Ten-year experience with preimplantation genetic diagnosis (PGD) at the New York University School of Medicine Fertility Center

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.

Preimplantation genetic diagnosis for inherited neurological disorders

Preimplantation genetic diagnosis (PGD) is an option for couples at risk of having offspring with an inherited debilitating or fatal neurological disorder who wish to conceive a healthy child. PGD has been carried out for conditions with various modes of inheritance, including spinal muscular atrophy, Huntington disease, fragile X syndrome, and chromosomal or mitochondrial disorders, and for susceptibility genes for cancers with nervous system involvement. Most couples at risk of transmitting a genetic mutation would opt for PGD over prenatal testing and possible termination of a pregnancy. The aim of this Perspectives article is to assist neurologists in counselling and treating patients who wish to explore the option of PGD to enable conception of an unaffected child. PGD can be accomplished for most disorders in which the genetic basis is known, and we argue that it is time for clinicians and neurological societies to consider the evidence and to formulate guidelines for the responsible integration of PGD into modern preventative neurology.

Idiopathic recurrent miscarriage is caused mostly by aneuploid embryos

OBJECTIVE

To determine any beneficial effects of preimplantation genetic screening (PGS) of all chromosomes by array comparative genomic hybridization (aCGH), with either day 3 or blastocyst biopsy, for idiopathic recurrent pregnancy loss (RPL) patients compared with their expected loss rate.

DESIGN

Case series report.

SETTING

Multiple fertility centers.

PATIENT(S)

A total of 287 cycles of couples with idiopathic RPL (defined as two or more losses).

INTERVENTION(S)

PGS was done with day 3 biopsy (n = 193) or blastocyst biopsy (n = 94), followed by analysis with aCGH.

MAIN OUTCOME MEASURE(S)

Spontaneous abortion rate, euploidy rate.

RESULT(S)

A total of 2,282 embryos were analyzed, of which 35% were euploid and 60% were aneuploid. There were 181 embryo transfer cycles, of which 100 (55%) became pregnant with an implantation rate of 45% (136 sacs/299 replaced embryos) and 94 pregnancies (92%) were ongoing (past second trimester) or delivered. The miscarriage rate was found to be only 6.9% (7/102), compared with the expected rate of 33.5% in an RPL control population and 23.7% in an infertile control population.

CONCLUSION(S)

Current PGS results with aCGH indicate a significant decrease in the miscarriage rate of idiopathic RPL patients and high pregnancy rates. Furthermore, this suggests that idiopathic recurrent miscarriage is mostly caused by chromosomal abnormalities in embryos.

Preimplantation genetic diagnosis on in vitro fertilization clinic websites: presentations of risks, benefits and other information

OBJECTIVE

To examine information on preimplantation genetic diagnosis (PGD) presented on IVF clinic websites.

DESIGN

We systematically sampled every third IVF clinic on the 2004 Centers for Disease Control provider list.

SETTING

The Internet.

PATIENT(S)

None.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Benefits, risks, and other types of information mentioned regarding PGD.

RESULT(S)

Of 135 sites examined, 88.1% had websites, and 70% mentioned PGD, of which 27% were university- or hospital-based and 63% were private clinics. Sites mentioning PGD listed uses and benefits of PGD far more than the risks involved. Of these sites, 76% described testing for single-gene diseases, but fewer mentioned risks of missing target diagnoses (35%) or risks for loss of embryo (18%), and 14% described PGD as new or controversial. Private clinics were more likely than other programs to be on either the East or West Coast, list certain PGD risks (e.g., diagnostic error), note that PGD was new or controversial, reference source of PGD information, provide accuracy rates of genetic testing of embryos, and offer gender selection for social reasons.

CONCLUSION(S)

Most IVF clinics advertise PGD online, but the scope and quality of information about it varies widely, emphasizing benefits while minimizing risks. Clinics and patients may benefit from more thorough and consistent presentation of PGD, drawing on available evidence to best provide a realistic portrayal of PGD.

Preimplantation genetic diagnosis for beta-thalassemia using single-cell DNA analysis for codons 17 and 26 of beta-globin gene

BACKGROUND

Preimplantation genetic diagnosis (PGD) of monogenic autosomal hereditary disorders following assisted conception usually involves the removal of one or two blastomeres from preimplantation embryos. However, the amount of DNA from a single blastomere is insufficient to amplify the region of interest. Hence, the whole genome amplification (WGA) method is performed prior to amplifying the genes of interest before analysis of DNA material through polymerase chain reaction (PCR).

METHODS

In the present study we report that WGA from a single blastomere extracted from unwanted preimplantation human embryos (obtained from 10 infertile couples) could positively yield microgram quantities of amplified DNA allowing PCR analysis for codons 17 and 26 of the beta-globin gene that cause the beta-thalassemia disorder. We developed a rapid and highly specific technique of single-cell PCR to amplify a specific region on the beta-globin gene for codon 17 (AAG-->TAG) and codon 26 (GAG-->AAG) by using single-cell PCR.

RESULTS

About 249 bp of amplicon for codon 17 and about 200 bp of amplicon for codon 26 were successfully amplified. No mutations were observed. Analyzed embryos were not transferred back to patients because the embryos used as samples were wasted embryos.

CONCLUSIONS

Compared to other approaches for prenatal diagnosis, PGD is rapid and suitable as a noninvasive clinical tool for identifying genetic disorders for the purpose of reducing selective miscarriages and moral dilemmas. We opine that DNA extraction and amplification can be successfully performed by using single-cell PCR to diagnose genetic diseases before pregnancy.