Esperanto for histones: CENP-A, not CenH3, is the centromeric histone H3 variant.

The first centromeric protein identified in any species was CENP-A, a divergent member of the histone H3 family that was recognised by autoantibodies from patients with scleroderma-spectrum disease. It has recently been suggested to rename this protein CenH3. Here, we argue that the original name should be maintained both because it is the basis of a long established nomenclature for centromere proteins and because it avoids confusion due to the presence of canonical histone H3 at centromeres.

Reducing stigma and discrimination associated with COVID-19: early stage pandemic rapid review and practical recommendations.

AIMS: To develop recommendations for strategies and interventions to reduce stigma and discrimination related to coronavirus disease 2019 (COVID-19), through reviewing and synthesising evidence in relation to COVID-19 and other disease outbreaks and infectious/stigmatised conditions from systematic reviews and primary studies and recommendations from additional materials. METHODS: Rapid review, drawing on the World Health Organization's (WHO) methodology for developing interim guidelines during health emergencies. PubMed/MEDLINE, PsycINFO, Cochrane Central and Campbell Collaboration searched up to mid-April 2020. Searches were supplemented by reference-searching and expert recommendations. Searches were designed to identify: (1) systematic reviews (<10 years), or (2) primary intervention studies (no date limit) reporting evidence on anti-stigma interventions (in relation to COVID-19 or other infectious/stigmatised conditions) or (3) additional relevant materials. Data were extracted on population, intervention, outcome and results. These data were compiled into evidence summary tables and narrative overviews. Recommendations on strategies for COVID-19 stigma-reduction were developed using the WHO 'Evidence to Decision' framework approach. The review protocol was registered with PROSPERO (registration ID: CRD42020177677). RESULTS: The searches identified a total of 4150 potentially relevant records, from which 12 systematic reviews and 29 additional articles were included. Overarching considerations and specific recommendations focus on: (1) language/words used in relation to COVID-19 and affected people; (2) media/journalistic practices; (3) public health interventions; (4) targeted public health interventions for key groups and (5) involving communities and key stakeholders. CONCLUSIONS: These recommendations represent the first consolidated evidence-based guidance on stigma and discrimination reduction in relation to COVID-19. Mitigating the impact of stigma is critical in reducing distress and negative experiences, and strengthening communities' resolve to work together during exceptional circumstances. Ultimately, reducing stigma helps addressing structural inequalities that drive marginalisation and exacerbate both health risks and the impact of stigma. Administrations and decision makers are urged to consider integrating these recommendations into the ongoing COVID-19 response.

Isolation of chromosome-associated proteins from Drosophila melanogaster that bind a human centromeric DNA sequence.

The molecular mechanism involved in packaging centromeric heterochromatin is still poorly understood. CENP-B, a centromeric protein present in human cells, is though to be involved in this process. This is a DNA-binding protein that localizes to the central domain of the centromere of human and mouse chromosomes due to its association with the 17-bp CENP-B box sequence. We have designed a biochemical approach to search for functional homologues of CENP-B in Drosophila melanogaster. This strategy relies upon the use of DNA fragments containing the CENP-B box to identify proteins that specifically bind this sequence. Three polypeptides were isolated by nuclear protein extraction, followed by sequential ion exchange columns and DNA affinity chromatography. All three proteins are present in the complex formed after gel retardation with the human alphoid satellite DNA that contains the CENP-B box. Footprinting analysis reveals that the complex occupies both strands of the CENP-B box, although it is still unclear which of the polypeptides actually makes contact with the DNA. Localization of fluorescein-labeled proteins after microinjection into early Drosophila embryos shows that they associate with condensed chromosomes. Immunostaining of embryos with a polyclonal serum made against all three polypeptides also shows chromosomal localization throughout mitosis. During metaphase and anaphase the antigens appear to localize preferentially to centromeric heterochromatin. Immunostaining of neuroblasts chromosome spreads confirmed these results, though some staining of chromosomal arms is also observed. The data strongly suggests that the polypeptides we have identified are chromosomal binding proteins that accumulate mainly at the centromeric heterochromatin. Furthermore, DNA binding assays clearly indicate that they have a high specific affinity for the human CENP-B box. This would suggest that at least one of the three proteins isolated might be a functional homologue of the human CENP-B.

