Centriole translocation and degeneration during ciliogenesis in Caenorhabditis elegans neurons

Neuronal cilia that are formed at the dendritic endings of sensory neurons are essential for sensory perception. However, it remains unclear how the centriole‐derived basal body is positioned to form a template for cilium formation. Using fluorescence time‐lapse microscopy, we show that the centriole translocates from the cell body to the dendrite tip in the Caenorhabditis elegans sensory neurons. The centriolar protein SAS‐5 interacts with the dynein light‐chain LC8 and conditional mutations of cytoplasmic dynein‐1 block centriole translocation and ciliogenesis. The components of the central tube are essential for the biogenesis of centrioles, which later drive ciliogenesis in the dendrite; however, the centriole loses these components at the late stage of centriole translocation and subsequently recruits transition zone and intraflagellar transport proteins. Together, our results provide a comprehensive model of ciliogenesis in sensory neurons and reveal the importance of the dynein‐dependent centriole translocation in this process.     

Neck region of gerbil spermatozoa

In the course of the reorganization and degeneration of the proximal centriole in the mature acentriolate spermatozoon of the Mongolian gerbil, both the proximal and distal centrioles appear in the early cap phase of spermatid development. During the acrosome phase, both distal and proximal centrioles become highly active in the formation of a segmented column. The proximal centriole becomes actively involved in the formation of the capitulum, while the distal centriole forms the axonemal complex and dense fibers. During the maturation phase of spermatid development, the “pinwheel” arrangement of the proximal centriole becomes an “S”-shaped structure, turned 90° on its vertical axis. The few “doublet” microtubules that can be detected later in that stage completely disappear during spermiation. The distal centriolar area develops a single central pair of microtubules and membranous elements. Another prominent feature in the neck region of the gerbil spermatozoa is the presence of two dense rudimentary columns in association with the mitochondria. Although their density is similar to that of the other columns, these two columns have no connection with the dense fibers; in fact, they are closely associated with the mitochondria.     

Glycosidases are present on the surface of Drosophila melanogaster spermatozoa

We investigated the presence of enzymes on the surface of Drosophila melanogaster spermatozoa that might bind to the carbohydrate residues of the egg shell. Spectrophotometric and fluorimetric studies were used on whole spermatozoa to assay galactosyltransferase and glycosidase activities. No galactosyltransferase is present on the sperm surface, whereas two glycosidases, β-N-acetylglucosaminidase (GlcNAc′ase) and α-mannosidase (Man′ase), have been evidenced. They have an optimal pH of 6–6.5 and 4, respectively. The same glycosidases were detected as soluble forms probably secreted by the seminal vesicle epithelium. We suggest that these enzymes might be involved in the recognition of α-mannose and β-N-acetylglucosamine residues present on the egg shell at the site of sperm entry. Mol. Reprod. Dev. 48:276–281, 1997. © 1997 Wiley-Liss, Inc.     

The acentriolar state of the Drosophila cell lines 1182

A Drosophila melanogaster cell line devoid of centrioles has been recently described. In order to achieve an easier characterization of these acentriolar cells, we used the monoclonal antibody Bx 63 of M. Frasch which recognizes the Drosophila centrosome. Although centrosomes are detected at every mitotic pole in Drosophila cells with centrioles, no such structure has been observed in 1182-4 acentriolar cells. The antigenic material is, however, present in these cells. Moreover, we noticed a certain proportion of acentriolar cells in 4 other 1182 lines. The lack of centrioles previously found only in the 1182-4 cells seems therefore not accidental and should be linked to their particular origin.     

Centriole Disassembly In Vivo and Its Effect on Centrosome Structure and Function in Vertebrate Cells

Glutamylation is the major posttranslational modification of neuronal and axonemal tubulin and is restricted predominantly to centrioles in nonneuronal cells (Bobinnec, Y., M. Moudjou, J.P. Fouquet, E. Desbruyères, B. Eddé, and M. Bornens. 1998. Cell Motil. Cytoskel. 39:223–232). To investigate a possible relationship between the exceptional stability of centriole microtubules and the compartmentalization of glutamylated isoforms, we loaded HeLa cells with the monoclonal antibody GT335, which specifically reacts with polyglutamylated tubulin. The total disappearance of the centriole pair was observed after 12 h, as judged both by immunofluorescence labeling with specific antibodies and electron microscopic observation of cells after complete thick serial sectioning. Strikingly, we also observed a scattering of the pericentriolar material (PCM) within the cytoplasm and a parallel disappearance of the centrosome as a defined organelle. However, centriole disappearance was transient, as centrioles and discrete centrosomes ultimately reappeared in the cell population.During the acentriolar period, a large proportion of monopolar half-spindles or of bipolar spindles with abnormal distribution of PCM and NuMA were observed. However, as judged by a quasinormal increase in cell number, these cells likely were not blocked in mitosis.Our results suggest that a posttranslational modification of tubulin is critical for long-term stability of centriolar microtubules. They further demonstrate that in animal cells, centrioles are instrumental in organizing centrosomal components into a structurally stable organelle.     

