The earliest publication credited with predicting the possible development of preimplantation genetic testing for human inherited disease is the Nature article from 1968 by Richard Gardner and the IVF pioneer and Nobel laureate, Robert Edwards. Tiny scissors, normally used for eye surgery, were used to cut away a small fragment of the trophectoderm from rabbit embryos. The cells were then fixed on microscope slides and stained for heterochromatin so that the Barr bodies representing the inactive X chromosome in female embryos were visible under the microscope. Male and female embryos were then separately transferred to rabbit recipients and the sex confirmed in fetuses recovered late in pregnancy. The authors finish their discussion by commenting ‘… cells excised from blastocysts could be examined for several characteristics, for example, chromosomes and enzymes, to detect autosomally inherited deformities from either parent‘. It would then be over 20 years before their predictions could be realised with the development of in vitro fertilisation (IVF) and the polymerase chain reaction (PCR)!
There are now thousands of publications in preimplantation genetics. The aim here is not to provide a complete listing of all of them but to curate a list of the most important publications grouped by topic that illustrate important milestones in the science and clinical application of the genetics of early human development. Suggestions for topics are welcome and if we have inadvertently left out important papers please let us know by email.
Tripolar mitosis and partitioning of the genome arrests human preimplantation development in vitro
Ottolini, Kitchen, Xanthopoulou, Gordon, Summers & Handyside
Scientific Reports 7: 9744 DOI:10.1038/s41598-017-09693-1
Open Access Click here
Following in vitro fertilisation (IVF), only about half of normally fertilised human embryos develop
beyond cleavage and morula stages to form a blastocyst in vitro. Although many human embryos are
aneuploid and genomically imbalanced, often as a result of meiotic errors inherited in the oocyte, these
aneuploidies persist at the blastocyst stage and the reasons for the high incidence of developmental
arrest remain unknown. Here we use genome-wide SNP genotyping and meiomapping of both polar
bodies to identify maternal meiotic errors and karyomapping to fingerprint the parental chromosomes
in single cells from disaggregated arrested embryos and excluded cells from blastocysts. Combined with
time lapse imaging of development in culture, we demonstrate that tripolar mitoses in early cleavage
cause chromosome dispersal to clones of cells with identical or closely related sub-diploid chromosome
profiles resulting in intercellular partitioning of the genome. We hypothesise that following zygotic
genome activation (ZGA), the combination of genomic imbalance and partial genome loss disrupts
the normal pattern of embryonic gene expression blocking development at the morula-blastocyst
transition. Failure to coordinate the cell cycle in early cleavage and regulate centrosome duplication is
therefore a major cause of human preimplantation developmental arrest in vitro.
High implantation and clinical pregnancy rates with single vitrified-warmed blastocyst transfer and optional aneuploidy testing for all patients
Gorodeckaja, Neumann, McCollin, Ottolini, Wang, Ahuja, Handyside & Summers
Human Fertility doi: 10.1080/14647273.2018.1551628
This study reports the results of a 2-year long IVF programme (‘One by One’) in which all
patients (median age 40 years; range 27–45 years) were offered preimplantation genetic testing
for aneuploidy (PGT-A) and had all blastocysts vitrified (freeze-only), followed later by single vitrified-
warmed blastocyst transfer (vSET) in managed cycles. Between January 2016 and
December 2017, a total of 155 patients started 222 treatment cycles and 99 (45%) cycles
resulted in one or more vitrified blastocysts (untested or with normal copy number for all chromosomes)
available for transfer. Seventeen patients (11%) aged 35 years opted out of PGT-A.
Over this period, 85 vSETs in 74 patients resulted in an implantation rate of 80% (68/85) and a
singleton clinical pregnancy rate of 66% (56/85). Cumulative live birth rates will not be known
for 1–2 years. Nevertheless, these high success rates with vSET confirm larger studies using
selected patients and are likely to deliver similar, if not higher, live birth rates per cycle started
than rates typically reported in national registries with conventional IVF and transfer of one or
more fresh and/or frozen embryos.
The dawn of the future: 30 years from the first biopsy of a human embryo. The detailed history of an ongoing revolution
Cimadomo, Rienzi, Capalbo, Rubio, Innocenti, García-Pascual, Ubaldi and Handyside
Human Reproduction Update 26, 453–473
Editors choice Free access Click here
Following early studies showing no adverse effects, cleavage stage biopsy by zona drilling using acid Tyrode’s solution, and removal of single blastomeres for preimplantation genetic testing (PGT) and identification of sex in couples at risk of X-linked disease, was performed by Handyside and colleagues in late 1989, and pregnancies reported in 1990. This method was later used for specific diagnosis of monogenic conditions, and a few years later also for chromosomal structural and/or numerical impairments, thereby establishing a valuable alternative option to prenatal diagnosis. This revolutionary approach in clinical embryology spread worldwide, and several other embryo biopsy strategies developed over three decades in a process that is still ongoing. The rationale of this narrative review is to outline the different biopsy approaches implemented across the years in the workflow of the IVF clinics that provided PGT: their establishment, the first clinical experiences, their downsides, evolution, improvement and standardization. The history ends with a glimpse of the future: minimally/non-invasive PGT and experimental embryo micromanipulation protocols. This grand theme review outlines a timeline of the evolution of embryo biopsy protocols, whose implementation is increasing worldwide together with the increasing application of PGT techniques in IVF. It represents a vade mecum especially for the past, present and upcoming operators and experts in this field to (re)live this history from its dawn to its most likely future.
