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PubMed1991

Developmental regulation of gap junction gene expression during mouse embryonic development.

The expression of products from three different gap junction genes (alpha 1, beta 1 and beta 2) was studied in pre- and postimplantation mouse embryos, during organogenesis, during differentiation of F9 teratocarcinoma cells, and in cultured embryonic stem (ES) cells. In this analysis, the following results were obtained. 1) Pre- and postimplantation mouse embryos. The alpha 1 transcript was the earliest gap junction RNA detected (in the 4 cell stage embryo) and its abundance increased significantly throughout subsequent development. 2) Organogenesis. Evidence was obtained for developmental expression of these three different gap junction genes during early embryogenesis and throughout the late stages of organogenesis. The expression patterns for these genes may be related to differences in gap junctional communication requirements for fetal organ development versus neonatal and adult organ function, or the utilization of different genes by different cell types during organogenesis. 3) During the differentiation of F9 cells in culture, expression of these three genes was modulated. Thus, this is the first evidence for modulation of gap junction gene expression during the differentiation of a single cell type in culture. 4) In an ES cell culture line, alpha 1 was the only gap junction gene product detected. This is consistent with the findings of alpha 1 expression in the embryonic inner cell mass region and in undifferentiated teratocarcinoma cells.

Amino Acid Sequence↗
PubMed2026

Single-cell profiling decodes patagium development in gliding mammal.

The gliding patagium represents a key adaptation for mammalian flight, but its cellular development remains unexplored. Using single-nucleus RNA sequencing of embryonic flying squirrel patagium and dorsal skin, we construct a single-cell atlas of patagium development and identify two distinct fibroblast subpopulations (Fp2 and Fr) highly enriched in the patagium. These fibroblasts are characterized by the patagium upregulation of Wnt5a, Fgf7, and Fgf10, and are associated with patagium morphogenesis through dermal-epidermal putative communication interactions between dermal fibroblasts (Fp2 and Fr) and epithelial basal keratinocytes. Specifically, Fp2 fibroblasts are potentially involved in distal dermal condensation and epithelial thickening together with elevated Wnt5a expression, while both Fp2 and Fr fibroblasts could play a role in epithelial polarization and thickening through Fgf7 and Fgf10, as suggested by ex vivo assays. Our data suggest that gliding patagium development results from the co-option of conserved WNT and FGF signaling pathways within a specialized fibroblast-epithelial context, illustrating how modifications of conserved developmental programs give rise to derived morphological traits.

Animals↗
PubMed1985

Tissue specific expression and developmental regulation of two genes coding for rat fatty acid binding proteins.

We have examined the tissue distribution and developmental regulation of two low molecular weight cytosolic fatty acid binding proteins. Based on their initial site of isolation, they have been referred to as liver and intestinal fatty acid binding proteins (FABP). Cloned cDNAs were used to probe blots of RNAs extracted from a wide variety of adult rat tissues as well as small intestine and liver RNA obtained from fetal, suckling, and weaning animals. The highest concentrations of "liver" FABP mRNA were found in small intestine and liver. "Intestinal" FABP mRNA is most abundant in small bowel RNA while only trace amounts were encountered in liver. Both mRNAs were detectable in stomach, colon, pancreas, spleen, lung, heart, testes, adrenal, and brain RNA at 1-8% the concentrations observed in small intestine. Accumulation of both mRNAs in the small intestinal epithelium increases during development. The mRNAs are first detectable between the 19th and 21st day of gestation. They undergo a coordinated 3-4-fold increase in concentration within the first 24 h after birth. Thereafter, gut levels of intestinal FABP mRNA remain constant during the suckling period while liver FABP mRNA increases an additional 2-fold. Liver FABP mRNA levels are also induced in hepatocytes during the first postnatal day but subsequently do not change during the suckling and weaning phase, despite marked alterations in hepatic fatty acid metabolism. These observations support the concept that the major role of these proteins is to facilitate the entry of lipids into cells and/or their subsequent intracellular transport and compartmentalization. The data also raise questions about the identity of extragastrointestinal FABPs.

