The role of pleiotrophin and β-catenin in fetal lung development

Mammalian lung development is a complex biological process, which is temporally and spatially regulated by growth factors, hormones, and extracellular matrix proteins. Abnormal changes of these molecules often lead to impaired lung development, and thus pulmonary diseases. Epithelial-mesenchymal interactions are crucial for fetal lung development. This paper reviews two interconnected pathways, pleiotrophin and Wnt/β-catenin, which are involved in fibroblast and epithelial cell communication during fetal lung development.     

Novel methods for studying normal and disordered erythropoiesis

Erythropoiesis is a process during which multipotential hematopoietic stem cells proliferate, differentiate and eventually form mature erythrocytes. Interestingly, unlike most cell types, an important feature of erythropoiesis is that following each mitosis the daughter cells are morphologically and functionally different from the parent cell from which they are derived, demonstrating the need to study erythropoiesis in a stage-specific manner. This has been impossible until recently due to lack of methods for isolating erythroid cells at each distinct developmental stage. This review summarizes recent advances in the development of methods for isolating both murine and human erythroid cells and their applications. These methods provide powerful means for studying normal and impaired erythropoiesis associated with hematological disorders.     

Regulation of collateral blood vessel development by the innate and adaptive immune system

The development of collateral circulation is an inherent compensatory mechanism to restore impaired blood perfusion following artery stenosis and/or occlusion. This process, termed arteriogenesis, is driven by inflammation and involves a complex remodeling of pre-existing conduit vessels running in parallel to the occluded artery. Recent studies have unveiled roles for different immune cell subsets as regulators of arteriogenesis, including natural killer (NK) cells, T helper 17 (Th17) cells, regulatory T lymphocytes (Tregs), and functional subsets of macrophages (e.g., M2 macrophages). This review summarizes recent findings and discusses future research needed to better define the time during which each cellular subset is active and reveal further critical regulatory switches.     

Mouse gridlock: no aortic coarctation or deficiency,but fatal cardiac defects in Hey2 -/- mice

Gridlock (grl) is one of the first mutations characterized from the large zebrafish mutagenesis screens, and it results in an arterial (aortic) maturation defect, which was proposed to resemble aortic coarctation, a clinically important human malformation. While the grl mutation appears to be a hypomorph, grl knockdown experiments have shown even stronger effects on arterial development. We have generated a knockout of the murine Hey2 (gridlock) gene to analyze the mammalian phenotype. Surprisingly, Hey2 loss does not affect aortic development, but it instead leads to a massive postnatal cardiac hypertrophy with high lethality during the first 10 days of life. This cardiomyopathy is ameliorated with time in surviving animals that do not appear to be manifestly impaired during adult life. These differences in phenotypes suggest that changes in expression or function of genes during evolution may lead to quite different pathological phenotypes, if impaired.     

Development of the mammary gland requires DGAT1 expression in stromal and epithelial tissues

Mammary gland development is a complex process that is dependent on interactions between the developing mammary epithelium and the surrounding stromal tissues. We show that mice lacking the triglyceride synthesis enzyme acyl CoA:diacylglycerol transferase 1 (DGAT1) have impaired mammary gland development, characterized by decreased epithelial proliferation and alveolar development, and reduced expression of markers of functional differentiation. Transplantation studies demonstrate that the impaired development results from a deficiency of DGAT1 in both the stromal and epithelial tissues. Our findings are the first to link defects in stromal lipid metabolism to impaired mammary gland development.     

GABAergic inhibition regulates developmental synapse elimination in the cerebellum

Functional neural circuit formation during development involves massive elimination of redundant synapses. In the cerebellum, one-to-one connection from excitatory climbing fiber (CF) to Purkinje cell (PC) is established by elimination of early-formed surplus CFs. This process depends on glutamatergic excitatory inputs, but contribution of GABAergic transmission remains unclear. Here, we demonstrate impaired CF synapse elimination in mouse models with diminished GABAergic transmission by mutation of a single allele for the GABA synthesizing enzyme GAD67, by conditional deletion of GAD67 from PCs and GABAergic interneurons or by pharmacological inhibition of cerebellar GAD activity. The impaired CF synapse elimination was rescued by enhancing GABA(A) receptor sensitivity in the cerebellum by locally applied diazepam. Our electrophysiological and Ca2+ imaging data suggest that GABA(A) receptor-mediated inhibition onto the PC soma from molecular layer interneurons influences CF-induced Ca2+ transients in the soma and regulates CF synapse elimination from postnatal day 10 (P10) to around P16.     

