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

Preimplantation genetic testing for type 2 diabetes based on family-specific polygenic risk score: A proof-of-concept study

AIMS

This study aims to evaluate the feasibility of family-specific polygenic risk prediction in reducing the risk of type 2 diabetes (T2D) in the offspring from an infertile couple with a family history of early-onset T2D.

METHODS

We innovatively established a family-specific polygenic risk prediction model for this T2D family and the embryo with the lowest risk of T2D were selected for implantation.

RESULTS

Initially, whole exome sequencing analysis in the family failed to identify monogenic-level pathogenic or likely pathogenic variants responsible for T2D. Thus, preimplantation genetic testing for monogenic disease (PGT-M) may be not applicable. Subsequently, we innovatively developed a family-specific polygenic-level T2D risk prediction model including 114 T2D risk SNPs and weighted by the genotype-phenotype correlation of asymptomatic individuals and T2D patients in the pedigree. Using this model, the euploid embryo P_5977_1C exhibited the lowest T2D risk and was selected for implantation. The newborn displayed the same lowest T2D polygenic risk and normal growth and development after a 16-month follow-up.

CONCLUSION

Our study provided preliminary evidence for the feasibility of developing a more accurate polygenic risk prediction model using pedigree information and its application in embryo selection.

The correlation between blastocyst morphological parameters and chromosomal euploidy, aneuploidy and other chromosomal abnormalities following pre-implantation genetic testing-a single center retrospective study

PURPOSE

To examine the association between blastocyst morphology and chromosomal status utilizing pre-implantation genetic testing for aneuploidy (PGT-A).

METHODS

A single-center retrospective cohort study including 169 in-vitro fertilization cycles that underwent PGT-A using Next Generation Sequencing (2017-2022). Blastocysts were morphologically scored based on Gardner and Schoolcraft's criteria. Chromosomal analysis results included: euploid; aneuploid (single or double); segmental; mosaic; and complex (≥ 3 chromosome abnormalities). We examined associations between morphological parameters and chromosomal statuses of biopsied embryos utilizing multivariate logistic regression.

RESULTS

Overall, 855 blastocysts underwent PGT-A (PGT-A alone: N = 804; unaffected PGT for monogenic disease (PGT-M) embryos along with PGT-A: N = 51). Of these, 826 were successfully analyzed, with 321 euploid embryos (38.86%). Various morphological parameters (embryo quality, inner cell mass (ICM), trophectoderm (TE), and expansion stage) were more frequent within the double (n = 72, 8.72%), complex (n = 97, 11.74%), mosaic (n = 139, 16.83%), and segmental aneuploidy (n = 28, 3.39%) groups, with similar associations between different morphological parameters and single aneuploidy (n = 169, 20.46%). Utilizing multivariate logistic regression, higher expansion, embryo quality, and TE and ICM grades, were associated with increased odds of euploidy (versus non-euploidy). Higher expansion was a positive predictor of single versus double aneuploidy (aOR 2.94, 95% CI 1.52-5.56, p = 0.001); and higher ICM grade was a positive predictor of single versus complex aneuploidy (aOR 2.86, 95% CI 1.15-7.12, p = 0.024). No morphological parameter was found to be associated with single versus mosaic aneuploidy.

CONCLUSION

Various morphological parameters are associated with euploidy and different aneuploidy statuses of pre-implantation blastocysts. These findings may aid in the selection of the assumed best chromosomally structured blastocyst for transfer when PGT-A is not performed.

In vitro fertilization as an option for couples with genetic disorders

Errors in human DNA may cause genetic disorders. Technological developments have raised hopes for reducing the risks of genetic inheritance among married couples who have a history of such disorders. Among the developments in reproductive health technology that reduce those risks is the in vitro fertilization (IVF) process. This review aimed to describe the current strategies using IVF and preimplantation genetic testing (PGT), which would be effective for couples with genetic disorders to have healthy offspring. The literature review included full-text, open-access research articles from ScienceDirect, PubMed, and Google Scholar that were published between 2013 and 2023, with 65 articles obtained from various journals. The keywords were 'in vitro fertilization,' 'reproductive genetic disorders,' 'PGT-A,' 'PGT-M,' 'PGT-SR,' and 'oocyte donor.' A total of 46 articles were selected as the most relevant to the review topic, and the results show that the IVF process can be an option for couples with a history of genetic disorders. Several additional procedures can be performed following IVF, such as oocyte donation and PGT, to help couples who want to have offspring without transmitting their genetic disorders. IVF can be an option for couples who have or carry genetic disorders. With IVF, couples can undertake several procedures such as oocyte donation and PGT for aneuploidy, monogenic disorders, or structural rearrangement.

