RESUMO
This paper reports a comparative analysis of heterochromatin organization in the sex chromosomes of the fruit fly Anastrepha. Mitotic chromosomes of eight Anastrepha species from different taxonomic groups were stained with DAPI and chromomycin A3 fluorochromes followed by C-banding. A specific sex-chromosome banding pattern was obtained for each of the analyzed species. Fluorescence in situ hybridization (FISH) was performed to investigate the chromosomal location of rDNA loci. In all cases the rDNA sequences were found to localize exclusively to the sex chromosomes. The results further extend the chromosomal knowledge of Anastrepha and allow a precise species identification.
Assuntos
Mapeamento Cromossômico , DNA Ribossômico/genética , Cromossomos Sexuais , Tephritidae/genética , Animais , Corantes , DNA Ribossômico/análise , Feminino , Hibridização In Situ , Cariotipagem , Larva , Masculino , Tephritidae/citologia , Tephritidae/crescimento & desenvolvimentoRESUMO
This paper reports the cloning and characterization in Sciara ocellaris of the gene homologous to Sex-lethal (Sxl) of Drosophila melanogaster. This gene plays the key role controlling sex determination and dosage compensation in the latter species. The Sciara Sxl gene produces a single transcript encoding a single protein in both males and females. This protein, found inside the nucleus, is expressed in all tissues. Both Sciara and Drosophila Sxl proteins are highly conserved at their two RNA-binding domains. In both Sciara sexes, the Sxl protein co-localizes with transcription-active regions dependent on RNA polymerase II but not on RNA polymerase I. It would appear that in Sciara, Sxl does not appear to play the key discriminative role in controlling sex determination and dosage compensation that it plays in Drosophila.
Assuntos
Dípteros/genética , Proteínas de Drosophila/genética , Regulação da Expressão Gênica no Desenvolvimento/fisiologia , Proteínas de Ligação a RNA/genética , Sequência de Aminoácidos , Animais , Northern Blotting , DNA Complementar , Dípteros/embriologia , Dípteros/metabolismo , Proteínas de Drosophila/biossíntese , Perfilação da Expressão Gênica , Dados de Sequência Molecular , RNA Mensageiro/metabolismo , Proteínas de Ligação a RNA/biossíntese , Alinhamento de SequênciaRESUMO
A Drosophila gene encoding a novel zinc-finger protein, Meics, was cloned using a monoclonal antibody. The predicted amino acid sequence contains 12 zinc-finger motifs of the C2H2-type. During spermatogenesis, Meics distributes intranuclearly at pre- and post-meiotic stages whereas it relocates to central-spindle microtubules at both meiotic divisions.
Assuntos
Proteínas de Ciclo Celular/metabolismo , Núcleo Celular/metabolismo , Proteínas de Ligação a DNA/metabolismo , Proteínas de Drosophila , Proteínas de Insetos/metabolismo , Meiose , Microtúbulos/metabolismo , Dedos de Zinco , Sequência de Aminoácidos , Animais , Proteínas de Ciclo Celular/química , Proteínas de Ciclo Celular/genética , Clonagem Molecular , Proteínas de Ligação a DNA/química , Proteínas de Ligação a DNA/genética , Drosophila , Genes de Insetos , Proteínas de Insetos/química , Proteínas de Insetos/genética , Masculino , Dados de Sequência Molecular , EspermatogêneseRESUMO
The programmed elimination of part of the genome through chromosome loss or chromatin diminution constitutes an exceptional biological process found to be present in several diverse groups of organisms. The occurrence of this phenomenon during early embryogenesis is generally correlated to somatic versus germ-line differentiation. A most outstanding example of chromosome elimination and genomic imprinting is found in sciarid flies, where whole chromosomes of exclusive parental origin are selectively eliminated at different developmental stages. Three types of tissue-specific chromosome elimination events occur in sciarids. During early cleavages, one or two X paternal chromosomes is/are discarded from somatic cells of embryos which then develop as females or males respectively. Thus, the sex of the embryo is determined by the number of eliminated paternal X chromosomes. In germ cells, instead, a single paternal X chromosome is eliminated in embryos of both sexes. In addition, while female meiosis is orthodox, male meiosis is highly unusual as the whole paternal chromosome set is discarded from spermatocytes. As a consequence, only maternally derived chromosomes are included in the functional sperm. This paper reviews current cytological and molecular knowledge on the tissue-specific cell mechanisms evolved to achieve chromosome elimination in sciarids.
