Preimplantation genetic diagnosis of human embryos for Marfan's syndrome

Pre-implantation genetic testing for Marfan syndrome using mini-sequencing

Marfan syndrome (MFS1) is an autosomal dominant condition causing aortopathy including fatal aortic dissection. This study aimed to perform clinical PGT-M in a family with a history of MFS1 for two generations. A family with two members affected by MFS1 approached the hospital for PGT-M. The couple decided to join the project following extensive counselling and informed consent was obtained. The mutation contributory to MFS1 was identified using whole-exome sequencing (WES). A novel PGT-M protocol using multiplex fluorescent PCR and mini-sequencing was developed and tested. Ten blastocysts were subjected to PGT-M in two clinical PGT cycles. Mini-sequencing revealed four normal and six affected embryos. Microsatellite-based linkage analysis confirmed mutation analysis results in all samples. The embryos diagnosed as normal (non-MFS1) were chosen for transfer. A pregnancy was obtained in the third embryo transfer. Invasive prenatal diagnosis confirmed the normal genotype of the baby. This study demonstrated comprehensive management using the application of clinical-based diagnosis, WES for mutation identification within the MFS1 gene, mini-sequencing for embryo selection and microsatellite-based linkage analysis for backup of PGT-M results and contamination detection to assist couples in having a healthy child when there was a family history of Marfan syndrome.Impact StatementWhat is already known on this subject? Marfan syndrome (MFS1, OMIM#154700) is an autosomal dominant condition causing aortopathy including fatal aortic dissection. Pre-implantation genetic testing (PGT) is an alternative to traditional invasive prenatal diagnosis (PND) giving the couples the chance of starting pregnancy with the confidence that the baby will be unaffected. Most of the previous PGT reports employed microsatellite-based linkage analysis. A few PGT studies used sequencing, mini-sequencing and mutation analysis; however, the details of the techniques were not described.What do the results of this study add? Single-cell PCR protocol using multiplex fluorescent PCR and mini-sequencing was developed and validated. Two clinical PGTs cycles for Marfan syndrome were performed. A healthy baby was resulted. The details of multiplex fluorescent PCR and mini-sequencing protocols are described in this study so that the procedures can be reproduced.What are the implications of these findings for clinical practice and/or further research? Embryo selection can help the family suffering from Marfan syndrome for two generations to start a pregnancy with confidence that their child will be unaffected. This study also shows the use of a mini-sequencing protocol for PGT, which can be a universal protocol for other mutations by changing the PCR primers and mini-sequencing primers.

De Novo Paternal FBN1 Mutation Detected in Embryos Before Implantation

Background

Marfan syndrome (MFS) is an autosomal dominant disease caused by mutations in the Fibrillin (FBN)1 gene and characterized by disorders in the cardiovascular, skeletal, and visual systems. The diversity of mutations and phenotypic heterogeneity of MFS make prenatal molecular diagnoses difficult. In this study, we used pre-implantation genetic diagnosis (PGD) to identify the pathogenic mutation in a male patient with MFS and to determine whether his offspring would be free of the disease.

Material/Methods

The history and pedigree of the proband were analyzed. Mutation analysis was performed on the couple and immediate family members. The couple chose IVF treatment and 4 blastocysts were biopsied. PGD was carried out by targeted high-throughput sequencing of the FBN1 gene in the embryos, along with single-nucleotide polymorphism haplotyping. Sanger sequencing was used to confirm the causative mutation.

Results

c.2647T>C (p.Trp883Arg) was identified as the de novo likely pathogenic mutation in the proband. Whole-genome amplification and sequencing of the 3 embryos revealed that they did not carry the mutation, and 1 blastocyst was transferred back to the uterus. The amniocentesis test result analyzed by Sanger sequencing confirmed the PGD. A premature but healthy infant free of heart malformations was born.

Conclusions

The de novo mutation c.2647T>C (p.Trp883Arg) in FBN1 was identified in a Chinese patient with MFS. Embryos without the mutation were identified by PGD and resulted in a successful pregnancy.

Five years’ experience of preimplantation genetic diagnosis in the Parisian Center: outcome of the first 441 started cycles

OBJECTIVE

To investigate the evolution of techniques and strategies and to evaluate the results of preimplantation genetic diagnosis (PGD) from January 2000 to December 2004 in chromosomal, monogenic and mitochondrial DNA disorders treated at our institution.

DESIGN

Retrospective study.

SETTING

Single French Parisian PGD center.

PATIENT(S)

Patients at risk of transmitting a serious genetic disorder to their offspring.