Case report: Successful PGT-M based on the identification of a spliceogenic variant in the RPGRIP1L gene through Minigene assay

With the development of high-throughput sequencing, the genetic etiology of many diseases has been revealed. However, this has also led to the categorization of many variants as variants of uncertain significance (VUSs), presenting a major challenge in genetic counseling. A couple with a history of adverse pregnancies sought assisted reproductive technology. Trio-WES revealed that they individually carried the following variants in the RPGRIP1L gene: a c.1581G>A (p.Gln527=) (VUS) and a c.135-11A>G (likely pathogenic variant, LP). Further investigation using the Minigene assay showed that the variant c.1581G>A (p.Gln527=) disrupts the normal splicing pattern of the mRNA, leading to two abnormal splicing modes: 1) retention of 26 bp in intron 13; 2) exon 13 skipping transcript. Consequently, the VUS was reclassified as likely pathogenic. We then performed preimplantation genetic testing (PGT) for the couple, which included direct detection of the RPGRIP1L locus, SNP haplotype analysis, and chromosome copy number detection. Through these precise detection procedures, an unaffected embryo was selected for transfer, and the prenatal genetic diagnosis of the fetus was normal. Our study indicates that the Minigene assay is a valuable tool for splicing functional analysis of variants in vitro. This approach is particularly useful for genetic counseling involving VUS that may affect pre-mRNA splicing, as well as for the subsequent clinical management of the related family.

A study on methods for preimplantation genetic testing (PGT) on in vivo- and in vitro-produced equine embryos, with emphasis on embryonic sex determination

Two methods for preimplantation genetic testing (PGT) have been described for equine embryos: trophoblast cell biopsy (TCB) or blastocoele fluid aspiration (BFA). While TCB is widely applied for both in vivo- and in vitro-produced embryos, BFA has been mostly utilized for in vivo-produced embryos. Alternative methods for PGT, including analysis of cell-free DNA (CFD) in the medium where in vitro-produced embryos are cultured, have been reported in humans but not for equine embryos. In Experiment 1, in vivo- (n = 10) and in vitro-produced (n = 13) equine embryos were subjected to BFA, cultured for 24 h, then subjected to TCB, and cultured for additional 24 h. No detrimental effect on embryonic diameter or re-expansion rates was observed for either embryo group (P > 0.05). In Experiment 2, the concordance (i.e., agreement on detecting the same embryonic sex using two techniques) among BFA, TCB, and the whole embryo (Whole) was studied by detecting the sex-determining region Y (SRY) or testis-specific y-encoded protein 1 (TSPY) (Y-chromosome), and androgen receptor (AR; X-chromosome) genes using PCR. Overall, a higher concordance for detecting embryonic sex was observed among techniques for in vivo-produced embryos (67-100 %; n = 14 embryos) than for in vitro-produced embryos (31-92 %; n = 13 embryos). The concordance between sample types increased when utilizing TSPY (77-100 %) instead of SRY (31-100 %) as target gene. In Experiment 3, CFD analysis was performed on in vitro-produced embryos to determine embryonic sex via PCR (SRY [Y-chromosome] and amelogenin - AMEL [X- and Y-chromosomes]). Overall, CFD was detected in all medium samples, and the concordance between CFD sample and the whole embryo was 60 % when utilizing SRY and AMEL genes. In conclusion, equine embryos can be subjected to two biopsy procedures (24 h apart) without apparent detrimental effects on embryonic size. For in vivo-, but not for in vitro-produced equine embryos, BFA can be considered a potential alternative to TCB for PGT. Finally, CFD can be further explored as a non-invasive method for PGT in in vitro produced equine embryos.

