STRIPE-SPECIFIC REGULATION OF PAIR-RULE GENES BY HOPSCOTCH, A PUTATIVE JAK FAMILY TYROSINE KINASE IN DROSOPHILA

We describe the characterization of the Drosophila gene, hopscotch (ho p), which is required maternally for the establishment of the normal a rray of embryonic segments. In hop embryos, although expression of the gap genes appears normal, there are defects in the expression pattern s of the pair-rule genes even-skipped, runt, and fushi tarazu, as well as the segment-polarity genes engrailed and wingless. We demonstrate that the effect of hop on the expression of these genes is stripe-spec ific. The hop gene encodes a putative nonreceptor tyrosine kinase of t he Janus kinase family, based on an internal duplication of the cataly tic domain. We present a model in which the Hop tyrosine kinase is inv olved in the control of pair-rule gene transcription in a stripe-speci fic manner. Our results provide the first evidence for stripe-specific regulation of pair-rule genes by a tyrosine kinase.