Origin and decay of the P element-associated latitudinal cline in Australian Drosophila melanogaster

The latitudinal cline in P transposable element-associated characteristics in eastern Australian populations of Drosophila melanogaster has changed between 1986 and 1991–1994. New collections were made in 1991–1994 from localities along the eastern coast of Australia. P element-associated properties of 256 isofemale lines from 43 localities were evaluated using gonadal dysgenesis and/or singed-weak hypermutability assays. The overall results indicate that both P activity and P susceptibility have declined, with all populations showing a tendency towards a state with little P activity potential but with P repressor function (neutral or ‘Q’). P repressor function is strong in all populations except some of the most southerly. P activity potential peaks at about 27° SLat, and drops off to the south (as in 1983–1986 collections) and to the north (in contrast to 1983–1986 collections); thus the cline is no longer a simple P-to-Q-to-M pattern from north to south, but is now Q-P-Q-M. A mtDNA RFLP that putatively distinguishes North American and European populations varies in frequency among the populations but the frequency does not vary clinally with latitude, ruling out massive introductions from North America and Europe as causing the cline. This revised version was published online in July 2006 with corrections to the Cover Date.     

Origin of the multiple forms of alcohol dehydrogenase from Drosophila melanogaster.

The three forms of alcohol dehydrogenase (EC 1.1.1.1) within a given strain of Drosophila melanogaster are composed of similar, if not identical, peptide chains as shown by amino acid analysis and peptide fingerprinting. After feeding [carbonyl-¹⁴C]nicotinamide to flies, label is associated with only two of the three forms in the ratio 1:2. Similarly, a fluorescent compound is associated with the same two forms. After purification of this compound and characterization of it by thin layer chromatography and mass spectroscopy, we conclude that the multiple forms of Drosophila alcohol dehydrogenase appear to be caused by the noncovalent binding of 1 and 2 mol of an NAD-carbonyl compound addition complex to the enzyme.     

Specific Features of Centriole Formation and Ciliogenesis in Ciliary Epithelium Cells of Respiratory Tracts in Patients with Kartagener Syndrome

An electron microscopic study of the ciliary epithelium of respiratory tracts was carried out in children (members of the same family) with Kartagener syndrome, which is a variant of ciliary dyskinesia. It was shown that in the case of both mobile cilia and ciliary dyskinesia in man, centrioles are formed during formation of the ciliary basal bodies predominantly de novo, involving deuterosomes. A wide spectrum of pathological changes was described in literature, such as the absence of dynein arms in the axoneme and disorganization of axoneme structure. In addition to these changes in the ciliary system, we found integration of several ciliary axonemes by the same plasma membrane, running of microtubules from the plasma membrane as bundles, different orientation of basal legs, etc.__________Translated from Ontogenez, Vol. 36, No. 3, 2005, pp. 190–198.Original Russian Text Copyright © 2005 by Domaratskii, Uvakina, Volkov, Onishchenko.     

Functional interplay between ribosomal protein paralogues in the eRpL22 family in Drosophila melanogaster

