DSCR1 gene expression is dependent on NFATc1 during cardiac valve formation and colocalizes with anomalous organ development in trisomy 16 mice

The Down syndrome critical region 1 (DSCR1) gene is present in the region of human chromosome 21 and the syntenic region of mouse chromosome 16, trisomy of which is associated with congenital heart defects observed in Down syndrome. DSCR1 encodes a regulatory protein in the calcineurin/NFAT signal transduction pathway. During valvuloseptal development in the heart, DSCR1 is expressed in the endocardium of the developing atrioventricular and semilunar valves, the muscular interventricular septum, and the ventricular myocardium. Human DSCR1 contains an NFAT-rich calcineurin-responsive element adjacent to exon 4. Transgenic mice generated with a homologous regulatory region of the mouse DSCR1 gene linked to lacZ (DSCR1(e4)/lacZ) show gene activation in the endocardium of the developing valves and aorticopulmonary septum of the heart, recapitulating a specific subdomain of endogenous DSCR1 cardiac expression. DSCR1(e4)/lacZ expression in the developing valve endocardium colocalizes with NFATc1 and, endocardial DSCR1(e4)/lacZ, is notably reduced or absent in NFATc1(-/-) embryos. Furthermore, expression of the endogenous DSCR1(e4) isoform is decreased in the outflow tract of NFATc1(-/-) hearts, and the DSCR1(e4) intragenic element is trans-activated by NFATc1 in cell culture. In trisomy 16 (Ts16) mice, expression of endogenous DSCR1 and DSCR1(e4)/lacZ colocalizes with anomalous valvuloseptal development, and transgenic Ts16 hearts have increased beta-galactosidase activity. DSCR1 and DSCR1(e4)/lacZ also are expressed in other organ systems affected by trisomy 16 in mice or trisomy 21 in humans including the brain, eye, ear, face, and limbs. Together, these results show that DSCR1(e4) expression in the developing valve endocardium is dependent on NFATc1 and support a role for DSCR1 in normal cardiac valvuloseptal formation as well as the abnormal development of several organ systems affected in individuals with Down syndrome.     

NF-kappaB-inducing kinase phosphorylates and blocks the degradation of Down syndrome candidate region 1

Down syndrome, the most frequent genetic disorder, is characterized by an extra copy of all or part of chromosome 21. Down syndrome candidate region 1 (DSCR1) gene, which is located on chromosome 21, is highly expressed in the brain of Down syndrome patients. Although its cellular function remains unknown, DSCR1 expression is linked to inflammation, angiogenesis, and cardiac development. To explore the functional role of DSCR1 and the regulation of its expression, we searched for novel DSCR1-interacting proteins using a yeast two-hybrid assay. Using a human fetal brain library, we found that DSCR1 interacts with NF-kappaB-inducing kinase (NIK). Furthermore, we demonstrate that NIK specifically interacts with and phosphorylates the C-terminal region of DSCR1 in immortalized hippocampal cells as well as in primary cortical neurons. This NIK-mediated phosphorylation of DSCR1 increases its protein stability and blocks its proteasomal degradation, the effects of which lead to an increase in soluble and insoluble DSCR1 levels. We show that an increase in insoluble DSCR1 levels results in the formation of cytosolic aggregates. Interestingly, we found that whereas the formation of these inclusions does not significantly alter the viability of neuronal cells, the overexpression of DSCR1 without the formation of aggregates is cytotoxic.     

Protein levels of genes encoded on chromosome 21 in fetal Down Syndrome brain (Part V): Overexpression of phosphatidyl-inositol-glycan class P protein (DSCR5)

Summary. Down Syndrome (DS, trisomy 21) is the most common genetic cause of mental retardation. The completed sequencing of genes encoded on chromosome 21 provides excellent basic information, however the molecular mechanisms leading to the phenotype of DS remain to be elucidated. Although overexpression of chromosome 21 encoded genes has been documented information at the protein expression level is mandatory as it is the proteins that carry out function. We therefore decided to evaluated expression level of seven proteins whose genes are encoded on chromosome 21: DSCR4, DSCR5, DSCR6; KIR4.2, GIRK2, KCNE1 and KCNE2 in fetal cortex brain of DS and controls at the early second trimester of pregnancy by Western blotting. -actin and neuron specific enolase (NSE) were used to normalise cell loss and neuronal loss. DSCR5 (PIG-P), a component of glycosylphosphatidylinositol-N-acetylglucosaminyltransferase (GPI-GnT), was overexpressed about twofold, even when levels were normalised with NSE. DSCR6 was overexpressed in addition but when normalised versus NSE, levels were comparable to controls. DSCR4 was not detectable in fetal brain. Potassium channels KIR4.2 and GIRK2 were comparable between DS and controls, whereas KCNE1 and KCNE2 were not detectable. Quantification of these proteins encoded on chromosome 21 revealed that not all gene products of the DS critical region are overexpressed in DS brain early in life, indicating that the DS phenotype cannot be simply explained by the gene dosage effect hypothesis. Overexpression of PIG-P (DSCR5) may lead to or represent impaired glycosylphosphatidylinositol-N-acetylglucosaminyltransferase mediated posttranslational modifications and subsequent anchoring of proteins to the plasma membrane.     

