Genetic counseling in Robertsonian translocations der(13;14): frequencies of reproductive outcomes and infertility in 101 pedigrees

A Familial Case of Robertsonian Translocation 13;14: Case Report

Robertsonian translocations are the most common form of chromosomal abnormalities that specifically involve the acrocentric chromosomes. Robertsonian translocation between chromosomes 13,14 and 14,21 are the most frequently reported. Infertility is common in genetically balanced carriers of these translocations, and their conceptions are more likely to have imbalances. Here we have reported a case of an 18-year-old female presenting with a complaint of primary amenorrhea. Cytogenetic analysis revealed a familial case of maternally inherited Robertsonian translocation (rob(13;14)(q10;q10)) affecting all the siblings. Genetic counseling and genetic testing are recommended especially in familial cases as the carriers are normal but can lead to several genetic disorders in their future generation.

The spectrum of chromosomal translocations in the Arab world: ethnic-specific chromosomal translocations and their relevance to diseases

Chromosomal translocations (CTs) are the most common type of structural chromosomal abnormalities in humans. CTs have been reported in several studies in the Arab world, but the frequency and spectrum of these translocations are not well characterized. The aim of this study is to conduct a systematic review to estimate the frequency and spectrum of CTs in the 22 Arab countries. Four literature databases were searched: PubMed, Science Direct, Scopus, and Web of Science, from the time of inception until July 2021. A combination of broad search terms was used to collect all possible CTs reported in the Arab world. In addition to the literature databases, all captured CTs were searched in three chromosomal rearrangement databases (Mitelman Database, CytoD 1.0 Database, and the Atlas of Genetics and Cytogenetics in Oncology and Hematology), along with PubMed and Google Scholar, to check whether the CTs are unique to the Arabs or shared between Arabs and non-Arabs. A total of 9,053 titles and abstracts were screened, of which 168 studies met our inclusion criteria, and 378 CTs were identified in 15 Arab countries, of which 57 CTs were unique to Arab patients. Approximately 89% of the identified CTs involved autosomal chromosomes. Three CTs, t(9;22), t(13;14), and t(14;18), showed the highest frequency, which were associated with hematological malignancies, recurrent pregnancy loss, and follicular lymphoma, respectively. Complex CTs were commonly reported among Arabs, with a total of 44 CTs, of which 12 were unique to Arabs. This is the first study to focus on the spectrum of CTs in the Arab world and compressively map the ethnic-specific CTs relevant to cancer. It seems that there is a distinctive genotype of Arabs with CTs, of which some manifested with unique clinical phenotypes. Although ethnic-specific CTs are highly relevant to disease mechanism, they are understudied and need to be thoroughly addressed.

Genetics of Male Infertility - Present and Future: A Narrative Review

Infertility affects 8%–12% of couples worldwide with a male factor contributing to nearly 50% of couples either as a primary or contributing cause. Several genetic factors that include single-gene and multiple-gene defects associated with male infertility were reported in the past two decades. However, the etiology remains ambiguous in a majority of infertile men (~40%). The objective of this narrative review is to provide an update on the genetic factors associated with idiopathic male infertility and male reproductive system abnormalities identified in the last two decades. We performed a thorough literature search in online databases from January 2000 to July 2021. We observed a total of 13 genes associated with nonobstructive azoospermia due to maturation/meiotic arrest. Several studies that reported novel genes associated with multiple morphological abnormalities of the sperm flagella are also discussed in this review. ADGRG2, PANK2, SCNN1B, and CA12 genes are observed in non-CFTR-related vas aplasia. The genomic analysis should be quickly implemented in clinical practice as the detection of gene abnormalities in different male infertility phenotypes will facilitate genetic counseling.

Maternal germline factors associated with aneuploid pregnancy loss: a systematic review

BACKGROUND

Miscarriage describes the spontaneous loss of pregnancy before the threshold of viability; the vast majority occur before 12 weeks of gestation. Miscarriage affects one in four couples and is the most common complication of pregnancy. Chromosomal abnormalities of the embryo are identified in ∼50% of first trimester miscarriages; aneuploidy accounts for 86% of these cases. The majority of trisomic miscarriages are of maternal origin with errors occurring during meiotic division of the oocytes. Chromosome segregation errors in oocytes may be sporadic events secondary to advancing maternal age; however, there is increasing evidence to suggest possible maternal germline contributions to this.

