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PubMed2001

Early growth response gene 1 stimulates development of hematopoietic progenitor cells along the macrophage lineage at the expense of the granulocyte and erythroid lineages.

Using a variety of differentiation-inducible myeloid cell lines, we previously showed that the zinc-finger transcription factor early growth response gene 1 (Egr-1) is a positive modulator of macrophage differentiation and negatively regulates granulocytic differentiation. In this study, high-efficiency retroviral transduction was used to ectopically express Egr-1 in myeloid-enriched or stem cell-enriched bone marrow cultures to explore its effect on the development of hematopoietic progenitors in vitro and in lethally irradiated mice. It was found that ectopic Egr-1 expression in normal hematopoietic progenitors stimulates development along the macrophage lineage at the expense of development along the granulocyte or erythroid lineages, regardless of the cytokine used. Moreover, Egr-1 accelerated macrophage development by suppressing the proliferative phase of the growth-to-macrophage developmental program. The remarkable ability of Egr-1 to dictate macrophage development at the expense of development along other lineages resulted in failure of Egr-1-infected hematopoietic progenitors to repopulate the bone marrow and spleen, and thereby prevent death, in lethally irradiated mice. These observations further highlight the role Egr-1 plays in monocytic differentiation and growth suppression.

Animals↗

PubMed2001

Identical mutations in RAG1 or RAG2 genes leading to defective V(D)J recombinase activity can cause either T-B-severe combined immune deficiency or Omenn syndrome.

Omenn syndrome (OS) is an inherited disorder characterized by an absence of circulating B cells and an infiltration of the skin and the intestine by activated oligoclonal T lymphocytes, indicating that a profound defect in the lymphoid developmental program could be accountable for this condition. Inherited mutations in either the recombination activating genes RAG1 or RAG2, resulting in partial V(D)J recombinase activity, were shown to be responsible for OS. This study reports on the characterization of new RAG1/2 gene mutations in a series of 9 patients with OS. Given the occurrence of the same mutations in patients with T-B-severe combined immune deficiency or OS on 3 separate occasions, the proposal is made that an additional factor may be required in certain circumstances for the development of the Omenn phenotype. The nature of this factor is discussed.

DNA Nucleotidyltransferases↗

PubMed2001

Pro-B-cell to pre-B-cell development in B-lineage acute lymphoblastic leukemia expressing the MLL/AF4 fusion protein.

The most common chromosomal abnormality of infant acute lymphoblastic leukemia (ALL) is the t(4;11)(q21;q23) that gives rise to the MLL/AF4 fusion gene. Leukemic blasts expressing MLL/AF4 are arrested at an early progenitor stage with lymphoid or monocytoid characteristics. A novel B-lineage ALL cell line termed B-lineage-3 (BLIN-3) requiring human bone marrow (BM) stromal cell contact and interleukin-7 (IL-7) for optimal proliferation has been established. BLIN-3 cells have a CD19(+)/CD10(-) phenotype typical of infant ALL, and they harbor the t(4;11)(q21;q23) chromosomal translocation. Reverse transcription-polymerase chain reaction and Western blot analysis confirmed the presence of the MLL/AF4 fusion mRNA and protein in BLIN-3. Initial BLIN-3 cultures had a pro-B cell phenotype and did not express cytoplasmic or surface mu heavy chain. After approximately 5 months in culture on BM stromal cells plus IL-7, BLIN-3 sublines emerged expressing mu heavy chain and VpreB on the cell surfaces (ie, pre-B-cell receptor [BCR](+)). BLIN-3 cells expressing pre-BCR had the t(4;11)(q21;q23) translocation and expressed the MLL/AF4 fusion protein. Cross-linking the BLIN-3 pre-BCR led to enhanced cell proliferation, demonstrating that BLIN-3 expressed a functional pre-BCR. Increased acquisition of surface pre-BCR in BLIN-3 sublines was associated with loss of DJ rearrangements and the appearance of VDJ rearrangements. These results indicate that expression of the MLL/AF4 fusion protein is compatible with BM stromal cell and cytokine dependency, functional immunoglobulin gene segment rearrangement, and subsequent expression of a potentially diverse antigen receptor repertoire. Thus, the expression of MLL/AF4 is compatible with the normal developmental program of human B-lineage cells.

