Intra-cytoplasmic sperm injection (ICSI) is a method of fertilisation that involves the injection of a single sperm into an oocyte. The technique has been applied successfully to generate viable offspring in human, mouse and other vertebrates, but never before has a live bird been produced using ICSI due to difficulties in mimicking avian polyspermic fertilisation. Now, on p. , Tomohiro Sasanami and colleagues report the birth of a live quail chick using ICSI and identify some critical parameters that hitherto prevented the successful application of this technique. The authors inject a single sperm together with sperm extract, of which they identify three different components essential for full egg activation and development: phospholipase Cζ, aconitate hydratase and citrate synthase. Importantly, the authors use this system to analyse Ca2+ dynamics during egg activation and show that, in contrast to mammals, avian egg activation requires two distinct patterns of Ca2+ flux: an initial transient rise and a long-lasting spiral-like oscillation. These findings represent an exciting step forward in the study of vertebrate egg activation and will provide new opportunities for the production of transgenic and cloned birds.
