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Duan HD, Li H. Consensus, controversies, and conundrums of P4-ATPases: The emerging face of eukaryotic lipid flippases. J Biol Chem 2024; 300:107387. [PMID: 38763336 PMCID: PMC11225554 DOI: 10.1016/j.jbc.2024.107387] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2024] [Revised: 05/04/2024] [Accepted: 05/07/2024] [Indexed: 05/21/2024] Open
Abstract
The cryo-EM resolution revolution has heralded a new era in our understanding of eukaryotic lipid flippases with a rapidly growing number of high-resolution structures. Flippases belong to the P4 family of ATPases (type IV P-type ATPases) that largely follow the reaction cycle proposed for the more extensively studied cation-transporting P-type ATPases. However, unlike the canonical P-type ATPases, no flippase cargos are transported in the phosphorylation half-reaction. Instead of being released into the intracellular or extracellular milieu, lipid cargos are transported to their destination at the inner leaflet of the membrane. Recent flippase structures have revealed multiple conformational states during the lipid transport cycle. Nonetheless, critical conformational states capturing the lipid cargo "in transit" are still missing. In this review, we highlight the amazing structural advances of these lipid transporters, discuss various perspectives on catalytic and regulatory mechanisms in the literature, and shed light on future directions in further deciphering the detailed molecular mechanisms of lipid flipping.
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Affiliation(s)
- H Diessel Duan
- Department of Structural Biology, Van Andel Institute, Grand Rapids, Michigan, USA.
| | - Huilin Li
- Department of Structural Biology, Van Andel Institute, Grand Rapids, Michigan, USA.
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2
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Yang Y, Sun K, Liu W, Li X, Tian W, Shuai P, Zhu X. The phosphatidylserine flippase β-subunit Tmem30a is essential for normal insulin maturation and secretion. Mol Ther 2021; 29:2854-2872. [PMID: 33895325 PMCID: PMC8417432 DOI: 10.1016/j.ymthe.2021.04.026] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2020] [Revised: 03/17/2021] [Accepted: 04/19/2021] [Indexed: 12/12/2022] Open
Abstract
The processing, maturation, and secretion of insulin are under precise regulation, and dysregulation causes profound defects in glucose handling, leading to diabetes. Tmem30a is the β subunit of the phosphatidylserine (PS) flippase, which maintains the membrane asymmetric distribution of PS. Tmem30a regulates cell survival and the localization of subcellular structures and is thus critical to the normal function of multiple physiological systems. Here, we show that conditional knockout of Tmem30a specifically in pancreatic islet β cells leads to obesity, hyperglycemia, glucose intolerance, hyperinsulinemia, and insulin resistance in mice, due to insufficient insulin release. Moreover, we reveal that Tmem30a plays an essential role in clathrin-mediated vesicle transport between the trans Golgi network (TGN) and the plasma membrane (PM), which comprises immature secretory granule (ISG) budding at the TGN. We also find that Tmem30a deficiency impairs clathrin-mediated vesicle budding and thus blocks both insulin maturation in ISGs and the transport of glucose-sensing Glut2 to the PM. Collectively, these disruptions compromise both insulin secretion and glucose sensitivity, thus contributing to impairments in glucose-stimulated insulin secretion. Taken together, our data demonstrate an important role of Tmem30a in insulin maturation and glucose metabolic homeostasis and suggest the importance of membrane phospholipid distribution in metabolic disorders.
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Affiliation(s)
- Yeming Yang
- Health Management Center, Sichuan Provincial People's Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu, Sichuan 610072, China; The Sichuan Provincial Key Laboratory for Human Disease Gene Study, Center for Medical Genetics, Prenatal Diagnosis Center, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, Sichuan 610072, China
| | - Kuanxiang Sun
- The Sichuan Provincial Key Laboratory for Human Disease Gene Study, Center for Medical Genetics, Prenatal Diagnosis Center, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, Sichuan 610072, China
| | - Wenjing Liu
- The Sichuan Provincial Key Laboratory for Human Disease Gene Study, Center for Medical Genetics, Prenatal Diagnosis Center, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, Sichuan 610072, China
| | - Xiao Li
- The Sichuan Provincial Key Laboratory for Human Disease Gene Study, Center for Medical Genetics, Prenatal Diagnosis Center, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, Sichuan 610072, China
| | - Wanli Tian
- The Sichuan Provincial Key Laboratory for Human Disease Gene Study, Center for Medical Genetics, Prenatal Diagnosis Center, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, Sichuan 610072, China
| | - Ping Shuai
- Health Management Center, Sichuan Provincial People's Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu, Sichuan 610072, China; The Sichuan Provincial Key Laboratory for Human Disease Gene Study, Center for Medical Genetics, Prenatal Diagnosis Center, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, Sichuan 610072, China; Research Unit for Blindness Prevention of Chinese Academy of Medical Sciences (2019RU026), Sichuan Academy of Medical Sciences and Sichuan Provincial People's Hospital, Chengdu, Sichuan 610072 China.
| | - Xianjun Zhu
- Health Management Center, Sichuan Provincial People's Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu, Sichuan 610072, China; The Sichuan Provincial Key Laboratory for Human Disease Gene Study, Center for Medical Genetics, Prenatal Diagnosis Center, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, Sichuan 610072, China; Key Laboratory of Tibetan Medicine Research, Chinese Academy of Sciences and Qinghai Provincial Key Laboratory of Tibetan Medicine Research, Northwest Institute of Plateau Biology, Xining, Qinghai 810008, China; Research Unit for Blindness Prevention of Chinese Academy of Medical Sciences (2019RU026), Sichuan Academy of Medical Sciences and Sichuan Provincial People's Hospital, Chengdu, Sichuan 610072 China; Natural Products Research Center, Institute of Chengdu Biology, Sichuan Translational Medicine Hospital, Chinese Academy of Sciences, Chengdu, Sichuan 610072, China; Department of Ophthalmology, First People's Hospital of Shangqiu, Shangqiu, Hennan 476100, China.
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3
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Ehrhart F, Janssen KJM, Coort SL, Evelo CT, Curfs LMG. Prader-Willi syndrome and Angelman syndrome: Visualisation of the molecular pathways for two chromosomal disorders. World J Biol Psychiatry 2019; 20:670-682. [PMID: 29425059 DOI: 10.1080/15622975.2018.1439594] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Objectives: Prader-Willi syndrome (PWS) and Angelman syndrome (AS) are two syndromes that are caused by the same chromosomal deletion on 15q11.2-q13. Due to methylation patterns, different genes are responsible for the two distinct phenotypes resulting in the disorders. Patients of both disorders exhibit hypotonia in neonatal stage, delay in development and hypopigmentation. Typical features for PWS include hyperphagia, which leads to obesity, the major cause of mortality, and hypogonadism. In AS, patients suffer from a more severe developmental delay, they have a distinctive behaviour that is often described as unnaturally happy, and a tendency for epileptic seizures. For both syndromes, we identified and visualised molecular downstream pathways of the deleted genes that could give insight on the development of the clinical features.Methods: This was done by consulting literature, genome browsers and pathway databases to identify molecular interactions and to construct downstream pathways.Results: A pathway visualisation was created and uploaded to the open pathway database WikiPathways covering all molecular pathways that were found.Conclusions: The visualisation of the downstream pathways of PWS- and AS-deleted genes shows that some of the typical symptoms are caused by multiple genes and reveals critical gaps in the current knowledge.
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Affiliation(s)
- Friederike Ehrhart
- GCK, Maastricht University Medical Centre, Maastricht, The Netherlands.,Department of Bioinformatics - BiGCaT, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University, Maastricht, The Netherlands
| | - Kelly J M Janssen
- GCK, Maastricht University Medical Centre, Maastricht, The Netherlands.,Department of Bioinformatics - BiGCaT, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University, Maastricht, The Netherlands
| | - Susan L Coort
- Department of Bioinformatics - BiGCaT, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University, Maastricht, The Netherlands
| | - Chris T Evelo
- GCK, Maastricht University Medical Centre, Maastricht, The Netherlands.,Department of Bioinformatics - BiGCaT, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University, Maastricht, The Netherlands
| | - Leopold M G Curfs
- Department of Bioinformatics - BiGCaT, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University, Maastricht, The Netherlands
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4
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Takar M, Huang Y, Graham TR. The PQ-loop protein Any1 segregates Drs2 and Neo1 functions required for viability and plasma membrane phospholipid asymmetry. J Lipid Res 2019; 60:1032-1042. [PMID: 30824614 PMCID: PMC6495175 DOI: 10.1194/jlr.m093526] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2019] [Indexed: 02/06/2023] Open
Abstract
Membrane asymmetry is a key organizational feature of the plasma membrane. Type IV P-type ATPases (P4-ATPases) are phospholipid flippases that establish membrane asymmetry by translocating phospholipids, such as phosphatidylserine (PS) and phospatidylethanolamine, from the exofacial leaflet to the cytosolic leaflet. Saccharomyces cerevisiae expresses five P4-ATPases: Drs2, Neo1, Dnf1, Dnf2, and Dnf3. The inactivation of Neo1 is lethal, suggesting Neo1 mediates an essential function not exerted by the other P4-ATPases. However, the disruption of ANY1, which encodes a PQ-loop membrane protein, allows the growth of neo1Δ and reveals functional redundancy between Golgi-localized Neo1 and Drs2. Here we show Drs2 PS flippase activity is required to support neo1Δ any1Δ viability. Additionally, a Dnf1 variant with enhanced PS flipping ability can replace Drs2 and Neo1 function in any1Δ cells. any1Δ also suppresses drs2Δ growth defects but not the loss of membrane asymmetry. Any1 overexpression perturbs the growth of cells but does not disrupt membrane asymmetry. Any1 coimmunoprecipitates with Neo1, an association prevented by the Any1-inactivating mutation D84G. These results indicate a critical role for PS flippase activity in Golgi membranes to sustain viability and suggests Any1 regulates Golgi membrane remodeling through protein-protein interactions rather than a previously proposed scramblase activity.