Polar growth in the infectious hyphae of the phytopathogen ustilago maydis depends on a virulence-specific cyclin

The maize smut fungus Ustilago maydis switches from yeast to hyphal growth to infect maize (Zea mays) plants. This switching is promoted by mating of compatible cells and seems to be required for plant penetration. Although many genes distinctively expressed during this dimorphic switch have been identified and shown to be essential for the infection process, none seems to be explicitly required for polar growth control. Here, we report the characterization of pcl12, encoding a cyclin that interacts specifically with Cdk5, an essential cyclin-dependent kinase with regulatory roles in morphogenesis in U. maydis. Pcl12 fulfills the requirements to be a virulence-specific regulator of polar growth in U. maydis. First, pcl12 expression is induced during the pathogenic development. Secondly, Pcl12 is sufficient to induce hyperpolarized growth in U. maydis cells, as haploid cells overexpressing pcl12 in axenic conditions produce filaments that were morphologically indistinguishable from those produced during the infection process. Finally, cells defective in pcl12 showed impaired polar growth during the formation of the b-dependent filament, the induction of the conjugation tubes, or the formation of a promycelium in spore germination. However, in spite of this pivotal role during morphogenesis, pcl12 mutants were virulent. We discuss the implications of these results for the role of polar growth during the infection process.     

Glucocorticoid receptor antagonizes EGFR function to regulate eyelid development

The glucocorticoid receptor (GR) plays a crucial role in epidermal morphogenesis during embryonic development, as demonstrated by analyzing genetically modified mouse models of GR gain- and loss-of-function. Eyelid formation constitutes a useful model to study epithelial development, as it requires coordinated regulation of keratinocyte proliferation, apoptosis and migration. We have analyzed this biological process in GR(-/-) embryos during ontogeny. Our data demonstrate that GR deficiency results in delayed and impaired eyelid closure, as illustrated by increased keratinocyte proliferation and apoptosis along with impaired differentiation in GR(-/-) eyelid epithelial cells. These defects are due, at least in part, to the lack of antagonism between GR and epidermal growth factor receptor (EGFR) signaling, causing sustained activation of the MAPK/AP-1 pathway and the upregulation of keratin K6 at embryonic stage E18.5. Additionally, we demonstrate that GR regulates epithelial cell migration in vitro by interfering with EGFR-mediated signaling. Overall, GR/EGFR antagonism appears as a major mechanism regulating ocular epithelial development.     

Influence of acoustic signal with ultrasonic components on the development of defensive conditioned reflex in Wistar rats

Short-term (90 s) effects of the complex acoustic signal (CAS) with ultrasonic components on the development of defensive conditioned reflex of two-way active avoidance in a shuttle-box were studied in female Wistar rats. The learning ability of rats was measured on a scale designed in our laboratory. It was shown that CAS stimulation triggered an audiogenic seizure of different strength in 59% of animals. The CAS was extremely stressful for Wistar rats: it prevented the active avoidance learning in early terms after its application (the first training session in 4 or 6 days). This effect did not depend on the presence or intensity of audiogenic seizures during CAS. In the second training session in 9 days (the first session was in 4 days), learning was impaired as compared to control without CAS. However, during repeated training procedure 1.5 months after the CAS (the first session in 6 days), rats rapidly reached the criterion of learning (10 consecutive avoidance reactions). On the other hand, if the CAS was presented with different time lags (immediately, in 3 or in 45 days) after the first training session, the ability of animals to learn during the second session was not impaired both in early and late terms after exposure to the stressor. The results suggest that exposure to CAS prevents development of short-term memory but does not affect consolidation process and long-term memory.     

