Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 17 de 17
Filtrar
Más filtros











Base de datos
Intervalo de año de publicación
1.
bioRxiv ; 2024 Aug 21.
Artículo en Inglés | MEDLINE | ID: mdl-39229242

RESUMEN

Mitosis and meiosis have two mechanisms for regulating the accuracy of chromosome segregation: error correction and the spindle assembly checkpoint (SAC). We have investigated the function of several checkpoint proteins in meiosis I of Drosophila oocytes. Evidence of a SAC response by several of these proteins is found upon depolymerization of microtubules by colchicine. However, unattached kinetochores or errors in biorientation of homologous chromosomes does not induce a SAC response. Furthermore, the metaphase I arrest does not depend on SAC genes, suggesting the APC is inhibited even if the SAC is silenced. Two SAC proteins, ROD of the ROD-ZW10-Zwilch (RZZ) complex and MPS1, are also required for the biorientation of homologous chromosomes during meiosis I, suggesting an error correction function. Both proteins aid in preventing or correcting erroneous attachments and depend on SPC105R for localization to the kinetochore. We have defined a region of SPC105R, amino acids 123-473, that is required for ROD localization and biorientation of homologous chromosomes at meiosis I. Surprisingly, ROD removal, or "streaming", is independent of the dynein adaptor Spindly and is not linked to the stabilization of end-on attachments. Instead, meiotic RZZ streaming appears to depend on cell cycle stage and may be regulated independently of kinetochore attachment or biorientation status. We also show that dynein adaptor Spindly is also required for biorientation at meiosis I, and surprisingly, the direction of RZZ streaming.

2.
PLoS Genet ; 19(11): e1011066, 2023 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-38019881

RESUMEN

The centromere is an epigenetic mark that is a loading site for the kinetochore during meiosis and mitosis. This mark is characterized by the H3 variant CENP-A, known as CID in Drosophila. In Drosophila, CENP-C is critical for maintaining CID at the centromeres and directly recruits outer kinetochore proteins after nuclear envelope break down. These two functions, however, happen at different times in the cell cycle. Furthermore, in Drosophila and many other metazoan oocytes, centromere maintenance and kinetochore assembly are separated by an extended prophase. We have investigated the dynamics of function of CENP-C during the extended meiotic prophase of Drosophila oocytes and found that maintaining high levels of CENP-C for metaphase I requires expression during prophase. In contrast, CID is relatively stable and does not need to be expressed during prophase to remain at high levels in metaphase I of meiosis. Expression of CID during prophase can even be deleterious, causing ectopic localization to non-centromeric chromatin, abnormal meiosis and sterility. CENP-C prophase loading is required for multiple meiotic functions. In early meiotic prophase, CENP-C loading is required for sister centromere cohesion and centromere clustering. In late meiotic prophase, CENP-C loading is required to recruit kinetochore proteins. CENP-C is one of the few proteins identified in which expression during prophase is required for meiotic chromosome segregation. An implication of these results is that the failure to maintain recruitment of CENP-C during the extended prophase in oocytes would result in chromosome segregation errors in oocytes.


Asunto(s)
Proteínas de Drosophila , Meiosis , Animales , Meiosis/genética , Segregación Cromosómica/genética , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Profase/genética , Centrómero/genética , Centrómero/metabolismo , Drosophila/genética , Drosophila/metabolismo , Mitosis , Cinetocoros/metabolismo , Proteína A Centromérica/genética , Proteína A Centromérica/metabolismo , Proteínas Cromosómicas no Histona/genética , Proteínas Cromosómicas no Histona/metabolismo
3.
J Cell Sci ; 134(14)2021 07 15.
Artículo en Inglés | MEDLINE | ID: mdl-34297127

RESUMEN

Meiosis in female oocytes lacks centrosomes, the microtubule-organizing centers. In Drosophila oocytes, meiotic spindle assembly depends on the chromosomal passenger complex (CPC). To investigate the mechanisms that regulate Aurora B activity, we examined the role of protein phosphatase 2A (PP2A) in Drosophila oocyte meiosis. We found that both forms of PP2A, B55 and B56, antagonize the Aurora B spindle assembly function, suggesting that a balance between Aurora B and PP2A activity maintains the oocyte spindle during meiosis I. PP2A-B56, which has a B subunit encoded by two partially redundant paralogs, wdb and wrd, is also required for maintenance of sister chromatid cohesion, establishment of end-on microtubule attachments, and metaphase I arrest in oocytes. WDB recruitment to the centromeres depends on BUBR1, MEI-S332 and kinetochore protein SPC105R. Although BUBR1 stabilizes microtubule attachments in Drosophila oocytes, it is not required for cohesion maintenance during meiosis I. We propose at least three populations of PP2A-B56 regulate meiosis, two of which depend on SPC105R and a third that is associated with the spindle.


