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At least 757 records · Page 42Linked to original sources
PubMed2006

Quantitative genomics of aggressive behavior in Drosophila melanogaster.

Aggressive behavior is important for animal survival and reproduction, and excessive aggression is an enormous social and economic burden for human society. Although the role of biogenic amines in modulating aggressive behavior is well characterized, other genetic mechanisms affecting this complex behavior remain elusive. Here, we developed an assay to rapidly quantify aggressive behavior in Drosophila melanogaster, and generated replicate selection lines with divergent levels of aggression. The realized heritability of aggressive behavior was approximately 0.10, and the phenotypic response to selection specifically affected aggression. We used whole-genome expression analysis to identify 1,539 probe sets with different expression levels between the selection lines when pooled across replicates, at a false discovery rate of 0.001. We quantified the aggressive behavior of 19 mutations in candidate genes that were generated in a common co-isogenic background, and identified 15 novel genes affecting aggressive behavior. Expression profiling of genetically divergent lines is an effective strategy for identifying genes affecting complex traits.

Aggression↗
PubMed2006

The 'metabolon,' CD47, and the 'phagocytic synapse': molecular co-localization and species divergence.

CD47 is a widely expressed integral membrane protein, found also on red blood cells where it reportedly has a key role in inhibiting phagocytic clearance of RBC by signaling within a multi-molecular 'phagocytic synapse'. Calreticulin is postulated to be on the RBC surface and stimulate phagocytosis, whereupon CD47 on the RBC binds SIRPalpha on the phagocyte and signals a block against phagocytosis. While studies of mouse suggest such an inhibitory role for CD47, CD47 seems to have distinct interactions in human RBC--particularly within a 'metabolon' complex of CD47, Rh proteins, and several other proteins. We have assessed the relative density, co-clustering, and mobility of some of the implicated proteins on human RBC versus murine RBC (hu-RBC and mu-RBC, respectively), and we find a few major differences. While RBC from both species express similar densities of CD47 and SIRPalpha interactions are measurably modest, the interactions prove species-specific. While RBC from both species also have detectable calreticulin, fresh hu-RBC are found to have 10-100-fold more calreticulin binding sites on their surface. Imaging of clusters of SIRPalpha-CD47 on both species of RBC show that RhD does co-localize with CD47 on hu-RBC, but neither calreticulin nor Glycophorin-A appear enriched in the metabolon complexes. Furthermore, mouse-cells alone tend to aggregate due to cross-bridging by SIRPalpha complexes, showing accumulation of CD47 in the adhesion zone, which is consistent with a high mobility of CD47 unique to mu-RBC.

Animals↗
PubMed2002

Distinct physiological roles of fructokinase isozymes revealed by gene-specific suppression of Frk1 and Frk2 expression in tomato.

There are two divergent fructokinase isozymes, Frk1 and Frk2 in tomato (Lycopersicon esculentum Mill.) plants. To investigate the physiological functions of each isozyme, the expression of each fructokinase mRNA was independently suppressed in transgenic tomato plants, and the respective phenotypes were evaluated. Suppression of Frk1 expression resulted in delayed flowering at the first inflorescence. Suppression of Frk2 did not effect flowering time but resulted in growth inhibition of stems and roots, reduction of flower and fruit number, and reduction of seed number per fruit. Localization of Frk1 and Frk2 mRNA accumulation by in situ hybridization in wild-type tomato fruit tissue indicated that Frk2 is expressed specifically in early tomato seed development. Fruit hexose and starch content were not effected by the suppression of either Frk gene alone. The results collectively indicate that flowering time is specifically promoted by Frk1 and that Frk2 plays specific roles in contributing to stem and root growth and to seed development. Because Frk1 and Frk2 gene expression was suppressed individually in transgenic plants, other significant metabolic roles of fructokinases may not have been observed if Frk1 and Frk2 play, at least partially, redundant metabolic roles.