OBJECTIVE AND RATIONALE

The objective of this review was to appraise critically the existing evidence relating to maternal germline factors associated with pregnancy loss secondary to embryo aneuploidy, identify limitations in the current evidence base and establish areas requiring further research.

SEARCH METHODS

The initial literature search was performed in September 2019 and updated in January 2021 using the electronic databases OVID MEDLINE, EMBASE and the Cochrane Library. No time or language restrictions were applied to the searches and only primary research was included. Participants were women who had suffered pregnancy loss secondary to numerical chromosomal abnormalities of the embryo. Study identification and subsequent data extraction were performed by two authors independently. The Newcastle-Ottawa Scale was used to judge the quality of the included studies. The results were synthesized narratively.

OUTCOMES

The literature search identified 2198 titles once duplicates were removed, of which 21 were eligible for inclusion in this systematic review. They reported on maternal germline factors having variable degrees of association with pregnancy loss of aneuploid origin. The Online Mendelian Inheritance in Man (OMIM) gene ontology database was used as a reference to establish the functional role currently attributed to the genes reported. The majority of the cases reported and included were secondary to the inheritance of maternal structural factors such as Robertsonian translocations, deletions and insertions. Germline factors with a plausible role in aneuploid pregnancy loss of maternal origin included skewed X-inactivation and CGG repeats in the fragile X mental retardation (FMR1) gene. Studies that reported the association of single gene mutations with aneuploid pregnancy loss were conflicting. Single gene mutations with an uncertain or no role in aneuploid pregnancy loss included mutations in synaptonemal complex protein 3 (SYCP3), mitotic polo-like kinase 4 (PLK4) and meiotic stromal antigen 3 (STAG3) spindle integrity variants and 5,10-methylenetetrahydrofolate reductase (MTHFR).

WIDER IMPLICATIONS

Identifying maternal genetic factors associated with an increased risk of aneuploidy will expand our understanding of cell division, non-disjunction and miscarriage secondary to embryo aneuploidy. The candidate germline factors identified may be incorporated in a screening panel for women suffering miscarriage of aneuploidy aetiology to facilitate counselling for subsequent pregnancies.

Y chromosome microdeletion and cytogenetic findings in male infertility: A cross-sectional descriptive study

Background

Infertility affects about 15% of couples worldwide, and the male factor alone is responsible for approximately 50% of the cases. Genetic factors have been found to play important roles in the etiology of azoospermia and severe oligospermia conditions that affect 30% of individuals seeking treatment at infertility clinics.

Objective

To determine the frequency of chromosomal abnormalities and Y chromosome microdeletion in infertile men.

Materials and Methods

A total of 100 infertile men with abnormal semen parameters were included in this study from 2014 to 2018. Chromosomal analysis was carried out using standard G-banding using Trypsin Giemsa protocol. Multiplex polymerase chain reaction was used to determine the Y microdeletion frequency.

Results

All participants were aged between 22 and 48 yr with a mean and standard deviation of 35.5 ± 5.1. Of the 100 subjects included in the study, three had Klinefelter syndrome-47,XXY, one had balanced carrier translocation-46,XY,t(2;7)(q21;p12), one with the balanced carrier translocation with inversion of Y chromosome 45,XY,der(13;14)(q10;q10),inv(Y), one had polymorphic variant of chromosome 15, one had Yqh-, and another had an inversion of chromosome 9. Y chromosome microdeletion of Azoospermia factor c region was observed in 2% of the cases. To the best of our knowledge, the current study is the first reported case with unique, balanced carrier translocation of chromosome 2q21 and 7p21.

Conclusion

The present study emphasizes the importance of routine cytogenetic screening and Y microdeletion assessment for infertile men, which can provide specific and better treatment options before undergoing assisted reproductive technology during genetic counseling.

How much, if anything, do we know about sperm chromosomes of Robertsonian translocation carriers?

