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Mulugeta A, Lumsden AL, Madakkatel I, Stacey D, Lee SH, Mäenpää J, Oehler MK, Hyppönen E. Phenome-wide association study of ovarian cancer identifies common comorbidities and reveals shared genetics with complex diseases and biomarkers. Cancer Med 2024; 13:e7051. [PMID: 38457211 PMCID: PMC10923028 DOI: 10.1002/cam4.7051] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2023] [Revised: 01/29/2024] [Accepted: 02/09/2024] [Indexed: 03/09/2024] Open
Abstract
BACKGROUND Ovarian cancer (OC) is commonly diagnosed among older women who have comorbidities. This hypothesis-free phenome-wide association study (PheWAS) aimed to identify comorbidities associated with OC, as well as traits that share a genetic architecture with OC. METHODS We used data from 181,203 white British female UK Biobank participants and analysed OC and OC subtype-specific genetic risk scores (OC-GRS) for an association with 889 diseases and 43 other traits. We conducted PheWAS and colocalization analyses for individual variants to identify evidence for shared genetic architecture. RESULTS The OC-GRS was associated with 10 diseases, and the clear cell OC-GRS was associated with five diseases at the FDR threshold (p = 5.6 × 10-4 ). Mendelian randomizaiton analysis (MR) provided robust evidence for the association of OC with higher risk of "secondary malignant neoplasm of digestive systems" (OR 1.64, 95% CI 1.33, 2.02), "ascites" (1.48, 95% CI 1.17, 1.86), "chronic airway obstruction" (1.17, 95% CI 1.07, 1.29), and "abnormal findings on examination of the lung" (1.51, 95% CI 1.22, 1.87). Analyses of lung spirometry measures provided further support for compromised respiratory function. PheWAS on individual OC variants identified five genetic variants associated with other diseases, and seven variants associated with biomarkers (all, p ≤ 4.5 × 10-8 ). Colocalization analysis identified rs4449583 (from TERT locus) as the shared causal variant for OC and seborrheic keratosis. CONCLUSIONS OC is associated with digestive and respiratory comorbidities. Several variants affecting OC risk were associated with other diseases and biomarkers, with this study identifying a novel genetic locus shared between OC and skin conditions.
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Affiliation(s)
- Anwar Mulugeta
- Australian Centre for Precision Health, Unit of Clinical and Health SciencesUniversity of South AustraliaAdelaideSouth AustraliaAustralia
- South Australian Health and Medical Research InstituteAdelaideSouth AustraliaAustralia
- Department of Pharmacology and Clinical Pharmacy, College of Health ScienceAddis Ababa UniversityAddis AbabaEthiopia
| | - Amanda L. Lumsden
- Australian Centre for Precision Health, Unit of Clinical and Health SciencesUniversity of South AustraliaAdelaideSouth AustraliaAustralia
- South Australian Health and Medical Research InstituteAdelaideSouth AustraliaAustralia
| | - Iqbal Madakkatel
- Australian Centre for Precision Health, Unit of Clinical and Health SciencesUniversity of South AustraliaAdelaideSouth AustraliaAustralia
- South Australian Health and Medical Research InstituteAdelaideSouth AustraliaAustralia
| | - David Stacey
- Australian Centre for Precision Health, Unit of Clinical and Health SciencesUniversity of South AustraliaAdelaideSouth AustraliaAustralia
- South Australian Health and Medical Research InstituteAdelaideSouth AustraliaAustralia
| | - S. Hong Lee
- Australian Centre for Precision Health, Unit of Clinical and Health SciencesUniversity of South AustraliaAdelaideSouth AustraliaAustralia
- South Australian Health and Medical Research InstituteAdelaideSouth AustraliaAustralia
- UniSA Allied Health & Human PerformanceUniversity of South AustraliaAdelaideSouth AustraliaAustralia
| | - Johanna Mäenpää
- Faculty of Medicine and Medical TechnologyTampere UniversityTampereFinland
- Cancer Centre, Tampere University and University HospitalTampereFinland
| | - Martin K. Oehler
- Department of Gynaecological OncologyRoyal Adelaide HospitalAdelaideSouth AustraliaAustralia
- Adelaide Medical School, Robinson Research Institute, University of AdelaideAdelaideSouth AustraliaAustralia
| | - Elina Hyppönen
- Australian Centre for Precision Health, Unit of Clinical and Health SciencesUniversity of South AustraliaAdelaideSouth AustraliaAustralia
- South Australian Health and Medical Research InstituteAdelaideSouth AustraliaAustralia
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Jones LA, Sun EW, Lumsden AL, Thorpe DW, Peterson RA, De Fontgalland D, Sposato L, Rabbitt P, Hollington P, Wattchow DA, Keating DJ. Alterations in GLP-1 and PYY release with aging and body mass in the human gut. Mol Cell Endocrinol 2023; 578:112072. [PMID: 37739120 DOI: 10.1016/j.mce.2023.112072] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/24/2023] [Revised: 09/18/2023] [Accepted: 09/20/2023] [Indexed: 09/24/2023]
Abstract
The lining of our intestinal surface contains an array of hormone-producing cells that are collectively our bodies' largest endocrine cell reservoir. These "enteroendocrine" (EE) cells reside amongst the billions of absorptive epithelial and other cell types that line our gastrointestinal tract and can sense and respond to the ever-changing internal environment in our gut. EE cells release an array of important signalling molecules that can act as hormones, including glucagon-like peptide (GLP-1) and peptide YY (PYY) which are co-secreted from L cells. While much is known about the effects of these hormones on metabolism, insulin secretion and food intake, less is understood about their secretion from human intestinal tissue. In this study we assess whether GLP-1 and PYY release differs across human small and large intestinal tissue locations within the gastrointestinal tract, and/or by sex, body weight and the age of an individual. We identify that the release of both hormones is greater in more distal regions of the human colon, but is not different between sexes. We observe a negative correlation of GLP-1 and BMI in the small, but not large, intestine. Increased aging correlates with declining secretion of both GLP-1 and PYY in human large, but not small, intestine. When the data for large intestine is isolated by region, this relationship with age remains significant for GLP-1 in the ascending and descending colon and in the descending colon for PYY. This is the first demonstration that site-specific differences in GLP-1 and PYY release occur in human gut, as do site-specific relationships of L cell secretion with aging and body mass.
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Affiliation(s)
- Lauren A Jones
- Flinders Health and Medical Research Institute, College of Medicine and Public Health, Flinders University, Bedford Park, SA, 5042, Australia
| | - Emily W Sun
- Flinders Health and Medical Research Institute, College of Medicine and Public Health, Flinders University, Bedford Park, SA, 5042, Australia
| | - Amanda L Lumsden
- Australian Centre for Precision Health, Unit of Clinical and Health Sciences, University of South Australia, and South Australian Health and Medical Research Institute, Adelaide, SA, 5000, Australia
| | - Daniel W Thorpe
- Flinders Health and Medical Research Institute, College of Medicine and Public Health, Flinders University, Bedford Park, SA, 5042, Australia
| | - Rochelle A Peterson
- Flinders Health and Medical Research Institute, College of Medicine and Public Health, Flinders University, Bedford Park, SA, 5042, Australia
| | - Dayan De Fontgalland
- Department of Surgery, Flinders Medical Centre, Bedford Park, SA, 5042, Australia
| | - Luigi Sposato
- Department of Surgery, Flinders Medical Centre, Bedford Park, SA, 5042, Australia
| | - Philippa Rabbitt
- Department of Surgery, Flinders Medical Centre, Bedford Park, SA, 5042, Australia
| | - Paul Hollington
- Department of Surgery, Flinders Medical Centre, Bedford Park, SA, 5042, Australia
| | - David A Wattchow
- Department of Surgery, Flinders Medical Centre, Bedford Park, SA, 5042, Australia
| | - Damien J Keating
- Flinders Health and Medical Research Institute, College of Medicine and Public Health, Flinders University, Bedford Park, SA, 5042, Australia.