Ready for polygenic risk scores? An analysis of regulation of preimplantation genetic testing in European countries

STUDY QUESTION

Would the different regulatory approaches for preimplantation genetic testing (PGT) in Europe permit the implementation of preimplantation genetic testing using polygenic risk scores (PGT-P)?

SUMMARY ANSWER

While the regulatory approaches for PGT differ between countries, the space provided for potential implementation of PGT-P seems limited in all three regulatory models.

WHAT IS KNOWN ALREADY

PGT is a reproductive genetic technology that allows the testing for hereditary genetic disorders and chromosome abnormalities in embryos before implantation. Throughout its history, PGT has largely been regarded as an ethically sensitive technology. For example, ethical questions have been raised regarding the use of PGT for adult-onset conditions, non-medical sex selection, and human leukocyte antigen typing for the benefit of existing siblings. Countries in which PGT is offered each have their own approach of regulating the clinical application of PGT, and a clear overview of legal and practical regulation of PGT in Europe is lacking. An emerging development within the field of PGT, namely PGT-P, is currently bringing new ethical tensions to the forefront. It is unclear whether PGT-P may be applied within the current regulatory frameworks in Europe. Therefore, it is important to investigate current regulatory frameworks in Europe and determine whether PGT-P fits within these frameworks.

STUDY DESIGN, SIZE, DURATION

The aim of this study was to provide an overview of the legal and practical regulation of the use of PGT in seven selected European countries (Belgium, France, Germany, Italy, the Netherlands, Spain, and the UK) and critically analyse the different approaches with regards to regulatory possibilities for PGT-P. Between July and September 2023, we performed a thorough and extensive search of websites of governments and governmental agencies, websites of scientific and professional organizations, and academic articles in which laws and regulations are described.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We investigated the legal and regulatory aspects of PGT by analysing legal documents, regulatory frameworks, scientific articles, and guidelines from scientific organizations and regulatory bodies to gather relevant information about each included country. The main sources of information were national laws relating to PGT.

MAIN RESULTS AND THE ROLE OF CHANCE

We divided the PGT regulation approaches into three models. The regulation of PGT differs per country, with some countries requiring central approval of PGT for each new indication (the medical indication model: the UK, the Netherlands), other countries evaluating each individual PGT request at the local level (the individual requests model: France, Germany), and countries largely leaving decision-making about clinical application of PGT to healthcare professionals (the clinical assessment model: Belgium, Italy, Spain). In the countries surveyed that use the medical indication model and the individual requests model, current legal frameworks and PGT criteria seem to exclude PGT-P. In countries using the clinical assessment model, the fact that healthcare professionals and scientific organizations in Europe are generally negative about implementation of PGT-P due to scientific and socio-ethical concerns, implies that, even if it were legally possible, the chance that PGT-P would be offered in the near future might be low.

LIMITATIONS, REASONS FOR CAUTION

The results are based on our interpretation of publicly available written information and documents, therefore not all potential discrepancies between law and practice might have been identified. In addition, our analysis focuses on seven-and not all-European countries. However, since these countries are relevant players within PGT in Europe and since they have distinct PGT regulations, the insights gathered give relevant insights into diverse ways of PGT regulation.

WIDER IMPLICATIONS OF THE FINDINGS

To the best of our knowledge, this is the first paper that provides a thorough overview of the legal and practical regulation of PGT in Europe. Our analysis of how PGT-P fits within current regulation models provides guidance for healthcare professionals and policymakers in navigating the possible future implementation of PGT-P within Europe.

STUDY FUNDING/COMPETING INTEREST(S)

This project has received funding from the European Union's Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement no. 813707. The authors declare no conflict of interest.

TRIAL REGISTRATION NUMBER

N/A.

Evaluation of genetic risk of apparently balanced chromosomal rearrangement carriers by breakpoint characterization

PURPOSE

To report genetic characteristics and associated risk of chromosomal breaks due to chromosomal rearrangements in large samples.