Autophagy machinery promotes the chaperone-mediated formation and compartmentalization of protein aggregates during appressorium development by the rice blast fungus

The chaperone-mediated sequestration of misfolded proteins into specialized quality control compartments represents an important strategy for maintaining protein homeostasis in response to stress. However, precisely how this process is controlled in time and subcellular space and integrated with the cell''s protein refolding and degradation pathways remains unclear. We set out to understand how aggregated proteins are managed during infection-related development by a globally devastating plant pathogenic fungus and to determine how impaired protein quality control impacts cellular differentiation and pathogenesis in this system. Here we show that in the absence of Hsp104 disaggregase activity, aggregated proteins are spatially sequestered into quality control compartments within conidia, but not within terminally differentiated infection cells, and thus spatial protein quality control is cell type–dependent. We demonstrate that impaired aggregate resolution results in a short-term developmental penalty but has no significant impact upon appressorium function. Finally, we show that, somewhat unexpectedly, the autophagy machinery is necessary for the normal formation and compartmentalization of protein aggregates. Taken together, our findings provide important new insight into spatial protein quality control during the process of terminal cellular differentiation by a globally important model eukaryote and reveal a new level of interplay between major proteostasis pathways.     

A gene involved in both protein secretion during growth and starvation-induced development encodes a subunit of the NADH:ubiquinone oxidoreductase in Myxococcus xanthus

The secretion of numerous proteins during vegetative growth of Myxococcus xanthus , and the multicellular development cycle induced upon starvation of these bacteria, are partially interrelated in so far as mutants impaired in extracellular protein production are unable to undergo development. We have cloned and sequenced a gene in which a Tn 5 insertion leads to a decrease in the production of most, if not all, extracellular proteins, and prevents development and sporulation. The deduced protein is homologous to the putative ubiquinone-binding subunit of bacterial and mitochondrial NADH:ubiquinone oxidoreductases (complex I). This is the first example of the presence of this complex in a bacterium from subclass δ of the proteobacteria. This gene is expressed during growth and during early development. As its disruption by Tn 5 does not impair growth of the mutant strain, we assume the presence of a second alternative NADH oxidoreductase, and suggest that the phenotypic alterations caused by the mutation are due to a decrease in the proton-motive force.     

The microtubule binding of Tau and high molecular weight Tau in apoptotic PC12 cells is impaired because of altered phosphorylation

Although the importance of the microtubule network throughout cell life is well established, the dynamics of microtubules during apoptosis, a regulated cell death process, is unclear. In a previous study (Davis, P. K., and Johnson, G. V. (1999) Biochem. J. 340, 51-58) we demonstrated that the phosphorylation of the microtubule-associated protein tau was increased during neuronal PC12 cell apoptosis. The purpose of this study was to determine whether the increased tau phosphorylation that occurred during apoptosis impaired the microtubule binding capacity of tau. This study is the first demonstration that microtubule-binding by tau and high molecular weight tau is significantly impaired as a result of altered phosphorylation during a naturally occurring process, apoptosis. Furthermore, co-immunofluorescence studies reveal for the first time that tau populations within an apoptotic neuronal PC12 cell exhibit differential phosphorylation. In control PC12 cells, Tau-1 staining (Tau-1 recognizes an unphosphorylated epitope) is evident throughout the entire cell body. In contrast, Tau-1 immunoreactivity in apoptotic PC12 cells is retained in the nuclear/perinuclear region but is significantly decreased in the cytoplasm up to the plasma membrane. The selective distribution of phosphorylated tau in apoptotic PC12 cells indicates that tau likely plays a significant role in the cytoskeletal changes that occur during apoptosis.     

Predicting Particle Size During Fluid Bed Granulation Using Process Measurement Data

In this study, a new concept for particle size prediction during the fluid bed granulation is presented. Using the process measurements data obtained from a design of experimental study, predictive partial least squares models were developed for spraying and drying phases. Measured and calculated process parameters from an instrumented fluid bed granulation environment were used as explaining factors, whereas an in-line particle size data determined by spatial filtering technique were used as response. Modeling was carried out by testing all possible combinations of two to six process parameters (factors) of the total of 41 parameters. Eleven batches were used for model development and four batches for model testing. The selected models predicted particle size (d ₅₀) well, especially during the spraying phase (Q ² = 0.86). While the measured in-line d ₅₀ data were markedly influenced by different process failures, e.g., impaired fluidization activity, the predicted data remained more consistent. This introduced concept can be applied in fluid bed granulation processes if the granulation environment is soundly instrumented and if reliable real-time particle size data from the design of experiment batches are retrieved for the model development.     