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Madakkatel I, Lumsden AL, Mulugeta A, Olver I, Hyppönen E. Hypothesis-free discovery of novel cancer predictors using machine learning. Eur J Clin Invest 2023; 53:e14037. [PMID: 37303098 DOI: 10.1111/eci.14037] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/29/2023] [Revised: 05/03/2023] [Accepted: 05/25/2023] [Indexed: 06/13/2023]
Abstract
BACKGROUND Cancer is a leading cause of morbidity and mortality worldwide, and better understanding of the risk factors could enhance prevention. METHODS We conducted a hypothesis-free analysis combining machine learning and statistical approaches to identify cancer risk factors from 2828 potential predictors captured at baseline. There were 459,169 UK Biobank participants free from cancer at baseline and 48,671 new cancer cases during the 10-year follow-up. Logistic regression models adjusted for age, sex, ethnicity, education, material deprivation, smoking, alcohol intake, body mass index and skin colour (as a proxy for sun sensitivity) were used for obtaining adjusted odds ratios, with continuous predictors presented using quintiles (Q). RESULTS In addition to smoking, older age and male sex, positively associating features included several anthropometric characteristics, whole body water mass, pulse, hypertension and biomarkers such as urinary microalbumin (Q5 vs. Q1 OR 1.16, 95% CI = 1.13-1.19), C-reactive protein (Q5 vs. Q1 OR 1.20, 95% CI = 1.16-1.24) and red blood cell distribution width (Q5 vs. Q1 OR 1.18, 95% CI = 1.14-1.21), among others. High-density lipoprotein cholesterol (Q5 vs. Q1 OR 0.84, 95% CI = 0.81-0.87) and albumin (Q5 vs. Q1 OR 0.84, 95% CI = 0.81-0.87) were inversely associated with cancer. In sex-stratified analyses, higher testosterone increased the risk in females but not in males (Q5 vs. Q1 ORfemales 1.23, 95% CI = 1.17-1.30). Phosphate was associated with a lower risk in females but a higher risk in males (Q5 vs. Q1 ORfemales 0.94, 95% CI = 0.90-0.99 vs. ORmales 1.09, 95% CI 1.04-1.15). CONCLUSIONS This hypothesis-free analysis suggests personal characteristics, metabolic biomarkers, physical measures and smoking as important predictors of cancer risk, with further studies needed to confirm causality and clinical relevance.
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Affiliation(s)
- Iqbal Madakkatel
- Australian Centre for Precision Health, Unit of Clinical and Health Sciences, University of South Australia, Adelaide, South Australia, Australia
- South Australian Health and Medical Research Institute, Adelaide, South Australia, Australia
| | - Amanda L Lumsden
- Australian Centre for Precision Health, Unit of Clinical and Health Sciences, University of South Australia, Adelaide, South Australia, Australia
- South Australian Health and Medical Research Institute, Adelaide, South Australia, Australia
| | - Anwar Mulugeta
- Australian Centre for Precision Health, Unit of Clinical and Health Sciences, University of South Australia, Adelaide, South Australia, Australia
- South Australian Health and Medical Research Institute, Adelaide, South Australia, Australia
- Department of Pharmacology and Clinical Pharmacy, College of Health Sciences, Addis Ababa, Ethiopia
| | - Ian Olver
- School of Psychology, Faculty of Health and Medical Sciences, University of Adelaide, Adelaide, South Australia, Australia
| | - Elina Hyppönen
- Australian Centre for Precision Health, Unit of Clinical and Health Sciences, University of South Australia, Adelaide, South Australia, Australia
- South Australian Health and Medical Research Institute, Adelaide, South Australia, Australia
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Lumsden AL, Mulugeta A, Hyppönen E. Milk consumption and risk of twelve cancers: A large-scale observational and Mendelian randomisation study. Clin Nutr 2023; 42:1-8. [PMID: 36473423 DOI: 10.1016/j.clnu.2022.11.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2022] [Revised: 11/01/2022] [Accepted: 11/04/2022] [Indexed: 11/11/2022]
Abstract
BACKGROUND & AIMS Milk consumption is a modifiable lifestyle factor that has been associated with several cancer types in observational studies. Limited evidence exists regarding the causality of these relationships. Using a genetic variant (rs4988235) near the lactase gene (LCT) locus that proxies milk consumption, we conducted a comprehensive survey to assess potential causal relationships between milk consumption and 12 types of cancer. METHODS Our analyses were conducted using white British participants of the UK Biobank (n = up to 255,196), the FinnGen cohort (up to 260,405), and available cancer consortia. We included cancers with previous evidence of an association with milk consumption in observational studies, as well as cancers common in both UK Biobank and FinnGen populations (>1000 cases). We evaluated phenotypic associations of milk intake and cancer incidence in the UK Biobank, and then used a Mendelian randomisation (MR) approach to assess causality in the UK Biobank, FinnGen consortium, and combined analyses incorporating additional consortia data for five cancers. In MR meta-analyses, case numbers for cancers of breast, ovary, uterus, cervix, prostate, bladder and urinary tract, colorectum, and lung ranged between 6000 and 148,000 cases, and between 780 and 1342 cases for cancers of the liver, mouth, stomach and diffuse large B-cell lymphoma. RESULTS In observational analyses, milk consumption was associated with higher risk of bladder and urinary tract cancer (OR 1.23, 95% CI 1.03-1.47), but not with any other cancer. This association was not confirmed in the MR analysis, and genetically predicted milk consumption showed a significant association only with lower risk of colorectal cancer (0.89, 0.81-0.98 per additional 50 g/day). In the MR analyses conducted among individual cohorts, genetically predicted milk consumption provided evidence for an association with lower colorectal cancer in the FinnGen cohort (0.85, 0.74-0.97), and in the UK Biobank greater risk of female breast cancer (1.12, 1.03-1.23), and uterine cancer in pre-menopausal females (3.98, 1.48-10.7). CONCLUSION In a comprehensive survey of milk-cancer associations, we confirm of a protective role of milk consumption for colorectal cancer. Our analyses also provide some suggestion for higher risks of breast cancer and premenopausal uterine cancer, warranting further investigation.
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Affiliation(s)
- Amanda L Lumsden
- Australian Centre for Precision Health, Unit of Clinical and Health Sciences, University of South Australia, Adelaide, SA 5000, Australia; South Australian Health and Medical Research Institute, Adelaide, SA 5000, Australia.
| | - Anwar Mulugeta
- Australian Centre for Precision Health, Unit of Clinical and Health Sciences, University of South Australia, Adelaide, SA 5000, Australia; South Australian Health and Medical Research Institute, Adelaide, SA 5000, Australia; Department of Pharmacology and Clinical Pharmacy, College of Health Sciences, Addis Ababa, Ethiopia.
| | - Elina Hyppönen
- Australian Centre for Precision Health, Unit of Clinical and Health Sciences, University of South Australia, Adelaide, SA 5000, Australia; South Australian Health and Medical Research Institute, Adelaide, SA 5000, Australia.
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Lumsden AL, Mulugeta A, Mäkinen V, Hyppönen E. Metabolic profile-based subgroups can identify differences in brain volumes and brain iron deposition. Diabetes Obes Metab 2023; 25:121-131. [PMID: 36053807 PMCID: PMC10946804 DOI: 10.1111/dom.14853] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/30/2022] [Revised: 08/16/2022] [Accepted: 08/28/2022] [Indexed: 12/14/2022]
Abstract
AIMS To evaluate associations of metabolic profiles and biomarkers with brain atrophy, lesions, and iron deposition to understand the early risk factors associated with dementia. MATERIALS AND METHODS Using data from 26 239 UK Biobank participants free from dementia and stroke, we assessed the associations of metabolic subgroups, derived using an artificial neural network approach (self-organizing map), and 39 individual biomarkers with brain MRI measures: total brain volume (TBV), grey matter volume (GMV), white matter volume (WMV), hippocampal volume (HV), white matter hyperintensity (WMH) volume, and caudate iron deposition. RESULTS In metabolic subgroup analyses, participants characterized by high triglycerides and liver enzymes showed the most adverse brain outcomes compared to the healthy reference subgroup with high-density lipoprotein cholesterol and low body mass index (BMI) including associations with GMV (βstandardized -0.20, 95% confidence interval [CI] -0.24 to -0.16), HV (βstandardized -0.09, 95% CI -0.13 to -0.04), WMH volume (βstandardized 0.22, 95% CI 0.18 to 0.26), and caudate iron deposition (βstandardized 0.30, 95% CI 0.25 to 0.34), with similar adverse associations for the subgroup with high BMI, C-reactive protein and cystatin C, and the subgroup with high blood pressure (BP) and apolipoprotein B. Among the biomarkers, striking associations were seen between basal metabolic rate (BMR) and caudate iron deposition (βstandardized 0.23, 95% CI 0.22 to 0.24 per 1 SD increase), GMV (βstandardized -0.15, 95% CI -0.16 to -0.14) and HV (βstandardized -0.11, 95% CI -0.12 to -0.10), and between BP and WMH volume (βstandardized 0.13, 95% CI 0.12 to 0.14 for diastolic BP). CONCLUSIONS Metabolic profiles were associated differentially with brain neuroimaging characteristics. Associations of BMR, BP and other individual biomarkers may provide insights into actionable mechanisms driving these brain associations.
