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PubMed1996

Comparison of the expression patterns of five developmentally regulated genes in Manduca sexta and their regulation by 20-hydroxyecdysone in vitro.

A previous study, using subtractive hybridization, identified five genes (esr16, esr20, Mng10, Mng14 and tps9) whose transcripts were up-regulated prior to metamorphosis in Manduca sexta nervous tissue. The developmental time points chosen for subtraction suggested that expression could be coordinately regulated and should be negatively regulated by the steroid hormones, the ecdysteroids. In the present paper, we present an analysis of the expression patterns of these five genes, using reverse transcription-polymerase chain reaction (RT-PCR), at various times during development and assess the effects of 20-hydroxyecdysone and cycloheximide on their expression in vitro. This analysis revealed that with the exception of esr20 all transcripts were detectable at all times and that all but one of the genes were up-regulated in vivo and in vitro in the absence or in the presence of low levels of the ecdysteroids. In the absence of ecdysteroids, cycloheximide blocked the accumulation of only two transcripts, esr16 and esr20. These results reveal a much more complex pattern of gene expression in the central nervous system prior to metamorphosis than previously imagined.

Animals↗
PubMed2001

Retinoic acid synthesis for the developing telencephalon.

The small lipid retinoic acid is known to promote neuronal differentiation in vitro and to act as a teratogen in the embryonic brain, but very little is known about the natural role of endogenously synthesized retinoic acid in forebrain development. Retinoic acid is synthesized mainly by three retinaldehyde dehydrogenases. We show here where the retinaldehyde dehydrogenases for the developing telencephalon are expressed and how their expression patterns change over developmental time. Retinoic acid diffusing from the retinaldehyde dehydrogenase sites is likely to influence the early telencephalon before the beginning of neurogenesis, as well as differentiation and radial migration of neurons into the cerebral cortex. Because of its diffusible character, retinoic acid represents a unique tool for the coordination of growth processes over an intermediate distance range in the developing telencephalon.

Aldehyde Oxidoreductases↗
PubMed2001

Alterations in fatty acid composition of tissue phospholipids in the developing retinal dystrophic rat.

Alterations in lipid composition occur in the retinal pigment epithelium and photoreceptor cells of the Royal College of Surgeons (RCS) dystrophic rat, a model for inherited retinal degeneration. With respect to lipid composition of nonretinal tissues, the developmental timing of lipid alterations and the incidence of dystrophy are unknown. We determined the fatty acid composition in choline phosphoglycerides (ChoGpl) and ethanolamine phosphoglycerides (EtnGpl) in the brain, liver, and retina from dystrophic RCS rats and from their nondystrophic congenics (controls) at the ages of 3 and 6 wk. At 3 wk, the fatty acid compositions were specific to individual phospholipid classes without any difference between dystrophic and nondystrophic tissues. In plasma phospholipids, there was an age-related increase in the relative contents of monounsaturated and n-3 polyunsaturated fatty acids, with only minor differences between dystrophic and nondystrophic rats. At 6 wk, the fatty acid compositions in ChoGpl and EtnGpl from dystrophic brain and retina were significantly different from those of nondystrophics. The effect of strain on developmental changes in brain fatty acid composition was significant for 18:0 and 22:6n-3 in EtnGpl and for 16:0, 18:0, 18:1n-9, and 20:4n-6 in ChoGpl. The brain ChoGpl fatty acid composition in nondystrophic rats was similar at 6 wk to that of normal rats, and there were almost no postweaning changes in the dystrophics. In retinal phospholipids, the effect of dystrophy was to increase the 20:4n-6 content in EtnGpl and to decrease 22:6n-3 in ChoGpl. The 18:2n-6 and 22:6n-3 contents in dystrophic liver ChoGpl were also significantly affected, while no difference was observed in the EtnGpl fraction. The dystrophy affected the phospholipid fatty acid developmental changes in a tissue- and class-specific manner. Fatty acid metabolism could be selectively altered in neural and nonneural tissues of developing dystrophic RCS rats.

Aging↗
PubMed1995

Culture of marmoset blastocysts on matrigel: a model of differentiation during the implantation period.