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Affiliation(s)
- Mehmet Takar
- Department of Biological Sciences, Vanderbilt University, Nashville, TN 37235
| | - Yannan Huang
- Department of Biological Sciences, Vanderbilt University, Nashville, TN 37235
| | - Todd R Graham
- Department of Biological Sciences, Vanderbilt University, Nashville, TN 37235.
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Huang L, Tepaamorndech S, Kirschke CP, Cai Y, Zhao J, Cao X, Rao A. Subcongenic analysis of a quantitative trait locus affecting body weight and glucose metabolism in zinc transporter 7 (znt7)-knockout mice. BMC Genet 2019; 20:19. [PMID: 30777014 PMCID: PMC6378724 DOI: 10.1186/s12863-019-0715-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2018] [Accepted: 01/11/2019] [Indexed: 11/24/2022] Open
Abstract
Background A genome-wide mapping study using male F2zinc transporter 7-knockout mice (znt7-KO) and their wild type littermates in a mixed 129P1/ReJ (129P1) and C57BL/6J (B6) background identified a quantitative trait locus (QTL) on chromosome 7, which had a synergistic effect on body weight gain and fat deposit with the znt7-null mutation. Results The genetic segment for body weight on mouse chromosome 7 was investigated by newly created subcongenic znt7-KO mouse strains carrying different lengths of genomic segments of chromosome 7 from the 129P1 donor strain in the B6 background. We mapped the sub-QTL for body weight in the proximal region of the previously mapped QTL, ranging from 47.4 to 64.4 megabases (Mb) on chromosome 7. The 129P1 donor allele conferred lower body weight gain and better glucose handling during intraperitoneal glucose challenge than the B6 allele control. We identified four candidate genes, including Htatip2, E030018B13Rik, Nipa1, and Atp10a, in this sub-QTL using quantitative RT-PCR and cSNP detection (single nucleotide polymorphisms in the protein coding region). Conclusions This study dissected the genetic determinates of body weight and glucose metabolism in znt7-KO mice. The study demonstrated that a 17-Mb long 129P1 genomic region on mouse chromosome 7 conferred weight reduction and improved glucose tolerance in znt7-KO male mice. Among the four candidate genes identified, Htatip2 is the most likely candidate gene involved in the control of body weight based on its function in regulation of lipid metabolism. The candidate genes discovered in this study lay a foundation for future studies of their roles in development of metabolic diseases, such as obesity and type 2 diabetes. Electronic supplementary material The online version of this article (10.1186/s12863-019-0715-2) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- L Huang
- Obesity and Metabolism Research Unit, USDA/ARS/Western Human Nutrition Research Center, 430 West Health Sciences Drive, Davis, CA, 95616, USA.
| | - S Tepaamorndech
- Integrative Genetics and Genomics Graduate Group, University of California Davis, One Shields Avenue, Davis, CA, 95616, USA.,Present Address: Food Biotechnology Research Unit, National Center for Genetic Engineering and Biotechnology (BIOTEC), 113 Thailand Science Park, Phahonyothin Road, Pathum Thani, 12120, Thailand
| | - C P Kirschke
- Obesity and Metabolism Research Unit, USDA/ARS/Western Human Nutrition Research Center, 430 West Health Sciences Drive, Davis, CA, 95616, USA
| | - Y Cai
- Graduate Group of Nutritional Biology, University of California Davis, One Shields Avenue, Davis, CA, 95616, USA
| | - J Zhao
- Department of Nutrition, University of California Davis, One Shields Avenue, Davis, CA, 95616, USA.,School of Food Science, Nanjing Xiaozhuang University, Nanjing, 211171, Jiangsu, China
| | - Xiaohan Cao
- Food Science and Technology, University of California Davis, One Shields Avenue, Davis, CA, 95616, USA
| | - Andrew Rao
- Department of Nutrition, University of California Davis, One Shields Avenue, Davis, CA, 95616, USA
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6
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Transient Silencing of a Type IV P-Type ATPase, Atp10c, Results in Decreased Glucose Uptake in C2C12 Myotubes. J Nutr Metab 2012; 2012:152902. [PMID: 22474575 PMCID: PMC3317196 DOI: 10.1155/2012/152902] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2011] [Revised: 10/15/2011] [Accepted: 10/29/2011] [Indexed: 11/26/2022] Open
Abstract
Atp10c is a strong candidate gene for diet-induced obesity and type 2 diabetes. To identify molecular and cellular targets of ATP10C, Atp10c expression was altered in vitro in C2C12 skeletal muscle myotubes by transient transfection with an Atp10c-specific siRNA. Glucose uptake assays revealed that insulin stimulation caused a significant 2.54-fold decrease in 2-deoxyglucose uptake in transfected cells coupled with a significant upregulation of native mitogen-activated protein kinases (MAPKs), p38, and p44/42. Additionally, glucose transporter-1 (GLUT1) was significantly upregulated; no changes in glucose transporter-4 (GLUT4) expression were observed. The involvement of MAPKs was confirmed using the specific inhibitor SB203580, which downregulated the expression of native and phosphorylated MAPK proteins in transfected cells without any changes in insulin-stimulated glucose uptake. Results indicate that Atp10c regulates glucose metabolism, at least in part via the MAPK pathway, and, thus, plays a significant role in the development of insulin resistance and type 2 diabetes.
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Sebastian TT, Baldridge RD, Xu P, Graham TR. Phospholipid flippases: building asymmetric membranes and transport vesicles. Biochim Biophys Acta Mol Cell Biol Lipids 2011; 1821:1068-77. [PMID: 22234261 DOI: 10.1016/j.bbalip.2011.12.007] [Citation(s) in RCA: 173] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2011] [Revised: 12/14/2011] [Accepted: 12/16/2011] [Indexed: 01/25/2023]
Abstract
Phospholipid flippases in the type IV P-type ATPase family (P4-ATPases) are essential components of the Golgi, plasma membrane and endosomal system that play critical roles in membrane biogenesis. These pumps flip phospholipid across the bilayer to create an asymmetric membrane structure with substrate phospholipids, such as phosphatidylserine and phosphatidylethanolamine, enriched within the cytosolic leaflet. The P4-ATPases also help form transport vesicles that bud from Golgi and endosomal membranes, thereby impacting the sorting and localization of many different proteins in the secretory and endocytic pathways. At the organismal level, P4-ATPase deficiencies are linked to liver disease, obesity, diabetes, hearing loss, neurological deficits, immune deficiency and reduced fertility. Here, we review the biochemical, cellular and physiological functions of P4-ATPases, with an emphasis on their roles in vesicle-mediated protein transport. This article is part of a Special Issue entitled Lipids and Vesicular Transport.
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Affiliation(s)
- Tessy T Sebastian
- Department of Biological Sciences, Vanderbilt University, Nashville TN 37235, USA
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DuBose AJ, Johnstone KA, Smith EY, Hallett RAE, Resnick JL. Atp10a, a gene adjacent to the PWS/AS gene cluster, is not imprinted in mouse and is insensitive to the PWS-IC. Neurogenetics 2009; 11:145-51. [PMID: 19894069 DOI: 10.1007/s10048-009-0226-9] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2009] [Accepted: 10/09/2009] [Indexed: 10/20/2022]
Abstract
Mutations affecting a cluster of coordinately regulated imprinted genes located at 15q11-q13 underlie both Prader-Willi syndrome (PWS) and Angelman syndrome (AS). Disruption of the predominately maternally expressed UBE3A locus is sufficient to meet diagnostic criteria for AS. However, AS patients with a deletion of the entire PWS/AS locus often have more severe traits than patients with point mutations in UBE3A suggesting that other genes contribute to the syndrome. ATP10A resides 200 kb telomeric to UBE3A and is of uncertain imprinted status. An initial report indicated bialleleic expression of the murine Atp10a in all tissues, but a subsequent report suggests that Atp10a is predominantly maternally expressed in the hippocampus and olfactory bulb. To resolve this discrepancy, we investigated Atp10a allelic expression in the brain, DNA methylation status, and sensitivity to mutations of the PWS imprinting center, an element required for imprinted gene expression in the region. We report that Atp10a is biallelically expressed in both the newborn and adult brain, and Atp10a allelic expression is insensitive to deletion or mutation of the PWS imprinting center. The CpG island associated with Atp10a is hypomethylated, a result consistent with the notion that Atp10a is not an imprinted gene.
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Affiliation(s)
- Amanda J DuBose
- Department of Molecular Genetics and Microbiology, University of Florida College of Medicine, Gainesville, Florida, 32610-0266, USA
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Dhar MS, Hauser LJ, Nicholls RD, Johnson DK. Physical Mapping of thePink-Eyed DilutionComplex in Mouse Chromosome 7 shows thatAtp10cis the only Transcript betweenGabrb3andUbe3a. ACTA ACUST UNITED AC 2009; 15:306-9. [PMID: 15620220 DOI: 10.1080/10425170412331279855] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Phenotypic analyses of a set of homozygous-lethal deletion mutants at the pink-eyed dilution (p) locus has resulted in the identification of p-linked obesity locus 1 (plo 1), distal to the p locus, as a locus involved in the modulation of body fat and/or affecting lipid metabolism in these mice. The plo 1 region maps to mouse chromosome 7 (MMU 7) between two genes, Gabrb3 and Ube3a, which have been used as anchor points to generate an integrated deletion and physical map of plo 1 that encompasses about 1.2-1.3 Mb. A deletion/physical map was constructed and the genomic DNA between the two loci was sequenced to identify genes mapping to this region. Data show that Atp10c, a novel type IV ATPase a putative phospholipid transporter, is the only coding unit in this region of the chromosome.
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Affiliation(s)
- Madhu S Dhar
- 318 Jessie Harris Building, Department of Nutrition, University of Tennessee, 1215 Cumberland Avenue, Knoxville, TN 37996, USA.
