Behind the scenes at the Gene Editing Strategic Research Centre
Truly collaborative research
Each of the co-investigators of the SRC take it in turns to host these quarterly lab meetings. When I attended, it was the turn of Dr Paola Bonfanti who has recently set up her lab in the prestigious Francis Crick Institute at King’s Cross. The Institute, home to over 1,500 scientists and support staff, was designed to encourage collaboration and the exchange of ideas.
Strategic research centres allow researchers with different knowledge and expertise to work together to solve a common problem. In this SRC, the gene editing expertise of Professor Stephen Hart and Dr Patrick Harrison (University College Cork) is combined with the stem cell expertise of Dr Paola Bonfanti and the physiological and electrophysiological expertise of Prof Chris O’Callaghan (UCL GOS Institute of Child Health) and Prof Deborah Baines (St George’s University).
What’s the difference between gene editing and gene therapy?
Gene editing goes into the cell to fix the faulty CFTR gene permanently. Gene therapy, on the other hand, aims to deliver new copies of the healthy gene, leaving the existing faulty gene in place.
What are the aims of the gene editing SRC?
The SRC programme is looking at two approaches to delivering gene editing. The first approach is to deliver the gene editing machinery and do the repair in the body. The other way is to take stem cells from the noses of people with cystic fibrosis (CF), edit the CF gene in these cells in dishes in the lab, grow lots of corrected cells, and then deliver them back to the same person.
The researchers working on the SRC have recently completed the first year of the programme. Much of their work has been about optimising their experimental processes, from getting the cells growing nicely in the lab, to working out how to deliver the treatment and finally to working out how to measure the effects on the function of the CFTR protein/receptor.
Practicing your technique first
The researchers working on the SRC are practicing their gene editing techniques on cell cultures growing in the lab before they try them out in animal models or people. It’s important to make sure that the cells are growing well and you really understand what’s happening in normal conditions before you can begin your experiments in cells with a faulty CF gene. If you don’t do this prep work, then it will be hard to be sure whether any changes (good or bad) are due to the experiment you’re running or the cells’ normal activity.
At the SRC meeting I heard about ‘ALI’ cultures, a realistic way of growing lung cells. The ‘ALI’ acronym stands for ‘Air – Liquid – Interface’. When cells are grown in the lab they are generally grown in a flat plastic dish and the liquid, or ‘medium’, which contains the energy and nutrients to keep the cells alive, is added on top of them. In ALI cultures, the medium is added to one dish, then the cells are added into an insert inside it, with holes in the bottom (a bit like a chip basket sitting in a pan of oil, but with no holes in the sides, just in the bottom). As the bottom half of the cells are in liquid and the top half of the cells are in the air, they can act and grow like cells in the lining of our lungs.
Getting all the gear in place
The CRISPR molecular ‘kit’ for gene editing has a number of bits to it. You need the cutting tools or scissors (Cas9 enzyme), the guide RNA (or gRNA) to direct the scissors to the mutation where the DNA will be cut, and most of the time the DNA template to make the repair / edit the gene.
Find out more about the latest results of gene editing.
When trying out gene editing in the lab, you’re also likely to add in a reporting or tracking system, so you can actually see what’s happening to the kit and if it’s doing its job. This tracking system is likely to take the form of a fluorescent protein. (Fluorescent proteins come in almost as many shades as a Dulux colour chart – but at their most basic they’re usually red, yellow, green or blue).
The gear is transported into the cell either as the instructions – so called ‘constructs’ – of DNA or RNA, or as the preformed Cas9 enzyme/gRNA particle.
In the SRC, there are a few aspects to the mechanics of gene editing: they want to see if the gear gets delivered, that it can assemble itself from the instructions in the ‘construct’ (if appropriate), and of course that the gene editing takes place in a safe and beneficial way.
The aim of gene editing is to get a healthy copy of the CFTR protein working on the cell surface. To test how well the protein is functioning, researchers measure the flow of electricity across the boundary of the cell. (The CFTR allows negatively charged chloride ions to travel out of the cell, which forms a current across the membrane.) The current is measured using a nifty piece of lab equipment called ‘Ussing chambers’. The study of these tiny electrical charges across cells is known as ‘electrophysiology’.
All of the researchers together on this SRC are fulfilling the aims of the Crick Institute and of the Trust’s SRC programme in terms of working so well collaboratively. I came away dazzled by the new techniques they’re working on and my head full of exciting research. I’d like to thank the lab members for making me so welcome.
You can read more about the gene editing SRC on our website.
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*Main photo: members of the Hart SRC team at the Crick Institue visit.