Interaction between the inducible 70-kDa heat shock protein and autophagy: effects on fertility and pregnancy

A consequence of hsp70 (HSPA1A) induction is the inhibition of autophagy. Evidence of autophagy involvement in all aspects of the reproductive process is reviewed, and possible consequences of hsp70 induction at each developmental stage are postulated. It is proposed that aberrant external or internal stimuli that result in high levels of hsp70 production interfere with normal autophagy-related functions and lead to a decrease in the number of functional ova and spermatozoa, impaired pre- and post-implantation embryo development, and increased susceptibility to premature labor and delivery. The purpose of this review is to increase understanding of hsp70-autophagy interactions during reproduction. Interventions to modulate this interaction will lead to development of novel protocols to improve fertility and pregnancy outcome.     

Impaired skeletal muscle substrate oxidation in glucose-intolerant men improves after weight loss

Objective: An impaired fatty acid handling in skeletal muscle may be involved in the development of insulin resistance and diabetes mellitus type 2 (DM2). We investigated muscle fatty acid metabolism in glucose‐intolerant men (impaired glucose tolerance (IGT)), a prediabetic state, relative to BMI‐matched control men (normal glucose tolerance (NGT)) during fasting and after a meal, because most people in the western society are in the fed state most of the day. Methods and Procedures: Skeletal muscle free fatty acid (FFA) uptake and oxidation were studied using the stable isotope tracer [2,2‐²H]‐palmitate and muscle indirect calorimetry in the forearm model during fasting and after a mixed meal (33 energy % (E%) carbohydrates, 61 E% fat). Intramyocellular triglycerides (IMTGs) were monitored with ¹H‐magnetic resonance spectroscopy. IGT men were re‐examined after weight loss (?15% of body weight (BW)). Results: The postprandial increase in forearm muscle respiratory quotient (RQ) was blunted in IGT compared to NGT, but improved after weight loss. Weight loss also improved fasting‐fat oxidation and tended to decrease IMTGs (P = 0.08). No differences were found in fasting and postprandial forearm muscle fatty acid uptake between NGT and IGT, or in IGT before and after weight loss. Discussion: The ability to switch from fat oxidation to carbohydrate oxidation after a meal is already impaired in the prediabetic state, suggesting this may be an early factor in the development toward DM2. This impaired ability to regulate fat oxidation during fasting and after a meal (impaired metabolic flexibility) can be (partly) reversed by weight loss.     

Igf Signaling is Required for Cardiomyocyte Proliferation during Zebrafish Heart Development and Regeneration

Unlike its mammalian counterpart, the adult zebrafish heart is able to fully regenerate after severe injury. One of the most important events during the regeneration process is cardiomyocyte proliferation, which results in the replacement of lost myocardium. Growth factors that induce cardiomyocyte proliferation during zebrafish heart regeneration remain to be identified. Signaling pathways important for heart development might be reutilized during heart regeneration. IGF2 was recently shown to be important for cardiomyocyte proliferation and heart growth during mid-gestation heart development in mice, although its role in heart regeneration is unknown. We found that expression of igf2b was upregulated during zebrafish heart regeneration. Following resection of the ventricle apex, igf2b expression was detected in the wound, endocardium and epicardium at a time that coincides with cardiomyocyte proliferation. Transgenic zebrafish embryos expressing a dominant negative form of Igf1 receptor (dn-Igf1r) had fewer cardiomyocytes and impaired heart development, as did embryos treated with an Igf1r inhibitor. Moreover, inhibition of Igf1r signaling blocked cardiomyocyte proliferation during heart development and regeneration. We found that Igf signaling is required for a subpopulation of cardiomyocytes marked by gata4:EGFP to contribute to the regenerating area. Our findings suggest that Igf signaling is important for heart development and myocardial regeneration in zebrafish.     

Glia maintain follower neuron survival during Drosophila CNS development

While survival of CNS neurons appears to depend on multiple neuronal and non-neuronal factors, it remains largely unknown how neuronal survival is controlled during development. Here we show that glia regulate neuronal survival during formation of the Drosophila embryonic CNS. When glial function is impaired either by mutation of the glial cells missing gene, which transforms glia toward a neuronal fate, or by targeted genetic glial ablation, neuronal death is induced non-autonomously. Pioneer neurons, which establish the first longitudinal axon fascicles, are insensitive to glial depletion whereas the later extending follower neurons die. This differential requirement of neurons for glia is instructive in patterning and links control of cell number with axon guidance during CNS development.