Aging↗
PubMed2025

A Balanced Inversion Polymorphism Exhibits a Dominance Reversal at the Gene Expression Level that Depends on Developmental Context.

How genetic variance for fitness is maintained is incompletely understood. Mutation-selection balance and single-locus overdominance cannot account for the large variance observed. Recent work suggests that antagonistic balancing selection, favoring different alleles in different contexts and involving beneficial dominance reversals, might contribute to maintaining fitness variance. However, while this mechanism is plausible, evidence for dominance reversals remains scarce. Here, we study how In(3R)Payne, a balanced inversion polymorphism in Drosophila melanogaster, affects gene expression and chromatin accessibility by using RNA-seq and ATAC-seq (assay for transposase-accessible chromatin with sequencing). We find that, in embryos, the inverted (INV) arrangement tends to have dominant effects, while the standard (STD) arrangement behaves like a recessive Mendelian allele. Yet, in wing discs, this pattern is reversed: STD has mostly dominant effects, whereas INV behaves recessively. Since this shift in the dominance of the INV "allele" between developmental contexts affects the expression of suites of genes in a concerted manner, it might be mediated by a dominance modifier, for example, a transcription factor. In favor of this idea, 25% of the differentially expressed genes between INV and STD encode transcription factors. Interestingly, while only four differentially expressed genes are shared between embryos and wing discs, one of them is HP1c, a chromatin-binding protein and major transcriptional regulator, and thus a promising candidate for mediating the context-dependent change in dominance. Although the relationship between these patterns and fitness is presently unknown, our observations are consistent with a potential role of reversals (or, more generally, shifts) of dominance in maintaining inversion polymorphism.

Animals↗
PubMed1992

Circadian and developmental regulation of Oct-2 gene expression in the suprachiasmatic nuclei.

Oct-2 is a transcriptional activating factor that is expressed in the suprachiasmatic nuclei (SCN), the site of a biological clock. We examined in rats whether Oct-2 gene expression is regulated by the circadian pacemaker or by light using quantitative in situ hybridization. The ontogeny of Oct-2 gene expression in the SCN was also studied. Oct-2 mRNA levels remained constant throughout the circadian cycle. In contrast to c-fos mRNA levels which are acutely induced by acute light exposure at night, Oct-2 mRNA levels were not increased by light exposure at night. At gestational day 18, the first age the SCN are anatomically distinct, a prominent Oct-2 hybridization signal was present in the SCN. Our results suggest that Oct-2 is constitutively expressed in the SCN and is present from the time the SCN are discernible as discrete nuclei in fetal brain.

Animals↗
PubMed1986

Developmentally regulated expression of Drosophila chorion genes introduced at diverse chromosomal positions.

Drosophila chorion genes are organized into two clusters that are selectively amplified in the ovarian follicle cells. During oogenesis the transcription of individual genes is temporally regulated, resulting in distinct, stage-specific profiles of chorion mRNA accumulation. P element-mediated gene transfer was used to study the regulation of genes encoding the major chorion proteins s15-1 and s38-1. Transformed chorion genes integrated at diverse chromosomal locations exhibited proper tissue-specific and stage-specific expression, despite separation from the gene clusters. Qualitatively normal expression was not dependent on the ability of the inserted DNA to undergo amplification. However, chromosome position quantitatively influenced the RNA produced by the transformed genes. The level of RNA per gene copy produced by individual transformed genes varied approximately tenfold, after correction for differences in gene dosage due to the amplification of some inserted sequences. Transformation experiments with an s38-1-lacZ fusion gene demonstrated that cis-regulatory sequences sufficient for the stage-specific program of s38-1 expression were confined to a 1.3 X 10(3) base-pair segment between -748 and +573 relative to the s38-1 initiation site. Finally, egg chamber-specific amplification was induced at the site of two s38-1 insertions, suggesting that an amplification control element resides near this gene.