In men with oligozoospermia, Robertsonian translocations (RobTs) are the most common type of autosomal aberrations. The most commonly occurring types are rob(13;14) and rob(14;21), and other types of RobTs are described as 'rare' cases. Based on molecular research, all RobTs can be broadly classified into Class 1 and Class 2. Class 1 translocations produce the same breakpoints within their RobT type, but Class 2 translocations are predicted to form during meiosis or mitosis through a variety of mechanisms, resulting in variation in the breakpoint locations. This review seeks to analyse the available data addressing the question of whether the molecular classification of RobTs into Classes 1 and 2 and/or the type of DD/GG/DG symmetry of the involved chromosomes is reflected in the efficiency of spermatogenesis. The lowest frequency value calculated for the rate of alternate segregants was found for rob(13;15) carriers (Class 2, symmetry DD) and the highest for rob(13;21) carriers (Class 2, DG symmetry). The aneuploidy values for the rare RobT (Class 2) and common rob(14;21) (Class 1) groups together exhibited similarities while differing from those for the common rob(13;14) (Class 1) group. Considering the division of RobT carriers into those with normozoospermia and those with oligoasthenozoospermia, it was found that the number of carriers with elevated levels of aneuploidy was unexpectedly quite similar and high (approx. 70%) in the two subgroups. The reason(s) that the same RobT does not always show a similar destructive effect on fertility was also pointed out.

Prenatally detected isolated ventricular septum defects and the association with chromosomal aberrations-A nationwide register-based study from Denmark

OBJECTIVE

To evaluate the association between prenatally detected isolated ventricular septum defects (VSDs) and chromosomal aberrations in a nationwide study in Denmark.

METHOD

Nationwide, register-based study with prospectively collected data including all singleton pregnancies from 2014-2018. From the Danish Fetal Medicine Database, we retrieved data on maternal characteristics, first-trimester biomarkers, pre- and postnatal diagnoses, genetic test results, and pregnancy outcomes. VSDs were considered isolated in the absence of other malformations or soft markers, and with a low first-trimester risk assessment for trisomies 21, 18 and 13. All cases of an isolated VSD with a chromosomal anomaly were audited. The genetic tests included karyotyping and chromosomal microarray.

RESULTS

We retrieved data on 292 108 singleton pregnancies; 323 registered with a prenatally detected VSD and 697 with a VSD detected postnatally (incidence of 0.35%). Only 1/153 (0.7%, 95% CI 0.02;3.6%) of the isolated prenatally detected VSDs had an abnormal genetic test result (del (8)(q23.1)). Moreover, they had a lower free β-hCG MoM (0.9 MoM vs 0.99 MoM, P = 0.02), and were more likely born small for gestational age (SGA), defined as birthweight 2 or more SD below the mean, compared with the control population (5.2% vs 2.5%, P = 0.03).

CONCLUSION

We found a prevalence of chromosomal aberrations of 0.7% in fetuses with a prenatally detected isolated VSD. Moreover, we found an association between isolated VSDs and a larger proportion being born SGA.

Mortality and Cancer Incidence in Carriers of Balanced Robertsonian Translocations: A National Cohort Study

A balanced robertsonian translocation (rob) results from fusion of 2 acrocentric chromosomes. Carriers are phenotypically normal and are often diagnosed because of recurrent miscarriages, infertility, or aneuploid offspring. Mortality and site-specific cancer risks in carriers have not been prospectively investigated. We followed 1,987 carriers diagnosed in Great Britain for deaths and cancer risk, over an average of 24.1 years. Standardized mortality and incidence ratios were calculated comparing the number of observed events against population rates. Overall mortality was higher for carriers diagnosed before age 15 years (standardized mortality ratio (SMR) = 2.00, 95% confidence interval (CI): 1.09, 3.35), similar for those diagnosed aged 15–44 years (SMR = 1.06, 95% CI: 0.86–1.28), and lower for those diagnosed aged 45–84 years (SMR = 0.81, 95% CI: 0.68, 0.95). Cancer incidence was higher for non-Hodgkin lymphoma (standardized incidence ratio (SIR) = 1.90, 95% CI: 1.01, 3.24) and childhood leukemia (SIR = 14.5, 95% CI: 1.75, 52.2), the latter particularly in rob(15;21) carriers (SIR = 447.8, 95% CI: 11.3, 2,495). Rob(13;14) carriers had a higher breast cancer risk (SIR = 1.58, 95% CI: 1.12, 2.15). Mortality risks relative to the population in diagnosed carriers depend on age at cytogenetic diagnosis, possibly reflecting age-specific cytogenetic referral reasons. Carriers might be at greater risk of childhood leukemia and non-Hodgkin lymphoma and those diagnosed with rob(13;14) of breast cancer.

