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PubMed1983

Transcription in human fibroblasts permissively infected by human cytomegalovirus strain AD169.

We used cloned subgenomic DNA fragments of human cytomegalovirus strain AD169 as hybridization reagents to analyze the sites of transcription and abundance of viral RNA in permissively infected human embryonic lung cells. RNA extracted from immediate early, early, middle, and late times in the infection was attached to filters and hybridized with excess cloned subgenomic fragments. Each hybridization was performed with an internal standard to allow quantitation of the RNA concentration and standardization for the variation in probe complexity and specific activity. We found immediate early transcription in the AD169 strain occurring primarily from three regions in the long unique segment at 0.061-0.110, 0.117-0.142, and 0.588-0.616 map units. A low level of transcription was also detected from the long unique segment at 0.230-0.372, 0.419-0.437 and 0.703-0.707 map units and the short unique segment and terminal repeats at 0.00-0.046, 0.776-0.854, and 0.892-1.00 map units. At 8 hr after infection in the presence of de novo protein synthesis, the transcription pattern was changed. Two of the major immediate early sites at 0.061-0.110 and 0.117-0.142 map units were represented less abundantly in the absence of cycloheximide while the site at 0.588-0.616 map units was represented at the same level. The most abundant early RNA was synthesized from the terminal repeat sequences and part of the short unique segment at 0.00-0.046, 0.776-0.822, and 0.892-1.00 map units. Steady-state RNA from the midpoint of the infection hybridized with most regions of the genome. Abundantly transcribed regions included the abundant early sites mentioned above (0.00-0.046, 0.588-0.616, 0.776-0.822, and 0.892-1.00 map units), several new sites in the long unique segment at 0.104-0.110, 0.576-0.588, 0.653-0.664, 0.703-0.707, and 0.766-0.776 map units and the L-S junction fragment at 0.804-0.854 map unit. RNA from late in the infection hybridized to all subgenomic fragments. The sites of de novo RNA synthesis along the genome were determined by hybridizing pulse-labeled RNA to individual cloned subgenomic fragments attached to filters. Transcription from the terminal repeat sequences and the long unique segment at 0.576-0.588 map unit accounted for 40% of the total viral RNA synthesized from 22 to 28 hr after infection. Of the total de novo RNA synthesis from 71 to 77 hr after infection, 4.3% was virus specific and 47% of the total de novo synthesized viral RNA hybridized to the terminal repeat sequences.

Cell Line↗

PubMed2002

Development of the specialized AMPA receptors of auditory neurons.

At maturity, the AMPA receptors of auditory neurons exhibit very rapid desensitization kinetics and high permeability to calcium, reflecting the predominance of GluR3 flop and GluR4 flop subunits and the paucity of GluR2. We used mRNA analysis and immunoblotting to contrast the development of AMPA receptor structure in the chick cochlear nucleus [nucleus magnocellularis (NM)] with that of the slowly desensitizing and calcium-impermeable AMPA receptors of brainstem motor neurons in the nucleus of the glossopharyngeal/vagal nerves. The relative abundance of transcripts for GluRs 1-4 changes substantially in auditory (but not motor) neurons after embryonic day (E)10, with large decreases in GluR2 and increases in GluR3 and GluR4. Relative to the motor neurons, NM neurons show a higher abundance of flop isoforms of GluRs 2-4 at E10, suggesting that auditory neurons are already biased toward expression of flop isoforms before the onset of synaptic function at E11. Immunoreactivities in NM show very distinct developmental patterns from E13 onward: GluR2 declines by >90%, GluR3 increases threefold, and GluR4 remains relatively constant. Our results show that there are a series of critical points during normal development, most occurring after the onset of function, when rapid changes in receptor structure (occurring via both transcriptional and post-transcriptional control mechanisms) produce the specialized AMPA receptor functions that enable auditory neurons to accurately encode acoustic information.

Alternative Splicing↗

PubMed1997

Expression of proteinases and proteinase inhibitors during embryo-uterine contact in the pig.