Human autoantibodies reveal titin as a chromosomal protein.

Assembly of the higher-order structure of mitotic chromosomes is a prerequisite for proper chromosome condensation, segregation and integrity. Understanding the details of this process has been limited because very few proteins involved in the assembly of chromosome structure have been discovered. Using a human autoimmune scleroderma serum that identifies a chromosomal protein in human cells and Drosophila embryos, we cloned the corresponding Drosophila gene that encodes the homologue of vertebrate titin based on protein size, sequence similarity, developmental expression and subcellular localization. Titin is a giant sarcomeric protein responsible for the elasticity of striated muscle that may also function as a molecular scaffold for myofibrillar assembly. Molecular analysis and immunostaining with antibodies to multiple titin epitopes indicates that the chromosomal and muscle forms of titin may vary in their NH2 termini. The identification of titin as a chromosomal component provides a molecular basis for chromosome structure and elasticity.

Mutations in the essential spindle checkpoint gene bub1 cause chromosome missegregation and fail to block apoptosis in Drosophila.

We have characterized the Drosophila mitotic checkpoint control protein Bub1 and obtained mutations in the bub1 gene. Drosophila Bub1 localizes strongly to the centromere/kinetochore of mitotic and meiotic chromosomes that have not yet reached the metaphase plate. Animals homozygous for P-element-induced, near-null mutations of bub1 die during late larval/pupal stages due to severe mitotic abnormalities indicative of a bypass of checkpoint function. These abnormalities include accelerated exit from metaphase and chromosome missegregation and fragmentation. Chromosome fragmentation possibly leads to the significantly elevated levels of apoptosis seen in mutants. We have also investigated the relationship between Bub1 and other kinetochore components. We show that Bub1 kinase activity is not required for phosphorylation of 3F3/2 epitopes at prophase/prometaphase, but is needed for 3F3/2 dephosphorylation at metaphase. Neither 3F3/2 dephosphorylation nor loss of Bub1 from the kinetochore is a prerequisite for anaphase entry. Bub1's localization to the kinetochore does not depend on the products of the genes zw10, rod, polo, or fizzy, indicating that the kinetochore is constructed from several independent subassemblies.

The elusive centromere: sequence divergence and functional conservation.

The centromere is an essential cis-acting structure present in the chromosomes of all eukaryotes, central to the mechanism that ensures proper segregation during meiosis and mitosis. Molecular characterization of centromeres in the budding and fission yeasts has advanced significantly over the last few years due to their relatively small size and the availability of functional assays. However, identification and characterization of centromeric sequences from multicellular organisms has proven to be slow and difficult in the absence of direct functional tests. Molecular data have recently become available on the centromere of Drosophila, making it possible to bridge a long-standing gap in our knowledge on the general structure of centromeres. An evaluation of the available data from yeast to man suggests that centromere sequence and centromere sequence organization have diverged significantly, even amongst different chromosomes of a single organism; however, overall centromere organization and kinetochore components might be significantly more conserved than thought previously.

Organized microtubule arrays in gamma-tubulin-depleted Drosophila spermatocytes.

