Our April issue is now online, and one of our featured protocols this month is a classic that, in the age of GFP and live imaging, has held up remarkably well and is still used with surprising frequency.

Staining Whole Mouse Embryos for ß-Galactosidase (lacZ) Activity, by Andras Nagy, Marina Gertsenstein, Kristina Vintersten, and Richard Behringer (authors of CSHL Press’ well-known “Manipulating The Mouse Embryo” manual) is a technique that one would think would no longer turn up so often in publications and talks. After all, why bother with a technique requiring you to fix the embryo and look at one static timepoint, when you could image fluorescent proteins over time? Clearly, X-gal staining is still highly valued, probably because of the ease of the staining method and the high level of specificity it provides. Staining an embryo (or most tissues) with X-gal is a fairly trivial procedure. The resultant blue precipitate is easily visualized, and can be used to detect lower levels of expression than can commonly be seen through in situ hybridization techniques or with fluorescent proteins, as both methods have higher levels of background which can interfere with detecting signal.

Related protocols on Imaging X-gal stained embryos and staining frozen sections with X-gal are also new to CSH Protocols this month.

As an aside, the first paper I published featured this very same method, so it has a certain sentimental value. Also, for those who don’t like the color blue, don’t forget you can always substitute in Salmon-gal or Magenta-gal to get the color scheme you prefer.