THE CELLULAR RETINOIC ACID-BINDING PROTEIN-I IS DISPENSABLE

The cellular retinoic acid binding proteins I and II (CRABPI and CRABP II) bind retinoic acid with high affinity, exhibit distinct patterns o f expression during embryonic development, and are thought to play imp ortant roles in the RA signaling pathway. We have generated a targeted mutation of the CRABPI gene using the ''hit-and-run'' strategy and sh own that it prevents the production of a functional CRABPI protein. Ho mozygous mutant mice were normal, indicating that CRABPI does not play a crucial role in the RA signaling pathway.