PGD for cystic fibrosis patients and couples at risk of an additional genetic disorder combined with 24-chromosome aneuploidy testing.

Preimplantation genetic diagnosis (PGD) for inherited disorders is presently applied for more than 300 different conditions. The most frequent PGD indication is cystic fibrosis (CF), the largest series of which is reviewed here, totalling 404 PGD cycles. This involved testing for 52 different CFTR mutations with almost half of the cases (195/404 cycles) performed for ΔF508 mutation, one-quarter (103/404 cycles) for six other frequent mutations and only a few for the remaining 45 CFTR mutations. There were 44 PGD cycles performed for 25 CF-affected homozygous or double-heterozygous CF patients (18 male and seven female partners), which involved testing simultaneously for three mutations, resulting in birth of 13 healthy CF-free children and no misdiagnosis. PGD was also performed for six couples at a combined risk of producing offspring with CF and another genetic disorder. Concomitant testing for CFTR and other mutations resulted in birth of six healthy children, free of both CF and another genetic disorder in all but one cycle. A total of 96 PGD cycles for CF were performed with simultaneous aneuploidy testing, including microarray-based 24-chromosome analysis, as a comprehensive PGD for two or more conditions in the same biopsy material.

PGD for inherited cardiac diseases.

Preimplantation genetic diagnosis (PGD) has been applied for more than 200 different inherited conditions, with expanding application to common disorders with genetic predisposition. One of the recent indications for PGD has been inherited cardiac disease, for which no preclinical diagnosis and preventive management may exist and which may lead to premature or sudden death. This paper presents the first, as far as is known, cumulative experience of PGD for inherited cardiac diseases, including familial hypertrophic and dilated cardiomyopathy, cardioencephalomyopathy and Emery-Dreifuss muscular dystrophy. A total of 18 PGD cycles were performed, resulting in transfer in 15 of them, which yielded nine unaffected pregnancies and the births of seven disease- or disease predisposition-free children. The data open the prospect of PGD for inherited cardiac diseases, allowing couples carrying cardiac disease predisposing genes to reproduce without much fear of having offspring with these genes, which are at risk for premature or sudden death. Preimplantation genetic diagnosis (PGD) is currently an established clinical procedure in assisted reproduction and genetic practices. Its application has been expanding beyond traditional indications of prenatal diagnosis and currently includes common disorders with genetic predisposition, such as inherited forms of cancer. This applies also to the diseases with no current prospect of treatment, which may manifest despite presymptomatic diagnosis and follow up, when PGD may provide the only relief for the at-risk couples to reproduce. One of the recent indications for PGD has been inherited cardiac disease, for which no preclinical diagnosis and preventive management may exist and which may lead to premature or sudden death. We present here our first cumulative experience of PGD for inherited cardiac diseases, including familial hypertrophic and dilated cardiomyopathy, cardioencephalomyopathy and Emery-Dreifuss muscular dystrophy. A total of 18 PGD cycles for these disorders was performed, resulting in transfer in 15 of them, which yielded nine unaffected pregnancies and birth of seven disease- or disease predisposition-free children. The data open the prospect of PGD for inherited cardiac diseases, allowing couples carrying cardiac disease predisposing genes to reproduce without much fear of having offspring with these genes at risk for premature or sudden death.

Polar body-based preimplantation genetic diagnosis for Mendelian disorders.

Introduced >20 years ago, the use of polar bodies (PBs), involving sequential removal and genetic analysis of the first (PB1) and second (PB2) PB, provides the option for pre-embryonic diagnosis, when the objection to the embryo biopsy procedures makes preimplantation genetic diagnosis (PGD) non-applicable. PB-based approach has presently been utilized in PGD for genetic and chromosomal disorders, applied either separately, or together with embryo biopsy approaches, especially if there are two or more PGD indications. We present here the world's largest experience of 938 PGD cycles for single-gene disorders performed by PB testing for 146 different monogenic conditions, which resulted in the birth of 345 healthy children (eight pregnancies are still ongoing), providing strong evidence that PB-based PGD is a reliable and safe procedure, with an extremely high accuracy rate of over 99%. With application of microarray technology, PB-based approach will be utilized for increasing number of indications, involving simultaneous testing for 24 chromosomes and single-gene disorders.