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Folmer DE, Elferink RPJO, Paulusma CC. P4 ATPases - lipid flippases and their role in disease. Biochim Biophys Acta Mol Cell Biol Lipids 2009; 1791:628-35. [PMID: 19254779 DOI: 10.1016/j.bbalip.2009.02.008] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2009] [Revised: 02/12/2009] [Accepted: 02/12/2009] [Indexed: 12/11/2022]
Abstract
P4 ATPases (type 4 P-type ATPases) are multispan transmembrane proteins that have been implicated in phospholipid translocation from the exoplasmic to the cytoplasmic leaflet of biological membranes. Studies in Saccharomyces cerevisiae have indicated that P4 ATPases are important in vesicle biogenesis and are required for vesicular trafficking along several intracellular vesicular transport routes. Although little is known about mammalian P4 ATPases, some members of this subfamily appear to be associated with human disease or mouse pathophysiology. ATP8B1, a phosphatidylserine translocase, is the most extensively studied mammalian P4 ATPase. This protein is important for maintaining the detergent resistant properties of the apical membrane of the hepatocyte. Mutations in ATP8B1 give rise to severe liver disease. Furthermore, a role for Atp8b3 in mouse sperm cell capacitation has been suggested, whereas deficiency of Atp10a and Atp10d leads to insulin resistance and obesity in mice. Here we review the present status on the pathophysiological consequences of P4 ATPase deficiency.
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Affiliation(s)
- Dineke E Folmer
- AMC Liver Center, Academic Medical Center, University of Amsterdam, Meibergdreef 69-71, 1105BK Amsterdam, The Netherlands
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Speakman J, Hambly C, Mitchell S, Król E. The contribution of animal models to the study of obesity. Lab Anim 2008; 42:413-32. [PMID: 18782824 DOI: 10.1258/la.2007.006067] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Obesity results from prolonged imbalance of energy intake and energy expenditure. Animal models have provided a fundamental contribution to the historical development of understanding the basic parameters that regulate the components of our energy balance. Five different types of animal model have been employed in the study of the physiological and genetic basis of obesity. The first models reflect single gene mutations that have arisen spontaneously in rodent colonies and have subsequently been characterized. The second approach is to speed up the random mutation rate artificially by treating rodents with mutagens or exposing them to radiation. The third type of models are mice and rats where a specific gene has been disrupted or over-expressed as a deliberate act. Such genetically-engineered disruptions may be generated through the entire body for the entire life (global transgenic manipulations) or restricted in both time and to certain tissue or cell types. In all these genetically-engineered scenarios, there are two types of situation that lead to insights: where a specific gene hypothesized to play a role in the regulation of energy balance is targeted, and where a gene is disrupted for a different purpose, but the consequence is an unexpected obese or lean phenotype. A fourth group of animal models concern experiments where selective breeding has been utilized to derive strains of rodents that differ in their degree of fatness. Finally, studies have been made of other species including non-human primates and dogs. In addition to studies of the physiological and genetic basis of obesity, studies of animal models have also informed us about the environmental aspects of the condition. Studies in this context include exploring the responses of animals to high fat or high fat/high sugar (Cafeteria) diets, investigations of the effects of dietary restriction on body mass and fat loss, and studies of the impact of candidate pharmaceuticals on components of energy balance. Despite all this work, there are many gaps in our understanding of how body composition and energy storage are regulated, and a continuing need for the development of pharmaceuticals to treat obesity. Accordingly, reductions in the use of animal models, while ethically desirable, will not be feasible in the short to medium term, and indeed an expansion in activity using animal models is anticipated as the epidemic continues and spreads geographically.
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Affiliation(s)
- John Speakman
- Aberdeen Centre for Energy Regulation and Obesity, School of Biological Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK.
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12
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Hogart A, Patzel KA, LaSalle JM. Gender influences monoallelic expression of ATP10A in human brain. Hum Genet 2008; 124:235-42. [PMID: 18726118 DOI: 10.1007/s00439-008-0546-0] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2008] [Accepted: 08/14/2008] [Indexed: 10/21/2022]
Abstract
Human chromosome 15q11-13 and the syntenic region of mouse chromosome 7 contain multiple imprinted genes necessary for proper neurodevelopment. Due to imprinting, paternal 15q11-13 deficiencies lead to Prader-Willi syndrome (PWS) while maternal 15q11-13 deficiencies cause Angelman syndrome (AS). The mechanisms involved in parental imprinting of this locus are conserved between human and mouse, yet inconsistencies exist in reports of imprinting of the maternally expressed gene Atp10a/ATP10A. Excess maternal 15q11-13 dosage often leads to autism-spectrum disorder therefore further investigation to characterize the true imprinting status of ATP10A in humans was warranted. In this study, we examined allelic expression of ATP10A transcript in 16 control brain samples, and found that 10/16 exhibited biallelic expression while only 6/16 showed monoallelic expression. Contrary to the expectation for a maternally expressed imprinted gene, quantitative RT-PCR revealed significantly reduced ATP10A transcript in Prader-Willi syndrome brains with two maternal chromosomes due to uniparental disomy (PWS UPD). Furthermore, a PWS UPD brain sample with monoallelic ATP10A expression demonstrated that monoallelic expression can be independent of imprinting. Investigation of factors that may influence allelic ATP10A expression status revealed that gender has a major affect, as females were significantly more likely to have monoallelic ATP10A expression than males. Regulatory sequences were also examined, and a promoter polymorphism that disrupts binding of the transcription factor Sp1 also potentially contributes to allelic expression differences in females. Our results show that monoallelic expression of human ATP10A is variable in the population and is influenced by both gender and common genetic variation.
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Affiliation(s)
- Amber Hogart
- Medical Microbiology and Immunology, Rowe Program in Human Genetics, School of Medicine, University of California, One Shields Ave, Davis, CA 95616, USA.
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Reed DR, McDaniel AH, Avigdor M, Bachmanov AA. QTL for body composition on chromosome 7 detected using a chromosome substitution mouse strain. Obesity (Silver Spring) 2008; 16:483-7. [PMID: 18239664 PMCID: PMC2266090 DOI: 10.1038/oby.2007.26] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
OBJECTIVE Previous studies in mice have detected quantitative trait loci (QTLs) on chromosome 7 that affect body composition. As a step toward identifying the responsible genes, we compared a chromosome 7 substitution strain C57BL/6J-Chr7(129S1/SvImJ)/Na (CSS-7) to its host (C57BL/6J) strain. METHODS AND PROCEDURES Fourteen-week-old mice were measured for body size (weight, length), organ weight (brain, heart, liver, kidneys, and spleen), body and bone composition (fat and lean weight; bone area, mineral content, and density), and individual adipose depot weights (gonadal, retroperitoneal, mesenteric, inguinal, and subscapular). Differences between the CSS-7 strain and the host strain were interpreted as evidence for the presence of one or more QTLs on chromosome 7. RESULTS Using this criterion, we detected QTLs for body weight, bone area, bone mineral content, brain, and heart weight, most adipose depot weights and some indices of fatness. A few strain differences were more pronounced in males (e.g., most adiposity measures) and others were more pronounced in females (e.g., bone area). QTLs for body length, lean weight, bone mineral density, and kidney, spleen, and liver weight were not detected. DISCUSSION This study found several associations that suggest one or more QTLs specific to the weight of select tissues and organs exist on mouse chromosome 7. Because these loci are detectable on a fixed and uniform genetic background, they are reasonable targets for high-resolution mapping and gene identification using a congenic approach.
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Imprinted Genes, Postnatal Adaptations and Enduring Effects on Energy Homeostasis. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2008; 626:41-61. [DOI: 10.1007/978-0-387-77576-0_4] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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15
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Affiliation(s)
- J Speakman
- Aberdeen Centre for Energy Regulation and Obesity, School of Biological Sciences, University of Aberdeen, Aberdeen, UK.
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16
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Reed DR, McDaniel AH, Li X, Tordoff MG, Bachmanov AA. Quantitative trait loci for individual adipose depot weights in C57BL/6ByJ x 129P3/J F2 mice. Mamm Genome 2006; 17:1065-77. [PMID: 17103053 PMCID: PMC1702371 DOI: 10.1007/s00335-006-0054-2] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2006] [Accepted: 06/28/2006] [Indexed: 10/23/2022]
Abstract
To understand how genotype influences fat patterning and obesity, we conducted an autosomal genome scan using male and female F(2) hybrids between the C57BL/6ByJ and 129P3/J parental mouse strains. Mice were studied in middle-adulthood and were fed a low-energy, low-fat diet during their lifetime. We measured the weight of the retroperitoneal adipose depot (near the kidney) and the gonadal adipose depot (near the epididymis in males and ovaries in females). An important feature of the analysis was the comparison of linkage results for absolute adipose depot weight and depot weight adjusted for body size, i.e., relative weight. We detected 67 suggestive linkages for six phenotypes, which fell into one of three categories: those specific to absolute but not relative depot weight (Chr 5, 11, and 14), those specific to relative but not absolute depot weight (Chr 9, 15, and 16), and those involving both (Chr 2 and 7). Some quantitative trait loci (QTLs) affected one adipose depot more than another: Retroperitoneal depot weight was linked to Chr 8, 11, 12, and 17, but the linkage effects for the gonadal depot were stronger for Chr 5, 7, and 9. Several linkages were specific to sex; for instance, the absolute weight of gonadal fat was linked to Chromosome 7 in male (LOD = 3.4) but not female mice (LOD = 0.2). Refining obesity as a phenotype may uncover clues about gene function that will assist in positional cloning efforts.
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Affiliation(s)
- Danielle R Reed
- Monell Chemical Senses Center, 3500 Market Street, Philadelphia, Pennsylvania 19104, USA.
