A protein encoded within the Down syndrome critical region is enriched in striated muscles and inhibits calcineurin signaling

The neuronal and endocrine roles of RCAN1 in health and disease

The regulator of calcineurin 1 (RCAN1) was first discovered as a gene located on human chromosome 21, expressed in neurons and overexpressed in the brains of Down syndrome individuals. Increased expression of RCAN1 has been linked with not only Down syndrome-associated pathology but also an associated neurological disorder, Alzheimer's Disease, in which neuronal RCAN1 expression is also increased. RCAN1 has additionally been demonstrated to affect other cell types including endocrine cells, with links to the pathogenesis of β-cell dysfunction in type 2 diabetes. The primary functions of RCAN1 relate to the inhibition of the phosphatase calcineurin, and to the regulation of mitochondrial function. Various forms of cellular stress such as reactive oxygen species and hyperglycaemia cause transient increases in RCAN1 expression. The short term (hours to days) induction of RCAN1 expression is generally thought to have a protective effect by regulating the expression of pro-survival genes in multiple cell types, many of which are mediated via the calcineurin/NFAT transcriptional pathway. However, strong evidence also supports the notion that chronic (weeks-years) overexpression of RCAN1 has a detrimental effect on cells and that this may drive pathophysiological changes in neurons and endocrine cells linked to Down syndrome, Alzheimer's Disease and type 2 diabetes. Here we review the evidence related to these roles of RCAN1 in neurons and endocrine cells and their relationship to these human health disorders.

RCAN-11R peptide provides immunosuppression for fully mismatched islet allografts in mice

Calcineurin inhibitors have been used for transplant therapy. However, the inhibition of calcineurin outside the immune system has a number of side effects. We previously developed a cell-permeable inhibitor of NFAT (nuclear factor of activated T cells) using the polyarginine peptide delivery system. This peptide (11R-VIVIT) selectively interferes with calcineurin-NFAT interaction without affecting the activity of calcineurin phosphatase and provides immunosuppression for fully mismatched islet allografts in mice. However, our recent study showed that 11R-VIVIT affected cell viability in vitro when it was used at higher concentration because of the VIVIT sequence. The aim of this study is to develop a safer NFAT inhibitor (RCAN-11R) that does not affect cell viability, and which is less toxic than calcineurin inhibitors. The minimal sequence of the protein family of regulators of calcineurin (RCAN) that is responsible for the inhibition of calcineurin-NFAT signaling was recently characterized. The peptide could selectively interfere with the calcineurin-NFAT interaction without affecting the activity of calcineurin phosphatase, similar to 11R-VIVIT. RCAN-11R did not affect cell viability when it was used at a higher concentration than the toxic concentration of 11R-VIVIT. RCAN-11R could therefore be useful as a therapeutic agent that is less toxic than current drugs or 11R-VIVIT.

Leucine-Rich Repeat Kinase 2 (LRRK2) Stimulates IL-1β-Mediated Inflammatory Signaling through Phosphorylation of RCAN1

Leucine-rich repeat kinase 2 (LRRK2) is a Ser/Thr kinase having mixed lineage kinase-like and GTPase domains, controlling neurite outgrowth and neuronal cell death. Evidence suggests that LRRK2 is involved in innate immune response signaling, but the underlying mechanism is yet unknown. A novel protein inhibitor of phosphatase 3B, RCAN1, is known to positively regulate inflammatory signaling through modulation of several intracellular targets of interleukins in immune cells. In the present study, we report that LRRK2 phosphorylates RCAN1 (RCAN1-1S) and is markedly up-regulated during interleukin-1β (IL-1β) treatment. During IL-1β treatment, LRRK2-mediated phosphorylation of RCAN1 promoted the formation of protein complexes, including that between Tollip and RCAN1. LRRK2 decreased binding between Tollip and IRAK1, which was accompanied by increased formation of the IRAK1-TRAF6 complex. TAK1 activity was significantly enhanced by LRRK2. Furthermore, LRRK2 enhanced transcriptional activity of NF-κB and cytokine IL-8 production. These findings suggest that LRRK2 might be important in positively modulating IL-1β-mediated signaling through selective phosphorylation of RCAN1.

Difficulty in obtaining the complete mRNA coding sequence at 5' region (5' end mRNA artifact): Causes, consequences in biology and medicine and possible solutions for obtaining the actual amino acid sequence of proteins (Review)

The known difficulty in obtaining the actual full length, complete sequence of a messenger RNA (mRNA) may lead to the erroneous determination of its coding sequence at the 5' region (5' end mRNA artifact), and consequently to the wrong assignment of the translation start codon, leading to the inaccurate prediction of the encoded polypeptide at its amino terminus. Among the known human genes whose study was affected by this artifact, we can include disco interacting protein 2 homolog A (DIP2A; KIAA0184), Down syndrome critical region 1 (DSCR1), SON DNA binding protein (SON), trefoil factor 3 (TFF3) and URB1 ribosome biogenesis 1 homolog (URB1; KIAA0539) on chromosome 21, as well as receptor for activated C kinase 1 (RACK1, also known as GNB2L1), glutaminyl‑tRNA synthetase (QARS) and tyrosyl-DNA phosphodiesterase 2 (TDP2) along with another 474 loci, including interleukin 16 (IL16). In this review, we discuss the causes of this issue, its quantitative incidence in biomedical research, the consequences in biology and medicine, and the possible solutions for obtaining the actual amino acid sequence of proteins in the post-genomics era.

Calcineurin signaling in the heart: The importance of time and place

The calcium-activated protein phosphatase, calcineurin, lies at the intersection of protein phosphorylation and calcium signaling cascades, where it provides an essential nodal point for coordination between these two fundamental modes of intracellular communication. In excitatory cells, such as neurons and cardiomyocytes, that experience rapid and frequent changes in cytoplasmic calcium, calcineurin protein levels are exceptionally high, suggesting that these cells require high levels of calcineurin activity. Yet, it is widely recognized that excessive activation of calcineurin in the heart contributes to pathological hypertrophic remodeling and the progression to failure. How does a calcium activated enzyme function in the calcium-rich environment of the continuously contracting heart without pathological consequences? This review will discuss the wide range of calcineurin substrates relevant to cardiovascular health and the mechanisms calcineurin uses to find and act on appropriate substrates in the appropriate location while potentially avoiding others. Fundamental differences in calcineurin signaling in neonatal verses adult cardiomyocytes will be addressed as well as the importance of maintaining heterogeneity in calcineurin activity across the myocardium. Finally, we will discuss how circadian oscillations in calcineurin activity may facilitate integration with other essential but conflicting processes, allowing a healthy heart to reap the benefits of calcineurin signaling while avoiding the detrimental consequences of sustained calcineurin activity that can culminate in heart failure.