INTERVENTION(S)

171 couples enrolled in the program undergoing stimulated and frozen embryo replacement cycles with PGD.

MAIN OUTCOME MEASURE(S)

Results of the 441 first PGD cycles performed for various genetic conditions.

RESULT(S)

During 5 years, 416 stimulation and 25 frozen embryo replacement cycles were started, among which 52 clinical and 47 ongoing pregnancies occurred. In stimulation cycles, the overall ongoing pregnancy rate was 24% per embryo transfer, 11% per started cycle, and 27% per couple. The implantation rate was 16%.

CONCLUSION(S)

These encouraging results demonstrate that PGD might be considered as a valid alternative to prenatal diagnosis. Nevertheless, couples referred for PGD must be selected and counseled appropriately, considering the complexity of the treatment and the relatively low take-home baby rate.

Preimplantation genetic diagnosis for Marfan syndrome

OBJECTIVE

To develop and apply efficient and reliable protocols for preimplantation genetic diagnosis (PGD) for Marfan syndrome.

DESIGN

Two mutation-specific protocols were developed, and the markers D15S1028, D15S992, D15S196, D15S576, D15S123, and D15S143 were used to set up four multiplex polymerase chain reactions (PCRs).

SETTING

Research Center Reproduction and Genetics.

PATIENT(S)

Ten couples carrying mutations in the FBN1 gene.

INTERVENTION(S)

Six PGD protocols were developed for 10 couples, and 7 of them underwent a total of 16 clinical cycles.

MAIN OUTCOME MEASURE(S)

Amplification, allele drop-out (ADO), and contamination rates during the preclinical assays. DNA analyses of blastomeres from embryos biopsied during PGD cycles.

RESULT(S)

Six different protocols were set up, with the main objective being to to use one protocol for several couples. A total of 16 PGD cycles were performed, which resulted in the delivery of an unaffected boy and three ongoing pregnancies.

CONCLUSION(S)

The development of single-cell multiplex PCRs for linked markers and its use in PGD reduce the workload of the genetic diagnostic laboratory as well as the average waiting time for patients. This approach also allows for the simultaneous and accurate detection of recombination, contamination, and ADO, thereby increasing the reliability of the diagnosis.

Indications et résultats du diagnostic pré-implantatoire (DPI)

OBJECTIVE

To report the results of preimplantation genetic diagnosis (PGD) cycles performed in our unit from 2000 to 2004. Materials and methods. One hundred and seventy-one couples were enrolled in the PGD program over this period. The collected oocytes were inseminated by intracytoplasmic sperm injection (ICSI). The resulting embryos were biopsied on the third day of development and the genetic analysis was performed on the same day. Embryo transfers were carried out on the fourth day.

RESULTS

The 416 stimulation cycles started yielded 280 oocyte pick-ups, 3506 oocytes retrieved, of which 2966 were suitable for ICSI. Among the 1982 embryos obtained, 1337 embryos were biopsied and genetic diagnosis was performed for 1083 (81%) of them. 381 embryos were transferred during the course of 189 transfer procedures. There were 51 clinical and 46 ongoing (35 single, 11 twin) pregnancies. In addition, 25 frozen embryo replacement cycles were initiated, leading to 6 embryo transfers and 1 ongoing pregnancy. A total of 58 unaffected children were born.

CONCLUSION

PGD has gained a place among the choices offered to couples at risk of transmission of a serious and incurable genetic disease. It might be a realistic alternative to prenatal diagnosis for patients carrier of chromosomal rearrangements, single gene defects, X-linked disesases or mitochondrial DNA disorders.

Preimplantation genetic diagnosis

Preimplantation genetic diagnosis (PGD) was introduced at the beginning of the 1990s as an alternative to prenatal diagnosis, to prevent termination of pregnancy in couples with a high risk for offspring affected by a sex-linked genetic disease. At that time, embryos obtained in vitro were tested to ascertain their sex, and only female embryos were transferred. Since then, techniques for genetic analysis at the single-cell level, involving assessment of first and second polar bodies from oocytes or blastomeres from cleavage-stage embryos, have evolved. Fluorescence in-situ hybridisation (FISH) has been introduced for the analysis of chromosomes and PCR for the analysis of genes in cases of monogenic diseases. In-vitro culture of embryos has also improved through the use of sequential media. Here, we provide an overview of indications for, and techniques used in, PGD, and discuss results obtained with the technique and outcomes of pregnancies. A brief review of new technologies is also included.