Genetic abnormalities and pregnancy loss

Genetic abnormalities, whether occurring in the conceptus or the parents, can predispose to sporadic or recurrent pregnancy loss (RPL). Abnormalities in the conceptus include aneuploidy, copy number changes, skewed X inactivation, and single gene disorders or mutations. Among parents who suffer RPL, the best studied genetic cause is balanced chromosomal translocations. For evaluation of genetic abnormalities in cases of pregnancy loss, chromosomal microarray is more likely to yield interpretable results than karyotype due to cell culture failure. For parents, karyotype remains the standard since microarray may not detect truly balanced translocations. For those with an identified underlying genetic abnormality, preimplantation genetic testing has been proposed to optimize the live birth rate. This approach shows promise, but currently lacks supporting evidence. In summary, various genetic causes for recurrent pregnancy loss are known, but when such a cause is identified, the implications for management remain unclear.

The dark side of centromeres: types, causes and consequences of structural abnormalities implicating centromeric DNA

Centromeres are the chromosomal domains required to ensure faithful transmission of the genome during cell division. They have a central role in preventing aneuploidy, by orchestrating the assembly of several components required for chromosome separation. However, centromeres also adopt a complex structure that makes them susceptible to being sites of chromosome rearrangements. Therefore, preservation of centromere integrity is a difficult, but important task for the cell. In this review, we discuss how centromeres could potentially be a source of genome instability and how centromere aberrations and rearrangements are linked with human diseases such as cancer.

Autosomal single-gene disorders involved in human infertility

Human infertility, defined as the inability to conceive after 1 year of unprotected intercourse, is a healthcare problem that has a worldwide impact. Genetic causes of human infertility are manifold. In addition to the chromosomal aneuploidies and rearrangements, single-gene defects can interfere with human fertility. This paper provides a review of the most common autosomal recessive and autosomal dominant single-gene disorders involved in human infertility. The genes reviewed are CFTR, SPATA16, AURKC, CATSPER1, GNRHR, MTHFR, SYCP3, SOX9, WT1 and NR5A1 genes. These genes may be expressed throughout the hypothalamic-pituitary–gonadal-outflow tract axis, and the phenotype of affected individuals varies considerably from varying degrees of spermatogenic dysfunction leading to various degrees of reduced sperm parameters, through hypogonadotropic hypogonadism reslting in pubertal deficiencies, until gonadal dysgenesis and XY and XX sex reversal. Furthermore, congenital bilateral absence of the vas deferens, as well as premature ovarian failure, have been reported to be associated with some single-gene defects.

Genetic Causes of Recurrent Pregnancy Loss

Pregnancy loss is one of the most common obstetric complications, affecting over 30% of conceptions. A considerable proportion of losses are due to genetic abnormalities. Indeed, over 50% of early pregnancy losses have been associated with chromosomal abnormalities. Most are due to de novo nondisjunctional events but balanced parental translocations are responsible for a small but important percentage of genetic abnormalities in couples with recurrent pregnancy loss. In the past, assessment of genetic abnormalities was limited to karyotype performed on placental or fetal tissue. However, advances in molecular genetic technology now provide rich genetic information about additional genetic causes of and risk factors for pregnancy loss. In addition, the use of preimplantation genetic testing in couples undergoing in vitro fertilization has the potential to decrease the risk of pregnancy loss from genetic abnormalities. To date, efficacy is uncertain but considerable potential remains. This chapter will review what is known about genetic causes of recurrent pregnancy loss with a focus on novel causes and potential treatments. Remaining knowledge gaps will be highlighted.

