Neurobiology. In the article ''ORK1, a potassium-selective leak channel with two pore domains cloned from Drosophila melanogaster by expression in Saccharomyces cerevisiae '' by Steve A. N. Goldstein, Laura A. Price, David N. Rosenthal, and Mark H. Pausch, which appeared in number 23, November 12, 1996, of Proc. Natl. Acad. Sci. USA (93, 13256-13261), the authors request that the following sequence correction be noted. We have found errors in the ORK1 nucleotide sequence reported in this work. The correct sequence extends the ORF and predicts a protein of 1001 residues; the correct nucleotide and predicted protein sequences are deposited under the GenBank accession no. U55321. The errors do not otherwise alter the conclusions of the paper. We are grateful to Noam Zilberberg (Yale Univ. School of Medicine, New Haven, CT) for his efforts to establish the correct sequence.Neurobiology. In the article "A Rap guanine nucleotide exchange factor enriched highly in the basal ganglia" by Hiroaki Kawasaki, Gregory M. Springett, Shinichiro Toki, Juan J. Canales, Patricia Harlan, Justin P. Blumenstiel, Emy J. Chen, I. Amy Bany, Naoki Mochizuki, Amy Ashbacher, Michiyuki Matsuda, David E. Housman, and Ann M. Graybiel, which appeared in number 22, October 27, 1998, of Proc. Natl. Acad. Sci. USA (95,(13278)(13279)(13280)(13281)(13282)(13283), due to a printer's error, the gene CalDAG-GEFII was referred to incorrectly in three places: in the heading of the second paragraph of Materials and Methods, in the first line of the Abbreviations footnote, and in line 11 of the second paragraph on page 13282. 318Corrections Proc. Natl. Acad. Sci. USA 96 (1999) Contributed by Ann M. Graybiel, August 20, 1998 ABSTRACT Ras proteins, key regulators of growth, differentiation, and malignant transformation, recently have been implicated in synaptic function and region-specific learning and memory functions in the brain. Rap proteins, members of the Ras small G protein superfamily, can inhibit Ras signaling through the Ras͞Raf-1͞mitogen-activated protein (MAP) kinase pathway or, through B-Raf, can activate MAP kinase. Rap and Ras proteins both can be activated through guanine nucleotide exchange factors (GEFs). Many Ras GEFs, but to date only one Rap GEF, have been identified. We now report the cloning of a brain-enriched gene, CalDAG-GEFI, which has substrate specificity for Rap1A, dual binding domains for calcium (Ca 2؉ ) and diacylglycerol (DAG), and enriched expression in brain basal ganglia pathways and their axon-terminal regions. Expression of CalDAG-GEFI activates Rap1A and inhibits Ras-dependent activation of the Erk͞MAP kinase cascade in 293T cells. Ca 2؉ ionophore and phorbol ester strongly and additively enhance this Rap1A activation. By contrast, CalDAG-GEFII, a second CalDAG-GEF family member that we cloned and found identical to

A century of genetic analysis has revealed that multiple mechanisms control the distribution of meiotic crossover events. In Drosophila melanogaster, two significant positional controls are interference and the strongly polar centromere effect. Here, we assess the factors controlling the distribution of crossovers (COs) and noncrossover gene conversions (NCOs) along all five major chromosome arms in 196 single meiotic divisions to generate a more detailed understanding of these controls on a genome-wide scale. Analyzing the outcomes of single meiotic events allows us to distinguish among different classes of meiotic recombination. In so doing, we identified 291 NCOs spread uniformly among the five major chromosome arms and 541 COs (including 52 double crossovers and one triple crossover). We find that unlike COs, NCOs are insensitive to the centromere effect and do not demonstrate interference. Although the positions of COs appear to be determined predominately by the long-range influences of interference and the centromere effect, each chromosome may display a different pattern of sensitivity to interference, suggesting that interference may not be a uniform global property. In addition, unbiased sequencing of a large number of individuals allows us to describe the formation of de novo copy number variants, the majority of which appear to be mediated by unequal crossing over between transposable elements. This work has multiple implications for our understanding of how meiotic recombination is regulated to ensure proper chromosome segregation and maintain genome stability.