METHODS

MicroSeq, a technique that combines chromosome microdissection and next-generation sequencing, was used to identify chromosomal breakpoints. Long-range PCR and Sanger sequencing were used to precisely characterize 100 breakpoints in 50 ABCR carriers.

RESULTS

In addition to the recurrent regions of balanced rearrangement breaks in 8q24.13, 11q11.23, and 22q11.21 that had been documented, we have discovered a 10-Mb region of 12q24.13-q24.3 that could potentially be a sparse region of balanced rearrangement breaks. We found that 898 breakpoints caused gene disruption and a total of 188 breakpoints interrupted genes recorded in OMIM. The percentage of breakpoints that disrupted autosomal dominant genes recorded in OMIM was 25.53% (48/188). Fifty-four of the precisely characterized breakpoints had 1-8-bp microhomologous sequences.

CONCLUSION

Our findings provide a reference for the evaluation of the pathogenicity of mutations in related genes that cause protein truncation in clinical practice. According to the characteristics of breakpoints, non-homologous end joining and microhomology-mediated break-induced replication may be the main mechanism for ABCRs formation.

Chinese experts' consensus guideline on preimplantation genetic testing of monogenic disorders

Recent developments in molecular biological technologies and genetic diagnostic methods, accompanying with updates of relevant terminologies, have enabled the improvements of new strategies of preimplantation genetic testing for monogenic (single gene) disorders (PGT-M) to prevent the transmission of inherited diseases. However, there has been much in the way of published consensus on PGT-M. To properly regulate the application of PGT-M, Chinese experts in reproductive medicine and genetics have jointly developed this consensus statement. The consensus includes indications for patient selection, genetic and reproductive counseling, informed consent, diagnostic strategies, report generation, interpretation of results and patient follow-ups. This consensus statement serves to assist in establishment of evidence-based clinical and laboratory practices for PGT-M.

Preimplantation genetic testing for Aicardi-Goutières syndrome induced by novel compound heterozygous mutations of TREX1: an unaffected live birth

BACKGROUND

Aicardi-Goutières syndrome (AGS) is a rare, autosomal recessive, hereditary neurodegenerative disorder. It is characterized mainly by early onset progressive encephalopathy, concomitant with an increase in interferon-α levels in the cerebrospinal fluid. Preimplantation genetic testing (PGT) is a procedure that could be used to choose unaffected embryos for transfer after analysis of biopsied cells, which prevents at-risk couples from facing the risk of pregnancy termination.

METHODS

Trio-based whole exome sequencing, karyotyping and chromosomal microarray analysis were used to determine the pathogenic mutations for the family. To block the inheritance of the disease, multiple annealing and looping-based amplification cycles was used for whole genome amplification of the biopsied trophectoderm cells. Sanger sequencing and next-generation sequencing (NGS)-based single nucleotide polymorphism (SNP) haplotyping were used to detect the state of the gene mutations. Copy number variation (CNV) analysis was also carried out to prevent embryonic chromosomal abnormalities. Prenatal diagnosis was preformed to verify the PGT outcomes.

RESULTS

A novel compound heterozygous mutation in TREX1 gene was found in the proband causing AGS. A total of 3 blastocysts formed after intracytoplasmic sperm injection were biopsied. After genetic analyses, an embryo harbored a heterozygous mutation in TREX1 and without CNV was transferred. A healthy baby was born at 38th weeks and prenatal diagnosis results confirmed the accuracy of PGT.

CONCLUSIONS

In this study, we identified two novel pathogenic mutations in TREX1, which has not been previously reported. Our study extends the mutation spectrum of TREX1 gene and contributes to the molecular diagnosis as well as genetic counseling for AGS. Our results demonstrated that combining NGS-based SNP haplotyping for PGT-M with invasive prenatal diagnosis is an effective approach to block the transmission of AGS and could be applied to prevent other monogenic diseases.

Segmental aneuploidies with 1 Mb resolution in human preimplantation blastocysts

PURPOSE

This study aimed to investigate the spectrum and characteristics of segmental aneuploidies (SAs) of <10 megabase (Mb) length in human preimplantation blastocysts.

