Developmental Expression of Kv Potassium Channels at the Axon Initial Segment of Cultured Hippocampal Neurons

Axonal outgrowth and the formation of the axon initial segment (AIS) are early events in the acquisition of neuronal polarity. The AIS is characterized by a high concentration of voltage-dependent sodium and potassium channels. However, the specific ion channel subunits present and their precise localization in this axonal subdomain vary both during development and among the types of neurons, probably determining their firing characteristics in response to stimulation. Here, we characterize the developmental expression of different subfamilies of voltage-gated potassium channels in the AISs of cultured mouse hippocampal neurons, including subunits Kv1.2, Kv2.2 and Kv7.2. In contrast to the early appearance of voltage-gated sodium channels and the Kv7.2 subunit at the AIS, Kv1.2 and Kv2.2 subunits were tethered at the AIS only after 10 days in vitro. Interestingly, we observed different patterns of Kv1.2 and Kv2.2 subunit expression, with each confined to distinct neuronal populations. The accumulation of Kv1.2 and Kv2.2 subunits at the AIS was dependent on ankyrin G tethering, it was not affected by disruption of the actin cytoskeleton and it was resistant to detergent extraction, as described previously for other AIS proteins. This distribution of potassium channels in the AIS further emphasizes the heterogeneity of this structure in different neuronal populations, as proposed previously, and suggests corresponding differences in action potential regulation.

Glycosylation differences between the normal and pathogenic prion protein isoforms

Prion protein consists of an ensemble of glycosylated variants or glycoforms. The enzymes that direct oligosaccharide processing, and hence control the glycan profile for any given glycoprotein, are often exquisitely sensitive to other events taking place within the cell in which the glycoprotein is expressed. Alterations in the populations of sugars attached to proteins can reflect changes caused, for example, by developmental processes or by disease. Here we report that normal (PrPC) and pathogenic (PrPSc) prion proteins (PrP) from Syrian hamsters contain the same set of at least 52 bi-, tri-, and tetraantennary N-linked oligosaccharides, although the relative proportions of individual glycans differ. This conservation of structure suggests that the conversion of PrPC into PrPSc is not confined to a subset of PrPs that contain specific sugars. Compared with PrPC, PrPSc contains decreased levels of glycans with bisecting GlcNAc residues and increased levels of tri- and tetraantennary sugars. This change is consistent with a decrease in the activity of N-acetylglucosaminyltransferase III (GnTIII) toward PrPC in cells where PrPSc is formed and argues that, in at least some cells forming PrPSc, the glycosylation machinery has been perturbed. The reduction in GnTIII activity is intriguing both with respect to the pathogenesis of the prion disease and the replication pathway for prions.

Characterization and developmental patterns of telomerase expression in plants

Telomerase activity is developmentally regulated in mammals. Here we examine telomerase activity in plants, whose development differs in fundamental ways from that of animals. Using a modified version of the telomere repeat amplification protocol (TRAP) assay, we detected an activity in extracts from carrots, cauliflower, soybean, Arabidopsis, and rice with all the characteristics expected for a telomerase synthesizing the plant telomere repeat sequence TTTAGGG. The activity was dependent on RNA and protein components, required dGTP, dATP, and dTTP, but not dCTP, and generated products with a seven nucleotide periodicity. Telomerase activity was abundant in cauliflower meristematic tissue and undifferentiated cells from Arabidopsis, soybean, and carrot suspension cultures, but was low or not detectable in a sampling of differentiated tissues from mature plants. Telomerase from cauliflower meristematic tissues exhibited relaxed DNA sequence requirements, which might reflect the capacity to form telomeres on broken chromosomes in vivo. The dramatic differences in telomerase expression and their correlation with cellular proliferation capacity mirror changes in human telomerase levels during differentiation and immortalization. Hence, telomerase activation appears to be a conserved mechanism involved in conferring long-term proliferation capacity.

Delineating developmental and metabolic pathways in vivo by expression profiling using the RIKEN set of 18,816 full-length enriched mouse cDNA arrays

We have systematically characterized gene expression patterns in 49 adult and embryonic mouse tissues by using cDNA microarrays with 18,816 mouse cDNAs. Cluster analysis defined sets of genes that were expressed ubiquitously or in similar groups of tissues such as digestive organs and muscle. Clustering of expression profiles was observed in embryonic brain, postnatal cerebellum, and adult olfactory bulb, reflecting similarities in neurogenesis and remodeling. Finally, clustering genes coding for known enzymes into 78 metabolic pathways revealed a surprising coordination of expression within each pathway among different tissues. On the other hand, a more detailed examination of glycolysis revealed tissue-specific differences in profiles of key regulatory enzymes. Thus, by surveying global gene expression by using microarrays with a large number of elements, we provide insights into the commonality and diversity of pathways responsible for the development and maintenance of the mammalian body plan.

