Polar body-based preimplantation diagnosis for X-linked disorders

A decade of molecular preimplantation genetic diagnosis of 350 blastomeres for beta-thalassemia combined with HLA typing, aneuploidy screening and sex selection in Iran

Background

Preimplantation genetic diagnosis (PGD) has been developed to detect genetic disorders before pregnancy which is usually done on blastomeres biopsied from 8-cell stage embryos obtained from in vitro fertilization method (IVF).

Here we report molecular PGD results for diagnosing of beta thalassemia (beta-thal) which are usually accompanied with evaluating chromosomal aneuploidies, HLA typing and sex selection.

Methods

In this study, haplotype analysis was performed using short tandem repeats (STRs) in a multiplex nested PCR and the causative mutation was detected by Sanger sequencing.

Results

We have performed PGDs on 350 blastomeres from 55 carrier couples; 142 blastomeres for beta-thal only, 75 for beta-thal and HLA typing, 76 for beta-thal in combination with sex selection, and 57 for beta-thal and aneuploidy screening. 150 blastomeres were transferable, 15 pregnancies were happened, and 11 babies born.

We used 6 markers for beta-thal, 36 for aneuploidy screening, 32 for sex selection, and 35 for HLA typing. To our knowledge combining all these markers together and the number of STR markers are much more than any other studies which have ever done.

Conclusions

PGD is a powerful diagnostic tool for carrier couples who desire to have a healthy child and wish to avoid medical abortion.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12884-022-04660-9.

Improving preimplantation genetic diagnosis (PGD) reliability by selection of sperm donor with the most informative haplotype

BACKGROUND

The study is aimed to describe a novel strategy that increases the accuracy and reliability of PGD in patients using sperm donation by pre-selecting the donor whose haplotype does not overlap the carrier's one.

METHODS

A panel of 4-9 informative polymorphic markers, flanking the mutation in carriers of autosomal dominant/X-linked disorders, was tested in DNA of sperm donors before PGD. Whenever the lengths of donors' repeats overlapped those of the women, additional donors' DNA samples were analyzed. The donor that demonstrated the minimal overlapping with the patient was selected for IVF.

RESULTS

In 8 out of 17 carriers the markers of the initially chosen donors overlapped the patients' alleles and 2-8 additional sperm donors for each patient were haplotyped. The selection of additional sperm donors increased the number of informative markers and reduced misdiagnosis risk from 6.00% ± 7.48 to 0.48% ±0.68. The PGD results were confirmed and no misdiagnosis was detected.

CONCLUSIONS

Our study demonstrates that pre-selecting a sperm donor whose haplotype has minimal overlapping with the female's haplotype, is critical for reducing the misdiagnosis risk and ensuring a reliable PGD. This strategy may contribute to prevent the transmission of affected IVF-PGD embryos using a simple and economical procedure.

TRIAL REGISTRATION

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. DNA testing of donors was approved by the institutional Helsinki committee (registration number 319-08TLV, 2008). The present study was approved by the institutional Helsinki committee (registration number 0385-13TLV, 2013).

Preimplantation genetic diagnosis for monogenic diseases: overview and emerging issues

Preimplantation genetic diagnosis (PGD) is an established reproductive option for couples at risk of conceiving a pregnancy affected with a known genetic disease, who wish to avoid an (additional) affected child, termination of pregnancy or recurrent miscarriages. Early technologies concentrated on different approaches to direct mutation testing for monogenic diseases using single cell PCR protocols, or sex selection by fluorescent in situ hybridization for X-linked monogenic disease. Development of multiplex fluorescent PCR allowed simultaneously testing of linked markers alongside the mutation test, increasing the accuracy by controlling for contamination and identifying allele drop-out. The advent of highly effective whole genome amplification methods has opened the way for new technologies such as preimplantation genetic haplotyping and microarrays, thus increasing the number of genetic defects that can be detected in preimplantation embryos; the number of cases carried out and the new indications tested increases each year. Different countries have taken very different approaches to legislating and regulating PGD, giving rise to the phenomenon of reproductive tourism. PGD is now being performed for scenarios previously not undertaken using prenatal diagnosis, some of which raise significant ethical concerns. While PGD has benefited many couples aiming to have healthy children, ethical concerns remain over inappropriate use of this technology.