To assess the role of gamma-tubulin in spindle assembly in vivo, we have followed meiosis progression by immunofluorescence and time-lapse video microscopy in gammaTub23C(PI) mutant spermatocytes. We have found that centrosomes associate with large numbers of astral microtubules even though gamma-tubulin is severely depleted; bipolar meiotic spindles are never assembled; and later in meiosis, the microtubules get organized into a conical structure that is never observed in wild-type cells. Several lines of evidence suggest that these cones may be related to wild-type central spindles. First, they are assembled midway through meiosis and elongate during anaphase. Second, they are constricted during late meiosis, giving rise to a pointed end similar to those that form in each half of the wild-type spindle midzone. Third, Klp3A and Polo, two markers of the wild-type central spindle are also found around the pointed end of the mutant cones. Finally, ectopic cytokinesis furrows are often formed at the distal end of the cone. Our results suggest that microtubule polymerization or stabilization from the centrosome may be possible in a gamma-tubulin-independent manner in Drosophila spermatocytes. However, gamma-tubulin seems to be essential for spindle assembly in these cells. Finally, our results show that at least part of the central spindle and constriction-ring assembly machinery can operate on microtubule bundles that are not organized as bipolar spindles.

The Drosophila RAD21 cohesin persists at the centromere region in mitosis.

'Cohesin' is a highly conserved multiprotein complex thought to be the primary effector of sister-chromatid cohesion in all eukaryotes. Cohesin complexes in budding yeast hold sister chromatids together from S phase until anaphase, but in metazoans, cohesin proteins dissociate from chromosomes and redistribute into the whole cell volume during prophase, well before sister chromatids separate (reviewed in [1,2]). Here we address this apparent anomaly by investigating the cell-cycle dynamics of DRAD21, the Drosophila orthologue of the Xenopus XRAD21 and Saccharomyces cerevisiae Scc1p/Mcd1p cohesins [3]. Analysis of DRAD21 in S2 Drosophila tissue culture cells and live embryos expressing a DRAD21-green fluorescent protein (GFP) fusion revealed the presence of four distinct subcellular pools of DRAD21: a cytoplasmic pool; a chromosome-associated pool which dissociates from chromatin as chromosomes condense in prophase; a short-lived centrosome-associated pool present during metaphase-anaphase; and a centromere-proximal pool which remains bound to condensed chromosomes, is found along the junction of sister chromatids between kinetochores, and persists until the metaphase-anaphase transition. We conclude that in Drosophila, and possibly all metazoans, a minor pool of cohesin remains bound to centromere-proximal chromatin after prophase and maintains sister-chromatid cohesion until the metaphase-anaphase transition.

A role for Drosophila SMC4 in the resolution of sister chromatids in mitosis.

BACKGROUND: Faithful segregation of the genome during mitosis requires interphase chromatin to be condensed into well-defined chromosomes. Chromosome condensation involves a multiprotein complex known as condensin that associates with chromatin early in prophase. Until now, genetic analysis of SMC subunits of the condensin complex in higher eukaryotic cells has not been performed, and consequently the detailed contribution of different subunits to the formation of mitotic chromosome morphology is poorly understood. RESULTS: We show that the SMC4 subunit of condensin is encoded by the essential gluon locus in Drosophila. DmSMC4 contains all the conserved domains present in other members of the structural-maintenance-of-chromosomes protein family. DmSMC4 is both nuclear and cytoplasmic during interphase, concentrates on chromatin during prophase, and localizes to the axial chromosome core at metaphase and anaphase. During decondensation in telophase, most of the DmSMC4 leaves the chromosomes. An examination of gluon mutations indicates that SMC4 is required for chromosome condensation and segregation during different developmental stages. A detailed analysis of mitotic chromosome structure in mutant cells indicates that although the longitudinal axis can be shortened normally, sister chromatid resolution is strikingly disrupted. This phenotype then leads to severe chromosome segregation defects, chromosome breakage, and apoptosis. CONCLUSIONS: Our results demonstrate that SMC4 is critically important for the resolution of sister chromatids during mitosis prior to anaphase onset.

Sequence conservation around the 5' ends of the larval serum protein 1 genes of Drosophila melanogaster.