Skeletal muscle action of estrogen receptor α is critical for the maintenance of mitochondrial function and metabolic homeostasis in females

Impaired estrogen receptor α (ERα) action promotes obesity and metabolic dysfunction in humans and mice; however, the mechanisms underlying these phenotypes remain unknown. Considering that skeletal muscle is a primary tissue responsible for glucose disposal and oxidative metabolism, we established that reduced ERα expression in muscle is associated with glucose intolerance and adiposity in women and female mice. To test this relationship, we generated muscle-specific ERα knockout (MERKO) mice. Impaired glucose homeostasis and increased adiposity were paralleled by diminished muscle oxidative metabolism and bioactive lipid accumulation in MERKO mice. Aberrant mitochondrial morphology, overproduction of reactive oxygen species, and impairment in basal and stress-induced mitochondrial fission dynamics, driven by imbalanced protein kinase A-regulator of calcineurin 1-calcineurin signaling through dynamin-related protein 1, tracked with reduced oxidative metabolism in MERKO muscle. Although muscle mitochondrial DNA (mtDNA) abundance was similar between the genotypes, ERα deficiency diminished mtDNA turnover by a balanced reduction in mtDNA replication and degradation. Our findings indicate the retention of dysfunctional mitochondria in MERKO muscle and implicate ERα in the preservation of mitochondrial health and insulin sensitivity as a defense against metabolic disease in women.

Down syndrome critical region 1 positively correlates with angiogenesis in hypopharyngeal cancer

Hypopharyngeal carcinoma has one of the highest mortality rates of head and neck cancer, therefore, the identification of markers associated with the pathogenesis and development of hypopharyngeal cancer is critical. Down syndrome critical region 1 (DSCR1) is associated with carcinogenesis and tumor growth in several types of malignancy. Activation of the vascular endothelial growth factor (VEGF) signaling pathway upregulates DSCR1. The aims of the present study were to determine the expression levels of DSCR1 and VEGF‑C in hypopharyngeal cancer, and investigate the association between DSCR1 and angiogenesis in the disease. Tissue samples from 94 cases of pathologically confirmed hypopharyngeal squamous cell carcinoma were collected. The mRNA levels of DSCR1 and VEGF‑C in cancerous and paracancerous tissues were examined using semi‑quantitative reverse transcription‑polymerase chain reaction. Microvessel density (MVD) was counted, according to the number of cluster of differentiation 34‑positive cells. Spearman's correlation analysis was utilized to analyze the association between DSCR1 and angiogenesis. The relative mRNA expression levels of DSCR1 and VEGF‑C, and the MVD were significantly increased in the cancerous tissue samples from the patients with hypopharyngeal cancer, compared with the paracancerous tissue samples from these patients. Higher levels of DSCR1 and increased MVD were associated with poorly differentiated tumors and lymph node metastasis. The mRNA expression levels of DSCR1 were positively correlated with the mRNA levels of VEGF‑C in the cancerous tissues. The protein expression levels of DSCR1 were also positively correlated with MVD in the cancerous tissues. The results indicated that DSCR1 is involved in tumor angiogenesis in patients with hypopharyngeal cancer, and is closely associated with the progression of the disease.

RCANs regulate the convergent roles of NFATc1 in bone homeostasis

Activation of calcineurin-dependent nuclear factor of activated T cells c1 (NFATc1) is convergent for normal bone homeostasis. NFATc1 regulates both osteoclastogenesis and osteoblastogenesis. Here we investigated the roles of regulator of calcineurin (RCAN) genes in bone homeostasis. RCANs function as potent physiological inhibitors of calcineurin. Overexpression of RCANs in osteoclast precursor cells attenuated osteoclast differentiation, while their overexpression in osteoblasts enhanced osteoblast differentiation and function. Intriguingly, opposing effects of RCANs in both cell types were shown by blocking activation of the calcineurin-NFATc1 pathway. Moreover, the disruption of RCAN1 or RCAN2 in mice resulted in reduced bone mass, which is associated with strongly increased osteoclast function and mildly reduced osteoblast function. Taken together, RCANs play critical roles in bone homeostasis by regulating both osteoclastogenesis and osteoblastogenesis, and they serve as inhibitors for calcineurin-NFATc1 signaling both in vivo and in vitro.

The Proteasome and Oxidative Stress in Alzheimer's Disease

SIGNIFICANCE

Alzheimer's disease is a neurodegenerative disorder that is projected to exceed more than 100 million cases worldwide by 2050. Aging is considered the primary risk factor for some 90% of Alzheimer's cases but a significant 10% of patients suffer from aggressive, early-onset forms of the disease. There is currently no effective Alzheimer's treatment and this, coupled with a growing aging population, highlights the necessity to understand the mechanism(s) of disease initiation and propagation. A major hallmark of Alzheimer's disease pathology is the accumulation of amyloid-β (Aβ) aggregates (an early marker of Alzheimer's disease), and neurofibrillary tangles, comprising the hyper-phosphorylated microtubule-associated protein Tau. Recent Advances: Protein oxidation is frequently invoked as a potential factor in the progression of Alzheimer's disease; however, whether it is a cause or a consequence of the pathology is still being debated. The Proteasome complex is a major regulator of intracellular protein quality control and an essential proteolytic enzyme for the processing of both Aβ and Tau. Recent studies have indicated that both protein oxidation and excessive phosphorylation may limit Proteasomal processing of Aβ and Tau in Alzheimer's disease.

CRITICAL ISSUES

Thus, the Proteasome may be a key factor in understanding the development of Alzheimer's disease pathology; however, its significance is still very much under investigation.

FUTURE DIRECTIONS

Discovering how the proteasome is affected, regulated, or dysregulated in Alzheimer's disease could be a valuable tool in the efforts to understand and, ultimately, eradicate the disease. Antioxid. Redox Signal. 25, 886-901.

Relationships between Muscle Architecture of Rectus Femoris and Functional Parameters of Knee Motion in Adults with Down Syndrome

This study was designed to measure in vivo muscle architecture of the rectus femoris in adults with Down syndrome, testing possible relationships with functional parameters of the knee motion. Ten adults with Down syndrome and ten typically developed participated in the study. Pennation angle and thickness of the rectus femoris and subcutaneous layer of the thigh were measured via ultrasound imaging. Knee kinematics and electromyographic activity of the rectus femoris were recorded during free leg dropping. Muscle thickness was reduced and subcutaneous layer was thicker in persons with Down syndrome with respect to typically developed adults, but there were no differences in the pennation angle. The area of the rectus femoris EMG activity during the leg flexion was greater in Down syndrome with respect to typically developed adults. The leg movement velocity was lower in Down people than in controls, but the knee excursion was similar between the groups. Functional parameters correlated with pennation angle in the persons with Down syndrome and with muscle thickness in typically developed persons. The description of muscle architecture and the relationships between morphological and functional parameters may provide insights on the limits and the opportunities to overcome the inherent biomechanical instability in Down syndrome.

