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The Journal of Comparative Neurology Feb 2021We present here a thorough and complete analysis of mouse P0-P140 prethalamic histogenetic subdivisions and corresponding nuclear derivatives, in the context of local...
We present here a thorough and complete analysis of mouse P0-P140 prethalamic histogenetic subdivisions and corresponding nuclear derivatives, in the context of local tract landmarks. The study used as fundamental material brains from a transgenic mouse line that expresses LacZ under the control of an intragenic enhancer of Dlx5 and Dlx6 (Dlx5/6-LacZ). Subtle shadings of LacZ signal, jointly with pan-DLX immunoreaction, and several other ancillary protein or RNA markers, including Calb2 and Nkx2.2 ISH (for the prethalamic eminence, and derivatives of the rostral zona limitans shell domain, respectively) were mapped across the prethalamus. The resulting model of the prethalamic region postulates tetrapartite rostrocaudal and dorsoventral subdivisions, as well as a tripartite radial stratification, each cell population showing a characteristic molecular profile. Some novel nuclei are proposed, and some instances of potential tangential cell migration were noted.
Topics: Animals; Animals, Newborn; Chromosome Mapping; Female; Gene Expression; Homeodomain Proteins; Lac Operon; Mice; Mice, Inbred C57BL; Mice, Transgenic; Pregnancy; Thalamus; Zebrafish
PubMed: 32420617
DOI: 10.1002/cne.24952 -
PloS One 2020The combination of a fluorescent reporter and enzymatic reporter provides a flexible and versatile way for the study of diverse biological processes, such as the...
The combination of a fluorescent reporter and enzymatic reporter provides a flexible and versatile way for the study of diverse biological processes, such as the detection of transcription and translation. Thus, there is an urgent need to develop this novel bifunctional reporter system. This study reports the design, construction, and validation of a new dicistronic mCherry-lacZα reporter system by artificial lac operon and pbr operon models in lacZM15-producing E. coli. It allows two reporter genes to be co-transcribed into a dicistronic mRNA strand, followed by coupled expression of mCherry and lacZα. In artificial lac operons, expression of the downstream lacZα was demonstrated to be positively related to expression of the upstream ORF. In artificial pbr operons, compared with the insertion of downstream full-length lacZ, the insertion of downstream lacZα exerted a slight effect on the response from the upstream mCherry. Furthermore, the downstream lacZα reporter showed stronger response to Pb(II) than the downstream full-length lacZ. Importantly, the response sensitivity of downstream lacZα was still higher than that of upstream mCherry in a dual RFP-lacZα reporter construct. The highly efficient expression profile of the reporter lacZα peptide makes it a preferred downstream reporter in polycistronic constructs. This novel bifunctional reporter system offers a robust tool for biological studies.
Topics: Biosensing Techniques; Escherichia coli; Gene Expression; Genes; Genes, Reporter; Lac Operon; Lead; Luminescent Proteins; RNA, Messenger; Red Fluorescent Protein
PubMed: 31999769
DOI: 10.1371/journal.pone.0228456 -
Journal of Bacteriology May 1984Small bacteriophage Mu transposable elements containing the lac operon structural genes were constructed to facilitate the isolation and use of Mu insertions and lac...
Small bacteriophage Mu transposable elements containing the lac operon structural genes were constructed to facilitate the isolation and use of Mu insertions and lac gene fusions. These mini-Mu elements have selectable genes for either ampicillin or kanamycin resistance and can be used to form both transcriptional and translational lac gene fusions. Some of the mini-Mu-lac elements constructed are deleted for the Mu A and B transposition genes and form stable insertions that cannot undergo transposition unless complemented for these functions. A procedure was developed for selecting mini-Mu insertions specifically into plasmids, including commonly used high-copy-number cloning vectors such as pBR322. Mu insertions in pBR322 were found to be distributed around the plasmid, but insertions in certain regions occurred more frequently than in others.
Topics: Ampicillin; Bacteriophage mu; Chromosome Deletion; Chromosomes, Bacterial; DNA Transposable Elements; DNA, Recombinant; Kanamycin; Lac Operon; Mutation; Penicillin Resistance; Plasmids; Transduction, Genetic
PubMed: 6327606
DOI: 10.1128/jb.158.2.488-495.1984 -
Molecular Microbiology Apr 2007Having no known environmental reservoir, Streptococcus pyogenes, a bacterium responsible for a wider variety of human diseases than any other bacterial species, must... (Comparative Study)
Comparative Study
Having no known environmental reservoir, Streptococcus pyogenes, a bacterium responsible for a wider variety of human diseases than any other bacterial species, must rely on its host for metabolic substrates. Although a streptococcal aldolase, LacD.1, has been adapted to virulence gene regulation, both LacD.1 and a paralogous protein, LacD.2, are predicted to function in the tagatose 6-phosphate pathway for lactose and galactose utilization. In order to gain insight into the mechanism of the LacD.1 regulatory pathway and the role of genome context in the emergence of LacD.1's novel regulatory functions, we compared the function and regulation of the Lac.1 and Lac.2 loci. The Lac.1 operon is not inducible, and regulation by LacD.1 is independent of a functional tagatose 6-phosphate pathway and enhanced by the conserved truncation of upstream Lac.1 genes. In contrast, Lac.2 expression is sensitive to environmental carbohydrates, and LacD.2, not LacD.1, contributes to growth on galactose. Thus, we conclude that the Lac.1 locus has been specialized to participate in regulation, leaving efficient utilization of carbohydrate sources to the Lac.2 locus. The adaptation of LacD for transcription regulation may be an underappreciated strategy among prokaryotes, as homologues of this multifaceted enzyme are present in a broad range of species.