Copy number analysis of meiotic and postzygotic mitotic aneuploidies in trophectoderm cells biopsied at the blastocyst stage and arrested embryos
Handyside, McCollin, Summers and Ottolini
Prenatal Diagnosis DOI: 10.1002/pd.5816
Open Access Click here
Preimplantation genetic testing for aneuploidy (PGT-A) by copy number analysis is no wwidely used to select euploid embryos for transfer. Whole or partial chromosome aneu-ploidy can arise in meiosis, predominantly female meiosis, or in the postzygotic, mitoticdivisions during cleavage and blastocyst formation, resulting in chromosome mosaicism.Meiotic aneuploidies are almost always lethal, however, the clinical significance ofmitotic aneuploidies detected by PGT-A is not fully understood and healthy live births have been reported following transfer of mosaic embryos. Here, we used single nucleotide polymorphism genotyping of both polar bodies and embryo samples to identify meiotic aneuploidies and compared copy number changes for meiotic and presumed mitotic aneuploidies in trophectoderm cells biopsied at the blastocyst stage andarrested embryos. PGT-A detected corresponding full copy number changes (≥70%) for36/37 (97%) maternal meiotic aneuploidies. The number of presumed mitotic copynumber changes detected exceeded those of meiotic origin. Although mainly in the mosaic range, some of these mitotic aneuploidies had copy number changes ≥70% and would have been identified as full aneuploidies. Interestingly, many arrested embryos had multiple mitotic aneuploidies across a broad range of copy number changes, which may have arisen through tripolar spindle and other mitotic abnormalities.
16th November 2020
Reproduction Special Issue '30 years of Preimplantation Genetic Testing'
Guest editor Professor Alan H Handyside
Guest editorial and video Click here
Recent lectures and videos
December 2nd, 2020 Informal interview with Prof Alan Handyside Click here
In this interview with Prof Darren Griffin, School of Biosciences, University of Kent, Prof Alan Handyside recalls some of the work which led to the first clinical application and pregnancies following IVF and preimplantation genetic diagnosis, or PGD, for couples at risk of X-linked disease in 1990 and how preimplantation genetic testing has developed over 30 years since then and briefly outlines some exciting possible future developments.
December 3rd, 2020 Advances in Preimplantation Genetic Testing (PGT): A 30-Year Perspective Click here
Keynote lecture presented at the Japanese Society for Human Genetics November, 2020 and sponsored by Vitrolife
December 18th, 2020 BBC documentary on human embryo research and PGD 'The First Fourteen Days' February 1990 Click here
Horizon is the BBC's flagship science progamme, which has been broadcast since the 1960's and continues today. This programme was broadcast in February, 1990 and focussed on the forthcoming debate to be held in the Houses of Parliament in the UK in April of that year on whether to ban or allow human embryo research up to 14 days post fertilisation. There are interviews with Prof Sir Robert Edwards at Bourne Hall, Cambridge, Prof Martin Johnson (my PhD supervisor), Prof Peter Braude, Dame Anne McClaren and Professor Lord Robert Winston, who I worked with at London's Hammersmith Hospital. It includes filming of the egg collection and transfer for the first successful attempt to use IVF and preimplantation genetic diagnosis (PGD) in a couple at risk of adrenoleukodystrophy. I have a cameo appearance performing embryo biopsy and analysing the gel following PCR for a Y linked repeat sequence to identify the gender of the embryos, with Dr Elena Kontogiani, then my PhD student.
Prof Alan Handyside
December 18th, 2020 Cleavage stage human embryo biopsy c 1989 Click here
I made this video to demonstrate cleavage stage human embryo biopsy sometime in 1989 for the BBC. At the time, I used a stereo microscope and Leitz micromanipulator and a mouth pipette with holding and biopsy pipettes which I made by hand using capillary tubing and a small alcohol burner.
For a fascinating insight into the development of embryo biopsy for preimplantation genetic testing up to the present day see Cimadomo et al (2020) Human Reproduction Update (link above)
December 21st, 2020 Various videos from the 1980s and 1990s
Check out and subscribe to my personal YouTube channel for more videos from the ealry days of preimplantation genetics.