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PubMed1995

Receptor-specific induction of individual AP-1 components in B lymphocytes.

The inducible nuclear transcription factor complex, AP-1, typically consists of heterodimers between Jun and Fos proteins. Although components are drawn from families of related molecules, little is known about the physiologic regulation of jun- and fos-related gene products. In particular, it is not known whether expression of individual family members is stimulus-specific or whether the same signaling pathways are responsible for induction of all subunits. To clarify these issues, AP-1 components were examined following activation of primary B lymphocytes through two separate receptors, the surface Ig Ag receptor, and the CD40 receptor for T cell influences. Both forms of stimulation led to expression of JunB and JunD mRNA and protein; however, induction of JunB mediated by anti-Ig Ab was protein kinase C (PKC)-dependent, whereas induction mediated by CD40 ligand was resistant to PKC depletion. The two forms of stimulation diverged even further with respect to Fos expression. Although both stimuli induced c-Fos, expression of FosB was stimulus specific at both the mRNA and protein levels, in that this component was induced by anti-Ig but not by CD40 ligand. Stimulated expression of c-Fos and FosB was in all cases PKC-independent. These results provide evidence for receptor-specific differences in the expression of AP-1 components, primarily with respect to FosB. They also indicate that separate intracellular pathways may be used for induction of jun and fos gene products and that the same transcription factor (junB) may be triggered by two surface receptors through separate pathways that differ in PKC dependence.

Animals↗

PubMed2001

B-Bolivia, an allele of the maize b1 gene with variable expression, contains a high copy retrotransposon-related sequence immediately upstream.

The maize (Zea mays) b1 gene encodes a transcription factor that regulates the anthocyanin pigment pathway. Of the b1 alleles with distinct tissue-specific expression, B-Peru and B-Bolivia are the only alleles that confer seed pigmentation. B-Bolivia produces variable and weaker seed expression but darker, more regular plant expression relative to B-Peru. Our experiments demonstrated that B-Bolivia is not expressed in the seed when transmitted through the male. When transmitted through the female the proportion of kernels pigmented and the intensity of pigment varied. Molecular characterization of B-Bolivia demonstrated that it shares the first 530 bp of the upstream region with B-Peru, a region sufficient for seed expression. Immediately upstream of 530 bp, B-Bolivia is completely divergent from B-Peru. These sequences share sequence similarity to retrotransposons. Transient expression assays of various promoter constructs identified a 33-bp region in B-Bolivia that can account for the reduced aleurone pigment amounts (40%) observed with B-Bolivia relative to B-Peru. Transgenic plants carrying the B-Bolivia promoter proximal region produced pigmented seeds. Similar to native B-Bolivia, some transgene loci are variably expressed in seeds. In contrast to native B-Bolivia, the transgene loci are expressed in seeds when transmitted through both the male and female. Some transgenic lines produced pigment in vegetative tissues, but the tissue-specificity was different from B-Bolivia, suggesting the introduced sequences do not contain the B-Bolivia plant-specific regulatory sequences. We hypothesize that the chromatin context of the B-Bolivia allele controls its epigenetic seed expression properties, which could be influenced by the adjacent highly repeated retrotransposon sequence.

Alleles↗

PubMed2005

Bacterial genome adaptation to niches: divergence of the potential virulence genes in three Burkholderia species of different survival strategies.

BACKGROUND: Two closely related species Burkholderia mallei (Bm) and Burkholderia pseudomallei (Bp) are serious human health hazards and are potential bio-warfare agents, whereas another closely related species Burkholderia thailandensis (Bt) is a non-pathogenic saprophyte. To investigate the genomic factors resulting in such a dramatic difference, we first identified the Bm genes responsive to the mouse environment, and then examined the divergence of these genes in Bp and Bt. RESULTS: The genes down-expressed, which largely encode cell growth-related proteins, are conserved well in all three species, whereas those up-expressed, which include potential virulence genes, are less well conserved or absent notably in Bt. However, a substantial number of up-expressed genes is still conserved in Bt. Bm and Bp further diverged from each other in a small number of genes resulting from unit number changes in simple sequence repeats (ssr) in the homologs. CONCLUSION: Our data suggest that divergent evolution of a small set of genes, rather than acquisition or loss of pathogenic islands, is associated with the development of different life styles in these bacteria of similar genomic contents. Further divergence between Bm and Bp mediated by ssr changes may reflect different adaptive processes of Bm and Bp fine-tuning into their host environments.