Enzyme Activation↗
PubMed1998

Expression of the Emx-1 and Dlx-1 homeobox genes define three molecularly distinct domains in the telencephalon of mouse, chick, turtle and frog embryos: implications for the evolution of telencephalic subdivisions in amniotes.

Homologies between vertebrate forebrain subdivisions are still uncertain. In particular the identification of homologs of the mammalian neocortex or the dorsal ventricular ridge (DVR) of birds and reptiles is still a matter of dispute. To get insight about the organization of the primordia of the main telencephalic subdivisions along the anteroposterior axis of the neural tube, a fate map of the dorsal prosencephalon was obtained in avian chimeras at the 8- to 9-somite stage. At this stage, the primordia of the pallium, DVR and striatum were located on the dorsal aspect of the prosencephalon and ordered caudorostrally along the longitudinal axis of the brain. Expression of homeobox-containing genes of the Emx, Dlx and Pax families were used as markers of anteroposterior developmental subdivisions of the forebrain in mouse, chick, turtle and frog. Their expression domains delineated three main telencephalic subdivisions in all species at the onset of neurogenesis: the pallial, intermediate and striatal neuroepithelial domains. The fate of the intermediate subdivisions diverged, however, between species at later stages of development. Homologies between forebrain subdivisions are proposed based on the conservation and divergence of these gene expression patterns.

Animals↗
PubMed1996

Glutamate transporter mRNA expression in proliferative zones of the developing and adult murine CNS.

Neuronal migration, differentiation, and synapse formation are developmental processes within the CNS significantly influenced by ionotropic and metabotropic glutamate receptor activity. Extracellular glutamate concentrations mediating this activity are regulated by transport proteins localized in neuronal and glial cell membranes. We have used in situ hybridization analysis with subtype-specific antisense-oligonucleotides to study the distribution of glia-specific excitatory amino acid transporter (mEAAT1 and mEAAT2) mRNAs during the later stages of embryogenesis and postnatal CNS development. Distinct but overlapping embryonic and postnatal patterns of localization were observed for the two transporter transcripts. Both mEAAT1 and mEAAT2 mRNAs were found during the peak period of gliogenesis (E15-E19) in the telencephalic and mesencephalic CNS proliferative zones. The overall expression of mEAAT1 mRNA diminished after the completion of cell migration, whereas mEAAT2 mRNA expression increased significantly during postnatal development. Interestingly, mEAAT2 transcript expression continued in the subventricular zone postnatally and persisted in this proliferative zone in the adult brain. From PO onward, mEAAT1 mRNA was present predominantly in the cerebellar Purkinje cell layer and at a much lower abundance in the cortex, hippocampus, basal nuclei, and septum, whereas from P7 onward, mEAAT2 mRNA expression increased throughout most of the neuraxis. Postnatally, transcripts for mEAAT1 and mEAAT2 were found in cell bodies, processes, and commissural white matter tracts of the CNS. The divergent temporal and spatial expression of EAAT subtypes and their persistence in mature fiber tracts and radial glia layers reveal that specific EAATs are likely to play multiple distinct roles in the developing and adult CNS, including the regulation of cell proliferation, axon-glia interactions, and neuronal survival.

ATP-Binding Cassette Transporters↗
PubMed2002

Expression of RGS2, RGS4 and RGS7 in the developing postnatal brain.