KRAS mutation leads to decreased expression of regulator of calcineurin 2, resulting in tumor proliferation in colorectal cancer

KRAS mutations occur in 30–40% of all cases of human colorectal cancer (CRC). However, to date, specific therapeutic agents against KRAS-mutated CRC have not been developed. We previously described the generation of mouse models of colon cancer with and without Kras mutations (CDX2P-G22Cre;Apc^flox/flox; LSL-Kras^G12D and CDX2P-G22Cre;Apc^flox/flox mice, respectively). Here, the two mouse models were compared to identify candidate genes, which may represent novel therapeutic targets or predictive biomarkers. Differentially expressed genes in tumors from the two mouse models were identified using microarray analysis, and their expression was compared by quantitative reverse transcription–PCR (qRT–PCR) and immunohistochemical analyses in mouse tumors and surgical specimens of human CRC, with or without KRAS mutations, respectively. Furthermore, the functions of candidate genes were studied using human CRC cell lines. Microarray analysis of 34 000 transcripts resulted in the identification of 19 candidate genes. qRT–PCR analysis data showed that four of these candidate genes (Clps, Irx5, Bex1 and Rcan2) exhibited decreased expression in the Kras-mutated mouse model. The expression of the regulator of calcineurin 2 (RCAN2) was also observed to be lower in KRAS-mutated human CRC. Moreover, inhibitory function for cancer cell proliferation dependent on calcineurin was indicated with overexpression and short hairpin RNA knockdown of RCAN2 in human CRC cell lines. KRAS mutations in CRC lead to a decrease in RCAN2 expression, resulting in tumor proliferation due to derepression of calcineurin–nuclear factor of activated T cells (NFAT) signaling. Our findings suggest that calcineurin–NFAT signal may represent a novel molecular target for the treatment of KRAS-mutated CRC.

RCAN1 deficiency protects against Salmonella intestinal infection by modulating JNK activation

OBJECTIVE

RCAN1 (regulator of calcineurin 1) has been shown to be involved in various physiological and pathological processes. However, the biological implications of RCAN1 during gastrointestinal tract infection remain unclear. In this study, we tried to determine the role of RCAN1 in acute Salmonella infectious colitis.

METHODS

Wild type and RCAN1-deficient mice or macrophages were used to characterize the impacts of RCAN1 on intestinal inflammation, inflammatory cytokines production, animal survival, and pathogen clearance following Salmonella challenge.

RESULTS

Histologic and quantitative assessments showed increased inflammation and elevated proinflammatory cytokines production in RCAN1-deficient mice. The aberrant inflammatory response was recapitulated in primary bone marrow-derived macrophages. In addition, we reveal a novel regulatory role for RCAN1 in the proinflammatory JNK signaling both in vitro and in vivo. Further analysis showed that the increased inflammation in RCAN1-deficient mice contributed to pathogen clearance and host survival.

CONCLUSIONS

The present study demonstrates that RCAN1 deficiency protects against Salmonella intestinal infection by enhancing proinflammatory JNK signaling.

A Syntenic Cross Species Aneuploidy Genetic Screen Links RCAN1 Expression to β-Cell Mitochondrial Dysfunction in Type 2 Diabetes

Type 2 diabetes (T2D) is a complex metabolic disease associated with obesity, insulin resistance and hypoinsulinemia due to pancreatic β-cell dysfunction. Reduced mitochondrial function is thought to be central to β-cell dysfunction. Mitochondrial dysfunction and reduced insulin secretion are also observed in β-cells of humans with the most common human genetic disorder, Down syndrome (DS, Trisomy 21). To identify regions of chromosome 21 that may be associated with perturbed glucose homeostasis we profiled the glycaemic status of different DS mouse models. The Ts65Dn and Dp16 DS mouse lines were hyperglycemic, while Tc1 and Ts1Rhr mice were not, providing us with a region of chromosome 21 containing genes that cause hyperglycemia. We then examined whether any of these genes were upregulated in a set of ~5,000 gene expression changes we had identified in a large gene expression analysis of human T2D β-cells. This approach produced a single gene, RCAN1, as a candidate gene linking hyperglycemia and functional changes in T2D β-cells. Further investigations demonstrated that RCAN1 methylation is reduced in human T2D islets at multiple sites, correlating with increased expression. RCAN1 protein expression was also increased in db/db mouse islets and in human and mouse islets exposed to high glucose. Mice overexpressing RCAN1 had reduced in vivo glucose-stimulated insulin secretion and their β-cells displayed mitochondrial dysfunction including hyperpolarised membrane potential, reduced oxidative phosphorylation and low ATP production. This lack of β-cell ATP had functional consequences by negatively affecting both glucose-stimulated membrane depolarisation and ATP-dependent insulin granule exocytosis. Thus, from amongst the myriad of gene expression changes occurring in T2D β-cells where we had little knowledge of which changes cause β-cell dysfunction, we applied a trisomy 21 screening approach which linked RCAN1 to β-cell mitochondrial dysfunction in T2D.

Synaptic Vesicle Recycling Is Unaffected in the Ts65Dn Mouse Model of Down Syndrome

Down syndrome (DS) is the most common genetic cause of intellectual disability, and arises from trisomy of human chromosome 21. Accumulating evidence from studies of both DS patient tissue and mouse models has suggested that synaptic dysfunction is a key factor in the disorder. The presence of several genes within the DS trisomy that are either directly or indirectly linked to synaptic vesicle (SV) endocytosis suggested that presynaptic dysfunction could underlie some of these synaptic defects. Therefore we determined whether SV recycling was altered in neurons from the Ts65Dn mouse, the best characterised model of DS to date. We found that SV exocytosis, the size of the SV recycling pool, clathrin-mediated endocytosis, activity-dependent bulk endocytosis and SV generation from bulk endosomes were all unaffected by the presence of the Ts65Dn trisomy. These results were obtained using battery of complementary assays employing genetically-encoded fluorescent reporters of SV cargo trafficking, and fluorescent and morphological assays of fluid-phase uptake in primary neuronal culture. The absence of presynaptic dysfunction in central nerve terminals of the Ts65Dn mouse suggests that future research should focus on the established alterations in excitatory / inhibitory balance as a potential route for future pharmacotherapy.

Explanation of Metastasis by Homeostatic Inflammation

If inflammation caused by either non-self or self molecules can disseminate throughout the body and inflammatory sites actively allow entry of circulating tumor cells and assist regrowth, then circulating tumor cells metastasize to the sites of inflammation. However, disrupted sites of homeostatic inflammation do not necessarily guarantee metastatic spread and subsequent regrowth.