Asunto(s)
Proteínas de Drosophila , Cinetocoros , Proteína Fosfatasa 2 , Huso Acromático , Animales , Proteínas de Ciclo Celular/genética , Segregación Cromosómica , Drosophila , Proteínas de Drosophila/genética , Femenino , Meiosis , Microtúbulos , Oocitos , Proteína Fosfatasa 2/genética
4.
J Cell Biol ; 220(6)2021 06 07.
Artículo en Inglés | MEDLINE | ID: mdl-33836043

RESUMEN

The chromosomes in the oocytes of many animals appear to promote bipolar spindle assembly. In Drosophila oocytes, spindle assembly requires the chromosome passenger complex (CPC), which consists of INCENP, Borealin, Survivin, and Aurora B. To determine what recruits the CPC to the chromosomes and its role in spindle assembly, we developed a strategy to manipulate the function and localization of INCENP, which is critical for recruiting the Aurora B kinase. We found that an interaction between Borealin and the chromatin is crucial for the recruitment of the CPC to the chromosomes and is sufficient to build kinetochores and recruit spindle microtubules. HP1 colocalizes with the CPC on the chromosomes and together they move to the spindle microtubules. We propose that the Borealin interaction with HP1 promotes the movement of the CPC from the chromosomes to the microtubules. In addition, within the central spindle, rather than at the centromeres, the CPC and HP1 are required for homologous chromosome bi-orientation.


Asunto(s)
Proteínas Cromosómicas no Histona/metabolismo , Cromosomas/genética , Drosophila melanogaster/metabolismo , Microtúbulos/metabolismo , Mitosis , Oocitos/fisiología , Animales , Aurora Quinasa B/genética , Aurora Quinasa B/metabolismo , Proteínas Cromosómicas no Histona/genética , Segregación Cromosómica , Drosophila melanogaster/genética , Drosophila melanogaster/crecimiento & desarrollo , Femenino , Cinetocoros , Masculino , Microtúbulos/genética , Oocitos/citología , Fosforilación
5.
G3 (Bethesda) ; 8(5): 1555-1569, 2018 05 04.
Artículo en Inglés | MEDLINE | ID: mdl-29514846

RESUMEN

Bipolar spindle assembly occurs in the absence of centrosomes in the oocytes of most organisms. In the absence of centrosomes in Drosophila oocytes, we have proposed that the kinesin 6 Subito, a MKLP-2 homolog, is required for establishing spindle bipolarity and chromosome biorientation by assembling a robust central spindle during prometaphase I. Although the functions of the conserved motor domains of kinesins is well studied, less is known about the contribution of the poorly conserved N- and C- terminal domains to motor function. In this study, we have investigated the contribution of these domains to kinesin 6 functions in meiosis and early embryonic development. We found that the N-terminal domain has antagonistic elements that regulate localization of the motor to microtubules. Other parts of the N- and C-terminal domains are not required for microtubule localization but are required for motor function. Some of these elements of Subito are more important for either mitosis or meiosis, as revealed by separation-of-function mutants. One of the functions for both the N- and C-terminals domains is to restrict the CPC to the central spindle in a ring around the chromosomes. We also provide evidence that CDK1 phosphorylation of Subito regulates its activity associated with homolog bi-orientation. These results suggest the N- and C-terminal domains of Subito, while not required for localization to the central spindle microtubules, have important roles regulating Subito, by interacting with other spindle proteins and promoting activities such as bipolar spindle formation and homologous chromosome bi-orientation during meiosis.