The abundant expression of RGS (regulator of G-protein signalling) proteins in neurons, together with their modulatory function on G-protein-dependent neurotransmission, provides the basis for cellular adaptation to sensory inputs. To identify the molecular mechanism involved in the sensory experience-induced neural development, we performed a systematic survey of the localization of mRNAs encoding three subtypes of the RGSs (RGS2, RGS4 and RGS7) in developing rat brains by in situ hybridization through postnatal day 2 (P2), P10 and P18 to adult. The most dramatic changes of expression patterns were observed in the discrete neuronal cell layers of the cerebral neocortex (for RGS2 and 4), the hippocampus (for RGS2, 4 and 7), the thalamus (for RGS4) and the cerebellum (for RGS2 and 7). In the neocortex, RGS2 mRNA was enriched in the superficial cortical plate at P2, in contrast to RGS4, which was enriched in more mature neurons of the deeper layer V and VI. In the hippocampus, the neuronal cell layer-specific expression pattern of RGS2 developed from P2 to P18. RGS4 expression was temporarily confined to the CA pyramidal cell layer and not detectable in the dentate gyrus at P10 and P18. Similarly, a high level of expression of RGS7 was observed in the CA area, but not in the dentate gyrus at P2 and P10. In the cerebellum, the maturation of laminar expression patterns for the three RGSs correlated with neuronal maturation and synaptogenesis at P18. The most characteristic temporal pattern among the three RGSs was observed for RGS4 mRNA, which was highly enriched in the thalamocortical regions. The peaks of RGS4 expression were seen in the following regions with distinct onset and duration: the neocortex (from P2 onward), the hippocampus (P10 and P18) and the thalamus (from P18 onward). The divergent temporal and spatial expression of RGS subtypes and their dynamic control in the cortex, the hippocampus and the thalamus suggest that the RGS family could play multiple distinct roles in experience-dependent brain development.

Aging↗
PubMed2005

Conservation and diversification of SCARECROW in maize.

The SCARECROW (SCR) gene in Arabidopsis is required for asymmetric cell divisions responsible for ground tissue formation in the root and shoot. Previously, we reported that Zea mays SCARECROW (ZmSCR) is the likely maize ortholog of SCR. Here we describe conserved and divergent aspects of ZmSCR. Its ability to complement the Arabidopsis scr mutant phenotype suggests conservation of function, yet its expression pattern during embryogenesis and in the shoot system indicates divergence. ZmSCR expression was detected early during embryogenesis and localized to the endodermal lineage in the root, showing a gradual regionalization of expression. Expression of ZmSCR appeared to be analogous to that of SCR during leaf formation. However, its absence from the maize shoot meristem and its early expression pattern during embryogenesis suggest a diversification of ZmSCR in the patterning processes in maize. To further investigate the evolutionary relationship of SCR and ZmSCR, we performed a phylogenetic analysis using Arabidopsis, rice and maize SCARECROW-LIKE genes (SCLs). We found SCL23 to be the most closely related to SCR in both eudicots and monocots, suggesting that a gene duplication resulting in SCR and SCL23 predates the divergence of dicots and monocots.

Arabidopsis↗
PubMed1995

Differential expression of the small chondroitin/dermatan sulfate proteoglycans decorin and biglycan after injury of the adult rat brain.

Chondroitin sulfate proteoglycans are widespread extracellular matrix proteins and are specifically upregulated after CNS injury at the lesion site. Many proteoglycan core proteins have been described in the rat brain, but detailed analysis of individual proteoglycans expressed after injury are missing. The present study represents an initial attempt to assess the diversity and timing of lesion-induced expression of proteoglycans in order to elucidate their functional role in CNS injury and repair. Using immunocytochemical methods we analysed the expression of decorin and biglycan in the transected postcommissural fornix of the adult rat. Transection of the fornix induced the upregulation of both decorin and biglycan. However, their expression differed with respect to time course, regional extent and cellular localization. The rapid upregulation of decorin within a wide area around the lesion was followed by a massive appearance of biglycan that remained restricted to the transection site. Three months after lesion, differences of the area size of decorin- and biglycan-immunoreactivities were no longer detectable. Both proteoglycans were restricted to the lesion site and the fornix stumps. While decorin was primarily expressed by astrocytes, biglycan was deposited extracellularly in sheet-like structures. The upregulation of both proteoglycans persisted for at least up to 6 months after lesion. These strong but divergent lesion-induced expression patterns indicate important but different roles of decorin and biglycan in CNS injury.

Animals↗
PubMed2002

Expression of zebrafish mab21 genes marks the differentiating eye, midbrain and neural tube.