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Affiliation(s)
- Amanda L. Lumsden
- Australian Centre for Precision Health, Unit of Clinical and Health SciencesUniversity of South AustraliaAdelaideAustralia
- South Australian Health and Medical Research InstituteAdelaideAustralia
| | - Anwar Mulugeta
- Australian Centre for Precision Health, Unit of Clinical and Health SciencesUniversity of South AustraliaAdelaideAustralia
- South Australian Health and Medical Research InstituteAdelaideAustralia
- Department of Pharmacology and Clinical PharmacyCollege of Health SciencesAddis AbabaEthiopia
| | - Ville‐Petteri Mäkinen
- South Australian Health and Medical Research InstituteAdelaideAustralia
- Computational Systems Biology Program, Precision Medicine ThemeSouth Australian Health and Medical Research InstituteAdelaideAustralia
| | - Elina Hyppönen
- Australian Centre for Precision Health, Unit of Clinical and Health SciencesUniversity of South AustraliaAdelaideAustralia
- South Australian Health and Medical Research InstituteAdelaideAustralia
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Mulugeta A, Navale SS, Lumsden AL, Llewellyn DJ, Hyppönen E. Healthy Lifestyle, Genetic Risk and Brain Health: A Gene-Environment Interaction Study in the UK Biobank. Nutrients 2022; 14:nu14193907. [PMID: 36235559 PMCID: PMC9570683 DOI: 10.3390/nu14193907] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2022] [Revised: 09/15/2022] [Accepted: 09/20/2022] [Indexed: 11/16/2022] Open
Abstract
Genetic susceptibility and lifestyle affect the risk of dementia but there is little direct evidence for their associations with preclinical changes in brain structure. We investigated the association of genetic dementia risk and healthy lifestyle with brain morphometry, and whether effects from elevated genetic risk are modified by lifestyle changes. We used prospective data from up to 25,894 UK Biobank participants (median follow-up of 8.8 years), and defined healthy lifestyle according to American Heart Association criteria as BMI < 30, no smoking, healthy diet and regular physical activity). Higher genetic risk was associated with lower hippocampal volume (beta −0.16 cm3, 95% CI −0.22, −0.11) and total brain volume (−4.34 cm3, 95% CI −7.68, −1.01) in participants aged ≥60 years but not <60 years. Healthy lifestyle was associated with higher total brain, grey matter and hippocampal volumes, and lower volume of white matter hyperintensities, with no effect modification by age or genetic risk. In conclusion, adverse effects of high genetic risk on brain health were only found in older participants, while adhering to healthy lifestyle recommendations is beneficial regardless of age or genetic risk.
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Affiliation(s)
- Anwar Mulugeta
- Australian Centre for Precision Health, Unit of Clinical and Health Sciences, University of South Australia, Adelaide, SA 5001, Australia
- South Australian Health and Medical Research Institute, Adelaide, SA 5000, Australia
- Department of Pharmacology and Clinical Pharmacy, College of Health Science, Addis Ababa University, Addis Ababa P.O. Box 9086, Ethiopia
| | - Shreeya S. Navale
- Australian Centre for Precision Health, Unit of Clinical and Health Sciences, University of South Australia, Adelaide, SA 5001, Australia
| | - Amanda L. Lumsden
- Australian Centre for Precision Health, Unit of Clinical and Health Sciences, University of South Australia, Adelaide, SA 5001, Australia
- South Australian Health and Medical Research Institute, Adelaide, SA 5000, Australia
| | - David J. Llewellyn
- College of Medicine and Health, University of Exeter, Devon EX1 2LU, UK
- Alan Turing Institute, London NW1 2DB, UK
| | - Elina Hyppönen
- Australian Centre for Precision Health, Unit of Clinical and Health Sciences, University of South Australia, Adelaide, SA 5001, Australia
- South Australian Health and Medical Research Institute, Adelaide, SA 5000, Australia
- Correspondence: ; Tel.: +61-(08)-83022518
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Sun EW, Iepsen EW, Pezos N, Lumsden AL, Martin AM, Schober G, Isaacs NJ, Rayner CK, Nguyen NQ, de Fontgalland D, Rabbitt P, Hollington P, Wattchow DA, Hansen T, Holm JC, Liou AP, Jackson VM, Torekov SS, Young RL, Keating DJ. A Gut-Intrinsic Melanocortin Signaling Complex Augments L-Cell Secretion in Humans. Gastroenterology 2021; 161:536-547.e2. [PMID: 33848536 DOI: 10.1053/j.gastro.2021.04.014] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/29/2020] [Revised: 04/04/2021] [Accepted: 04/06/2021] [Indexed: 12/23/2022]
Abstract
OBJECTIVE Hypothalamic melanocortin 4 receptors (MC4R) are a key regulator of energy homeostasis. Brain-penetrant MC4R agonists have failed, as concentrations required to suppress food intake also increase blood pressure. However, peripherally located MC4R may also mediate metabolic benefits of MC4R activation. Mc4r transcript is enriched in mouse enteroendocrine L cells and peripheral administration of the endogenous MC4R agonist, α-melanocyte stimulating hormone (α-MSH), triggers the release of the anorectic hormones Glucagon-like peptide-1 (GLP-1) and peptide tyrosine tyrosine (PYY) in mice. This study aimed to determine whether pathways linking MC4R and L-cell secretion exist in humans. DESIGN GLP-1 and PYY levels were assessed in body mass index-matched individuals with or without loss-of-function MC4R mutations following an oral glucose tolerance test. Immunohistochemistry was performed on human intestinal sections to characterize the mucosal MC4R system. Static incubations with MC4R agonists were carried out on human intestinal epithelia, GLP-1 and PYY contents of secretion supernatants were assayed. RESULTS Fasting PYY levels and oral glucose-induced GLP-1 secretion were reduced in humans carrying a total loss-of-function MC4R mutation. MC4R was localized to L cells and regulates GLP-1 and PYY secretion from ex vivo human intestine. α-MSH immunoreactivity in the human intestinal epithelia was predominantly localized to L cells. Glucose-sensitive mucosal pro-opiomelanocortin cells provide a local source of α-MSH that is essential for glucose-induced GLP-1 secretion in small intestine. CONCLUSION Our findings describe a previously unidentified signaling nexus in the human gastrointestinal tract involving α-MSH release and MC4R activation on L cells in an autocrine and paracrine fashion. Outcomes from this study have direct implications for targeting mucosal MC4R to treat human metabolic disorders.
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Affiliation(s)
- Emily W Sun
- Flinders Health and Medical Research Institute, College of Medicine and Public Health, Flinders University, Bedford Park, Australia
| | - Eva W Iepsen
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark; The Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, Copenhagen, Denmark
| | - Nektaria Pezos
- Nutrition, Diabetes and Metabolism, Lifelong Health, South Australia Health and Medical Research Institute, Adelaide, Australia; Adelaide Medical School and NHMRC Centre of Research Excellence in Translating Nutritional Science to Good Health, The University of Adelaide, Australia
| | - Amanda L Lumsden
- Flinders Health and Medical Research Institute, College of Medicine and Public Health, Flinders University, Bedford Park, Australia
| | - Alyce M Martin
- Flinders Health and Medical Research Institute, College of Medicine and Public Health, Flinders University, Bedford Park, Australia
| | - Gudrun Schober
- Nutrition, Diabetes and Metabolism, Lifelong Health, South Australia Health and Medical Research Institute, Adelaide, Australia; Adelaide Medical School and NHMRC Centre of Research Excellence in Translating Nutritional Science to Good Health, The University of Adelaide, Australia
| | - Nichole J Isaacs
- Nutrition, Diabetes and Metabolism, Lifelong Health, South Australia Health and Medical Research Institute, Adelaide, Australia; Adelaide Medical School and NHMRC Centre of Research Excellence in Translating Nutritional Science to Good Health, The University of Adelaide, Australia
| | - Christopher K Rayner
- Adelaide Medical School and NHMRC Centre of Research Excellence in Translating Nutritional Science to Good Health, The University of Adelaide, Australia; Department of Gastroenterology and Hepatology, Royal Adelaide Hospital, Adelaide, Australia
| | - Nam Q Nguyen
- Adelaide Medical School and NHMRC Centre of Research Excellence in Translating Nutritional Science to Good Health, The University of Adelaide, Australia; Department of Gastroenterology and Hepatology, Royal Adelaide Hospital, Adelaide, Australia
| | | | - Philippa Rabbitt
- Department of Surgery, Flinders Medical Centre, Bedford Park, Australia
| | - Paul Hollington
- Department of Surgery, Flinders Medical Centre, Bedford Park, Australia
| | - David A Wattchow
- Department of Surgery, Flinders Medical Centre, Bedford Park, Australia
| | - Torben Hansen
- The Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, Copenhagen, Denmark
| | - Jens-Christian Holm
- The Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, Copenhagen, Denmark; Department of Pediatrics, Holbæk University Hospital, Holbæk, Denmark
| | - Alice P Liou
- Cardiovascular and Metabolic Diseases Research Unit, Pfizer Worldwide Research and Development, Cambridge, Massachusetts
| | - V Margaret Jackson
- Cardiovascular and Metabolic Diseases Research Unit, Pfizer Worldwide Research and Development, Cambridge, Massachusetts
| | - Signe S Torekov
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark; The Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, Copenhagen, Denmark.
| | - Richard L Young
- Nutrition, Diabetes and Metabolism, Lifelong Health, South Australia Health and Medical Research Institute, Adelaide, Australia; Adelaide Medical School and NHMRC Centre of Research Excellence in Translating Nutritional Science to Good Health, The University of Adelaide, Australia.
| | - Damien J Keating
- Flinders Health and Medical Research Institute, College of Medicine and Public Health, Flinders University, Bedford Park, Australia.