Asunto(s)
Proteínas de Drosophila/química , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/citología , Drosophila melanogaster/metabolismo , Cinesinas/química , Cinesinas/metabolismo , Meiosis , Secuencia de Aminoácidos , Animales , Proteína Quinasa CDC2/metabolismo , Proteínas Cromosómicas no Histona/metabolismo , Cromosomas/metabolismo , Secuencia Conservada , Análisis Mutacional de ADN , Femenino , Metafase , Microtúbulos/metabolismo , Mutación/genética , Oocitos/metabolismo , Fenotipo , Fosforilación , Dominios Proteicos , Transporte de Proteínas , Serina/metabolismo , Huso Acromático/metabolismo , Transgenes
6.
Genetics ; 192(2): 417-29, 2012 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-22865736

RESUMEN

During meiosis in the females of many species, spindle assembly occurs in the absence of the microtubule-organizing centers called centrosomes. In the absence of centrosomes, the nature of the chromosome-based signal that recruits microtubules to promote spindle assembly as well as how spindle bipolarity is established and the chromosomes orient correctly toward the poles is not known. To address these questions, we focused on the chromosomal passenger complex (CPC). We have found that the CPC localizes in a ring around the meiotic chromosomes that is aligned with the axis of the spindle at all stages. Using new methods that dramatically increase the effectiveness of RNA interference in the germline, we show that the CPC interacts with Drosophila oocyte chromosomes and is required for the assembly of spindle microtubules. Furthermore, chromosome biorientation and the localization of the central spindle kinesin-6 protein Subito, which is required for spindle bipolarity, depend on the CPC components Aurora B and Incenp. Based on these data we propose that the ring of CPC around the chromosomes regulates multiple aspects of meiotic cell division including spindle assembly, the establishment of bipolarity, the recruitment of important spindle organization factors, and the biorientation of homologous chromosomes.


Asunto(s)
Cromosomas/genética , Drosophila melanogaster/genética , Puntos de Control de la Fase M del Ciclo Celular/genética , Microtúbulos/genética , Animales , Aurora Quinasas , Centrosoma , Proteínas Cromosómicas no Histona/genética , Proteínas de Drosophila/genética , Drosophila melanogaster/citología , Femenino , Cinesinas/genética , Meiosis/genética , Oocitos/citología , Proteínas Serina-Treonina Quinasas/genética , Interferencia de ARN
7.
Methods Mol Biol ; 558: 197-216, 2009.
Artículo en Inglés | MEDLINE | ID: mdl-19685326

RESUMEN

Methods are described to analyze two different parts of the Drosophila ovary, which correspond to early stages (pachytene) and late stages (metaphase I and beyond) of meiosis. In addition to taking into account morphology, the techniques differ by fixation conditions and the method to isolate the tissue. Most of these methods are whole mounts, which preserve the three-dimensional structure.


Asunto(s)
Técnicas Citológicas/métodos , Drosophila/citología , Meiosis/fisiología , Ovario/citología , Animales , Análisis Citogenético/métodos , Drosophila/genética , Embrión no Mamífero/citología , Femenino , Meiosis/genética , Modelos Biológicos , Ovario/metabolismo , Fijación del Tejido/métodos
8.
Development ; 135(19): 3239-46, 2008 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-18755775

RESUMEN

Spindle formation in female meiosis differs from mitosis in many animals, as it takes place independently of centrosomes, and the molecular requirements of this pathway remain to be understood. Here, we report two crucial roles of Incenp, an essential subunit of the chromosomal passenger complex (the Aurora B complex), in centrosome-independent spindle formation in Drosophila female meiosis. First, the initial assembly of spindle microtubules is drastically delayed in an incenp mutant. This clearly demonstrates, for the first time, a crucial role for Incenp in chromosome-driven spindle microtubule assembly in living oocytes. Additionally, Incenp is necessary to stabilise the equatorial region of the metaphase I spindle, in contrast to mitosis, where the equivalent function becomes prominent after anaphase onset. Our analysis suggests that Subito, a kinesin-6 protein, cooperates with Incenp for this latter function, but not in microtubule assembly. We propose that the two functions of Incenp are part of the mechanisms that compensate for the lack of centrosomes during meiotic spindle formation.