Implantation in pigs is noninvasive and characterized by interdigitation of embryonic and endometrial epithelial cell processes. However, when pig embryos are transferred to ectopic sites, trophoblast becomes invasive. The objective of this study was to evaluate expression of proteinases and proteinase inhibitors in pig embryos and uteri at the time of endometrial attachment. RNA was extracted from Day 15.75 pig embryos and uteri and reverse transcribed, and cDNA was amplified by polymerase chain reactions using primers specific for urokinase-type plasminogen activator (uPA), matrix metalloproteinases-2 and -9 (MMP-2 and -9), and tissue inhibitors of MMP-1, -2, and -3 (TIMP-1, -2, and -3). Localization of transcripts for the genes of interest in embryos and uteri was performed using in situ hybridization with antisense riboprobes. Day 15.75 pig embryos and uteri expressed transcripts for uPA, MMP-2 and -9, and TIMP-1, -2, and -3. In situ hybridization revealed weak expression of uPA in the trophectoderm and moderate expression in the adjacent extraembryonic endoderm. TIMP-1 transcripts were abundant in extraembryonic endoderm and scattered throughout the trophectoderm. TIMP-2 appeared to be expressed in all cells of the embryo. TIMP-3 expression was observed in the trophectoderm and, to a lesser extent, in the extraembryonic endoderm. Specific localization of MMP-2 and -9 transcripts above background was not observed by in situ hybridization in either embryos or uterus. Uterine expression of uPA and TIMP-1, -2 and -3 was localized to the endometrial stroma. Transcripts of these genes were not observed in either the luminal or glandular endometrial epithelium. These results suggest that pig embryos and uteri express a wide array of proteinases and proteinase inhibitors during the period of uterine association. The abundant expression of proteinases and proteinase inhibitors during the period of uterine association. The abundant expression of TIMP in pig embryos may partially explain the absence of invasive implantation in this species in contrast to implantation typified by rodents and primates.

Animals↗

PubMed1998

The mouse Gtl2 gene is differentially expressed during embryonic development, encodes multiple alternatively spliced transcripts, and may act as an RNA.

We have isolated a novel mouse gene (Gtl2) from the site of a gene trap integration (Gtl2lacZ) that gave rise to developmentally regulated lacZ expression, and a dominant parental-origin-dependent phenotype. Heterozygous Gtl2lacZ mice that inherited the transgene from the father showed a proportionate dwarfism phenotype, whereas the penetrance and expressivity of the phenotype was strongly reduced in Gtl2lacZ mice that inherited the transgene from the mother. Gtl2 expression is highly similar to the beta-galactosidase staining pattern, and is down-regulated but not abolished in mice carrying the Gtl2lacZ insertion. In early postimplantation embryos, Gtl2 is expressed in the visceral yolk sac and embryonic ectoderm. During subsequent development and organogenesis, Gtl2 transcripts are abundant in the paraxial mesoderm closely correlated with myogenic differentiation, in parts of the central nervous system, and in the epithelial ducts of developing excretory organs. The Gtl2 gene gives rise to various differentially spliced transcripts, which contain multiple small open reading frames (ORF). However, none of the ATG codons of these ORFs is in the context of a strong Kozak consensus sequence for initiation of translation, suggesting that Gtl2 might function as an RNA. Nuclear Gtl2 RNA was detected in a temporally and spatially regulated manner, and partially processed Gtl2 transcripts were readily detected in Northern blot hybridizations of polyadenylated RNA, suggesting that primary Gtl2 transcripts are differently processed in various cell types during development. Gtl2 transcript levels are present in parthenogenic embryos but may be reduced, consistent with the pattern of inheritance of the Gtl2lacZ phenotype.

Alternative Splicing↗

PubMed1995

Two auxin-responsive domains interact positively to induce expression of the early indoleacetic acid-inducible gene PS-IAA4/5.

The plant growth hormone indole-3-acetic acid (IAA) transcriptionally activates expression of several genes in plants. We have previously identified a 164-bp promoter region (-318 to -154) in the PS-IAA4/5 gene that confers IAA inducibility. Linker-scanning mutagenesis across the region has identified two positive domains: domain A (48 bp; -203 to -156) and domain B (44 bp; -299 to -256), responsible for transcriptional activation of PS-IAA4/5 by IAA. Domain A contains the highly conserved sequence 5'-TGTCCCAT-3' found among various IAA-inducible genes and behaves as the major auxin-responsive element. Domain B functions as an enhancer element which may also contain a less efficient auxin-responsive element. The two domains act cooperatively to stimulate transcription; however, tetramerization of domain A or B compensates for the loss of A or B function. The two domains can also mediate IAA-induced transcription from the heterologous cauliflower mosaic virus 35S promoter (-73 to +1). In vivo competition experiments with icosamers of domain A or B show that the domains interact specifically and with different affinities to low abundance, positive transcription factor(s). A model for transcriptional activation of PS-IAA4/5 by IAA is discussed.