Animals↗

PubMed2003

Cres2 and Cres3: new members of the cystatin-related epididymal spermatogenic subgroup of family 2 cystatins.

The cystatin-related epididymal spermatogenic (CRES) and recently identified testatin and cystatin T proteins define a new subgroup within the family 2 cystatins of cysteine protease inhibitors. Members of the CRES subgroup are predominantly expressed in reproductive tissues and lack critical cystatin active-site sequences implying divergent functions. To determine whether there are additional members of the subgroup, we searched nucleotide databases and identified two novel genes that we designated Cres2 and Cres3. These genes, like other subgroup members, encode proteins with four conserved cysteine residues and predicted molecular weights characteristic of family 2 cystatins but have divergent cystatin inhibitory sequences. Furthermore, the genes exhibited reproductive-specific expression with Cres2 exclusively expressed in the epithelial cells of the proximal and midcaput epididymal regions and Cres3 expressed in the proximal caput epididymal epithelium, Sertoli cells of the testis, and early follicles and corpora lutea in the ovary. Additional studies showed that, like Cres, both Cres2 and Cres3 genes are dependent on testicular factors for epididymal expression. Taken together, CRES2 and CRES3 represent new members of a subgroup of cystatin family 2 proteins that likely carry out tissue-specific functions distinct from that of typical cystatins.

Amino Acid Sequence↗

PubMed1996

Selectivity of IgE responses, mast cell sensitization, and cytokine expression in the immune response of Brown Norway rats to chemical allergens.

Sensitizing chemicals can induce various types of allergic disease, including contact dermatitis and occupational asthma. In the present study we have examined the nature of the immune response induced in Brown Norway (BN) rats by oxazolone (OX), a potent contact allergen, and by trimellitic anhydride (TMA), a chemical known to cause sensitization of the respiratory tract and occupational asthma. BN rats were exposed topically to either OX or TMA at doses selected to achieve similar levels of proliferative activity by draining LNC. Both chemicals stimulated hapten-specific IgG antibody responses, but only TMA induced specific IgE antibody, an increase in total serum IgE and active sensitization of mast cells. Draining LNC from OX-treated rats expressed elevated IFN-gamma mRNA, whereas those from TMA-treated rats expressed elevated IL-5 mRNA compared to controls. Furthermore, Con A-activated draining LNC from rats exposed to TMA, but not OX, released significantly increased concentrations of IL-4. In conclusion, different chemical allergens can induce in the BN rat divergent patterns of IgE response and cytokine expression.

Allergens↗

PubMed2004

Amphioxus and ascidian Dmbx homeobox genes give clues to the vertebrate origins of midbrain development.

The ancestral chordate neural tube had a tripartite structure, comprising anterior, midbrain-hindbrain boundary (MHB) and posterior regions. The most anterior region encompasses both forebrain and midbrain in vertebrates. It is not clear when or how the distinction between these two functionally and developmentally distinct regions arose in evolution. Recently, we reported a mouse PRD-class homeobox gene, Dmbx1, expressed in the presumptive midbrain at early developmental stages, and the hindbrain at later stages, with exclusion from the MHB. This gene provides a route to investigate the evolution of midbrain development. We report the cloning, genomic structure, phylogeny and embryonic expression of Dmbx genes from amphioxus and from Ciona, representing the two most closely related lineages to the vertebrates. Our analyses show that Dmbx genes form a distinct, ancient, homeobox gene family, with highly conserved sequence and genomic organisation, albeit more divergent in Ciona. In amphioxus, no Dmbx expression is observed in the neural tube, supporting previous arguments that the MHB equivalent region has been secondarily modified in evolution. In Ciona, the CiDmbx gene is detected in neural cells caudal to Pax2/5/8-positive cells (MHB homologue), in the Hox-positive region, but, interestingly, not in any cells rostral to them. These results suggest that a midbrain homologue is missing in Ciona, and argue that midbrain development is a novelty that evolved specifically on the vertebrate lineage. We discuss the evolution of midbrain development in relation to the ancestry of the tripartite neural ground plan and the origin of the MHB organiser.

Amino Acid Sequence↗

PubMed2000

Tyrosine 50 at the subunit interface of dimeric human glutathione transferase P1-1 is a structural key residue for modulating protein stability and catalytic function.

