chromosome are actively transcribed.

Prenatal and postnatal prevalence of Turner's syndrome: a registry study

OBJECTIVE

To study prevalence of Turner's syndrome in Denmark and to assess validity of prenatal diagnosis.

DESIGN

Study of data on prenatal and postnatal Turner's syndrome in Danish Cytogenetic Central Register.

SUBJECTS

All registered Turner's syndrome karyotypes (100 prenatal cases and 215 postnatal cases) during 1970-93.

MAIN OUTCOME MEASURES

Prevalence of Turner's syndrome karyotypes among prenatally tested fetuses and Turner's syndrome among liveborn infants.

RESULTS

Among infant girls, prevalence of Turner's syndrome was 32/100,000. Among female fetuses tested by amniocentesis, prevalence of Turner's syndrome karyotypes was 176/100,000 (relative risk of syndrome, 6.74 compared with prevalence among untested pregnancies). Among female fetuses tested by chorion villus sampling, prevalence of syndrome karyotypes was 392/100,000 (relative risk, 16.8). We excluded prenatal tests referred because of results of ultrasound scanning: among fetuses tested by amniocentesis revised relative risk was 5.68, while revised relative risk among fetuses tested by chorion villus sampling was 13.3. For 29 fetuses with prenatal diagnosis of possible Turner's syndrome, pregnancy was allowed to continue and 24 children were live born. Thirteen of these children were karyotyped postnatally, and diagnosis of Turner's syndrome had to be revised for eight, seven being normal girls and one boy. This gives tentative predictive value of amniocentesis in diagnosing Turner's syndrome of between 21% and 67%. There was no significant relation between mother's age and risk of Turner's syndrome.

CONCLUSIONS

Discrepancy between prenatal and postnatal prevalence of Turner's syndrome challenges specificity of prenatal examination in diagnosing Turner's syndrome.

Parental origin of the X chromosome, X chromosome mosaicism and screening for "hidden" Y chromosome in 45,X Turner syndrome ascertained cytogenetically

Our study confirms the finding that about 85% of X chromosomes in Turner girls are maternally derived. A new observation is the detection of a high frequency of mosaicism (15%) in Turner girls who by cytogenetic analysis were thought to have a pure 45,X karyotype. DNA examination of the material was done by hybridization with digoxigenin labelled, non-radioactive probes, and PCR products for microsatellite analysis were run on polyacrylamide gels. We screened for the presence of "hidden" Y chromosome mosaicism, using the primers SRY, ZFY, DYZ3, DYZ1 and DYS132. Contrary to other reports using the PCR technique to unravel "hidden" Y chromosome mosaics, we did not find any positive cases. A precise technical protocol for these new techniques is given, and the advantages are discussed.

Turner syndrome and female sex chromosome aberrations: deduction of the principal factors involved in the development of clinical features

Although clinical features in Turner syndrome have been well defined, underlying genetic factors have not been clarified. To deduce the factors leading to the development of clinical features, we took the following four steps: (1) assessment of clinical features in classic 45,X Turner syndrome; (2) review of clinical features in various female sex chromosome aberrations (karyotype-phenotype correlations); (3) assessment of factors that could lead to Turner features; and (4) correlation of the clinical features with the effects of specific factors. The results indicate that the clinical features in 45,X and in other female sex chromosome aberrations may primarily be determined by: (1) degree of global non-specific developmental defects caused by quantitative alteration of a euchromatic or non-inactivated region; (2) dosage effect of a pseudoautosomal growth gene(s), a Y-specific growth gene(s), and an Xp-Yp homologous lymphogenic gene(s); and (3) degree of chromosome pairing failure in meiocytes that are destined to develop as oocytes in the absence of SRY. 1991; Grumbach and Conte 1992). However, the pertinent factors have not been determined to date. The method to clarify the factors responsible for the development of the Turner phenotype can be broken down into the following steps: (1) assessment of clinical features in classic 45,X Turner syndrome; (2) review of clinical features in various female sex chromosome aberrations (karyotype-phenotype correlations); (3) assessment of factors that could lead to Turner features; and (4) correlation of the clinical features with the effects of specific factors. If the clinical features in 45,X and in other female sex chromosome aberrations are explained by the effects of specific factors, it can be said that such factors contribute to the development of Turner features. In this paper, we take each of the above steps, and propose the principal factors involved in the development of clinical features in Turner syndrome.

