CRISPR used to peer into human embryos' first days

Francis Crick Institute

The research was undertaken at the Francis Crick Institute Credit Daniel Leal-Olivas

"After the egg is fertilised, it divides until at about seven days it forms a ball of around 200 cells called the "blastocyst", authors of the study explained in a press release on Wednesday.

The Francis Crick Institute team was only given the go-ahead to conduct the research by the Human Fertilisation and Embryology Authority fertility regulator a year ago.

The technique, called CRISPR/Cas9, was used to remove a gene (in 41 embryos) that codes for a protein called OCT4, which is usually activated during the first few days of embryonic development.

Dr Kathy Niakan, who led the work and invented the editing technique, said: "Our research is the first time that genome-editing has been used to understand the role of a gene in early embryonic development".

Scientists at London's Francis Crick Institute discovered the vital role the Oct4 gene played in a viable pregnancy through editing DNA in human embryo - otherwise known as gene-editing.

So-called "pluripotent" stem cells whose fate can be manipulated in the laboratory could one day help the tens of thousand of genetic illnesses that have so far been beyond the reach of medical science.

Among the OCT4 disrupted levels group, only a reported 19 percent made it to the blastocyst stage.

The research was conducted by the Francis Crick Institute, who applied for permission to begin gene editing back in September 2015.

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"Other research methods, including studies in mice, suggested a later and more focused role for OCT4, so our results highlight the need for human embryo research", she said in a statement.

The researchers had to apply to the Human Fertilisation and Embryology Authority, an institution set up in the United Kingdom that rigorously reviews proposed embryo-editing research, Vogel reports for Science. It is possible that the reason why some of those embryos fail to develop is because Oct4 isn't working properly, and there may be a simple molecular test that could distinguish which embryos are most likely to develop normally.

Niakan says this study could eventually lead to improvements in the development and therapeutic use of stem cells and in IVF treatment.

Lead author Kathy Niakan (Francis Crick Institute, London) says she hopes the technique can be used by others to identify a whole host of genetic factors that affect pregnancy, but are now poorly understood: "One way to find out what a gene does in the developing embryo is to see what happens when it isn't working".

Many experts believe the form of research is pivotal to gaining a better understanding of how humans develop.

Niakin and colleagues used CRISPR to deactivate the gene that codes for OCT4 in 37 single-cell human embryos left over after in vitro fertilization treatments and donated by couples.

"It may take many years to achieve such an understanding, our study is just the first step", said Niakan.

Dr Niakan's team was the first to use the editing technique to investigate gene function in human embryos, rather than try to correct defective genes. The study has been carried out with full regulatory oversight and offers new knowledge of the biological processes at work in the first five or six days of a human embryo's healthy development. Niakan's team found that human embryos stopped growing earlier than mouse embryos lacking the protein and showed different patterns of gene expression.

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