Base Sequence↗

PubMed1997

Differential gene expression in ripening banana fruit.

During banana (Musa acuminata L.) fruit ripening ethylene production triggers a developmental cascade that is accompanied by a massive conversion of starch to sugars, an associated burst of respiratory activity, and an increase in protein synthesis. Differential screening of cDNA libraries representing banana pulp at ripening stages 1 and 3 has led to the isolation of 11 nonredundant groups of differentially expressed mRNAs. Identification of these transcripts by partial sequence analysis indicates that two of the mRNAs encode proteins involved in carbohydrate metabolism, whereas others encode proteins thought to be associated with pathogenesis, senescence, or stress responses in plants. Their relative abundance in the pulp and tissue-specific distribution in greenhouse-grown banana plants were determined by northern-blot analyses. The relative abundance of transcripts encoding starch synthase, granule-bound starch synthase, chitinase, lectin, and a type-2 metallothionein decreased in pulp during ripening. Transcripts encoding endochitinase, beta-1,3-glucanase, a thaumatin-like protein, ascorbate peroxidase, metallothionein, and a putative senescence-related protein increased early in ripening. The elucidation of the molecular events associated with banana ripening will facilitate a better understanding and control of these processes, and will allow us to attain our long-term goal of producing candidate oral vaccines in transgenic banana plants.

DNA, Complementary↗

PubMed2006

A dynamic expression survey identifies transcription factors relevant in mouse digestive tract development.

Tissue-restricted transcription factors (TFs), which confer specialized cellular properties, are usually identified through sequence homology or cis-element analysis of lineage-specific genes; conventional modes of mRNA profiling often fail to report non-abundant TF transcripts. We evaluated the dynamic expression during mouse gut organogenesis of 1381 transcripts, covering nearly every known and predicted TF, and documented the expression of approximately 1000 TF genes in gastrointestinal development. Despite distinctive structures and functions, the stomach and intestine exhibit limited differences in TF genes. Among differentially expressed transcripts, a few are virtually restricted to the digestive tract, including Nr2e3, previously regarded as a photoreceptor-specific product. TFs that are enriched in digestive organs commonly serve essential tissue-specific functions, hence justifying a search for other tissue-restricted TFs. Computational data mining and experimental investigation focused interest on a novel homeobox TF, Isx, which appears selectively in gut epithelium and mirrors expression of the intestinal TF Cdx2. Isx-deficient mice carry a specific defect in intestinal gene expression: dysregulation of the high density lipoprotein (HDL) receptor and cholesterol transporter scavenger receptor class B, type I (Scarb1). Thus, integration of developmental gene expression with biological assessment, as described here for TFs, represents a powerful tool to investigate control of tissue differentiation.

Animals↗

PubMed1991

The relationship between cell proliferation and the transcription of the nuclear oncogenes c-myc, c-myb and c-ets-1 during feather morphogenesis in the chick embryo.

We have described the expression of three nuclear protooncogenes, c-myc, c-myb and c-ets-1 during feather morphogenesis in the chick embryo. In parallel with the expression patterns obtained by in situ hybridization, we have mapped the spatial distribution of S-phase cells by monitoring the incorporation of 5-bromodeoxyuridine. We do not detect c-myc or c-myb transcripts during the early stages when S-phase cells are scattered in the dermis and in the epidermis. Rather c-ets-1 transcripts are abundant in the dermal cells which divide and accumulate under the uniform epidermis. At the onset of the formation of the feather bud, cells within each rudiment cease DNA replicative activities and c-myc transcripts are detected both in the epidermis and in the underlying dermis. This expression precedes the reentry into the S phase. The transcription of c-myb, which has been previously tightly linked to hemopoietic cells is also detected in the developing skin. This expression is essentially located in proliferating epidermal cells on and after the beginning of feather outgrowth. As feather outgrowth proceeds, the distribution of c-myc and c-myb transcripts is restricted to the highly proliferating epidermis. In contrast c-ets-1 transcripts are never detected in the epidermis. During the later stages of skin morphogenesis, the transcription of c-ets-1 is restricted to the endothelial cells of blood vessels, as previously described. We suggest that the differential expression of these nuclear oncogenes reflects the activation of different mitotic controlling pathways during the development of the skin.

