Copyright zyxwvutsrqp 6 1997 by the Genetics Society of America P-Element Insertion Alleles of Essential Genes on the zy Third Chromosome of z hsophila melamgader: Mutations Affecting Embryonic PNS Development Adi Salzberg,*” Sergei N. Prokopenko,*9t Yuchun He,* Peter Tsai,* Margit Pa,* Peter Maroy: David M. Glover: Peter De@’** and Hugo J. BeUen*’t College of Medicine, Houston, Texas 77030, ‘Department of Genetics, University of Szeged, Szeged, H-6701, Hungary, rm9 CRC Cell Baylor Cycle Genetics Group, Department of Anatomy and Physiology, University of Dundee, Dundee DDl 4HN, United Kingdom and **Institute of Biochemistry, Biological Research Center, Szeged, H-6726, Hungary Manuscript received March zyxwv 12, 1997 Accepted for publication July 29, 1997 *Howard Hughes Medical Institute, Department of Molecular and Human Genetics and tDeuelopmental Biology Pro ABSTRACT To identify novel genes and to isolate tagged mutations in known genes that are required for the development of the peripheral nervous system (PNS), we have screened a novel collection of 2460 strains carrying lethal or semilethal Pelement insertions on the thirdchromosome. Monoclonal antibody 22C10 was used as a marker to visualize the embryonic PNS. We identified 109 mutant strains that exhibited reproducible phenotypes in the PNS. Cytological and genetic analyses of these strains indicated that 87 mutations affect previously identified genes: tramtrack ( n zyxwvu = 18 alleles), string ( n = 15), cyclin A ( n = 13), single-minded ( n = 13), Delta ( n = 9), neuralized ( n = 4), pointed ( n = 4), extra macrochaetae (n = 4), pospero ( n = 3), tartan ( n = 2), and pebble ( n = 2). In addition, 13 mutationsaffect genes that we identified recently in a chemical mutagenesis screen designed to isolate similar mutants: hearty ( n = 3), dursotonals ( n = 2), pauarotti ( n = 2), sanpodo ( n = 2), dalmatian ( n = l), missensed ( n = 1) , senseless (n = 1) , and sticky chl zyxwvutsrqp (n = 1). The remaining nine mutations define seven novel complementation groups. The data presented here demonstrate that this collection of Pelements will be useful for the identification and cloning of novel genes on the third chromosome, since >70% of mutations identified in the screen are causedby the insertion of a Pelement. A comparison between this screen and a chemical mutagenesis screen undertaken earlier highlights the complementarityof the two types of genetic screens. A POWERFUL approach to isolate genes involved in a specific developmental process is to screen systematically for mutations that disrupt normal devel- opment. This approach has been used successfully in the fruit fly to identify genes that play a role in diverse developmental processes such as general body pat- terning (N~SSLEIN-VOLHARD and WIESCHAUS 1980) and different aspects of axonal growth (SEEGER et al. 1993; VAN VACTOR et al. 1993; KOLODZIEJ et al. 1995; MARTIN et al. 1995). More recently, this methodology has been employed in zebrafish to identify genes that affect body pattern formation, morphogenesis and behavior (for review see EISEN 1996). We have used this approach to identify genes that are required for normal pattern formation in the em- bryonic peripheral nervous system (PNS) (SALZBERG et al. 1994; KANIA et al. 1995). The embryonic PNS of Drosophila has proven to be an excellent model sys- tem to study neurogenesis, since it is relatively simple and since someof the molecular pathways underlying PNS development in the fly seem to be conserved Corresponding author: Hugo J. Bellen, Howard Hughes Medical Insti- tute,Room T630, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030. E-mail: hbellen@bcm.tmc.edu ‘Present address: Department of Genetics, Bruce Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa 31096, Israel. across animal phyla (reviewed in SALZBERC and BELLEN 1996). The anatomy of the embryonic PNS has been well studied (DAMBLY-CHAUDIERE and GHYSEN 1986; GHYSEN et al. 1986; BODMER and JAN 1987; HARTENSTEIN 1988). It consists of -650 neurons and 1200 associated non- neuronal cells. There are two major types of sensory organs: external sensory (ES) organs that function as chemoreceptors and mechanoreceptors, and chordoto- nal (Ch) organs that function as stretch or propriore- ceptors. In addition, the PNS contains multiple den- dritic (MD) neurons that are not associated with spe- cific accessory cells andarethoughttofunction in touch perception. Genes participating in PNS development in the fly were discovered in various ways. Many genes were iden- tified on the basis of altered bristle patterns in adult flies (e.g., achaete, scute, Hairless, and extra macrochaetae). Bristles are secreted by hair cells and constitute the external portion of ES organs in adults. Although the adult PNS is more elaborate than the embryonic PNS, the molecular mechanisms that govern neurogenesis seem to be similar in both systems. Indeed, genes that were initiallyidentified due to their effect on adult neu- rogenesis were later found to play a role in embryonic neurogenesis as well. Another important group of Genetics 147: 1723-1741 (December, 1997)