Morphological innovation and developmental genetics

How do the actions of individual genes contribute to the complex morphologies of animals and plants? How widespread are these genes taxonomically? How many genes are involved in the morphological differences observed between species, and can we identify them? To what extent can empirical data and theory be reconciled? We provide an overview of some recent attempts to answer these questions, answers that have taken us to the threshold of understanding the mechanistic basis and evolutionary factors that underlie morphological innovation.

Analysis of Cell Division and Elongation Underlying the Developmental Acceleration of Root Growth in Arabidopsis thaliana1

To investigate the relation between cell division and expansion in the regulation of organ growth rate, we used Arabidopsis thaliana primary roots grown vertically at 20°C with an elongation rate that increased steadily during the first 14 d after germination. We measured spatial profiles of longitudinal velocity and cell length and calculated parameters of cell expansion and division, including rates of local cell production (cells mm−1 h−1) and cell division (cells cell−1 h−1). Data were obtained for the root cortex and also for the two types of epidermal cell, trichoblasts and atrichoblasts. Accelerating root elongation was caused by an increasingly longer growth zone, while maximal strain rates remained unchanged. The enlargement of the growth zone and, hence, the accelerating root elongation rate, were accompanied by a nearly proportionally increased cell production. This increased production was caused by increasingly numerous dividing cells, whereas their rates of division remained approximately constant. Additionally, the spatial profile of cell division rate was essentially constant. The meristem was longer than generally assumed, extending well into the region where cells elongated rapidly. In the two epidermal cell types, meristem length and cell division rate were both very similar to that of cortical cells, and differences in cell length between the two epidermal cell types originated at the apex of the meristem. These results highlight the importance of controlling the number of dividing cells, both to generate tissues with different cell lengths and to regulate the rate of organ enlargement.

Targeted disruption of the mouse beta1-adrenergic receptor gene: developmental and cardiovascular effects.

At least three distinct beta-adrenergic receptor (beta-AR) subtypes exist in mammals. These receptors modulate a wide variety of processes, from development and behavior, to cardiac function, metabolism, and smooth muscle tone. To understand the roles that individual beta-AR subtypes play in these processes, we have used the technique of gene targeting to create homozygous beta 1-AR null mutants (beta 1-AR -/-) in mice. The majority of beta 1-AR -/- mice die prenatally, and the penetrance of lethality shows strain dependence. Beta l-AR -/- mice that do survive to adulthood appear normal, but lack the chronotropic and inotropic responses seen in wild-type mice when beta-AR agonists such as isoproterenol are administered. Moreover, this lack of responsiveness is accompanied by markedly reduced stimulation of adenylate cyclase in cardiac membranes from beta 1-AR -/- mice. These findings occur despite persistent cardiac beta 2-AR expression, demonstrating the importance of beta 1-ARs for proper mouse development and cardiac function, while highlighting functional differences between beta-AR subtypes.

Phenotypic variations among paternal centrosomes expressed within the zygote as disparate microtubule lengths and sperm aster organization: correlations between centrosome activity and developmental success.

This study describes a paternal effect on sperm aster size and microtubule organization during bovine fertilization. Immunocytochemistry using tubulin antibodies quantitated with confocal microscopy was used to measure the diameter of the sperm aster and assign a score (0-3) based on the degree of radial organization (0, least organized; 3, most organized). Three bulls (A-C) were chosen based on varying fertility (A, lowest fertility; C, highest fertility) as assessed by nonreturn to estrus after artificial insemination and in vitro embryonic development to the blastocyst stage. The results indicate a statistically significant bull-dependent difference in diameter of the sperm aster and in the organization of the sperm astral microtubules. Insemination from bull A resulted in an average sperm aster diameter of 101.4 microm (76.3% of oocyte diameter). This significantly differs (P < or = 0.0001) from the average sperm aster diameters produced after inseminations from bull B (78.2 microm; 60.8%) or bull C (77.9 microm; 57.8%), which themselves displayed no significant differences. The degree of radial organization of the sperm aster was also bull-dependent. Sperm asters organized by bull A-derived sperm had an average quality score of 1.8, which was higher than that of bull B (1.4; P < or = 0.0005) or bull C (1.2; P < or = 0.0001). Results with bulls B and C were also significantly different (P < or = 0.025). These results indicate that the paternally derived portion of the centrosome varies among males and that this variation affects male fertility, the outcome of early development, and, therefore, reproductive success.