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17
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Abstract
Many cave animals are colorless due to loss of pigment cells. Here, we review recent progress on how and why pigmentation has disappeared inAstyanax mexicanus, a single teleost species with conspecific surface-dwelling (surface fish) and many different cave-dwelling (cavefish) forms. During surface fish development, migratory neural crest cells form three types of pigment cells: silver iridophores, orange xanthophores, and black melanophores. Cavefish have eliminated or substantially reduced their complement of melanophores and exhibit albinism, loss of the capacity to synthesize melanin. Cell tracing, immunolocalization, and neural tube explant cultures show that cavefish have retained a colorless pre-melanophore (melanoblast) lineage derived from the neural crest. Thus, the cavefish neural crest produces melanoblasts that migrate normally but are blocked in differentiation and show defective melanogenesis. Cavefish melanoblasts can convert exogenous L-DOPA into melanin and therefore have active tyrosinase, the key enzyme in melanogenesis. In contrast, cavefish melanoblasts are unable to convert L-tyrosine to L-DOPA (and melanin), although this reaction is also catalyzed by tyrosinase. Thus, cavefish are tyrosinase-positive albinos that have a deficiency in L-tyrosine transport or utilization within the melanosome, the organelle in which melanin is synthesized. At least five different types ofAstyanaxcavefish show the same defect in melanogenesis. Genetic analysis shows that cavefish albinism is caused by loss of function mutations in a single gene,p/oca2, which encodes a large protein that probably spans the melanosome membrane. Different deletions in thep/oca2 protein-coding region are responsible for loss of function in at least two different cavefish populations, suggesting that albinism evolved by convergence. Based on current understanding of the genetic basis of albinism, we discuss potential mechanisms for regressive evolution of cavefish pigmentation.
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18
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Rankinen T, Zuberi A, Chagnon YC, Weisnagel SJ, Argyropoulos G, Walts B, Pérusse L, Bouchard C. The human obesity gene map: the 2005 update. Obesity (Silver Spring) 2006; 14:529-644. [PMID: 16741264 DOI: 10.1038/oby.2006.71] [Citation(s) in RCA: 685] [Impact Index Per Article: 38.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
This paper presents the 12th update of the human obesity gene map, which incorporates published results up to the end of October 2005. Evidence from single-gene mutation obesity cases, Mendelian disorders exhibiting obesity as a clinical feature, transgenic and knockout murine models relevant to obesity, quantitative trait loci (QTL) from animal cross-breeding experiments, association studies with candidate genes, and linkages from genome scans is reviewed. As of October 2005, 176 human obesity cases due to single-gene mutations in 11 different genes have been reported, 50 loci related to Mendelian syndromes relevant to human obesity have been mapped to a genomic region, and causal genes or strong candidates have been identified for most of these syndromes. There are 244 genes that, when mutated or expressed as transgenes in the mouse, result in phenotypes that affect body weight and adiposity. The number of QTLs reported from animal models currently reaches 408. The number of human obesity QTLs derived from genome scans continues to grow, and we now have 253 QTLs for obesity-related phenotypes from 61 genome-wide scans. A total of 52 genomic regions harbor QTLs supported by two or more studies. The number of studies reporting associations between DNA sequence variation in specific genes and obesity phenotypes has also increased considerably, with 426 findings of positive associations with 127 candidate genes. A promising observation is that 22 genes are each supported by at least five positive studies. The obesity gene map shows putative loci on all chromosomes except Y. The electronic version of the map with links to useful publications and relevant sites can be found at http://obesitygene.pbrc.edu.
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Affiliation(s)
- Tuomo Rankinen
- Human Genomics Laboratory, Pennington Biomedical Research Center, Baton Rouge, LA 70808-4124, USA
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19
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Paterson JK, Renkema K, Burden L, Halleck MS, Schlegel RA, Williamson P, Daleke DL. Lipid Specific Activation of the Murine P4-ATPase Atp8a1 (ATPase II)†. Biochemistry 2006; 45:5367-76. [PMID: 16618126 DOI: 10.1021/bi052359b] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The asymmetric transbilayer distribution of phosphatidylserine (PS) in the mammalian plasma membrane and secretory vesicles is maintained, in part, by an ATP-dependent transporter. This aminophospholipid "flippase" selectively transports PS to the cytosolic leaflet of the bilayer and is sensitive to vanadate, Ca(2+), and modification by sulfhydryl reagents. Although the flippase has not been positively identified, a subfamily of P-type ATPases has been proposed to function as transporters of amphipaths, including PS and other phospholipids. A candidate PS flippase ATP8A1 (ATPase II), originally isolated from bovine secretory vesicles, is a member of this subfamily based on sequence homology to the founding member of the subfamily, the yeast protein Drs2, which has been linked to ribosomal assembly, the formation of Golgi-coated vesicles, and the maintenance of PS asymmetry. To determine if ATP8A1 has biochemical characteristics consistent with a PS flippase, a murine homologue of this enzyme was expressed in insect cells and purified. The purified Atp8a1 is inactive in detergent micelles or in micelles containing phosphatidylcholine, phosphatidic acid, or phosphatidylinositol, is minimally activated by phosphatidylglycerol or phosphatidylethanolamine (PE), and is maximally activated by PS. The selectivity for PS is dependent upon multiple elements of the lipid structure. Similar to the plasma membrane PS transporter, Atp8a1 is activated only by the naturally occurring sn-1,2-glycerol isomer of PS and not the sn-2,3-glycerol stereoisomer. Both flippase and Atp8a1 activities are insensitive to the stereochemistry of the serine headgroup. Most modifications of the PS headgroup structure decrease recognition by the plasma membrane PS flippase. Activation of Atp8a1 is also reduced by these modifications; phosphatidylserine-O-methyl ester, lysophosphatidylserine, glycerophosphoserine, and phosphoserine, which are not transported by the plasma membrane flippase, do not activate Atp8a1. Weakly translocated lipids (PE, phosphatidylhydroxypropionate, and phosphatidylhomoserine) are also weak Atp8a1 activators. However, N-methyl-phosphatidylserine, which is transported by the plasma membrane flippase at a rate equivalent to PS, is incapable of activating Atp8a1 activity. These results indicate that the ATPase activity of the secretory granule Atp8a1 is activated by phospholipids binding to a specific site whose properties (PS selectivity, dependence upon glycerol but not serine, stereochemistry, and vanadate sensitivity) are similar to, but distinct from, the properties of the substrate binding site of the plasma membrane flippase.
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Affiliation(s)
- Jill K Paterson
- Department of Biochemistry and Molecular Biology, Medical Sciences, Indiana University, Bloomington, Indiana 47405, USA
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20
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Dhar MS, Yuan JS, Elliott SB, Sommardahl C. A type IV P-type ATPase affects insulin-mediated glucose uptake in adipose tissue and skeletal muscle in mice. J Nutr Biochem 2006; 17:811-20. [PMID: 16517145 DOI: 10.1016/j.jnutbio.2006.01.002] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2005] [Revised: 12/27/2005] [Accepted: 01/03/2006] [Indexed: 11/27/2022]
Abstract
Mice carrying two pink-eyed dilution (p) locus heterozygous deletions represent a novel polygenic mouse model of type 2 diabetes associated with obesity. Atp10c, a putative aminophospholipid transporter on mouse chromosome 7, is a candidate for the phenotype. The phenotype is diet-induced. As a next logical step in the validation and characterization of the model, experiments to analyze metabolic abnormalities associated with these mice were carried out. Results demonstrate that mutants (inheriting the p deletion maternally) heterozygous for Atp10c are hyperinsulinemic, insulin-resistant and have an altered insulin-stimulated response in peripheral tissues. Adipose tissue and the skeletal muscle are the targets, and GLUT4-mediated glucose uptake is the specific metabolic pathway associated with Atp10c deletion. Insulin resistance primarily affects the adipose tissue and the skeletal muscle, and the effect in the liver is secondary. Gene expression profiling using microarray and real-time PCR show significant changes in the expression of four genes--Vamp2, Dok1, Glut4 and Mapk14--involved in insulin signaling. The expression of Atp10c is also significantly altered in the adipose tissue and the soleus muscle. The most striking observation is the loss of Atp10c expression in the mutants, specifically in the soleus muscle, after eating the high-fat diet for 12 weeks. In conclusion, experiments suggest that the target genes and/or their cognate factors in conjunction with Atp10c presumably affect the normal translocation and sequestration of GLUT4 in both the target tissues.
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Affiliation(s)
- Madhu S Dhar
- Large Animal Clinical Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, TN 37996-4500, USA.
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21
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Mamo S, Bodo S, Kobolak J, Polgar Z, Tolgyesi G, Dinnyes A. Gene expression profiles of vitrified in vivo derived 8-cell stage mouse embryos detected by high density oligonucleotide microarrays. Mol Reprod Dev 2006; 73:1380-92. [PMID: 16897732 DOI: 10.1002/mrd.20588] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Very little is known about the effect of vitrification on gene functions after warming. The goals of our study were to compare the gene expression patterns, and identify those most affected. For this, 8-cell stage embryos were collected from ICR mice and vitrified with solid surface vitrification technique, while maintaining equal numbers of embryos as control. Total RNAs were extracted and two rounds of amplification were employed. Finally three micrograms of contrasting RNA samples were hybridized on the Agilent Mouse 22 K oligonucleotide slides and the results were analyzed with subsequent verification by independent real-time PCR analyses. The two rounds of amplification with 5 ng tRNA input have yielded 15-16 microg of cRNA. The analyses of repeated hybridizations showed 20,183 genes/ESTs as common signatures, and unsupervised analysis identified 628 differentially expressed (P < 0.01) genes. However, with at least 1.5-fold change considerations, 183 genes were differentially expressed (P < 0.01) out of which 107 were upregulated. The independent analysis with real-time PCR and unamplified samples fully confirmed the results of microarray, indicating the linearity of amplification. Furthermore, this novel gene expression study for vitrified embryos identified many new candidate genes with overrepresentation in some important biological processes. Thus, it is possible to conclude that the expression pattern reflected a broad spectrum of consequences of vitrification on embryos, with most effects on metabolism, regulatory role and stress response genes and allowed the identification of new candidate marker genes for cryosurvival.
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Affiliation(s)
- Solomon Mamo
- Micromanipulation and Genetic Reprogramming Group, Agricultural Biotechnology Center, Gödöllo, Hungary.