Assuntos
Dípteros/embriologia , Dípteros/genética , Embrião não Mamífero/fisiologia , Animais , Ciclo Celular/genética , Deleção Cromossômica , Feminino , Masculino , Modelos Genéticos , Morfogênese , Cromossomo XRESUMO
In Drosophila melanogaster and in Sciara ocellaris dosage compensation occurs by hypertranscription of the single male X chromosome. This article reports the cloning and characterization in S. ocellaris of the gene homologous to maleless (mle) of D. melanogaster, which implements dosage compensation. The Sciara mle gene produces a single transcript, encoding a helicase, which is present in both male and female larvae and adults and in testes and ovaries. Both Sciara and Drosophila MLE proteins are highly conserved. The affinity-purified antibody to D. melanogaster MLE recognizes the S. ocellaris MLE protein. In contrast to Drosophila polytene chromosomes, where MLE is preferentially associated with the male X chromosome, in Sciara MLE is found associated with all chromosomes. Anti-MLE staining of Drosophila postblastoderm male embryos revealed a single nuclear dot, whereas Sciara male and female embryos present multiple intranuclear staining spots. This expression pattern in Sciara is also observed before blastoderm stage, when dosage compensation is not yet set up. The affinity-purified antibodies against D. melanogaster MSL1, MSL3, and MOF proteins involved in dosage compensation also revealed no differences in the staining pattern between the X chromosome and the autosomes in both Sciara males and females. These results lead us to propose that different proteins in Drosophila and Sciara would implement dosage compensation.
Assuntos
Proteínas Cromossômicas não Histona , DNA Helicases , Proteínas de Ligação a DNA , Dípteros/genética , Mecanismo Genético de Compensação de Dose , Proteínas de Drosophila , Drosophila melanogaster/genética , Genes de Insetos , Proteínas de Insetos/genética , RNA Helicases/genética , Fatores de Transcrição/genética , Sequência de Aminoácidos , Animais , Anticorpos Monoclonais/imunologia , Núcleo Celular/ultraestrutura , Cromossomos/química , Clonagem Molecular , Dípteros/embriologia , Drosophila melanogaster/embriologia , Embrião não Mamífero/metabolismo , Embrião não Mamífero/ultraestrutura , Feminino , Técnica Indireta de Fluorescência para Anticorpo , Regulação da Expressão Gênica no Desenvolvimento , Proteínas de Insetos/imunologia , Proteínas de Insetos/fisiologia , Masculino , Dados de Sequência Molecular , RNA Helicases/imunologia , RNA Helicases/fisiologia , Alinhamento de Sequência , Homologia de Sequência de Aminoácidos , Processos de Determinação Sexual , Especificidade da Espécie , Fatores de Transcrição/imunologia , Fatores de Transcrição/fisiologia , Transcrição Gênica , Cromossomo X/genéticaRESUMO
We have isolated a cDNA that encodes a 142 kDa protein by immunoscreening of a Schizosaccharomyces pombe expression library with a new antibody, mAb8, that reveals spindle poles and equatorial ring-like structures in several organisms. This cDNA encodes a putative protein which we termed Alm (for abnormal long morphology). The protein is predicted to be a coiled-coil protein, containing a central alpha-helical domain flanked by non-helical terminal domains. Immunofluorescence analysis showed that Alm1 is localized in the medial region of the cell from anaphase to the end of cytokinesis. Cells carrying an alm1::ura4+ disruption are viable and exhibit an elongated morphology. Homozygous alm1::ura4+ diploids sporulated normally but the spores did not germinate. Spores that have inherited the disruption allele from a heterozygous alm1+/ alm1::ura4+ diploid germinated but generated smaller colonies. We propose that Alm1 participates in the structural organization of the medial region in S. pombe.