Systemic monocyte activation levels and developmental milestone attainment in HIV-infected infants initiating antiretroviral therapy

Thesis (Master's)--University of Washington, 2016-06

Establishment of metanephros transplantation in mice highlights contributions by both nephrectomy and pregnancy to developmental progression

Background: It has been demonstrated that embryonic kidneys (metanephroi) xenotransplanted into the omentum of adult recipients continue to develop and display immune protection due to their more nave immune presentation. To date, this has been achieved using rat, pig and human metanephroi, with unilateral nephrectomy (UNX) of recipient rats a requisite of renal development. The aim of this study was to adapt this approach for use in mice and examine the parameters affecting successful onward development in this species. Methods: Metanephroi at embryonic age (E) 13.5 were transplanted either onto the body wall, abdominal fat pads or omentum of recipient isogenic C57/Bl6 mice using either sutures or polyglycolic acid mesh. Having established greatest success with polyglycolic acid mesh on the body wall, E12.5 and 15.5 days metanephroi from C57/Bl6 mice were then transplanted onto the body wall of control (non-pregnant non-UNX), UNX or 12.5 days post-coitum pregnant isogenic recipients. After 7 days, implanted tissue was harvested and examined using histology and immunohistochemistry for markers of renal maturation. The mean number of S-shaped bodies and glomeruli per section were recorded and statistically analysed for significant differences between all recipient groups and untransplanted metanephroi. The degree of development was scored qualitatively. Results: Transplanted E12.5 metanephroi developed S-shaped bodies and glomeruli in all recipient groups, although there were statistically higher numbers of S-shaped bodies in UNX (n = 2) and pregnant recipients (n = 9) than in control recipients (n = 4). Continued development, as indicated by mature vascularized glomeruli, was only observed in those E15.5 metanephroi transplanted into pregnant recipients (n = 11) with a 15.5-fold increase in S-shaped bodies and 4-fold increase in glomeruli compared with control transplants (n = 12). Conclusions: We have successfully established metanephros transplantation in mice and demonstrated enhancement of onward development of E12.5 metanephroi in response to both pregnancy and UNX. Using E15.5 metanephroi, continued development only occurred in pregnant recipients, implying pregnancy provides an environment conducive to continued organogenesis. This murine assay, when coupled with transgenically-tagged strains of mice, will allow the investigation of the relative contribution of donor and recipient cells to this process. Copyright (C) 2005 S. Karger AG, Basel.

The functional impact of developmental co-ordination disorder during adolescence and early adult life

PURPOSE: The purpose of this study was to increase the understanding of the functional impact that coordination problems have during adolescence and early adult life. In particular, this study aimed to investigate the impact coordination deficits have on day-to-day functioning, activity levels, self-concept with respect to coordination, leisure pursuits, occupational types, accidents and injuries, as well as experiences learning to drive. RELEVANCE: This study may enable clinicians to identify at risk situations, such that appropriate prevention and targeting of treatment can occur. SUBJECTS: The participants involved in this study comprised two groups; 40 subjects previously diagnosed with DCD, and their matched controls. METHODS: Participants were initially contacted by mail for their consent to the study. Consenting participants were then contacted via telephone, and interviewed. ANALYSES: Data analysis was performed using SPSS. Chi squared analysis and Mann Whitney U test was also used to compare groups. RESULTS: During both age periods, the number of DCD subjects participating in sport was significantly less than the number of controls. Although in the 12-14 years age category, the two groups displayed similar results for the type of sport chosen, the 18 – 20 years age group, showed significant differences, with the number of DCD subjects participating in High level coordination activities, being significantly less than controls. Self-perception with respect to coordination was also significantly different amongst groups with more DCD subjects, having perceived themselves as being clumsy. Similarly, a significantly greater number of DCD subjects admitted to tripping over themselves regularly. Some differences have also been noted in the experiences of subjects learning to drive. First, the number of DCD subjects, who had difficulties learning to drive was significantly greater than controls. Second, a much greater number of Control subjects, compared to DCD subjects were successful in obtaining drivers license. Finally, also of interest is the 58% of DCD subjects who have experienced an accident whilst driving, compared to the 35% of controls. The last result of this study was that whilst there was no significant difference between groups, in the number of broken bones, dislocated joints, sprain, burns, stitches, or other significant injuries, the number of control subjects suffering muscle strains was significantly greater than the number of DCD subjects. CONCLUSION: The results of this study indicate that DCD has many implications on day-to-day functioning, both in adolescence and early adulthood. Findings have shown despite the significant sensory-motor deficits displayed by DCD subjects, the impact that this has on day-to-day functioning may be reduced by lifestyle modification.