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22
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Johnstone KA, DuBose AJ, Futtner CR, Elmore MD, Brannan CI, Resnick JL. A human imprinting centre demonstrates conserved acquisition but diverged maintenance of imprinting in a mouse model for Angelman syndrome imprinting defects. Hum Mol Genet 2005; 15:393-404. [PMID: 16368707 DOI: 10.1093/hmg/ddi456] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Prader-Willi syndrome (PWS) and Angelman syndrome (AS) are caused by the loss of imprinted gene expression from chromosome 15q11-q13. Imprinted gene expression in the region is regulated by a bipartite imprinting centre (IC), comprising the PWS-IC and the AS-IC. The PWS-IC is a positive regulatory element required for bidirectional activation of a number of paternally expressed genes. The function of the AS-IC appears to be to suppress PWS-IC function on the maternal chromosome through a methylation imprint acquired during female gametogenesis. Here we have placed the entire mouse locus under the control of a human PWS-IC by targeted replacement of the mouse PWS-IC with the equivalent human region. Paternal inheritance of the human PWS-IC demonstrates for the first time that a positive regulatory element in the PWS-IC has diverged. These mice show postnatal lethality and growth deficiency, phenotypes not previously attributed directly to the affected genes. Following maternal inheritance, the human PWS-IC is able to acquire a methylation imprint in mouse oocytes, suggesting that acquisition of the methylation imprint is conserved. However, the imprint is lost in somatic cells, showing that maintenance has diverged. This maternal imprinting defect results in expression of maternal Ube3a-as and repression of Ube3a in cis, providing evidence that Ube3a is regulated by its antisense and creating the first reported mouse model for AS imprinting defects.
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Affiliation(s)
- Karen A Johnstone
- Department of Molecular Genetics and Microbiology, Center for Mammalian Genetics, University of Florida College of Medicine, Gainesville, Fl 32610-0266, USA.
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23
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Ding F, Prints Y, Dhar MS, Johnson DK, Garnacho-Montero C, Nicholls RD, Francke U. Lack of Pwcr1/MBII-85 snoRNA is critical for neonatal lethality in Prader-Willi syndrome mouse models. Mamm Genome 2005; 16:424-31. [PMID: 16075369 DOI: 10.1007/s00335-005-2460-2] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2004] [Accepted: 03/14/2005] [Indexed: 10/25/2022]
Abstract
Prader-Willi syndrome (PWS) is a neurobehavioral disorder caused by the lack of paternal expression of imprinted genes in the human chromosome region 15q11-13. Recent studies of rare human translocation patients narrowed the PWS critical genes to a 121-kb region containing PWCR1/HBII-85 and HBII-438 snoRNA genes. The existing mouse models of PWS that lack the expression of multiple genes, including Snrpn, Ube3a, and many intronic snoRNA genes, are characterized by 80%-100% neonatal lethality. To define the candidate region for PWS-like phenotypes in mice, we analyzed the expression of several genetic elements in mice carrying the large radiation-induced p(30PUb) deletion that includes the p locus. Mice having inherited this deletion from either parent develop normally into adulthood. By Northern blot and RT-PCR assays of brain tissue, we found that Pwcr1/MBII-85 snoRNAs are expressed normally, while MBII-52 snoRNAs are not expressed when the deletion is paternally inherited. Mapping of the distal deletion breakpoint indicated that the p30PUb deletion includes the entire MBII-52 snoRNA gene cluster and three previously unmapped EST sequences. The lack of expression of these elements in mice with a paternal p30PUb deletion indicates that they are not critical for the neonatal lethality observed in PWS mouse models. In addition, we identified MBII-436, the mouse homolog of the HBII-436 snoRNA, confirmed its imprinting status, and mapped it outside of the p30PUb deletion. Taking together all available data, we conclude that the lack of Pwcr1/MBII-85 snoRNA expression is the most likely cause for the neonatal lethality in PWS model mice.
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Affiliation(s)
- Feng Ding
- Department of Genetics, Stanford University, Stanford, California 94305, USA
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24
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Paulusma CC, Oude Elferink RPJ. The type 4 subfamily of P-type ATPases, putative aminophospholipid translocases with a role in human disease. Biochim Biophys Acta Mol Basis Dis 2005; 1741:11-24. [PMID: 15919184 DOI: 10.1016/j.bbadis.2005.04.006] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2005] [Revised: 04/21/2005] [Accepted: 04/25/2005] [Indexed: 11/22/2022]
Abstract
The maintenance of phospholipid asymmetry in membrane bilayers is a paradigm in cell biology. However, the mechanisms and proteins involved in phospholipid translocation are still poorly understood. Members of the type 4 subfamily of P-type ATPases have been implicated in the translocation of phospholipids from the outer to the inner leaflet of membrane bilayers. In humans, several inherited disorders have been identified which are associated with loci harboring type 4 P-type ATPase genes. Up to now, one inherited disorder, Byler disease or progressive familial intrahepatic cholestasis type 1 (PFIC1), has been directly linked to mutations in a type 4 P-type ATPase gene. How the absence of an aminophospholipid translocase activity relates to this severe disease is, however, still unclear. Studies in the yeast Saccharomyces cerevisiae have recently identified important roles for type 4 P-type ATPases in intracellular membrane- and protein-trafficking events. These processes require an (amino)phospholipid translocase activity to initiate budding or fusion of membrane vesicles from or with other membranes. The studies in yeast have greatly contributed to our cell biological insight in membrane dynamics and intracellular-trafficking events; if this knowledge can be translated to mammalian cells and organs, it will help to elucidate the molecular mechanisms which underlie severe inherited human diseases such as Byler disease.
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Affiliation(s)
- C C Paulusma
- Department of Experimental Hepatology, Academic Medical Center/AMC Liver Center, Meibergdreef 69-71, 1105 BK Amsterdam, The Netherlands.
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25
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Landers M, Calciano MA, Colosi D, Glatt-Deeley H, Wagstaff J, Lalande M. Maternal disruption of Ube3a leads to increased expression of Ube3a-ATS in trans. Nucleic Acids Res 2005; 33:3976-84. [PMID: 16027444 PMCID: PMC1178004 DOI: 10.1093/nar/gki705] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Angelman syndrome (AS) is a neurogenetic disorder characterized by severe mental retardation, ‘puppet-like’ ataxic gait with jerky arm movements, seizures, EEG abnormalities, hyperactivity and bouts of inappropriate laughter. Individuals with AS fail to inherit a normal active maternal copy of the gene encoding ubiquitin protein ligase E3A (UBE3A). UBE3A is transcribed predominantly from the maternal allele in brain, but is expressed from both alleles in most other tissues. It has been proposed that brain-specific silencing of the paternal UBE3A allele is mediated by a large (>500 kb) paternal non-coding antisense transcript (UBE3A-ATS). There are several other examples of imprinting regulation involving antisense transcripts that share two main properties: (i) the sense transcript is repressed by antisense and (ii) the interaction between sense and antisense occurs in cis. We show here that, in a mouse model of AS, maternal transmission of Ube3a mutation leads to increased expression of the paternal Ube3a-ATS, suggesting that the antisense is modulated by sense rather than the reciprocal mode of regulation. Our observation that Ube3a regulates expression of Ube3a-ATS in trans is in contrast to the other cases of sense–antisense epigenetic cis-interactions and argues against a major role for Ube3a-ATS in the imprinting of Ube3a.
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Affiliation(s)
| | | | | | | | - Joseph Wagstaff
- Clinical Genetics Program, Carolinas Medical CenterCharlotte NC 28232-2861, USA
| | - Marc Lalande
- To whom correspondence should be addressed. Tel: +1 860 679 8349; Fax: +1 860 679 8345;
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26
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Brockmann GA, Karatayli E, Haley CS, Renne U, Rottmann OJ, Karle S. QTLs for pre- and postweaning body weight and body composition in selected mice. Mamm Genome 2005; 15:593-609. [PMID: 15457339 DOI: 10.1007/s00335-004-3026-4] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2003] [Accepted: 04/07/2004] [Indexed: 12/01/2022]
Abstract
In an intercross between the high-body-weight-selected mouse line NMRI8 and the inbred line DBA/2, we analyzed genetic effects on growth during the suckling period and after weaning during the juvenile phase of development. QTL mapping results indicated that a switch of gene activation might occur at the age of three weeks when animals are weaned. We found QTLs for body weight with major effects at the age of two and three weeks when animals are fed by their mothers, and QTLs with highest effects after weaning when animals have to live on their own under ad libitum access to food. Specific epistatic effects on body weight at two and three weeks and epistatic interaction influencing growth after weaning support this finding. QTL effects explained the greatest variance during puberty when animals grow fastest and become fertile. In the present study, all except one QTL effect for early body weight had dominance variance components. These might result from direct single-locus-dominant allelic expression, but also from the identified epistatic interaction between different QTLs that we have found for body weight at all ages. Beside body weight, body composition traits (muscle weight, reproductive fat weight, weight of inner organs) were analyzed. Sex-dimorphic QTLs were found for body weight and fat deposition. The identified early-growth QTLs could be the target of epigenetic modifications which might influence body weight at later ages.
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Affiliation(s)
- Gudrun A Brockmann
- Research Institute for the Biology of Farm Animals, 18196, Dummerstorf, Germany.
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27
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Abstract
Although obesity shows high heritability, we are aware of only a small number of genes that affect adipose mass in humans. Genetic syndromes with obesity represent unique opportunities to gain insight into the control of energy balance. The majority of obesity syndromes can be distinguished by the presence of mental retardation. We performed a systematic search of such syndromes and reviewed the literature with a focus on distinguishing clinical features, the characteristics of their obesity, and the underlying pathogenetic mechanisms. We predict that the study of these conditions will shed light on common forms of obesity.