METHODS

Preimplantation genetic testing for aneuploidy was performed in 15,411 blastocysts from 5171 patients using a validated 1 Mb resolution platform. The characteristics and spectrum of SAs, including the incidence, sizes, type, inheritance pattern, clinical significance, and embryo distribution, were studied.

RESULTS

In total, 6.4% of the 15,411 blastocysts carried SAs of >10 Mb, 4.9% of embryos had SAs ranging between 1 to 10 Mb, and 84.3% of 1 to 10 Mb SAs were <5 Mb in size. Inheritance pattern analysis indicated that approximately 63.8% of 1 to 10 Mb SAs were inherited and were predominantly 1 to 3 Mb in size. Furthermore, 18.4% of inherited SAs and 51.9% de novo 1 to 10 Mb SAs were pathogenic or likely pathogenic (P/LP). Different from whole-chromosome aneuploidies, reanalysis indicated that 50% of the de novo 1 to 10 Mb SAs and 70% of the >10 Mb SAs arose from mitotic errors.

CONCLUSION

Based on the established platform, 1 to 10 Mb SAs are common in blastocysts and include a subset of P/LP SAs. Inheritance pattern analysis and clinical interpretation based on the American College of Medical Genetics and Genomics/Association for Molecular Pathology guidelines contributed to determine the P/LP SAs.

Frequency of embryos appropriate for transfer following preimplantation genetic testing for monogenic disease

PURPOSE

To identify specific likelihoods that an embryo will be classified as appropriate for transfer after preimplantation genetic testing for detection of a monogenic disorder (PGT-M), with or without preimplantation genetic testing for aneuploidy (PGT-A), separated by inheritance pattern.

METHODS

Retrospective chart review of 181 selected PGT-M cycles performed at CooperGenomics in 2018 or 2019. For each cycle, the following main outcome data was collected: the number of embryos classified as affected with monogenic disease, the number detected to be chromosomally abnormal, the number that were recombinant, the number that had no result, and if applicable, the number which were aneuploid.

RESULTS

There were significantly fewer embryos appropriate to consider for transfer when PGT-A was included for autosomal recessive and X-linked disorders. There were also fewer for autosomal dominant disorders, though this was not statistically significant. When PGT-A was not included, 45.8% of autosomal dominant, 69% of autosomal recessive, and 47.8% of X-linked embryos were appropriate to consider for transfer. When PGT-A analysis was included, 29% of autosomal dominant, 41% of autosomal recessive, and 22% of X-linked embryos were appropriate to consider for transfer. 96.8% of women elect to include PGT-A when pursuing PGT-M.

CONCLUSION

This study resulted in specific likelihoods that an embryo would be found appropriate for clinicians and patients to consider for transfer based on the inheritance pattern of the monogenic disease being tested for and whether aneuploidy analysis was included.

Comparative study on risk of birth defects in singleton ART birth under high levels of estrogen after fresh embryo transfer and frozen embryo transfer

OBJECTIVE

To investigate whether high estrogen (E2) levels caused by controlled ovarian hyperstimulation affect the birth defect rate in singleton assisted reproductive technology (ART) birth after conceived by fresh embryo transfer and frozen embryo transfer (FET).

METHODS

This was a retrospective cohort study. A total of 581 women with singletons, as well as those who have become pregnant and have had an unwanted abortion under high E2 levels on trigger day were divided into three groups. Group A received FET and the E2 levels on trigger day were higher than 5000 pg/ml. Group B received fresh embryo transfer and the E2 levels were between 3000 and 5000 pg/ml. Group C received FET and the E2 levels were between 3000 and 5000 pg/ml.

RESULTS

There were no significant differences in birth weight, delivery mode, preterm birth rate, and fetal sex between the three groups (p > .05). Birth defect rate in Group B was higher than that in Group A and C, and the rate between Group B and C had significant differences (p < .05). After adjusting for maternal age, BMI, and type of infertility, only a FET cycle is significantly associated with decreased birth defect rate.

