Preimplantation genetic diagnosis in Saudi Arabia

Preimplantation genetic diagnosis (PGD) testing is the practice of obtaining a cellular biopsy sample from a developing human oocyte or embryo, acquired via a cycle of in vitro fertilization (IVF); evaluating the genetic composition of this sample; and using this information to determine which embryos will be optimal for subsequent uterine transfer. PGD has become an increasingly useful adjunct to IVF procedures. The ability to provide couples who are known carriers of genetic abnormalities the opportunity to deliver healthy babies has opened a new frontier in reproductive medicine. The purpose of the PGD is enables us to choose which embryos will be implanted into the mother. In the present study 137 families who had undergone IVF at Habib Medical Centre, were enrolled for the PGD analysis. The couple visited the clinic for the sex selection, recurrent fetal loss and with the recurrent IVF failure. 802 embryos were tested by the biopsy method and 512 are found to be normal and 290 were abnormal embryos. In this study only 24% of the embryos were transferred and the remaining was not transferred because of the abnormalities or undesired sex of the embryos. The structural and numerical abnormalities were found to be 16.8%.     

植入前遗传学诊断的原理、方法及适应症

植入前遗传学诊断是一种非常早的产前诊断,指在胚胎着床之前即对配子或胚胎的遗传物质进行分析,检测配子或胚胎是否有遗传物质异常,选择正常胚胎进行移植。与传统的产前诊断相比,能避免选择性流产异常妊娠给妇女带来的心身痛苦。本文就该领域的发展及现状和其诊断原理、方法及适应症进行了总结和综述。 Abstract:Preimplatation genetic diagnosis (PGD) is a very early form of prenatal diagnosis.Gametes or embryos are biopsied and a genetic diagnosis is carried out on the biopsied cells to investigate if the gametes or embryos is free of genetic disease.And the normal embryos is transferred to the mother.Comparing to the traditional prenatal diagnosis,PGD is a method that can avoid aborting a abnormal pregnant and reduce pains of women.In this review,we introduce the history of development and statues in quo,principle,method and application of PGD.     

从植入前遗传学诊断异常的胚胎中分离人胚胎干细胞系

在体外受精过程中,通过胚胎植入前遗传性诊断（PGD）对有遗传风险患者的胚胎进行植入前活检和遗传学分析,选择无遗传性疾病的胚胎植入子宫,而PGD诊断异常的胚胎则会被丢弃。本研究尝试将PGD异常胚胎用于分离人胚胎干细胞,以获得携带遗传缺陷的人胚胎干细胞系。利用荧光原位杂交技术对第3-5天胚胎进行PGD检测,结果异常的胚胎进一步用于分离获取胚胎干细胞系,然后对h ES细胞系进行核型及干细胞表面标记、多能性基因表达、端粒酶活性以及分化能力等特征性鉴定。总共从13个PGD异常胚胎中分离获得8个人胚胎干细胞系,建系效率为61.5%,其中1个核型正常,5个核型异常。说明利用PGD异常胚胎可以获得携带遗传缺陷的人胚胎干细胞系,不仅为评估PGD技术临床结论的准确性提供了一种新方法,更重要的是为研究各种遗传性疾病的发病机理提供了有效的细胞模型。     

Derivation of new human embryonic stem cell lines from preimplantation genetic screening and diagnosis-analyzed embryos

In this study, we focused on the derivation of human embryonic stem cell (hESC) from preimplantation genetic screening (PGS)-analyzed and preimplantation genetic diagnosis (PGD)-analyzed embryos. Out of 62 fresh PGD/PGS-analyzed embryos, 22 embryos reached the blastocyst stage. From 12 outgrowth blastocysts, we derived four hESC lines onto a feeder layer. Surprisingly, karyotype analysis showed that hESC lines derived from aneuploid embryos had diploid female karyotype. One hESC line was found to carry a balanced Robertsonian translocation. All the cell lines showed hESC markers and had the pluripotent ability to differentiate into derivatives of the three embryonic germ layers. The established lines had clonal propagation with 22–31% efficiency in the presence of ROCK inhibitor. These results further indicate that hESC lines can be derived from PGD/PGS-analyzed embryos that are destined to be discarded and can serve as an alternative source for normal euploid lines.     