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Affiliation(s)
- M-A Delrue
- Division of Medical Genetics, Hôpital Sainte-Justine, Montréal, Québec, Canada
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28
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Wang Y, Jones Voy B, Urs S, Kim S, Soltani-Bejnood M, Quigley N, Heo YR, Standridge M, Andersen B, Dhar M, Joshi R, Wortman P, Taylor JW, Chun J, Leuze M, Claycombe K, Saxton AM, Moustaid-Moussa N. The human fatty acid synthase gene and de novo lipogenesis are coordinately regulated in human adipose tissue. J Nutr 2004; 134:1032-8. [PMID: 15113941 DOI: 10.1093/jn/134.5.1032] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Despite its potential importance in obesity and related disorders, little is known about regulation of lipogenesis in human adipose tissue. To investigate this area at the molecular and mechanistic levels, we studied lipogenesis and the regulation of 1 of its core enzymes, fatty acid synthase (FAS), in human adipose tissue in response to hormonal and nutritional manipulation. As a paradigm for lipogenic genes, we cloned the upstream region of the human FAS gene, compared its sequence to that of FAS orthologs from other species, and identified important regulatory elements that lie upstream of the FAS coding region. Lipogenesis, as assessed by glucose incorporation into lipids, was increased by insulin and more so by the combination of insulin and dexamethasone (Dex, a potent glucocorticoid analogue). In parallel, FAS expression, activity, and gene transcription rate were also significantly increased by these treatments. We also showed that linoleic acid, a representative PUFA, attenuated the actions of insulin and Dex on fatty acid and lipid synthesis as well as FAS activity and expression. Using reporter assays, we determined that the regions responsible for hormonal regulation of the FAS gene lie in the proximal portion of the gene's 5'-flanking region, within which we identified an insulin response element similar to the E-box sequence we identified previously in the rat FAS gene. In summary, we demonstrated that lipogenesis occurs in human adipose tissue and can be induced by insulin, further enhanced by glucocorticoids, and suppressed by PUFA in a hormone-dependent manner.
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Affiliation(s)
- Yanxin Wang
- Department of Nutrition and Agricultural Experiment Station, University of Tennessee, Knoxville, TN 37996-1920,USA
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29
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Stefan M, Nicholls RD. What have rare genetic syndromes taught us about the pathophysiology of the common forms of obesity? Curr Diab Rep 2004; 4:143-50. [PMID: 15035975 DOI: 10.1007/s11892-004-0070-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Obesity is a central feature for several congenital syndromes, including Prader-Willi, Angelman, Bardet-Biedl, Cohen, Alström, and Börjeson-Forssman-Lehmann syndromes, and Albright's hereditary osteodystrophy. Although a role for the central nervous system, including the hypothalamus-pituitary axis, has been suggested for the etiology of obesity in these syndromes, the pathophysiologic pathways are as yet not well defined, and in many cases may identify currently unknown mechanisms. Nevertheless, many of the causative genes and unusual mechanisms, including parental imprinting of genes and complex patterns of inheritance, have been identified. We review the latest advances in understanding congenital syndromes in which obesity is purely genetic, drawing on comparisons to genetic studies of obesity in the human population as well as to those in experimental and agricultural animal models. An understanding of the genetic basis for these syndromes will provide a more comprehensive picture of the mechanisms that control food intake and energy balance in humans.
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Affiliation(s)
- Mihaela Stefan
- Department of Psychiatry, University of Pennsylvania, Clinical Research Building, Room 528, 415 Curie Boulevard, Philadelphia, PA 19104-6140, USA
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30
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Dhar MS, Sommardahl CS, Kirkland T, Nelson S, Donnell R, Johnson DK, Castellani LW. Mice heterozygous for Atp10c, a putative amphipath, represent a novel model of obesity and type 2 diabetes. J Nutr 2004; 134:799-805. [PMID: 15051828 DOI: 10.1093/jn/134.4.799] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Atp10c is a novel type IV P-type ATPase and is a putative phospholipid transporter. The purpose of this study was to assess the overall effect of the heterozygous deletion of Atp10c on obesity-related phenotypes and metabolic abnormalities in mice fed a high-fat diet. Heterozygous mice with maternal inheritance of Atp10c were compared with heterozygous mice with paternal inheritance of Atp10c and wild-type controls. Body weight, adiposity index, and plasma insulin, leptin and triglyceride concentrations were significantly greater in the mutants inheriting the deletion maternally compared with their sex- and age-matched control male mice fed a 10% fat (% energy) diet and female mice fed a 45% fat (% energy) diet. Glucose and insulin tolerance tests were performed after mice consumed the diets for 4 and 8 wk. Mutants had altered glucose tolerance and insulin response compared with controls, suggesting insulin resistance in both sexes. Mice were killed at 12 wk and routine gross and histological evaluations of the liver, pancreas, adipose tissue, and heart were performed. Histological evaluation showed micro- and macrovesicular lipid deposition within the hepatocytes that was more severe in the mutant mice than in age-matched controls. Although sex differences were observed, our data suggest that heterozygous deletion along with an unusual pattern of maternal inheritance of the chromosomal region containing the single gene, Atp10c, causes obesity, type 2 diabetes, and nonalcoholic fatty liver disease in these mice.
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Affiliation(s)
- Madhu S Dhar
- Department of Nutrition, University of Tennessee, Knoxville, TN 37996, USA.
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Johnson DK. Phenotype- and gene-driven approaches to discovering the functions of mammalian genes. J Nutr 2003; 133:4269-70. [PMID: 14652386 DOI: 10.1093/jn/133.12.4269] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
All of us are involved in discovery science as we pursue the genes, networks, cellular processes and biophysical principles that govern our chosen biological question. For those of us who choose to proceed using plant or animal models to dissect the elements of our favorite biological system, there are many classical and newer approaches available for our use, including two complementary strategies by which the discovery process is proceeding at the Oak Ridge National Laboratory (ORNL). The ORNL has been known for six decades for its investigations of the effects of radiation and chemicals in inducing heritable mutations in mouse germ cells, and for using mouse mutations as tools for the cloning and characterization of mammalian genes. Our history and experience in making mouse models are being applied via these two complementary strategies: 1), a phenotype-driven approach, in which mice carrying random chemically-induced mutations are screened for abnormal phenotypes; and 2) a gene-driven approach in which heritable single nucleotide polymorphisms (SNP) in preselected genes already thought likely to influence a biological system of choice can be recovered in live mice. The SNP-carrying mice can then be phenotyped for alterations in one's target biology. Both approaches have value and are necessary; while we can use mutations in genes that we already know to be of interest in our favorite biology to discover gene function, we also know that biology is full of surprise genes whose effects on our favorite biology would not be predicted and which will be identified only through phenotype screening.
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Affiliation(s)
- Dabney K Johnson
- Life Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6420, USA.
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Kashiwagi A, Meguro M, Hoshiya H, Haruta M, Ishino F, Shibahara T, Oshimura M. Predominant maternal expression of the mouse Atp10c in hippocampus and olfactory bulb. J Hum Genet 2003; 48:194-8. [PMID: 12730723 DOI: 10.1007/s10038-003-0009-3] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2002] [Accepted: 02/09/2003] [Indexed: 10/26/2022]
Abstract
The human chromosome 15q11-q13 region is one of the most intriguing imprinted domains, and the abnormalities inherited are associated with neurological disorders including Prader-Willi syndrome (PWS), Angelman syndrome (AS) and autism. Recently we have identified a novel maternally expressed gene, ATP10C, that encodes a putative aminophospholipid translocase within this critical region, 200 kb distal to UBE3A in an imprinted domain on human chromosome 15. ATP10C, with UBE3A, displayed tissue-specific imprinting with predominant expression of the maternal allele in the brain. In this study, we demonstrated that the mouse homologue, Atp10c/pfatp, showed tissue-specific maternal expression in the hippocampus and olfactory bulb, which overlapped the region of imprinted Ube3a expression. These data suggest that the imprinted transcript of Atp10c in the specific region of CNS may be associated with neurological disorders including AS and autism.
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Affiliation(s)
- Akiko Kashiwagi
- Division of Molecular and Cell Genetics, Department of Molecular and Cellular Biology, School of Life Sciences, Faculty of Medicine, Tottori University, 86 Nishimachi, Yonago 683-8503, Japan
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Hua Z, Graham TR. Requirement for neo1p in retrograde transport from the Golgi complex to the endoplasmic reticulum. Mol Biol Cell 2003; 14:4971-83. [PMID: 12960419 PMCID: PMC284799 DOI: 10.1091/mbc.e03-07-0463] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Neo1p from Saccharomyces cerevisiae is an essential P-type ATPase and potential aminophospholipid translocase (flippase) in the Drs2p family. We have previously implicated Drs2p in protein transport steps in the late secretory pathway requiring ADP-ribosylation factor (ARF) and clathrin. Here, we present evidence that epitope-tagged Neo1p localizes to the endoplasmic reticulum (ER) and Golgi complex and is required for a retrograde transport pathway between these organelles. Using conditional alleles of NEO1, we find that loss of Neo1p function causes cargo-specific defects in anterograde protein transport early in the secretory pathway and perturbs glycosylation in the Golgi complex. Rer1-GFP, a protein that cycles between the ER and Golgi complex in COPI and COPII vesicles, is mislocalized to the vacuole in neo1-ts at the nonpermissive temperature. These phenotypes suggest that the anterograde protein transport defect is a secondary consequence of a defect in a COPI-dependent retrograde pathway. We propose that loss of lipid asymmetry in the cis Golgi perturbs retrograde protein transport to the ER.