Mapping allele with resolved carrier status of Robertsonian and reciprocal translocation in human preimplantation embryos

Reciprocal translocations (RecT) and Robertsonian translocations (RobT) are among the most common chromosomal abnormalities that cause infertility and birth defects. Preimplantation genetic testing for aneuploidy using comprehensive chromosome screening for in vitro fertilization enables embryo selection with balanced chromosomal ploidy; however, it is normally unable to determine whether an embryo is a translocation carrier. Here we report a method named "Mapping Allele with Resolved Carrier Status" (MaReCs), which enables chromosomal ploidy screening and resolution of the translocation carrier status of the same embryo. We performed MaReCs on 108 embryos, of which 96 were from 13 RecT carriers and 12 were from three RobT carriers. Thirteen of the sixteen patients had at least one diploid embryo. We have confirmed the accuracy of our carrier status determination in amniotic fluid karyotyping of seven cases as well as in the live birth we have thus far. Therefore, MaReCs accurately enables the selection of translocation-free embryos from patients carrying chromosomal translocations. We expect MaReCs will help reduce the propagation of RecT/RobT in the human population.

Activity and High-Order Effective Connectivity Alterations in Sanfilippo C Patient-Specific Neuronal Networks

Induced pluripotent stem cell (iPSC) technology has been successfully used to recapitulate phenotypic traits of several human diseases in vitro. Patient-specific iPSC-based disease models are also expected to reveal early functional phenotypes, although this remains to be proved. Here, we generated iPSC lines from two patients with Sanfilippo type C syndrome, a lysosomal storage disorder with inheritable progressive neurodegeneration. Mature neurons obtained from patient-specific iPSC lines recapitulated the main known phenotypes of the disease, not present in genetically corrected patient-specific iPSC-derived cultures. Moreover, neuronal networks organized in vitro from mature patient-derived neurons showed early defects in neuronal activity, network-wide degradation, and altered effective connectivity. Our findings establish the importance of iPSC-based technology to identify early functional phenotypes, which can in turn shed light on the pathological mechanisms occurring in Sanfilippo syndrome. This technology also has the potential to provide valuable readouts to screen compounds, which can prevent the onset of neurodegeneration.

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Fibroblasts from two Sanfilippo C patients were reprogrammed to obtain iPSCs

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iPSCs were successfully differentiated to neural cells that mimic the disease

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Networks of patients’ neurons show altered activity and connectivity

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Early functional phenotypes are prevented in gene-corrected patients’ neurons

Recurrence risks for different pregnancy outcomes and meiotic segregation analysis of spermatozoa in carriers of t(1;11)(p36.22;q12.2)

Cumulative data obtained from two relatively large pedigrees of a unique reciprocal chromosomal translocation (RCT) t(1;11)(p36.22;q12.2) ascertained by three miscarriages (pedigree 1) and the birth of newborn with hydrocephalus and myelomeningocele (pedigree 2) were used to estimate recurrence risks for different pregnancy outcomes. Submicroscopic molecular characterization by fluorescent in situ hybridization (FISH) of RCT break points in representative carriers showed similar rearrangements in both families. Meiotic segregation patterns after sperm analysis by three-color FISH of one male carrier showed all possible outcomes resulting from 2:2 and 3:1 segregations. On the basis of empirical survival data, we suggest that only one form of chromosome imbalance resulting in monosomy 1p36.22→pter with trisomy 11q12.2→qter may be observed in progeny at birth. Segregation analysis of these pedigrees was performed by the indirect method of Stengel-Rutkowski and showed that probability rate for malformed child at birth due to an unbalanced karyotype was 3/48 (6.2±3.5%) after ascertainment correction. The risk for stillbirths/early neonatal deaths was -/48 (<1.1%) and for miscarriages was 17/48 (35.4±6.9%). However, the probability rate for children with a normal phenotype at birth was 28/48 (58.3±7.1%). The results obtained from this study may be used to determine the risks for the various pregnancy outcomes for carriers of t(1;11)(p36.22;q12.2) and can be used for genetic counseling of carriers of this rearrangement.