Animals↗

PubMed1996

The avian IGF type 1 receptor: cDNA analysis and in situ hybridization reveal conserved sequence elements and expression patterns relevant for the development of the nervous system.

Insulin-like growth factor type 1 receptor (IGF-1R) is a tyrosine kinase with a key role in development. The primary structure of IGF-1R is known for mammalian species, but not for birds. The avian embryo, however, provides an ideal system for the experimental study of neurogenesis. We therefore cloned the complete coding sequence of the chicken IGF-1R from a cDNA library and analyzed its embryonic expression by Northern blot and in situ hybridization. The deduced chicken IGF-1R precursor of 1363 amino acids was 85% identical to human IGF-1R and did not show deletions or insertions in critical positions, when compared to its mammalian homologues. Notably, all cysteine residues in the extracellular domains, and 15 of the 17 N-linked glycosylation sites found in human IGF-1R were also present in the chicken receptor. An 11 kb transcript was abundant in developing nervous tissues, kidney, pancreas and the gastrointestinal tract. The early in situ expression patterns in 20-somite embryos revealed high levels of IGF-1R mRNA in the neuroepithelia, notochord and somites. At embryonic day 4 (E4), high concentrations of IGF-1R transcripts were found again primarily in the neuroepithelia and, to a lesser degree, in the sensory ganglia and diverse mesenchymal derivatives. During the second half of embryonic development, IGF-1R expression in the CNS was particularly abundant in telencephalic regions, including the olfactory bulb, hippocampus, striatum and piriform cortex, and also in the optic tectum and cerebellum. By the use of cDNA cloning and in situ hybridization this study reveals conserved amino acid sequence elements between birds and mammals, and developmental expression patterns that are compatible with an important role of this receptor in growth, differentiation and maturation of the avian CNS.

Animals↗

PubMed2005

Effect of serum and cumulus cell expansion on marker gene transcripts in bovine cumulus-oocyte complexes during maturation in vitro.

OBJECTIVE: To determine the distribution of transcripts encoding the FSH receptor (FSHr), LH receptor (LHr), connexin 43 (Cx43), cyclooxygenase-2 (COX-2), and prostaglandin E(2) receptors 2 and 3 (EP2 and EP3) within bovine cumulus-oocyte complexes (COCs) and denuded oocytes and investigate the influence of gonadotropins, serum, and cumulus cell expansion on the abundance of transcripts encoding these genes. DESIGN: Prospective controlled animal study. SETTING: University research laboratory. PATIENT(S): Animal models for human studies. INTERVENTION(S): Cumulus-oocyte complexes were treated in culture with serum and gonadotropin-supplemented media to examine the effects to mRNA transcript levels. MAIN OUTCOME MEASURE(S): Variation in mRNA transcript levels. RESULT(S): Luteinizing hormone receptor, FSHr, and EP3 mRNAs were detected in intact COCs and not in cumulus cell-denuded oocytes, whereas Cx43, COX-2, and EP2 mRNAs were found in both COCs and oocytes. The relative abundance of marker gene mRNAs did not vary in media containing no additives or FSH alone, independent of whether the media induced cumulus cell expansion. However, the presence of serum in maturation media significantly decreased expression of all mRNAs except LHr. CONCLUSION(S): The relative abundance of COC mRNAs is altered by serum in the maturation medium, which may signify long-term consequences for embryonic development.

Animals↗

PubMed1983

Expression of Drosophila heat-shock cognate genes during heat shock and development.