BACKGROUND: The objective was to develop an experimental model for studying the differentiation of trophoblast and inner cell mass (ICM) during the early stages of implantation in primates. METHODS: Marmoset monkey blastocytes were used in these studies. Ovulation was timed by plasma progesterone assays in ovarian cycles initiated by administering a luteolytic agent to mating marmosets. Embryos were recovered from the uterus usually at the eight-cell stage and cultured in minimum essential medium containing fetal calf serum, insulin, and transferrin. The embryos that formed hatched blastocysts by about day 11 after ovulation were transferred for further development in Matrigel-coated culture chambers. After 2, 4, and 6 days of development, two blastocysts were processed at each interval and serially sectioned for light and electron microscopy. RESULTS: All blastocysts adhered to the Matrigel at their embryonic pole within 24 hours. Adherent polar cytotrophoblast was differentiating to syncytiotrophoblast at all time intervals, but syncytium was not detected in mural trophoblast until day 4 after attachment. By day 2 syncytial microvilli and processes had penetrated the Matrigel surface, whereas by days 4 and 6 cytotrophoblast that was differentiating to syncytiotrophoblast had invaded the matrix. Since all blastocysts maintained their structural integrity progressive differentiation of the ICM, endoderm and presumptive mesoderm was observed. A small amniotic cavity was observed at 2 days and by 6 days a distinct cavity separated polarized epiblast and amnion cells. Visceral and parietal endoderm were present at 2 days, and a completed primary yolk sac was observed by 4 days after attachment. In all blastocysts a basal lamina lined the inner surface of mural and polar trophoblast and the basal surface of the differentiating ICM. CONCLUSIONS: The developmental time sequence of the cultured blastocysts closely resembled the time frame reported for marmoset embryos implanting in utero. An effective model for studying trophoblast invasion and differentiation of embryonic germ cell layers has been established.

Amnion↗
PubMed2026

Does Timing Matter? Age of First Mobile Phone Acquisition and Psychological Outcomes in Middle and Late Adolescence.

The age at which adolescents acquire their first smartphone has decreased markedly in recent years; however, evidence on its long-term effects on psychosocial adjustment remains limited. This study investigated whether age at first mobile phone acquisition is associated with psychosocial functioning in middle and late adolescence, including social integration and competence, emotion regulation difficulties, disordered eating behaviors and problematic social media use (PSMU). The sample comprised 1179 adolescents aged 15-17 years (53.8% female). Linear regression and generalized additive mixed models were used to examine both linear and nonlinear associations, adjusting for age, gender and school clustering. Earlier smartphone acquisition was linearly but weakly associated with greater emotion regulation difficulties, disordered eating and PSMU, even after adjustment for covariates. In contrast, associations with social integration and competence were nonlinear: acquiring a first smartphone between ages 6 and 10 or after age 13 was associated with lower social integration in adolescence, whereas acquisition between ages 11 and 13 was linked to higher social functioning. These findings suggest that the developmental timing of first smartphone access shows a modest association with subsequent psychosocial functioning during middle and late adolescence. Focusing on the timing of access, alongside other demographic and contextual factors, may contribute to a better understanding of digital influences on adolescent well-being.

Humans↗
PubMed2000

Sublethal effects of resin glycosides from the periderm of sweetpotato storage roots on Plutella xylostella (Lepidoptera: Plutellidae).

Resin glycoside material extracted from the periderm tissue of storage roots from sweetpotato, Ipomoea batatas (L.) Lam., was bioassayed for effects on survival, development, and fecundity of the diamondback moth, Plutella xylostella (L.). The resin glycoside was incorporated into an artificial diet and fed to P. xylostella larvae. First instars were placed individually into snap-top centrifuge vials containing artificial diet with one of six concentrations of resin glycoside material (0.00, 0.25, 0.50, 1.00, 1.50, and 2.00 mg/ml). Each replication consisted of 10 individuals per concentration, and the experiment was repeated 13 times. Vials were incubated at 25 degrees C and a photoperiod of 14:10 (L:D) h in a growth chamber. After 6 d, surviving larvae were weighted and their sex determined, then returned to their vials. Later, surviving pupae were weighed and incubated at 25 degrees C until moths emerged. Females were fed, mated with males from the laboratory colony, and allowed to lay eggs on aluminum foil strips. Lifetime fecundity (eggs/female) was measured. There were highly significant negative correlations between resin glycoside levels and survival, and between glycoside levels and larval weight after 6 d of feeding. For larvae that lived at least 6 d, there was no additional mortality that could be attributed to the resin glycoside material. However, there was a significant positive correlation between glycoside dosages and developmental time of larvae (measured as days until pupation). Lifetime fecundity also was negatively affected at sublethal doses. Resin glycosides may contribute to the resistance in sweetpotato breeding lines to soil insect pests.