Antibodies, Monoclonal↗

PubMed2003

Growth factor signaling in lung morphogenetic centers: automaticity, stereotypy and symmetry.

Lung morphogenesis is stereotypic, both for lobation and for the first several generations of airways, implying mechanistic control by a well conserved, genetically hardwired developmental program. This program is not only directed by transcriptional factors and peptide growth factor signaling, but also co-opts and is modulated by physical forces. Peptide growth factors signal within repeating epithelial-mesenchymal temporospatial patterns that constitute morphogenetic centers, automatically directing millions of repetitive events during both stereotypic branching and nonstereotypic branching as well as alveolar surface expansion phases of lung development. Transduction of peptide growth factor signaling within these centers is finely regulated at multiple levels. These may include ligand expression, proteolytic activation of latent ligand, ligand bioavailability, ligand binding proteins and receptor affinity and presentation, receptor complex assembly and kinase activation, phosphorylation and activation of adapter and messenger protein complexes as well as downstream events and cross-talk both inside and outside the nucleus. Herein we review the critical Sonic Hedgehog, Fibroblast Growth Factor, Bone Morphogenetic Protein, Vascular Endothelial Growth Factor and Transforming Growth Factorbeta signaling pathways and propose how they may be functionally coordinated within compound, highly regulated morphogenetic gradients that drive first stereotypic and then non-stereotypic, automatically repetitive, symmetrical as well as asymmetrical branching events in the lung.

Aging↗

PubMed2004

Identification of Wnt responsive genes using a murine mammary epithelial cell line model system.

BACKGROUND: The Wnt/Wg pathway plays an important role in the developmental program of many cells and tissues in a variety of organisms. In addition, many Wnts and components of their downstream signaling pathways, such as beta-catenin and APC, have been implicated in tumorigenesis. Over the past years, several genes have been identified as Wnt responsive, including c-myc, siamois, and cyclin D1. RESULTS: In order to identify additional genes responsive to Wnt signaling that contribute to the transformed phenotype, we performed a cDNA subtractive hybridization screen between a mouse mammary epithelial cell line that overexpresses Wnt-1 (C57MG/Wnt-1) and the parental cell line (C57MG). The screen identified a total of 67 genes to be up-regulated in response to Wnt signaling. Of these 67 genes, the up-regulation of 62 was subsequently confirmed by Northern and dot blot analyses (and, for a subset, semi-quantitative PCR) of RNA isolated from C57MG cells subjected to (1) an independent Wnt-1 retroviral infection, and (2) co-culture with Wnt-1 expressing cells. Among the confirmed Wnt-1 responsive genes, we further characterized a mouse homolog of the human transcription factor Basic Transcription Element Binding protein 2 (BTEB2), Wnt-1 Responsive Cdc42 homolog (Wrch-1), and Wnt-1 Induced Secreted Protein (WISP-1). CONCLUSION: Several novel genes were identified in this screen, as well as others that have been shown previously to be regulated by Wnt signaling, such as connexin43. The results indicate that cDNA subtractive hybridization is a useful method for identifying genes involved in the process of Wnt-1-induced transformation.

Animals↗

PubMed2006

FLOWERING LOCUS C-dependent and -independent regulation of the circadian clock by the autonomous and vernalization pathways.

BACKGROUND: The circadian system drives pervasive biological rhythms in plants. Circadian clocks integrate endogenous timing information with environmental signals, in order to match rhythmic outputs to the local day/night cycle. Multiple signaling pathways affect the circadian system, in ways that are likely to be adaptively significant. Our previous studies of natural genetic variation in Arabidopsis thaliana accessions implicated FLOWERING LOCUS C (FLC) as a circadian-clock regulator. The MADS-box transcription factor FLC is best known as a regulator of flowering time. Its activity is regulated by many regulatory genes in the "autonomous" and vernalization-dependent flowering pathways. We tested whether these same pathways affect the circadian system. RESULTS: Genes in the autonomous flowering pathway, including FLC, were found to regulate circadian period in Arabidopsis. The mechanisms involved are similar, but not identical, to the control of flowering time. By mutant analyses, we demonstrate a graded effect of FLC expression upon circadian period. Related MADS-box genes had less effect on clock function. We also reveal an unexpected vernalization-dependent alteration of periodicity. CONCLUSION: This study has aided in the understanding of FLC's role in the clock, as it reveals that the network affecting circadian timing is partially overlapping with the floral-regulatory network. We also show a link between vernalization and circadian period. This finding may be of ecological relevance for developmental programming in other plant species.