CONCLUSION

Fresh embryo transfer under supraphysiological level of estrogen exposure may increase the birth defect rate of ART singletons. Even after prenatal screening and diagnosis, a part of birth defect could not be detected during pregnancy. When the estrogen levels on trigger day were no lower than 3000 pg/ml, FET should be advocated to reduce the occurrence of such risk.

Decision-making and experiences of preimplantation genetic diagnosis in inherited heart diseases: a qualitative study

Preimplantation genetic diagnosis (PGD) ensures a disease-causing variant is not passed to the next generation, including for inherited heart diseases. PGD is known to cause significant emotional burden, but little is known about how parents experience PGD to select against inherited heart disease. We aim to understand how people with inherited heart disease, and their partners, experience and make decisions about PGD. Participants were recruited from a specialised inherited heart disease clinic. Qualitative semi-structured interviews were conducted with adult participants who had considered PGD. A semi-structured interview schedule explored overall experiences and reasons for undergoing PGD. Broad topics included experience of disease, reproductive history, psychosocial and financial considerations. Interviews were recorded, transcribed verbatim and thematically analysed using a framework method. Twenty participants were included (15 with inherited cardiomyopathy, 3 with inherited arrhythmia syndrome and 2 partners). In contemplating PGD, participants considered 3 main issues: past experience of disease e.g. sudden cardiac death, sport restrictions and clinical heterogeneity; intergenerational responsibilities; and practical considerations such as finances and maternal age. Among those who chose to undergo PGD (n = 7/18), past experience of a significant cardiac event, such as family history of sudden cardiac death, was important in the decision process. The decision to undergo PGD for inherited heart disease is complex and influenced by individual values and experience of disease. We highlight key areas where further discussion may assist in PGD decision processes.

Preimplantation Genetic Diagnosis for DEB by Detecting a Novel Family-Specific COL7A1 Mutation in Vietnam

Background

Epidermolysis bullosa (EB) is a disorder characterized by the appearance of blisters, erosions and wounds in response to minimal trauma. The disease manifests with noticeable symptoms ranging from mild to severe, classified into four major types: epidermolysis bullosa simplex (EBS), junctional epidermolysis bullosa (JEB), dystrophic epidermolysis bullosa (DEB) and Kindler syndrome. Preimplantation genetic diagnosis for the disease remains the only available option for families at risk for the recurrence of the disorder without having to terminate an ongoing pregnancy.

Materials and Methods

A novel COL7A1 mutation was used to design primers for the polymerase chain reaction (PCR) to amplify the segment spanning the mutation in the family and their in-vitro fertilization (IVF) embryos. Then, the PCR products were sequenced with Sanger sequencing to detect the alteration in the allele, and some embryos would go through NGS-based preimplantation screening for chromosomal abnormalities.

Results

The established protocol for EB detected mutant allele in 6/9 embryos (66.6%), while the remaining 3 embryos (33.4%) appeared to not carry any mutation. Only one among 3 embryos was recommended to be transferred into the mother's uterus.

Conclusion

The established preimplantation genetic diagnosis procedure is helpful to families affected by epidermolysis bullosa caused by COL7A1 mutations but wish to have healthy children.

Preimplantation Genetic Testing: A Perceptual Study From the Eastern Province, Saudi Arabia

Background: Chromosomal abnormalities affect many children which lead to high rates of morbidity and mortality among them. So, preimplantation genetic testing (PGT) is an evolving technology used to detect a specific genetic disorder in embryos of a couple known to be carriers or affected by a specific mutation. Similarly, it could be used in advanced maternal age which is a high risk of chromosomal abnormalities. Although PGT is a solution for many inherited chromosomal disorders, many ethical dilemmas surround its application. Thus, the aim of this study is to evaluate the community awareness and acceptance of PGT which will eventually lead to a healthier society through disease-free babies in Eastern Province, Kingdom of Saudi Arabia (KSA).

Methodology: A qualitative cross-sectional questionnaire-based study was conducted within the population of the Eastern Province of Saudi Arabia. The questionnaire was designed in Arabic and distributed electronically through social media platforms.