The calcineurin inhibitor Sarah (Nebula) exacerbates Aβ42 phenotypes in a Drosophila model of Alzheimer's disease

Expression of the Down syndrome critical region 1 (DSCR1) protein, an inhibitor of the Ca²⁺-dependent phosphatase calcineurin, is elevated in the brains of individuals with Down syndrome (DS) or Alzheimer's disease (AD). Although increased levels of DSCR1 were often observed to be deleterious to neuronal health, its beneficial effects against AD neuropathology have also been reported, and the roles of DSCR1 on the pathogenesis of AD remain controversial. Here, we investigated the role of sarah (sra; also known as nebula), a Drosophila DSCR1 ortholog, in amyloid-β42 (Aβ42)-induced neurological phenotypes in Drosophila. We detected sra expression in the mushroom bodies of the fly brain, which are a center for learning and memory in flies. Moreover, similar to humans with AD, Aβ42-expressing flies showed increased Sra levels in the brain, demonstrating that the expression pattern of DSCR1 with regard to AD pathogenesis is conserved in Drosophila. Interestingly, overexpression of sra using the UAS-GAL4 system exacerbated the rough-eye phenotype, decreased survival rates and increased neuronal cell death in Aβ42-expressing flies, without modulating Aβ42 expression. Moreover, neuronal overexpression of sra in combination with Aβ42 dramatically reduced both locomotor activity and the adult lifespan of flies, whereas flies with overexpression of sra alone showed normal climbing ability, albeit with a slightly reduced lifespan. Similarly, treatment with chemical inhibitors of calcineurin, such as FK506 and cyclosporin A, or knockdown of calcineurin expression by RNA interference (RNAi), exacerbated the Aβ42-induced rough-eye phenotype. Furthermore, sra-overexpressing flies displayed significantly decreased mitochondrial DNA and ATP levels, as well as increased susceptibility to oxidative stress compared to that of control flies. Taken together, our results demonstrating that sra overexpression augments Aβ42 cytotoxicity in Drosophila suggest that DSCR1 upregulation or calcineurin downregulation in the brain might exacerbate Aβ42-associated neuropathogenesis in AD or DS.

Drosophila Collection: Chronically increased levels of Sarah (Nebula), a calcineurin inhibitor, cause mitochondria dysfunction and subsequently increased Aβ42-induced cytotoxicity in Drosophila.

RCAN1 overexpression promotes age-dependent mitochondrial dysregulation related to neurodegeneration in Alzheimer's disease

Aging is the largest risk factor for Alzheimer's disease (AD). Patients with Down syndrome (DS) develop symptoms consistent with early-onset AD, suggesting that overexpression of chromosome 21 genes such as Regulator of Calcineurin 1 (RCAN1) plays a role in AD pathogenesis. RCAN1 levels are increased in the brain of DS and AD patients but also in the human brain with normal aging. RCAN1 has been implicated in several neuronal functions, but whether its increased expression is correlative or causal in the aging-related progression of AD remains elusive. We show that brain-specific overexpression of the human RCAN1.1S isoform in mice promotes early age-dependent memory and synaptic plasticity deficits, tau pathology, and dysregulation of dynamin-related protein 1 (DRP1) activity associated with mitochondrial dysfunction and oxidative stress, reproducing key AD features. Based on these findings, we propose that chronic RCAN1 overexpression during aging alters DRP1-mediated mitochondrial fission and thus acts to promote AD-related progressive neurodegeneration.

Influence of Two Various Durations of Resistance Exercise on Oxidative Stress in the Male Rat's Hearts

INTRODUCTION

The previous studies have suggested that alteration in oxidative stress and antioxidant defense depends on various factors, such as mode, intensity, frequency and duration of exercise. In this study, we compared the effects of two various durations of resistance exercise (1 month and 4 month) on oxidative stress and antioxidant status in cardiac tissue.

METHODS

Thirty Wistar male rats divided into 3 groups: control (sedentary), exercise-1 (regular exercise for 1 month) and exercise-2 group (regular exercise for 4 months). After the final to the experiment, the rats were anesthetized, and then blood and heart samples were obtained and used to determine glutathione peroxidase (GPX), superoxide dismutase (SOD), malondialdehyde (MDA) and biochemical estimation.

RESULTS

MDA levels between control and exercise-2 groups showed no significant difference, hence, MDA level in exercise-1 group was higher compared to control group (P < .01). The heart GPX activity increased significantly in exercise-2 group regarding other groups (P < .01). The SOD activities of groups were similar. Creatine kinase (CK) and lactate dehydrogenase (LDH) concentrations increased in the exercise-1 compared to the other groups (P < .01).

CONCLUSION

Our results indicate that in heart, the adaptation and alteration in oxidative stress and cell injury level depend on duration of exercise.

Systematic Tracking of Disrupted Modules Identifies Altered Pathways Associated with Congenital Heart Defects in Down Syndrome

BACKGROUND

This work aimed to identify altered pathways in congenital heart defects (CHD) in Down syndrome (DS) by systematically tracking the dysregulated modules of reweighted protein-protein interaction (PPI) networks.

MATERIAL AND METHODS

We performed systematic identification and comparison of modules across normal and disease conditions by integrating PPI and gene-expression data. Based on Pearson correlation coefficient (PCC), normal and disease PPI networks were inferred and reweighted. Then, modules in the PPI network were explored by clique-merging algorithm; altered modules were identified via maximum weight bipartite matching and ranked in non-increasing order. Finally, pathways enrichment analysis of genes in altered modules was carried out based on Database for Annotation, Visualization, and Integrated Discovery (DAVID) to study the biological pathways in CHD in DS.

RESULTS

Our analyses revealed that 348 altered modules were identified by comparing modules in normal and disease PPI networks. Pathway functional enrichment analysis of disrupted module genes showed that the 4 most significantly altered pathways were: ECM-receptor interaction, purine metabolism, focal adhesion, and dilated cardiomyopathy.

CONCLUSIONS

We successfully identified 4 altered pathways and we predicted that these pathways would be good indicators for CHD in DS.

Effects of Cinnamon extract on biochemical enzymes, TNF-α and NF-κB gene expression levels in liver of broiler chickens inoculated with Escherichia coli

Abstract: Infection with Escherichia coli (E. coli) is a common disease in poultry industry. The use of antibiotics to treat diseases is facing serious criticism and concerns. The medicinal plants may be effective alternatives because of their multiplex activities. The aim of this study was to investigate the effects of cinnamon extract on the levels of liver enzymes, tumor necrosis factor-alpha (TNF-α) and nuclear factor-kappa B (NF-κB) gene expressions in liver of broiler chickens infected with E. coli. Ninety Ross-308 broilers were divided into healthy or E. coli-infected groups, receiving normal or cinnamon extract (in concentrations of 100 or 200mg/kg of food) supplemented diets. E. coli suspension (108cfu) was injected subcutaneously after 12 days cinnamon administration. Seventy-two hours after E. coli injection, the blood samples were taken for biochemical analysis of liver enzymes in serum (spectrophotometrically), and liver tissue samples were obtained for detection of gene expression of inflammatory markers TNF-α and NF-κB, using real-time PCR. Infection with E. coli significantly increased the levels of TNF-α and NF-κB gene expressions as well as some liver enzymes including creatine-kinase (CK), lactate-dehydrogenase (LDH), alanine-transferase (ALT) and aspartate-transferase (AST) as compared with control group (P<0.05). Pre-administration of cinnamon extract in broilers diet (in both concentrations) significantly reduced the tissue levels of TNF-α and NF-κB gene expressions and enzymes CK and ALT in serum of broiler chickens inoculated with E. coli in comparison with E. coli group (P<0.05 and P<0.01). The levels of LDH and AST were significantly decreased only by 200mg/kg cinnamon extract in infected broilers. The level of alkaline-phosphatase (ALP) was not affected in any groups. Pre-administration of cinnamon extract in diets of broiler chickens inoculated with E. coli could significantly reduce the gene expression levels of pro-inflammatory mediators and liver enzymes activities, thereby protecting the liver against this pathologic condition.