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Castro J, Harrington AM, Lieu T, Garcia-Caraballo S, Maddern J, Schober G, O’Donnell T, Grundy L, Lumsden AL, Miller P, Ghetti A, Steinhoff MS, Poole DP, Dong X, Chang L, Bunnett NW, Brierley SM. Activation of pruritogenic TGR5, MrgprA3, and MrgprC11 on colon-innervating afferents induces visceral hypersensitivity. JCI Insight 2019; 4:131712. [PMID: 31536477 PMCID: PMC6824308 DOI: 10.1172/jci.insight.131712] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2019] [Accepted: 09/11/2019] [Indexed: 12/17/2022] Open
Abstract
Itch induces scratching that removes irritants from the skin, whereas pain initiates withdrawal or avoidance of tissue damage. While pain arises from both the skin and viscera, we investigated whether pruritogenic irritant mechanisms also function within visceral pathways. We show that subsets of colon-innervating sensory neurons in mice express, either individually or in combination, the pruritogenic receptors Tgr5 and the Mas-gene-related GPCRs Mrgpra3 and Mrgprc11. Agonists of these receptors activated subsets of colonic sensory neurons and evoked colonic afferent mechanical hypersensitivity via a TRPA1-dependent mechanism. In vivo intracolonic administration of individual TGR5, MrgprA3, or MrgprC11 agonists induced pronounced visceral hypersensitivity to colorectal distension. Coadministration of these agonists as an "itch cocktail" augmented hypersensitivity to colorectal distension and changed mouse behavior. These irritant mechanisms were maintained and enhanced in a model of chronic visceral hypersensitivity relevant to irritable bowel syndrome. Neurons from human dorsal root ganglia also expressed TGR5, as well as the human ortholog MrgprX1, and showed increased responsiveness to pruritogenic agonists in pathological states. These data support the existence of an irritant-sensing system in the colon that is a visceral representation of the itch pathways found in skin, thereby contributing to sensory disturbances accompanying common intestinal disorders.
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Affiliation(s)
- Joel Castro
- Visceral Pain Research Group, College of Medicine and Public Health, Flinders University, Bedford Park, South Australia, Australia
- Hopwood Centre for Neurobiology, Lifelong Health Theme, South Australian Health and Medical Research Institute (SAHMRI), North Terrace, Adelaide, South Australia, Australia
- Centre for Nutrition and Gastrointestinal Diseases, Discipline of Medicine, University of Adelaide, Adelaide, South Australia, Australia
| | - Andrea M. Harrington
- Visceral Pain Research Group, College of Medicine and Public Health, Flinders University, Bedford Park, South Australia, Australia
- Hopwood Centre for Neurobiology, Lifelong Health Theme, South Australian Health and Medical Research Institute (SAHMRI), North Terrace, Adelaide, South Australia, Australia
- Centre for Nutrition and Gastrointestinal Diseases, Discipline of Medicine, University of Adelaide, Adelaide, South Australia, Australia
| | - TinaMarie Lieu
- Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia
| | - Sonia Garcia-Caraballo
- Visceral Pain Research Group, College of Medicine and Public Health, Flinders University, Bedford Park, South Australia, Australia
- Hopwood Centre for Neurobiology, Lifelong Health Theme, South Australian Health and Medical Research Institute (SAHMRI), North Terrace, Adelaide, South Australia, Australia
- Centre for Nutrition and Gastrointestinal Diseases, Discipline of Medicine, University of Adelaide, Adelaide, South Australia, Australia
| | - Jessica Maddern
- Visceral Pain Research Group, College of Medicine and Public Health, Flinders University, Bedford Park, South Australia, Australia
- Hopwood Centre for Neurobiology, Lifelong Health Theme, South Australian Health and Medical Research Institute (SAHMRI), North Terrace, Adelaide, South Australia, Australia
- Centre for Nutrition and Gastrointestinal Diseases, Discipline of Medicine, University of Adelaide, Adelaide, South Australia, Australia
| | - Gudrun Schober
- Visceral Pain Research Group, College of Medicine and Public Health, Flinders University, Bedford Park, South Australia, Australia
- Hopwood Centre for Neurobiology, Lifelong Health Theme, South Australian Health and Medical Research Institute (SAHMRI), North Terrace, Adelaide, South Australia, Australia
- Centre for Nutrition and Gastrointestinal Diseases, Discipline of Medicine, University of Adelaide, Adelaide, South Australia, Australia
| | - Tracey O’Donnell
- Visceral Pain Research Group, College of Medicine and Public Health, Flinders University, Bedford Park, South Australia, Australia
- Hopwood Centre for Neurobiology, Lifelong Health Theme, South Australian Health and Medical Research Institute (SAHMRI), North Terrace, Adelaide, South Australia, Australia
- Centre for Nutrition and Gastrointestinal Diseases, Discipline of Medicine, University of Adelaide, Adelaide, South Australia, Australia
| | - Luke Grundy
- Visceral Pain Research Group, College of Medicine and Public Health, Flinders University, Bedford Park, South Australia, Australia
- Hopwood Centre for Neurobiology, Lifelong Health Theme, South Australian Health and Medical Research Institute (SAHMRI), North Terrace, Adelaide, South Australia, Australia
- Centre for Nutrition and Gastrointestinal Diseases, Discipline of Medicine, University of Adelaide, Adelaide, South Australia, Australia
| | - Amanda L. Lumsden
- Visceral Pain Research Group, College of Medicine and Public Health, Flinders University, Bedford Park, South Australia, Australia
- Hopwood Centre for Neurobiology, Lifelong Health Theme, South Australian Health and Medical Research Institute (SAHMRI), North Terrace, Adelaide, South Australia, Australia
- Centre for Nutrition and Gastrointestinal Diseases, Discipline of Medicine, University of Adelaide, Adelaide, South Australia, Australia
| | - Paul Miller
- AnaBios Corporation, San Diego, California, USA
| | | | - Martin S. Steinhoff
- Department of Dermatology and Dermatology Immunology Institute, Hamad Medical Corporation, Doha, Qatar
- Department of Dermatology, Weill Cornell Medicine-Qatar and Weill Cornell University, New York, New York, USA
- School of Medicine Qatar University, Doha, Qatar
| | - Daniel P. Poole
- Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia
- Australian Research Council Centre of Excellence in Convergent Bio-Nano Science and Technology, Monash University, Parkville, Victoria, Australia
- Department of Anatomy and Neuroscience, University of Melbourne, Parkville, Victoria, Australia
| | - Xinzhong Dong
- The Solomon H. Snyder Department of Neuroscience, Center for Sensory Biology, School of Medicine, Howard Hughes Medical Institute, Johns Hopkins University, Baltimore, Maryland, USA
| | - Lin Chang
- G. Oppenheimer Centre for Neurobiology of Stress and Resilience, David Geffen School of Medicine at UCLA, UCLA, Los Angeles, California, USA
| | - Nigel W. Bunnett
- Department of Pharmacology and Therapeutics, University of Melbourne, Parkville, Victoria, Australia
- Department of Surgery and
- Department of Pharmacology, Columbia University, New York, New York, USA
| | - Stuart M. Brierley
- Visceral Pain Research Group, College of Medicine and Public Health, Flinders University, Bedford Park, South Australia, Australia
- Hopwood Centre for Neurobiology, Lifelong Health Theme, South Australian Health and Medical Research Institute (SAHMRI), North Terrace, Adelaide, South Australia, Australia
- Centre for Nutrition and Gastrointestinal Diseases, Discipline of Medicine, University of Adelaide, Adelaide, South Australia, Australia
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Lumsden AL, Rogers JT, Majd S, Newman M, Sutherland GT, Verdile G, Lardelli M. Dysregulation of Neuronal Iron Homeostasis as an Alternative Unifying Effect of Mutations Causing Familial Alzheimer's Disease. Front Neurosci 2018; 12:533. [PMID: 30150923 PMCID: PMC6099262 DOI: 10.3389/fnins.2018.00533] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2018] [Accepted: 07/16/2018] [Indexed: 12/12/2022] Open
Abstract
The overwhelming majority of dominant mutations causing early onset familial Alzheimer’s disease (EOfAD) occur in only three genes, PSEN1, PSEN2, and APP. An effect-in-common of these mutations is alteration of production of the APP-derived peptide, amyloid β (Aβ). It is this key fact that underlies the authority of the Amyloid Hypothesis that has informed Alzheimer’s disease research for over two decades. Any challenge to this authority must offer an alternative explanation for the relationship between the PSEN genes and APP. In this paper, we explore one possible alternative relationship – the dysregulation of cellular iron homeostasis as a common effect of EOfAD mutations in these genes. This idea is attractive since it provides clear connections between EOfAD mutations and major characteristics of Alzheimer’s disease such as dysfunctional mitochondria, vascular risk factors/hypoxia, energy metabolism, and inflammation. We combine our ideas with observations by others to describe a “Stress Threshold Change of State” model of Alzheimer’s disease that may begin to explain the existence of both EOfAD and late onset sporadic (LOsAD) forms of the disease. Directing research to investigate the role of dysregulation of iron homeostasis in EOfAD may be a profitable way forward in our struggle to understand this form of dementia.
