In order to recover new mutant alleles of the Polycomb group gene Additional sex combs (Asx), mutagenized chromosomes were screened over the putative Asx allele XT129. Thirteen new mutant strains that fail to complement XT129 were recovered. Unexpectedly, the thirteen strains sorted into four complementation groups. Recombination mapping suggests that each complementation group represents a separate locus. The largest group fails to complement a deletion of Asx and maps in the vicinity of 2-72, the published location of Asx. All new mutant strains enhance the phenotype of Polycomb mutant flies and are not allelic to any previously discovered second chromosome Polycomb group genes. Therefore, the new mutants may be considered putative new members of the Polycomb group. This study suggests that Asx belongs to a sub-group of genes displaying intergenic non-complementation. / Science, Faculty of / Zoology, Department of / Graduate

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Four sibling species of the Drosophila melanogaster species subgroup (D. melanogaster, D. simulans, D. sechellia and D. mauritiana) were used to study genetic variation at the protein level by improved two-dimensional (2DE) gel electrophoresis. Three of the species, D. simulans, D. sechellia and D. mauritiana, are chromosomally homosequential, but their phylogenetic relationship to each other is a subject of controversy. Eight tissues representing adult and larval (developmental stage) and reproductive and non-reproductive tissues were analysed for protein variation. The tissues used were as follows: larval testis, brain, haemolymph, wing disc, and adult testis, accessory gland, male and female brain. Close to 400 protein spots were detected per tissue using this sensitive method. Each tissue was compared between species for protein variation. Protein variation was measured on the basis of qualitative differences (presence/ absence) of the protein spots in six pairwise species comparisons and four-way comparisons. Different levels of protein variation were detected for the same tissues in different species comparisons and each tissue showed different levels of variation in the same species. Different tissue proteins seemed to evolve independently in different species. But there was no evidence of any trend or pattern to show that either larval or adult patterns are more diverged than the other. The variation between tissues rather than developmental stages appears to be the major determinat of the level of divergence. The reproductive tract (testis and accessory gland) proteins showed more variation among species comparison than the non-reproductive tissue proteins. Among the four species, D. melanogaster testis proteins, both larval and adult, showed the maximum divergence. From the results it seems that there is a correlation between the level of reproductive tract protein divergence and the degree of reproductive isolation observed among these species. Among the other three closely related species, the levels of divergence of the reproductive tract proteins are similar, but lower than that of D. melanogaster. The phylogenetic relationship based on 2DE protein divergence showed D. simulans to be closer to D. mauritiana than to D. sechellia. / Thesis / Master of Science (MS)

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At least some areas of the embryonic blastoderm in Drosophila melanogaster appear to be determined by substances produced under control of the maternal genome without involvement of the embryonic genome. Study of mutant genes controlling the production of such morphogenic substances would provide valuable information about these substances and the nature of determination itself. In this thesis, the adult ovaries in offspring of females containing sex chromosomes originating from a wild-type strain of Drosophila melanogaster collected on Margarita Island, Venezuela have been examined. After selection on such chromosomes, over 50% of the offspring produced by homozygous females contained either one or two agametic gonads. The delayed expression is due to temperature-sensitive gene expression duringoogenesis. Two micron sections of normal and abnormal ovaries of this strain indicate the mesodermal components of the abnormal ovaries including the ovarian sheaths and the ovariole epithelial sheaths, were normal. In addition, attachment of the ovaries to the oviducts are normal. The abnormal ovarioles contain cells which appear to be mesodermally-derived follicle cells, but no normal egg chambers are seen. The germaria also contain follicle cells but no cells resembling stem cells or cystocytes are seen. It is concluded: (1) the development of ovarian germinal and mesodermal components are completely independent and (2) the mutant gene(s) prevent normal differentiation of pole cells into germ cells.

Memoria para optar al Título Profesional de Médico Veterinario / La correcta ubicación de todos los componentes sinápticos durante el desarrollo requiere del ordenamiento preciso de una red de proteínas, este ordenamiento es provisto por proteínas andamio, pertenecientes a la familia MAGUK (membrane-associated guanylate kinases). Los miembros de esta familia, reclutan receptores, canales iónicos, componentes de cascadas de transducción de señales y proteínas del citoesqueleto a través de sus dominios de interacción proteína-proteína, formando complejos macromoleculares multiproteicos asociados a membrana. Se ha descrito que el gen discs-large, de Drosophila melanogaster, codifica para, al menos, dos proteínas andamio de la famila MAGUK. La sinapsis neuromuscular de la larva de Drosophila es una sinapsis glutamatérgica. En ella la proteína andamio Discs large cumple un papel importante en la formación de la sinapsis y en la localización de proteínas involucradas en la transducción de señales. Gracias a la conservación de los procesos básicos de transmisión sináptica, la sinapsis neuromuscular de la larva de Drosophila melanogaster ha demostrado ser un excelente modelo de estudio de sinapsis centrales de mamíferos. Numerosos estudios han demostrado que Dlg determina la localización sináptica del canal de potasio tipo Shaker y de Fasciclina II (FasII), una proteína de adhesión celular involucrada en el crecimiento y plasticidad de la sinapsis neuromuscular. Además, Dlg participa en múltiples procesos, incluyendo el mantenimiento de la adhesión y polaridad apicobasal de los epitelios y la neurogénesis embrionaria. Dlg también participa en el control de la proliferación en tejido epitelial por lo que se le considera un gen supresor de tumores. Todas estas funciones, están asociadas a una única isoforma, DlgA. Sin embargo, en la sala de moscas del Laboratorio de Neurobiología Celular Molecular de la Facultad de Medicina Norte de la Universidad de Chile se aisló una serie de transcritos que corresponden a variantes de procesamiento alternativo del gen dlg que presentan en su extremo 5’ una región que codifica un segmento de 65 aminoácidos llamado S97N y que está ausente en DlgA. Las variantes de dlg que contienen S97N como la proteína denominada DlgS97, sólo se expresan en sistema nervioso y músculo, a diferencia de DlgA, que también se expresa en células epiteliales. En este estudio se describen los defectos ocasionados por el estrés térmico tanto agudo como crónico en individuos de Drosophila melanogaster que expresan variantes del gen dlg con dominio S97N, para parámetros como viabilidad, fertilidad, conducta locomotora de la larva y del adulto, y en la estructura de la sinapsis de la unión neuromuscular de la larva