Aggregate formation and synaptic abnormality induced by DSCR1

Aggregation of conformation-abnormal peptides probably plays a key role in the pathogenesis of many neurodegenerative diseases. DSCR1 Down syndrome (DS) critical region 1, was identified from a chromosomal region (21q22.1-q22.2) for the clinical manifestations of DS when an extra-copy is present. We report that expression of DSCR1 in several cell types, including primary neurons, causes microtubule-dependent aggresome-like inclusion body formation. Disease-associated huntingtin (Q148) and ataxin-3 (Q84) co-localize with DSCR1 aggregates. Neurons bearing DSCR1 aggregates show reduced synaptophysin staining in processes. DSCR1 residues 31-90 constitute an aggregation-prone domain that is predicted to form a hydrophobic patch on the protein surface when residues 1-30 are removed. This study identifies a novel function of DSCR1 that may underlie DS neuropathology.     

Nedd4-2 ubiquitin ligase interacts with RCAN1 (DSCR1) for the proteasomal degradation

Regulator of Calcineurin 1 (RCAN1/DSCR1/Adapt78) gene is located in the Down syndrome (DS) region of chromosome 21, and critical for the phenotype of DS and Alzheimer disease (AD). In this report, we found that expression of Nedd4-2 E3 ubiquitin ligase decreased the protein level of RCAN1. Decrease of RCAN1 protein expression by Nedd4-2 was blocked by proteasome inhibitor MG132, indicating that this decrease was mediated by the ubiquitin-proteasome pathway. Furthermore, we found that the ability of Nedd4-2 to degrade RCAN1 depended on the direct binding with RCAN1. Consistently, Nedd4-2 enhanced the ubiquitination of RCAN1 protein. Our data provide the first evidence that Nedd4-2 acts as an important regulatory component in the control of RCAN1 protein stability.     

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.     

Protein dysregulation in mouse hippocampus polytransgenic for chromosome 21 structures in the Down Syndrome Critical Region

Mice polytransgenic for chromosome 21 genes DSCR3, 5, 6, 9, and TTC3 within the Down Syndrome Critical Region-1 represent an animal model for Down Syndrome (DS). In a proteomic approach, we show a series of altered hippocampal protein levels that may be caused by overexpression of at least one of the five chromosome 21 genes and that fit fear-conditioned memory defects and were observed to be dysregulated in human fetal DS.     

唐氏综合症决定域蛋白1泛素化分析

利用Fm oc固相多肽合成的方法合成DSCR1羧基端一个多肽片段(55-70AA),经HPLC纯化后偶联到匙孔槭血蓝蛋白,免疫新西兰雄兔后采血检测、纯化、经W estern b lotting、免疫沉淀证实得到的抗体为抗DSCR1的特异抗体。该抗体即能检测人源DSCR1蛋白,又能检测小鼠的DSCR1蛋白。运用获得的DSCR1多克隆抗体进行功能研究,发现DSCR1广泛存在泛素化,参与泛素化-蛋白酶体途径。     

DSCR1 interacts with FMRP and is required for spine morphogenesis and local protein synthesis

Most common genetic factors known to cause intellectual disability are Down syndrome and Fragile X syndrome. However, the underlying cellular and molecular mechanisms of intellectual disability remain unclear. Recently, dendritic spine dysmorphogenesis and impaired local protein synthesis are posited to contribute to the cellular mechanisms of intellectual disability. Here, we show that Down syndrome critical region1 (DSCR1) interacts with Fragile X mental retardation protein (FMRP) and regulates both dendritic spine morphogenesis and local protein synthesis. Interestingly, decreasing the level of FMRP restores the DSCR1-induced changes in dendritic spine morphology. Our results imply that DSCR1 is a novel regulator of FMRP and that Fragile X syndrome and Down syndrome may share disturbances in common pathways that regulate dendritic spine morphology and local protein synthesis.     

