Low-level X chromosome mosaicism in women with sporadic premature ovarian failure

Genetic counseling for women with 45,X/46,XX mosaicism: Towards more personalized management

Despite numerous clinical series, consistent karyotype-phenotype correlations for Turner syndrome have not been established, although a lower level of 45,X is generally thought to be associated with a milder phenotype. This limits personalized counseling for women with 45,X/46,XX mosaicism. To better understand the phenotypic spectrum associated with various levels of 45,X/46,XX mosaicism, we compared patients evaluated in the Massachusetts General Hospital Turner Syndrome Clinic to determine if cardiac, renal, and thyroid abnormalities correlated with the percentage of 45,X cells present in a peripheral blood karyotype. of the 118 patients included in the study, 78 (66%) patients had non-mosaic 45,X and 40 (34%) patients had varying levels of 45,X/46,XX mosaicism. Patients with ≤70% 45,X compared with those with >70% 45,X had a significantly lower frequency of cardiac and renal anomalies. The presence of hypothyroidism was somewhat lower for the ≤70% 45,X group, but was not statistically significant. Supplemental tissue testing on another tissue type, typically buccal mucosa, was often useful in counseling patients with 45,X mosaicism. Given the modest sample size of patients with varying levels of mosaicism and the variability of Turner syndrome abnormalities, we hope this preliminary study will inspire a multicenter collaboration, which may lead to modification of clinical guidelines. Because several patients with ≤70% 45,X were ascertained from perinatal care referrals, we still advise women with 45,X mosaicism pursuing pregnancy to receive standard Turner syndrome cardiac surveillance. There is an opportunity to personalize counseling and surveillance for patients based on percentage of 45,X cells on chromosome analysis.

Low-level X Chromosome Mosaicism: A Common Finding in Women Undergoing IVF

BACKGROUND/AIM

To determine the incidence of X chromosome mosaicism in women undergoing in vitro fertilization (IVF) treatment and present preimplantation genetic testing for aneuploidy (PGT-A) outcome of this group.

PATIENTS AND METHODS

A total of 1,058 women undergoing IVF and 154 women with no fertility problems were enrolled in the study. Karyotyping from peripheral blood lymphocytes was performed by conventional cytogenetics. Twenty-nine women with X mosaicism underwent PGT-A by array-comparative genomic hybridization from embryos at the blastocyst stage.

RESULTS AND CONCLUSION

Out of 1,058 women undergoing IVF, 166 (15.7%) had an abnormal karyotype. The most common finding (14.6%) was X chromosome mosaicism. Its frequency was higher in women >35 years old and reached 46.1% in those >45 years of age. PGT-A results of 130 blastocysts tested showed that 29/117 (24.8%) were euploid; 17/29 (60%) were transferred and 10/17 (70%) were successfully implanted, indicating that PGT-A may be an option for women with low-level X chromosome mosaicism undergoing IVF in order to improve the likelihood of a successful pregnancy outcome.

Two Cases of Primary Ovarian Insufficiency Accompanied by High Serum Anti-Müllerian Hormone Levels and Preservation of Ovarian Follicles

Primary ovarian insufficiency (POI) is defined as the presence of amenorrhea for ≥ 4 months accompanied by evidence of two serum follicle-stimulating hormone levels in the menopausal range in women aged < 40 years. Anti-Müllerian hormone (AMH) has been recognized as the most reliable marker of ovarian reserve status, and its serum level is very low or undetectable in women with POI. Here we report two cases of patients who were diagnosed with POI despite high serum AMH levels and preservation of ovarian follicles, as revealed by ultrasound. In addition, we have presented a review of the current literature regarding this condition.

X chromosome aneuploidy and micronuclei in fertile mares

Abnormalities of chromosomes are an important and well documented cause of disorders of sexual development, fertility problems and congenital anomalies in mammals. Detection of low-level 63,X/64,XX mosaicism during routine cytogenetic evaluation is a challenge because its clinical significance is not yet fully clear. This study describes the prevalence and levels of 63,X mosaicism for a cohort of fertile mares and compares the results with eight problem mares for which no clinical cause of sub-fertility was found. The study design allowed for the analysis of micronuclei which are biomarkers of genomic instability and can disturb cell divisions, drive cancer development or cause congenital diseases. Although 27% of the fertile mares were identified to be 63,X mosaics, the results showed that the rates of abnormal cells were very low (1-3%). Levels of abnormal cells in problem mares with 63,X mosaicism were similar or higher. The average rate of micronuclei in the blood of the fertile mares was ∼1%, well below the baseline (5%) which was proposed for peripheral blood of normal healthy humans. We found weak to modest, but not significant, correlations between the age of fertile mares and 63,X cells (Kendall's tau b = 0.2905; p > 0.05) as well as the rate of micronuclei (Kendall's tau b = 0.1896; p > 0.05). Likewise, the correlation between presence of a 63,X cell line and micronuclei rate was not significant (Kendall's tau b = 0.3201; p > 0.05). The presence of 63,X cells in rates greater than 3% may indeed indicate a higher risk for sub-fertility and eventually for associated health problems in such mares. Detection and elimination of mares with high level of X aneuploidies from breeding may have a positive effect on the fertility within the general horse population. This data may support the evaluation of problem mares with mosaic karyotypes involving the X chromosome.