Animals↗
PubMed1986

Developmentally regulated rearrangement and expression of genes encoding the T cell receptor-T3 complex.

Human leukemic cells corresponding to the earliest identifiable stages of intrathymic T cell differentiation lack cell surface expression of the T cell receptor(TCR alpha/beta)-T3 complex but transcribe TCR beta mRNA from either germ-line configuration (1/13) or partially (DJ) or fully (VDJ) rearranged (12/13) genes. These cells do not produce TCR alpha mRNA, but do contain T3 delta and T3 epsilon mRNA and accumulate T3 polypeptides, primarily in the perinuclear envelope. Equivalent normal T cells isolated from thymus have a predominantly germ-line configuration of TCR beta but contain intracellular T3 proteins. T3 gene expression is therefore a very early event in T cell differentiation. TCR alpha chain production appears to be the limiting maturation-linked event in the transport, assembly, and cell surface membrane insertion of the TCR alpha/beta-T3 complex.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1991

Developmental regulation of creatine kinase gene expression by myogenic factors in embryonic mouse and chick skeletal muscle.

The B isoform of creatine kinase (BCK), which is expressed at a high level in embryonic neural tissues, is also expressed abundantly in developing striated muscle and is an early marker for skeletal myogenesis. Using isoform-specific 35S-labeled antisense cRNA probes for in situ hybridization, we have detected BCK mRNAs in embryonic mouse and chick myotomes, the first skeletal muscle masses to form in developing embryos. These transcripts are detectable as soon as myotomes are morphologically distinguishable. BCK is expressed at high levels in both skeletal and cardiac muscle in mouse and chick embryos. In the mouse, BCK transcript levels fall of rapidly in striated muscle shortly after the onset of MCK gene expression. The M isoform of creatine kinase (MCK), the striated muscle-specific isoform, is expressed later than BCK. In the mouse, BCK transcripts are expressed in myotomes at 8.5 days post coitum (p.c.), but MCK transcripts are not detected before 13 days p.c. In the chick, BCK mRNAs are present at Hamburger-Hamilton stage 13, but MCK mRNAs are not detected before stage 19. We have compared the patterns of expression of the CK genes with those of myogenic differentiation factor genes, which are thought to regulate skeletal muscle-specific gene expression. In the chick, both CMD1, first detected at stage 13, and myogenin, first detected at stage 15, are present prior to MCK, which begins to be expressed at stage 19. Unlike the mouse embryo, CMD1, the chick homologue of MyoD1, is expressed before chick myogenin. In the mouse, myogenin, first detected at 8.5 days p.c., is expressed at the same time as BCK in myotomes. Both myogenin and MyoD1, which begins to be detected two days later than myogenin, are expressed at least two days before MCK. It has been proposed that the myogenic factors, MyoD1 and myogenin, directly regulate MCK gene expression in the mouse by binding to its enhancer. However, our results show that MCK transcripts are not detected until well after MyoD1 and myogenin mRNAs are expressed, suggesting that these factors by themselves are not sufficient to initiate MCK gene expression.

Animals↗
PubMed1989

The tissue-specific expression and developmental regulation of two nuclear genes encoding rat mitochondrial proteins. Medium chain acyl-CoA dehydrogenase and mitochondrial malate dehydrogenase.