The dimer interface in human GSTP1-1 has been altered by site-directed mutagenesis of Tyr50. It is shown that the effects of some mutations of this single amino acid residue are as detrimental for enzyme function as mutations of Tyr8 in the active site. The dimeric structure is a common feature of the soluble glutathione transferases and the structural lock-and-key motif contributing to the subunit-subunit interface is well conserved in classes alpha, mu, and pi. The key residue Tyr50 in GSTP1-1 was replaced with 5 different amino acids with divergent properties and the mutant proteins expressed and characterized. Mutant Y50F is an improved variant, with higher thermal stability and higher catalytic efficiency than the wild-type enzyme. The other mutants studied are also dimeric proteins, but have lower stabilities and catalytic activities that are reduced by a factor of 10(2)-10(4) from the wild-type value. Mutants Y50L and Y50T are characterized by a markedly increased K(M) value for GSH, while the effect is mainly due to decreased k(cat) values for mutants Y50A and Y50R. In conclusion, residue 50 in the interface governs both structural stability and catalytic function.

Amino Acids↗

PubMed2005

TRPC3: a versatile transducer molecule that serves integration and diversification of cellular signals.

Transient receptor potential (TRP) proteins have been recognized as sensors for a wide variety of external and internal signals involved in maintenance of cellular homeostasis and control of physiological functions. Evidence of a striking versatility in terms of signal integration and transduction has been reported for members of the canonical (or classical) TRP subfamily (TRPCs). TRPC species are cation channel subunits and emerge as multifunctional signal transduction molecules that are able to function as components of divergent signalplexes. Results obtained in heterologous expression systems suggest TRPC3 as a paradigm of multifunctional signal transduction by a cation channel protein. TRPC3 serves cellular Ca(2+) signaling by multiple mechanisms and may control a variety of distinct physiological functions. In this review, we summarize current knowledge on the properties and possible signaling partners of TRPC3, and discuss the role of TRPC3 channel proteins in cellular signaling networks.

Animals↗

PubMed2005

Hybrid disadvantage in the larval foraging behaviour of the two neotropical species of Drosophila pavani and Drosophila gaucha.

Flies from two populations of the Chilean endemic neotropical species Drosophila pavani and two populations of its sibling species Drosophila gaucha were crossed reciprocally to obtain intra- and interspecific hybrids. The developmental pathways of locomotor activity and feeding rate were analysed for eleven of twelve possible genotype groups. The hybrids showed reduced fitness indicated by a decrease in the measured traits. Hybrid disadvantage was strongest in interspecific hybrids, especially with respect to feeding behaviour. This evidence supports the contention that D. pavani and D. gaucha have evolved different coadapted gene pools controlling the developmental pathways for behavioural traits expressed during larval foraging; but genetic divergence affecting these behaviours has also taken place between locally adapted populations within each species.

Animals↗

PubMed1983

A single gene encodes multiple neuropeptides mediating a stereotyped behavior.

Egg laying in Aplysia is characterized by a stereotyped behavioral array which is mediated by several neuroactive peptides. We have sequenced two genes encoding the A and B peptides thought to initiate the egg-laying process, as well as a gene encoding egg-laying hormone (ELH) which directly mediates the behavioral array. The three genes share 90% sequence homology and are representatives of a small multigene family. Each gene encodes a protein precursor in which the active peptides are flanked by internal cleavage sites providing the potential to generate multiple small peptides. Each of the three genes consists of sequences homologous to A or B peptide as well as ELH. Although these genes share significant nucleotide homology, they have diverged such that different member genes express functionally related but nonoverlapping sets of neuroactive peptides in different tissues.

Animals↗

PubMed1996

Child development and long-term outcomes: a population health perspective and summary of successful interventions.

Studies of socioeconomic gradients in mortality in wealthy societies reveal that they have been persist, and included most of the principal causes of death, even during the era when these principal causes of death have entirely changed. This observation has led to an interest in the ways in which the diversity of conditions of life, unfolding over the life cycle, can become embedded in human biology and subsequently affect health status and vitality. There is evidence that childhood experiences affect subsequent health status (as well as well-being and competence) in profound and long-lasting ways. Conflicting explanatory models of the impact of childhood experiences have been advanced, whose conflicts are political in nature, in that the reflect divergent beliefs about how human potential expresses itself, and, also, about the nature of the obligations which members of society have to one another. Notwithstanding these conflicts, a body of evidence derived from intervention studies in the post-neonatal, preschool, and school age periods suggest that performance in two basic domains of child development, the cognitive and the social-emotional, can be modified in ways which improve health, well-being, and competence in the long-term.

Child↗

PubMed1999

The TINS Lecture. Understanding the roles of Otx1 and Otx2 in the control of brain morphogenesis.