The Drosophila genome contains a number of genes related to the major heat-shock-inducible (Hsp70) genes of Drosophila. The structure and expression of three of these heat-shock cognate (Hsc) genes have been studied; Hsc1 (previously described), Hsc2, and Hsc4 are dispersed on chromosome 3 at cytological loci 70C, 87D, and 88E, respectively. RNA homologous to Hsc4 was shown by hybridization selection translation experiments to encode a protein of approximately 70kd, with similar, but distinguishable, mobility to that of the heat-shock-inducible 70K protein. Because of variance in size of the 5' nonprotein coding region, it was possible to identify in adult flies distinct transcripts from each gene. Unlike transcripts from Hsp genes, the abundance of the Hsc transcripts was not increased after heat shock. Transcription of these Hsc genes is regulated during development. While transcripts from Hsc4 were equally abundant in RNA isolated from embryos, larvae and adults, Hsc1 and Hsc2 transcripts were not detected in embryo and larval RNA, and are therefore at least 20 times less abundant in these stages than in adults. The primary DNA sequences of the regions homologous to that encoding the amino terminus of hsp70 were compared. Approximately 76% homology of the base sequence and 78% homology of the deduced amino acid sequence were found among the four genes. The Hsp70 genes contain no intervening sequences; Hsc4 contains no insertions relative to Hsp70 in the region encoding the first 101 aa. However, in the codon specifying aa66 Hsc1 is interrupted by 1.7 kb of DNA; in the codon for aa55 Hsc2 contains an insertion of about 650 b. The sequences at the 5' and 3' junctions of the insertions in both Hsc1 and Hsc2 are similar to those found in intervening sequences of Drosophila and of many other organisms.

Amino Acid Sequence↗

PubMed2003

The regulation of EFG1 in white-opaque switching in Candida albicans involves overlapping promoters.

EFG1, which encodes a trans-acting factor, is expressed as a more abundant 3.2 kb transcript in the white phase and as a less abundant 2.2 kb transcript in the opaque phase of the white-opaque transition in Candida albicans. To understand how alternative phase-specific mRNAs are transcribed from the same gene locus, the 2320 bp upstream region of the gene was functionally characterized by analysing the -activity of deletion derivatives in a luciferase-based reporter system. The white phase-specific promoter contained three discrete sequences involved in white phase-specific activation, between -2022 and -1809 bp (AR1), between -1809 and -1727 bp (AR2) and between -922 and -840 bp (AR3). A higher resolution deletion and mutation analysis of AR2 revealed two regions between -1809 and -1787 bp and between -1764 and -1728 bp that are responsible for AR2 activation. Targeting of promoter constructs to the ectopic ADE2 genomic site and the 3' end of the EFG1 genomic site revealed a positional requirement for white phase-regulated activation specific for the AR2 region of the promoter. Gel mobility shift assays using AR2 revealed a white phase-specific activation complex. No discrete activation sequences were identified in the overlapping promoter of the opaque phase-specific EFG1 transcript. The strength of opaque phase activation was directly proportional to the length of the promoter. Northern analysis excluded the possibility of an opaque phase-specific repressor. These results demonstrate overlapping promoters for white and opaque phase-specific expression of the gene for the transcription factor Efg1, with distinctly different mechanisms of phase-specific activation.

Base Sequence↗

PubMed1991

Inverse relationship between human papillomavirus (HPV) type 16 early gene expression and cell differentiation in nude mouse epithelial cysts and tumors induced by HPV-positive human cell lines.

Two human papillomavirus type 16 (HPV 16)-immortalized human keratinocyte cell lines (HPK) were shown to have retained the ability for differentiation after subcutaneous injection into nude mice. These properties were maintained even at late passage. HPK cells gave rise to transiently growing cysts which exhibited an epitheliumlike architecture. Moreover, differentiation-specific markers such as cytokeratin 10, involucrin, and filaggrin were shown to be expressed in an ordered succession. RNA-RNA in situ hybridization revealed heterogeneous and low levels of HPV 16 E6-E7 RNA in the basal layer of the cysts. In contrast, in progressively growing tumors induced by HPK cells containing an activated ras oncogene (EJ-ras) or in tumors induced by the cervical carcinoma cell line CaSki, high levels of E6-E7-specific RNA could be detected. Irrespective of the growth potential of these cell lines in nude mice, viral transcription was always more evident in the basal layer and in proliferatively active cells rather than in differentiated cells. This contrasts with viral gene expression in HPV 16 positive low-grade cervical dysplasia, in which abundant viral transcriptional activity was mapped to the upper third of the epithelium. It is suggested that the physical state of the viral DNA, i.e., integrated viral DNA in the cell lines as opposed to extrachromosomal DNA in low-grade cervical dysplasia, may influence viral gene regulation.

Animals↗

PubMed1989

Molecular cloning and regulatory analysis of the arylsulfatase structural gene of Neurospora crassa.