Assuntos
Proteínas Fúngicas/genética , Genes Fúngicos , Proteínas de Schizosaccharomyces pombe , Schizosaccharomyces/genética , Sequência de Aminoácidos , Anticorpos Monoclonais , Antígenos de Fungos/genética , Sequência de Bases , Clonagem Molecular , Primers do DNA/genética , DNA Complementar/genética , DNA Fúngico/genética , Proteínas Fúngicas/química , Proteínas Fúngicas/metabolismo , Imuno-Histoquímica , Mitose , Dados de Sequência Molecular , Mutação , Fenótipo , Schizosaccharomyces/citologia , Schizosaccharomyces/metabolismoRESUMO
We have identified a 227 kDa spindle- and centromere-associated protein in Parascaris, designated PUMA1 (Parascaris univalens mitotic apparatus), using a monoclonal antibody (mAb403) generated against Parascaris embryonic extracts. PUMA1 distribution was studied by immunofluorescence microscopy in mitotic and meiotic Parascaris cells, where centromere organization differs greatly. In mitosis, PUMA1 associates throughout cell division with the centrosomes and kinetochore-microtubules, and it concentrates at the continuous centromere region of the holocentric chromosomes. PUMA1 also localizes to the spindle mid-zone region during anaphase and at the midbody during telophase. In meiosis, PUMA1 associates with the centrosomes and with the discrete centromeric regions lacking kinetochore structures. The analysis of colchicine-treated embryos indicated that the association of PUMA1 with the centromeric region depends on microtubule integrity. mAb403 also recognizes spindle components in Drosophila. A series of overlapping cDNAs encoding the gene were isolated from a Parascaris embryonic expression library. Analysis of the nucleotide sequence identified an open reading frame capable of encoding a protein of 227 kDa. Analysis of the protein sequence indicated that PUMA1 is predicted to be a coiled-coil protein containing a large central alpha-helical domain flanked by nonhelical terminal domains. The structural features and cellular distribution of PUMA1 suggest that it may play a role in the organization of the spindle apparatus and in its interaction with the centromere in Parascaris.
Assuntos
Proteínas de Ciclo Celular , Centrômero/metabolismo , Centrossomo/metabolismo , Proteínas Nucleares/metabolismo , Fuso Acromático/metabolismo , Sequência de Aminoácidos , Animais , Anticorpos Monoclonais/metabolismo , Antígenos de Helmintos/química , Antígenos de Helmintos/genética , Ascaridoidea , Sequência de Bases , DNA Complementar/química , DNA Complementar/isolamento & purificação , Drosophila melanogaster , Proteínas de Helminto/genética , Masculino , Meiose/imunologia , Mitose/imunologia , Dados de Sequência Molecular , Proteínas Nucleares/química , Proteínas Nucleares/genéticaRESUMO
Spindle formation and chromosome elimination during male meiosis in Sciara ocellaris (Diptera, Sciaridae) has been studied by immunofluorescence techniques. During meiosis I a monopolar spindle is formed from a single polar complex (centrosome-like structure). This single centrosomal structure persists during meiosis II and is responsible for the non-disjunction of the maternal X chromatids. During meiosis I and II non-spindle microtubules are assembled in the cytoplasmic bud regions of the spermatocytes. The chromosomes undergoing elimination during both meiotic divisions are segregated to the bud region where they associate with bundles of microtubules. The presence and distribution of centrosomal antigens in S. ocellaris meiotic spindles and bud regions has been investigated using different antibodies. gamma-Tubulin and centrin are present in the bud as well as in the single polar complex of first meiotic spindle. The results suggest that spermatocyte bud regions contain microtubule-organizing centres (MTOCs) that nucleate cytoplasmic microtubules that are involved in capturing chromosomes in the bud regions. The distribution of actin and myosin in the spermatocytes during meiosis is also reported.
Assuntos
Deleção Cromossômica , Dípteros/genética , Meiose/genética , Microtúbulos/fisiologia , Actinas/metabolismo , Animais , Centrossomo/metabolismo , Dípteros/citologia , Técnica Indireta de Fluorescência para Anticorpo , Masculino , Miosinas/metabolismo , Espermatócitos/metabolismo , Combinação Trimetoprima e Sulfametoxazol/imunologia , Tubulina (Proteína)/imunologiaRESUMO
We have studied the relationship between the occurrence of chromatin diminution and the developmental behavior of somatic blastomeres in early development of the nematode Parascaris univalens. A cytological and immunocytochemical analysis of chromatin diminution was performed in P. univalens embryos exposed to 'vegetalizing' (LiCl) and 'animalizing' (NaSCN) substances during early developmental stages. We have also analyzed chromatin diminution in embryos displaying only symmetrical 'somatic-like' divisions due to a brief cytochalasin B treatment at the pronuclear stage. The results show that LiCl treatment induces chromatin diminution in P0-P4 pregerminal blastomeres while NaSCN treatment prevents it. Pregerminal cells undergoing chromatin diminution in 'vegetalized' embryos behaved like somatic cells with respect to division and cleavage patterns. NaSCN treatment results in undiminuted polynucleated embryos that are not capable of cleavage. In cytochalasin B-pulsed embryos, chromatin diminution occurs in all blastomeres. From our results we conclude that chromatin diminution and somatic cell behavior are not separable and constitute strictly correlated events in Parascaris. Moreover, the results indicate that the segregation of the cytoplasmic factors involved in chromatin diminution in early Parascaris development are microfilament-mediated. Here, we also report the formation of a latter pregerminal cell precursor (P5) not susceptible to LiCl-induced chromatin diminution.
