The Abruptex mutations of Notch disrupt the establishment of proneural clusters in Drosophila

The receptor encoded by the Notch gene plays a central role in preventing c ells from making decisions about their fates until appropriate signals are present. This function of Notch requires the product of the Suppressor of H airless gene. Loss of either Notch or Suppressor of Hairless function resul ts in cells making premature and incorrect cell fate decisions, whilst incr eases in Notch signalling prevent cells from making these decisions. Here w e find that the proneural clusters are? not established correctly in certai n Abruptex mutations of Notch and this failure to establish proneural clust ers correctly is not due to increased Notch signalling during lateral inhib ition. In addition we show that the overexpression of certain dominant nega tive Notch molecules can disrupt the initiation of proneural cluster develo pment in a manner similar to the Abruptex mutants. (C) 1999 Academic Press.