To study the regulation of nuclear genes which encode mitochondrial enzymes involved in oxidative metabolism, absolute levels of mRNA encoding rat medium chain acyl-CoA dehydrogenase (MCAD) and rat mitochondrial malate dehydrogenase (mMDH) were determined in developing and adult male rat tissues. MCAD mRNA is expressed in a variety of adult male tissues with highest steady state levels in heart, adrenal, and skeletal muscle and lowest levels in brain, lung, and testes. In comparison, steady state levels of mMDH mRNA in adult male rat tissues were similar to those of MCAD mRNA in heart, small intestine, adrenal, and skeletal muscle but markedly different in brain, stomach, and testes. Thus, the steady-state levels of MCAD and mMDH mRNA are highest in adult tissues with high energy requirements. Dot blot analysis of RNA prepared from late fetal, suckling, and weaning rat heart, liver, and brain demonstrated the presence of MCAD and mMDH mRNA during the fetal period in all three tissues. Both MCAD and mMDH mRNA levels increased 2-2.5-fold at birth followed by a decline during the first postnatal week in heart and liver. The patterns of accumulation of these mRNAs in heart and liver during the weaning and early adult periods were also similar, although the absolute levels were significantly different. Brain MCAD mRNA levels were consistently low (less than 0.1 pg/micrograms total cellular RNA) throughout the developmental stages. However, brain mMDH mRNA levels exhibited a marked increase during the weaning period, reaching a peak concentration which is higher than the level of mMDH mRNA in heart and liver at any point during development. These results indicate that the level of expression of the nuclear genes encoding MCAD and mMDH is tissue-specific and developmentally regulated. The patterns of MCAD and mMDH mRNA accumulation parallel the changes in energy metabolism which occur during development and among adult tissues.

Acyl-CoA Dehydrogenase↗
PubMed1990

Oocyte-specific expression of mouse Zp-2: developmental regulation of the zona pellucida genes.

The zona pellucida surrounds all mammalian oocytes and plays a vital role at fertilization and in early development. The genes that code for two of the mouse zona proteins (ZP2 and ZP3) represent a developmentally regulated set of genes whose expression serves as markers of mouse oocyte growth and differentiation. We previously characterized the single-copy Zp-3 gene and showed that its expression is oocyte specific and restricted to a narrow window of oocyte development. We now define the Zp-2 gene transcript and show that it is coordinately expressed with Zp-3 only during the 2-week growth phase of oogenesis that occurs prior to ovulation. Like Zp-3, the expression of Zp-2 is restricted to oocytes, and, although not detectable in resting oocytes, both ZP2 and ZP3 transcripts accumulate to become very abundant messengers in 50-microns-diameter oocytes. Ovulated eggs contain ZP2 and ZP3 transcripts which are 200 nucleotides shorter than those found in growing oocytes and have an abundance of less than 5% of the peak levels. In an attempt to understand the molecular details associated with the developmentally regulated, tissue-specific gene expression of the zona genes, the Zp-2 genetic locus has been characterized and its 5' flanking sequences have been compared with those of Zp-3. Both genes contain three short (8- to 12-base-pair) DNA sequences of 80 to 88% identity located within 250 base pairs of their transcription start sites.

Amino Acid Sequence↗
PubMed1985

Developmentally regulated expression of a chicken muscle-specific gene in stably transfected rat myogenic cells.

To test the evolutionary conservation of DNA sequences specifying the developmentally regulated expression of the skeletal muscle actin gene, a recombinant plasmid containing the chicken skeletal muscle actin gene was introduced into rat myogenic cells. In a significant number of isolated clones, the accumulation of chicken actin mRNA increased greatly during differentiation. To test the expression in myogenic cells of a gene that is normally expressed during terminal differentiation of another tissue, rat myogenic cells were transfected with a mouse/human beta-globin chimeric gene. A decrease by a factor of 2-3 in the amount of globin mRNA during differentiation was observed in most clones in which the gene was expressed. The results indicate the conservation of the muscle-specific regulatory DNA sequences for more than 300 Myr.

Actins↗
PubMed1987

Developmental pattern of the expression of malonyl-CoA decarboxylase gene and the production of unique lipids in the goose uropygial glands.