Results: The study included 837 participants, whose ages ranged from 18 to 65 years with the mean age 33.5 ± 11.9 years. Good awareness and acceptance were detected among 53.7% of the old aged group (50 years or more) compared to 39.5% of the young age group. Also, 44.9% of female participants had good awareness in comparison to 34.2% of males (p=.033). Participants with a higher number of children had significantly higher awareness and acceptance of PGT. Also, 44.3% of participants who knew someone in need of assisted reproductive technology, had good awareness and acceptance levels compared to 36.9% of those who did not (p=.033).

Conclusion: The perception of Eastern Province’s Saudi citizens toward PGT is found to be low. Increasing their perception toward such technology is needed as it is known that many chromosomal abnormalities are prevalent among this population, particularly sickle cell disease. Achieving this goal will eventually lead to decrease the burden of prevalent inherited diseases. Since Saudis' opinions are almost influenced by cultural and religious points of view, care should be given to these aspects.

An Introduction: Prenatal Screening, Diagnosis, and Treatment of Single Gene Disorders

Increasing ability to diagnose fetal single gene disorders has changed the prenatal diagnostic paradigm. As fetal sequencing advances, the genomic information obtained can lead to improved prognostic counseling, and elucidation of recurrence risk and future prenatal diagnosis options. For some of these disorders, postnatal molecular therapy, including gene therapy, is available or being studied in clinical trials. Most of the initial research and clinical trials have involved children and adults, but there are potential benefits to treating conditions before birth. Many clinical studies are underway exploring the potential for in utero gene therapy.

Expanded clinical validation of Haploseek for comprehensive preimplantation genetic testing

PURPOSE

We previously developed Haploseek, a method for comprehensive preimplantation genetic testing (PGT). However, some key features were missing, and the method has not yet been systematically validated.

METHODS

We extended Haploseek to incorporate DNA from embryo grandparents and to allow testing of variants on chromosome X or in regions where parents share common haplotypes. We then validated Haploseek on 151 embryo biopsies from 27 clinical PGT cases. We sequenced all biopsies to low coverage (0.2×), and performed single-nucleotide polymorphism (SNP) microarray genotyping on the embryos' parents and siblings/grandparents. We used the extended Haploseek to predict chromosome copy-number variants (CNVs) and relevant variant-flanking haplotypes in each embryo. We validated haplotype predictions for each clinical sample against polymerase chain reaction (PCR)-based PGT case results, and CNV predictions against established commercial kits.

RESULTS

For each of the 151 embryo biopsies, all Haploseek-derived haplotypes and CNVs were concordant with clinical PGT results. The cases included 17 autosomal dominant, 5 autosomal recessive, and 3 X-linked monogenic disorders. In addition, we evaluated 1 Robertsonian and 2 reciprocal translocations, and 17 cases of chromosome copy-number counting were performed.

CONCLUSION

Our results demonstrate that Haploseek is clinically accurate and fit for all standard clinical PGT applications.

Reproductive outcomes after preimplantation genetic testing in mosaic Turner syndrome: a retrospective cohort study of 100 cycles

PURPOSE

The purpose of this study is to explore the reproductive outcomes of women with Turner syndrome (TS) in preimplantation genetic testing (PGT) cycles.

METHODS

A retrospective study of 100 controlled ovarian stimulating cycles, 68 TS (sixty-four mosaic Turner syndrome (MTS) and four pure Turner syndrome (PTS)) women underwent PGT was conducted from 2013 to 2018.

RESULTS

Embryo X chromosome abnormal rates of TS women were significantly higher than women with normal karyotype (7.04 vs 1.61%, P<0.01). Cumulative live birth rates (CLBR) after PGT-NGS treatment were lower in TS than control (31.15 vs 45.59%, P<0.05). Clinical pregnancy rates per transfer (CPR), miscarriage rates (MR) and live birth rates per transfer (LBR) remained comparable between TS and control group. Reproductive outcomes (X chromosome abnormal rates, CPR, MR, LBR and CLBR) among low (<10%), medium (10-50%) and high (>50%) level 45,X mosaicism groups were not statistically different.

CONCLUSIONS

To avoid high risk of embryo X chromosome abnormalities, prenatal or preimplantation genetic testing should be recommended to mosaic or pure TS patients.