ABSTRACT

Duplicated ribosomal protein (RP) genes in the Drosophila melanogaster eRpL22 family encode structurally-divergent and differentially-expressed rRNA-binding RPs. eRpL22 is expressed ubiquitously and eRpL22-like expression is tissue-restricted with highest levels in the adult male germline. We explored paralogue functional equivalence using the GAL4-UAS system for paralogue knockdown or overexpression and a conditional eRpL22-like knockout in a heat- shock flippase/FRT line. Ubiquitous eRpL22 knockdown with Actin-GAL4 resulted in embryonic lethality, confirming eRpL22 essentiality. eRpL22-like knockdown (60%) was insufficient to cause lethality; yet, conditional eRpL22-like knockout at one hour following egg deposition caused lethality within each developmental stage. Therefore, each paralogue is essential. Variation in timing of heat-shock-induced eRpL22-like knockout highlighted early embryogenesis as the critical period where eRpL22-like expression (not compensated for by eRpL22) is required for normal development of several organ systems, including testis development and subsequent sperm production. To determine if eRpL22-like can substitute for eRpL22, we used Actin-GAL4 for ubiquitous eRpL22 knockdown and eRpL22-like-FLAG (or FLAG-eRpL22: control) overexpression. Emergence of adults demonstrated that ubiquitous eRpL22-like-FLAG or FLAG-eRpL22 expression eliminates embryonic lethality resulting from eRpL22 depletion. Adults rescued by eRpL22-like-FLAG (but not by FLAG-eRpL22) overexpression had reduced fertility and longevity. We conclude that eRpL22 paralogue roles are not completely interchangeable and include functionally-diverse roles in development and spermatogenesis. Testis-specific paralogue knockdown revealed molecular phenotypes, including increases in eRpL22 protein and mRNA levels following eRpL22-like depletion, implicating a negative crosstalk mechanism regulating eRpL22 expression. Paralogue depletion unmasked mechanisms, yet to be defined that impact paralogue co-expression within germ cells.     

Three-Dimensional Reconstruction of the Mammalian Centriole from Cryoelectron Micrographs: The Use of Common Lines for Orientation and Alignment

The microtubule organizing center of the animal cell (S. D. Fulleret al.,1992,Curr. Opin. Struct. Biol.2,264–274; D. M. Gloveret al.,1993,Sci. Am.268,62–68; E. B. Wilson, 1925), (The Cell in Development and Heredity) comprises two centrioles and the pericentriolar material. We have completed several three-dimensional reconstructions of individual centrioles from tilt series of cryoelectron micrographs. The reconstruction procedure uses minimization of the common lines residual to define the orientation of the centriolar ninefold symmetry axis and then uses this symmetry to generate a structure by weighted backprojection to 28-nm resolution. Many of the features of these reconstructions agree with previous, conventional transmission electron microscopy studies (M. Paintrandet al.,1992,J. Struct. Biol.108,107–128). The microtubule barrel of the centriole is roughly 500 nm long and 300 nm in diameter and the microtubule bundles appear to taper toward the distal end. In addition, we see a handedness to the pericentriolar material at the base (distal end) of the centriole which is opposite to the skew of the microtubule triplets. The region at which the microtubule barrel joins this base is intriguingly complex and includes an internal cylindrical feature which is a site of γ tubulin localization.     

The first oncogene in Drosophila melanogaster

Discovered by Bridges in the 1930s, lethal (2) giant larvae was the first of more than 27 recessive oncogenes identified in Drosophila, which provides an excellent model to study neoplastic mechanisms due to the fact that homologs of human oncogenes and tumor suppressors have been isolated and most of the complexes and associated pathways are conserved. This review explores the potential of neoplastic studies in Drosophila to help understand the genomic mechanisms of neoplastic development in vertebrates and invertebrates. Starting from neoplasms and genetic mutations, the article introduces the reader to one of the possibilities that the studies on neoplastic mechanisms of oncogenes in Drosophila can provide a great understanding of the developmental progression in both vertebrates and invertebrates.     

The translation factors of Drosophila melanogaster

Synthesis of polypeptides from mRNA (translation) is a fundamental cellular process that is coordinated and catalyzed by a set of canonical ‘translation factors’. Surprisingly, the translation factors of Drosophila melanogaster have not yet been systematically identified, leading to inconsistencies in their nomenclature and shortcomings in functional (Gene Ontology, GO) annotations. Here, we describe the complete set of translation factors in D. melanogaster, applying nomenclature already in widespread use in other species, and revising their functional annotation. The collection comprises 43 initiation factors, 12 elongation factors, 3 release factors and 6 recycling factors, totaling 64 of which 55 are cytoplasmic and 9 are mitochondrial. We also provide an overview of notable findings and particular insights derived from Drosophila about these factors. This catalog, together with the incorporation of the improved nomenclature and GO annotation into FlyBase, will greatly facilitate access to information about the functional roles of these important proteins.     

The generation of cloned Drosophila melanogaster

We report here the first successful use of embryonic nuclear transfer to create viable adult Drosophila melanogaster clones. Given the generation time, cost effectiveness, and relative ease of embryonic nuclear transplant in Drosophila, this method can provide an opportunity to further study the constraints on development imposed by transplanting determined or differentiated nuclei.