Asunto(s)
Proteínas Cromosómicas no Histona/fisiología , Proteínas de Drosophila/fisiología , Drosophila/citología , Drosophila/fisiología , Meiosis/fisiología , Animales , Animales Modificados Genéticamente , Centrosoma/fisiología , Proteínas Cromosómicas no Histona/genética , Drosophila/genética , Proteínas de Drosophila/genética , Femenino , Genes de Insecto , Cinesinas/fisiología , Meiosis/genética , Metafase/genética , Metafase/fisiología , Microtúbulos/fisiología , Mutación
9.
Genetics ; 177(1): 267-80, 2007 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-17660552

RESUMEN

Bipolar spindles assemble in the absence of centrosomes in the oocytes of many species. In Drosophila melanogaster oocytes, the chromosomes have been proposed to initiate spindle assembly by nucleating or capturing microtubules, although the mechanism is not understood. An important contributor to this process is Subito, which is a kinesin-6 protein that is required for bundling interpolar microtubules located within the central spindle at metaphase I. We have characterized the domains of Subito that regulate its activity and its specificity for antiparallel microtubules. This analysis has revealed that the C-terminal domain may interact independently with microtubules while the motor domain is required for maintaining the interaction with the antiparallel microtubules. Surprisingly, deletion of the N-terminal domain resulted in a Subito protein capable of promoting the assembly of bipolar spindles that do not include centrosomes or chromosomes. Bipolar acentrosomal spindle formation during meiosis in oocytes may be driven by the bundling of antiparallel microtubules. Furthermore, these experiments have revealed evidence of a nuclear- or chromosome-based signal that acts at a distance to activate Subito. Instead of the chromosomes directly capturing microtubules, signals released upon nuclear envelope breakdown may activate proteins like Subito, which in turn bundles together microtubules.


Asunto(s)
Centrosoma/fisiología , Cromosomas , Proteínas de Drosophila/genética , Cinesinas/genética , Oocitos/fisiología , Huso Acromático/fisiología , Animales , Animales Modificados Genéticamente , Western Blotting , Proteínas de Drosophila/metabolismo , Drosophila melanogaster , Femenino , Técnica del Anticuerpo Fluorescente , Infertilidad , Cinesinas/metabolismo , Masculino , Meiosis , Metafase , Microtúbulos/fisiología , Mutación , Oocitos/citología , Fenotipo
10.
J Cell Sci ; 119(Pt 22): 4770-80, 2006 Nov 15.
Artículo en Inglés | MEDLINE | ID: mdl-17077127

RESUMEN

Drosophila Subito is a kinesin 6 family member and ortholog of mitotic kinesin-like protein (MKLP2) in mammalian cells. Based on the previously established requirement for Subito in meiotic spindle formation and for MKLP2 in cytokinesis, we investigated the function of Subito in mitosis. During metaphase, Subito localized to microtubules at the center of the mitotic spindle, probably interpolar microtubules that originate at the poles and overlap in antiparallel orientation. Consistent with this localization pattern, subito mutants improperly assembled microtubules at metaphase, causing activation of the spindle assembly checkpoint and lagging chromosomes at anaphase. These results are the first demonstration of a kinesin 6 family member with a function in mitotic spindle assembly, possibly involving the interpolar microtubules. However, the role of Subito during mitotic anaphase resembles other kinesin 6 family members. Subito localizes to the spindle midzone at anaphase and is required for the localization of Polo, Incenp and Aurora B. Genetic evidence suggested that the effects of subito mutants are attenuated as a result of redundant mechanisms for spindle assembly and cytokinesis. For example, subito double mutants with ncd, polo, Aurora B or Incenp mutations were synthetic lethal with severe defects in microtubule organization.


Asunto(s)
Proteínas de Drosophila/fisiología , Drosophila/fisiología , Cinesinas/fisiología , Huso Acromático/fisiología , Anafase/fisiología , Animales , Aurora Quinasas , Proteínas Cromosómicas no Histona/fisiología , Cromosomas/fisiología , Citocinesis/fisiología , Proteínas de Drosophila/genética , Cinesinas/genética , Larva , Metafase/fisiología , Microtúbulos/fisiología , Mutación , Unión Proteica , Proteínas Serina-Treonina Quinasas/fisiología
11.
Curr Biol ; 16(14): 1441-6, 2006 Jul 25.
Artículo en Inglés | MEDLINE | ID: mdl-16860744