Animals↗
PubMed2001

Differential regulation of the two principal Runx2/Cbfa1 n-terminal isoforms in response to bone morphogenetic protein-2 during development of the osteoblast phenotype.

Cbfa1/Runx2 is a transcription factor essential for bone formation and osteoblast differentiation. Two major N-terminal isoforms of Cbfa1, designated type I/p56 (PEBP2aA1, starting with the sequence MRIPV) and type II/p57 (til-1, starting with the sequence MASNS), each regulated by distinct promoters, are known. Here, we show that the type I transcript is constitutively expressed in nonosseous mesenchymal tissues and in osteoblast progenitor cells. Cbfa1 type I isoform expression does not change with the differentiation status of the cells. In contrast, the type II transcript is increased during differentiation of primary osteoblasts and is induced in osteoprogenitors and in premyoblast C2C12 cells in response to bone morphogenetic protein-2. The functional equivalence of the two isoforms in activation and repression of bone-specific genes indicates overlapping functional roles. The presence of the ubiquitous type I isoform in nonosseous cells and before bone morphogenetic protein-2 induced expression of the type II isoform suggests a regulatory role for Cbfa1 type I in early stages of mesenchymal cell development, whereas type II is necessary for osteogenesis and maintenance of the osteoblast phenotype. Our data indicate that Cbfa1 function is regulated by transcription, cellular protein levels, and DNA binding activity during osteoblast differentiation. Taken together, our studies suggest that developmental timing and cell type- specific expression of type I and type II Cbfa isoforms, and not necessarily molecular properties or sequences that reside in the N-terminus of Cbfa1, are the principal determinants of the osteogenic activity of Cbfa1.

Animals↗
PubMed1998

Analysis of transcriptional regulatory regions in vivo.

Understanding the transcriptional regulation of development and tissue-specific gene expression is a central goal of modern biology. Although the analysis of gene transcription in transfected cultured cells has been essential in establishing many key aspects of this gene control, only analysis in animals can determine developmental timing and cell-specificity of expression within a complex organ and in all the tissues of an animal. The advent of transgenesis made in vivo studies possible. A summary of the in vivo regulatory properties of the pancreas-specific transcriptional enhancer of the rat elastase 1 gene (ELA1) and the role individual elements in this enhancer play in directing high level, cell-specific transcription illustrates the nature, revelations and limitations of transgenic analysis.

Animals↗
PubMed2002

Onset of Tlx-3 expression in the chick cerebellar cortex correlates with the morphological development of fissures and delineates a posterior transverse boundary.

Recent studies have shown that the mammalian cerebellar cortex can be subdivided into a reproducible array of zones and stripes. In particular, discontinuous patterns of gene expression together with mutational analysis suggest that there are at least four distinct transverse zones along the rostrocaudal axis in mouse: the anterior zone (lobules I-V), the central zone (lobules VI and VII), the posterior zone (lobules VIII and IX), and the nodular zone (lobule X). Here we show that the divergent homeobox-containing transcription factor, Tlx- 3 (also known as Hox11L2 or Rnx) is transiently expressed in external granule cells in a distinct transverse domain of the developing chick cerebellar cortex. Expression is first detected at Hamburger and Hamilton (HH) stage 35. Interestingly, Tlx-3 mRNA expression is initially confined to, and coincident with, the morphological development of fissures. Slightly later, at HH stage 38, expression extends throughout the developing external granular layer (EGL) of lobules I-IXab. Notably, no Tlx-3 expression was detected in lobules IXc and X at any developmental time point examined. Expression is noticeably stronger in nonproliferating cells located in the deep layer of the EGL. Tlx-3 expression is downregulated as granule cells migrate inward to form the internal granule layer and is undetectable shortly after birth. These results suggest that Tlx-3 is expressed as granule cells become postmitotic and suggest that Tlx-3 may play a role in the differentiation of distinct neuronal populations in the cerebellum.