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Affiliation(s)
- Zhaolin Hua
- Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee 37235-1634, USA
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Chai JH, Locke DP, Greally JM, Knoll JHM, Ohta T, Dunai J, Yavor A, Eichler EE, Nicholls RD. Identification of four highly conserved genes between breakpoint hotspots BP1 and BP2 of the Prader-Willi/Angelman syndromes deletion region that have undergone evolutionary transposition mediated by flanking duplicons. Am J Hum Genet 2003; 73:898-925. [PMID: 14508708 PMCID: PMC1180611 DOI: 10.1086/378816] [Citation(s) in RCA: 161] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2003] [Accepted: 08/01/2003] [Indexed: 01/21/2023] Open
Abstract
Prader-Willi and Angelman syndromes (PWS and AS) typically result from an approximately 4-Mb deletion of human chromosome 15q11-q13, with clustered breakpoints (BP) at either of two proximal sites (BP1 and BP2) and one distal site (BP3). HERC2 and other duplicons map to these BP regions, with the 2-Mb PWS/AS imprinted domain just distal of BP2. Previously, the presence of genes and their imprinted status have not been examined between BP1 and BP2. Here, we identify two known (CYFIP1 and GCP5) and two novel (NIPA1 and NIPA2) genes in this region in human and their orthologs in mouse chromosome 7C. These genes are expressed from a broad range of tissues and are nonimprinted, as they are expressed in cells derived from normal individuals, patients with PWS or AS, and the corresponding mouse models. However, replication-timing studies in the mouse reveal that they are located in a genomic domain showing asynchronous replication, a feature typically ascribed to monoallelically expressed loci. The novel genes NIPA1 and NIPA2 each encode putative polypeptides with nine transmembrane domains, suggesting function as receptors or as transporters. Phylogenetic analyses show that NIPA1 and NIPA2 are highly conserved in vertebrate species, with ancestral members in invertebrates and plants. Intriguingly, evolutionary studies show conservation of the four-gene cassette between BP1 and BP2 in human, including NIPA1/2, CYFIP1, and GCP5, and proximity to the Herc2 gene in both mouse and Fugu. These observations support a model in which duplications of the HERC2 gene at BP3 in primates first flanked the four-gene cassette, with subsequent transposition of these four unique genes by a HERC2 duplicon-mediated process to form the BP1-BP2 region. Duplicons therefore appear to mediate genomic fluidity in both disease and evolutionary processes.
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Affiliation(s)
- J-H Chai
- Center for Neurobiology and Behavior, Department of Psychiatry, University of Pennsylvania, Philadelphia, PA, 19104, USA
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Kayashima T, Yamasaki K, Joh K, Yamada T, Ohta T, Yoshiura KI, Matsumoto N, Nakane Y, Mukai T, Niikawa N, Kishino T. Atp10a, the mouse ortholog of the human imprinted ATP10A gene, escapes genomic imprinting. Genomics 2003; 81:644-7. [PMID: 12782135 DOI: 10.1016/s0888-7543(03)00077-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The mouse Atp10a gene is located at the border of an imprinted domain distal to the p-locus on mouse chromosome 7. The localization of Atp10a neighboring the maternally expressed gene Ube3a in the imprinted domain and an unusual inheritance pattern of the obesity phenotype with a p-locus deletion have suggested that Atp10a might be imprinted and associated with body fat. Recently, its human ortholog, ATP10A, was identified as the second imprinted gene with maternal expression in the human chromosome 15q11-q13 imprinted domain. To elucidate the imprinting status of Atp10a, we performed expression analysis in various tissues from reciprocal crosses between C57BL/6 and PWK (divergent strains of Mus musculus) mice. The results revealed that Atp10a was biallelically expressed in all tissues examined. Furthermore, there was no differential methylation in the CpG island and no antisense transcripts of the gene. These findings suggest that the mouse Atp10a gene escapes genomic imprinting.
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Affiliation(s)
- Tomohiko Kayashima
- Department of Human Genetics, Nagasaki University, School of Medicine, Nagasaki 852-8523, Japan
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Abstract
Lipids in biological membranes are asymmetrically distributed across the bilayer; the amine-containing phospholipids are enriched on the cytoplasmic surface of the plasma membrane, while the choline-containing and sphingolipids are enriched on the outer surface. The maintenance of transbilayer lipid asymmetry is essential for normal membrane function, and disruption of this asymmetry is associated with cell activation or pathologic conditions. Lipid asymmetry is generated primarily by selective synthesis of lipids on one side of the membrane. Because passive lipid transbilayer diffusion is slow, a number of proteins have evolved to either dissipate or maintain this lipid gradient. These proteins fall into three classes: 1) cytofacially-directed, ATP-dependent transporters ("flippases"); 2) exofacially-directed, ATP-dependent transporters ("floppases"); and 3) bidirectional, ATP-independent transporters ("scramblases"). The flippase is highly selective for phosphatidylserine and functions to keep this lipid sequestered from the cell surface. Floppase activity has been associated with the ABC class of transmembrane transporters. Although they are primarily nonspecific, at least two members of this class display selectivity for their substrate lipid. Scramblases are inherently nonspecific and function to randomize the distribution of newly synthesized lipids in the endoplasmic reticulum or plasma membrane lipids in activated cells. It is the combined action of these proteins and the physical properties of the membrane bilayer that generate and maintain transbilayer lipid asymmetry.
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Affiliation(s)
- David L Daleke
- Medical Sciences Program, Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Bloomington, IN 47405, USA.
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Williamson P, Schlegel RA. Transbilayer phospholipid movement and the clearance of apoptotic cells. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1585:53-63. [PMID: 12531537 DOI: 10.1016/s1388-1981(02)00324-4] [Citation(s) in RCA: 145] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
When lymphocytes (and other cells) die by apoptosis, they orchestrate their own orderly removal by macrophages, and thereby prevent the inflammation that would otherwise attend cell lysis. As part of their demise, apoptotic cells disrupt the normal asymmetric distribution of phospholipids across their plasma membranes, an asymmetry normally maintained by an aminophospholipid translocase. This disruption of asymmetry, mediated by an activity known as the scramblase, generates ligands on the cell surface that trigger phagocytosis of the dying cell before lysis can occur. This crucial alteration of the plasma membrane is not dependent on caspase-mediated proteolysis, but quite unexpectedly, it is required both on the apoptotic target cell and on the phagocyte that engulfs it. At least in the phagocyte, this rearrangement may depend on the activity of an ABC ATPase, termed ABC1 in mammals and ced-7 in C. elegans.
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38
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Hua Z, Fatheddin P, Graham TR. An essential subfamily of Drs2p-related P-type ATPases is required for protein trafficking between Golgi complex and endosomal/vacuolar system. Mol Biol Cell 2002; 13:3162-77. [PMID: 12221123 PMCID: PMC124150 DOI: 10.1091/mbc.e02-03-0172] [Citation(s) in RCA: 192] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2002] [Revised: 05/23/2002] [Accepted: 06/05/2002] [Indexed: 01/06/2023] Open
Abstract
The Saccharomyces cerevisiae genome contains five genes encoding P-type ATPases that are potential aminophospholipid translocases (APTs): DRS2, NEO1, and three uncharacterized open reading frames that we have named DNF1, DNF2, and DNF3 for DRS2/NEO1 family. NEO1 is the only essential gene in APT family and seems to be functionally distinct from the DRS2/DNF genes. The drs2Delta dnf1Delta dnf2Delta dnf3Delta quadruple mutant is inviable, although any one member of this group can maintain viability, indicating that there is a substantial functional overlap between the encoded proteins. We have previously implicated Drs2p in clathrin function at the trans-Golgi network. In this study, we constructed strains carrying all possible viable combinations of null alleles from this group and analyzed them for defects in protein transport. The drs2Delta dnf1Delta mutant grows slowly, massively accumulates intracellular membranes, and exhibits a substantial defect in the transport of alkaline phosphatase to the vacuole. Transport of carboxypeptidase Y to the vacuole is also perturbed, but to a lesser extent. In addition, the dnf1Delta dnf2Delta dnf3Delta mutant exhibits a defect in recycling of GFP-Snc1p in the early endocytic-late secretory pathways. Drs2p and Dnf3p colocalize with the trans-Golgi network marker Kex2p, whereas Dnf1p and Dnf2p seem to localize to the plasma membrane and late exocytic or early endocytic membranes. We propose that eukaryotes express multiple APT subfamily members to facilitate protein transport in multiple pathways.
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Affiliation(s)
- Zhaolin Hua
- Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee 37235-1634, USA
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39
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Dhar M, Hauser L, Johnson D. An aminophospholipid translocase associated with body fat and type 2 diabetes phenotypes. OBESITY RESEARCH 2002; 10:695-702. [PMID: 12105293 DOI: 10.1038/oby.2002.94] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
OBJECTIVE We have shown that a region on proximal mouse chromosome 7, near the pink-eyed (p) dilution locus, contains an ATPase (pfatp), a putative aminophospholipid translocase. Studies have suggested that this gene is a prime candidate for modulating body fat or involved in lipid metabolism in mouse and humans. Toward further analyses, our objective was to generate the complete genomic structures of mouse and human genes. RESEARCH METHODS AND PROCEDURES The genomic structure of mouse pfatp was deduced by comparing the full-length cDNA sequence with the genomic sequence derived from a mouse BAC. The human ortholog was identified from the National Center for Biotechnology Information database. Full-length cDNA was generated, and the corresponding genomic structure was deduced from the Human Genome Database. RESULTS Murine pfatp, and its human ortholog, PFATP, belong to class V of the third subfamily of P-type ATPases. The gene organization is strikingly similar in both organisms and all exon-intron junctions are conserved. A putative promoter region of PFATP contains a strong CpG island. The 5' untranslated regions of the two cDNAs have potential binding sites for multiple transcription factors, including Sp1, USF, AP1, and AP2, involved in adipogenesis and adipocyte metabolism. DISCUSSION We report the generation of the complete genomic structure of a novel aminophospholipid translocase in mice and humans. Because the exact biological role and the subsequent relevance of these ATPases to obesity and diabetes are unknown, these data help to delineate the role of these genes in lipid/adipocyte metabolism.