Risk,parental autonomy and the epistemic divide: preimplantation genetic diagnosis in the Australian print news media, 1990–2007

Preimplantation genetic diagnosis (PGD) is a reproductive/genetic technology which has become the subject of public and scholarly debate because it involves the evaluation and consequent selection (and implantation) or destruction of human embryos. This research investigates the way PGD is constituted in the Australian print news media. Foucauldian discourse analysis reveals that proponents draw on their direct knowledge and experience of PGD to support their claims. There is an epistemic divide between consumers and others claiming direct knowledge, and critics and others drawing on indirect or abstract understandings of PGD. This divide characterizes the discourses present in the data and is directly linked to changes in these over the period under analysis.     

Preimplantation genetic diagnosis: State of the ART 2011

For the last 20 years, preimplantation genetic diagnosis (PGD) has been mostly performed on cleavage stage embryos after the biopsy of 1–2 cells and PCR and FISH have been used for the diagnosis. The main indications have been single gene disorders and inherited chromosome abnormalities. Preimplantation genetic screening (PGS) for aneuploidy is a technique that has used PGD technology to examine chromosomes in embryos from couples undergoing IVF with the aim of helping select the chromosomally ‘best’ embryo for transfer. It has been applied to patients of advanced maternal age, repeated implantation failure, repeated miscarriages and severe male factor infertility. Recent randomised controlled trials (RCTs) have shown that PGS performed on cleavage stage embryos for a variety of indications does not improve delivery rates. At the cleavage stage, the cells biopsied from the embryo are often not representative of the rest of the embryo due to chromosomal mosaicism. There has therefore been a move towards blastocyst and polar body biopsy, depending on the indication and regulations in specific countries (in some countries, biopsy of embryos is not allowed). Blastocyst biopsy has an added advantage as vitrification of blastocysts, even post biopsy, has been shown to be a very successful method of cryopreserving embryos. However, mosaicism is also observed in blastocysts. There have been dramatic changes in the method of diagnosing small numbers of cells for PGD. Both array-comparative genomic hybridisation and single nucleotide polymorphism arrays have been introduced clinically for PGD and PGS. For PGD, the use of SNP arrays brings with it ethical concerns as a large amount of genetic information will be available from each embryo. For PGS, RCTs need to be conducted using both array-CGH and SNP arrays to determine if either will result in an increase in delivery rates.     

Multiple displacement amplification for preimplantation genetic diagnosis of fragile X syndrome

Preimplantation genetic diagnosis (PGD) has become an assisted reproductive technique for couples that have genetic risks. Despite the many advantages provided by PGD, there are several problems, including amplification failure, allele drop-out and amplification inefficiency. We evaluated multiple displacement amplification (MDA) for PGD of the fragile X syndrome. Whole genome amplification was performed using MDA. MDA products were subjected to fluorescent PCR of fragile X mental retardation-1 (FMR1) CGG repeats, amelogenin and two polymorphic markers. In the pre-clinical tests, the amplification rates of the FMR1 CGG repeat, DXS1215 and FRAXAC1 were 84.2, 87.5 and 75.0%, respectively, while the allele dropout rates were 31.3, 57.1 and 50.0%, respectively. In two PGD treatment cycles, 20 embryos among 30 embryos were successfully diagnosed as 10 normal embryos, four mutated embryos and six heterozygous carriers. Three healthy embryos were transferred to the uterus; however, no clinical pregnancy was achieved. Our data indicate that MDA and fluorescent PCR with four loci can be successfully applied to PGD for fragile X syndrome. Advanced methods for amplification of minuscule amounts of DNA could improve the sensitivity and reliability of PGD for complicated single gene disorders.     

Advances in preimplantation genetic diagnosis/screening

Preimplantation genetic diagnosis (PGD) gives couples who have a high risk of transmitting genetic disorders to their baby the chance to have a healthy offspring through embryo genetic analysis and selection. Preimplantation genetic screening (PGS) is an effective method to select euploid embryos that may prevent repeated implantation failure or miscarriage. However, how and to whom PGS should be provided is a controversial topic. The first successful case of PGD of a human being was reported in 1990, and there have been tremendous improvements in this technology since then. Both embryo biopsy and genetic technologies have been improved dramatically, which increase the accuracy and expand the indications of PGD/PGS.     