Pituitary Adenylate Cyclase-activating Polypeptide (PACAP) Targets Down Syndrome Candidate Region 1 (DSCR1/RCAN1) to control Neuronal Differentiation

Pituitary adenylate cyclase-activating peptide (PACAP) is a neurotrophic peptide involved in a wide range of nervous functions, including development, differentiation, and survival, and various aspects of learning and memory. Here we report that PACAP induces the expression of regulator of calcineurin 1 (RCAN1, also known as DSCR1), which is abnormally expressed in the brains of Down syndrome patients. Increased RCAN1 expression is accompanied by activation of the PKA-cAMP response element-binding protein pathways. EMSA and ChIP analyses demonstrate the presence of a functional cAMP response element in the RCAN1 promoter. Moreover, we show that PACAP-dependent neuronal differentiation is significantly disturbed by improper RCAN1 expression. Our data provide the first evidence of RCAN1, a Down syndrome-related gene, as a novel target for control of the neurotrophic function of PACAP.

Consistent in-frame internal tandem duplications of BCOR characterize clear cell sarcoma of the kidney

Clear cell sarcoma of the kidney (CCSK) is one of the major pediatric renal neoplasms, but its associated genetic abnormalities are largely unknown. We identified internal tandem duplications in the BCOR gene (BCL6 corepressor) affecting the C terminus in 100% (20/20) of CCSK tumors but in none (0/193) of the other pediatric renal tumors. CCSK tumors expressed only an aberrant BCOR allele, indicating a close correlation between BCOR aberration and CCSK tumorigenesis.

Molecular mechanisms linking amyloid β toxicity and Tau hyperphosphorylation in Alzheimer׳s disease

Neurofibrillary tangles (aggregates of cytoskeletal Tau protein) and senile plaques (aggregates mainly formed by amyloid β peptide) are two landmark lesions in Alzheimer׳s disease. Some researchers have proposed tangles, whereas others have proposed plaques, as primary lesions. For a long time, these were thought of as independent mechanisms. However, experimental evidence suggests that both lesions are intimately related. We review here some molecular pathways linking amyloid β and Tau toxicities involving, among others, glycogen synthase kinase 3β, p38, Pin1, cyclin-dependent kinase 5, and regulator of calcineurin 1. Understanding amyloid β and Tau toxicities as part of a common pathophysiological mechanism may help to find molecular targets to prevent or even treat the disease.

Rcan1 deficiency impairs neuronal migration and causes periventricular heterotopia

Periventricular heterotopia (PH) is a cortical malformation characterized by aggregation of neurons lining the lateral ventricles due to abnormal neuronal migration. The molecular mechanism underlying the pathogenesis of PH is unclear. Here we show that Regulators of calcineurin 1 (Rcan1), a Down syndrome-related gene, plays an important role in radial migration of rat cortical neurons. Downregulation of Rcan1 by expressing shRNA impaired neural progenitor proliferation and led to defects in radial migration and PH. Two isoforms of Rcan1 (Rcan1-1 and Rcan1-4) are expressed in the rat brain. Migration defects due to downregulation of Rcan1 could be prevented by shRNA-resistant expression of Rcan1-1 but not Rcan1-4. Furthermore, we found that Rcan1 knockdown significantly decreased the expression level of Flna, an F-actin cross-linking protein essential for cytoskeleton rearrangement and cell migration, mutation of which causes the most common form of bilateral PH in humans. Finally, overexpression of FLNA in Rcan1 knockdown neurons prevented migration abnormalities. Together, these findings demonstrate that Rcan1 acts upstream from Flna in regulating radial migration and suggest that impairment of Rcan1-Flna pathway may underlie PH pathogenesis.

Identification and mutational analyses of phosphorylation sites of the calcineurin-binding protein CbpA and the identification of domains required for calcineurin binding in Aspergillus fumigatus

Calcineurin is a key protein phosphatase required for hyphal growth and virulence in Aspergillus fumigatus, making it an attractive antifungal target. However, currently available calcineurin inhibitors, FK506 and cyclosporine A, are immunosuppressive, limiting usage in the treatment of patients with invasive aspergillosis. Therefore, the identification of endogenous inhibitors of calcineurin belonging to the calcipressin family is an important parallel strategy. We previously identified the gene cbpA as the A. fumigatus calcipressin member and showed its involvement in hyphal growth and calcium homeostasis. However, the mechanism of its activation/inhibition through phosphorylation and its interaction with calcineurin remains unknown. Here we show that A. fumigatus CbpA is phosphorylated at three distinct domains, including the conserved SP repeat motif (phosphorylated domain-I; PD-I), a filamentous fungal-specific domain (PD-II), and the C-terminal CIC motif (Calcipressin Inhibitor of Calcineurin; PD-III). While mutation of three phosphorylated residues (Ser208, Ser217, Ser223) in the PD-II did not affect CbpA function in vivo, mutation of the two phosphorylated serines (Ser156, Ser160) in the SP repeat motif caused reduced hyphal growth and sensitivity to oxidative stress. Mutational analysis in the key domains in calcineurin A (CnaA) and proteomic interaction studies confirmed the requirement of PxIxIT motif-binding residues (352-NIR-354) and the calcineurin B (CnaB)-binding helix residue (V371) for the binding of CbpA to CnaA. Additionally, while the calmodulin-binding residues (442-RVF-444) did not affect CbpA binding to CnaA, three mutations (T359P, H361L, and L365S) clustered between the CnaA catalytic and the CnaB-binding helix were also required for CbpA binding. This is the first study to analyze the phosphorylation status of calcipressin in filamentous fungi and identify the domains required for binding to calcineurin.

Anabolic steroids activate calcineurin-NFAT signaling and thereby increase myotube size and reduce denervation atrophy

Anabolic androgens have been shown to reduce muscle loss due to immobilization, paralysis and many other medical conditions, but the molecular basis for these actions is poorly understood. We have recently demonstrated that nandrolone, a synthetic androgen, slows muscle atrophy after nerve transection associated with down-regulation of regulator of calcineurin 2 (RCAN2), a calcineurin inhibitor, suggesting a possible role of calcineurin-NFAT signaling. To test this possibility, rat gastrocnemius muscle was analyzed at 56 days after denervation. In denervated muscle, calcineurin activity declined and NFATc4 was excluded from the nucleus and these effects were reversed by nandrolone. Similarly, nandrolone increased calcineurin activity and nuclear NFATc4 levels in cultured L6 myotubes. Nandrolone also induced cell hypertrophy that was blocked by cyclosporin A or overexpression of RCAN2. Finally protection against denervation atrophy by nandrolone in rats was blocked by cyclosporin A. These results demonstrate for the first time that nandrolone activates calcineurin-NFAT signaling, and that such signaling is important in nandrolone-induced cell hypertrophy and protection against paralysis-induced muscle atrophy.

