APPLICATION NOTE No. 285 The Eppendorf TransferMan® 4r, one manipulator for all genetic engineering techniques Ronald Naumann, Transgenic Core Facility, Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany Abstract The study of genetically modified animals provides impor- mouse or rat models prefer to have two separate work- tant insights into gene function. It can also be used for stations for the two main techniques, nucleic acid injec- modelling human diseases, to either understand disease tion into fertilized oocytes and embryonic stem (ES) cell mechanisms or aid drug development. transfer into early embryos. The main techniques to generate those animal models With the multifunctional TransferMan 4r, one workstation require micromanipulation devices, but usually in slightly is adequate for all applications because of its easy angle varying set-ups and with different settings for the respec- adjustment, vibration-free movements and unique Eppen- tive techniques. Therefore many laboratories generating dorf DualSpeed™ joystick. Introduction Micromanipulation of oocytes or embryos is the method for modifying the genome of laboratory animals. The most com- mon method is microinjection of nucleic acid constructs like simple transgenes, larger bacterial artificial chromosomes (BAC), or site-specific nucleases like zinc finger (ZFN) and transcription activator-like effector nucleases (TALEN). In recent times, the microinjection of clustered regularly inter- spaced short palindromic repeats (CRISPR) and RNA-guided Cas9 nucleases emerged as a powerful tool for genome engineering. The different types of constructs are either injected into one of the pronuclei of early zygotes (1-2) or into the cytoplasm (3-4). These techniques are called pronuclear and cytoplas- mic injection, respectively. Another technique, though not applicable to all laboratory animals due to the lack of suit- able material and/or limited accessibility of material, is the so-called ES cell transfer, i.e. the injection of genetically modified embryonic stem cells into embryos in blastocyst Figure 1: Eppendorf TransferMan 4r micromanipulators. or 8-cell stage. In addition, the Intracytoplasmic Sperm Injection (ICSI) of either genetically modified sperms or sperms coated with nucleic acid (sperm-mediated gene transfer) into oocytes can be used to generate genetically altered offspring (5). APPLICATION NOTE I No. 285 I Page 2 In practice, all these injection techniques demand certain > Adapter for inverted microscope, Eppendorf (Germany) precautions and considerations for optimal results. They > CellTram 4r Air microinjector for holding the oocyte, do not only differ in the optimal injection angles, but (in Eppendorf (Germany) our opinion) also vary in their demand of the micromanipu- > CellTram 4r Oil microinjector for transferring the ES cells, lators used as well as in the speed of injection movements. Eppendorf (Germany) Therefore most laboratories are using independently > FemtoJet® microinjector for pronuclear and cytoplasmic pre-fixed and finely adjusted workstations for each kind injections, Eppendorf (Germany) of injection technology. > Holding capillaries, e.g. VacuTip I, Eppendorf (Germany) > Injection capillaries, e.g. BioMedical Instruments With the TransferMan 4r (see Figure 1) Eppendorf (Germany) introduces a multifunctional manipulator suitable for > ES cell transfer capillaries, e.g. TransferTip® ES, Piezo all these applications. Drill Tip ES, Eppendorf (Germany) > Eppendorf Microloader™ for back-filling the injection This system includes a number of special features includ- capillaries, Eppendorf (Germany) ing application-specific masks like »Cell transfer«, »DNA injection« or »ICSI« which facilitate and simplify the indi- vidual workflow process. The unique DualSpeed joystick allows precise and intuitive movement during injection in A all spatial dimensions as well as dynamic movements while e.g. collecting ES cells. Thanks to its mounting concept the workstation is sturdy and safe against external vibrations. Furthermore, all elements of the manipulator are easy and fast to install and adjust. The construction of the motor modules allows for an extremely flexible set-up and can be adapted to all major microscopes used. Position changes on the motor modules are extremely flexible and therefore comfortable for all microscopes. The angle adjustment is easily done. It is possible to set shallow angles of theoreti- cally 0°, preferred for pronuclear and cytoplasmic injections B when using straight capillaries, as well as angles up to 45° (with a maximum of 90°). We tested the TransferMan 4r performance for manipulation techniques which are routinely performed in our lab over an extended period of time. Where possible, this was