Arabidopsis↗

PubMed2006

The PTI1-like kinase ZmPti1a from maize (Zea mays L.) co-localizes with callose at the plasma membrane of pollen and facilitates a competitive advantage to the male gametophyte.

BACKGROUND: The tomato kinase Pto confers resistance to bacterial speck disease caused by Pseudomonas syringae pv. tomato in a gene for gene manner. Upon recognition of specific avirulence factors the Pto kinase activates multiple signal transduction pathways culminating in induction of pathogen defense. The soluble cytoplasmic serine/threonine kinase Pti1 is one target of Pto phosphorylation and is involved in the hypersensitive response (HR) reaction. However, a clear role of Pti1 in plant pathogen resistance is uncertain. So far, no Pti1 homologues from monocotyledonous species have been studied. RESULTS: Here we report the identification and molecular analysis of four Pti1-like kinases from maize (ZmPti1a, -b, -c, -d). These kinase genes showed tissue-specific expression and their corresponding proteins were targeted to different cellular compartments. Sequence similarity, expression pattern and cellular localization of ZmPti1b suggested that this gene is a putative orthologue of Pti1 from tomato. In contrast, ZmPti1a was specifically expressed in pollen and sequestered to the plasma membrane, evidently owing to N-terminal modification by myristoylation and/or S-acylation. The ZmPti1a:GFP fusion protein was not evenly distributed at the pollen plasma membrane but accumulated as an annulus-like structure which co-localized with callose (1,3-beta-glucan) deposition. In addition, co-localization of ZmPti1a and callose was observed during stages of pollen mitosis I and pollen tube germination. Maize plants in which ZmPti1a expression was silenced by RNA interference (RNAi) produced pollen with decreased competitive ability. Hence, our data provide evidence that ZmPti1a plays an important part in a signalling pathway that accelerates pollen performance and male fitness. CONCLUSION: ZmPti1a from maize is involved in pollen-specific processes during the progamic phase of reproduction, probably in crucial signalling processes associated with regions of callose deposition. Pollen-sporophyte interactions and pathogen induced HR show certain similarities. For example, HR has been shown to be associated with cell wall reinforcement through callose deposition. Hence, it is hypothesized that Pti1 kinases from maize act as general components in evolutionary conserved signalling processes associated with callose, however during different developmental programs and in different tissue types.

Cell Membrane↗

PubMed2003

Neural stem cells and the regulation of adult neurogenesis.

Presumably, the 'hard-wired' neuronal circuitry of the adult brain dissuades addition of new neurons, which could potentially disrupt existing circuits. This is borne out by the fact that, in general, new neurons are not produced in the mature brain. However, recent studies have established that the adult brain does maintain discrete regions of neurogenesis from which new neurons migrate and become incorporated into the functional circuitry of the brain. These neurogenic zones appear to be vestiges of the original developmental program that initiates brain formation. The largest of these germinal regions in the adult brain is the subventricular zone (SVZ), which lines the lateral walls of the lateral ventricles. Neural stem cells produce neuroblasts that migrate from the SVZ along a discrete pathway, the rostral migratory stream, into the olfactory bulb where they form mature neurons involved in the sense of smell. The subgranular layer (SGL) of the hippocampal dentate gyrus is another neurogenic region; new SGL neurons migrate only a short distance and differentiate into hippocampal granule cells. Here, we discuss the surprising finding of neural stem cells in the adult brain and the molecular mechanisms that regulate adult neurogenesis.

Adrenal Cortex Hormones↗

PubMed2006

The homeobox transcription factor Even-skipped regulates acquisition of electrical properties in Drosophila neurons.