Histone deacetylase 3 promotes RCAN1 stability and nuclear translocation

Regulator of calcineurin 1 (RCAN1; also referred as DSCR1 or MCIP1) is located in close proximity to a Down syndrome critical region of human chromosome 21. Although RCAN1 is an endogenous inhibitor of calcineurin signaling that controls lymphocyte activation, apoptosis, heart development, skeletal muscle differentiation, and cardiac function, it is not yet clear whether RCAN1 might be involved in other cellular activities. In this study, we explored the extra-functional roles of RCAN1 by searching for novel RCAN1-binding partners. Using a yeast two-hybrid assay, we found that RCAN1 (RCAN1-1S) interacts with histone deacetylase 3 (HDAC3) in mammalian cells. We also demonstrate that HDAC3 deacetylates RCAN1. In addition, HDAC3 increases RCAN1 protein stability by inhibiting its poly-ubiquitination. Furthermore, HDAC3 promotes RCAN1 nuclear translocation. These data suggest that HDAC3, a new binding regulator of RCAN1, affects the protein stability and intracellular localization of RCAN1.

Murine Creld1 controls cardiac development through activation of calcineurin/NFATc1 signaling

Calcineurin is a heteromeric Ca(2+)-dependent serine/threonine phosphatase. It dephosphorylates the transcription factor nuclear factor of activated T cells (NFAT) in the cytoplasm, which subsequently undergoes nuclear translocation. NFAT regulates numerous biological processes, including inflammatory T cell responses and cardiac development. Our study identifies the Cysteine-Rich with EGF-Like Domains 1 (Creld1) gene as a regulator of calcineurin/NFATc1 signaling. We show that Creld1 is sufficient to promote NFATc1 dephosphorylation and translocation to the nucleus. Creld1 is contained in a joint protein complex with the regulatory subunit of calcineurin, CnB, thereby controlling calcineurin function. Localization of Creld1 at the endoplasmic reticulum (ER) is important to exert its action on calcineurin. By using Creld1KO mice, we demonstrate that Creld1 is essential for heart development. Creld1 function is required for the VEGF-dependent proliferation of endocardial cells by promoting the expression of NFATc1 target-genes. Collectively, our study identifies Creld1 as an important regulator of calcineurin/NFATc1 signaling.

Aberrant expression of RCAN1 in Alzheimer's pathogenesis: a new molecular mechanism and a novel drug target

AD, a devastating neurodegenerative disorder, is the most common cause of dementia in the elderly. Patients with AD are characterized by three hallmarks of neuropathology including neuritic plaque deposition, neurofibrillary tangle formation, and neuronal loss. Growing evidences indicate that dysregulation of regulator of calcineurin 1 (RCAN1) plays an important role in the pathogenesis of AD. Aberrant RCAN1 expression facilitates neuronal apoptosis and Tau hyperphosphorylation, leading to neuronal loss and neurofibrillary tangle formation. This review aims to describe the recent advances of the regulation of RCAN1 expression and its physiological functions. Moreover, the AD risk factors-induced RCAN1 dysregulation and its role in promoting neuronal loss, synaptic impairments and neurofibrillary tangle formation are summarized. Furthermore, we provide an outlook into the effects of RCAN1 dysregulation on APP processing, Aβ generation and neuritic plaque formation, and the possible underlying mechanisms, as well as the potential of targeting RCAN1 as a new therapeutic approach.

Regulator of calcineurin 1 modulates expression of innate anxiety and anxiogenic responses to selective serotonin reuptake inhibitor treatment

Regulator of calcineurin 1 (RCAN1) controls the activity of calcium/calmodulin-dependent phosphatase calcineurin (CaN), which has been implicated in human anxiety disorders. Previously, we reported that RCAN1 functioned as an inhibitor of CaN activity in the brain. However, we now find enhanced phosphorylation of a CaN substrate, cAMP response element-binding protein (CREB), in the brains of Rcan1 knock-out (KO) mice. Consistent with enhanced CREB activation, we also observe enhanced expression of a CREB transcriptional target, brain-derived neurotrophic factor (BDNF) in Rcan1 KO mice. We also discovered that RCAN1 deletion or blockade of RCAN1-CaN interaction reduced CaN and protein phosphatase-1 localization to nuclear-enriched protein fractions and promoted CREB activation. Because of the potential links between CREB, BDNF, and anxiety, we examined the role of RCAN1 in the expression of innate anxiety. Rcan1 KO mice displayed reduced anxiety in several tests of unconditioned anxiety. Acute pharmacological inhibition of CaN rescued these deficits while transgenic overexpression of human RCAN1 increased anxiety. Finally, we found that Rcan1 KO mice lacked the early anxiogenic response to the selective serotonin reuptake inhibitor (SSRI) fluoxetine and had improved latency for its therapeutic anxiolytic effects. Together, our study suggests that RCAN1 plays an important role in the expression of anxiety-related and SSRI-related behaviors through CaN-dependent signaling pathways. These results identify RCAN1 as a mediator of innate emotional states and possible therapeutic target for anxiety.

Increased dosage of DYRK1A and DSCR1 delays neuronal differentiation in neocortical progenitor cells

Down's syndrome (DS), a major genetic cause of mental retardation, arises from triplication of genes on human chromosome 21. Here we show that DYRK1A (dual-specificity tyrosine-phosphorylated and -regulated kinase 1A) and DSCR1 (DS critical region 1), two genes lying within human chromosome 21 and encoding for a serine/threonine kinase and calcineurin regulator, respectively, are expressed in neural progenitors in the mouse developing neocortex. Increasing the dosage of both proteins in neural progenitors leads to a delay in neuronal differentiation, resulting ultimately in alteration of their laminar fate. This defect is mediated by the cooperative actions of DYRK1A and DSCR1 in suppressing the activity of the transcription factor NFATc. In Ts1Cje mice, a DS mouse model, dysregulation of NFATc in conjunction with increased levels of DYRK1A and DSCR1 was observed. Furthermore, counteracting the dysregulated pathway ameliorates the delayed neuronal differentiation observed in Ts1Cje mice. In sum, our findings suggest that dosage of DYRK1A and DSCR1 is critical for proper neurogenesis through NFATc and provide a potential mechanism to explain the neurodevelopmental defects in DS.

A major role for RCAN1 in atherosclerosis progression

Atherosclerosis is a complex inflammatory disease involving extensive vascular vessel remodelling and migration of vascular cells. As RCAN1 is implicated in cell migration, we investigated its contribution to atherosclerosis. We show RCAN1 induction in atherosclerotic human and mouse tissues. Rcan1 was expressed in lesional macrophages, endothelial cells and vascular smooth muscle cells and was induced by treatment of these cells with oxidized LDLs (oxLDLs). Rcan1 regulates CD36 expression and its genetic inactivation reduced atherosclerosis extension and severity in Apoe^−/− mice. This effect was mechanistically linked to diminished oxLDL uptake, resistance to oxLDL-mediated inhibition of macrophage migration and increased lesional IL-10 and mannose receptor expression. Moreover, Apoe^−/−Rcan1^−/− macrophages expressed higher-than-Apoe^−/− levels of anti-inflammatory markers. We previously showed that Rcan1 mediates aneurysm development and that its expression is not required in haematopoietic cells for this process. However, transplantation of Apoe^−/−Rcan1^−/− bone-marrow (BM) cells into Apoe^−/− recipients confers atherosclerosis resistance. Our data define a major role for haematopoietic Rcan1 in atherosclerosis and suggest that therapies aimed at inhibiting RCAN1 expression or function might significantly reduce atherosclerosis burden.