Mab21 homolog in Caenorhabditis elegans is expressed in the sensory ray cells and determines the ray identity (Dev. Dyn. 221 (2001) 422). Similarly, vertebrate homologs of this gene have been shown to express in the craniofacial tissues, limb bud and neural tissues. We report here the cloning and expression analysis of two zebrafish mab21 genes. Both genes have a conserved open reading frame of 1080 nucleotides. Phylogenetic analysis suggested that the two family subgroups existed prior to the divergence of vertebrates. Their expression profiles revealed that mab21l1 was turned on in embryos as early as 8 h post-fertilization (hpf) while mab21l2 was first detected at around 11 hpf. In situ hybridization results showed that expression of these mab21 genes marked the early differentiating olfactory bulbs, eye primordia, midbrain and subsequently the branchial pouches and neural tube.

Animals↗
PubMed2006

Survivin stable knockdown by siRNA inhibits tumor cell growth and angiogenesis in breast and cervical cancers.

Increased resistance to apoptosis is a hallmark of many tumor cells. Survivin, a member of IAP family protein, is expressed in many human cancers and plays an important role in protecting cells from apoptosis. Here we show that vector-based small interfering RNAs (siRNA) stably knockdown survivin expression in several cancer cell lines, leading to increased apoptotic rate in response to different proapoptotic stimuli, such as doxorubicin or TNF-alpha. The apoptotic susceptibility was dependent on divergent levels of survivin expression. The stable transfectants exhibited abnormal morphology, suppressed cell growth, enhanced spontaneous apoptosis and cell cycle hindrance. Furthermore, in nude mice xenografts of survivin-positive tumors, cells expressing survivin-targeted siRNAs exhibited decreased tumor formation and reduced angiogenesis. Results from these studies: (1) provide direct evidence that intracellular silencing of survivin by siRNA sensitizes human tumor cells to apoptosis; (2) define survivin as a promising molecular target for cancer therapy; and (3) suggest the potential applicability of survivin-targeted siRNA for treating human tumors, probably in combination with chemotherapy.

Animals↗
PubMed1998

Of mites and zen: expression studies in a chelicerate arthropod confirm zen is a divergent Hox gene.

We have cloned, from an oribatid mite, a gene homologous to the zerknült (zen) genes of insects and the Hox 3 genes of vertebrates. Hox genes specify cell fates in specific regions of the body in all metazoans studied and are expressed in antero-posteriorly restricted regions of the embryo. This is true of the vertebrate Hox 3 but not of the zen genes, the insect homologs, and it has been proposed that the zen genes have lost their Hox-like function in the ancestor of the insects. We studied expression of a mite Hox 3/zen homolog and found that it is expressed in a discrete antero-posterior region of the body with an anterior boundary coinciding with that of the chelicerate homolog of the Drosophila Hox gene, proboscipedia, and propose that its loss of Hox function in insects is due to functional redundancy due to this overlap with another Hox gene.

Amino Acid Sequence↗
PubMed2006

Divergence of duplicated genes in maize: evolution of contrasting targeting information for enzymes in the porphyrin pathway.

The divergence of sequence and expression pattern of duplicated genes provides a means for genetic innovation to occur without sacrificing an essential function. The cpx1 and cpx2 genes of maize are a singular example of duplicated genes that have diverged by deletion and creation of protein targeting information. The cpx genes encode coproporphyrinogen III oxidase ('coprogen oxidase'), which catalyzes a step in the synthesis of chlorophyll and heme. In plants, this enzyme has been found exclusively in the plastids. The cpx1 and cpx2 genes encode almost identical, catalytically active enzymes with distinctive N-terminal peptide sequences. The cpx1 gene encodes the expected plastid transit peptide, but this region is deleted from the cpx2 gene. While the 5' regions of both messenger RNAs are highly similar, the cpx2 gene has an open-reading frame that could encode a new targeting signal. GFP fused with CPX1 localized to the plastids. In contrast, the GFP fusion with CPX2 did not target plastids and appeared to localize to mitochondria. Both cpx genes are expressed ubiquitously but, based on mutant phenotype, they seem to have discrete biological roles. Seedlings homozygous for a null mutation in the cpx1 gene completely lack chlorophyll and develop necrotic lesions in the light. However, the mutant seedlings and callus cultures will grow in tissue culture in the dark, implying that they retain a capacity to produce heme. We discuss models for the evolution of the cpx genes and possible roles of mitochondrion-localized coprogen oxidase activity in maize.

