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      Phosphatidylserine Increases IKBKAP Levels in Familial Dysautonomia Cells

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          Abstract

          Familial Dysautonomia (FD) is an autosomal recessive congenital neuropathy that results from abnormal development and progressive degeneration of the sensory and autonomic nervous system. The mutation observed in almost all FD patients is a point mutation at position 6 of intron 20 of the IKBKAP gene; this gene encodes the IκB kinase complex-associated protein (IKAP). The mutation results in a tissue-specific splicing defect: Exon 20 is skipped, leading to reduced IKAP protein expression. Here we show that phosphatidylserine (PS), an FDA-approved food supplement, increased IKAP mRNA levels in cells derived from FD patients. Long-term treatment with PS led to a significant increase in IKAP protein levels in these cells. A conjugate of PS and an omega-3 fatty acid also increased IKAP mRNA levels. Furthermore, PS treatment released FD cells from cell cycle arrest and up-regulated a significant number of genes involved in cell cycle regulation. Our results suggest that PS has potential for use as a therapeutic agent for FD. Understanding its mechanism of action may reveal the mechanism underlying the FD disease.

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          Most cited references 54

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          Modeling Pathogenesis and Treatment of Familial Dysautonomia using Patient Specific iPSCs

          SUMMARY The isolation of human induced pluripotent stem cells (iPSCs)1-3 offers a novel strategy for modeling human disease. Recent studies have reported the derivation and differentiation of disease-specific human iPSCs4-7. However, a key challenge in the field is the demonstration of disease-related phenotypes and the ability to model pathogenesis and treatment of disease in iPSCs. Familial dysautonomia (FD) is a rare but fatal peripheral neuropathy caused by a point mutation in IKBKAP 8 involved in transcriptional elongation9. The disease is characterized by the depletion of autonomic and sensory neurons. The specificity to the peripheral nervous system and the mechanism of neuron loss in FD are poorly understood due to the lack of an appropriate model system. Here we report the derivation of patient specific FD-iPSCs and the directed differentiation into cells of all three germ layers including peripheral neurons. Gene expression analysis in purified FD-iPSC derived lineages demonstrates tissue specific mis-splicing of IKBKAP in vitro. Patient-specific neural crest precursors express particularly low levels of normal IKBKAP transcript suggesting a mechanism for disease specificity. FD pathogenesis is further characterized by transcriptome analysis and cell based assays revealing marked defects in neurogenic differentiation and migration behavior. Finally, we use FD-iPSCs for validating the potency of candidate drugs in reversing aberrant splicing and ameliorating neuronal differentiation and migration. Our study illustrates the promise of iPSC technology for gaining novel insights into human disease pathogenesis and treatment.
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            Elevated levels of two tRNA species bypass the requirement for elongator complex in transcription and exocytosis.

            The Saccharomyces cerevisiae Elongator complex consisting of the six Elp1-Elp6 proteins has been proposed to participate in three distinct cellular processes: transcriptional elongation, polarized exocytosis, and formation of modified wobble uridines in tRNA. Therefore it was important to clarify whether Elongator has three distinct functions or whether it regulates one key process that leads to multiple downstream effects. Here, we show that the phenotypes of Elongator-deficient cells linking the complex to transcription and exocytosis are suppressed by increased expression of two tRNA species. Elongator is required for formation of the mcm(5) group of the modified wobble nucleoside 5-methoxycarbonylmethyl-2-thiouridine (mcm(5)s(2)U) in these tRNAs. Hence, in cells with normal levels of these tRNAs, presence of mcm(5)s(2)U is crucial for posttranscriptional expression of gene products important in transcription and exocytosis. Our results indicate that the physiologically relevant function of the evolutionary-conserved Elongator complex is in formation of modified nucleosides in tRNAs.
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              Nonsense-mediated mRNA decay in human cells: mechanistic insights, functions beyond quality control and the double-life of NMD factors.

              Nonsense-mediated decay is well known by the lucid definition of being a RNA surveillance mechanism that ensures the speedy degradation of mRNAs containing premature translation termination codons. However, as we review here, NMD is far from being a simple quality control mechanism; it also regulates the stability of many wild-type transcripts. We summarise the abundance of research that has characterised each of the NMD factors and present a unified model for the recognition of NMD substrates. The contentious issue of how and where NMD occurs is also discussed, particularly with regard to P-bodies and SMG6-driven endonucleolytic degradation. In recent years, the discovery of additional functions played by several of the NMD factors has further complicated the picture. Therefore, we also review the reported roles of UPF1, SMG1 and SMG6 in other cellular processes.
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                Author and article information

                Contributors
                Role: Editor
                Journal
                PLoS One
                plos
                plosone
                PLoS ONE
                Public Library of Science (San Francisco, USA )
                1932-6203
                2010
                29 December 2010
                : 5
                : 12
                Affiliations
                [1 ]Department of Human Molecular Genetics and Biochemistry, Sackler Faculty of Medicine, Tel Aviv University, Ramat Aviv, Israel
                [2 ]Department of Cell Research and Immunology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv, Israel
                [3 ]Department of Pediatrics, Hadassah University Hospital, Mount Scopus, Jerusalem, Israel
                Centre de Regulació Genòmica, Spain
                Author notes

                Conceived and designed the experiments: HK GA. Performed the experiments: HK MD. Analyzed the data: HK DZ. Contributed reagents/materials/analysis tools: HK MD DZ TP CM GA. Wrote the paper: HK.

                Article
                PONE-D-10-03309
                10.1371/journal.pone.0015884
                3012102
                21209961
                Keren et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
                Page count
                Pages: 12
                Categories
                Research Article
                Biology
                Genetics
                Human Genetics
                Autosomal Recessive
                Gene Splicing
                Genetics of Disease
                Medicine
                Clinical Genetics
                Autosomal Recessive
                Neurology
                Autonomic Nervous System

                Uncategorized

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