Nebula/DSCR1 upregulation delays neurodegeneration and protects against APP-induced axonal transport defects by restoring calcineurin and GSK-3β signaling

Post-mortem brains from Down syndrome (DS) and Alzheimer's disease (AD) patients show an upregulation of the Down syndrome critical region 1 protein (DSCR1), but its contribution to AD is not known. To gain insights into the role of DSCR1 in AD, we explored the functional interaction between DSCR1 and the amyloid precursor protein (APP), which is known to cause AD when duplicated or upregulated in DS. We find that the Drosophila homolog of DSCR1, Nebula, delays neurodegeneration and ameliorates axonal transport defects caused by APP overexpression. Live-imaging reveals that Nebula facilitates the transport of synaptic proteins and mitochondria affected by APP upregulation. Furthermore, we show that Nebula upregulation protects against axonal transport defects by restoring calcineurin and GSK-3β signaling altered by APP overexpression, thereby preserving cargo-motor interactions. As impaired transport of essential organelles caused by APP perturbation is thought to be an underlying cause of synaptic failure and neurodegeneration in AD, our findings imply that correcting calcineurin and GSK-3β signaling can prevent APP-induced pathologies. Our data further suggest that upregulation of Nebula/DSCR1 is neuroprotective in the presence of APP upregulation and provides evidence for calcineurin inhibition as a novel target for therapeutic intervention in preventing axonal transport impairments associated with AD.

Alzheimer's disease (AD) is a debilitating neurodegenerative disease characterized by gradual neuronal cell loss and memory decline. Importantly, Down syndrome (DS) individuals over 40 years of age almost always develop neuropathological features of AD, although most do not develop dementia until at least two decades later. These findings suggest that DS and AD may share common genetic causes and that a neuroprotective mechanism may delay neurodegeneration and cognitive decline. It has been shown that the amyloid precursor protein (APP), which is associated with AD when duplicated and upregulated in DS, is a key gene contributing to AD pathologies and axonal transport abnormalities. Here, using fruit fly as a simple model organism, we examined the role of Down syndrome critical region 1 (DSCR1), another gene located on chromosome 21 and upregulated in both DS and AD, in modulating APP phenotypes. We find that upregulation of DSCR1 (Nebula in flies) is neuroprotective in the presence of APP upregulation. We report that nebula overexpression delays the onset of neurodegeneration and transport blockage in neuronal cells. Our results further suggest that signaling pathways downstream of DSCR1 may be potential therapeutic targets for AD.

Chronic high levels of the RCAN1-1 protein may promote neurodegeneration and Alzheimer disease

The RCAN1 gene encodes three different protein isoforms: RCAN1-4, RCAN1-1L, and RCAN1-1S. RCAN1-1L is the RCAN1 isoform predominantly expressed in human brains. RCAN1 proteins have been shown to regulate various other proteins and cellular functions, including calcineurin, glycogen synthase kinase-3β (GSK-3β), the mitochondrial adenine nucleotide transporter (ANT), stress adaptation, ADP/ATP exchange in mitochondria, and the mitochondrial permeability transition pore (mtPTP). The effects of increased RCAN1 gene expression seem to depend both on the specific RCAN1 protein isoform(s) synthesized and on the length of time the level of each isoform is elevated. Transiently elevated RCAN1-4 and RCAN1-1L protein levels, lasting just a few hours, can be neuroprotective under acute stress conditions, including acute oxidative stress. We propose that, by transiently inhibiting the phosphatase calcineurin, RCAN1-4 and RCAN1-1L may reinforce and extend protective stress-adaptive cell responses. In contrast, prolonged elevation of RCAN1-1L levels is associated with the types of neurodegeneration observed in several diseases, including Alzheimer disease and Down syndrome. RCAN1-1L levels can also be increased by multiple chronic stresses and by glucocorticoids, both of which can cause neurodegeneration. Although increasing levels of RCAN1-1L for just a few months has no overtly obvious neurodegenerative effect, it does suppress neurogenesis. Longer term elevation of RCAN1-1L levels (for at least 16 months), however, can lead to the first signs of neurodegeneration. Such neurodegeneration may be precipitated by (RCAN1-1L-mediated) prolonged calcineurin inhibition and GSK-3β induction/activation, both of which promote tau hyperphosphorylation, and/or by (RCAN1-1L-mediated) effects on the mitochondrial ANT, diminished ATP/ADP ratio, opening of the mtPTP, and mitochondrial autophagy. We propose that RCAN1-1L operates through various molecular mechanisms, primarily dependent upon the length of time protein levels are elevated. We also suggest that models analyzing long-term RCAN1 gene overexpression may help us to understand the molecular mechanisms of neurodegeneration in diseases such as Alzheimer disease, Down syndrome, and possibly others.

CREB-mediated Bcl-2 expression contributes to RCAN1 protection from hydrogen peroxide-induced neuronal death

Regulator of calcineurin 1 (RCAN1) is located on the Down syndrome critical region (DSCR) locus in human chromosome 21. In this study, we investigated the functional role of RCAN1 in the reactive oxygen species (ROS)-mediated neuronal death signaling. We found that RCAN1 was able to protect the cells from H(2)O(2) -induced cytotoxicity. The expression of RCAN1 caused an inhibition of the H(2)O(2) -induced activation of mitogen-activated protein kinases (MAPKs) and AP-1. In contrast, RCAN1 significantly enhanced the activity of cAMP response element-binding protein (CREB). Furthermore, RCAN1 induced the expression of the CREB target gene, Bcl-2. Consistently, knockdown of endogenous RCAN1 using shRNA down regulated the phosphorylation of CREB and the expression of Bcl-2, which protects the cells from H(2)O(2) -induced cytotoxicity. Our data provide a new mechanism for the cytoprotective function of RCAN1 in response to oxidant-induced apoptosis.

The role of taurine on skeletal muscle cell differentiation

Taurine abundantly contained in the skeletal muscle has been considered as one of essential factors for the differentiation and growth of skeletal muscles. The previous studies in the taurine transporter knockout mice showed that deficiency of taurine content in the skeletal muscle caused incomplete muscular developments, morphological abnormalities, and exercise abilities. In fetal and neonatal periods, taurine must be an essential amino acid due to no biosynthesis capacity, and therefore, taurine should be endogenously supplied through placenta and maternal milk. In general cell culture condition, taurine contained in the culture medium is absent or few, and therefore, most of cultured cells are in taurine-deficient condition. In the present study, we confirmed, in cultured mouse differentiable myoblast, taurine treatment significantly enhanced the differentiation to myotube in a dose-dependent manner, while these effects were abrogated by inhibitions of taurine transport and Ca(2+) signaling pathway.The present study suggested that exogenous taurine might play a key role on the mature differentiation/growth of the skeletal muscle during development period through Ca(2+) signaling pathway, and therefore, taurine would contribute the muscle recovery after damages.