RESUMEN

Activation of mature oocytes initiates development by releasing the prior arrest of female meiosis, degrading certain maternal mRNAs while initiating the translation of others, and modifying egg coverings. In vertebrates and marine invertebrates, the fertilizing sperm triggers activation events through a rise in free calcium within the egg. In insects, egg activation occurs independently of sperm and is instead triggered by passage of the egg through the female reproductive tract ; it is unknown whether calcium signaling is involved. We report here that mutations in sarah, which encodes an inhibitor of the calcium-dependent phosphatase calcineurin, disrupt several aspects of egg activation in Drosophila. Eggs laid by sarah mutant females arrest in anaphase of meiosis I and fail to fully polyadenylate and translate bicoid mRNA. Furthermore, sarah mutant eggs show elevated cyclin B levels, indicating a failure to inactivate M-phase promoting factor (MPF). Taken together, these results demonstrate that calcium signaling is involved in Drosophila egg activation and suggest a molecular mechanism for the sarah phenotype. We also find the conversion of the sperm nucleus into a functional male pronucleus is compromised in sarah mutant eggs, indicating that the Drosophila egg's competence to support male pronuclear maturation is acquired during activation.


Asunto(s)
Proteínas de Drosophila/fisiología , Drosophila/metabolismo , Péptidos y Proteínas de Señalización Intracelular/fisiología , Óvulo/crecimiento & desarrollo , Anafase/genética , Animales , Proteínas de Unión al Calcio , Núcleo Celular/metabolismo , Núcleo Celular/ultraestructura , Ciclina B/metabolismo , Drosophila/genética , Drosophila/fisiología , Proteínas de Drosophila/genética , Femenino , Fertilidad/genética , Péptidos y Proteínas de Señalización Intracelular/genética , Masculino , Meiosis/fisiología , Modelos Biológicos , Mutación , Óvulo/citología , Óvulo/metabolismo , Poliadenilación , Biosíntesis de Proteínas , ARN Mensajero/metabolismo , Espermatozoides/citología , Espermatozoides/ultraestructura , Membrana Vitelina/metabolismo
12.
Genetics ; 169(2): 767-81, 2005 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-15545646

RESUMEN

In the pairing-site model, specialized regions on each chromosome function to establish meiotic homolog pairing. Analysis of these sites could provide insights into the mechanism used by Drosophila females to form a synaptonemal complex (SC) in the absence of meiotic recombination. These specialized sites were first established on the X chromosome by noting that there were barriers to crossover suppression caused by translocation heterozygotes. These sites were genetically mapped and proposed to be pairing sites. By comparing the cytological breakpoints of third chromosome translocations to their patterns of crossover suppression, we have mapped two sites on chromosome 3R. We have performed experiments to determine if these sites have a role in meiotic homolog pairing and the initiation of recombination. Translocation heterozygotes exhibit reduced gene conversion within the crossover-suppressed region, consistent with an effect on the initiation of meiotic recombination. To determine if homolog pairing is disrupted in translocation heterozygotes, we used fluorescent in situ hybridization to measure the extent of homolog pairing. In wild-type oocytes, homologs are paired along their entire lengths prior to accumulation of the SC protein C(3)G. Surprisingly, translocation heterozygotes exhibited homolog pairing similar to wild type within the crossover-suppressed regions. This result contrasted with our observations of c(3)G mutant females, which were found to be defective in pairing. We propose that each Drosophila chromosome is divided into several domains by specialized sites. These sites are not required for homolog pairing. Instead, the initiation of meiotic recombination requires continuity of the meiotic chromosome structure within each of these domains.


Asunto(s)
Cromosomas , Drosophila/fisiología , Meiosis , Recombinación Genética , Animales , Rotura Cromosómica , Mapeo Cromosómico , Emparejamiento Cromosómico , Intercambio Genético , Drosophila/citología , Drosophila/genética , Femenino , Heterocigoto , Hibridación Fluorescente in Situ , Masculino , Modelos Genéticos , Mutación , Oocitos/citología , Oocitos/metabolismo , Cromosoma X
13.
J Cell Sci ; 116(Pt 15): 3069-77, 2003 Aug 01.
Artículo en Inglés | MEDLINE | ID: mdl-12799415