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Affiliation(s)
- Amanda L Lumsden
- College of Medicine and Public Health, Flinders University, Adelaide, SA, Australia.,South Australian Health and Medical Research Institute, Adelaide, SA, Australia
| | - Jack T Rogers
- Neurochemistry Laboratory, Department of Psychiatry-Neuroscience, Massachusetts General Hospital (East), Harvard Medical School, Harvard University, Charlestown, MA, United States
| | - Shohreh Majd
- Neuronal Injury and Repair Laboratory, Centre for Neuroscience, College of Medicine and Public Health, Flinders University, Adelaide, SA, Australia
| | - Morgan Newman
- Centre for Molecular Pathology, School of Biological Sciences, University of Adelaide, Adelaide, SA, Australia
| | - Greg T Sutherland
- Discipline of Pathology, Sydney Medical School, University of Sydney, Sydney, NSW, Australia
| | - Giuseppe Verdile
- School of Pharmacy and Biomedical Sciences, Faculty of Health Sciences, Curtin Health Innovation Research Institute, Curtin University, Bentley, WA, Australia
| | - Michael Lardelli
- Centre for Molecular Pathology, School of Biological Sciences, University of Adelaide, Adelaide, SA, Australia
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10
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Lumsden AL, Ma Y, Ashander LM, Stempel AJ, Keating DJ, Smith JR, Appukuttan B. ICAM-1-related long non-coding RNA: promoter analysis and expression in human retinal endothelial cells. BMC Res Notes 2018; 11:285. [PMID: 29743093 PMCID: PMC5944171 DOI: 10.1186/s13104-018-3384-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2018] [Accepted: 04/30/2018] [Indexed: 11/22/2022] Open
Abstract
Objective Regulation of intercellular adhesion molecule (ICAM)-1 in retinal endothelial cells is a promising druggable target for retinal vascular diseases. The ICAM-1-related (ICR) long non-coding RNA stabilizes ICAM-1 transcript, increasing protein expression. However, studies of ICR involvement in disease have been limited as the promoter is uncharacterized. To address this issue, we undertook a comprehensive in silico analysis of the human ICR gene promoter region. Results We used genomic evolutionary rate profiling to identify a 115 base pair (bp) sequence within 500 bp upstream of the transcription start site of the annotated human ICR gene that was conserved across 25 eutherian genomes. A second constrained sequence upstream of the orthologous mouse gene (68 bp; conserved across 27 Eutherian genomes including human) was also discovered. Searching these elements identified 33 matrices predictive of binding sites for transcription factors known to be responsive to a broad range of pathological stimuli, including hypoxia, and metabolic and inflammatory proteins. Five phenotype-associated single nucleotide polymorphisms (SNPs) in the immediate vicinity of these elements included four SNPs (i.e. rs2569693, rs281439, rs281440 and rs11575074) predicted to impact binding motifs of transcription factors, and thus the expression of ICR and ICAM-1 genes, with potential to influence disease susceptibility. We verified that human retinal endothelial cells expressed ICR, and observed induction of expression by tumor necrosis factor-α. Electronic supplementary material The online version of this article (10.1186/s13104-018-3384-8) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Amanda L Lumsden
- Flinders University College of Medicine and Public Health, Flinders Medical Centre Room 4E-431, Flinders Drive, Bedford Park, SA, 5042, Australia
| | - Yuefang Ma
- Flinders University College of Medicine and Public Health, Flinders Medical Centre Room 4E-431, Flinders Drive, Bedford Park, SA, 5042, Australia
| | - Liam M Ashander
- Flinders University College of Medicine and Public Health, Flinders Medical Centre Room 4E-431, Flinders Drive, Bedford Park, SA, 5042, Australia
| | - Andrew J Stempel
- Flinders University College of Medicine and Public Health, Flinders Medical Centre Room 4E-431, Flinders Drive, Bedford Park, SA, 5042, Australia
| | - Damien J Keating
- Flinders University College of Medicine and Public Health, Flinders Medical Centre Room 4E-431, Flinders Drive, Bedford Park, SA, 5042, Australia
| | - Justine R Smith
- Flinders University College of Medicine and Public Health, Flinders Medical Centre Room 4E-431, Flinders Drive, Bedford Park, SA, 5042, Australia.
| | - Binoy Appukuttan
- Flinders University College of Medicine and Public Health, Flinders Medical Centre Room 4E-431, Flinders Drive, Bedford Park, SA, 5042, Australia
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11
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Young RL, Lumsden AL, Martin AM, Schober G, Pezos N, Thazhath SS, Isaacs NJ, Cvijanovic N, Sun EWL, Wu T, Rayner CK, Nguyen NQ, Fontgalland DD, Rabbitt P, Hollington P, Sposato L, Due SL, Wattchow DA, Liou AP, Jackson VM, Keating DJ. Augmented capacity for peripheral serotonin release in human obesity. Int J Obes (Lond) 2018; 42:1880-1889. [PMID: 29568107 DOI: 10.1038/s41366-018-0047-8] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Revised: 01/08/2018] [Accepted: 01/16/2018] [Indexed: 12/20/2022]
Abstract
BACKGROUND/OBJECTIVES Evidence from animal studies highlights an important role for serotonin (5-HT), derived from gut enterochromaffin (EC) cells, in regulating hepatic glucose production, lipolysis and thermogenesis, and promoting obesity and dysglycemia. Evidence in humans is limited, although elevated plasma 5-HT concentrations are linked to obesity. SUBJECTS/METHODS We assessed (i) plasma 5-HT concentrations before and during intraduodenal glucose infusion (4 kcal/min for 30 min) in non-diabetic obese (BMI 44 ± 4 kg/m2, N = 14) and control (BMI 24 ± 1 kg/m2, N = 10) subjects, (ii) functional activation of duodenal EC cells (immunodetection of phospho-extracellular related-kinase, pERK) in response to glucose, and in separate subjects, (iii) expression of tryptophan hydroxylase-1 (TPH1) in duodenum and colon (N = 39), and (iv) 5-HT content in primary EC cells from these regions (N = 85). RESULTS Plasma 5-HT was twofold higher in obese than control responders prior to (P = 0.025), and during (iAUC, P = 0.009), intraduodenal glucose infusion, and related positively to BMI (R2 = 0.334, P = 0.003) and HbA1c (R2 = 0.508, P = 0.009). The density of EC cells in the duodenum was twofold higher at baseline in obese subjects than controls (P = 0.023), with twofold more EC cells activated by glucose infusion in the obese (EC cells co-expressing 5-HT and pERK, P = 0.001), while the 5-HT content of EC cells in duodenum and colon was similar; TPH1 expression was 1.4-fold higher in the duodenum of obese subjects (P = 0.044), and related positively to BMI (R2 = 0.310, P = 0.031). CONCLUSIONS Human obesity is characterized by an increased capacity to produce and release 5-HT from the proximal small intestine, which is strongly linked to higher body mass, and glycemic control. Gut-derived 5-HT is likely to be an important driver of pathogenesis in human obesity and dysglycemia.