We have determined the nucleotide sequence at the 5' ends of the genes for the alpha, beta and gamma polypeptides of larval serum protein 1 (LSP1) of Drosophila melanogaster. In their upstream regions, the three genes share homology around the TATA boxes. There is also a homologous region of about 20 nucleotides at positions 200, 216 and 377 upstream from the alpha, beta and gamma genes, respectively. Another 18-nucleotide homology occurs between a sequence 111 nucleotides upstream from the alpha gene and 130 nucleotides upstream of the beta gene. This contains a seven-nucleotide match with a sequence 180 nucleotides upstream from the gamma gene. The sequences corresponding to the 5' non-translated regions of the RNA show two regions of strong homology: one being within the first 20 nucleotides at the very 5' end of the RNA, and the other being between nucleotides 27 and 52 of the three transcripts. The first AUG codon to precede a long open reading frame is found at nucleotides 89, 86 and 83 downstream from the 5' end of the alpha, beta and gamma RNAs, respectively. An extremely conserved nucleotide sequence with an exact homology of 66 nucleotides between the alpha and beta genes, and sharing 27 nucleotides with the gamma gene, is contained within this long open reading frame in the first exon. Conceptual translation of the long open reading frame shows that the hydrophobic nature of the first 20 amino acids of the three polypeptides has been conserved whereas the exact sequence has not. This suggests that the N termini contain signal sequences required for secretion of the protein into the haemolymph. The three genes have intervening sequences ranging from 65 to 68 nucleotides in length at comparable locations close to the 5' end of the genes.

Expression of the prokaryotic gene for chloramphenicol acetyl transferase in Drosophila under the control of larval serum protein 1 gene promoters.

We have linked the protein coding region of the prokaryotic gene for chloramphenicol acetyl transferase (CAT) to the promoter region of the Drosophila genes for larval serum protein 1 (LSP1). These regions consist of 1.65 X 10(3) and 2.25 X 10(3) base long DNA segments upstream from the LSP1 alpha and beta genes, respectively. The hybrid genes have been inserted into a P-element transformation vector and the constructs introduced into cultured Drosophila Kc cells by calcium phosphate-mediated transfection, or into the germ-lines of flies by P-element-mediated transformation. CAT expression occurs in approximately 1% of the cultured cells following transfection and the accumulation of protein is maximal three to four days after transfection; and it is dependent upon the presence of the LSP1 sequences. We have also obtained several lines of transformed flies that carry the LSP1-CAT genes in their germ-line. The onset of synthesis of functional chloramphenicol acetyl transferase in these organisms occurs in the late third larval instar, rising to a maximum at puparium formation. We continue to detect CAT until the first few hours of adulthood. Assays of CAT activity in the homogenates of dissected tissues indicated that the genes are only expressed in the fat body, as are the endogenous LSP1 genes. We have confirmed this tissue-specific localization of CAT in indirect immunofluorescence using an anti-CAT monoclonal antibody. Northern blots indicate that CAT transcripts are found only in the fat body but their abundance is an order of magnitude lower than endogenous LSP1 transcripts. Primer extension experiments show that transcription of the hybrid genes is initiated at the same nucleotide as the endogenous LSP1 genes. Taken together these data indicate that the 1.65 X 10(3) and 2.25 X 10(3) base segments of DNA upstream from the LSP1 alpha and LSP1 beta genes contain cis-acting regulatory elements necessary for correct tissue and temporal specificity of LSP1 gene expression.

Microtubule binding of the drosophila DMAP-85 protein is regulated by phosphorylation in vitro.

The phosphorylation of microtubule-associated proteins (MAPs) is thought to be a key factor in the regulation of microtubule (MT) stability. Previously we isolated DMAP-85, a Drosophila MAP shown to be associated with stable MTs. In this work we show that DMAP-85 phosphorylated in cell-free early embryo extracts is released from MTs. MPM-2 antibodies recognize the phosphorylated protein. In vitro, DMAP-85 can be phosphorylated by the mitotic kinase Polo affecting its binding to MTs and creating MPM-2 epitopes on the protein. The results suggest that phosphorylation of DMAP-85 might affect its MT stabilizing activity during early mitotic cycles.