BACKGROUND: While developmental processes such as axon pathfinding and synapse formation have been characterized in detail, comparatively less is known of the intrinsic developmental mechanisms that regulate transcription of ion channel genes in embryonic neurons. Early decisions, including motoneuron axon targeting, are orchestrated by a cohort of transcription factors that act together in a combinatorial manner. These transcription factors include Even-skipped (Eve), islet and Lim3. The perdurance of these factors in late embryonic neurons is, however, indicative that they might also regulate additional aspects of neuron development, including the acquisition of electrical properties. RESULTS: To test the hypothesis that a combinatorial code transcription factor is also able to influence the acquisition of electrical properties in embryonic neurons we utilized the molecular genetics of Drosophila to manipulate the expression of Eve in identified motoneurons. We show that increasing expression of this transcription factor, in two Eve-positive motoneurons (aCC and RP2), is indeed sufficient to affect the electrical properties of these neurons in early first instar larvae. Specifically, we observed a decrease in both the fast K+ conductance (IKfast) and amplitude of quantal cholinergic synaptic input. We used charybdotoxin to pharmacologically separate the individual components of IKfast to show that increased Eve specifically down regulates the Slowpoke (a BK Ca2+-gated potassium channel), but not Shal, component of this current. Identification of target genes for Eve, using DNA adenine methyltransferase identification, revealed strong binding sites in slowpoke and nAcRalpha-96Aa (a nicotinic acetylcholine receptor subunit). Verification using real-time PCR shows that pan-neuronal expression of eve is sufficient to repress transcripts for both slo and nAcRalpha-96Aa. CONCLUSION: Taken together, our findings demonstrate, for the first time, that Eve is sufficient to regulate both voltage- and ligand-gated currents in motoneurons, extending its known repertoire of action beyond its already characterized role in axon guidance. Our data are also consistent with a common developmental program that utilizes a defined set of transcription factors to determine both morphological and functional neuronal properties.

Acetylcholine↗

PubMed2003

Transcriptome analysis of Sinorhizobium meliloti during symbiosis.

BACKGROUND: Rhizobia induce the formation on specific legumes of new organs, the root nodules, as a result of an elaborated developmental program involving the two partners. In order to contribute to a more global view of the genetics underlying this plant-microbe symbiosis, we have mined the recently determined Sinorhizobium meliloti genome sequence for genes potentially relevant to symbiosis. We describe here the construction and use of dedicated nylon macroarrays to study simultaneously the expression of 200 of these genes in a variety of environmental conditions, pertinent to symbiosis. RESULTS: The expression of 214 S. meliloti genes was monitored under ten environmental conditions, including free-living aerobic and microaerobic conditions, addition of the plant symbiotic elicitor luteolin, and a variety of symbiotic conditions. Five new genes induced by luteolin have been identified as well as nine new genes induced in mature nitrogen-fixing bacteroids. A bacterial and a plant symbiotic mutant affected in nodule development have been found of particular interest to decipher gene expression at the intermediate stage of the symbiotic interaction. S. meliloti gene expression in the cultivated legume Medicago sativa (alfalfa) and the model plant M. truncatula were compared and a small number of differences was found. CONCLUSIONS: In addition to exploring conditions for a genome-wide transcriptome analysis of the model rhizobium S. meliloti, the present work has highlighted the differential expression of several classes of genes during symbiosis. These genes are related to invasion, oxidative stress protection, iron mobilization, and signaling, thus emphasizing possible common mechanisms between symbiosis and pathogenesis.

Cluster Analysis↗

PubMed2006

Patterns of expansion and expression divergence in the plant polygalacturonase gene family.

BACKGROUND: Polygalacturonases (PGs) belong to a large gene family in plants and are believed to be responsible for various cell separation processes. PG activities have been shown to be associated with a wide range of plant developmental programs such as seed germination, organ abscission, pod and anther dehiscence, pollen grain maturation, fruit softening and decay, xylem cell formation, and pollen tube growth, thus illustrating divergent roles for members of this gene family. A close look at phylogenetic relationships among Arabidopsis and rice PGs accompanied by analysis of expression data provides an opportunity to address key questions on the evolution and functions of duplicate genes. RESULTS: We found that both tandem and whole-genome duplications contribute significantly to the expansion of this gene family but are associated with substantial gene losses. In addition, there are at least 21 PGs in the common ancestor of Arabidopsis and rice. We have also determined the relationships between Arabidopsis and rice PGs and their expression patterns in Arabidopsis to provide insights into the functional divergence between members of this gene family. By evaluating expression in five Arabidopsis tissues and during five stages of abscission, we found overlapping but distinct expression patterns for most of the different PGs. CONCLUSION: Expression data suggest specialized roles or subfunctionalization for each PG gene member. PGs derived from whole genome duplication tend to have more similar expression patterns than those derived from tandem duplications. Our findings suggest that PG duplicates underwent rapid expression divergence and that the mechanisms of duplication affect the divergence rate.