The ars-1+ gene of Neurospora crassa encodes the enzyme arylsulfatase. ars-1+ is in a group of highly regulated sulfur-related structural genes that are expressed under conditions of sulfur limitation and are under coordinate control of the cys-3+ and scon+ regulatory genes. The ars-1+ gene was cloned by chromosome walking from the qa gene cluster, using a lambda library. Cotransformation of an N. crassa ars-1 mutant with the isolated lambda clones and the benomyl resistance gene, followed by assay for arylsulfatase activity, was used to screen for the ars-1+ gene. Further confirmation that the cloned segment mapped to the ars-1+ locus was obtained by restriction-fragment-length polymorphism analysis. Northern (RNA) blot analysis showed that the ars-1+ gene was transcribed to give an mRNA of 2.3 kilobases. In wild-type cells, the ars-1+ transcript was abundant under sulfur-derepressing conditions but absent under repressing conditions. Time course analysis showed that the appearance of ars-1+ message in sulfur-derepressed cultures paralleled the appearance of arylsulfatase enzyme activity. In addition, transcription of ars-1+ was detected only under derepressing conditions in a nuclear transcription assay. In a cys-3 regulatory mutant that was unable to synthesize arylsulfatase (or other sulfur-controlled enzymes), there was no ars-1+ transcript under repressing or derepressing conditions. In a temperature-sensitive cys-3 mutant, the ars-1+ transcript was present only at the permissive growth temperature and under sulfur derepression. A negative regulatory mutant, sconc, displayed both constitutive expression of arylsulfatase enzyme activity and content of ars-1+ message.

Arylsulfatases↗

PubMed1994

Type IIx myosin heavy chain transcripts are expressed in type IIb fibers of human skeletal muscle.

Several members of the sarcomeric myosin heavy chain (MHC) gene family have been mapped in the human genome but many of them have not yet been identified. In this study we report the identification of two human skeletal MHC genes as fast IIa and IIx MHC based on pattern of expression and sequence homology with the corresponding rat genes in the 3'-translated and untranslated regions. The distribution of these two gene products as well as that of the beta/slow MHC gene was analyzed in human skeletal muscles by in situ hybridization. The distribution of beta/slow, IIa, and IIx MHC transcripts defines three major muscle fiber types expressing a single MHC mRNA, i.e., either beta/slow, IIa, or IIx MHC mRNA, and two populations of hybrid fibers coexpressing beta/slow with IIa or IIa with IIx MHC mRNA. Fiber typing by ATPase histochemistry shows that IIa MHC transcripts are more abundant in histochemical type IIa fibers, whereas IIx MHC transcripts are more abundant in histochemical type IIb fibers.

Adolescent↗

PubMed1997

Ig D(H) gene segment transcription and rearrangement before surface expression of the pan-B-cell marker CD19 in normal human bone marrow.

The onset of IgH transcription and rearrangement is a defining characteristic of the progenitor population in which B-lineage commitment occurs. These features were used to better define the earliest stage of B-cell commitment in humans and to determine if these stages differ as a function of human ontogeny. Fetal and adult bone marrow mononuclear cells were sorted into B-lineage subpopulations on the basis of surface expression of the stem cell marker CD34, the pan-B-cell marker CD19, and IgM and analyzed for transcription and rearrangement of the IgH locus. The locus was found to be transcriptionally active before surface expression of CD19, as indicated by the presence of germline I mu, C mu, and D(H)Q52 transcripts in the CD34+ CD19- subpopulation. Transcripts from IgH alleles that had undergone DJC mu rearrangements were also detected in the CD34+ CD19- subpopulation. Within this subpopulation, low levels of DXP-containing DJC mu transcripts were detected in both fetal and adult cells. Although D(H)Q52 DJC mu transcripts were abundant in fetal CD34+ CD19- cells, they were not detected in cells of the same phenotype derived from adult bone marrow. In both fetus and adult, V(H)3-and V(H)6-containing VDJC mu transcripts were detected only in the CD19+ subpopulations. These data indicate that transcription of D(H)Q52-J(H) and DXP-J(H) rearrangements differs during fetal and adult B lymphopoiesis. Moreover, in both fetus and adult, transcription of unrearranged components of the IgH locus and DJ rearrangements can proceed before the surface expression of CD19.

Adult↗

PubMed1989

Mouse homeo-genes within a subfamily, Hox-1.4, -2.6 and -5.1, display similar anteroposterior domains of expression in the embryo, but show stage- and tissue-dependent differences in their regulation.