Meiosis errors in over 20,000 oocytes studied in the practice of preimplantation aneuploidy testing.

This study presents the world's largest series of over 20,000 oocytes tested for aneuploidies, involving chromosomes 13,16, 18, 21 and 22, providing the data on the rates and types of aneuploidies and their origin. Almost every second oocyte (46.8%) is abnormal, with predominance of extra chromatid errors predicting predominance of trisomies (53%) over monosomies (26%) in the resulting embryos (2:1), which is opposite to monosomy predominance observed in embryo testing. Of the detected anomalies in oocytes, 40% are complex, so testing for a few most prevalent chromosome errors may allow detection of the majority of abnormal embryos. Chromosome 21 and 22 errors are more prevalent, while two different patterns of error origin were observed for different chromosomes: chromosome 16 and 22 errors originate predominantly from meiosis II, compared with chromosome 13, 18 and 21 errors originating from meiosis I. This provides the first evidence for the differences in the aneuploid embryo survival depending on the meiotic origin. Considering the problem of mosaicism, which is the major limitation of the cleavage-stage testing, the direct oocyte aneuploidy testing by polar body analysis may be of obvious practical value in improving accuracy and reliability of avoiding aneuploid embryos for transfer.

First systematic experience of preimplantation genetic diagnosis for de-novo mutations.

Standard preimplantation genetic diagnosis (PGD) cannot be applied for de-novo mutations (DNM), because neither origin nor relevant haplotypes are available for testing in single cells. PGD strategies were developed for 80 families with 38 genetic disorders, determined by 33 dominant, three recessive and two X-linked DNM. All three recessive mutations were of paternal origin, while of 93 dominant mutations, 40 were paternal, 46 maternal and seven detected in affected children. The development of specific PGD strategy for each couple involved DNA analysis of the parents and affected children prior to PGD, including a mutation verification, polymorphic marker evaluation, whole and single sperm testing to establish the normal and mutant haplotypes and PGD by polar body analysis and/or embryo biopsy. Overall, 151 PGD cycles were performed for 80 families, for which a specific PGD design has been established. The application of these protocols resulted in pre-selection and transfer of 219 (1.72 per cycle) DNM-free embryos in 127 (84.1%) PGD cycles, yielding 63 (49.6%) unaffected pregnancies and birth of 59 (46.5%) healthy children, confirmed to be free of DNM. The data show feasibility of PGD for DNM, which may routinely be performed with accuracy of over 99%, using the established PGD strategy.

Preimplantation genetic diagnosis for hemoglobinopathies.

Hemoglobinopathies are the most frequent indications for preimplantation genetic diagnosis (PGD), allowing couples at-risk of bearing offspring with thalassemia and sickle cell disease to reproduce without fear of having an affected child. The present experience includes PGD for sickle cell disease, α- and ß-thalassemia (α- and ß-thal). We present here the results of the world's largest experience of over 395 PGD cycles for hemoglobin (Hb) disorders, resulting in the birth of 98 healthy, hemoglobinopathy-free children, with seven pregnancies still ongoing. One-third of these cases were performed in combination with HLA typing, allowing the birth of unaffected children who were also HLA identical to the affected siblings with hemoglobinopathies in these families, with successful or pending stem cell transplantation in a dozen of them. The results show that PGD is presently a practical approach for prevention of hemoglobinopathies, gradually also becoming a useful approach to improving access to HLA-compatible stem cell transplantation for this group of diseases.

Conversion and non-conversion approach to preimplantation diagnosis for chromosomal rearrangements in 475 cycles.