Animals↗
PubMed1983

High-frequency conversion to a "fluffy" developmental phenotype in Aspergillus spp. by 5-azacytidine treatment: evidence for involvement of a single nuclear gene.

Transient exposure of mycelia from Aspergillus niger and Aspergillus nidulans to the cytidine analog 5-azacytidine, leading to no more than 0.3 to 0.5% substitution for cytosine by 5-azacytosine in A. nidulans DNA, resulted in the conversion of a high fraction of the cell population (more than 20%) to a mitotically and meiotically stable "fluffy" developmental phenotype. The phenotypic variants are characterized by the developmentally timed production of a profuse fluffy network of undifferentiated aerial hyphae that seem to escape signals governing vegetative growth. Genetic analysis with six different fluffy clones reveals that this trait is not cytoplasmically coded, is recessive in heterozygous diploids but codominant in heterokaryons, and exhibits a 1:1 Mendelian segregation pattern upon sexual sporulation of heterozygous diploids. Complementation and mitotic haploidization studies indicated that all variants are affected in the same gene, which can be tentatively located on chromosome VIII of A. nidulans. Molecular analysis to search for modified bases showed that DNA methylation is negligible in in both A. niger and A. nidulans and that no differences could be detected among DNAs from wild-type cells, fluffy clones, or mycelia exposed to 5-azacytidine. It thus appears that high-frequency conversion of fungal mycelia to a stable, variant developmental phenotype by 5-azacytidine is the result of some kind of target action on a single nuclear gene and that this conversion can occur in organisms virtually devoid of DNA methylation.

Aspergillus nidulans↗
PubMed1991

The contrasting roles of N-CAM and N-cadherin as neurite outgrowth-promoting molecules.

The neural cell adhesion molecule (N-CAM) is a prominent member of the immunoglobulin gene superfamily of recognition molecules. It operates in a calcium-independent manner to promote cell-cell adhesion. Alternative splicing of a single gene generates more than twenty N-CAM isoforms and these can be further modified by the differential addition of complex N- and O-linked carbohydrates. In contrast, N-cadherin is a major calcium-dependent adhesion molecule in the brain; it is not a member of the immunoglobulin gene superfamily and, as far as we know, exists as a single gene product with no evidence of differential post-translational modification. Both molecules are believed to operate through a homophilic binding mechanism and both are expressed at key developmental times in a number of tissues including the brain. Antibody perturbation experiments suggest that both of the above cell adhesion molecules (CAMs) can support neurite outgrowth over complex cellular substrata such as astrocytes and Schwann cells. In the present review we discuss the use of a molecular genetic approach to study the neurite outgrowth-promoting activity of these molecules. Using this approach we have found that both CAMs are potent inducers of neurite outgrowth from a variety of neurons. However, whereas a critical value of N-CAM expression is required for increased neurite outgrowth, with small increases above this value having substantial effects, N-cadherin promotes neurite outgrowth in a highly linear manner. In addition, whereas N-CAM promotes chick retinal ganglion cell (RGC) neurite outgrowth at E6 but not E11, N-cadherin does so throughout this developmental period.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2000

Co-ordination of the expression of the protein tyrosine kinase p56(lck) with the pre-T cell receptor during thymocyte development.

