Dose-Sensitive Autosomal Modifiers Identify Candidate Genes for Tissue Autonomous and Tissue Nonautonomous Regulation by the Drosophila Nuclear Zinc-Finger Protein, Hindsight

The nuclear zinc-finger protein encoded by the hindsight (hnt) locus regulates several cellular processes in Drosophila epithelia, including the Jun N-terminal kinase (JNK) signaling pathway and actin polymerization. Defects in these molecular pathways may underlie the abnormal cellular interactions, loss of epithelial integrity, and apoptosis that occurs in hnt mutants, in turn causing failure of morphogenetic processes such as germ band retraction and dorsal closure in the embryo. To define the genetic pathways regulated by hnt, 124 deficiencies on the second and third chromosomes and 14 duplications on the second chromosome were assayed for dose-sensitive modification of a temperature-sensitive rough eye phenotype caused by the viable allele, hntpeb; 29 interacting regions were identified. Subsequently, 438 P-element-induced lethal mutations mapping to these regions and 12 candidate genes were tested for genetic interaction, leading to identification of 63 dominant modifier loci. A subset of the identified mutants also dominantly modify hnt308-induced embryonic lethality and thus represent general rather than tissue-specific interactors. General interactors include loci encoding transcription factors, actin-binding proteins, signal transduction proteins, and components of the extracellular matrix. Expression of several interactors was assessed in hnt mutant tissue. Five genes--apontic (apt), Delta (Dl), decapentaplegic (dpp), karst (kst), and puckered (puc)--are regulated tissue autonomously and, thus, may be direct transcriptional targets of HNT. Three of these genes--apt, Dl, and dpp--are also regulated nonautonomously in adjacent non-HNT-expressing tissues. The expression of several additional interactors--viking (vkg), Cg25, and laminin-alpha (LanA)-is affected only in a nonautonomous manner.