Due to the limitations of preimplantation genetic diagnosis (PGD) for chromosomal rearrangements by interphase fluorescent in-situ hybridization (FISH) analysis, a method for obtaining chromosomes from single blastomeres was introduced by their fusion with enucleated or intact mouse zygotes, followed by FISH analysis of the resulting heterokaryons. Although this allowed a significant improvement in the accuracy of testing of both maternally and paternally derived translocations, it is still labour intensive and requires the availability of fertilized mouse oocytes, also creating ethical issues related to the formation of interspecies heterokaryons. This method was modified with a chemical conversion procedure that has now been clinically applied for the first time on 877 embryos from PGD cycles for chromosomal rearrangements and has become the method of choice for performing PGD for structural rearrangements. This is presented within the context of overall experience of 475 PGD cycles for translocations with pre-selection and transfer of balanced or normal embryos in 342 (72%) of these cycles, which resulted in 131 clinical pregnancies (38%), with healthy deliveries of 113 unaffected children. The spontaneous abortion rate in these cycles was as low as 17%, which confirms an almost five-fold reduction of spontaneous abortion rate following PGD for chromosomal rearrangements.

Single-Molecule Sequencing: A New Approach for Preimplantation Testing and Noninvasive Prenatal Diagnosis Confirmation of Fetal Genotype.

We investigated the potential of next-generation sequencing (NGS) as an alternative method for preimplantation genetic testing of monogenic disease (PGT-M) with human leukocyte antigen (HLA) matching and for noninvasive prenatal diagnosis follow-up. The case involved parents who were carriers of the Fanconi anemia complementation group G (FANCG) 260delG mutation. After clinical PGT using conventional short tandem repeat and mutation analysis, two euploid disease-free embryos were transferred, resulting in a twin pregnancy. Using the original embryo whole genome amplification products from 10 embryos, NGS confirmed the genotypes of the eight nontransferred embryos for both mutation status and HLA combination. NGS also confirmed that the two transferred embryos, which resulted in a twin pregnancy, were euploid, Fanconi disease free, and HLA matched to their sick sibling. At 15 weeks' gestation, noninvasive prenatal diagnosis of the maternal cell-free DNA determined fetal fractions of 14% and 6.6% for twins 1 and 2, respectively. The maternal plasma FANCG 260delG mutation ratio was measured at 46.2%, consistent with the presence of a carrier fetus and a normal fetus. These findings provide proof of concept that NGS has clinical utility as a safe and effective PGT-M method for embryo genotyping as well as more complex direct HLA matching. In addition, NGS can be used to confirm the original PGT-M and HLA matching embryo results in early pregnancy without the need for invasive prenatal diagnosis.

Impact of meiotic and mitotic non-disjunction on generation of human embryonic stem cell lines.

At least 50-60% of oocytes derived from IVF procedures are chromosomally abnormal due to meiotic I or II errors. Through the use of polar body and blastomere diagnosis, euploid embryos suitable for transfer can be identified. Those embryos that are aneuploid are usually discarded, or otherwise can be used to generate chromosomally abnormal human embryonic stem cell (hESC) lines. The authors' centre has one of the largest repositories of hESC lines with genetic and chromosomal disorders generated from preimplantation genetic diagnosis (PGD) abnormal embryos. The results, studying hESC lines derived from PGD abnormal zygotes, imply that aneuploidies resulting from meiotic non-disjunction have a greater impact on viability of cells of the human embryos than those originating from post-zygotic mitotic non-disjunction.

Before the beginning: the genetic risk of a couple aiming to conceive.