RESUMEN

The relationship between synaptonemal complex formation (synapsis) and double-strand break formation (recombination initiation) differs between organisms. Although double-strand break creation is required for normal synapsis in Saccharomyces cerevisiae and the mouse, it is not necessary for synapsis in Drosophila and Caenorhabditis elegans. To investigate the timing of and requirements for double-strand break formation during Drosophila meiosis, we used an antibody that recognizes a histone modification at double-strand break sites, phosphorylation of HIS2AV (gamma-HIS2AV). Our results support the hypothesis that double-strand break formation occurs after synapsis. Interestingly, we detected a low (10-25% of wildtype) number of gamma-HIS2AV foci in c(3)G mutants, which fail to assemble synaptonemal complex, suggesting that there may be both synaptonemal complex-dependent and synaptonemal complex-independent mechanisms for generating double-strand breaks. Furthermore, mutations in Drosophila Rad54 (okr) and Rad51 (spnB) homologs cause delayed and prolonged gamma-HIS2AV staining, suggesting that double-strand break repair is delayed but not eliminated in these mutants. There may also be an interaction between the recruitment of repair proteins and phosphorylation.


Asunto(s)
Emparejamiento Cromosómico/genética , ADN/genética , Recombinación Genética/genética , Complejo Sinaptonémico/metabolismo , Animales , ADN/metabolismo , ADN Helicasas , Proteínas de Unión al ADN/genética , Proteínas de Drosophila/genética , Drosophila melanogaster/genética , Drosophila melanogaster/metabolismo , Proteínas del Huevo/genética , Femenino , Inmunohistoquímica , Mutación , Fosforilación , Recombinasa Rad51 , Complejo Sinaptonémico/genética
14.
Annu Rev Genet ; 36: 205-32, 2002.
Artículo en Inglés | MEDLINE | ID: mdl-12429692

RESUMEN

In this review, we describe the pathway for generating meiotic crossovers in Drosophila melanogaster females and how these events ensure the segregation of homologous chromosomes. As appears to be common to meiosis in most organisms, recombination is initiated with a double-strand break (DSB). The interesting differences between organisms appear to be associated with what chromosomal events are required for DSBs to form. In Drosophila females, the synaptonemal complex is required for most DSB formation. The repair of these breaks requires several DSB repair genes, some of which are meiosis-specific, and defects at this stage can have effects downstream on oocyte development. This has been suggested to result from a checkpoint-like signaling between the oocyte nucleus and gene products regulating oogenesis. Crossovers result from genetically controlled modifications to the DSB repair pathway. Finally, segregation of chromosomes joined by a chiasma requires a bipolar spindle. At least two kinesin motor proteins are required for the assembly of this bipolar spindle, and while the meiotic spindle lacks traditional centrosomes, some centrosome components are found at the spindle poles.


Asunto(s)
Cromosomas , Drosophila/genética , Meiosis/genética , Recombinación Genética/genética , Animales , Femenino
15.
Genetics ; 162(1): 245-58, 2002 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-12242237

RESUMEN

Double-strand breaks (DSB) initiate meiotic recombination in a variety of organisms. Here we present genetic evidence that the mei-P22 gene is required for the induction of DSBs during meiotic prophase in Drosophila females. Strong mei-P22 mutations eliminate meiotic crossing over and suppress the sterility of DSB repair-defective mutants. Interestingly, crossing over in mei-P22 mutants can be restored to almost 50% of wild-type by X irradiation. In addition, an antibody-based assay was used to demonstrate that DSBs are not formed in mei-P22 mutants. This array of phenotypes is identical to that of mei-W68 mutants; mei-W68 encodes the Drosophila Spo11 homolog that is proposed to be an enzyme required for DSB formation. Consistent with a direct role in DSB formation, mei-P22 encodes a basic 35.7-kD protein, which, when examined by immunofluorescence, localizes to foci on meiotic chromosomes. MEI-P22 foci appear transiently in early meiotic prophase, which is when meiotic recombination is believed to initiate. By using an antibody to C(3)G as a marker for synaptonemal complex (SC) formation, we observed that SC is present before MEI-P22 associates with the chromosomes, thus providing direct evidence that the development of SC precedes the initiation of meiotic recombination. Similarly, we found that MEI-P22 foci did not appear in a c(3)G mutant in which SC does not form, suggesting that DSB formation is dependent on SC formation in Drosophila. We propose that MEI-P22 interacts with meiosis-specific chromosome proteins to facilitate DSB creation by MEI-W68.