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Affiliation(s)
- Madhu Dhar
- The University of Tennessee Graduate School of Genome Science and Technology, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
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40
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Abstract
P-type ATPases are a venerable family of ATP-dependent ion transporters. Recently, evidence was presented that a rabbit gene in the type IV subfamily of P-type ATPases was missing a transmembrane helix (transmembrane domain 4) thought to be critical for ion transport, a deletion that would place the two major catalytic loops of the enzyme on opposite sides of the membrane. It was proposed that the resulting protein was a RING finger-binding protein that targets transcription factors to specific domains within the nucleus. From analysis of human genomic sequence data, it is shown here that the region containing transmembrane domain 4, corresponding to exon 12, is present in the human homolog of the gene, ATP11B. PCR analysis indicates that the predominant Atp11b transcripts in a rabbit cDNA library and in a mouse cDNA library also contain exon 12. The results suggest that the transcript proposed to encode the RING finger-binding protein is a minor rabbit-specific splice variant. The ATP11B gene thus may not encode a protein with a function radically different from that of other P-type ATPase transporters.
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Affiliation(s)
- Margaret S Halleck
- Department of Biochemistry and Molecular Biology, Penn State University, University Park, Pennsylvania 16802, USA
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41
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Nicholls RD, Knepper JL. Genome organization, function, and imprinting in Prader-Willi and Angelman syndromes. Annu Rev Genomics Hum Genet 2002; 2:153-75. [PMID: 11701647 DOI: 10.1146/annurev.genom.2.1.153] [Citation(s) in RCA: 405] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The chromosomal region, 15q11-q13, involved in Prader-Willi and Angelman syndromes (PWS and AS) represents a paradigm for understanding the relationships between genome structure, epigenetics, evolution, and function. The PWS/AS region is conserved in organization and function with the homologous mouse chromosome 7C region. However, the primate 4 Mb PWS/AS region is bounded by duplicons derived from an ancestral HERC2 gene and other sequences that may predispose to chromosome rearrangements. Within a 2 Mb imprinted domain, gene function depends on parental origin. Genetic evidence suggests that PWS arises from functional loss of several paternally expressed genes, including those that function as RNAs, and that AS results from loss of maternal UBE3A brain-specific expression. Imprinted expression is coordinately controlled in cis by an imprinting center (IC), a genetic element functional in germline and/or early postzygotic development that regulates the establishment of parental specific allelic differences in replication timing, DNA methylation, and chromatin structure.
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Affiliation(s)
- R D Nicholls
- Center for Neurobiology and Behavior, Department of Psychiatry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6140, USA.
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42
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Lossie AC, Whitney MM, Amidon D, Dong HJ, Chen P, Theriaque D, Hutson A, Nicholls RD, Zori RT, Williams CA, Driscoll DJ. Distinct phenotypes distinguish the molecular classes of Angelman syndrome. J Med Genet 2001; 38:834-45. [PMID: 11748306 PMCID: PMC1734773 DOI: 10.1136/jmg.38.12.834] [Citation(s) in RCA: 237] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
BACKGROUND Angelman syndrome (AS) is a severe neurobehavioural disorder caused by defects in the maternally derived imprinted domain located on 15q11-q13. Most patients acquire AS by one of five mechanisms: (1) a large interstitial deletion of 15q11-q13; (2) paternal uniparental disomy (UPD) of chromosome 15; (3) an imprinting defect (ID); (4) a mutation in the E3 ubiquitin protein ligase gene (UBE3A); or (5) unidentified mechanism(s). All classical patients from these classes exhibit four cardinal features, including severe developmental delay and/or mental retardation, profound speech impairment, a movement and balance disorder, and AS specific behaviour typified by an easily excitable personality with an inappropriately happy affect. In addition, patients can display other characteristics, including microcephaly, hypopigmentation, and seizures. METHODS We restricted the present study to 104 patients (93 families) with a classical AS phenotype. All of our patients were evaluated for 22 clinical variables including growth parameters, acquisition of motor skills, and history of seizures. In addition, molecular and cytogenetic analyses were used to assign a molecular class (I-V) to each patient for genotype-phenotype correlations. RESULTS In our patient repository, 22% of our families had normal DNA methylation analyses along 15q11-q13. Of these, 44% of sporadic patients had mutations within UBE3A, the largest percentage found to date. Our data indicate that the five molecular classes can be divided into four phenotypic groups: deletions, UPD and ID patients, UBE3A mutation patients, and subjects with unknown aetiology. Deletion patients are the most severely affected, while UPD and ID patients are the least. Differences in body mass index, head circumference, and seizure activity are the most pronounced among the classes. CONCLUSIONS Clinically, we were unable to distinguish between UPD and ID patients, suggesting that 15q11-q13 contains the only significant maternally expressed imprinted genes on chromosome 15.
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Affiliation(s)
- A C Lossie
- R C Philips Unit and Division of Genetics, Department of Pediatrics, University of Florida, Gainesville, FL 32610-0296, USA
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43
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Abstract
In this paper we describe various study designs and analytic techniques for testing the joint hypothesis that a genetic marker is both linked to and associated with a quantitative phenotype. Issues of power and sampling are addressed. The distinction between methods that explicitly examine association and those that infer association by examining the distribution of allelic transmissions from a heterozygous parent is examined. Extensions to multivariate, multiallelic, and multilocus situations are addressed. Recent approaches that combine variance-components-based linkage analyses with joint tests of linkage in the presence of association for disentanglement of the linkage and association and the application of such methods to fine mapping are discussed. Finally, new classes of joint tests of linkage and association that do not require samples of related individuals are described.
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Affiliation(s)
- D B Allison
- Department of Biostatistics Section on Statistical Genetics & Clinical Nutrition Research Center, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA
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44
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Nurmi EL, Bradford Y, Chen Y, Hall J, Arnone B, Gardiner MB, Hutcheson HB, Gilbert JR, Pericak-Vance MA, Copeland-Yates SA, Michaelis RC, Wassink TH, Santangelo SL, Sheffield VC, Piven J, Folstein SE, Haines JL, Sutcliffe JS. Linkage disequilibrium at the Angelman syndrome gene UBE3A in autism families. Genomics 2001; 77:105-13. [PMID: 11543639 DOI: 10.1006/geno.2001.6617] [Citation(s) in RCA: 110] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Autistic disorder is a neurodevelopmental disorder with a complex genetic etiology. Observations of maternal duplications affecting chromosome 15q11-q13 in patients with autism and evidence for linkage and linkage disequilibrium to markers in this region in chromosomally normal autism families indicate the existence of a susceptibility locus. We have screened the families of the Collaborative Linkage Study of Autism for several markers spanning a candidate region covering approximately 2 Mb and including the Angelman syndrome gene (UBE3A) and a cluster of gamma-aminobutyric acid (GABA(A)) receptor subunit genes (GABRB3, GABRA5, and GABRG3). We found significant evidence for linkage disequilibrium at marker D15S122, located at the 5' end of UBE3A. This is the first report, to our knowledge, of linkage disequilibrium at UBE3A in autism families. Characterization of null alleles detected at D15S822 in the course of genetic studies of this region showed a small (approximately 5-kb) genomic deletion, which was present at somewhat higher frequencies in autism families than in controls.
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Affiliation(s)
- E L Nurmi
- Program in Human Genetics, Department of Molecular Physiology & Biophysics, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA
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Herzing LBK, Kim SJ, Cook, Jr. EH, Ledbetter DH. The human aminophospholipid-transporting ATPase gene ATP10C maps adjacent to UBE3A and exhibits similar imprinted expression. Am J Hum Genet 2001; 68:1501-5. [PMID: 11353404 PMCID: PMC1226137 DOI: 10.1086/320616] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2001] [Accepted: 04/12/2001] [Indexed: 11/03/2022] Open
Abstract
Maternal duplications of the imprinted 15q11-13 domain result in an estimated 1%-2% of autism-spectrum disorders, and linkage to autism has been identified within 15q12-13. UBE3A, the Angelman syndrome gene, has, to date, been the only maternally expressed, imprinted gene identified within this region, but mutations have not been found in autistic patients. Here we describe the characterization of ATP10C, a new human imprinted gene, which encodes a putative protein homologous to the mouse aminophospholipid-transporting ATPase Atp10c. ATP10C maps within 200 kb distal to UBE3A and, like UBE3A, also demonstrates imprinted, preferential maternal expression in human brain. The location and imprinted expression of ATP10C thus make it a candidate for chromosome 15-associated autism and suggest that it may contribute to the Angelman syndrome phenotype.
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Affiliation(s)
- Laura B. K. Herzing
- Departments of Human Genetics, Psychiatry, Laboratory of Developmental Neuroscience, and Pediatrics, University of Chicago, Chicago
| | - Soo-Jeong Kim
- Departments of Human Genetics, Psychiatry, Laboratory of Developmental Neuroscience, and Pediatrics, University of Chicago, Chicago
| | - Edwin H. Cook, Jr.
- Departments of Human Genetics, Psychiatry, Laboratory of Developmental Neuroscience, and Pediatrics, University of Chicago, Chicago
| | - David H. Ledbetter
- Departments of Human Genetics, Psychiatry, Laboratory of Developmental Neuroscience, and Pediatrics, University of Chicago, Chicago
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46
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Meguro M, Kashiwagi A, Mitsuya K, Nakao M, Kondo I, Saitoh S, Oshimura M. A novel maternally expressed gene, ATP10C, encodes a putative aminophospholipid translocase associated with Angelman syndrome. Nat Genet 2001; 28:19-20. [PMID: 11326269 DOI: 10.1038/ng0501-19] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Lack of a maternal contribution to the genome at the imprinted domain on proximal chromosome 15 causes Angelman syndrome (AS) associated with neurobehavioral anomalies that include severe mental retardation, ataxia and epilepsy. Although AS patients have infrequent mutations in the gene encoding an E6-AP ubiquitin ligase required for long-term synaptic potentiation (LTP), most cases are attributed to de novo maternal deletions of 15q11-q13. We report here that a novel maternally expressed gene, ATP10C, maps within the most common interval of deletion and that ATP10C expression is virtually absent from AS patients with imprinting mutations, as well as from patients with maternal deletions of 15q11-q13.
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Affiliation(s)
- M Meguro
- Core Research for Evolutional Science and Technology project, Department of Molecular and Cell Genetics, School of Life Sciences, Faculty of Medicine, Tottori University, Tottori, Japan
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