Arabidopsis↗

PubMed2026

Epigenetic safety of in vitro maturation in PCOS: genome-wide DNA methylation profiling of cord blood from a randomized controlled trial.

BACKGROUND: In vitro maturation (IVM) provides a safer alternative to conventional in vitro fertilization (IVF) for women with polycystic ovary syndrome (PCOS) by mitigating the risk of ovarian hyperstimulation. However, concerns persist regarding whether IVM perturbs epigenetic reprogramming in the offspring. Current evidence is constrained by candidate-gene approaches or a lack of parental controls. This study aimed to evaluate the genome-wide DNA methylation safety of IVM compared with conventional IVF using a rigorous trio-based design. METHODS: This secondary epigenetic analysis was nested within a randomized controlled trial (RCT) (ClinicalTrials.gov: NCT03463772). We included 10 nuclear families (trios), comprising five IVM-conceived and five IVF-conceived singleton offspring alongside their biological parents. Both groups utilized a uniform freeze-only single-blastocyst transfer strategy to minimize hormonal confounding. Genomic DNA from umbilical cord blood (UCB) and parental peripheral blood was analyzed using reduced representation bisulfite sequencing (RRBS). Genome-wide methylation patterns and differentially methylated regions (DMRs) were subsequently compared between the groups. RESULTS: Clinical characteristics were comparable between the IVM and IVF groups. Genome-wide analyses demonstrated high concordance in UCB methylation patterns, revealing no significant differences in global CpG methylation levels or distributions across key genomic features (promoters, CpG islands, and gene bodies). Only three rare DMRs were identified in UCB (representing ~ 0.0001% of the genome), none of which mapped to imprinted or developmentally critical loci. Furthermore, methylation variability remained consistent between the groups. CONCLUSIONS: Our findings provide robust mechanistic evidence supporting the epigenetic safety of IVM. The remarkable stability of the neonatal methylome confirms that specific IVM conditions do not compromise early developmental programming, thereby endorsing IVM as a safe and viable alternative for women with PCOS. TRIAL REGISTRATION: ClinicalTrials.gov registry, NCT03463772. Registered on March 13, 2018.

Humans↗

PubMed1997

D1 and D2 dopamine receptors in perinatal and adult basal ganglia.

There is reason to believe that dopamine is important in developmental programs of the basal ganglia, brain nuclei implicated in motor and cognitive processing. Dopamine exerts effects through dopamine receptors, which are predominantly of the D1 and D2 subtypes in the basal ganglia. Cocaine acts as a stimulant of dopamine receptors and may cause long-term abnormalities in children exposed in utero. Dopamine receptor (primarily D1) stimulation has been linked to gene regulation. Therefore, D1 and D2 receptor densities in perinatal and adult striatum and globus pallidus were examined using quantitative autoradiography. The most striking finding was that pallidal D1 receptor densities were 7-15 times greater in the perinatal cases than in the adult. Pallidal D2 receptor densities were similar at both ages. In both the adult and perinatal striatum, D2 receptor densities were greater in the putamen than in the caudate, and both D1 and D2 receptor densities were modestly enriched in caudate striosomes compared with the matrix. In both caudate and putamen, perinatal D1 receptor levels were within the adult range, whereas D2 receptor levels were only 50% of adult values. The development of D1 and D2 receptors appears to vary across the major subdivisions of the human basal ganglia. The facts that we found such extremely high levels of D1 receptors in the perinatal pallidum, and that D1 receptor activation influences gene regulation, suggest that the globus pallidus could be particularly susceptible to long-term changes with perinatal exposure to cocaine and other D1 receptor agonists or antagonists.

Aged↗

PubMed1999

The relationship between differentiation and proliferation in late gestation fetal rat hepatocytes.