Asunto(s)
Drosophila melanogaster/citología , Meiosis , Recombinación Genética , Alelos , Secuencia de Aminoácidos , Animales , Reparación del ADN , Drosophila melanogaster/genética , Datos de Secuencia Molecular , ARN/genética , Procesamiento Postranscripcional del ARN
16.
Genetics ; 160(4): 1489-501, 2002 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-11973304

RESUMEN

The female meiotic spindle lacks a centrosome or microtubule-organizing center in many organisms. During cell division, these spindles are organized by the chromosomes and microtubule-associated proteins. Previous studies in Drosophila melanogaster implicated at least one kinesin motor protein, NCD, in tapering the microtubules into a bipolar spindle. We have identified a second Drosophila kinesin-like protein, SUB, that is required for meiotic spindle function. At meiosis I in males and females, sub mutations affect only the segregation of homologous chromosomes. In female meiosis, sub mutations have a similar phenotype to ncd; even though chromosomes are joined by chiasmata they fail to segregate at meiosis I. Cytological analyses have revealed that sub is required for bipolar spindle formation. In sub mutations, we observed spindles that were unipolar, multipolar, or frayed with no defined poles. On the basis of these phenotypes and the observation that sub mutations genetically interact with ncd, we propose that SUB is one member of a group of microtubule-associated proteins required for bipolar spindle assembly in the absence of the centrosomes. sub is also required for the early embryonic divisions but is otherwise dispensable for most mitotic divisions.


Asunto(s)
Proteínas de Drosophila/genética , Drosophila melanogaster/genética , Cinesinas/genética , Meiosis/fisiología , Huso Acromático/metabolismo , Secuencia de Aminoácidos , Animales , Segregación Cromosómica/fisiología , Proteínas de Drosophila/fisiología , Drosophila melanogaster/embriología , Femenino , Cinesinas/metabolismo , Cinesinas/fisiología , Proteínas de Microtúbulos/metabolismo , Mitosis/fisiología , Datos de Secuencia Molecular , No Disyunción Genética , Oocitos/citología , Oocitos/metabolismo , Alineación de Secuencia , Análisis de Secuencia de ADN , Análisis de Secuencia de Proteína
17.
Mol Biol Cell ; 13(1): 84-95, 2002 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-11809824

RESUMEN

During Drosophila oogenesis, the oocyte is formed within a 16-cell cyst immediately after four incomplete cell divisions. One of the primary events in oocyte development is meiotic recombination. Here, we report the intracellular localization of the MEI-218 protein that is specifically required for meiotic crossing-over. To understand the role of mei-218 in meiosis and to study the regulation of genes required for meiotic recombination, we characterized the expression pattern of its RNA and protein. Furthermore, we cloned and sequenced mei-218 from two other Drosophila species. The mei-218 RNA and protein have a similar expression pattern, appearing first in early meiotic prophase and then rapidly disappearing as prophase is completed. This pattern corresponds to a specific appearance of the mei-218 gene product in the region of the ovary where meiotic prophase occurs. Although mei-218 is required for 95% of all crossovers, the protein is found exclusively in the cytoplasm. Based on these results, we suggest that mei-218 does not have a direct role in recombination but rather regulates other factors required for the production of crossovers. We propose that mei-218 is a molecular link between oocyte differentiation and meiosis.


Asunto(s)
Proteínas de Ciclo Celular/genética , Proteínas de Ciclo Celular/metabolismo , Intercambio Genético , Drosophila/genética , Evolución Molecular , Regiones no Traducidas 3'/metabolismo , Secuencia de Aminoácidos , Animales , Proteínas de Ciclo Celular/química , Proteínas de Ciclo Celular/inmunología , Secuencia Conservada , Citoplasma/química , Drosophila/embriología , Drosophila/metabolismo , Proteínas de Drosophila/química , Proteínas de Drosophila/genética , Proteínas de Drosophila/inmunología , Proteínas de Drosophila/metabolismo , Femenino , Regulación del Desarrollo de la Expresión Génica , Hibridación in Situ , Meiosis , Microscopía Confocal , Mutación , Oogénesis , Ovario/citología , Fenotipo , Homología de Secuencia de Aminoácido , Transcripción Genética
SELECCIÓN DE REFERENCIAS
DETALLE DE LA BÚSQUEDA