Amino Acid Sequence↗
PubMed2001

Global and cognate regulators control the expression of the organic solvent efflux pumps TtgABC and TtgDEF of Pseudomonas putida.

Pseudomonas putida DOT-T1E grows on a water-toluene double liquid phase. Toluene tolerance in this microorganism is mainly achieved by at least two efflux pumps that belong to the RND family. The TtgDEF efflux pump is induced by toluene, whereas the other efflux pump, called TtgABC, is expressed at a high level in cells not exposed to toluene and at a lower level in cells grown with toluene. The ttgR gene is adjacent to the ttgABC operon and is transcribed divergently from ttgA. The expression level of ttgR was fourfold higher in cells growing in the presence of toluene than in its absence. In a TtgR-deficient background, expression from the ttgA promoter increased about 20-fold, suggesting that TtgR represses expression from the ttgA promoter. In this mutant, background expression of the ttgR gene was also much higher than in the wild-type background; however, its level of expression increased in the presence of toluene. In a ttgR mutant background, expression from the ttgD promoter followed the same pattern of expression as in the wild type. Analysis of a P. putida pTn5cat mutant that exhibited increased sensitivity to a sudden toluene shock, regardless of whether or not it was previously exposed to low toluene concentrations, revealed that pTn5cat had interrupted an lrp-like gene. The ttgR gene was expressed at very high levels in this mutant, with concomitant repression of expression of the ttgABC operon. The second ttgDEF efflux pump was expressed at low levels in this mutant strain, suggesting that the Lrp-like protein is a global regulatory protein involved in the solvent-tolerant response of this strain.

Bacterial Proteins↗
PubMed1998

Tandem zinc-finger gene families in mammals: insights and unanswered questions.

Evidence for the remarkable conservation of mammalian genomes, in both content and organization of resident genes, is rapidly emerging from comparative mapping studies. The frequent occurrence of familial gene clustering, presumably reflecting a history of tandem in situ duplications starting from a single ancestral gene, is also apparent from these analyses. Genes encoding Kruppel-type zinc-finger (ZNF) proteins, including those containing Kruppel-associated box (KRAB) motifs, are particularly prone to such clustered organization. Existing data suggest that genes in KRAB-ZNF gene clusters have diverged in sequence and expression patterns, possibly yielding families of proteins with distinct, yet related, functions. Comparative mapping studies indicate that at least some of the genes within these clusters in mammals were elaborated prior to the divergence of mammalian orders and, subsequently, have been conserved. These data suggest a possible role for these tandem KRAB-ZNF gene families in mammalian evolution.

Amino Acid Sequence↗
PubMed1993

Distinct mechanisms regulate interstitial collagenase and 92-kDa gelatinase expression in human monocytic-like cells exposed to bacterial endotoxin.

