... retroviral A env protein on their surface. Embryos were injected at stage 18 into the eye (A and B), stage 10 into the neural tube (E and F), or stage 18 into the limb bud or heart regions (C, ... different tag location or choice of an alternative tag can be considered. Attaching Tags to Proteins Engineering an expression clone with the selected epitope tag fused to the open reading frame of ... a dedicated histology laboratory would be well advised. Much of the equipment and many of the procedures for fixing, dehydrating, clearing, embedding, and sectioning tissues are rou- tine...