Regulation and function of myocyte enhancer factor 2 (MEF2) in myogenic and neurogenic cells

"In eukaryotic organisms, regulation of gene expression at the transcriptional level is a fundamental mechanism which is evolutionary conserved in all cellular systems. It tightly regulates the diversification in expression patterns of genes and proteins required for biological complexity and function. Transcriptional regulation is mediated by the physical interaction between transcription factors and specific cis-acting regulatory elements in gene promoter regions. Myocyte enhancer factor 2 (MEF2) is a transcription factor highly conserved in eukaryotes involved in differentiation, proliferation, and survival/apoptosis. The MEF2 gene family (MEF2 A-D) regulates development of various tissue types including muscle (skeletal, cardiac, and smooth muscle), bone, lymphocytes and neurons. The regulation of MEF2 activity is complex, and is coordinated at multiple levels including posttranslational modifications and protein-protein interaction, that together modulate MEF2's function. Conversely dysregulation of MEF2 activity underlies pathogenesis in muscle and neuronal cells. MEF2 is responsive to various signaling cascades which provide a way for distinct stimuli to differentially regulate MEF2-dependent gene expression. It is known that phosphorylation by kinases is an important process through which the activity of MEF2 is up- or down-regulated. Several kinases (p38MAPK, CDK5, PKC, and ERK5) have been linked to muscle and neuronal development, as well as survival in part due to their modulation of MEF2 function. In addition MEF2 is known to be targeted by co-repressors, such as class Ila histone deacetylases (HDAC 4, 5, 7 and 9). This interaction contributes to repression of MEF2-dependent gene expression. Although MEF2 family members are critical regulators of skeletal muscle differentiation and cardiovascular function their individual roles within nervous system are less well characterized. In current studies, we attempted to investigate the posttranslational regulation of MEF2 both in myogenic and neurogenic cells. The cAMP/protein kinase A (PKA) signaling pathway regulates a variety of cellular functions and numerous important biological processes. Many of the effects of cAMP/PKA are mediated via changes in gene expression. We have previously documented that cAMP/PKA signaling negatively regulates MEF2 activity and inhibits myogenes1s by direct phosphorylation of MEF2 proteins. MEF2 A-D are highly expressed in multiple regions of the brain, including cortex, cerebellum, and hippocampus. Distinct patterns of expression during pre- and postnatal development suggest specific functions for MEF2 proteins at different stages of neuronal maturation and survival. However, whether the cAMP/PKA pathway inhibits MEF2 mediated gene expression in neurons was unclear. Recently, we evaluated whether cAMP/PKA signaling can inhibit MEF2-dependent gene expression directly or indirectly and survival role of MEF2D in hippocampal neurons. We performed survival assays to determine PKA effects in neuronal cells. We observed that experimental induction of cAMP/PKA signaling promotes apoptosis in primary hippocampal neurons as indicated by TUNEL and FACS analysis. Luciferase reporter gene assays revealed that PKA potently represses MEF2D trans-activation properties in neurons. Kruppel-like factor 6 (KLF6) was identified as a key transcriptional target of MEF2 in hippocampal neurons and siRNA mediated knockdown of KLF6 expression promotes neuronal cell death and also antagonizes the pro-survival role of MEF2D. In this study, we found that cAMP/PKA signaling represses KLF6 transcriptional activity and induce neuronal apoptosis by phosphorylating MEF2 and preventing HDAC4 export from the nucleus. These observations characterize a potent inhibitory effect of PKA on the transactivation properties of MEF2D leading to repression of KLF6 expression and compromising neuronal survival (Chapter III). Next, we were interested to determine how MEF2 controls diverse cellular processes in muscle development in the presence/absence of cofactors. Tandem Affinity Purification (TAP) combined with mass spectrometry analysis was employed in the current studies to identify MEF2 interacting cofactors. We identified Strawberry notch 1(Sbno1) as a novel interacting factor of MEF2D which is known to be downstream effecter of Notch signaling. Notch signaling is known to block the expression and activity of myogenic factors such as MEF2s. We therefore characterized the mechanism of myogenic inhibition by Notch-Sbnol signaling. C2C 12 myoblasts provide a useful in vitro model to study skeletal muscle differentiation. We determined the expression patterns, by western blot analysis, of muscle specific gene expression during myogenesis. Sbno1 represses MEF2 transactivation properties and plays a critical role in inhibition of skeletal muscle differentiation. Immunocytochemistry analysis suggests that Notch-Sbno1 might be involved in maintaining the ""reserve"" cell population. Our data suggested that protein-protein interactions between Sbno1 and MEF2D result in interference with the function of myogenic factors (Chapter IV). MEF2D is a known transcriptional regulator of muscle differentiation. Current studies identified KLF6 as a novel MEF2D target gene which is involved in hippocampal neuronal survival. TGF? has been reported as a potent inhibitor of myogenic differentiation by maintaining myoblasts in a proliferative state (undifferentiated myoblasts). Further, TGF? and KLF6 regulate each other's expression in other cell types. We therefore sought to investigate the possible role of KLF6 in a myogenic context and assessed whether TGF? activation regulates KLF6 protein expression and function in a MEF2 dependent manner in C2C12 myoblasts (Chapter V). Taken together, these studies indicate that differential activation of signaling cascades and co-factors regulate the MEF2 transcriptional complex which has profound effects on gene expression in myogenic and neurogenic cells.