The Genetics of Infertility: Current Status of the Field

Infertility is a relatively common health condition, affecting nearly 7% of all couples. Clinically, it is a highly heterogeneous pathology with a complex etiology that includes environmental and genetic factors. It has been estimated that nearly 50% of infertility cases are due to genetic defects. Hundreds of studies with animal knockout models convincingly showed infertility to be caused by gene defects, single or multiple. However, despite enormous efforts, progress in translating basic research findings into clinical studies has been challenging. The genetic causes remain unexplained for the vast majority of male or female infertility patients. A particular difficulty is the huge number of candidate genes to be studied; there are more than 2,300 genes expressed in the testis alone, and hundreds of those genes influence reproductive function in humans and could contribute to male infertility. At present, there are only a handful of genes or genetic defects that have been shown to cause, or to be strongly associated with, primary infertility. Yet, with completion of the human genome and progress in personalized medicine, the situation is rapidly changing. Indeed, there are 10-15 new gene tests, on average, being added to the clinical genetic testing list annually.

Preimplantation genetic diagnosis for couples with a Robertsonian translocation: practical information for genetic counseling

PURPOSE

To evaluate the proportions of abnormal and normal embryos detected by preimplantation genetic diagnosis (PGD) of infertile couples of whom one was a Robertsonian translocation (RT) carrier, and to provide practical information, including details of reproductive outcomes, to aid in genetic counseling of such couples.

METHODS

We retrospectively analyzed all PGD cycles conducted to deal with RT at our center between January 2000 and December 2009. Subject demographic and clinical data were compared with the results of PGD.

RESULTS

Employing PGD, we conducted a total of 66 cycles on 34 couples of whom one was an RT carrier, including 24 female and 10 male carriers. Of the 514 blastomeres tested, 161 (31.3%) were normal or balanced. Of the 57 cycles that included embryo transfer, 17 (29.8%) attained positivity for human chorionic gonadotropin (hCG). A total of 17 embryos were implanted and 16 babies, including two sets of twins, were born. The takehome baby rate was 41.2% per couple and the loss rate 6.6%. Receiver operating characteristic curve analysis showed that the proportion of alternate embryos associated with a sensitivity of 70.6% for prediction of clinical pregnancy following PGD was 0.31. Sex of the carrier and type of translocation were not significantly associated with pregnancy outcomes.

CONCLUSION

Couples with RT may benefit from PGD; pregnancy success rate is improved and embryo loss reduced. We found that about 30% of embryos were of normal or balanced chromosomal constitution and that the percentage of normal or balanced embryos was predictive of PGD outcome.

Cytogenetic findings and reproductive outcome of infertile couples referred to an assisted reproduction program

It is still undefined whether all the couples entering an assisted reproduction program should undergo to karyotype analysis. The present study was conducted to determine the prevalence of chromosomal abnormalities in a non-selected sample of 1,146 couples referred to assisted reproduction technologies (ART), and to analyze the outcome of pregnancies from couples in whom cytogenetic anomalies were detected. Irrespective of the infertility factor, fertilization was achieved by intracytoplasmic sperm injection (ICSI). A total number of 35 karyotype anomalies were diagnosed, corresponding to an abnormality frequency of 1.52% (1.83% for men and 1.22% for women). As could be expected, the majority of men presenting karyotype anomalies had a low sperm count. Among women, the majority of cytogenetic anomalies were detected in individual not presenting risk factors for aberrant karyotype. Around 41% of pregnancies achieved in couples presenting chromosomal anomalies ended in spontaneous abortion. Information on fetal karyotype was limited. No major malformations were observed among newborns from parents with abnormal karyotype. In consideration of the elevated frequency of pregnancy loss, it seems advisable to recommend that chromosomal analysis be performed in all couples undergoing ART. This with the aim of identifying patients that would possibly benefit from pre-implantation genetic diagnosis.

Meiotic segregation of Robertsonian translocations ascertained in cleavage-stage embryos--implications for preimplantation genetic diagnosis

BACKGROUND

The aim of this study was to ascertain the prevalence of meiotic segregation products in embryos from carriers of 13/14 and 14/21 Robertsonian translocations and to estimate the predictive value of testing single cells using the fluorescence in situ hybridization (FISH) technique, to provide more information for decision-making about PGD.