Isochromosome 15q of maternal origin in two Prader-Willi syndrome patients previously diagnosed erroneously as cytogenetic deletions

Since our previous report on two Prader-Willi syndrome (PWS) patients with t(15q;15q) (Niikawa and Ishikiriyama; Hum Genet 69:22-27, 1985) was erroneous, we report here new data and a corrected interpretation. Reexamination of the parental origin of their t(15q;15q) using polymorphic DNA markers that are mapped to various regions of 15q documented no molecular deletions at the 15q11-q13 region in either patient. Both patients were homozygous at all loci examined and their haplotypes on 15q coincided with one of those in their respective mothers. These results indicate that the presumed t(15q;15q) in each patient was actually an isochromosome 15q producing maternal uniparental disomy, consistent with genomic imprinting at the PWS locus.

Turner's syndrome: a behavioral and cytogenetic study

This study focused on the behavioral and cytogenetic aspects of Turner's syndrome. We evaluated the behavioral scores by ESPQ, HSPQ, and TAMAI tests. In the cytogenetic study, six different variables were defined by a chromosome image analysis computer system (Applied Imagine) that assessed changes in band organization and the measurement of mean optical density (MOD) in six G-bands (Xp21, Xq12, Xq21, Xq23, Xq25, Xq27). We studied 33 females with Turner's syndrome and compared them with 30 females individually matched for normal karyotype, short stature, age, and education. Significant differences were found between the two groups.

Molecular studies of parental origin and mosaicism in 45,X conceptuses

The present report summarizes molecular studies of parental origin and sex chromosome mosaicism in forty-one 45,X conceptuses, consisting of 29 spontaneous abortions and 12 liveborn individuals with Turner syndrome. Our studies indicate that most 45,X conceptuses have a single, maternally derived X chromosome, regardless of whether the conceptus is liveborn or spontaneously aborted. In studies of mosaicism, our identification of X- and Y-chromosome mosaics among 45,X spontaneous abortions indicates that mosaicism does not ensure survival to term of 45,X fetuses. However, the incidence of sex chromosome mosaicism is substantially higher in liveborn than in aborted 45,X conceptuses, indicating that the presence of a second cell line increases the likelihood of survival to term.

Molecular study of 45,X conceptuses: correlation with clinical findings

The parental origin of the single X in 45 cases (40 liveborns and 5 fetuses) with a 45,X karyotype was studied using polymorphic DNA probes. The single X was paternal in origin (Xp) in 10 cases (22.2%) and maternal (Xm) in 35 cases (77.8%). Y chromosome material was detected in 1 out of the 35 cases with a 45,Xm constitution. Analysis of parental ages and clinical data of the patients with respect to the origin of the single X revealed no significant differences between the origins.

Expression of RPS4X in fibroblasts from patients with structural aberrations of the X chromosome

A series of fibroblasts from patients with numerical or structural aberrations of the X chromosome were scored for the amount of mRNA of ribosomal protein S4 (RPS4X). Haplo-insufficiency of this gene has been reported previously to be a possible cause of Turner syndrome. Our results show that the transcription rate of RPS4X correlates with the number of gene copies. This confirms earlier findings indicating that this gene escapes X inactivation. In addition, we demonstrate that this applies to structurally aberrant X chromosomes. Our results show that RPS4X does not give rise to a type of haplo-insufficiency in these cases, because it escapes inactivation, even on structurally aberrant X chromosomes from patients with Turner syndrome. We therefore assume that RPS4X is not the most prominent candidate gene for Turner syndrome.

Survival of fetuses with 45,X: an instructive case and an hypothesis

The high (greater than 95%) fetal loss rate of 45,X embryos and fetuses has led to the suggestion that fetal survival with this karyotype requires the presence of mosaicism. However, in many instances, even given a "mild Ullrich-Turner syndrome" phenotype, mosaicism is not detected. In a pregnancy studied for advanced maternal age, CVS cultured cells showed 65% 45,X and 35% 46,X,r(X). After termination, 2 fetal tissues showed 95% 45,X cells. It is suggested that infants with the 45,X karyotype likely had mosaicism for a structurally abnormal X or Y chromosome during embryogenesis, but the abnormal cell line disappeared prior to birth.