‘Saviour Siblings’? The Distinction between PGD with HLA Tissue Typing and Preimplantation HLA Tissue Typing

One of the more controversial uses of preimplantation genetic diagnosis (PGD) involves selecting embryos with a specific tissue type so that the child to be born can act as a donor to an existing sibling who requires a haematopoietic stem cell transplant. PGD with HLA tissue typing is used to select embryos that are free of a familial genetic disease and that are also a tissue match for an existing sibling who requires a transplant. Preimplantation HLA tissue typing occurs when parents select embryos that are not at risk of a familial genetic disease to be a match for an existing sibling who requires a transplant. In Victoria, Australia, applications to use PGD with HLA tissue typing are reviewed by the Infertility Treatment Authority on a case by case basis. Preimplantation HLA tissue typing is prohibited prima facie because the embryo to be tested would not be at risk for a genetic abnormality or disease. Arguments for or against the use of PGD/HLA tissue typing are based on several key issues including the commodification and welfare of the donor child. This essay aims to show that that the same arguments apply to both PGD with HLA tissue typing and Preimplantation HLA tissue typing, and that the policy distinction between the two procedures is therefore ethically inconsistent.     

Cytogenetics in reproductive medicine: the contribution of comparative genomic hybridization (CGH)

Cytogenetic research has had a major impact on the field of reproductive medicine, providing an insight into the frequency of chromosomal abnormalities that occur during gametogenesis, embryonic development and pregnancy. In humans, aneuploidy has been found to be relatively common during fetal life, necessitating prenatal screening of high-risk pregnancies. Aneuploidy rates are higher still during the preimplantation stage of development. An increasing number of IVF laboratories have attempted to improve pregnancy rates by using preimplantation genetic diagnosis (PGD) to ensure that the embryos transferred to the mother are chromosomally normal. This paper reviews some of the techniques that are key to the detection of aneuploidy in reproductive samples including comparative genomic hybridization (CGH). CGH has provided an unparalleled insight into the nature of chromosome imbalance in human embryos and polar bodies. The clinical application of CGH for the purposes of PGD and the future extensions of the methodology, including DNA microarrays, are discussed.     

Refining the ethics of preimplantation genetic diagnosis: A plea for contextualized proportionality

Many European countries uphold a ‘high risk of a serious condition’ requirement for limiting the scope of preimplantation genetic diagnosis (PGD). This ‘front door’ rule should be loosened to account for forms of PGD with a divergent proportionality. This applies to both ‘added PGD’ (aPGD), as an add‐on to in vitro fertilization (IVF), and ‘combination PGD’ (cPGD), for a secondary disorder in addition to the one for which the applicants have an accepted PGD indication. Thus loosening up at the front has implications at the back of PGD treatment, where a further PGD rule says that ‘affected embryos’ (in the sense of embryos with the targeted mutation or abnormality) should not be transferred to the womb. This ‘back door’ rule should be loosened to allow for transferring ‘last chance’ affected embryos in aPGD and cPGD cases, provided this does not entail a high risk that the child will have a seriously diminished quality of life.     

Eugenic Selection Benefits Embryos

The primary question to be addressed here is whether pre‐implantation genetic diagnosis (PGD), used for both negative and positive trait selection, benefits potential supernumerary embryos. The phrase ‘potential supernumerary embryos’ is used to indicate that PGD is typically performed on a set of embryos, only some of which will be implanted. Prior to any testing, each embryo in the set is potentially supernumerary in the sense that it may not be selected for implantation. Those embryos that are not selected, and hence destroyed or frozen, are ‘actually supernumerary’. The argument to be advanced is hypothetical: If embryos may be said to benefit or be harmed by our actions, then PGD used to select for an embryo or embryos with the highest expected Wellbeing benefits potential supernumerary embryos. The argument shows that the ‘non‐identity’ problem is not sufficient to show that eugenic selection does not benefit supernumerary embryos.     

Meiotic recombinations within major histocompatibility complex of human embryos

We studied the rate and pattern of recombinations within the extended major histocompatibility complex (MHC) locus of the human embryos obtained during preimplantation genetic diagnosis (PGD) for HLA compatibility. Recombinant allele frequency was on average 5.33?%, and recombination rate was 0.44?cM/Mb in the 12.2?Mb of the extended MHC locus. Recombination rate varied up to 14-fold (0.19–2.73?cM/Mb) between cases, and maternal recombination rate was on average 3.8 times higher than paternal alleles. More than 69?% of the recombination hot spots were clustered within the extended class II region where the recombination rate was 5.4 times more than that in extended class I region. These findings indicate the potential of PGD to study the mechanisms of linkage disequilibrium within MHC locus of human embryos, demonstrate the recombination characteristics within extended MHC loci of human embryos in comparison to sperm and family studies, and point to the significance of design and interpretation of PGD for HLA compatibility to avoid misdiagnosis because of meiotic recombinations.     