done in parallel to our standard set-up. Materials and Methods Figure 2: Display of the TransferMan 4r control panel: A) Initial display: »Choose Your Application«; Devices B) »Cell transfer« application mask selected with function keys for position > Inverted microscope equipped with Differential Interference storage and Z-axis limit. The 4th softkey is user-definable e.g. for »Axial«, »Clean« or other functions. Contrast (DIC), and 10 x, 20 x and 40 x objectives > Infrared Laser for laser-assisted ES cell transfer, e.g. from OCTAX® (Germany) or Hamilton Thorne (USA) > Two TransferMan 4r micromanipulators (one for moving the holding capillary and the second for positioning the transfer/injection capillary), Eppendorf (Germany) APPLICATION NOTE I No. 285 I Page 3 Operation of the micromanipulator TransferMan 4r Furthermore, the DualSpeed joystick can be operated with Operating the TransferMan 4r micromanipulator with two different movement modes. The standard mode is a its functional softkeys and its single joystick for all move- direct, intuitive movement, a direct transfer of the hand ment dimensions and speed settings is extremely simple movement to the microcapillary. When the maximum (see Figure 2): The selection of the application mask »Cell deflection of the actual path radius has been reached it is transfer« allows for the saving and recall of three capillary possible to press the joystick gently against its outer margin positions, plus the setting of a vertical limit and thus the to activate the dynamic mode so that the needle proceeds avoidance of capillary breakage. The application mask straight in the desired direction with an accelerating speed »DNA injection« offers not only capillary position storage as long as the joystick is deflected (see Figure 3). Using this but also functions to temporarily deactivate the Y motor DualSpeed joystick system, the needle can be moved care- preventing accidental sideways tearing of the zygote during fully in the fine or extra fine (x-fine) speed mode for gentle the sensitive injection procedure. This feature can be of manipulation of cells and embryos whilst still being capable crucial importance especially when the user is not very of a considerable range of quick motion once the dynamic, experienced with this injection technique. The single joystick outer zone of the joystick range is entered. By using this provides easy, intuitive movement control of the micro- feature even cells which are located in the periphery of your capillary in any direction (X, Y, Z), and each TransferMan 4r working focus can be quickly reached and collected. The can store up to five independent positions (depending on the combination of both features, the user-definable application chosen application mask). By simply pressing the joystick mask and the DualSpeed joystick, speeds up the entire work key twice, the capillary can be moved to one of the next flow and therefore shortens the time of samples being held preprogrammed positions. under the light beam of the microscope. Preparation of cells, embryos and injection samples The preparatory steps are of crucial importance but their detailed description would go beyond the scope of this Application Note. They will therefore not be described here, please proceed as described elsewhere (1, 6). Many different organisms may be used for pronuclear and cytoplasmic injection, and there are also more and more laboratory models for the transfer of ES cells. Although the general procedure of both microinjection techniques is very similiar for the different species, this Application Note focuses on the generation of mouse models. Figure 3: Principle of the DualSpeed joystick with direct (1) and dynamic deflection (2). APPLICATION NOTE I No. 285 I Page 4 Preparation of the workstation for pronuclear There are different injection chambers available to serve as (and cytoplasmic) injection a microenvironment for the zygote during the injection pro- One TransferMan 4r micromanipulator is used for moving cess (e.g. plastic Petri dish with glass bottom, depression the holding capillary and the other is used for moving the slide injection chamber or metal frame/glass slide injection injection capillary (Figure 4A). chamber). In our lab, we use a homemade injection chamber A CellTram 4r Air microinjector in combination with a hold- according to our specification. One drop of M2 medium is ing capillary, e.g. the VacuTip I, is used to hold the embryo. placed in the chamber. The zygotes to be injected (10 to 20) The programmable microinjector FemtoJet is used together are placed in one area of this drop. The whole droplet is with finely tapered microinjection capillaries to inject the covered with oil. nucleic acids. The FemtoJet offers an automatic