1. Egg production Place about 30 adult snails (10 mm diameter) into a 5.5-liter water tank. Place a piece of polystyrene of (3 x 3 cm) in each tank. There is the preferred support of Biomphalaria glabrata for laying its eggs. The snails are fed ad libitum with green lettuce leaves, they can also be fed with dry spirulina to boost reproduction. Maintain water at a temperature of 25 degrees Celsius. 2. Egg collection Gently pick up several egg layers from the polystyrene with soft holding forceps and place the eggs into a petri dish with natural mineral water (e.g. Volvic) to prevent them from drying out. Start sorting the eggs under the stereoscopic microscope to choose only the gastrula stage and place them into another petri dish with natural mineral water. 3. Preparation of the transfection solution Material: a. in vivo JetPEI transfection reagent b. 10% glucose solution c. 5% glucose solution d. Plasmids (dCas9-SunTag-BFP and scFv-DNMT3A-GFP) e. 0.2 ml microtubes f. P10 and P200 pipettes g. P10 and P200 pipette tips h. Permanent marker The glucose solution and the in vivo jetPEI transfection reagent are equilibrated at room temperature. Prepare 21 µl of each plasmid at a concentration of 78 and 88 ng / µl respectively (for a total volume of 42 µl =equals 3.5 µg of DNA) add the plasmid DNA to a 0.2 ml tube (labeled as Tube A) and mix with 21 µl of 10% glucose solution. In another microtube (labeled as Tube B), add 21 μl of 5% glucose solution and 1 μl of in vivo jetPEI. Prepare a third tube (labeled as Tube C) with 21 µl of 5% glucose solution and 0.5 µl of in vivo jetPEI to inject into embryos that will serve as controls. Leave the solutions at room temperature while you prepare the microinjection station. 4. Preparation of the micro-injection station Material: a. Pre-pulled glass micropipettes (1mm diameter) b. Watch glass c. Modeling clay d. 35 mm and 90 mm petri dishes e. Mineral oil (M5904, SIGMA) f. Wash bottle with natural mineral water (Volvic) g. 0.2 ml microtubes h. 12-well cell culture plate i. Fine brush j. Phenol red solution k. Pasteur pipette or dropper l. Dissection forceps m. Soft holding forceps n. Snail eggs in the gastrula stage o. Drummond Scientific Nanoject III Programmable Nanoliter Injector Take a pre-pulled glass micropipette and cut it with a scalpel to have a ~ 0.2 mm ti...