Asunto(s)
Proteínas de Drosophila , Proteínas de Insectos/genética , Proteínas Nucleares , Proteínas Quinasas , Proteínas/genética , Factores de Transcripción , Animales , Exones , Etiquetas de Secuencia Expresada , Genes de Insecto , Humanos , Intrones , Datos de Secuencia Molecular , Secuencias Repetitivas de Aminoácido , Especificidad de la EspecieRESUMEN
The first step in ecdysteroidogenesis, i.e. the 7,8-dehydrogenation of dietary cholesterol (C) to 7-dehydrocholesterol (7dC), is blocked in Drosophila melanogaster homozygous woc (without children) third instar larval ring glands (source of ecdysone). Unlike ring glands from wild-type D. melanogaster larvae, glands from woc mutants cannot convert radiolabelled C or 25-hydroxycholesterol (25C) to 7dC or 7-dehydro-25-hydroxycholesterol (7d25C) in vitro, nor to ecdysone (E). Yet, when these same glands are incubated with synthetic tracer 7d25C, the rate of metabolism of this polar Delta(5,7)-sterol into E is identical to that observed with glands from comparably staged wild-type larvae. The absence of this enzymatic activity in vivo is probably the direct cause of the observed low whole-body ecdysteroid titers in late third instar homozygous mutant larvae, the low ecdysteroid secretory activity in vitro of brain-ring gland complexes from these animals, and the failure of the larvae to pupariate (undergo metamorphosis). Oral administration of 7dC, but not C, results in a dramatic increase in ecdysteroid production both in vivo and in vitro by the woc mutant brain-ring gland complexes and affects a partial rescue to the beginning of pupal-adult development, but no further, despite elevated whole-body ecdysteroid titers. Data previously reported (Wismar et al., 2000) indicate that the woc gene encodes a zinc-finger protein that apparently modulates the activity of the 7,8-dehydrogenase.
Asunto(s)
Proteínas de Drosophila , Drosophila melanogaster/genética , Drosophila melanogaster/metabolismo , Ecdisona/biosíntesis , Regulación de la Expresión Génica , Proteínas de Insectos/genética , Animales , Encéfalo/metabolismo , Cromatografía Líquida de Alta Presión , Proteínas de Unión al ADN , Ecdisona/análisis , Ecdisona/genética , Ecdisteroides , Genotipo , Proteínas de Insectos/fisiología , Larva/crecimiento & desarrollo , Larva/metabolismo , Mutación/genética , Esteroides/biosíntesis , Esteroides/metabolismo , Factores de TranscripciónRESUMEN
Larvae homozygous for the recessive lethal allele without children(rgl) (woc(rgl)) fail to pupariate. Application of exogenous 20-hydroxyecdysone elicits puparium formation and pupation. Ecdysteroid titer measurements on mutant larvae show an endocrine deficiency in the brain-ring gland complex, which normally synthesizes ecdysone, resulting in a failure of the larvae to achieve a threshold whole body hormone titer necessary for molting. Ultrastructural investigation revealed extensive degeneration of the prothoracic cells of the ring gland in older larvae. The woc gene, located in polytene chromosomal region 97F, consists of 11 exons. A 6.8-kb transcript is expressed throughout development but is absent in the mutant woc(rgl) larvae. The woc gene encodes a protein of 187 kDa. Eight zinc fingers of the C2-C2 type point to a possible function as a transcription factor. The woc protein shows considerable homology to human proteins which have been implicated in both mental retardation and a leukemia/lymphoma syndrome.
Asunto(s)
Proteínas de Drosophila , Drosophila melanogaster/genética , Proteínas de Insectos/genética , Larva/metabolismo , Esteroides/metabolismo , Alelos , Secuencia de Aminoácidos , Animales , Secuencia de Bases , ADN Complementario , Proteínas de Unión al ADN , Drosophila melanogaster/embriología , Drosophila melanogaster/crecimiento & desarrollo , Ecdisteroides , Homocigoto , Humanos , Proteínas de Insectos/metabolismo , Larva/ultraestructura , Microscopía Electrónica , Datos de Secuencia Molecular , Mutagénesis , Fenotipo , Esteroides/biosíntesis , Factores de TranscripciónRESUMEN
Nuclear lamins are thought to play an important role in disassembly and reassembly of the nucleus during mitosis. Here, we describe a Drosophila lamin Dm0 mutant resulting from a P element insertion into the first intron of the Dm0 gene. Homozygous mutant animals showed a severe phenotype including retardation in development, reduced viability, sterility, and impaired locomotion. Immunocytochemical and ultrastructural analysis revealed that reduced lamin Dm0 expression caused an enrichment of nuclear pore complexes in cytoplasmic annulate lamellae and in nuclear envelope clusters. In several cells, particularly the densely packed somata of the central nervous system, defective nuclear envelopes were observed in addition. All aspects of the mutant phenotype were rescued upon P element-mediated germline transformation with a lamin Dm0 transgene. These data constitute the first genetic proof that lamins are essential for the structural organization of the cell nucleus.