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Affiliation(s)
- Richard L Young
- Adelaide Medical School, The University of Adelaide, Adelaide, SA, 5005, Australia.,Nutrition & Metabolism, South Australian Health and Medical Research Institute (SAHMRI), Adelaide, SA, 5000, Australia
| | - Amanda L Lumsden
- Centre for Neuroscience & Department of Human Physiology, Flinders University, Bedford Park, SA, 5042, Australia
| | - Alyce M Martin
- Centre for Neuroscience & Department of Human Physiology, Flinders University, Bedford Park, SA, 5042, Australia
| | - Gudrun Schober
- Adelaide Medical School, The University of Adelaide, Adelaide, SA, 5005, Australia.,Nutrition & Metabolism, South Australian Health and Medical Research Institute (SAHMRI), Adelaide, SA, 5000, Australia
| | - Nektaria Pezos
- Adelaide Medical School, The University of Adelaide, Adelaide, SA, 5005, Australia.,Nutrition & Metabolism, South Australian Health and Medical Research Institute (SAHMRI), Adelaide, SA, 5000, Australia
| | - Sony S Thazhath
- Adelaide Medical School, The University of Adelaide, Adelaide, SA, 5005, Australia.,NHMRC Centre of Research Excellence in Translating Nutritional Science to Good Health, The University of Adelaide, Adelaide, SA, 5005, Australia
| | - Nicole J Isaacs
- Adelaide Medical School, The University of Adelaide, Adelaide, SA, 5005, Australia.,Nutrition & Metabolism, South Australian Health and Medical Research Institute (SAHMRI), Adelaide, SA, 5000, Australia
| | - Nada Cvijanovic
- Adelaide Medical School, The University of Adelaide, Adelaide, SA, 5005, Australia.,Nutrition & Metabolism, South Australian Health and Medical Research Institute (SAHMRI), Adelaide, SA, 5000, Australia
| | - Emily W L Sun
- Centre for Neuroscience & Department of Human Physiology, Flinders University, Bedford Park, SA, 5042, Australia
| | - Tongzhi Wu
- Adelaide Medical School, The University of Adelaide, Adelaide, SA, 5005, Australia.,NHMRC Centre of Research Excellence in Translating Nutritional Science to Good Health, The University of Adelaide, Adelaide, SA, 5005, Australia
| | - Christopher K Rayner
- Adelaide Medical School, The University of Adelaide, Adelaide, SA, 5005, Australia.,NHMRC Centre of Research Excellence in Translating Nutritional Science to Good Health, The University of Adelaide, Adelaide, SA, 5005, Australia
| | - Nam Q Nguyen
- Adelaide Medical School, The University of Adelaide, Adelaide, SA, 5005, Australia.,NHMRC Centre of Research Excellence in Translating Nutritional Science to Good Health, The University of Adelaide, Adelaide, SA, 5005, Australia
| | - Dayan de Fontgalland
- Department of Surgery, Flinders Medical Centre, Bedford Park, SA, 5042, Australia
| | - Philippa Rabbitt
- Department of Surgery, Flinders Medical Centre, Bedford Park, SA, 5042, Australia
| | - Paul Hollington
- Department of Surgery, Flinders Medical Centre, Bedford Park, SA, 5042, Australia
| | - Luigi Sposato
- Department of Surgery, Flinders Medical Centre, Bedford Park, SA, 5042, Australia
| | - Steven L Due
- Department of Surgery, Flinders Medical Centre, Bedford Park, SA, 5042, Australia
| | - David A Wattchow
- Department of Surgery, Flinders Medical Centre, Bedford Park, SA, 5042, Australia
| | - Alice P Liou
- Cardiovascular, Metabolic, and Endocrine Diseases Research Unit, Pfizer Worldwide Research and Development, Cambridge, MA, 02139, USA
| | - V Margaret Jackson
- Cardiovascular, Metabolic, and Endocrine Diseases Research Unit, Pfizer Worldwide Research and Development, Cambridge, MA, 02139, USA
| | - Damien J Keating
- Nutrition & Metabolism, South Australian Health and Medical Research Institute (SAHMRI), Adelaide, SA, 5000, Australia. .,Centre for Neuroscience & Department of Human Physiology, Flinders University, Bedford Park, SA, 5042, Australia.
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12
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Martin AM, Lumsden AL, Young RL, Jessup CF, Spencer NJ, Keating DJ. Regional differences in nutrient-induced secretion of gut serotonin. Physiol Rep 2017; 5:5/6/e13199. [PMID: 28320893 PMCID: PMC5371566 DOI: 10.14814/phy2.13199] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2017] [Revised: 02/15/2017] [Accepted: 02/16/2017] [Indexed: 12/17/2022] Open
Abstract
Enterochromaffin (EC) cells located in the gastrointestinal (GI) tract provide the vast majority of serotonin (5-HT) in the body and constitute half of all enteroendocrine cells. EC cells respond to an array of stimuli, including various ingested nutrients. Ensuing 5-HT release from these cells plays a diverse role in regulating gut motility as well as other important responses to nutrient ingestion such as glucose absorption and fluid balance. Recent data also highlight the role of peripheral 5-HT in various pathways related to metabolic control. Details related to the manner by which EC cells respond to ingested nutrients are scarce and as that the nutrient environment changes along the length of the gut, it is unknown whether the response of EC cells to nutrients is dependent on their GI location. The aim of the present study was to identify whether regional differences in nutrient sensing capability exist in mouse EC cells. We isolated mouse EC cells from duodenum and colon to demonstrate differential responses to sugars depending on location. Measurements of intracellular calcium concentration and 5-HT secretion demonstrated that colonic EC cells are more sensitive to glucose, while duodenal EC cells are more sensitive to fructose and sucrose. Short-chain fatty acids (SCFAs), which are predominantly synthesized by intestinal bacteria, have been previously associated with an increase in circulating 5-HT; however, we find that SCFAs do not acutely stimulate EC cell 5-HT release. Thus, we highlight that EC cell physiology is dictated by regional location within the GI tract, and identify differences in the regional responsiveness of EC cells to dietary sugars.
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Affiliation(s)
- Alyce M Martin
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, Australia
| | - Amanda L Lumsden
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, Australia
| | - Richard L Young
- South Australian Health and Medical Research Institute (SAHMRI), Adelaide, Australia.,Adelaide Medical School, University of Adelaide, Adelaide, Australia
| | - Claire F Jessup
- Department of Anatomy and Histology and Centre for Neuroscience, Flinders University, Adelaide, Australia.,Adelaide Medical School, University of Adelaide, Adelaide, Australia
| | - Nick J Spencer
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, Australia
| | - Damien J Keating
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, Australia .,South Australian Health and Medical Research Institute (SAHMRI), Adelaide, Australia
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13
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Martin AM, Lumsden AL, Young RL, Jessup CF, Spencer NJ, Keating DJ. The nutrient-sensing repertoires of mouse enterochromaffin cells differ between duodenum and colon. Neurogastroenterol Motil 2017; 29. [PMID: 28251760 DOI: 10.1111/nmo.13046] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/23/2016] [Revised: 01/11/2017] [Accepted: 01/12/2017] [Indexed: 01/30/2023]
Abstract
BACKGROUND Enterochromaffin (EC) cells within the gastrointestinal (GI) tract provide almost all body serotonin (5-hydroxytryptamine [5-HT]). Peripheral 5-HT, released from EC cells lining the gut wall, serves diverse physiological roles. These include modulating GI motility, bone formation, hepatic gluconeogenesis, thermogenesis, insulin resistance, and regulation of fat mass. Enterochromaffin cells are nutrient sensors, but which nutrients they are responsive to and how this changes in different parts of the GI tract are poorly understood. METHODS To accurately undertake such an examination, we undertook the first isolation and purification of primary mouse EC cells from both the duodenum and colon in the same animal. This allowed us to compare, in an internally controlled manner, regional differences in the expression of nutrient sensors in EC cells using real-time PCR. KEY RESULTS Both colonic and duodenal EC cells expressed G protein-coupled receptors and facilitative transporters for sugars, free fatty acids, amino acids, and lipid amides. We find differential expression of nutrient receptor and transporters in EC cells obtained from duodenal and colonic EC cells. Duodenal EC cells have higher expression of tryptophan hydroxylase-1, sugar transporters GLUT2, GLUT5, and free fatty acid receptors 1 and 3 (FFAR1 and FFAR3). Colonic EC cells express higher levels of GLUT1, FFAR2, and FFAR4. CONCLUSIONS & INFERENCES We highlight the diversity of EC cell physiology and identify differences in the regional sensing repertoire of EC cells to an assortment of nutrients. These data indicate that not all EC cells are similar and that differences in their physiological responses are likely dependent on their location within the GI tract.