Preimplantation genetic diagnosis (PGD) for SHOX-related haploinsufficiency in conjunction with trisomy 21 detection by molecular analysis

PURPOSE

Development of a molecular PGD protocol for a male with an X-linked deletion in the SHOX gene region, located in the pseudoautosomal region of the X/Y chromosomes. Due to excessive recombination in this region, the deletion can be found in male offspring.

METHODS

We developed a 13 marker multiplex fluorescent PCR protocol: 3 markers within the deleted SHOX region, 5 flanking markers, 3 informative markers on chromosome 21 (advanced maternal age) and 2 markers for sex determination.

RESULTS

Of four embryos, two wild type males, diploid for chromosome 21 were transferred resulting in twin boys. One embryo was an affected female and another embryo was Turner. Amniocentesis confirmed the implanted embryos were males (46XY), with no recombinations.

CONCLUSIONS

While many X-linked disorders can be analyzed by sexing, genes located in the pseudoautosomal regions have high XY recombination rates, requiring multiple markers to enable an accurate diagnosis.

PGD for fragile X syndrome: ovarian function is the main determinant of success

BACKGROUND

PGD for fragile X syndrome (FRAX) is inefficient, probably owing to fewer oocytes, poor embryo quality and difficulties in genetic analysis. We investigated IVF-PGD in FRAX mutation carriers compared with controls, looking at the effects of oocyte and embryo number/quality on live birth outcome.

METHODS

We performed IVF-PGD in 27 patients with the FRAX mutation and 33 controls with other genetic diseases. Genetic testing was by multiplex PCR.

RESULTS

Seventy-nine and 108 IVF-PGD cycles were started in FRAX mutation carriers and controls, respectively. Twenty-two patients had a premutation (CGG repeat number 60-200) and five had a full mutation (300-2000 CGG repeats). FRAX patients required higher doses of gonadotrophins (6788 ± 2379 versus 4360 ± 2330, P< 0.001) but had lower peak serum estradiol levels (8166 ± 5880 versus 10 211 ± 4673, P = 0.03) and fewer oocytes retrieved (9.8 ± 6 versus 14 ± 8, P = 0.01). The cancellation rate (unsatisfactory ovarian response) was higher in the FRAX group than in the control group (13 versus 1%, P < 0.001). When embryos were transferred, ongoing pregnancy/live birth rates per transfer were similar (29 versus 36%, P = 0.54).

CONCLUSIONS

Ovarian dysfunction in FRAX carriers is more prevalent and profound than previously appreciated, with a high cancelation rate and reduced efficiency of PGD. The main determinant for successful PGD for FRAX is ovarian dysfunction. When embryo transfer is possible, the results are comparable to PGD for other monogenic diseases.

Preimplantation genetic diagnosis (PGD) for nonsyndromic deafness by polar body and blastomere biopsy

PURPOSE

Development of an efficient and reliable PGD protocol for nonsyndromic deafness, by polar body (PB) and blastomere PGD.

METHODS

The GJB2/GJB6 mutations along with 12 polymorphic markers were used in PGD analysis of blastomeres or polar bodies in 14 couples for 35 cycles. Marker informativity, diagnosis rates, Allele Drop Out (ADO) rates and PB1 heterozygosity rates were assessed.

RESULTS

Six cycles were performed by PB biopsy, 27 by blastomere and two combined cycles, resulting in delivery of three unaffected children and five ongoing pregnancies. Diagnosis rates for PB and blastomeres were similar. Only 17% PB1s were heterozygote. ADO rates of 19% were observed in both groups.

CONCLUSIONS

We have developed a single cell multiplex PGD protocol for nonsyndromic deafness with a high efficiency of diagnosis. Most PB1 are homozygous, and similar ADO rates were observed; therefore, blastomere biopsy appears to be the method of choice for this autosomal recessive disease.

Preimplantation genetic diagnosis for fragile X syndrome: is there increased transmission of abnormal FMR1 alleles among female heterozygotes?

BACKGROUND

Fragile X syndrome is caused by a CGG triplet-repeat expansion mutation in the FMR1 gene. Previous studies have shown increased transmission of abnormal alleles in the 51-60 repeat range. This study was undertaken to evaluate the performance of preimplantation genetic diagnosis (PGD) for fragile X, and to assess the transmission rate of the abnormal FMR1 alleles in this setting.