Synthesis, platelet aggregation inhibitory activity, and in vivo antithrombotic activity of new 1,4-dihydropyridines.

A series of 1,4-dihydropyridines (DHP) bound to 1,2-benzisothiazol-3-ones were synthesized and evaluated for their ability to inhibit platelet aggregation induced by collagen in human platelet-rich plasma (PRP) and to protect mice against experimental thrombosis. The results showed that the compounds were in vitro inhibitors of collagen-induced platelet aggregation. Most of them were also effective in reducing mortality in the mouse antithrombotic assay. 2-(1,1,3-Trioxo-2,3-dihydro-1,2-benzisothiazol-2-yl)ethyl 2,6-dimethyl-5-(ethoxycarbonyl)-4-methyl-1,4-dihydropyridinecarboxyla te (4A) is the most promising compound. This compound did not show any cardiovascular effects either in the anesthetized cat or in the anesthetized rat at iv doses up to 750 or 500 micrograms/kg, respectively. Likewise, antiplatelet and cardiovascular effects of compound 4A were simultaneously studied in anesthetized rats and compared with those of nitrendipine.

4-Alkyl-1,4-dihydropyridines derivatives as specific PAF-acether antagonists.

A new series of 4-alkyl-1,4-dihydropyridines (1,4-DHP) were synthesized and evaluated for their ability to inhibit washed rabbit platelet aggregation induced by PAF-acether (1-O-hexadecyl/octadecyl-2-O-acetyl-sn-glycero-3-phosphorylcholine) and to reverse PAF-induced hypotension in anesthetized rats. Additionally, compounds were evaluated for their ability to inhibit the binding of radiolabeled PAF to its receptor on rabbit platelets. Among these compounds, 6I and 6L were the most potent and specific antagonists. At concentrations up to 100 microM, neither compound 6I nor compound 6L caused platelet aggregation nor did they inhibit platelet aggregation induced by collagen or adenosine diphosphate. Compound 6L did not show in vitro calcium channel blocker activity measured on vascular smooth muscle preparations of rabbit aorta and on [3H]nitrendipine binding assays. The compound did not show any cardiovascular effects in anesthetized rat at iv doses up to 1000 micrograms/kg, and the Ki value was 568.62 nmol. These results indicate that compound 6L is a potent and specific PAF antagonist with 1,4-dihydropyridine structure but devoid of a significant cardiovascular activity related to calcium-antagonist properties.

Synthesis, structure, and pharmacological evaluation of the stereoisomers of furnidipine.

The synthesis and pharmacological activities of the four stereoisomers of methyl tetrahydrofuran-2-ylmethyl 2,6-dimethyl-4-(2'-nitrophenyl)-1,4-dihydropyridine-3,5- dicarboxylate(furnidipine) are reported. The four isomers were synthesized by a modified Hantzsch synthesis by reaction of (-)- or (+)-tetrahydrofuran-2-ylmethyl 3-aminocrotonate and methyl 2-[(2'-nitrophenyl)methylene]acetoacetate or, alternatively, by reaction of (-)- or (+)-tetrahydrofuran-2-ylmethyl 2-[(2'-nitrophenyl)methylene]acetoacetate and methyl 3-aminocrotonate. The 1:1 diastereomeric mixtures thus obtained were separated by chromatography, using poly(D-phenylglycine) as the chiral stationary phase. The enantiomeric purity of the stereoisomers was determined by a high-performance liquid chromatography-chiral stationary phase technique (HPLC-CSP). Attempts to obtain crystals of a single stereoisomer failed in different solvents, while methanol crystallization of the product obtained from (+/-)-tetrahydrofuran-2-ylmethyl 2-[(2'-nitrophenyl)methylene]acetoacetate and methyl 3-aminocrotonate yielded good-quality crystals of the most insoluble racemate which proved to be a mixture of the (SS)/(RR) enantiomers by X-ray crystallography. Conformational analysis of the stereoisomers, assuming rotation of the aryl substituent and ester groups, shows small energy differences (about 4 kcal.mol-1) between the most and the least favorable conformations. Binding studies were performed using [3H]isradipine as a reference ligand. The results showed stereospecificity of the furnidipine isomers in brain, ileum, and cardiac tissues, the (SS)- and (SR)-isomers clearly being more potent than their (RR)- and (RS)-enantiomers. The (SS)- and (SR)-isomers were also more selective on cerebral tissue when compared with ileal and cardiac preparations.