Asunto(s)
Proteínas de Drosophila , Drosophila/genética , Membrana Nuclear/química , Membrana Nuclear/metabolismo , Proteínas Nucleares/genética , Animales , Secuencia de Bases , Química Encefálica , Citoplasma/química , Citoplasma/metabolismo , Drosophila/química , Drosophila/metabolismo , Embrión no Mamífero/fisiología , Fertilidad/genética , Técnica del Anticuerpo Fluorescente Indirecta , Regulación del Desarrollo de la Expresión Génica/fisiología , Genes de Insecto/fisiología , Mutación de Línea Germinal/fisiología , Homocigoto , Intrones/genética , Laminas , Locomoción/genética , Microscopía Electrónica , Microtomía , Datos de Secuencia Molecular , Mutagénesis Insercional/fisiología , Membrana Nuclear/ultraestructura , Proteínas Nucleares/inmunología , Fenotipo , Transformación Genética/fisiologíaRESUMEN
Of the 28 presently known Drosophila tumor suppressor genes we present the status of the functional analysis of the following three genes: (a) lethal (3) malignant brain tumor [1(3)mbt], which by homology belongs to the Pc-G gene family and may be involved in the stable silencing of specific developmental genes by changing the chromatin structure, and thus establishing and maintaining the differentiated state; (b) lethal (3) malignant blood neoplasm-1 [1(3)mbn-1], for whose function only vague predictions can be made; 4) benign (2) gonial cell neoplasm [b(2)gcn], which may function as a splice factor. Each Drosophila tumor suppressor gene transforms in the homozygously mutated state either one or two specific cell-types in a single step, and is thus the primary cause for tumorigenesis. For one of the genes a putative human homologue has been found.
Asunto(s)
Drosophila/genética , Regulación del Desarrollo de la Expresión Génica/genética , Regulación Neoplásica de la Expresión Génica/genética , Genes Supresores de Tumor/genética , Animales , Mutagénesis , Neoplasias/genética , Transformación Genética/genéticaRESUMEN
Tumor suppressor genes of Drosophila are developmental genes which, in the homozygously mutated state, induce in one step malignant or benign neoplastic transformation of specific cell types. They act early in development and by this set the stage for cell specific differentiation of imaginal discs, adult optic neuroblasts, blood and gonial cells. The structure, expression and possible function of the following four tumor suppressor genes are discussed: tumorous imaginal disc, lethal (3) malignant brain tumor, lethal (3) malignant blood neoplasm-1 and benign (2) gonial cell neoplasm.
Asunto(s)
Drosophila/genética , Genes de Insecto , Genes Supresores de Tumor , Animales , Drosophila/crecimiento & desarrollo , Femenino , Proteínas del Choque Térmico HSP40 , Proteínas de Choque Térmico/genética , Masculino , Chaperonas Moleculares/genética , Familia de Multigenes , Dedos de Zinc/genéticaRESUMEN
The lethal(3)malignant brain tumor [t(3)mbt] gene causes, when mutated, malignant growth of the adult optic neuroblasts and ganglion mother cells in the larval brain and imaginal disc overgrowth. Via overlapping deficiencies a genomic region of approximately 6.0 kb was identified, containing l(3)mbt+ gene sequences. The l(3)mbt+ gene encodes seven transcripts of 5.8 kb, 5.65 kb, 5.35 kb, 5.25 kb, 5.0 kb, 4.4 kb and 1.8 kb. The putative MBT163 protein, encompassing 1477 amino acids, is proline-rich and contains a novel zinc finger. In situ hybridizations of whole mount embryos and larval tissues revealed l(3)mbt+ RNA ubiquitously present in stage 1 embryos and throughout embryonic development in most tissues. In third instar larvae l(3)mbt+ RNA is detected in the adult optic anlagen and the imaginal discs, the tissues directly affected by l(3)mbt mutations, but also in tissues, showing normal development in the mutant, such as the gut, the goblet cells and the hematopoietic organs.
Asunto(s)
Neoplasias Encefálicas/genética , Drosophila melanogaster/genética , Genes de Insecto , Genes Letales , Genes Supresores de Tumor , Genoma , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Drosophila melanogaster/embriología , Femenino , Código Genético , Larva/genética , Masculino , Datos de Secuencia Molecular , Péptidos/genética , Fenotipo , Prolina , Dominios Proteicos Ricos en Prolina , Dedos de ZincRESUMEN
The recessive-lethal, temperature-sensitive (ts) mutation of the tumor suppressor gene lethal(3)malignant brain tumor (l(3)mbt) causes in a single step the malignant transformation of the adult optic neuroblasts and ganglion mother cells in the larval brain at the restrictive temperature of 29 degrees C. The transformed cells are differentiation-incompetent and grow autonomously in a lethal and invasive fashion in situ in the brain as well as after transplantation in vivo into wild-type adult hosts. The imaginal discs show epithelial overgrowth. At the permissive temperature of 22 degrees C development is completely normal. The ts-period of gene activity responsible for 100% brain tumor suppression and normal imaginal disc development encompasses the first six hours of embryonic development. The l(3)mbt gene function is, however, also required thereafter for the proper differentiation of the brain and the imaginal discs. The l(3)mbt gene is located cytologically in the salivary gland chromosome bands 97E8-F11, and in molecular terms in 29 kb of DNA detected via a P-element insertional deletion.
Asunto(s)
Neoplasias Encefálicas/genética , Drosophila melanogaster/genética , Genes Supresores de Tumor , Animales , Mapeo Cromosómico , Ganglios/embriología , Genes Letales , Calor , Lóbulo Óptico de Animales no Mamíferos/anatomía & histología , Lóbulo Óptico de Animales no Mamíferos/embriología , Células MadreRESUMEN
Six Drosophila melanogaster tumor suppressor genes causing malignant or benign tumors in specific cell types are described. The wild-type alleles of these genes are instrumental in the differentiation of particular cell types. In the homozygous state, recessive mutations in the genes interrupt the differentiation of the cells and thus cause their uncontrolled, autonomous, lethal proliferation. The tumors show all major characteristics of malignant and benign neoplastic growth. Genomic sequences of four of the genes have been identified and are currently being characterized.