The murine homologs of the orthodenticle (otd) gene of Drosophila, Otx1 and Otx2, have an important role in brain morphogenesis. Analysis of Otx1 and Otx2 null mice reveals that Otx1 is required primarily for corticogenesis and sense-organ development,while Otx2 is necessary for specification and maintenance of anterior neural plate as well as for proper gastrulation. Cross-phylum recoveries of Otx1 abnormalities by Drosophila otd, and vice versa, indicate that genetic functions required in mammalian-brain development evolved in a primitive ancestor of flies and mice. Knock-in mouse models in which Otx2 was replaced with Otx1, and vice versa, provide evidence that the existence of Otx1-/- and Otx2-/- divergent phenotypes largely reflects differences in expression patterns rather than in the biochemical activity of OTX1 and OTX2. In evolutionary terms, some of these findings lead us to hypothesize a fascinating and crucial role for Otx genes that contributes to the genetic program required for the specification of the development of the vertebrate head.

Animals↗

PubMed2002

GnRH signaling pathways regulate differentially the tilapia gonadotropin subunit genes.

Exposure of tilapia pituitary cells in culture to salmon gonadotropin-releasing hormone (sGnRH; 0.01-100 nM) elevated the phosphorylated extracellular signal-regulated kinase (pERK) levels. sGnRH also elevated the alpha, FSHbeta and LHbeta subunit mRNA levels. The phorbol ester, 1-O-tetradecanoyl phorbol-13-acetate (TPA; 12.5 nM) increased pERK levels, whereas protein kinase C (PKC) depletion or inhibition by GF109203X (GF; 0.01-10 microM) suppressed GnRH-activated ERKs. GF too abated the GnRH-induced alpha and LHbeta mRNA levels, but had no effect on those of FSHbeta. Forskolin (0.001-100 microM) activated ERK, while inhibition of protein kinase A (PKA) by H89 (0.01-10 microM) suppressed pERK levels and all GnRH-stimulated gonadotropin subunit transcripts. Exposure of cells to the mitogen-activated protein kinase kinase (MAPK kinase; MEK) inhibitor (PD98059; PD 10, 25 and 50 microM) completely blocked GnRH-induced increase in ERKs activation. Furthermore, PD suppressed the alpha and LHbeta mRNA responses to GnRH, but had no effect on FSHbeta mRNA levels. It is suggested that in tilapia the differential regulation of gonadotropin subunit gene expression by GnRH results from a divergent recruitment of signal transduction pathways, activated upon GnRH binding; PKC-ERK cascade is involved in elevating alpha and LHbeta mRNAs, whereas induction of FSHbeta transcript is ERK-independent and is under direct cAMP-PKA regulation or through other MAPK cascades.

Animals↗

PubMed2002

Conservation in divergent solanaceous species of the unique gene structure and enzyme activity of a gametophytically-expressed flavonol 3-O-galactosyltransferase.

Flavonol 3-O-galactosyltransferase (F3GalTase) is a pollen-specific enzyme which glycosylates the flavonols required for germination in petunia. The highly restricted tissue-specific expression and substrate usage make F3GalTase unique among all other flavonoid glycosyltransferases (GTs) described to date, including the well characterized Bronze 1 (Bz1) gene of maize. RFLP mapping, DNA gel blot, and sequence analyses showed that the single copy F3galtase gene has a different genomic organization than Bz1. Within the promoter of F3galtase are potential regulatory motifs which may confer pollen-specific gene expression and activation by Myb and bHLH transcription factors. However, we provide evidence that F3galtase is not regulated by An4, which encodes a Myb factor known to regulate anthocyanin accumulation in petunia anthers. An unexpected feature of the F3galtase promoter was the presence of large blocks of chloroplast and mitochondrial DNA. Gel blot analyses of genomic DNA from the progenitors of Petunia hybrida, as well as from Nicotiana tabacum, indicated that migration of organellar DNA into the F3galtase gene was an ancient event that occurred prior to speciation of the Solanaceae. Together with enzyme assays and HPLC analyses of pollen extracts from tobacco, tomato, and potato, these results confirmed that the unique F3galtase gene structure, enzyme activity, and pollen-specific flavonol glucosylgalactosides are conserved throughout the Solanaceae.

Base Sequence↗

PubMed2002

Divergent regulation of the HEMA gene family encoding glutamyl-tRNA reductase in Arabidopsis thaliana: expression of HEMA2 is regulated by sugars, but is independent of light and plastid signalling.