Comparison between fluorescence in situ hybridization (FISH) and quantitative-fluorescent polymerase chain reaction (QF-PCR) for the detection of aneuploidies in single blastomeres

OBJECTIVES

The aim of our investigation was to compare the efficiencies of the fluorescence in situ hybridization (FISH) and the quantitative-fluorescent PCR (QF-PCR) methods for the detection of sexing and numerical chromosome disorders in single blastomeres collected from the same preimplantation human embryos.

METHODS

FISH analysis was carried out on 145 blastomeres from the 79 surplus embryos with probes specific for chromosomes 13, 18, 21, X, and Y. QF-PCR was performed with each one or two of the primers specific for the same chromosomes on 151 blastomeres from the same embryos obtained from patients undergoing IVF treatment.

RESULTS

Analyses were possible on 135 blastomeres (93%) by FISH and on 117 blastomeres (77%) by QF-PCR. Of 65 embryos, which could be analyzed by both methods, 20 embryos (31%) were diagnosed as abnormal.

CONCLUSION

The present study shows that FISH tests are more accurate than QF-PCR assays for the detection of numerical chromosome disorders when performed on single blastomeres.

Pre-implantation genetic diagnosis

Pre-implantation genetic diagnosis is an alternative to prenatal diagnosis for a select group of patients. Patients have to go through in vitro fertilization in order to produce embryos in vitro, from which one or two cells are removed at the 8-cell stage. A fluorescence in situ hybridization or polymerase chain reaction is carried out for the genetic diagnosis. Fluorescence in situ hybridization is used for the analysis of chromosomes for sexing for X-linked disease, chromosome abnormalities and aneuploidy screening. Aneuploidy screening is performed for infertile patients going through in vitro fertilization to try to improve their pregnancy rate. A polymerase chain reaction is used for the diagnosis of single-gene disorders. Since the risk of contamination and allele dropout is high with a polymerase chain reaction, linked or unlinked markers are usually used in a fluorescent multiplex polymerase chain reaction. New techniques, for example comparative genomic hybridization, allow the analysis of all of the chromosomes from one cell at one time. The ethical implications of pre-implantation genetic diagnosis are immense as the technique has already been used for social sexing and human leukocyte antigen matching.

Living with Marfan syndrome III. Quality of life and reproductive planning

As individuals with Marfan syndrome are increasingly diagnosed earlier in life and prior to life-threatening cardiovascular events, there is opportunity to study factors that influence their reproductive planning and quality of life. In this study of 174 affected adults, the overall quality of life was reported to be adequate, although it was significantly decreased within the spiritual/psychological domain. Approximately 62% agreed that having Marfan syndrome significantly affected their reproductive decision-making. This view was correlated with age of diagnosis, mitral valve prolapse, and the view that Marfan syndrome has adverse consequences on life. Sixty-nine percent reported personal interest in prenatal testing for Marfan syndrome. Respondents most commonly cited increased worries about personal health and the recurrence risk as ways that Marfan syndrome affects their reproductive decisions. Age, striae, back pain, and low quality of life were each independently correlated with lack of sex drive. These results affirm the importance of both clinical and psychosocial issues on affected adults' reproductive decision-making and sexual well-being. Genetic professionals are ideally positioned to discuss concerns about quality of life and reproduction with patients with Marfan syndrome and refer those with significant concerns for further evaluation and management.

Preimplantation genetic diagnosis: applications for molecular medicine

Preimplantation genetic diagnosis is an alternative to prenatal diagnosis for the detection of genetic disorders. Tests are conducted on single cells biopsied from embryos before they are implanted, allowing the selection of unaffected embryos before a pregnancy has been established. Thus, the issue of pregnancy termination is circumvented. The use of preimplantation genetic diagnosis might have a significant impact on in vitro fertilization success rates as well as allowing the diagnosis of inherited disease.

Pre-implantation genetic diagnosis

Pre-implantation genetic diagnosis (PGD) was developed in the UK over 10 years ago. There are now more than 40 centres worldwide carrying out PGD and 150 babies have been born after genetic testing on day 3 of development, at the cleavage stage. This review covers the current status of PGD, the technology used and the types of genetically determined diseases for which testing has been developed.

Preimplantation genetic diagnosis

Embryo biopsy for preimplantation genetic diagnosis can be performed on the oocyte/zygote, cleavage stage embryo, or blastocyst, but the majority of centres perform cleavage stage biopsy. Single-cell diagnosis is undertaken by the polymerase chain reaction or fluorescent in-situ hybridization. Technical difficulties have arisen with preimplantation genetic diagnosis, such as allele dropout and chromosomal mosaicism. However, it is hoped that these difficulties can be overcome in the future with the advent of new techniques.