Autoimmune pancreatitis presenting as obstructive jaundice

A 71 years cachexic male presented with sign symptoms of biliary tract obstruction. There was a large mass in the head of pancreases with raised CA 19.9. But elevated serum lipase raised the suspicion of paocreatitis. Elevated immunoglobu­lin IgG4 confmned this case as a auto immune aetiology. Initially there was much difficulty to differentiate auto immune pancreatitis from pancreatic carcinoma but after successful stenting and a course of corticosteroids, patient improved dramatically along with nonnalisation of all the radiological, bio-chemical and immunological parameters

Use of Recombinant Human Erythropoietin in Renal Anemia in Children

Erythropoietin is a hormone highly effective as like as natural erythropoietin to maintain target hemoglobin and hematocrit level in renal anemia. Its advantage over blood transfusion has been proved by improving the quality of life and decreasing morbidity and mortality in ESRD patients. Effectiveness of r-erythropoietin depends on absences of infection, inflammation and vitamin deficiency and iron status. Iron supplementation is needed before r-erythropoietin administration and sub-cutaneous rout is better in renal anemia because of slow and sustained releases of r-erythropoietin from the site of administration. Target hemoglobin level is 11-12.5 gm/dl and hematocrit is 33% which can be achieved by this hormone therapy. Key words- Recombinant erythropoietin, renal anemia, end stage renal disease.DOI: 10.3329/bsmmuj.v2i1.3713 BSMMU J 2009; 2(1): 50-53 &nbsp

Acceptability and short-term complications of PPIUCD

Background: Intrauterine contraceptive device (IUCD) is an effective form of long-acting reversible contraceptive (LARC). Postpartum IUCD insertion is labelled when IUCD is inserted within 10 minutes to 48 hours of expulsion of placenta. assess the acceptability and short-term complications of postpartum intrauterine contraception device insertion in tertiary care hospital of Bangladesh. The aim of the study was to assess the evaluation of factors associated with acceptability of post-partum intrauterine contraceptive device (PPIUCD). Methods: This was a prospective observational study was conducted at department of obstetrics and gynecology, Dhaka Medical College Hospital (DMCH). Results: Out of 360 eligible counselled postpartum patients, 48 (13.3%) women underwent PPIUCD insertion. Acceptance of PPIUCD was higher in the age group of 25-30 years (43.75%), having former health counselling about PPIUCD (70.8%), multipara (68.75%). The commonest complications were missing thread (8.3%) followed by lower abdominal pain (6.25%), irregular per vaginal bleeding (4.2%). Conclusions: PPIUCD is not very acceptable in our set up but it is a safe, highly effective method of contraception with very few side effects and no major complications and contraindications. The acceptability of PPIUCD can be increased with antenatal counselling and institutional delivery