Symptoms of hyperactivity and inattention can mediate deficits of postural stability in developmental dyslexia

DDevelopmental dyslexia is a reading disorder associated with impaired postural control. However, such deficits are also found in attention deficit hyperactivity disorder (ADHD), which is present in a substantial subset of dyslexia diagnoses. Very few studies of balance in dyslexia have assessed ADHD symptoms, thereby motivating the hypothesis that such measures can account for the group differences observed. In this study, we assessed adults with dyslexia and similarly aged controls on a battery of cognitive, literacy and attention measures, alongside tasks of postural stability. Displacements of centre of mass to perturbations of posture were measured in four experimental conditions using digital optical motion capture. The largest group differences were obtained in conditions where cues to the support surface were reduced. Between-group differences in postural sway and in sway variability were largely accounted for by co-varying hyperactivity and inattention ratings, however. These results therefore suggest that postural instability in dyslexia is more strongly associated with symptoms of ADHD than to those specific to reading impairment.

Impaired balance in developmental dyslexia? A meta-analysis of the contending evidence

Background: Developmental dyslexia is typically defined by deficits in phonological skills, but it is also associated with anomalous performance on measures of balance. Although balance assessments are included in several screening batteries for dyslexia, the association between impairments in literacy and deficits in postural stability could be due to the high co-occurrence of dyslexia with other developmental disorders in which impairments of motor behaviour are also prevalent. Methods: We identified 17 published studies that compared balance function between dyslexia and control samples and obtained effect-sizes for each. Contrast and association analyses were used to quantify the influence of hypothesised moderator variables on differences in effects across studies. Results: The mean effect-size of the balance deficit in dyslexia was .64 (95% CI = .44-.78) with heterogeneous findings across the population of studies. Probable co-occurrence of other developmental disorders and variability in intelligence scores in the dyslexia samples were the strongest moderator variables of effect-size. Conclusions: Balance deficits are associated with dyslexia, but these effects are apparently more strongly related to third variables other than to reading ability. Deficits of balance may indicate increased risk of developmental disorder, but are unlikely to be uniquely associated with dyslexia.

Leadership development: the role of developmental readiness, personality dispositions, and individual values

Increased awareness of the crucial role of leadership as a competitive advantage for organisations (McCall, 1998; Petrick, Scherer, Brodzinski, Quinn, & Ainina, 1999) has led to billions spent on leadership development programmes and training (Avolio & Hannah, 2008). However, research reports confusing and contradictory evidence regarding return on investment and developmental outcomes, and a lot of variance has been observed across studies (Avolio, Reichard, Hannah, Walumbwa, & Chan, 2009). The purpose of this thesis is to understand the mechanisms underlying this variability in leadership development. Of the many factors at play in the process, such as programme design and delivery, organisational support, and perceptions of relevance (Mabey, 2002; Day, Harrison, & Halpin, 2009), individual differences and characteristics stand out. One way in which individuals differ is in their Developmental Readiness (DR), a concept recently introduced in the literature that may well explain this variance and which has been proposed to accelerate development (Avolio & Hannah, 2008, 2009). Building on previous work, DR is introduced and conceptualised somewhat differently. In this study, DR is construed of self-awareness, self-regulation, and self-motivation, proposed by Day (2000) to be the backbones of leadership development. DR is suggested to moderate the developmental process. Furthermore, personality dispositions and individual values are proposed to be precursors of DR. The empirical research conducted uses a pre-test post-test quasi-experimental design. Before conducting the study, though, both a measure of Developmental Readiness and a competency profiling measure are tested in two pilot studies. Results do not find evidence of a direct effect of leadership development programmes on development, but do support an interactive effect between DR and leadership development programmes. Personality dispositions Agreeableness, Conscientiousness, and Openness to Experience and value orientations Conservation, Open, and Closed Orientation are found to significantly predict DR. Finally, the theoretical and practical implications of findings are discussed.