Topics: Bacterial Proteins; Biological Evolution; Carbohydrate Metabolism; Exotoxins; Gene Expression Regulation, Bacterial; Genome, Bacterial; Hexosephosphates; Lac Operon; Repressor Proteins; Sequence Deletion; Streptococcus pyogenes; Transcription, Genetic
PubMed: 17371500
DOI: 10.1111/j.1365-2958.2007.05663.x -
Journal of Bacteriology May 1985Expression of type 1 fimbriae in Escherichia coli exhibits phase variation, whereby individual cells can alternate between states of organelle expression (Fim+) and...
Expression of type 1 fimbriae in Escherichia coli exhibits phase variation, whereby individual cells can alternate between states of organelle expression (Fim+) and nonexpression (Fim-). Strains with a fimD-lac operon fusion, in which lac, rather than fimD, expression is under the control of the fimD promoter, undergo Lac+ in equilibrium Lac- phase variation, instead. After positioning a lambda prophage adjacent to the operon fusion, we were able to isolate specialized lambda phage carrying both the fimD-lac fusion and the phase variation control region. Introduction of such phage into an Fim+ strain resulted in construction of a strain with a double, independently switching phenotype (Fim+ in equilibrium Fim- and Lac+ in equilibrium Lac-), demonstrating that the region controlling phase variation is contiguous with the fimD-lac operon fusion and is cis acting. When the specialized lambda phage was propagated on a delta lac delta fim strain, phase variation occurred within the plaques, confirming that the phase variation control region is carried on the specialized transducing phage. All lysogens acquired the Lac+ in equilibrium Lac- phenotype, except for two nonswitching Lac+ recombinants, which acquired Lac+ in equilibrium Lac- phase variation only by trans complementation with fim. Phase variation of type 1 fimbriae, therefore, appears to involve both a cis-active element, which is cloned on a specialized lambda phage, and a trans-active permissive factor, which is not present on the phage, but rather must be supplied by the recipient strain in the transduction.
Topics: Escherichia coli; Fimbriae, Bacterial; Gene Expression Regulation; Genes, Bacterial; Genes, Regulator; Heterozygote; Lac Operon
PubMed: 2859269
DOI: 10.1128/jb.162.2.668-675.1985 -
Applied and Environmental Microbiology Sep 2014Comparison of the transcriptome of Streptococcus pneumoniae strain D39 grown in the presence of either lactose or galactose with that of the strain grown in the presence...
Comparison of the transcriptome of Streptococcus pneumoniae strain D39 grown in the presence of either lactose or galactose with that of the strain grown in the presence of glucose revealed the elevated expression of various genes and operons, including the lac gene cluster, which is organized into two operons, i.e., lac operon I (lacABCD) and lac operon II (lacTFEG). Deletion of the DeoR family transcriptional regulator lacR that is present downstream of the lac gene cluster revealed elevated expression of lac operon I even in the absence of lactose. This suggests a function of LacR as a transcriptional repressor of lac operon I, which encodes enzymes involved in the phosphorylated tagatose pathway in the absence of lactose or galactose. Deletion of lacR did not affect the expression of lac operon II, which encodes a lactose-specific phosphotransferase. This finding was further confirmed by β-galactosidase assays with PlacA-lacZ and PlacT-lacZ in the presence of either lactose or glucose as the sole carbon source in the medium. This suggests the involvement of another transcriptional regulator in the regulation of lac operon II, which is the BglG-family transcriptional antiterminator LacT. We demonstrate the role of LacT as a transcriptional activator of lac operon II in the presence of lactose and CcpA-independent regulation of the lac gene cluster in S. pneumoniae.
Topics: Culture Media; Galactose; Gene Deletion; Gene Expression Regulation, Bacterial; Glucose; Lac Operon; Lac Repressors; Lactose; Multigene Family; Promoter Regions, Genetic; Streptococcus pneumoniae; Trans-Activators
PubMed: 24951784
DOI: 10.1128/AEM.01370-14 -
The Journal of Histochemistry and... Apr 2021Secretogranin III (SgIII) is a granin protein involved in secretory granule formation in peptide-hormone-producing endocrine cells. In this study, we analyzed the...