Procreative beneficence: why we should select the best children

Eugenic selection of embryos is now possible by employing in vitro fertilization (IVF) and preimplantation genetic diagnosis (PGD). While PGD is currently being employed for the purposes of detecting chromosomal abnormalities or inherited genetic abnormalities, it could in principle be used to test any genetic trait such as hair colour or eye colour.
Genetic research is rapidly progressing into the genetic basis of complex traits like intelligence and a gene has been identified for criminal behaviour in one family. Once the decision to have IVF is made, PGD has few 'costs' to couples, and people would be more inclined to use it to select less serious medical traits, such as a lower risk of developing Alzheimer Disease, or even for non-medical traits. PGD has already been used to select embryos of a desired gender in the absence of any history of sex-linked genetic disease.
I will argue that: (1) some non-disease genes affect the likelihood of us leading the best life; (2) we have a reason to use information which is available about such genes in our reproductive decision-making; (3) couples should select embryos or fetuses which are most likely to have the best life, based on available genetic information, including information about non-disease genes. I will also argue that we should allow selection for non-disease genes even if this maintains or increases social inequality. I will focus on genes for intelligence and sex selection.
I will defend a principle which I call Procreative Beneficence: couples (or single reproducers) should select the child, of the possible children they could have, who is expected to have the best life, or at least as good a life as the others, based on the relevant, available information.     

Prenatal and preimplantation genetic diagnosis: decision tree, new practices?

Preimplantation genetic diagnosis (PGD) purpose is to assess the genetic status of 3 day-old embryos. PGD offers thus to couples "at-risk" of a genetic disorder an earlier option to prenatal diagnosis (PND). At the beginning, PGD's indications, patients and law were very closed to PND, but PGD specificities are gradually raising. Particularly, indications vary considerably in countries where the absence of law authorizes all the practices. Some of these applications are moreover raising serious ethical issues. Even in France, where this activity is particularly supervised, the recent modification to the law marks this evolution.     

Preimplantation genetic diagnosis of β-thalassemia using real-time polymerase chain reaction with fluorescence resonance energy transfer hybridization probes

Preimplantation genetic diagnosis (PGD) is employed increasingly to allow transfer of embryos to the uterus in assisted reproduction procedures. There are three stages of biopsy: polar bodies, one or two blastomeres from the cleavage-stage embryos, and trophectoderm cells (∼5 cells) from the blastocyst-stage embryos. Validation of polymerase chain reaction (PCR)-based assays are challenging because only limited genetic material can be obtained for PGD. In the current study, we modified a valid single-cell PCR protocol for PGD using real-time PCR assay with fluorescence resonance energy transfer (FRET) hybridization probes followed by melting curve analysis. We optimized and clinically applied the protocol, permitting molecular genetic analysis to amplify a specific region on the beta-globin (HBB) gene for a couple, carriers of two mutations: c.-78A>G and c.52A>T. Among a total of eight embryos obtained after ovarian stimulation, a single blastomere per embryo at the six- to eight-cell stage was biopsied. This PGD method showed that four embryos were unaffected, two embryos were selected for transfer, and one pregnancy was achieved. Finally, a healthy male baby was delivered at 38 weeks’ gestation. The results obtained using the new method, FRET hybridization probes, were compared with findings using an existing method, primer extension minisequencing.     

Preimplantation genetic diagnosis--an overview.

Since the early 1990s, preimplantation genetic diagnosis (PGD) has been expanding in scope and applications. Selection of female embryos to avoid X-linked disease was carried out first by polymerase chain reaction, then by fluorescence in situ hybridization (FISH), and an ever-increasing number of tests for monogenic diseases have been developed. Couples with chromosome rearrangements such as Robertsonian and reciprocal translocations form a large referral group for most PGD centers and present a special challenge, due to the large number of genetically unbalanced embryos generated by meiotic segregation. Early protocols used blastomeres biopsied from cleavage-stage embryos; testing of first and second polar bodies is now a routine alternative, and blastocyst biopsy can also be used. More recently, the technology has been harnessed to provide PGD-AS, or aneuploidy screening. FISH probes specific for chromosomes commonly found to be aneuploid in early pregnancy loss are used to test blastomeres for aneuploidy, with the aim of replacing euploid embryos and increasing pregnancy rates in groups of women who have poor IVF success rates. More recent application of PGD to areas such as HLA typing and social sex selection have stoked public controversy and concern, while provoking interesting ethical debates and keeping PGD firmly in the public eye.     