We studied the mechanisms that govern the expression of interstitial collagenase and 92-kDa gelatinase in U937 cells, a human monocyte-like cell line, exposed to bacterial lipopolysaccharide (LPS), a potent inducer of metalloproteinase expression. U937 cells were differentiated by phorbol ester (phorbol 12-myristate 13-acetate (PMA)) and, 24 h later, were exposed to LPS for an additional 24 h. Enzyme-linked immunosorbent assay and Northern hybridization showed that PMA mediated an induction of collagenase and markedly stimulated the low basal levels of 92-kDa gelatinase. Subsequent exposure to LPS substantially increased the production of both enzymes. Nuclear runoff assay demonstrated that PMA regulated collagenase and 92-kDa gelatinase transcription. LPS also stimulated collagenase transcription but did not affect transcription of 92-kDa gelatinase. Consistent with the runoff data, the decay rate of collagenase mRNA did not differ between experimental treatments, but the half-life of gelatinase mRNA increased with exposure to LPS. Furthermore, in situ hybridization showed that 92-kDa gelatinase was expressed by all cells whereas collagenase was produced by a subpopulation of cells in both PMA- and PMA/LPS-exposed cultures, and similar findings were seen with LPS-activated human alveolar macrophages. These data indicate that divergent mechanisms control metalloproteinase expression in phagocytic cells and that enzyme production differs among macrophage subpopulations.

Adult↗
PubMed1991

Transgene expression variability (position effect) of CAT and GUS reporter genes driven by linked divergent T-DNA promoters.

Forty-five individually transformed clonal tobacco callus lines were simultaneously assayed for both chloramphenicol acetyltransferase (CAT) and beta-glucuronidase (GUS) activity resulting from expression of introduced reporter genes driven by the adjacent and divergent mannopine (mas) promoters. Excluding lines in which one or both of the enzyme activities was essentially zero, the activities of the reporter genes varied by as much as a factor of 136 (CAT) and 175 (GUS) between individual transformants. Superimposed upon the high degree of inter-clonal expression variability was an intra-clonal variability of 3-4-fold. The observed degree of intra-clonal reporter gene activity may be more extreme because of the regulatory characteristics of the mannopine promoters, but must still be addressed when considering the limitations of reporter gene-based analysis of transgene function and structure. There was no consistent correlation between the expression levels of the introduced CAT and GUS genes since the ratio of GUS to CAT activities (nmol min-1 mg-1) within individual lines varied from 0.05 to 49. Even divergent transcription from two directly adjacent promoter regions (both contained within a 479 bp TR-DNA fragment) is insufficient to guarantee concurrent expression of two linked transgenes. Our quantitative data were compared to published data of transgene expression variability to examine the overall distribution of expression levels in individual transformants. The resulting frequency distribution indicates that most transformants express introduced transgenes at relatively low levels, suggesting that a potentially large number of Agrobacterium-mediated transformation events may result in silent transgenes.

Chloramphenicol O-Acetyltransferase↗
PubMed2006

Prolactin in man: a tale of two promoters.

The pituitary hormone prolactin (PRL) is best known for its role in the regulation of lactation. Recent evidence furthermore indicates PRL is required for normal reproduction in rodents. Here, we report on the insertion of two transposon-like DNA sequences in the human prolactin gene, which together function as an alternative promoter directing extrapituitary PRL expression. Indeed, the transposable elements contain transcription factor binding sites that have been shown to mediate PRL transcription in human uterine decidualised endometrial cells and lymphocytes. We hypothesize that the transposon insertion event has resulted in divergent (pituitary versus extrapituitary) expression of prolactin in primates, and in differential actions of pituitary versus extrapituitary prolactin in lactation versus pregnancy respectively. Importantly, the TE insertion might provide a context for some of the conflicting results obtained in studies of PRL function in mice and man.

Animals↗
PubMed1992

Divergent ileal IGF-I and IGFBP-3 gene expression after small bowel resection: a novel mechanism to amplify IGF action?

Changes in the levels of ileal insulin-like growth factor-I (IGF-I) and insulin-like growth factor binding protein-3 (IGFBP-3) mRNA in the rat following massive small bowel resection (MSBR) have been investigated with a sensitive S1 nuclease assay. IGF-I mRNA levels vary little over 7 days; in contrast IGFBP-3 mRNA levels decreased to one-third 7 h post-MSBR, and remained suppressed for the length of this study. We postulate that decreased ileal synthesis of IGFBP-3 enhances the ability of IGF-I to stimulate the adaptive response.

Animals↗