Disorders of genetic etiology exist in 2%-3% of live-born infants. Identifying couples with increased susceptibility for offspring with anomalies or genetic disorders is increasingly effective as a result of molecular advances. Preimplantation genetic testing (PGT) with the use of trophectoderm biopsy, 24-chromosome testing, and molecular testing have allowed wider applicability for avoiding a clinical pregnancy termination. Cell-free DNA in maternal blood is another targeted option, although invasive prenatal genetic diagnosis provides the greatest amount of genetic information. DNA-based methods to detect subtle chromosomal abnormalities are much more sensitive than traditional karyotypes and do not require cultured cells. Aneuploidy and structural chromosomal abnormalities can be readily detected with the use of small amounts of DNA, if necessary amplified, as in PGT. Novel approaches exist for detecting perturbations in single-gene disorders. Not only has the molecular basis for many monogenic disorders been elucidated, but modest costs for DNA sequencing has made testing feasible. As the number of testable genetic disorders has increased, principles underlying screening have advanced. Genetic screening for disorders of high incidence in certain ethnic groups was initiated decades ago; however, limitations exist, and reduction in live-born incidence is not infrequently small. Expanded carrier screening is now offered in panethnic fashion, extending surveillance to couples of mixed ethnicities and involving many more genetic conditions. Targeted gene panels (e.g., adult-onset cancer genes) further increase the number of genetic disorders amenable to screening, often leading to PGT.

Overview of Preimplantation Genetic Diagnosis (PGD): Historical Perspective and Future Direction.

Preimplantation genetic diagnosis (PGD) can be considered the earliest form of prenatal testing. It was first used in humans over 26 years ago. At its inception, PGD could only be performed for a limited number of genetic disorders. Technological advances in molecular biology and cytogenomics have been utilized in the field of PGD to greatly expand the spectrum of genetic disorders that can now be detected in early human embryos.

Preimplantation genetic testing: current challenges and future prospects.

INTRODUCTION: Preimplantation genetic testing (PGT) is now a widely applied procedure in genetic practices and ART, with more than one third of ART Centers in US already utilizing PGT technology. Its indications have also been significantly extended to include common late-onset disorders and non-genetic conditions, such as testing for HLA match. Areas covered: This is a critical review of the developments in PGT, with emphasis on their outstanding limitations and directions for the future research and practice in the area of PGT. Expert commentary: The application of the new higher resolution PGT technologies has led to the identification of genetic variations, the biological and clinical importance of which is not sufficiently understood. It is obvious that the current selection process of embryos with the highest developmental potential requires a further improvement, as significant proportion of transferred euploid embryos still fail to result in an ongoing clinical pregnancy. More research will be needed to upgrade PGT for different conditions into a single universal test in the same biopsy material. To avoid a potential damage of embryo biopsy procedures, one of the important challenges will be the development of non-invasive approaches to PGT.

Cytoplasmic cell fusion: Stembrid technology for reprogramming pluripotentiality.

Recent progress in somatic cell nuclear transfer (SCNT) provides the evidence for the presence of reprogramming factors in human embryonic stem cells (hESC). Hybrid hESC with donor human somatic nuclei have been established, but the resulting hybrid hESC contained DNA originating from both hESC and donor somatic cells. There is still no method to completely replace the hESC nuclei by the nuclei of somatic cells and to obtain the pure colonies of hESC with donor genotype. We present here the original technology, which is based on enucleation of h ESC and their fusion with the adult somatic cells, resulting in the establishment of individual-specific hESC with the genotype of the donor somatic cells. The resulting constructs was demonstrated to have the "stemness" of hESC and the genotype of the donor somatic cells. So this "Stembrid technology," may be used for the construction of patient-specific hESC.

Preimplantation genetics: Improving access to stem cell therapy.