Hepatocyte proliferation and differentiation occur simultaneously during late mammalian gestation. We hypothesized that regulation of hepatocyte growth and differentiation would be coordinated in late gestation fetal hepatocyte cultures such that proliferation would be most active in a population of less well-differentiated cells. Cultured fetal hepatocytes (embryonic d 19 and 21; E19 and E21) were studied using double staining immunofluorescent microscopy. Differentiation was assessed as staining for alpha-fetoprotein (AFP), three markers of enzymic differentiation (glucokinase [GK], phosphoenolpyruvate carboxykinase [PEPCK], and carbamoyl phosphate synthase [CPS]), and a hepatocyte cell-cell adhesion molecule (C-CAM). Proliferation was assessed using immunocytochemical detection of proliferating cell nuclear antigen (PCNA) or 5-bromo-2'-deoxy-uridine (BrdU) incorporation into DNA. Fetal hepatocyte cultures consisted of a heterogeneous population of cells, slightly more than half of which were proliferative under defined, growth factor-free conditions. These cultures were heterogeneous for AFP expression. There was no correlation between the expression of AFP and PCNA or AFP and S-phase entry (BrdU staining) during the first 48 h in culture. Similar results were obtained in staining for the enzymic differentiation markers and C-CAM. In addition, the differentiation status of cultured fetal hepatocytes was unrelated to a presumed indicator of mature growth regulation, mitogenic responsiveness to transforming growth factor alpha (TGFalpha), and hepatocyte growth factor (HGF). Finally, absence of any correlation between proliferation and differentiated phenotype was supported by in vivo studies using staining for PCNA, AFP, CPS, and PEPCK in liver sections. These results indicate that the developmental program governing differentiation of late gestation fetal rat hepatocytes is independent from mechanisms controlling proliferation.

Animals↗

PubMed1991

Androgen receptor expression in the developing rat prostate is not altered by castration, flutamide, or suppression of the adrenal axis.

Mesenchymal epithelial interactions are believed to be important to the growth and development of the neonatal prostate. Prior studies in the rat ventral prostate, using autoradiography and tritiated dihydrotestosterone, indicate that androgen receptors are present in the prostatic stroma on day 3 and are detected in the epithelium by the tenth postnatal day. These findings suggested that androgen stimulation of the prostatic mesenchyme is a crucial step in the growth and development of the prostate. We have examined this developmental program directly using polyclonal antibodies that recognize specific epitopes of the androgen receptor to examine the pattern of androgen receptor expression in intact and neonatally castrate animals. In keeping with previous studies, androgen receptors are present in the prostate stroma at birth and subsequently appear in the prostatic epithelium by the 10th postnatal day. Development of androgen receptor expression in the epithelium was not changed when the animals were castrated at birth, castrated and blocked by flutamide, or castrated and given hydrocortisone to suppress the production of adrenal androgens. These findings suggest that the appearance of androgen receptors in the prostatic epithelium is programmed by androgens before birth or that factors other than testicular or adrenal androgens control the development of epithelial androgen receptors.

Adrenal Glands↗

PubMed1992

Cloning of an ovine 11 beta-hydroxysteroid dehydrogenase complementary deoxyribonucleic acid: tissue and temporal distribution of its messenger ribonucleic acid during fetal and neonatal development.

Glucocorticoids promote the development of many organ systems vital for extrauterine survival, and fetal cortisol provides the trigger for birth in sheep. The activity of glucocorticoids may be influenced at a cellular level by 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD), which is responsible for the interconversion of cortisol and cortisone. To examine 11 beta-HSD gene expression during fetal development, two overlapping clones which yield a 1.4 kilobase (kb) complementary DNA encoding sheep 11 beta-HSD from a liver library were isolated by using a rat 11 beta-HSD cDNA as the probe. This cDNA contains a 879 base pair open reading frame for a protein of 292 amino acids that has more than 70% sequence identity to rat and human 11 beta-HSDs. To define the tissue distribution of 11 beta-HSD messenger RNA in sheep, selected tissues were collected from one fetus at day 130 and term (approximately 145 days), and from a nonpregnant ewe. Cellular RNA was extracted and subjected to Northern blot analysis, and a single 1.8 kb transcript was detected in the fetal and adult liver, lung, hypothalamus, anterior pituitary, and placenta. This was undetectable in adrenals and kidneys, but a smaller (1.5 kb) transcript was present in fetal and adult kidney RNA. The relative abundance of 11 beta-HSD mRNA was greatest in fetal and adult livers, and it was much higher in adult liver, lung, and kidney than in the corresponding fetal tissues. To examine whether 11 beta-HSD gene expression is developmentally regulated in the fetal sheep, liver, lung, and kidney tissues were taken from fetuses at day 60-70, day 100-110, day 125-130, at term, and from newborn lambs (24-48 h old). In the lung and kidney, the relative abundance of 11 beta-HSD mRNA did not change from day 60 to term but increased in the lungs of newborn lambs. In contrast, 11 beta-HSD mRNA levels in the liver increased between day 125 and term and rose further in the newborn. Collectively, these results demonstrate that 11 beta-HSD gene expression in sheep is regulated in a tissue-specific and developmentally programmed manner.