Ontogenetic and Pathogenetic Views on Somatic Chromosomal Mosaicism

Intercellular karyotypic variability has been a focus of genetic research for more than 50 years. It has been repeatedly shown that chromosome heterogeneity manifesting as chromosomal mosaicism is associated with a variety of human diseases. Due to the ability of changing dynamically throughout the ontogeny, chromosomal mosaicism may mediate genome/chromosome instability and intercellular diversity in health and disease in a bottleneck fashion. However, the ubiquity of negligibly small populations of cells with abnormal karyotypes results in difficulties of the interpretation and detection, which may be nonetheless solved by post-genomic cytogenomic technologies. In the post-genomic era, it has become possible to uncover molecular and cellular pathways to genome/chromosome instability (chromosomal mosaicism or heterogeneity) using advanced whole-genome scanning technologies and bioinformatic tools. Furthermore, the opportunities to determine the effect of chromosomal abnormalities on the cellular phenotype seem to be useful for uncovering the intrinsic consequences of chromosomal mosaicism. Accordingly, a post-genomic review of chromosomal mosaicism in the ontogenetic and pathogenetic contexts appears to be required. Here, we review chromosomal mosaicism in its widest sense and discuss further directions of cyto(post)genomic research dedicated to chromosomal heterogeneity.

Premutations of FMR1 CGG repeats are not related to idiopathic premature ovarian failure in Iranian patients: A case control study

Premature ovarian failure (POF) is a reproductive disease which affects 1 in 100 under 40 years women. FMR1 premutation carriers of CGG repeats are supposed to be at increased risk for POF. We have examined the 5'UTR region of the gene to find any association between the repeat size and the disease etiology in Iranian population. 30 women with early idiopathic POF and 30 fertile control women were selected. We used triplet repeat primed PCR (TP PCR) assay and gene-specific primers to amplify the CpG Island of FMR1 gene promoter region. The amplification results were analyzed by capillary electrophoresis and Gene Marker software. Among 30 patients, two had intermediate repeat size, one had premutation and the rest had CGG repeat of the normal range. Two of controls had intermediate repeats and none had a premutation. Two groups had significant differences in the repeat number average (p = 0.007) and in the average length of the smallest allele (p < 0.001), but had no promising difference in average length of the longest allele (p = 0.453). Although the two groups showed a significant difference in the length of alleles, their length was within normal range. Perhaps the polymorphism, in connection with the genome's entire network, has been involved in the development of the disease, or there has been a fundamentally different mechanism for the disease in Iranian population. A larger number of Iranian POF patients should be investigated for any probable relationship between the CGG triplet repeat length and the etiology of the disease.

Cell-free DNA screening for fetal aneuploidy as a clinical service

Non-invasive prenatal testing (NIPT) through the analysis of cell free (cf)DNA is revolutionizing prenatal screening for fetal aneuploidy. Current methods used in clinical practice include shotgun massively parallel sequencing (s-MPS); targeted (t-MPS); and an approach that takes advantage of single nucleotide polymorphism (SNP) differences between mother and fetus. Efficacy of cfDNA testing for the common autosomal trisomies far exceeds that of conventional screening. Depending on the methodology used, reasons for discordancy between cfDNA results and fetal karyotype can include true fetal mosaicism, confined placental mosaicism, presence of a maternal karyotype abnormality, insufficient counting due to low fetal fraction, and a vanishing twin. Among the possible cfDNA strategies a Primary test has the highest performance but is expensive, while a Contingent cfDNA test can achieve high performance at a relatively low cost. Practicalities to be considered in the provision of testing include pretest counseling about the scope and accuracy of the testing, the interpretation of results when there is a low fetal fraction and follow-up studies for positive test results. The role of first trimester nuchal translucency measurement and conventional biochemical testing needs to be reassessed in the context of the use of cfDNA.