The abundant fatty acid synthase in the uropygial gland of goose generates multimethyl-branched fatty acids as the major product because of the unique presence of the cytoplasmic malonyl-CoA decarboxylase which assures that only methylmalonyl-CoA is available to the synthase. If this conclusion is valid, the developmental pattern of expression of the gene for this tissue-specific decarboxylase should correlate with the appearance of other lipogenic enzymes and the production of the unique lipids. To test this possibility the levels of the decarboxylase, acetyl-CoA carboxylase, and fatty acid synthase in the gland of the embryonic and neonatal goose were measured by immunodiffusion and immunoblot assays for the proteins as well as the enzyme assays for the catalytic activities. Malonyl-CoA decarboxylase appeared several days before hatching as did the other two lipogenic enzymes and reached half-maximal levels by hatching. The levels of expression of the malonyl-CoA decarboxylase gene and cytoplasmic actin gene, which is not expected to be developmentally regulated, were measured by dot-blot analysis using cloned cDNA for the two proteins. The decarboxylase transcripts appeared 4 days prior to hatching and reached maximal levels by hatching, whereas the levels of cytoplasmic actin gene transcripts showed very little change. The appearance of oil droplets in the glands was clearly seen soon after hatching. These results show that malonyl-CoA decarboxylase gene expression is developmentally regulated in a manner consistent with its proposed role in the synthesis of the unique lipids of the uropygial gland.

Aging↗
PubMed1992

C/EBP and c-JUN proteins activate the proximal enhancer of the developmentally regulated alpha-fetoprotein gene.

The expression of the alpha-fetoprotein (AFP) gene is developmentally regulated. Active transcription of this gene depends on a proximal enhancer sequence located between positions D-203 bp and -81 bp, upstream the initiation site. This enhancer contains several putative binding sites for transcription factors. By transfection experiments, we showed that the enhancer activity can be driven by interactions with two regulatory factors, namely C/EBP and c-JUN.

Base Sequence↗
PubMed1985

Expression of the Caenorhabditis elegans collagen genes col-1 and col-2 is developmentally regulated.

The total collagen gene expression as well as the specific expression of two sequenced Caenorhabditis elegans collagen genes, col-1 and col-2, has been investigated. Northern blots of RNA isolated from animals at different developmental stages were probed under conditions that allow cross-hybridization of all collagen sequences. The majority of hybridization is to transcripts of 1.1-1.4 kilobases (kb) in length, with weak hybridization to some larger transcripts. Different size patterns, within the 1.1-1.4-kb ranges, are seen in RNAs from different developmental stages. Gene-specific probes were produced from the C. elegans collagen genes col-1 and col-2, and each was shown to hybridize to a single size transcript in the 1.1-1.4-kb region. The col-1 transcript was found in all the developmental stages examined, but its abundance varied between stages. The col-2 transcript was detected only in a single developmental stage, during formation of the dauer larvae. The 5' and the 3' ends of the col-1 and col-2 transcripts were determined by S1 nuclease digestion experiments. Both genes have the common "TATA" and "CAAT" box sequences preceding the 5' end of their transcripts and there is strong sequence homology in their 5' untranslated regions. Multiple copies of an eight-nucleotide repeat sequence were found upstream from both col-1 and col-2.

Animals↗
PubMed1986

Tissue-specific and developmentally regulated expression of a chimeric actin-globin gene in transgenic mice.