Mutational analyses of the signals involved in the subcellular location of DSCR1

Background  

Down syndrome is the most frequent genetic disorder in humans. Rare cases involving partial trisomy of chromosome 21 allowed a small chromosomal region common to all carriers, called Down Syndrome Critical Region (DSCR), to be determined. The DSCR1 gene was identified in this region and is expressed preferentially in the brain, heart and skeletal muscle. Recent studies have shown that DSCR1 belongs to a family of proteins that binds and inhibits calcineurin, a serine-threonine phosphatase. The work reported on herein consisted of a study of the subcellular location of DSCR1 and DSCR1-mutated forms by fusion with a green fluorescent protein, using various cell lines, including human.     

A patient with Down syndrome with a de novo derivative chromosome 21

Pure partial trisomy of chromosome 21 is a rare event. The patients with this aberration are very important for setting up precise karyotype-phenotype correlations particularly in Down syndrome phenotype. We present here a patient with Down syndrome with a de novo derivative chromosome 21. Karyotype of the patient was designated as 46,XY,der(21)(p13)dup(21)(q11.2q21.3)dup(21)(q22.2q22.3) with regard to cytogenetic, FISH and array-CGH analyses. Non-continuous monosomic, disomic and trisomic chromosomal segments through the derivative chromosome 21 were detected by array-CGH analysis. STR analyses revealed maternal origin of the de novo derivative chromosome 21. The dual-specificity tyrosine (Y)-phosphorylation regulated kinase 1A (DYRK1A) and Down Syndrome Critical Region 1 (DSCR1) genes that are located in Down syndrome critical region, are supposed to be responsible for most of the clinical findings of Down syndrome. However, our patient is the first patient with Down syndrome whose clinical findings were provided in detail, with a de novo derivative chromosome 21 resulting from multiple chromosome breaks excluding DYRK1A and DSCR1 gene regions.     

Identification of a novel putative mitogen-activated kinase cascade on human chromosome 21 by computational approaches

Down syndrome (DS) is the most frequent form of mental retardation and is caused by chromosome 21 (HSA21) trisomy. Despite the number of known genes involved in DS and its high therapeutic interest, biological mechanisms leading to the DS phenotype are not fully clear. We present a functional hypothesis based on fold recognition and hidden Markov model techniques for four HSA21 genes located in the DS Candidate Region (DSCR). More specifically, we propose that they are members of a novel mitogen-activated protein kinase pathway with DYRK1A, SNF1LK and RIPK4 gene products being elements of the kinase cascade and the DSCR3 acting as structural scaffold for their interaction. This hypothesis finds support in various biochemical studies concerning the biological behavior and features of the involved HSA21 proteins. Our analysis calls for specifically designed experiments to validate our prediction and establish its relevance in terms of therapeutic approaches to the disease. CONTACT: anna.tramontano@uniroma1.it SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.     

VEGF selectively induces Down syndrome critical region 1 gene expression in endothelial cells: a mechanism for feedback regulation of angiogenesis?

The Down syndrome critical region 1 (DSCR1) gene (also known as MCIP1, Adapt78) encodes a regulatory protein that binds to calcineurin catalytic A subunit and acts as a regulator of the calcineurin-mediated signaling pathway. We show in this study that DSCR1 is greatly induced in endothelial cells in response to VEGF, TNF-alpha, and A23187 treatment, and that this up-regulation is inhibited by inhibitors of the calcineurin-NFAT (nuclear factor of activated T cells) signaling pathway as well as by PKC inhibition and a Ca(2+) chelator. We hypothesized that the up-regulation of DSCR1 gene expression in endothelial cells could act as an endogenous feedback inhibitor for angiogenesis by regulating the calcineurin-NFAT signaling pathway. Our transient transfection analyses confirm that the overexpression of DSCR1 abrogates the up-regulation of reporter gene expression driven by both the cyclooxygenase 2 and DSCR1 promoters in response to stimulators. Our results indicate that DSCR1 up-regulation may represent a potential molecular mechanism underlying the regulation of angiogenic genes activated by the calcineurin-NFAT signaling pathway in endothelial cells.     

DSCR1 is required for both axonal growth cone extension and steering

Local information processing in the growth cone is essential for correct wiring of the nervous system. As an axon navigates through the developing nervous system, the growth cone responds to extrinsic guidance cues by coordinating axon outgrowth with growth cone steering. It has become increasingly clear that axon extension requires proper actin polymerization dynamics, whereas growth cone steering involves local protein synthesis. However, molecular components integrating these two processes have not been identified. Here, we show that Down syndrome critical region 1 protein (DSCR1) controls axon outgrowth by modulating growth cone actin dynamics through regulation of cofilin activity (phospho/dephospho-cofilin). Additionally, DSCR1 mediates brain-derived neurotrophic factor–induced local protein synthesis and growth cone turning. Our study identifies DSCR1 as a key protein that couples axon growth and pathfinding by dually regulating actin dynamics and local protein synthesis.