Upregulation of RCAN1 causes Down syndrome-like immune dysfunction

BACKGROUND

People with Down syndrome (DS) are more susceptible to infections and autoimmune disease, but the molecular genetic basis for these immune defects remains undetermined. In this study, we tested whether increased expression of the chromosome 21 gene RCAN1 contributes to immune dysregulation.

METHODS

We investigated the immune phenotype of a mouse model that overexpresses RCAN1. RCAN1 transgenic (TG) mice exhibit T cell abnormalities that bear a striking similarity to the abnormalities described in individuals with DS.

RESULTS

RCAN1-TG mice display T cell developmental defects in the thymus and peripheral immune tissues. Thymic cellularity is reduced by substantial losses of mature CD4 and CD8 thymocytes and medullary epithelium. In peripheral immune organs T lymphocytes are reduced in number and exhibit reduced proliferative capacity and aberrant cytokine production. These T cell defects are stem cell intrinsic in that transfer of wild type bone marrow into RCAN1-TG recipients restored medullary thymic epithelium and T cell numbers in the thymus, spleen and lymph nodes. However, bone marrow transplantation failed to improve T cell function, suggesting an additional role for RCAN1 in the non-haemopoietic compartment.

CONCLUSIONS

RCAN1 therefore facilitates T cell development and function, and when overexpressed, may contribute to immune dysfunction in DS.

Evaluation of cardiac functions with Doppler echocardiography in children with Down syndrome and anatomically normal heart

OBJECTIVE

To study the cardiac functions in Down syndrome children who did not have structural cardiac lesion by conventional and tissue Doppler echocardiography.

MATERIALS AND METHODS

A total of 85 children with Down syndrome without anatomic heart disease and 50 normal control children were subjected to the assessment of right and left ventricular functions by both two-dimensional and tissue Doppler echocardiography.

RESULTS

Children with Down syndrome had significantly higher left ventricular ejection fraction detected by two-dimensional echocardiography and left ventricular diastolic dysfunction detected by tissue Doppler than observed in the controls. In addition, children with Down syndrome also had right ventricular systolic and diastolic dysfunctions. Children with Down syndrome had significantly higher pulmonary artery systolic pressure than the control children. There was no significant difference in the cardiac functions between children with non-disjunction Down syndrome and those with the translocation type.

CONCLUSION

Despite an apparently normal heart, children with Down syndrome may have silent disturbed cardiac functions, which may be detected by two-dimensional or tissue Doppler echocardiography. This may have an important clinical implication, especially before involving Down syndrome children in surgery or strenuous exercise.

RCAN1 regulates vesicle recycling and quantal release kinetics via effects on calcineurin activity

We have previously shown that Regulator of Calcineurin 1 (RCAN1) regulates multiple stages of vesicle exocytosis. However, the mechanisms by which RCAN1 affects secretory vesicle exocytosis and quantal release kinetics remain unknown. Here, we use carbon fibre amperometry to detect exocytosis from chromaffin cells and identify these underlying mechanisms. We observe reduced exocytosis with repeated stimulations in chromaffin cells over-expressing RCAN1 (RCAN1(ox)), but not in wild-type (WT) cells, indicating a negative effect of RCAN1 on vesicle recycling and endocytosis. Acute exposure to calcineurin inhibitors, cyclosporine A and FK-506, replicates this effect in WT cells but has no additional effect in RCAN1(ox) cells. When we chronically expose WT cells to cyclosporine A and FK-506 we find that catecholamine release per vesicle and pre-spike foot (PSF) signal parameters are decreased, similar to that in RCAN1(ox) cells. Inhibiting calcineurin activity in RCAN1(ox) cells has no additional effect on the amount of catecholamine release per vesicle but further reduces PSF signal parameters. Although electron microscopy studies indicate these changes are not because of altered vesicle number or distribution in RCAN1(ox) cells, the smaller vesicle and dense core size we observe in RCAN1(ox) cells may underlie the reduced quantal release in these cells. Thus, our results indicate that RCAN1 most likely affects vesicle recycling and quantal release kinetics via the inhibition of calcineurin activity.

Increased expression of the glucose-responsive gene, RCAN1, causes hypoinsulinemia, β-cell dysfunction, and diabetes

RCAN1 is a chromosome 21 gene that controls secretion in endocrine cells, regulates mitochondrial function, and is sensitive to oxidative stress. Regulator of calcineurin 1 (RCAN1) is also an endogenous inhibitor of the protein phosphatase calcineurin, the inhibition of which leads to hypoinsulinemia and diabetes in humans and mice. However, the presence or the role of RCAN1 in insulin-secreting β-cells and its potential role in the pathogenesis of diabetes is unknown. Hence, the aim of this study is to investigate the presence of RCAN1 in β-cells and identify its role in β-cell function. RCAN1 is expressed in mouse islets and in the cytosol of pancreatic β-cells. We find RCAN1 is a glucose-responsive gene with a 1.5-fold increase in expression observed in pancreatic islets in response to chronic hyperglycemia. The overexpression of the human RCAN1.1 isoform in mice under the regulation of its endogenous promoter causes diabetes, age-associated hyperglycemia, reduced glucose tolerance, hypoinsulinemia, loss of β-cells, reduced β-cell insulin secretion, aberrant mitochondrial reactive oxygen species production, and the down-regulation of key β-cell genes. Our data therefore identifies a novel molecular link between the overexpression of RCAN1 and β-cell dysfunction. The glucose-responsive nature of RCAN1 provides a potential mechanism of action associated with the β-cell dysfunction observed in diabetes.

Covalent NEDD8 conjugation increases RCAN1 protein stability and potentiates its inhibitory action on calcineurin

Similar to ubiquitin, regulatory roles for NEDD8 (neural precursor cell-expressed developmentally down-regulated 8) are being clarified during cell growth, signal transduction, immune response, and development. However, NEDD8 targets and their functional alterations are not well known. Regulator of calcineurin 1 (RCAN1/DSCR1P1) is located near the Down syndrome critical region on the distal part of chromosome 21, and its gene product is an endogenous inhibitor of calcineurin signaling. RCAN1 is modified by ubiquitin and consequently undergoes proteasomal degradation. Here we report that NEDD8 is conjugated to RCAN1 (RCAN1-1S) via three lysine residues, K96, K104, and K107. Neddylation enhances RCAN1 protein stability without affecting its cellular location. In addition, we found that neddylation significantly inhibits proteasomal degradation of RCAN1, which may underlie the ability of NEDD8 to enhance RCAN1 stability. Furthermore, neddylation increases RCAN1 binding to calcineurin, which potentiates its inhibitory activity toward downstream NFAT signaling. The present study provides a new regulatory mechanism of RCAN1 function and highlights an important role for diverse RCAN1-involved cellular physiology.