A chimeric plasmid containing about 2/3 of the rat skeletal muscle actin gene plus 730 base pairs of its 5' flanking sequences fused to the 3' end of a human embryonic globin gene (D. Melloul, B. Aloni, J. Calvo, D. Yaffe, and U. Nudel, EMBO J. 3:983-990, 1984) was inserted into mice by microinjection into fertilized eggs. Eleven transgenic mice carrying the chimeric gene with or without plasmid pBR322 DNA sequences were identified. The majority of these mice transmitted the injected DNA to about 50% of their progeny. However, in transgenic mouse CV1, transmission to progeny was associated with amplification or deletion of the injected DNA sequences, while in transgenic mouse CV4 transmission was distorted, probably as a result of insertional mutagenesis. Tissue-specific expression was dependent on the removal of the vector DNA sequences from the chimeric gene sequences prior to microinjection. None of the transgenic mice carrying the chimeric gene together with plasmid pBR322 sequences expressed the introduced gene in striated muscles. In contrast, the six transgenic mice carrying the chimeric gene sequences alone expressed the inserted gene specifically in skeletal and cardiac muscles. Moreover, expression of the chimeric gene was not only tissue specific, but also developmentally regulated. Similar to the endogenous skeletal muscle actin gene, the chimeric gene was expressed at a relatively high level in cardiac muscle of neonatal mice and at a significantly lower level in adult cardiac muscle. These results indicate that the injected DNA included sufficient cis-acting control elements for its tissue-specific and developmentally regulated expression in transgenic mice.

Actins↗
PubMed2026

Two Paralogues as They Like It: Conserved and Divergent Evolution of Vertebrate Gcm Genes.

Gcm1 and Gcm2 are paralogous transcription factors in vertebrates that play key roles in the development of pharyngeal-derived epithelia, yet their deployment across vertebrate lineages remains incompletely understood. While Gcm2 shows deeply conserved pharyngeal expression across gnathostomes, Gcm1 has been mainly characterized in mammals, where it exhibits broader expression patterns. How Gcm1 is deployed in non-mammalian vertebrates has remained unexplored. Here, we performed a comparative analysis of Gcm1 expression in cartilaginous fishes, non-teleost actinopterygians, and amphibians. RNA in situ hybridization revealed conserved Gcm1 expression in gill epithelia across these taxa. Parallel analyses showed that Gcm2 is also expressed in gill epithelia, with overlapping but distinct spatial patterns. In addition, Gcm1 showed lineage-specific expression in bichir embryos, including strong expression in external gills and scattered epithelial cells in the yolk-sac membrane. In the external gills, Gcm1-positive cells possess vacuole-like cytoplasmic structures, suggesting a previously unrecognized epithelial cell population. Together, our findings indicate that Gcm1 and Gcm2 share ancestral expression in pharyngeal epithelia but have followed distinct evolutionary trajectories, with Gcm1 exhibiting greater lineage-specific diversification.

Animals↗
PubMed2026

Developmental analysis of the cone photoreceptor-less little skate retina reveals distinct Onecut1 isoforms.

The retinal development of elasmobranchs, the subclass comprising sharks, skates, and rays, remains poorly understood. This group is diverse in retinal phenotype, with many sharks and rays possessing rods together with one or more cone types. In contrast, the little skate (Leucoraja erinacea) has only a single rod photoreceptor type, which has been reported to exhibit some physiological and anatomical properties associated with cones. To investigate how this unusual photoreceptor system develops, we first identified an embryonic stage of early photoreceptor formation based on otx2 expression. We then developed a retinal electroporation approach to test whether a onecut1-dependent cone-associated reporter could be activated in the embryonic skate retina. Activation of this reporter was not detected, indicating that the corresponding enhancer is not robustly active under the conditions tested. To assess developmental changes in gene expression, we generated bulk RNA-seq datasets from embryonic, hatchling, and adult retinas. These analyses showed strong embryonic expression of onecut1, increasing expression of rod-associated genes through development, and pseudogenization or loss of multiple cone-enriched genes. We further identified a developmentally regulated onecut1 splice isoform containing an additional 48 amino acid sequence between the CUT and homeodomain DNA-binding domains. This spacer-containing isoform, termed LSOC1X2, was most abundant in the embryonic retina. To test whether LSOC1X2 retained regulatory activity, we assayed it in a mouse retinal reporter system. Both skate Onecut1 isoforms activated the ThrbCRM1 reporter in this heterologous context. Together, these findings identify a novel, developmentally regulated retinal onecut1 isoform in the little skate and establish it as a candidate regulator for future studies of photoreceptor development in this species and its elasmobranch relatives.

Animals↗