METHOD

The study included 18 fragile X carriers who applied for PGD. FMR1 CGG repeats ranged from 70 to 300. PGD was performed using multiplex-nested PCR, with simultaneous amplification of the CGG repeat region and several polymorphic markers, and sex chromosome markers.

RESULTS

Four patients had a poor ovarian response, and could not undergo PGD. The remaining 14 patients underwent 47 PGD cycles. A total of 565 oocytes were aspirated. Of the 386 embryos that were successfully biopsied, 18 (6.4%) could not be analyzed due to amplification failure, and 12 (4.3%) had sex chromosomal abnormalities. Of the remaining 250 embryos, the abnormal allele was transmitted to 124 embryos (49.6%) compared to 126 (50.4%) for the normal allele. This difference was not statistically significant. Only embryos carrying the normal allele were transferred, resulting in 7 clinical pregnancies (18% per embryo transfer).

CONCLUSIONS

Our results demonstrate that PGD for fragile X is feasible, and that carriers transmit the abnormal allele at the same frequency as the normal allele.

Management of carriers and babies with haemophilia

Although up to 30% of babies born with haemophilia do not have a family history of the disorder, the remaining 70% are born in families where haemophilia has been diagnosed. It has been estimated that for each male with haemophilia, there are five potential female carriers. Such women will benefit from knowledge of both their genetic (mutation present or not) and phenotype (level of plasma factor activity) status. Genetic counselling services to provide information and testing, together with plasma factor measurement, should be offered where available to all women at risk of being carriers. It is critical that women know their plasma factor measurement as they may have mild haemophilia (factor 5-30%, reference range 50-150%) which requires management at times of medical and surgical procedures and following trauma. Close liaison between adult and paediatric haemophilia centres and obstetric-gynaecology units is important to ensure that clinical carers identify and address carriers' needs. Genetic testing should be performed only after a potential carrier has been counselled and supported to receive such information. There is no coercion to accept such testing. An advantage of genetic testing is to then discuss pre-implantation genetic diagnosis which is an ex-vitro form of prenatal diagnosis. This can assist couples at risk of having a child with haemophilia who wish to reduce their anxieties about reproduction. Approximately 4% of boys with haemophilia, born in countries with good maternal care, will have intracranial haemorrhage in the neonatal period. There are no high-level evidence-based guidelines for the management of delivery or of the newborn with haemophilia. Obstetricians or other birth attendants need to be advised of the possibility of delivery of a boy with haemophilia and seek support from a haemophilia specialist during the pregnancy. The mother can then be monitored and plans for delivery be developed between her medical consultants and discussed with her. It is always preferable for a carrier to know of her genetic and phenotypic status before becoming pregnant so that she is informed as to her options and requirements for safe delivery.

Preimplantation genetic diagnosis in assisted reproduction

Despite its novelty, preimplantation genetic diagnosis has become an alternative to traditional prenatal diagnosis, allowing the establishment of only unaffected pregnancies and avoiding the risk of pregnancy termination. In addition, preimplantation genetic diagnosis is presently applied for much wider indications than prenatal diagnosis, including common diseases with genetic predisposition and preimplantation human leukocyte antigen typing, with the purpose of establishing potential donor progeny for stem cell treatment of siblings. Many hundreds of apparently healthy, unaffected children have been born after preimplantation genetic diagnosis, presenting evidence of its accuracy, reliability and safety. Preimplantation genetic diagnosis appears to be of special value for avoiding age-related aneuploidies in patients of advanced reproductive age, improving reproductive outcome, particularly obvious from their reproductive history, and is presently an extremely attractive option for carriers of balanced translocations to have unaffected children of their own.