By use of in situ hybridization experiments on mouse embryo sections, we compare the transcript patterns of three homeo-genes from the Hox-1.4 subfamily (Hox-1.4, -2.6 and -5.1). Genes within a subfamily are true homologues, present in the genome as a result of duplication of an ancestral homeo-gene cluster. We show that Hox-1.4, -2.6 and -5.1 are similar, although apparently not identical, in the limits of their transcript domains along the anteroposterior axis. Within the prevertebral column of the 12 1/2 day embryo, for example, the anterior boundary of transcripts for each of the three genes was most obvious at the junction of the first and second prevertebrae. Similarly, all three genes showed an anterior boundary of transcripts within the central nervous system that was located in the mid-myelencephalon of the hindbrain. Both in the prevertebral column and hindbrain, however, Hox-2.6 and Hox-5.1 transcripts extended slightly anterior to the anteriormost limits detected for Hox-1.4. In spite of close similarities in the positions of their transcript domains, Hox-1.4, -2.6 and -5.1 displayed striking stage- and tissue-dependent differences in the relative abundance of their transcripts. For example, Hox-5.1 transcripts were abundant within mesoderm and ectoderm of early stages (8 1/2 and 9 1/2 days), yet were detected only weakly in mesodermal components of the lung and stomach at 10 1/2 days, and were apparently absent from these tissues at 12 1/2 days. In contrast, Hox-1.4 and Hox-2.6 transcripts were relatively weakly detected at 8 1/2 and 9 1/2 days, but were abundant within the lung and stomach at 12 1/2 days. Our findings suggest, but do not prove, that genes within the Hox-1.4 subfamily might be coordinately regulated in their expression. We discuss the patterns of mouse homeo-gene expression now observed in terms of models originally devised for Drosophila. We also propose how our new findings may help to explain any selective advantage to the vertebrates of homeo-gene duplication to form subfamilies.

Animals↗

PubMed2002

Differential expression and function of Arabidopsis thaliana NHX Na+/H+ antiporters in the salt stress response.

The Arabidopsis thaliana vacuolar Na+/H+ antiporter AtNHX1 is a salt tolerance determinant. Predicted amino acid sequence similarity, protein topology and the presence of functional domains conserved in AtNHX1 and prototypical mammalian NHE Na+/H+ exchangers led to the identification of five additional AtNHX genes (AtNHX2-6). The AtNHX1 and AtNHX2 mRNAs are the most prevalent transcripts among this family of genes in seedling shoots and roots. A lower-abundance AtNHX5 mRNA is present in both shoots and roots, whereas AtNHX3 transcript is expressed predominantly in roots. AtNHX4 and AtNHX6 mRNAs were detected only by RT-PCR. AtNHX1, 2 or 5 suppress, with differential efficacy, the Na+/Li+-sensitive phenotype of a yeast mutant that is deficient in the endosomal/vacuolar Na+/H+ antiporter ScNHX1. Ion accumulation data indicate that these AtNHX proteins function to facilitate Na+ ion compartmentalization and maintain intracellular K+ status. Seedling steady-state mRNA levels of AtNHX1 and AtNHX2 increase similarly after treatment with NaCl, an equi-osmolar concentration of sorbitol, or ABA, whereas AtNHX5 transcript abundance increases only in response to salt treatment. Hyper-osmotic up-regulation of AtNHX1, 2 or 5 expression is not dependent on the SOS pathway that controls ion homeostasis. However, steady-state AtNHX1, 2 and 5 transcript abundance is greater in sos1, sos2 and sos3 plants growing in medium that is not supplemented with sorbitol or NaCl, providing evidence that transcription of these genes is negatively affected by the SOS pathway in the absence of stress. AtNHX1 and AtNHX2 transcripts accumulate in response to ABA but not to NaCl in the aba2-1, mutant indicating that the osmotic responsiveness of these genes is ABA-dependent. An as yet undefined stress signal pathway that is ABA- and SOS-independent apparently controls transcriptional up-regulation of AtNHX5 expression by hyper-saline shock. Similar to AtNHX1, AtNHX2 is localized to the tonoplast of plant cells. Together, these results implicate AtNHX2 and 5, together with AtNHX1, as salt tolerance determinants, and indicate that AtNHX2 has a major function in vacuolar compartmentalization of Na+.

Amino Acid Sequence↗