Le diagnostic génétique pré-implantatoire: premier bilan du groupe parisien

This paper reports the birth of the first fourteen infants conceived after preimplantation genetic diagnosis (PGD) in our unit. Fifty-nine couples were enrolled between January 2000 and July 2001. They had a total of 71 oocyte pick-up cycles. The collected oocytes were inseminated by intracytoplasmic sperm injection. The resulting embryos were biopsied on the third day of development and genetic analysis was performed on the same day. Most of the embryo transfers were carried out on the fourth day. The 71 oocyte pick-up cycles yielded 872 oocytes of which 731 were suitable for intacytoplasmic sperm injection. Among the 505 embryos obtained, 421 embryos were biopsied and genetic diagnosis was performed for 312 (74%) of them. 127 embryos were transferred during 58 transfer procedures. There were 18 biochemical and 12 ongoing (7 singles, 4 twins and 1 triple) pregnancies. Sixteen infants have been born and 2 are expected. PGD now constitutes an alternative for couples at risk of transmission of a serious and incurable genetic disease.     

Clinical applications of MARSALA for preimplantation genetic diagnosis of spinal muscular atrophy

Conventional PCR methods combined with linkage analysis based on short tandem repeats(STRs) or Karyomapping with single nucleotide polymorphism(SNP) arrays, have been applied to preimplantation genetic diagnosis(PGD) for spinal muscular atrophy(SMA), an autosome recessive disorder. However, it has limitations in SMA diagnosis by Karyomapping, and these methods are unable to distinguish wildtype embryos with carriers effectively. Mutated allele revealed by sequencing with aneuploidy and linkage analyses(MARSALA) is a new method allowing embryo selection by a one-step next-generation sequencing(NGS) procedure, which has been applied in PGD for both autosome dominant and X-linked diseases in our group previously. In this study, we carried out PGD based on MARSALA for two carrier families with SMA affected children. As a result, one of the couples has given birth to a healthy baby free of mutations in SMA-causing gene. It is the first time that MARSALA was applied to PGD for SMA, and we can distinguish the embryos with heterozygous deletion(carriers) from the wild-type(normal) ones accurately through this NGS-based method. In addition, direct mutation detection allows us to identify the affected embryos(homozygous deletion), which can be regarded as probands for linkage analysis, in case that the affected family member is absent. In the future, the NGS-based MARSALA method is expected to be used in PGD for all monogenetic disorders with known pathogenic gene mutation.     

Correlation between preimplantation genetic diagnosis for chromosomal aneuploidies and the efficiency of establishing human ES cell lines

There are several sources from which human embryonic stem cell (hESC) lines can be generated: surplus embryos after in vitro fertilization procedures, one- and three-pronuclear zygotes, early arrested or highly fragmented embryos that have reached the blastocyst stage, or otherwise chromosomally or genetically abnormal embryos after preimplantation genetic diagnosis (PGD). We report on the efficiency of establishing hESC lines from blastocysts with proven meiotic or mitotic errors after sequential testing of both polar bodies and blastomere analysis on day 3. The success rate of establishing hESC lines originating from blastocysts carrying a meiotic error was as low as 2.4% and differed significantly from the success rate of establishing hESC lines originating from blastocysts with balanced meiotic errors (21.6%) or mitotic errors (after sequential testing (9.1%) and after blastomere testing alone (12.2%)). This suggests that it may be reasonable to apply sequential PGD prior to the initiation of hESC culture. Information about the karyotype may in the future help refine the methods and possibly improve the efficiency by which hESC lines are derived from embryos with prezygotic abnormalities. Additionally, it may in general prove very difficult to obtain abnormal hESC lines for scientific study from aneuploid PGD embryos, which will limit our ability to study the biological consequences of chromosomal abnormalities. Furthermore, the success rates for generating aneuploid cell lines originating from fertilized oocytes carrying a prezygotic nondisjunction error seem to mirror the miscarriage rates during pregnancy of embryos carrying such errors.