Review: Preimplantation genetic diagnosis (PGD) as a reproductive option in patients with neurodegenerative disorders

Preimplantation genetic diagnosis (PGD) was introduced in the late 1980s and represents an option for couples at risk of transmitting an inherited, debilitating or neurological disorder to their children. From a cleavage or blastocyst stage embryo, cell(s) are collected and then genetically analyzed for disease; enabling an unaffected embryo to be transferred into the uterus cavity. Nowadays, PGD has been carried out for several hundreds of heritable conditions including myotonic dystrophy, and for susceptibility genes involved in cancers of the nervous system. Currently, advanced molecular technologies with better resolution, such as array comparative genomic hybridisation, quantitative polymerase chain reaction, and next generation sequencing, are on the verge of becoming the gold standard in embryo preimplantation screening. Given this, it may be time for neurological societies to consider the published evidence to develop new guidelines for the integration of PGD into modern preventative neurology. Therefore, the main aim of this review is to illustrate the option of PGD to enable conception of an unaffected baby, and to assist clinicians and neurologists in the counseling of the patient at risk of transmitting an inherited disease, to explore the genetic journey throughout in vitro fertilization IVF with PGD.

Ante-natal counseling in phacomatoses

OBJECTIVES

Phacomatoses are a group of neuro-oculo-cutaneous syndromes/ neurocutaneous disorders, involving structures arising from the embryonic ectoderm. Most of phacomatoses including the most common ones:, neurofibromatosis type I and type II (NF1, NF2) and tuberosclerosis complex (TSC), are autosomal dominant genetic disorders with full penetrance and variable expression. As no effective treatment exists, the only way to prevent the disease, is by prenatal genetic diagnosis (either chorionic villus sampling-CVS or amniocentesis-AC) and termination of pregnancy or performing preimplantation genetic testing (PGT). As the risk for an affected offspring is 50% in every pregnancy of an affected parent, prenatal, and preimplantation testing are of great importance. However, those procedures are associated with technical and ethical concerns. This chapter shortly reviews the common phacomatoses emphasizes their genetics and inheritance. We will review the common methods for prenatal and preimplantation diagnoses and discuss its use in common phacomatoses.

CONCLUSION

Phacomatoses are common autosomal dominant genetic conditions with variable expression. Ante-natal genetic diagnosis is an appropriate approach for family planning in individuals affected by phacomatosis or parents of an affected child.

Disruptive Synergy: Melding of Human Genetics and Clinical Assisted Reproduction

The melding of human genetics with clinical assisted reproduction, now all but self-evident, gave flight to diagnostic and therapeutic approaches previously deemed infeasible. Preimplantation genetic diagnosis, mitochondrial replacement techniques, and remedial germline editing are particularly noteworthy. Here we explore the relevant disruption brought forth by coalescence of these mutually enabling disciplines with the regulatory and legal implications thereof.

Utility and First Clinical Application of Screening Embryos for Polygenic Disease Risk Reduction

For over 2 decades preimplantation genetic testing (PGT) has been in clinical use to reduce the risk of miscarriage and genetic disease in patients with advanced maternal age and risk of transmitting disease. Recently developed methods of genome-wide genotyping and machine learning algorithms now offer the ability to genotype embryos for polygenic disease risk with accuracy equivalent to adults. In addition, contemporary studies on adults indicate the ability to predict polygenic disorders with risk equivalent to monogenic disorders. Existing biobanks provide opportunities to model the clinical utility of polygenic disease risk reduction among sibling adults. Here, we provide a mathematical model for the use of embryo screening to reduce the risk of type 1 diabetes. Results indicate a 45-72% reduced risk with blinded genetic selection of one sibling. The first clinical case of polygenic risk scoring in human preimplantation embryos from patients with a family history of complex disease is reported. In addition to these data, several common and accepted practices place PGT for polygenic disease risk in the applicable context of contemporary reproductive medicine. In addition, prediction of risk for PCOS, endometriosis, and aneuploidy are of particular interest and relevance to patients with infertility and represent an important focus of future research on polygenic risk scoring in embryos.