METHODS

In this prospective cohort study, the copy number of translocation chromosomes in nuclei from lysed blastomeres of cleavage-stage embryos was ascertained using locus-specific FISH probes. Logistic regression analysis, controlling for translocation type, female age and fertility status, was used to calculate the odds ratio (OR) of unbalanced segregation products for female and male heterozygotes. The primary diagnostic measure was the predictive value of the test result. The primary outcome measure was the live birth rate per couple.

RESULTS

Female carriers were four times more likely than male carriers to produce embryos with an unbalanced translocation product (OR 3.8, 95% confidence interval 2.0-7.2, P < 0.001). The prevalence of abnormality for the chromosomes tested in embryos from female or male heterozygotes was estimated to be 43 or 28%, respectively, while estimates of the predictive value were 93-100 or 96-100% for a normal test result and 79 or 57% for an abnormal test result. The live birth rate per couple was 58% for female carriers and 50% for male carriers.

CONCLUSIONS

For female carriers, PGD using FISH could reduce the risk of miscarriage from either translocation or the risk of Down syndrome from the 14/21 Robertsonian translocation. PGD using FISH for male carriers is unlikely to be indicated given the relatively low prevalence of chromosome imbalance and low predictive value.

Inheritance of a t(13;14)(q10;q10) Robertsonian translocation with a low level of trisomy 13 mosaicism

INTRODUCTION

Low level of trisomy 13 mosaicism is a rare condition. In the present report, we describe a case of a 19-month-old boy with poor feeding, poor weight gain, mild dysmorphic features, mild muscular hypotonia, and speech delay.

DISCUSSION

Cytogenetic analysis on metaphases of lymphocytes revealed an 8% mosaic Robertsonian translocation trisomy 13 in the boy and a balanced Robertsonian translocation, 45,XX,der(13;14)(q10;q10), in his normal mother. Fluorescence in situ hybridization (FISH) on patient lymphocytes disclosed 4% of metaphases with a trisomy 13. The trisomy 13 mosaicism in metaphases could not be identified by interphase FISH. The percentage of three signals (4%) was within the standard deviation in diploid controls. Follow-up of the patient was performed at the age of 7 1/12 years, and in cells from buccal smear of the patient, trisomy 13 was detected in 11% of interphases analyzed that is a higher frequency. Uniparental disomy of chromosomes 13 and 14 were excluded in the boy, and therefore, his phenotypic abnormalities most likely were caused by the low level of trisomy 13 mosaicism.

CONCLUSION

The detailed report of this patient described the infrequent occurrence of a low mosaic Robertsonian translocation trisomy 13. We suggest to study cases of low trisomy mosaicism preferentially using metaphase analyses rather than interphase FISH. Our case is helpful in further defining the phenotype of these patients.

Preconceptional diagnosis for Robertsonian translocation as an alternative to preimplantation genetic diagnosis in two situations: a pilot study

INTRODUCTION

Preimplantation genetic diagnosis (PGD) is widely used for women heterozygous for a Robertsonian translocation. Preconceptional diagnosis (PCD), performed before fertilization, may be an alternative to PGD, especially in countries where PGD is restricted or prohibited, as in France. It could also give different information and clarify the influence of reproductive and obstetric history.

METHODS

In our study, translocation was diagnosed before ICSI in five cases (group A), and after newborn or fetal aneuploidy or miscarriage in two cases, (group B).

RESULTS

First polar body (PB1) analysis using acrocentric centromeric probes was done for 85 PB1s, and aneuploidy rate was at 42.4%. Oocyte aneuploidy rate differed (p<0.0001) between groups A and B (30% vs 84%). Despite the small group sizes, we demonstrate a correlation (p=0.0358) of aneuploidy rate in polar bodies after 2 or more attempts. Three live births were recorded, all in group A.

DISCUSSION

PCD could thus be an alternative to PGD. This pilot study also provides new prognostic information taking into account the women's natural history, but further confirmation is required.