Secretogranin III (SgIII) is a granin protein involved in secretory granule formation in peptide-hormone-producing endocrine cells. In this study, we analyzed the expression of the in the knockout mice produced by gene trapping () for the purpose of comprehensively clarifying the expression patterns of SgIII at the cell and tissue levels. In the endocrine tissues of mice, expression was observed in the pituitary gland, adrenal medulla, and pancreatic islets, where SgIII expression has been canonically revealed. expression was extensively observed in brain regions, especially in the cerebral cortex, hippocampus, hypothalamic nuclei, cerebellum, and spinal cord. In peripheral nervous tissues, expression was observed in the retina, optic nerve, and trigeminal ganglion. expression was particularly prominent in astrocytes, in addition to neurons and ependymal cells. In the cerebellum, at least four cell types expressed SgIII under basal conditions. The expression of SgIII in the glioma cell lines C6 and RGC-6 was enhanced by excitatory glutamate treatment. It also became clear that the expression level of SgIII varied among neuron and astrocyte subtypes. These results suggest that SgIII is involved in glial cell function, in addition to neuroendocrine functions, in the nervous system.
Topics: Animals; Cells, Cultured; Chromogranins; Lac Operon; Mice; Mice, Inbred C57BL; Mice, Knockout; Rats
PubMed: 33622062
DOI: 10.1369/0022155421996845 -
Proceedings of the National Academy of... Aug 1978Nucleotide analogs were substituted for unmodified nucleotides at specific sites in the lac operator sequence by a combination of chemical and enzymatic procedures. The...
Nucleotide analogs were substituted for unmodified nucleotides at specific sites in the lac operator sequence by a combination of chemical and enzymatic procedures. The nitrocellulose filter assay was used to study the interactions of these modified operators with wild-type (SQ) and tight-binding (QX86) lac repressors. These studies implicate directly the 5 methyl of thymine and the 2 amino of guanine as important operator-repressor contact sites. Furthermore, when these findings are combined with published results from other laboratories, a model for the lac operator-lac repressor interaction can be derived. Two important postulates follow from this model. (i) The repressor interacts at specific and defined sites with the N7 of guanine, the 5 methyl of thymine, the 2 amino of guanine, and the central major groove of the operator. (ii) The repressor binds to one side of the operator.
Topics: Base Sequence; Binding Sites; Lac Operon; Models, Biological; Repressor Proteins; Transcription Factors
PubMed: 278973
DOI: 10.1073/pnas.75.8.3578 -
Proceedings of the National Academy of... Dec 2015Epistatic interactions can frustrate and shape evolutionary change. Indeed, phenotypes may fail to evolve when essential mutations are only accessible through positive...
Epistatic interactions can frustrate and shape evolutionary change. Indeed, phenotypes may fail to evolve when essential mutations are only accessible through positive selection if they are fixed simultaneously. How environmental variability affects such constraints is poorly understood. Here, we studied genetic constraints in fixed and fluctuating environments using the Escherichia coli lac operon as a model system for genotype-environment interactions. We found that, in different fixed environments, all trajectories that were reconstructed by applying point mutations within the transcription factor-operator interface became trapped at suboptima, where no additional improvements were possible. Paradoxically, repeated switching between these same environments allows unconstrained adaptation by continuous improvements. This evolutionary mode is explained by pervasive cross-environmental tradeoffs that reposition the peaks in such a way that trapped genotypes can repeatedly climb ascending slopes and hence, escape adaptive stasis. Using a Markov approach, we developed a mathematical framework to quantify the landscape-crossing rates and show that this ratchet-like adaptive mechanism is robust in a wide spectrum of fluctuating environments. Overall, this study shows that genetic constraints can be overcome by environmental change and that cross-environmental tradeoffs do not necessarily impede but also, can facilitate adaptive evolution. Because tradeoffs and environmental variability are ubiquitous in nature, we speculate this evolutionary mode to be of general relevance.
Topics: Directed Molecular Evolution; Escherichia coli; Escherichia coli Proteins; Gene-Environment Interaction; Lac Operon; Point Mutation; Transcription Factors
PubMed: 26567153
DOI: 10.1073/pnas.1510282112 -
Developmental Dynamics : An Official... Mar 2004The chick embryo is a classic model that has been used to gain insight into developmental processes and cell fate within the embryo for over a century. For the most... (Review)
Review
The chick embryo is a classic model that has been used to gain insight into developmental processes and cell fate within the embryo for over a century. For the most part, investigators have implanted quail cells into a chicken embryo. A more powerful tool for developmental biology research than the quail:chick chimera system would be to have lines of transgenic chickens expressing reporter genes that are readily available to the research community. However, avian transgenic technology has been fraught with technical difficulties, and transgenic chickens expressing reporter genes have only recently been developed. The goal of this review is to report the technologies that have been used to generate transgenic chickens and to discuss the challenges in generating avian transgenics for developmental biology research.
Topics: Animals; Animals, Genetically Modified; Chick Embryo; Developmental Biology; Fertilization; Lac Operon; Models, Biological; Quail; Retroviridae; Transgenes
PubMed: 14991696
DOI: 10.1002/dvdy.10461