NRXN1 deletion and exposure to methylmercury increase astrocyte differentiation by different notch-dependent transcriptional mechanisms

Controversial evidence points to a possible involvement of methylmercury (MeHg) in the etiopathogenesis of autism spectrum disorders (ASD). In the present study, we used human neuroepithelial stem cells from healthy donors and from an autistic patient bearing a bi-allelic deletion in the gene encoding for NRXN1 to evaluate whether MeHg would induce cellular changes comparable to those seen in cells derived from the ASD patient. In healthy cells, a subcytotoxic concentration of MeHg enhanced astroglial differentiation similarly to what observed in the diseased cells (N1), as shown by the number of GFAP positive cells and immunofluorescence signal intensity. In both healthy MeHg-treated and N1 untreated cells, aberrations in Notch pathway activity seemed to play a critical role in promoting the differentiation toward glia. Accordingly, treatment with the established Notch inhibitor DAPT reversed the altered differentiation. Although our data are not conclusive since only one of the genes involved in ASD is considered, the results provide novel evidence suggesting that developmental exposure to MeHg, even at subcytotoxic concentrations, induces alterations in astroglial differentiation similar to those observed in ASD

ANTIHYPERGLYCEMIC AND ANTINOCICEPTIVE ACTIVITY EVALUATION OF ‘KHOYER’ PREPARED FROM BOILING THE WOOD OF ACACIA CATECHU IN WATER

‘Khoyer’ is prepared by boiling the wood of Acacia catechu in water and then evaporating the resultant brew. The resultant hard material is powdered and chewed with betel leaves and lime with or without tobacco by a large number of the people of Bangladesh as an addictive psycho-stimulating and euphoria-inducing formulation. There are folk medicinal claims that khoyer helps in the relief of pain and is also useful to diabetic patients to maintain normal sugar levels. Thus far no scientific studies have evaluated the antihyperglycemic and antinociceptive effects of khoyer. The present study was carried out to evaluate the possible glucose tolerance efficacy of methanolic extracts of khoyer using glucose-induced hyperglycemic mice, and antinociceptive effects with acetic acid-induced gastric pain models in mice. In antihyperglycemic activity tests, the extract at different doses was administered one hour prior to glucose administration and blood glucose level was measured after two hours of glucose administration (p.o.) using glucose oxidase method. The statistical data indicated the significant oral hypoglycemic activity on glucose-loaded mice at all doses of the extracts tested. Maximum anti-hyperglycemic activity was shown at 400 mg extract per kg body weight, which was slightly less than that of a standard drug, glibenclamide (10 mg/kg body weight). In antinociceptive activity tests, the extract also demonstrated a dose-dependent significant reduction in the number of writhings induced in mice through intraperitoneal administration of acetic acid. Maximum antinociceptive activity was observed at a dose of 400 mg extract per kg body weight, which was greater than that of a standard antinociceptive drug, aspirin, when administered at a dose of 400 mg per kg body weight. The results validate the folk medicinal use of the plant for reduction of blood sugar in diabetic patients as well as the folk medicinal use for alleviation of pain

Ionanofluid flow through a triangular grooved microchannel heat sink: Thermal heightening

With recent technological advances, thermal transport from different electronic and electrical devices is the most vital concern. The microchannel heat sink (MCHS) of liquid cooling is a useful device to remove over thermal load. Ionanofluid is a brand new and super potential cooling fluid for its ionic conductivity, non-flammability, negligible volatility, and high-level heat stability. In this research, the ionanofluid's velocity and thermal field characteristics through a triangular grooved MCHS are investigated using numerical tools. The combination of ionic liquid (IL) 1-Butyl-3-methylimidazolium Bis(trifluoromethanesulfonyl)imide [C4mim]NTf2 and propylene glycol (PG) is used as base fluid whereas graphene (G) and single-walled carbon nanotube (SWCNT) are chosen as hybrid nanoparticles to make the working ionanofluid. The governing equations of nonlinear partial differential equations describing the physical phenomena along with proper border settings are resolved by applying the finite element method (FEM). Different ratios of hybrid nanoparticles (G: SWCNT) like (1: 0, 1/3: 2/3, 1/2: 1/2, 2/3: 1/3, 0: 1) are suspended in the base fluid mixture. In addition, the base fluid mixture is assumed in different combinations of (IL: PG) as (100: 0, 50: 50, 0: 100). The numerical results are displayed in the forms of streamlines, isothermal lines, and rate of thermal transfer for the pertinent parameters namely forced convection (Re = 100–900) and solid concentration (φ = 0.001–0.05). Also, pressure drop, field synergy number, relative fanning friction feature, relative Nusselt number, and temperature enhancement efficiency are calculated. The results indicate that a higher heat transport rate is found using the IL-based ionanofluid with the highest solid concentration. Moreover, the higher forced convection enhances the thermal efficiency of MCHS. Two linear regression equations along with very good correlation coefficients have been derived from the numerical results