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Affiliation(s)
- A M Martin
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, SA, Australia
| | - A L Lumsden
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, SA, Australia
| | - R L Young
- South Australian Health and Medical Research Institute (SAHMRI), Adelaide, SA, Australia.,Adelaide Medical School, University of Adelaide, Adelaide, SA, Australia
| | - C F Jessup
- Adelaide Medical School, University of Adelaide, Adelaide, SA, Australia.,Department of Anatomy and Histology and Centre for Neuroscience, Flinders University, Adelaide, SA, Australia
| | - N J Spencer
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, SA, Australia
| | - D J Keating
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, SA, Australia.,South Australian Health and Medical Research Institute (SAHMRI), Adelaide, SA, Australia
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14
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Lumsden AL, Young RL, Pezos N, Keating DJ. Huntingtin-associated protein 1: Eutherian adaptation from a TRAK-like protein, conserved gene promoter elements, and localization in the human intestine. BMC Evol Biol 2016; 16:214. [PMID: 27737633 PMCID: PMC5064798 DOI: 10.1186/s12862-016-0780-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Accepted: 09/29/2016] [Indexed: 11/28/2022] Open
Abstract
Background Huntingtin-associated Protein 1 (HAP1) is expressed in neurons and endocrine cells, and is critical for postnatal survival in mice. HAP1 shares a conserved “HAP1_N” domain with TRAfficking Kinesin proteins TRAK1 and TRAK2 (vertebrate), Milton (Drosophila) and T27A3.1 (C. elegans). HAP1, TRAK1 and TRAK2 have a degree of common function, particularly regarding intracellular receptor trafficking. However, TRAK1, TRAK2 and Milton (which have a “Milt/TRAK” domain that is absent in human and rodent HAP1) differ in function to HAP1 in that they are mitochondrial transport proteins, while HAP1 has emerging roles in starvation response. We have investigated HAP1 function by examining its evolution, and upstream gene promoter sequences. We performed phylogenetic analyses of the HAP1_N domain family of proteins, incorporating HAP1 orthologues (identified by genomic synteny) from 5 vertebrate classes, and also searched the Dictyostelium proteome for a common ancestor. Computational analyses of mammalian HAP1 gene promoters were performed to identify phylogenetically conserved regulatory motifs. Results We found that as recently as marsupials, HAP1 contained a Milt/TRAK domain and was more similar to TRAK1 and TRAK2 than to eutherian HAP1. The Milt/TRAK domain likely arose post multicellularity, as it was absent in the Dictyostelium proteome. It was lost from HAP1 in the eutherian lineage, and also from T27A3.1 in C. elegans. The HAP1 promoter from human, mouse, rat, rabbit, horse, dog, Tasmanian devil and opossum contained common sites for transcription factors involved in cell cycle, growth, differentiation, and stress response. A conserved arrangement of regulatory elements was identified, including sites for caudal-related homeobox transcription factors (CDX1 and CDX2), and myc-associated factor X (MAX) in the region of the TATA box. CDX1 and CDX2 are intestine-enriched factors, prompting investigation of HAP1 protein expression in the human duodenum. HAP1 was localized to singly dispersed mucosal cells, including a subset of serotonin-positive enterochromaffin cells. Conclusion We have identified eutherian HAP1 as an evolutionarily recent adaptation of a vertebrate TRAK protein-like ancestor, and found conserved CDX1/CDX2 and MAX transcription factor binding sites near the TATA box in mammalian HAP1 gene promoters. We also demonstrated that HAP1 is expressed in endocrine cells of the human gut. Electronic supplementary material The online version of this article (doi:10.1186/s12862-016-0780-3) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Amanda L Lumsden
- Centre for Neuroscience and Department of Human Physiology, Flinders University, Adelaide, South Australia, Australia.
| | - Richard L Young
- South Australian Health and Medical Research Institute, Adelaide, South Australia, Australia.,Department of Medicine, University of Adelaide, Adelaide, South Australia, Australia
| | - Nektaria Pezos
- South Australian Health and Medical Research Institute, Adelaide, South Australia, Australia.,Department of Medicine, University of Adelaide, Adelaide, South Australia, Australia
| | - Damien J Keating
- Centre for Neuroscience and Department of Human Physiology, Flinders University, Adelaide, South Australia, Australia. .,South Australian Health and Medical Research Institute, Adelaide, South Australia, Australia.
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15
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Mackenzie KD, Lumsden AL, Guo F, Duffield MD, Chataway T, Lim Y, Zhou XF, Keating DJ. Huntingtin-associated protein-1 is a synapsin I-binding protein regulating synaptic vesicle exocytosis and synapsin I trafficking. J Neurochem 2016; 138:710-21. [PMID: 27315547 DOI: 10.1111/jnc.13703] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Revised: 06/14/2016] [Accepted: 06/15/2016] [Indexed: 12/27/2022]
Abstract
Huntingtin-associated protein-1 (HAP1) is involved in intracellular trafficking, vesicle transport, and membrane receptor endocytosis. However, despite such diverse functions, the role of HAP1 in the synaptic vesicle (SV) cycle in nerve terminals remains unclear. Here, we report that HAP1 functions in SV exocytosis, controls total SV turnover and the speed of vesicle fusion in nerve terminals and regulates glutamate release in cortical brain slices. We found that HAP1 interacts with synapsin I, an abundant neuronal phosphoprotein that associates with SVs during neurotransmitter release and regulates synaptic plasticity and neuronal development. The interaction between HAP1 with synapsin I was confirmed by reciprocal co-immunoprecipitation of the endogenous proteins. Furthermore, HAP1 co-localizes with synapsin I in cortical neurons as discrete puncta. Interestingly, we find that synapsin I localization is specifically altered in Hap1(-/-) cortical neurons without an effect on the localization of other SV proteins. This effect on synapsin I localization was not because of changes in the levels of synapsin I or its phosphorylation status in Hap1(-/-) brains. Furthermore, fluorescence recovery after photobleaching in transfected neurons expressing enhanced green fluorescent protein-synapsin Ia demonstrates that loss of HAP1 protein inhibits synapsin I transport. Thus, we demonstrate that HAP1 regulates SV exocytosis and may do so through binding to synapsin I. The Proposed mechanism of synapsin I transport mediated by HAP1 in neurons. HAP1 interacts with synapsin I, regulating the trafficking of synapsin I containing vesicles and/or transport packets, possibly through its engagement of microtubule motors. The absence of HAP1 reduces synapsin I transport and neuronal exocytosis. These findings provide insights into the processes of neuronal trafficking and synaptic signaling.
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Affiliation(s)
- Kimberly D Mackenzie
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, South Australia, Australia
| | - Amanda L Lumsden
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, South Australia, Australia
| | - Feng Guo
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, South Australia, Australia
| | - Michael D Duffield
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, South Australia, Australia
| | - Timothy Chataway
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, South Australia, Australia
| | - Yoon Lim
- Sansom Institute, University of South Australia, Adelaide, South Australia, Australia
| | - Xin-Fu Zhou
- Sansom Institute, University of South Australia, Adelaide, South Australia, Australia
| | - Damien J Keating
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, South Australia, Australia.,South Australian Health and Medical Research Institute, Adelaide, South Australia, Australia
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Zelkas L, Raghupathi R, Lumsden AL, Martin AM, Sun E, Spencer NJ, Young RL, Keating DJ. Serotonin-secreting enteroendocrine cells respond via diverse mechanisms to acute and chronic changes in glucose availability. Nutr Metab (Lond) 2015; 12:55. [PMID: 26673561 PMCID: PMC4678665 DOI: 10.1186/s12986-015-0051-0] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2015] [Accepted: 12/09/2015] [Indexed: 01/11/2023] Open
Abstract
Background Enteroendocrine cells collectively constitute our largest endocrine tissue, with serotonin (5-HT) secreting enterochromaffin (EC) cells being the largest component (~50 %). This gut-derived 5-HT has multiple paracrine and endocrine roles. EC cells are thought to act as nutrient sensors and luminal glucose is the major absorbed form of carbohydrate in the gut and activates secretion in an array of cell types. It is unknown whether EC cells release 5-HT in response to glucose in primary EC cells. Furthermore, fasting augments 5-HT synthesis and release into the circulation. However, which nutrients cause fasting-induced synthesis of EC cell 5-HT is unknown. Here we examine the effects of acute and chronic changes in glucose availability on 5-HT release from intact tissue and single EC cells. Methods We utilised established approaches in our laboratories measuring 5-HT release in intact mouse colon with amperometry. We then examined single EC cells function using our published protocol in guinea-pig colon. Single cell Ca2+ imaging and amperometry were used with these cells. Real-time PCR was used along with amperometry, on primary EC cells cultured for 24 h in 5 or 25 mM glucose. Results We demonstrate that acute increases in glucose, at levels found in the gut lumen rather than in plasma, trigger 5-HT release from intact colon, and cause Ca2+ entry and 5-HT release in primary EC cells. Single cell amperometry demonstrates that high glucose increases the amount of 5-HT released from individual vesicles as they undergo exocytosis. Finally, 24 h incubation of EC cells in low glucose causes an increase in the transcription of the 5-HT synthesising enzyme Tph1 as well as increasing in 5-HT secretion in EC cells. Conclusions We demonstrate that primary EC cells respond to acute changes in glucose availability through increases in intracellular Ca2+ the activation of 5-HT secretion, but respond to chronic changes in glucose levels through the transcriptional regulation of Tph1 to alter 5-HT synthesis.