Synthesis of 3-[(2,3-dihydro-1,1,3-trioxo-1,2-benzisothiazol-2-yl)alkyl] 1,4-dihydropyridine-3,5-dicarboxylate derivatives as calcium channel modulators.

1,4-Dihydropyridine (DHP) derivatives with a 1,2-benzisothiazol-3-one 1,1-dioxide group, linked through an alkylene bridge to the C-3 carboxylate of the DHP ring, with both vasoconstricting and vasorelaxant properties were obtained. In blocking Ca(2+)-evoked contractions of K(+)-depolarized rabbit aortic strips, compounds 12 and 41 were 10-fold more potent than nifedipine; 27 other compounds were 1-4-fold more potent. Their vascular versus cardiac selectivity was very pronounced; for instance, the selectivity index for compound 41 was 70-fold higher than that of nifedipine. This was also true for the vasoconstricting compound 22, which was as potent as Bay K 8644 in enhancing the Ca(2+)-evoked contractions of rabbit aorta strips, yet it had poor inotropic activity in rabbit left atria. Oral administration of compounds 38, 40, 43, and 53 (20 mg/kg) caused a 35-37% decrease in systolic blood pressure in spontaneously hypertensive rats (SHR); these effects were similar to those of nifedipine. However, iv administration of these compounds to anesthetized SHR caused a decrease in blood pressure which was more pronounced and long-lasting than that of nifedipine. When administered iv at 100 micrograms/kg, the vasoconstricting compound 22 caused a 40% increase in systolic and diastolic blood pressure. Compound 22 exhibited an unusually interesting feature over the other five Ca2+ DHP agonists: it had diester substitutions at the C-3 and C-5 positions of the DHP ring. Overall, compounds possessing these properties might be useful in treating clinical cardiovascular conditions in which DHP Ca2+ antagonists or agonists are indicated.

The antithrombogenic in vivo effects of calcium channel blockers in experimental thrombosis in mice.

A new model of thrombotic challenge, well suited for screening agents and which acts primarily against platelet thromboembolism, has been used to test the in vivo anti-platelet effects of four calcium channel blockers (CCB). An i.v. injection of a mixture of collagen plus epinephrine (15 micrograms and 1.8 micrograms/mouse, respectively) was given to male mice. 94% control mice died or remained paralyzed for more than 15 minutes. The dihydropyridine agents, CRE-223 and Nifedipine, were highly protective against experimental thrombosis, whereas Verapamil had a weaker and much shorter effect and, on the other hand, Diltiazem had no protective effect over a range of doses. The activity on both dihydropyridines lasted for seven hours or even longer.

Antiproliferative effects of PCA-4230, a new antithrombotic drug, in vascular smooth muscle cells.