There has been progress in the application of stem cell transplantation for treatment of an increasing number of severe congenital and acquired bone marrow disorders, currently restricted by the availability of human leukocyte antigen (HLA)-matched related donors. Preimplantation HLA typing has recently been introduced to improve the access to stem cell therapy for inherited bone marrow failures. Preimplantation genetic diagnosis (PGD) provides an option not only for avoiding an affected pregnancy with thalassemia and other inherited disorders but also for preselection of the HLA-compatible donors for affected siblings. Multiple short tandem repeat markers throughout the HLA region are applied for this purpose, allowing 100% accuracy of HLA typing, through picking up possible recombination in the HLA region, as well as the copy number of chromosome 6, which affect accuracy of preimplantation HLA typing. Present experience of preimplantation HLA typing includes preimplantation HLA typing in 180 cycles, 122 of which were done as part of PGD for Fanconi anemia, thalassemia, Wiscott-Aldrich syndrome, hyper-immunoglobulin M syndrome, hypohidrotic ectodermal dysplasia with immune deficiency, and X-linked adrenoleukodystrophy, and 58 for the sole purpose of HLA typing for leukemias and for aplastic and Diamond-Blackfan anemia. The applied method resulted in the accurate preselection and transfer of 100% HLA-matched embryos, yielding already three dozen clinical pregnancies and the birth of two dozen HLA-matched children to the siblings requiring stem cell transplantation. Successful therapy with HLA-matched stem cells, obtained from these PGD children, has been achieved already for Diamond-Blackfan anemia hypohidrotic ectodermal dysplasia with immune deficiency and thalassemia.

First systematic experience of preimplantation genetic diagnosis for single-gene disorders, and/or preimplantation human leukocyte antigen typing, combined with 24-chromosome aneuploidy testing.

OBJECTIVE: To study the feasibility, accuracy, and reproductive outcome of 24-chromosome aneuploidy testing (24-AT), combined with preimplantation genetic diagnosis (PGD) for single-gene disorders (SGDs) or human leukocyte antigen (HLA) typing in the same biopsy sample. DESIGN: Retrospective study. SETTING: Preimplantation genetic diagnosis center. PATIENT(S): A total of 238 PGD patients, average age 36.8 years, for whom 317 combined PGD cycles were performed, involving 105 different conditions, with or without HLA typing. INTERVENTION(S): Whole-genome amplification product, obtained in 24-AT, was used for PGD and/or HLA typing in the same blastomere or blastocyst biopsy samples. MAIN OUTCOME MEASURE(S): Proportion of the embryos suitable for transfer detected in these blastomere or blastocyst samples, and the resulting pregnancy and spontaneous abortion rates. RESULT(S): Embryos suitable for transfer were detected in 42% blastocyst and 25.1% blastomere samples, with a total of 280 unaffected, HLA-matched euploid embryos detected for transfer in 212 cycles (1.3 embryos per transfer), resulting in 145 (68.4%) unaffected pregnancies and birth of 149 healthy, HLA-matched children. This outcome is significantly different from that of our 2,064 PGD cycle series without concomitant 24-AT, including improved pregnancy (68.4% vs. 45.4%) and 3-fold spontaneous abortion reduction (5.5% vs. 15%) rates. CONCLUSION(S): The introduced combined approach is a potential universal PGD test, which in addition to achieving extremely high diagnostic accuracy, significantly improves reproductive outcomes of PGD for SGDs and HLA typing in patients of advanced reproductive age.

Preimplantation diagnosis for diseases with genetic predisposition and nondisease testing.

Preimplantation genetic diagnosis has become a method of choice in genetic practices. The present experience includes thousands of clinical cases of preimplantation genetic diagnosis, demonstrating the safety, accuracy and reliability of the technique and its clinical relevance for those at-risk couples who cannot accept traditional methods for prenatal diagnosis and termination of pregnancy. Most recently, preimplantation genetic diagnosis has been performed for late-onset disorders, such as genetic predisposition to cancers, Alzhelmer's disease and nondisease testing involving human leukocyte antigen typing, never practiced in prenatal diagnosis. The review of these developments suggests the clinical usefulness of this new approach for avoiding the birth of children with genetic predisposition to cancers and other late-onset disorders, or preimplanation human leukocyte antigen matching to provide the treatment of the affected siblings requiring bone marrow transplantation.

Preimplantation diagnosis for long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency.