Preimplantation genetic diagnosis for fragile X syndrome using multiplex nested PCR

Fragile X syndrome is caused by a dynamic mutation in the FMR1 gene. Normal individuals have <55 CGG repeats in the 5 untranslated region, premutation carriers have 55-200 repeats and a full mutation has >200 repeats. Female carriers are at risk of having affected offspring. A multiplex nested polymerase chain reaction protocol is described for preimplantation genetic diagnosis (PGD) of fragile X syndrome with simultaneous amplification of the CGG-repeat region, the Sry gene and several flanking polymorphic markers. The amplification efficiency was > or =96% for all loci. The allele dropout rate in heterozygotic females was 9% for the FMR1 CGG-repeat region and 5-10% for the polymorphic markers. Amplification failure for Sry occurred in 5% of single leukocytes isolated from males. PGD was performed in six patients who underwent 15 cycles. Results were confirmed in all cases by amniocentesis or chorionic villous sampling. Five clinical pregnancies were obtained (31% per cycle), four of which resulted in a normal delivery and one miscarried. This technique is associated with high efficiency and accuracy and may be used in carriers of full mutations and unstable high-order premutations.

Screening oocytes by polar body biopsy

Preimplantation genetic aneuploidy screening performed by polar body biopsy has become a frequently used method, especially as in several countries only preconceptional genetic diagnosis is allowed. To penetrate the zona pellucida, mechanical, chemical and laser-assisted techniques have been introduced. In this paper, the advantages, disadvantages, efficacy and safety of these techniques are elucidated.

Place of preimplantation diagnosis in genetic practice

Preimplantation genetic diagnosis (PGD) is currently one of the practical options available for couples at-risk to avoid the birth of children with genetic and chromosomal disorders. Despite its novelty, PGD has already become an alternative to traditional prenatal diagnosis, allowing establishing only unaffected pregnancies avoiding the risk for pregnancy termination. Indications for PGD have currently expanded beyond those practices in prenatal diagnosis, such as late-onset diseases with genetic predisposition, and preimplantation HLA typing with the purpose of establishing potential donor progeny for stem cell treatment of siblings, which makes PGD also an important compliment to prenatal diagnosis. The fact that more than 1,000 apparently healthy unaffected children have been born after PGD suggests its accuracy, reliability, and safety. PGD is presently an excellent option for carriers of balanced translocations, and appears to be of special value for avoiding age-related aneuploidies in patients of advanced reproductive age. The accumulated experience of thousands of PGD cycles for poor prognosis in vitro fertilization (IVF) patients provides strong evidence of the improvement of clinical outcome, particularly obvious from the reproductive history of patients. This makes of practical relevance to inform couples at-risk about availability of PGD option, so they make their own choice in avoiding the birth of affected offspring and having healthy children of their own.

Preimplantation diagnosis: a realistic option for assisted reproduction and genetic practice

PURPOSE OF REVIEW

Preimplantation genetic diagnosis (PGD) allows genetically disadvantaged couples to reproduce, while avoiding the birth of children with targeted genetic disorders. By ensuring unaffected pregnancies, PGD circumvents the possible need and therefore risks of pregnancy termination. This review will describe the current progress of PGD for Mendelian and chromosomal disorders and its impact on reproductive medicine.

RECENT FINDINGS

Indications for PGD have expanded beyond those used in prenatal diagnosis, which has also resulted in improved access to HLA-compatible stem-cell transplantation for siblings through preimplantation HLA typing. More than 1000 apparently healthy, unaffected children have been born after PGD, suggesting its accuracy, reliability and safety. PGD is currently the only hope for carriers of balanced translocations. It also appears to be of special value for avoiding age-related aneuploidies in in-vitro fertilization patients who have a particularly poor prognosis for a successful pregnancy; the accumulated experience of thousands of PGD cycles strongly suggests that PGD can improve clinical outcome for such patients.

SUMMARY

PGD would particularly benefit poor prognosis in-vitro fertilization patients and other at-risk couples by improving reproductive outcomes and avoiding the birth of affected offspring.