Assuntos
Cromatina/fisiologia , Nematoides/fisiologia , Animais , Diferenciação Celular , Núcleo Celular/fisiologia , Cromatina/ultraestrutura , Embrião não Mamífero/fisiologia , Nematoides/embriologiaRESUMO
The distribution of antigens to two antibodies (Bx63 and Rb188) that associate to Drosophila melanogaster centrosomes has been investigated in the nematode Parascaris. By western blot analysis both antibodies identify in Parascaris polypeptides of the same molecular mass as in Drosophila (Rb188 a 185 kDa antigen and Bx63 185 kDa and 66 kDa antigens). By immunocytochemistry we show that the centrosomes of Parascaris contain the 185 kDa antigen recognized by polyclonal Rb188 and monoclonal Bx63 antibodies. In addition, Bx63 reveals cytoplasmic midzone structures, not found in Drosophila, that display a cell cycle-dependent organization in embryos. These structures, which most probably contain the 66 kDa antigen revealed by Bx63, appear at the onset of anaphase as fibrillar-like structures that during anaphase form a ring-like structure encircling the equatorial plane of the blastomere. Before furrowing, the antigen participates in the formation of the midbody and associates with convergent polar microtubules. After blastomere division, Bx63 signal persists as a single body between the daughter cells. The analysis of chilled and nocodazole-treated embryos suggests that the localization of the midzone Bx63 antigen is dependent on non-kinetochore microtubules. Inhibition of furrowing by cytochalasin B shows that the antigen persists after the disassembly of microfilaments. Cytological observations of contractile ring and Bx63 ring assembly indicate that both structures do not simultaneously colocalize at the equatorial zone. The data suggest a spindle-dependent distribution of the Bx63 antigen during cytokinesis. We discuss the participation of this antigen in the organization of the midbody before furrowing, and consider the possible relevance of the midbody with respect to cell to cell communication during early development in nematodes.
Assuntos
Drosophila melanogaster/imunologia , Microtúbulos/ultraestrutura , Nematoides/ultraestrutura , Fuso Acromático/ultraestrutura , Citoesqueleto de Actina/ultraestrutura , Actinas/ultraestrutura , Animais , Anticorpos , Western Blotting , Citocalasina B/farmacologia , Imunofluorescência , Meiose , Microtúbulos/imunologia , Mitose , Nematoides/citologia , Nematoides/embriologia , Nocodazol/farmacologia , Fuso Acromático/imunologiaRESUMO
Chromatin diminution takes place in presomatic cells of some parasitic nematodes during early development. This phenomenon may play an important role in somatic cell differentiation, since the somatic cells of these species undergo an extensive genome reorganization during development via chromatin diminution and polyploidization, as explained here by Clara Goday and Sergio Pimpinelli.
RESUMO
In Parascaris the mitotic chromosomes of gonial germline cells are holocentric and possess a continuous kinetochore along their entire length. By contrast, in meiotic cells, the centromeric activity is restricted to the heterochromatic tips where direct insertion of spindle microtubules into chromatin without any kinetochore plate is seen. In the presomatic cells of early embryos, which undergo heterochromatin elimination, only euchromatin shows kinetic activity. After developing a technique to separate the very resistant egg shell from the embryos, we studied the cell divisions during early embryogenesis by immunochemical and EM approaches. The results reported here show that in presomatic cells microtubules bind only the euchromatin where a continuous kinetochore plate is present. We also report observations suggesting that the binding of the long kinetochores to the mitotic spindle initiates to a limited number of sites and extends along the entire length, during chromosome condensation. The existence of different centromere stages in different cell types, rends Parascaris chromosomes a very good model to study centromere organization.
