A FUNCTIONAL-ANALYSIS OF NOTCH MUTATIONS IN DROSOPHILA

The Notch gene encodes a receptor protein that is involved in many pro cesses during development. Its best understood role is during neurogen esis in a process called ''lateral inhibition.'' However, it has been proposed that Notch also has a role in defining the proneural clusters in the first place. This raises the possibility that the Notch protei n is acting as a multifunctional receptor. To test this hypothesis, we have carried out a genetic analysis of molecularly characterized Notc h alleles to identify alleles that affect only one of the two proposed functions. Here we present evidence that Notch alleles can be identif ied that appear to affect the function of Notch during either lateral inhibition or the definition of proneural clusters. In addition our re sults indicate that there may be discrete regions of the Notch protein required for each function.