The protein tyrosine kinase p56(lck) is essential for the regulation of early thymocyte development by transducing pre-T cell receptor (pre-TCR) mediated-signals. Here we have investigated the developmental timing of expression of p56(lck) in the thymus. We show that p56(lck) transcripts are detectable in each CD4(-)CD8(-) double-negative (DN) thymocyte subset defined by CD25 and CD44. The steady-state level of p56(lck) mRNA with these four DN subsets is similar, varying by less than 2-fold. However, p56(lck) protein levels are undetectable in DN subsets 1 and 2, but are at least 20-fold up-regulated between DN subsets 2 and 3. Analysis of independent transgenic mouse lines in which the proximal p56(lck) promoter was used to drive expression of a green fluorescent protein (GFP) reporter gene revealed a lack of correlation between GFP mRNA expression and transgene copy number and variable expression of GFP protein in different lines. Taken together these results show that the expression of the p56(lck) gene is developmentally regulated at the post-transcriptional level at the precise developmental stage at which its upstream receptor complex, the pre-TCR, is expressed. These results also have implications for the interpretation of the phenotype of transgenic mice which utilize the p56(lck) proximal promoter.

Animals↗
PubMed2005

Cdx binding determines the timing of enhancer activation in postnatal duodenum.

In mammalian intestine, adenosine deaminase (ADA) is expressed at high levels only along the villi of the duodenal epithelium. A duodenum-specific enhancer identified in the second intron of the human ADA gene controls this pattern of expression. This enhancer faithfully recapitulates this expression pattern in transgenic mice, when included in CAT reporter gene constructions. Multiple binding sites for PDX-1 and GATA factors were previously identified within the approximately 300-bp region that encompasses the enhancer. Mutation analyses demonstrated that binding of PDX-1 and of GATA-4 was absolutely essential for enhancer function. In the present study, we have identified additional enhancer binding sites for Cdx factors, for YY1, and for NFI family members. Detailed EMSA studies were used to confirm binding at these sites. This brings the number of confirmed binding sites within the enhancer to thirteen, with five different factors or family of factors contributing to the putative enhanceosome complex. Mutation analysis was utilized to examine the specific roles of the newly identified sites. Two sites were identified that bound both Cdx1 and Cdx2. Mutations were identified in these two sites that completely and specifically eliminated Cdx binding. In transgenic mice, these enhancer mutations dramatically changed the developmental timing of enhancer activation (delaying it by 2-3 weeks) without affecting other aspects of enhancer function. In the chromatin context of certain transgenic insertion sites, mutation of the two YY1 sites to specifically ablate binding caused a delay in enhancer activation similar to that observed with the Cdx mutations. No overt changes were observed from mutation of the NFI site.

Adenosine Deaminase↗
PubMed2006

The role of ascorbic acid in the control of flowering time and the onset of senescence.

Ascorbic acid (AA) is not only an important antioxidant, it also appears to link flowering time, developmental senescence, programmed cell death, and responses to pathogens through a complex signal transduction network. The biological activity of AA is defined by its oxidation and subsequent regeneration into the reduced form. Some studies suggest that the total endogenous level of AA influences induction of flowering and senescence. Both processes require the co-ordinated regulation of gene expression, which is mediated by various phytohormones. For example, gibberellins and salicylic acid are known to promote flowering, but inhibit or retard senescence in Arabidopsis. Ethylene and abscisic acid accelerate senescence. Ascorbic acid serves as an important co-factor for the synthesis of some of these hormones. Therefore, it is assumed that AA affects phytohormone-mediated signalling processes during the transition from the vegetative to the reproductive phase and the final stage of development, senescence. This review summarizes recent reports that investigate the effect of AA on flowering time and the onset of senescence. An attempt was made to bring these findings in context with previously characterized flowering and senescence pathways and a model is proposed that may explain how AA influences flowering and senescence both under long- and short-day conditions in Arabidopsis.

Aging↗
PubMed2000

Neuromotor markers of risk for schizophrenia.