1. In the present study we examined the effects of PCA-4230, a novel antithrombotic agent, on the growth of cultured A10 vascular smooth muscle cells (rat'aorta). 2. The action of PCA-4230 on cell proliferation and on serum-induced DNA synthesis was determined by measuring the cell number and the incorporation of the thymidine analogue 5-bromo-2'-deoxyuridine (BrdU), respectively. 3. PCA-4230 reversibly inhibited vascular smooth muscle cell proliferation. The increase in cell number was significantly reduced in the presence of 1 and 50 microM PCA-4230. 4. DNA synthesis was concentration-dependently inhibited by PCA-4230 (0.5 to 50 microM) in A10 cells that were synchronized by 48 h serum starvation and then re-stimulated by serum repletion, with an IC50 value of 13 microM. However, serum-induced DNA synthesis in bovine aortic endothelial cells was not significantly affected by PCA-4230. In addition, PCA-4230 (50 microM) caused a significant drop in PDGF-BB-mediated BrdU incorporation in A10 cells. 5. The effect of PCA-4230 on serum-induced DNA synthesis was compared to that elicited by nifedipine, another dihydropyridine-class inhibitor of vascular smooth muscle proliferation. PCA-4230 (10 microM) elicited a degree of inhibition similar to that of nifedipine at equimolar concentration. 6. To define the nature of the cell proliferation inhibition, an evaluation of cell cycle progression was undertaken. Flow cytometry studies of DNA content in synchronized cells revealed a block of the serum-inducible cell cycle progression. This inhibitory effect was markedly reduced when PCA-4230 was added 2 h after serum repletion. 7. Accordingly, PCA-4230 (50 microM) caused a 95 and 90% decrease in the elevation of c-fos and c-jun proto-oncogenes expression as evaluated by Northern blot analysis of mRNA induced early after serum addition. 8. The present results indicate that PCA-4230 inhibits vascular smooth muscle cell proliferation, in culture, by altering the cell cycle progression. Flow cytometric studies of DNA content and the down regulation of c-fos and c-jun proto-oncogenes, suggest that the drug is acting at the early G0/G1 transition phase. PCA-4230 may hold promising potential for the prevention of structural abnormalities of blood vessels associated with atherosclerosis and vascular diseases.

Molecular cloning, developmental expression, and cellular localization of the 70-kDa RPA-1 subunit of Drosophila melanogaster.

Replication protein A (RPA) is a highly conserved multifunctional heterotrimeric complex, involved in DNA replication, repair, recombination, and possibly transcription. Here, we report the cloning of the gene that codes for the largest subunit of the Drosophila melanogaster RPA homolog, dmRPA70. In situ hybridization showed that dmRPA70 RNA is present in developing embryos during the first 16 cycles. After this point, dm-RPA70 expression is downregulated in cells that enter a G1 phase and exit the mitotic cycle, becoming restricted to brief bursts of accumulation from late G1 to S phase. This pattern of regulated expression is also observed in the developing eye imaginal disc. In addition, we have shown that the presence of cyclin E is necessary and sufficient to drive the expression of dmRPA70 in embryonic cells arrested in G1 but is not required in tissues undergoing endoreduplication. Immunolocalization showed that in early developing embryos, the dmRPA70 protein associates with chromatin from the end of mitosis until the beginning of the next prophase in a dynamic speckled pattern that is strongly suggestive of its association with replication foci.

The sensory projections of Drosophila mutants which show abnormal wing formation or flying behavior.

The central projection pattern of sensory neurones from the wing of Drosophila melanogaster arise from a small number of differentiated cell types which are localized in a precise and reproducible spatial pattern. We report here the distribution of the nerve pathways revealed by filling with peroxidase and the structure and number of the wing sensory receptors, in flies which have wings but which nevertheless are flightless, including one which presents abnormal wing formation. Our results indicate that in dumpy and taxi mutants, there are no detectable modifications in the neural projections or in the number and morphology of sensory receptors. Vestigial mutants however, present several alterations including the absence of the ovoid projection, a fact consistent with the existence of very few marginal bristles. The projection of the large companiform sensilla branch profusely along the ventromedial tract and more sensory fibers cross the midline in the mesothorax. Wings of vestigial mutants show a decrease in the number of large campaniform sensilla, and more importantly some receptors present abnormally oriented trichomes in the neighboring cells.