Outcome of laser-assisted polar body biopsy and aneuploidy testing

Polar body biopsy and subsequent fluorescence in-situ hybridization (FISH) analysis allows detection of maternally derived chromosomal aneuploidies in human oocytes during IVF treatment. The development of a diode laser technique for the partial opening of the zona pellucida has stimulated the use of this technique to assist polar body biopsy. Laser-assisted polar body biopsy was performed in 140 IVF cycles from patients of advanced maternal age (> or =35 years). A total of 921 oocytes were treated by a laser for partial zona opening and polar body removal. FISH was performed for chromosomes 13, 16, 18, 21 and 22 and results were available for 903 oocytes (98%). In all, 443 oocytes (49.1%) were euploid and of these, 293 were fertilized. A total of 214 embryos were transferred in 120 embryo transfer cycles (1.78 per embryo transfer) resulting in 27 clinical pregnancies (22.5% per embryo transfer) with an implantation rate of 15.4%. Subsequently, five women aborted (18.5%) and 24 healthy children were born from the remaining 22 pregnancies, which gives a take home baby rate of 18.3% per transfer cycle. It is concluded that polar body biopsy using a diode laser system is as efficient as standard polar body biopsy using zona drilling.

A novel L1CAM mutation with L1 spectrum disorders

X-linked hydrocephalus, HSAS (hydrocephalus due to stenosis of aqueduct of Sylvius), MASA (mental retardation, aphasia, shuffling gait, and adducted thumbs), and CRASH (corpus callosum hypoplasia, retardation, adducted thumbs, spastic paraplegia, and hydrocephalus) syndromes are allelic disorders. X-linked hydrocephalus and associated phenotypes are due to mutations in the L1CAM gene, which has been identified as a coding neural cell adhesion molecule. We report two cases of L1 spectrum disorders within the same family. The first case was diagnosed by ultrasonographic examination prenatally and the second case was diagnosed postnatally. Both patients and their mothers carry a novel mutation of the L1CAM gene. In this family, nine X-linked hydrocephalus and five female carriers were found in three generations, and molecular genetic analysis was performed to detect the asymptomatic carriers.

The role of preimplantation genetic diagnosis in women of advanced reproductive age

PURPOSE OF REVIEW

More than half of in-vitro fertilization patients are of advanced reproductive age and at risk for producing offspring with age-related aneuploidies, which contribute significantly to spontaneous abortions and implantation failure.

RECENT FINDINGS

Fluorescent in-situ hybridization analysis of thousands of oocytes and preimplantation embryos obtained from these patients revealed an aneuploidy rate of over 50%, suggesting practical relevance of preimplantation genetic diagnosis for aneuploidy to women of advanced reproductive age. The overall preimplantation genetic diagnosis experience for age-related aneuploidies comprising more than 3000 clinical cycles indicates the positive impact of preselection and transfer of aneuploidy-free embryos on implantation and pregnancy rates and outcome of pregnancies in women of advanced reproductive age.

SUMMARY

These patients will need to be informed about preimplantation genetic diagnosis availability, in order use this option to improve their relatively poor chances of becoming pregnant, especially with the current tendency of limiting the number of transferred embryos to avoid complications due to multiple pregnancies. This may contribute significantly to improving standards of assisted reproduction technology, substituting the current practice of selection of embryos for transfer using morphological parameters with the preselection of aneuploidy-free embryos with a higher potential to result in pregnancy.

Current status of preimplantation diagnosis for single gene disorders

Preimplantation genetic diagnosis (PGD) has become an established procedure for avoiding the birth of affected children with single gene disorders. PGD is performed through polar body or blastomere biopsy, which has no deleterious effect on pre- and post-implantation development. This review describes the most recent developments and current changes in the spectrum of conditions for which PGD has been applied. The most recent applications of PGD include congenital malformations, blood group incompatibility and an increasing number of late onset disorders with genetic predisposition, all of which have not previously been diagnosed using PGD. Despite ethical concerns, PGD has also been used for preselection of unaffected and HLA matched embryos, and recently for preimplantation HLA matching without testing for the causative gene. This extends the practical value of PGD, with its utility being no longer limited to prevention of single gene disorders, by expanding it to treatment of siblings requiring stem cell transplantation.

Preimplantation genetic diagnosis

Preimplantation genetic diagnosis (PGD) is an evolving technique that provides a practical alternative to prenatal diagnosis and termination of pregnancy for couples who are at substantial risk of transmitting a serious genetic disorder to their offspring. Samples for genetic testing are obtained from oocytes or cleaving embryos after in vitro fertilization. Only embryos that are shown to be free of the genetic disorders are made available for replacement in the uterus, in the hope of establishing a pregnancy. PGD has provided unique insights into aspects of reproductive genetics and early human development, but has also raised important new ethical issues about assisted human reproduction.