Assuntos
Centrômero/metabolismo , Cromatina/metabolismo , Microtúbulos/metabolismo , Mitose/fisiologia , Nematoides/embriologia , Fuso Acromático/metabolismo , Animais , Centrômero/ultraestrutura , Cromossomos/ultraestrutura , Eucromatina , Feminino , Imunofluorescência , Células Germinativas/metabolismo , Heterocromatina/metabolismo , Tubulina (Proteína)/isolamento & purificaçãoRESUMO
The chromosomes of Parascaris univalens possess a continuous centromeric structure spanning their entire length in gonial cells. A cytological and ultrastructural analysis of P. univalens meiotic chromosomes was performed. The results show that during meiosis the holocentric germline chromosomes of male P. univalens undergo restriction of kinetic activity to the heterochromatic terminal regions. These regions lack kinetochore structures and interact directly with spindle microtubules.
Assuntos
Centrômero/ultraestrutura , Cromossomos/ultraestrutura , DNA/ultraestrutura , Meiose , Nematoides/genética , Animais , Bandeamento Cromossômico , DNA/isolamento & purificação , Imunofluorescência , Masculino , Microscopia de Fluorescência , Nematoides/ultraestrutura , Hibridização de Ácido NucleicoRESUMO
The first description of the cytogenetics of the horse parasitic nematode Ascaris megalocephala (Parascaris equorum) represented an important step in the history of genetics. The chromosomes of this organism possess a particular centromeric organization and undergo a process known as chromatin diminution in all presomatic cells during early development. Both these unusual features make Parascaris a good model to study general aspects of chromosome biology.
Assuntos
Ascaris/genética , Fuso Acromático , Animais , Cromossomos/ultraestrutura , MitoseRESUMO
Ultrastructural analysis of the centromere in germ-line mitotic chromosomes of Parascaris univalens and Parascaris equorum revealed that these chromosomes are holocentric. In thin longitudinal sections of both species the kinetochore appeared as a continuous plate (up to 3.8 micron long) and displayed a layered structure. This structure consisted of electron-dense inner and outer layers (average width 10 nm) separated by a less dense middle layer (25 nm wide), which had transverse electron-dense bars (10 nm wide) regularly spaced every 25-30 nm. Thus the ladderlike kinetochore profile observed in Parascaris gonial mitotic chromosomes represents a different type of organization from that of the classical trilaminar kinetochore found in both holocentric and monocentric chromosomes.
Assuntos
Ascaridoidea/ultraestrutura , Centrômero/ultraestrutura , Cromossomos/ultraestrutura , Animais , Microscopia Eletrônica , Mitose , Fuso Acromático/ultraestruturaRESUMO
A cytological analysis by modern banding techniques of gonial metaphases in two Parascaris forms that have been considered varieties but now seem to be two species [P. univalens (karyotype 2n = 2) and P. equorum (karyotype 2n = 4)] reveals a different chromosome organization in each. Parascaris univalens chromosomes contain only terminal heterochromatin, while P. equorum chromosomes also contain intercalary heterochromatin. In the somatic cells of both species during early embryogenesis, chromatin diminution occurs in and consists of the elimination of all heterochromatin independent of its localization in the chromosomes.
RESUMO
Two new cases of "cri du chat" syndrome are reported in sisters aged 2 years and one month, respectively. These cases allowed us to detect a translocation t(5p--;18p+) in the mother and to study the familial segregation of this structural chromosome anomaly. At the same time, results from the dermatoglyphic analysis of the propositi as well as those of the carriers of the translocation are also reported.
Assuntos
Aberrações Cromossômicas , Cromossomos Humanos 16-18 , Cromossomos Humanos 4-5 , Síndrome de Cri-du-Chat/genética , Translocação Genética , Pré-Escolar , Dermatoglifia , Feminino , Humanos , Recém-Nascido , LinhagemRESUMO
The case of a 2 1/2-month-old male child with intrauterine distrophy features and multiple congenital malformations is presented. Cytogenetic studies of the child and his parents, completed with Q- and G-banding techniques led us to conclude that it is a case of 22 trisomy inherited from his mother.
Assuntos
Cromossomos Humanos 21-22 e Y , Trissomia , Anormalidades Múltiplas/genética , Dermatoglifia , Humanos , Lactente , Masculino , Linhagem , FenótipoRESUMO
The cytogenic study is reported of a female infant affected with several malformations and presenting a mosaicism of the type 47,XX,+8/46,XX in her karyotype. G-band analysis and the distribution curves of these bands were studied in order to obtain a more objective identification of trisomy 8. Results of Q-banding, X-chromatin and dermatoglyphic studies are given and compared with previous reports.