11-beta-Hydroxysteroid Dehydrogenases↗

PubMed1993

Thyroid hormone regulation of RC3, a brain-specific gene encoding a protein kinase-C substrate.

RC3 is a brain-specific mRNA expressed in discrete neuronal groups of the forebrain that encodes a 78-amino acid protein, also called neurogranin, a calmodulin-binding, protein kinase-C substrate. Expression of RC3 mRNA was studied in normal and hypothyroid animals during the first month of life. Hypothyroid rats were produced by administration of methyl-mercapto-imidazol to the pregnant dams and subsequent surgical thyroidectomy on postnatal day 5 of the neonates. As studied by slot-blotting of total cerebrum poly(A)+ RNA, RC3 mRNA accumulates in normal brain from the fifth to seventh postnatal day, reaching maximal levels around days 10-12. RC3 mRNA accumulation in hypothyroid animals was blunted, and the maximal levels attained were about 30-50% of normal values. The effect of hypothyroidism on steady state mRNA levels was also observed by Northern blotting of RNA from cerebral cortex and striatum. As studied by immunoblotting using a polyclonal antibody, hypothyroidism also led to clear decreases in the amount of the RC3 protein in extracts from cerebral cortex, striatum, and hippocampus. A single administration of 10 micrograms T4 to hypothyroid rats on postnatal day 12 led to a steady increase in striatal RC3 mRNA from levels that were about 40% of normal to about 70% of normal at 16 h and 115% of normal at 48 h. In contrast to the effect on RC3, hypothyroidism did not affect developmental expression of the mRNA encoding GAP-43, another brain protein kinase-C substrate of axonal localization. RC3 is, thus, one of the few known neuronal genes whose expression is influenced by thyroid hormone in the brain. Thyroid hormone is required for an appropriate level of expression, not for the developmentally programmed timing of expression of the RC3 gene.

Animals↗

PubMed1996

Transcription factor Sp1 is expressed by three different developmentally regulated messenger ribonucleic acids in mouse spermatogenic cells.

Gene expression during spermatogenesis is highly cell- and stage-specific and involves the complex interplay of multiple developmentally regulated transcription factors. Recent evidence suggests that the DNA-binding protein Sp1 functions as an important trans-activator during cell development and differentiation. In the present study, the developmental expression of Sp1 was characterized during mouse spermatogenesis. Three distinct Sp1 transcripts were detected in mouse spermatogenic cells, each with a distinct developmental pattern; an 8.2-kilobase (kb) messenger RNA (mRNA) identical in size to the somatic mRNA expressed in spermatogonial cells, a larger mRNA approximately 8.8 kb in size present in meiotic cells, and a 2.4 kb mRNA in meiotic and postmeiotic germ cells. The 8.8- and 2.4-kb Sp1 transcripts were not observed in somatic cells and, thus, are male germ cell specific. Northern, ribonuclease protection, and RT-PCR assays revealed that the 2.4-kb Sp1 transcript is truncated in both the 5'- and 3'-untranslated regions relative to the somatic mRNA and lacks a short segment of the N-terminal coding region. Polysome analysis further indicated that these germ cell-specific Sp1 mRNAs are translated, albeit with a lower efficiency than the somatic transcript. Consistent with these results, spermatogenic cells were shown to contain approximately 9-fold lower concentrations of Sp1 proteins that are approximately the same size as the somatic form. Of particular interest, the apparent affinity of Sp1 DNA-binding activity in nuclear extracts from mouse germ cells was 5-fold greater than that in extracts from mouse somatic tissues. This may reflect the existence of mechanisms within mouse spermatogenic cells that compensate for the lower nuclear concentrations of Sp1 protein. These results suggest that cell- and stage-specific regulation of Sp1 gene expression and activity may be an important component of the mouse spermatogenic cell developmental program.

Amino Acid Sequence↗