Long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) deficiency is a fatal autosomal recessive metabolic disorder, presenting during infancy. Preimplantation genetic diagnosis (PGD) provides an option for establishing an unaffected pregnancy, avoiding the risk for termination of pregnancy following prenatal diagnosis. The method for pre-selection of mutation-free oocytes for LCHAD deficiency was developed by testing the first and second polar body removed from oocytes by micromanipulation techniques in the framework of in-vitro fertilization. To avoid misdiagnosis, testing was done using hemi-nested polymerase chain reaction (PCR), with outer primers designed to lie outside the pseudogene, eliminating false priming. Four of 12 tested oocytes were predicted to be unaffected, based on the heterozygous first and mutant second polar body. The embryos resulting from these mutation-free oocytes were replaced, yielding a singleton clinical pregnancy and birth of a healthy child following confirmation by prenatal diagnosis.

Preimplantation diagnosis for p53 tumour suppressor gene mutations.

Preimplantation genetic diagnosis (PGD) was introduced for high-risk couples to avoid establishing affected pregnancies potentially requiring termination following prenatal diagnosis. This opens the possibility for PGD for late onset disorders with genetic predisposition, including inherited cancer predisposition, because only embryos free from the predisposing gene may be transferred back to the patient, with no potential risk for pregnancy termination. PGD was performed for two couples, one with maternally and one with paternally derived p53 tumour-suppressor mutations, 902insC in exon 8 and G524A in exon 5, respectively. This involved a standard IVF protocol, allowing oocytes or embryos to be tested prior to their transfer back to uterus. Maternal mutation was tested by sequential PCR analysis of the first and second polar bodies, removed following maturation and fertilization of oocytes, while paternal mutation analysis required embryo biopsy at the cleavage stage. To avoid misdiagnosis due to allele drop out, multiplex nested PCR was applied, involving p53 mutation analysis simultaneously with the linked short tandem repeats in intron 1. Of 10 oocytes tested in two PGD cycles for 902insC mutation, four unaffected oocytes were pre-selected for transfer yielding no clinical pregnancy. Of 18 embryos analysed in two cycles for G524A mutation, seven mutation-free embryos were detected, two of which were transferred in each cycle, resulting in a singleton pregnancy and birth of a mutation-free child. This is the first PGD for inherited cancer predisposition determined by p53 tumour suppressor mutations, resulting in a clinical pregnancy and birth of a child free from inherited cancer predisposition.

Preimplantation genetic diagnosis for the Kell genotype.

OBJECTIVE: To use preimplantation genetic diagnosis (PGD) to achieve a Kell 1 (K1) allele-free pregnancy in couples at risk for producing a child with hemolytic disease of the newborn (HDN) caused by maternofetal incompatibility in sensitized mothers. DESIGN: DNA analysis of biopsied blastomeres from cleavage-stage embryos in IVF-ET with the goal of identifying and transferring back to patients the K1 allele-free embryos. SETTING: IVF program at the Reproductive Genetics Institute, Chicago, Illinois, and IVF Michigan, Rochester Hills, Michigan. PATIENT(S): Two at-risk couples with a history of neonatal death caused by HDN due to K1/K2 genotype in a male partner. INTERVENTION(S): Biopsy of single blastomeres and testing for paternal K1 allele in each embryo after standard IVF. MAIN OUTCOME MEASURE(S): DNA analysis of blastomeres indicating whether corresponding embryos were K1 allele-free for the purpose of transferring only embryos without the K1 allele. RESULT(S): Of 36 embryos tested in five cycles from two couples, 18 were predicted to be K1 allele-free. Of these, 9 were transferred, resulting in a K1 allele-free twin pregnancy and the birth of two healthy children. CONCLUSION(S): PGD of the K1 genotype resulted in the birth of healthy twins confirmed to be free of the K1 allele. PGD in couples with a heterozygous K1/K2 male partner provides an option for avoiding HDN in sensitized mothers.