Drosophila Microinjection - All you need to know
Important: Preparing your DNA sample
Sample quality is the major factor that determines the success or failure of microinjection work. Please read our guidelines for sample preparation before sending your samples for microinjection.
Help with experimental design
We are happy to assist with selecting the best host stock (embryos) for your microinjection experiment and with other aspects of experimental design. Please contact us at flyinject@gen.cam.ac.uk.
- List of phiC31 stocks currently available in the Fly Facility.
- List of Cas-9 expressing stocks currently available in the Fly Facility.
If you prefer a host stock that is not currently kept by the Fly Facility, please send us some healthy flies or direct us to where we can obtain some.
We can inject into the progeny of a cross, but we charge an additional fee (currently £20) for virgin collection.
Sending your samples for microinjection
Please download and complete the and send it with your samples for injection to Alla Madich, Department of Genetics, Downing Site, Downing Street, Cambridge, CB2 3EH. UK.
If your sample tube is crushed during transport, your sample may be lost through the lid opening or the tube splitting. Therefore, it is best to mail your sample in a padded envelope (Jiffy bag) or a box. Please use a small (0.5 ml) Eppendorf tube for your sample. It is easier for us to handle the small sample volume in a 0.5 ml tube, compared to a 1.5 ml tube, and so we are less likely to require an additional sample if repeat injections are needed. Do not use PCR tubes as they are fragile and easily crushed. Sealing the tube lid with parafilm or similar will help prevent the lid opening and also guard against evaporation.
Choosing sample names
Our staff need to be able to communicate with you, and with each other, about individual injection samples. Ideally, your sample names should be relatively brief to make this communication easier. However, the names should also be sufficiently unique that they are unlikely to match other sample names currently in our database. So "ABC-123" might be a good choice, whereas "Sample A" is likely not unique, and "pUAST-attB-5'GFP-exonII-frag-3'MycTag-7a" is just too long!
Sending fly stocks for microinjection
If you would like us to inject into your own fly line, please provide us with sufficient flies to set up an injection cage (around 500-1000 flies). We prefer flies to be sent as larvae so that we can set up the cage using newly-emerged adults. Young adults produce eggs in greater quantity, and of better quality, than older flies. Please contact us to discuss the best time to send your flies. Please ensure the flies you provide are free of mites or we may not accept them for injections.
Receiving your injected flies
When the service is complete, we will send the injected flies to you via regular mail. In our experience, this approach works well and it is rare that the flies fail to reach their destination. For service plans that involve screening, crossing and/or stock construction (e.g. Plans 2, 3, 5 and 7) we will resend flies at no additional cost if the original package fails to reach you. However, for 'injection only' requests where we ship all the injected larvae (e.g. Plans 1, 4, 6 and 8) we will not repeat the service if you fail to receive the larvae unless the failure clearly results from our own error.
Injection-only requests from outside the UK: We no longer accept injection-only requests (e.g. Plans 1, 4, 6, 8) from outside the UK. This is because we are uncertain whether shipping from the UK to the EU will be efficient enough to ensure the viability of injected larvae.
Culturing your injected larvae (injection-only plans)
For injection-only requests (e.g. Plans 1, 4, 6 and 8), every surviving G0 larva is precious so it important to provide the best possible culture conditions. After injection, we recover viable larvae in a yeast paste/agar plug which we then transfer to a plastic tube containing fly food. We mail this tube to you. Ideally, you should put the tube in a humidified incubator at between 18oC and 25oC.
Before placing the tube in an incubator, check if there are any signs that the food is drying out, since dehydration is the biggest threat to larval survival. Are there gaps between the food and the side of the tube? Does the food appears lumpy rather than smooth? If the food appears to be drying, you can add water directly to the tube. Do not fill water above the surface of the food as you will risk drowning the larvae. Alternatively, you can gently push a ball of tissue paper into the surface of the drying food and then saturate the paper with water. You can also add a liquid yeast paste to the food surface which will both hydrate the tube and nourish the larvae. It is worth continuing to monitor your tubes of injected larvae for dehydration. This is particularly important if your incubator is not humidified or relies on passive humidification (e.g. trays of water placed in the incubator).
We also recommend that you make regular collections of adults when they start emerging from the tube. In our experience, adult flies show better survival when removed from the original tube to a fresh tube shortly after they eclose.
Paying for your microinjection work
Click here for a description of our prices and plans
- University of Cambridge Department of Genetics members: Please supply a Grant Code for payment on the
- University of Cambridge users outside of the Department of Genetics: Please email a copy of your Purchase Order to Simon Collier (simon.collier@gen.cam.ac.uk) at the time you send your samples. Also, please include the Purchase Order number on your Invoices for microinjection work are normally sent at the completion of the service unless you request otherwise
- Users outside of the University of Cambridge: You have two options:
- Option 1: Purchase Order: Please email a copy of your Purchase Order to Simon Collier (simon.collier@gen.cam.ac.uk) at the time you send your samples. Also, please include the Purchase Order number on your Invoices for microinjection work are normally sent at the completion of the service unless you request otherwise. Please note: Our microinjection service does not qualify for medical VAT-exemption. All Purchase Orders covering microinjection requests from research groups in the UK (outside of Cambridge University) must include VAT at 20%.
- Option 2: Credit card:
- Credit card users in the UK: Please visit our Online Store for UK Business. Enter the total cost of the sevice including VAT (all UK users outside of the University of Cambridge are required to pay VAT at 20% on their microinjection payments). You will be asked to provide the name of the person who submitted the original Microinjection Request Form as well as their department and institution affiliation. Please provide this information, it will allow us to confidently match your payment to a specific microinjection request.
- Credit card users in the rest of the world: Please visit our Online Store for Rest of the World Business. Enter the total cost of the service excluding VAT. You will be asked to provide the name of the person who submitted the original Microinjection Request Form as well as their department and institution affiliation. Please provide this information, it will allow us to confidently match your payment to a specific microinjection request.
VAT charges for Microinjection work
We have been informed by the University of Cambridge Finance Division Tax Office that our Microinjection Service does not qualify for medical VAT-exmption. Consequently all microinjection charges for UK research groups (outside of the University of Cambridge) are subject to VAT at the standard rate (20%). Please ensure that your Purchase Order includes VAT at 20% and do not send a VAT-exemption certificate with your Purchase Order.
What if my microinjection experiment fails?
For Plans 2, 3, 5 and 7 we will inject a further 200 embryos (at no extra cost) if we do not obtain our guaranteed number of transformants. However, Plans 1, 4, 6 and 8 are injection only – we do not routinely re-inject if no transformants are obtained. Go here for a description of Plans 1-8. Please note: Our offer of a free injection only applies to repeats of the original injection with, perhaps, minor modifications (freshly prepared sample, change of host stock etc.). It is not a credit for future injection requests.
Acknowledging the Fly Facility
Please acknowledge 'The University of Cambridge Department of Genetics Fly Facility' in any publications or public presentations resulting from the use of microinjected flies
Our Terms and Conditions
To use our microinjection service, you must agree to our Term and Conditions for Microinjection work.