Possible influence of menstrual cycle on lymphocyte X chromosome mosaicism

PURPOSE

Estrogens are known to selectively influence cell proliferation. Physiological variations of blood hormone concentration might play a role in regulating the level of X chromosome aneuploidy. In this study we observed the percentages of X aneuploid cells in standard lymphocyte cultures from blood samples obtained in relation to the menstrual cycle, noting whether collection occurred during either the follicular or the luteal phase.

METHODS

A study consisting of 28 women with X mosaicism and recurrent pregnancy loss, and 28 age-matched healthy controls. Cytogenetic studies were carried out on peripheral blood samples according to standard procedures.

RESULTS

A significant difference in the percentage of X aneuploidy was found in blood samples obtained during different phases of the menstrual cycle. In the case group, the mean value of aneuploid cells in the follicular and luteal phase samples was 10.0 and 6.3 % respectively and in the control group, it was 2.8 and 1.0 % (P < 0.0001). The difference in the case group varied between 0 and 8 % (3.6 ± 2.1 %) and in the control group between 0 and 4 % (1.7 ± 1.1 %). The specificity for detecting true X mosaicism was 0.875. We estimate that the initial diagnosis of X mosaicism could be correct in 68 % of patients with recurrent pregnancy loss.

CONCLUSIONS

This observational study establishes that the time of blood sampling in relation to the menstrual cycle can influence lymphocyte X chromosome mosaicism. The results, further proven by additional controlled studies, would have practical implications for genetic counselling and fertility treatment.

Generalized epilepsy in a patient with mosaic Turner syndrome: a case report

INTRODUCTION

Reports on cases of epilepsy in Turner syndrome are rare and most of them have cortical developmental malformations. We report the case of a Taiwanese patient with mosaic Turner syndrome with generalized tonic-clonic epilepsy and asymmetrical lateral ventricles but no apparent cortical anomaly.

CASE PRESENTATION

A 49-year-old Taiwanese woman without family history presented with infrequent generalized tonic-clonic epilepsy since she was 11 years old. On examination, her short stature, webbed neck, swelling of hands and feet, retrognathic face, and mild intellectual disability were noted. She had spontaneous menarche and regular menses. Brain magnetic resonance imaging showed asymmetrical lateral ventricles and diffuse subcortical white matter T2-weighted hyperintensities. Chromosome studies disclosed low aneuploid (10%) 45,X/46,XX/47,XXX mosaic Turner syndrome.

CONCLUSIONS

There is increasing evidence that epilepsy can be an uncommon presentation of Turner syndrome. Mosaic Turner syndrome with 47, XXX probably increases the risk of epilepsy but more research is needed to reach a conclusion. This case also strengthens our knowledge that Turner syndrome can be one of the pathologic bases of asymmetrical lateral ventricles. When a patient has idiopathic/cryptogenic epilepsy or asymmetrical lateral ventricles on brain images, the presence of a mild Turner phenotype warrants further chromosome studies.

Chromosome abnormalities in Indonesian patients with short stature

Background

Short stature is associated with several disorders including wide variations of chromosomal disorders and single gene disorders. The objective of this report is to present the cytogenetic findings in Indonesian patients with short stature.

Methods

G-banding and interphase/metaphase FISH were performed on short stature patients with and without other clinical features who were referred by clinicians all over Indonesia to our laboratory during the year 2003–2009.

Results

The results of chromosomal analysis of ninety seven patients (mean age: 10.7 years old) were collected. The group of patients with other clinical features showed sex chromosome abnormalities in 45% (18/40) and autosomal abnormalities in 10% (4/40), whereas those with short stature only, 42.1% (24/57) had sex chromosome abnormalities and 1.75% (1/57) had autosomal abnormalities. The autosomal chromosomal abnormalities involved mostly subtelomeric regions. Results discrepancies between karyotype and FISH were found in 10 patients, including detection of low-level monosomy X mosaicism in 6 patients with normal karyotype, and detection of mosaic aneuploidy chromosome 18 in 1 patient with 45,XX,rob(13;14)(q10;q10).

Statistical analysis showed no significant association between the groups and the type of chromosomal abnormalities.

Conclusion

Chromosome abnormalities account for about 50% of the short stature patients. Wide variations of both sex and autosomal chromosomes abnormalities were detected in the study. Since three out of five patients had autosomal structural abnormalities involving the subtelomeric regions, thus in the future, subtelomeric FISH or even a more sensitive method such as genomic/SNP microarray is needed to confirm deletions of subtelomeric regions of chromosome 9, 11 and 18. Low-level mosaicism in normal karyotype patients indicates interphase FISH need to be routinely carried out in short stature patients as an adjunct to karyotyping.