Hybrid dysgenesis in Drosophila is a syndrome of gonadal atrophy, sterility, and male recombination, and it occurs in the progeny of crosses between males that harbor certain transposable elements (TEs) and females that lack them. Known examples of hybrid dysgenesis in Drosophila melanogaster result from mobilization of individual families of TEs, such as the P element, the I element, or hobo. An example of hybrid dysgenesis in Drosophila virilis is unique in that multiple, unrelated families of TEs become mobilized, but a TE designated Penelope appears to play a major role. In all known examples of hybrid dysgenesis, the paternal germ line transmits the TEs in an active state, whereas the female germ line maintains repression of the TEs. The mechanism of maternal maintenance of repression is not known. Recent evidence suggests that the molecular machinery of RNA interference may function as an important host defense against TEs. This protection is mediated by the action of endogenous small interfering RNAs (siRNAs) composed of dsRNA molecules of 21-25 nt that can target complementary transcripts for destruction. In this paper, we demonstrate that endogenous siRNA derived from the Penelope element is maternally loaded in embryos through the female germ line in D. virilis. We also present evidence that the maternal inheritance of these endogenous siRNAs may contribute to maternal repression of Penelope.hybrid dysgenesis ͉ maternal effect ͉ RNA interference ͉ transposable element

Next-generation methods for rapid whole-genome sequencing enable the identification of single-basepair mutations in Drosophila by comparing a chromosome bearing a new mutation to the unmutagenized sequence. To validate this approach, we sought to identify the molecular lesion responsible for a recessive EMS-induced mutation affecting egg shell morphology by using Illumina next-generation sequencing. After obtaining sufficient sequence from larvae that were homozygous for either wild-type or mutant chromosomes, we obtained high-quality reads for base pairs composing $70% of the third chromosome of both DNA samples. We verified 103 single-base-pair changes between the two chromosomes. Nine changes were nonsynonymous mutations and two were nonsense mutations. One nonsense mutation was in a gene, encore, whose mutations produce an egg shell phenotype also observed in progeny of homozygous mutant mothers. Complementation analysis revealed that the chromosome carried a new functional allele of encore, demonstrating that one round of next-generation sequencing can identify the causative lesion for a phenotype of interest. This new method of whole-genome sequencing represents great promise for mutant mapping in flies, potentially replacing conventional methods. S TANDARD practices of genetic mapping typically occur in three phases. First, polymorphisms that distinguish the chromosome carrying the mutation to be mapped from that of the homolog bearing a wild-type allele of that gene must be identified. Second, by genotyping recombinant chromosomes that do or do not carry the mutation of interest, an association between polymorphisms and the mutation can be identified, which can then be used to pinpoint the location of the relevant mutation. Finally, candidate genes within the interval must be identified and regions sequenced to find the causative mutation. Often, these three steps are performed iteratively. In situations where there are few polymorphic markers or candidate genes, this process can be arduous and, depending on the organism, can consume months to years.New genome-sequencing technologies (Margulies et al. 2005;Bentley 2006;Barski et al. 2007;Sarin et al. 2008;Smith et al. 2008;Valouev et al. 2008) show tremendous promise for reducing the time needed to identify causative mutations. Using these approaches, one may be able to directly identify causative lesions by comparing the nucleotide sequences of wild-type and mutant genomes. Indeed, we have conducted a proofof-principle experiment to determine the feasibility of such an approach in Drosophila melanogaster. In the course of conducting an EMS-based genetic screen, we identified a chromosome, designated 791, which displayed a fused dorsal appendage phenotype in embryos of homozygous mothers. Such phenotypes usually arise from a defect in the maternal establishment of the dorso-ventral axis. To identify the mutated gene that gives rise to this phenotype, we used a next-generation sequencing platform to directly compare the nucleotide sequence of the...