OBJECTIVE: To evaluate the possibility of using neuromotor deviation (NMD) as an individual-orientated, early life marker for increased risk for schizophrenia. METHOD: Previous findings based on systematic examination of NMD are summarised concerning schizophrenia patients and individuals at heightened genetic risk for schizophrenia. RESULTS: Significantly increased rates of NMD are found in patients with schizophrenia, both after and long before disease onset. Neuromotor deviation can be efficiently studied at all ages from infancy to adulthood, and is typically not in itself stigmatising. Neuromotor deviation may represent an unstable characteristic of individuals from infancy to middle-to-late childhood, possibly attaining greater stability thereafter. Neuromotor deviation may also be more stable over time in the high-risk offspring of parents with schizophrenia than in other children. Neuromotor deviation in childhood predicts subsequent serious mental disturbance in genetic high-risk children. The efficiency of NMD for predicting schizophrenia in unselected samples is unknown, as is the optimal age(s) for assessing NMD to predict schizophrenia in high-risk and normal-risk groups. Neuromotor deviation is also found in the well relatives of schizophrenia patients, individuals developing a broad range of mental and physical disorders, and mentally normal individuals in the general population. CONCLUSIONS: Neuromotor deviation should definitely be included in batteries of methods for identifying individuals with notably heightened risk of schizophrenia. However, NMD is not pathognomonic for schizophrenia, and the investigation of NMD during childhood and adolescence must thus be used judiciously in order to avoid possible stigmatisation. Further research should be done concerning the specific forms and developmental timing of NMD as related to schizophrenia.

Adult↗
PubMed2002

Transforming growth factor-beta and insulin-like signalling pathways in parasitic helminths.

The signal transduction pathways involved in regulating developmental arrest in the free-living nematode, Caenorhabditis elegans, are fairly well characterised. However, much less is known about how these processes may influence the developmental timing and maturation in helminth parasites. Here, we provide an overview of two signalling pathways implicated in the regulation of dauer larva formation in C. elegans, the insulin-like signalling pathway and the transforming growth factor-beta pathway, and explore what is known about these signalling pathways in a variety of parasitic helminths. Understanding the differences about how these pathways are affected by environmental cues in free-living versus parasitic species of helminths may provide insights into novel mechanisms for the control or prevention of helminth-induced disease.

Animals↗
PubMed2002

Empty pericarp2 encodes a negative regulator of the heat shock response and is required for maize embryogenesis.

The heat shock response (HSR) is an evolutionarily conserved molecular/biochemical reaction to thermal stress that is essential to the survival of eukaryotic organisms. Recessive Mutator transposon mutations at the maize empty pericarp2 (emp2) locus led to dramatically increased expression of heat shock genes, retarded embryo development, and early-stage abortion of embryogenesis. The developmental timing of emp2 mutant embryo lethality was correlated with the initial competence of maize kernels to invoke the HSR. Cloning and sequence analyses revealed that the emp2 gene encoded a predicted protein with high similarity to HEAT SHOCK BINDING PROTEIN1, which was first described in animals as a negative regulator of the HSR. emp2 is a loss-of-function mutation of an HSR-negative regulator in plants. Despite the recessive emp2 phenotype, steady state levels of emp2 transcripts were abundant in mutant kernels, and the predicted coding region was unaffected. These expression data suggest that emp2 transcription is feedback regulated, whereas S1 nuclease mapping suggests that emp2 mutant transcripts are 5' truncated and nontranslatable. In support of this model, immunoblot assays revealed that EMP2 protein did not accumulate in mutant kernels. These data support a model whereby an unattenuated HSR results in the early abortion of emp2 mutant embryos. Furthermore, the developmental retardation of emp2 mutant kernels before the HSR suggests an additional role for EMP2 during embryo development distinct from the HSR.

5' Untranslated Regions↗
PubMed2001

Sonic hedgehog regulates epithelial proliferation and cell survival in the developing tooth germ.

Shh expression is highly restricted to the future sites of tooth development during the initiation of odontogenesis. This suggests a role for Shh as a proliferative factor, as localized epithelial thickenings invaginate to form a tooth bud. We have investigated this role by blocking Shh signaling between E10.5 and E12.5 in murine mandibular processes using a 5E1 blocking antibody and the PKA activator Forskolin. This results in down-regulation of Ptc, a principle target of Shh signaling. The effects of inhibition varied with developmental time. At E10.5, tooth development was arrested as epithelial thickenings and the numbers of teeth developing were considerably reduced. Inhibition at E12.5 produced localized apoptosis in the epithelium at the tip of the tooth buds, although some teeth were able to develop. Thus, Shh has dual roles in early odontogenesis, first in bud formation by stimulating epithelial proliferation, and second in the development of cap-stage tooth germs by increasing epithelial cell survival.

Animals↗