Nexus between Economic Policy Uncertainty and Renewable Energy Consumption in BRIC Nations: The Mediating Role of Foreign Direct Investment and Financial Development

In recent literature, the impact of economic policy uncertainty (EPU) on macro aspects have been investigated, but the aspect of energy, precisely renewable energy still to explore. The motivation of the study is to produce fresh evidence regarding the nexus between EPU and renewable energy consumption (REC) with the mediating role of forcing direct investment (FDI) and financial development (FD) in BRIC nations for the period 1997q1–2018q4. The study applied unit root tests following Ng-Perron and Zivot and Andrews for detecting variable’s stationary properties. The long-run cointegration was evaluated by implementing Bayer, Hanck combined the cointegration test, Bound testing approach, and tBDM test. Both linear and non-linear ARDL were implemented to evaluate long-run and short-run shocks, and directional causality was assessed through a non-granger causality test. Furthermore, the study implemented robustness by implementing fully-modified OLS, dynamic OLS, and canonical cointegrating regression (CCR). Unit root test established the variables are stationary after the first difference; moreover, the Bayer and Hanck cointegration test confirmed the long-run association between EPU, FD, FD, and REC in BRIC nations. Accruing to ARDL estimation, adverse effects running from EPU to REC both in the long run and short run. Furthermore, the positive statistically significant linkage revealed for FDI and FD to REC implies that clean energy integration could be augmented with continual inflows of FDI and development of the financial sector. Model estimation with asymmetric assumption, the study documented asymmetric effects running from EPU, FDI, and FD to renewable energy consumption, especially in the long run. Finally, the directional causality revealed unidirectional causality between REC and EPU, whereas the feedback hypothesis was disclosed for FDI and REC] and FD and REC. Study findings postulated that the role of foreign direct investment and financial development is critically significant because technological advancement and capital investment augment clean energy integration through the application of renewable energy

How mechanisms of stem cell polarity shape the human cerebral cortex.

Apical-basal progenitor cell polarity establishes key features of the radial and laminar architecture of the developing human cortex. The unique diversity of cortical stem cell populations and an expansion of progenitor population size in the human cortex have been mirrored by an increase in the complexity of cellular processes that regulate stem cell morphology and behaviour, including their polarity. The study of human cells in primary tissue samples and human stem cell-derived model systems (such as cortical organoids) has provided insight into these processes, revealing that protein complexes regulate progenitor polarity by controlling cell membrane adherence within appropriate cortical niches and are themselves regulated by cytoskeletal proteins, signalling molecules and receptors, and cellular organelles. Studies exploring how cortical stem cell polarity is established and maintained are key for understanding the features of human brain development and have implications for neurological dysfunction

Autoimmune pancreatitis presenting as obstructive jaundice

A 71 years cachexic male presented with sign symptoms of biliary tract obstruction. There was a large mass in the head of pancreases with raised CA 19.9. But elevated serum lipase raised the suspicion of paocreatitis. Elevated immunoglobu­lin IgG4 confmned this case as a auto immune aetiology. Initially there was much difficulty to differentiate auto immune pancreatitis from pancreatic carcinoma but after successful stenting and a course of corticosteroids, patient improved dramatically along with nonnalisation of all the radiological, bio-chemical and immunological parameters