The synthesis of 5-aminolevulinic acid (ALA) is a key regulatory step for the production of hemes and chlorophyll via the tetrapyrrole synthesis pathway. The first enzyme committed to ALA synthesis is glutamyl-tRNA reductase encoded in Arabidopsis by a small family of nuclear-encoded HEMA genes. To better understand the regulation of the tetrapyrrole synthesis pathway we have made a detailed study of HEMA2 expression with transgenic Arabidopsis thaliana L. Col. plants carrying chimeric HEMA2 promoter:gusA fusion constructs. Our results show that the HEMA2 promoter directs expression predominantly to roots and flowers, but that HEMA2 is also expressed at low levels in photosynthetic tissues. Deletion analysis of the HEMA2 promoter indicates that a ca. 850 bp fragment immediately upstream of the HEMA2 coding region is sufficient to drive regulated gusA expression. In contrast to HEMA1, HEMA2 is not up-regulated by red, far-red, blue, UV or white light. In addition, elimination of a promotive plastid signal by Norflurazon-induced photobleaching of plastids had no effect on HEMA2 expression while being required for normal white-light induction of HEMA1. HEMA2 expression in the cotyledons is inhibited by the presence of sucrose or glucose, but not fructose, and this response is light-independent. HEMA1 expression in cotyledons is also inhibited by sugars, but in a strictly light-dependent manner. The roles of HEMA1 and HEMA2 in meeting cellular tetrapyrrole requirements are discussed.

Aldehyde Oxidoreductases↗

PubMed2004

Sulfation pattern in glycosaminoglycan: does it have a code?

Heparan sulfate chains (HS) are initially synthesized on core proteins as linear polysaccharides composed of glucuronic acid--N-acetylglucosamine repeating units and subjected to marked structural modification by sulfation (N-, 2-O-, 6-O-, 3-O-sulfotransferases) and epimerization (C5-epimerase) at the Golgi lumen and further by desulfation (6-O- endosulfatase) at the cell surface, after which divergent fine structures are generated. The expression patterns and specificity of the modifying enzymes are, at least partly, responsible for the elaboration of these fine structures of heparan sulfate. HS interacts with many proteins including growth factors (GF) and morphogens through specific fine structures. Recent biochemical and genetic studies have presented evidence that HS plays important roles in cell behavior and organogenesis. In knock-down experiments of heparan sulfate 6-O-sulfotransferase, 6-O-sulfated units in HS have been shown to act as a stimulator or suppressor according to individual GF/morphogen signaling systems.

Animals↗

PubMed1997

A role for oestrogens in the male reproductive system.

Oestrogen is considered to be the 'female' hormone, whereas testosterone is considered the 'male' hormone. However, both hormones are present in both sexes. Thus sexual distinctions are not qualitative differences, but rather result from quantitative divergence in hormone concentrations and differential expressions of steroid hormone receptors. In males, oestrogen is present in low concentrations in blood, but can be extraordinarily high in semen, and as high as 250 pg ml(-1) in rete testis fluids, which is higher than serum oestradiol in the female. It is well known that male reproductive tissues express oestrogen receptors, but the role of oestrogen in male reproduction has remained unclear. Here we provide evidence of a physiological role for oestrogen in male reproductive organs. We show that oestrogen regulates the reabsorption of luminal fluid in the head of the epididymis. Disruption of this essential function causes sperm to enter the epididymis diluted, rather than concentrated, resulting in infertility. This finding raises further concern over the potential direct effects of environmental oestrogens on male reproduction and reported declines in human sperm counts.

Animals↗

PubMed1999

Evolution of oligomeric proteins. The unusual case of a dimeric ribonuclease.

The model system made up of a monomeric and a dimeric ribonuclease of the pancreatic-type superfamily has recently attracted the attention of investigators interested in the evolution of oligomeric proteins. In this system, bovine pancreatic ribonuclease (RNase A) is the monomeric prototype, and bovine seminal ribonuclease (BS-RNase) is the dimeric counterpart. However, this evolutionary case is unusual, as BS-RNase is the only dimeric member of the whole large superfamily comprising more than 100 identified members from amphibia, aves, reptilia and mammalia. Furthermore, although the seminal-type RNase gene can be traced back to the divergence of the ruminants, it is expressed only in a single species (Bos taurus). These unusual findings are discussed, as well as previous hypotheses on the evolution of seminal RNase. Furthermore, a new 'minimalist' hypothesis is proposed, in line with basic principles of structural biology and molecular evolution.

Amino Acid Sequence↗