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Affiliation(s)
- Leah Zelkas
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Sturt Rd, Adelaide, SA 5042 Australia
| | - Ravi Raghupathi
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Sturt Rd, Adelaide, SA 5042 Australia ; South Australian Health and Medical Research Institute (SAHMRI), Adelaide, 5001 Australia
| | - Amanda L Lumsden
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Sturt Rd, Adelaide, SA 5042 Australia ; South Australian Health and Medical Research Institute (SAHMRI), Adelaide, 5001 Australia
| | - Alyce M Martin
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Sturt Rd, Adelaide, SA 5042 Australia ; South Australian Health and Medical Research Institute (SAHMRI), Adelaide, 5001 Australia
| | - Emily Sun
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Sturt Rd, Adelaide, SA 5042 Australia ; South Australian Health and Medical Research Institute (SAHMRI), Adelaide, 5001 Australia
| | - Nick J Spencer
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Sturt Rd, Adelaide, SA 5042 Australia
| | - Richard L Young
- South Australian Health and Medical Research Institute (SAHMRI), Adelaide, 5001 Australia ; Discipline of Medicine, University of Adelaide, Adelaide, SA 5001 Australia
| | - Damien J Keating
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Sturt Rd, Adelaide, SA 5042 Australia ; South Australian Health and Medical Research Institute (SAHMRI), Adelaide, 5001 Australia
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Raghupathi R, Jessup CF, Lumsden AL, Keating DJ. Fusion Pore Size Limits 5-HT Release From Single Enterochromaffin Cell Vesicles. J Cell Physiol 2015; 231:1593-600. [PMID: 26574734 DOI: 10.1002/jcp.25256] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2015] [Accepted: 11/13/2015] [Indexed: 12/15/2022]
Abstract
Enterochromaffin cells are the major site of serotonin (5-HT) synthesis and secretion providing ∼95% of the body's total 5-HT. 5-HT can act as a neurotransmitter or hormone and has several important endocrine and paracrine roles. We have previously demonstrated that EC cells release small amounts of 5-HT per exocytosis event compared to other endocrine cells. We utilized a recently developed method to purify EC cells to demonstrate the mechanisms underlying 5-HT packaging and release. Using the fluorescent probe FFN511, we demonstrate that EC cells express VMAT and that VMAT plays a functional role in 5-HT loading into vesicles. Carbon fiber amperometry studies illustrate that the amount of 5-HT released per exocytosis event from EC cells is dependent on both VMAT and the H(+)-ATPase pump, as demonstrated with reserpine or bafilomycin, respectively. We also demonstrate that increasing the amount of 5-HT loaded into EC cell vesicles does not result in an increase in quantal release. As this indicates that fusion pore size may be a limiting factor involved, we compared pore diameter in EC and chromaffin cells by assessing the vesicle capture of different-sized fluorescent probes to measure the extent of fusion pore dilation. This identified that EC cells have a reduced fusion pore expansion that does not exceed 9 nm in diameter. These results demonstrate that the small amounts of 5-HT released per fusion event in EC cells can be explained by a smaller fusion pore that limits 5-HT release capacity from individual vesicles.
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Affiliation(s)
- Ravinarayan Raghupathi
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, Australia
| | - Claire F Jessup
- Department of Anatomy and Histology and Centre for Neuroscience, Flinders University, Adelaide, Australia.,Discipline of Medicine, University of Adelaide, Adelaide, Australia
| | - Amanda L Lumsden
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, Australia
| | - Damien J Keating
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, Australia.,South Australian Health and Medical Research Institute, Adelaide, Australia
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Affiliation(s)
- Richard L Young
- South Australian Health and Medical Research Institute (SAHMRI), Adelaide, Australia; Department of Medicine, University of Adelaide, Adelaide, Australia
| | - Amanda L Lumsden
- Centre for Neuroscience and Department of Human Physiology, Flinders University, Adelaide, Australia
| | - Damien J Keating
- South Australian Health and Medical Research Institute (SAHMRI), Adelaide, Australia; Centre for Neuroscience and Department of Human Physiology, Flinders University, Adelaide, Australia
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Myre MA, Lumsden AL, Thompson MN, Wasco W, MacDonald ME, Gusella JF. Deficiency of huntingtin has pleiotropic effects in the social amoeba Dictyostelium discoideum. PLoS Genet 2011; 7:e1002052. [PMID: 21552328 PMCID: PMC3084204 DOI: 10.1371/journal.pgen.1002052] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2010] [Accepted: 03/02/2011] [Indexed: 11/24/2022] Open
Abstract
Huntingtin is a large HEAT repeat protein first identified in humans, where a polyglutamine tract expansion near the amino terminus causes a gain-of-function mechanism that leads to selective neuronal loss in Huntington's disease (HD). Genetic evidence in humans and knock-in mouse models suggests that this gain-of-function involves an increase or deregulation of some aspect of huntingtin's normal function(s), which remains poorly understood. As huntingtin shows evolutionary conservation, a powerful approach to discovering its normal biochemical role(s) is to study the effects caused by its deficiency in a model organism with a short life-cycle that comprises both cellular and multicellular developmental stages. To facilitate studies aimed at detailed knowledge of huntingtin's normal function(s), we generated a null mutant of hd, the HD ortholog in Dictyostelium discoideum. Dictyostelium cells lacking endogenous huntingtin were viable but during development did not exhibit the typical polarized morphology of Dictyostelium cells, streamed poorly to form aggregates by accretion rather than chemotaxis, showed disorganized F-actin staining, exhibited extreme sensitivity to hypoosmotic stress, and failed to form EDTA-resistant cell–cell contacts. Surprisingly, chemotactic streaming could be rescued in the presence of the bivalent cations Ca2+ or Mg2+ but not pulses of cAMP. Although hd− cells completed development, it was delayed and proceeded asynchronously, producing small fruiting bodies with round, defective spores that germinated spontaneously within a glassy sorus. When developed as chimeras with wild-type cells, hd− cells failed to populate the pre-spore region of the slug. In Dictyostelium, huntingtin deficiency is compatible with survival of the organism but renders cells sensitive to low osmolarity, which produces pleiotropic cell autonomous defects that affect cAMP signaling and as a consequence development. Thus, Dictyostelium provides a novel haploid organism model for genetic, cell biological, and biochemical studies to delineate the functions of the HD protein. Genetic evidence in humans and mouse models of Huntington's disease suggests that the disease mutation confers a deleterious gain-of-function on huntingtin that acts through the deregulation of some aspect of the protein's normal function(s). While huntingtin's function is poorly understood, its evolutionary conservation makes investigation of its physiological role in lower organisms an attractive route that has yet to be fully exploited. Therefore, we have used Dictyostelium discoideum to study the consequences of huntingtin (hd) deficiency. Developing Dictyostelium cells chemotax to form a multicellular slug that forms a fruiting body, comprising dormant spores encased above dead stalk cells. We found that hd− cells were hypersensitive to hypoosmotic stress. When starved, hd− cells aggregate by accretion, showed disorganized F-actin, and failed to form EDTA-resistant cell–cell contacts. Surprisingly, chemotactic signaling was rescued with Ca2+ or Mg2+ but not pulses of cAMP. Development of hd− mutants produced small fruiting bodies with round, defective spores, and when mixed with wild-type cells they didn't differentiate into spores. Our results are consistent with mammalian studies that show huntingtin is a multifunctional protein involved in many biochemical processes; and, importantly, they establish Dictyostelium as a valuable experimental organism for exploring in biochemical detail huntingtin's normal function(s).
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Affiliation(s)
- Michael A. Myre
- Molecular Neurogenetics Unit, Center for Human Genetic Research, Massachusetts General Hospital, Boston, Massachusetts, United States of America
- * E-mail:
| | - Amanda L. Lumsden
- Molecular Neurogenetics Unit, Center for Human Genetic Research, Massachusetts General Hospital, Boston, Massachusetts, United States of America
| | - Morgan N. Thompson
- Molecular Neurogenetics Unit, Center for Human Genetic Research, Massachusetts General Hospital, Boston, Massachusetts, United States of America
| | - Wilma Wasco
- Genetics and Aging Research Unit, MassGeneral Institute for Neurodegenerative Disease, Massachusetts General Hospital, Charlestown, Massachusetts, United States of America
| | - Marcy E. MacDonald
- Molecular Neurogenetics Unit, Center for Human Genetic Research, Massachusetts General Hospital, Boston, Massachusetts, United States of America
| | - James F. Gusella
- Molecular Neurogenetics Unit, Center for Human Genetic Research, Massachusetts General Hospital, Boston, Massachusetts, United States of America
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Henshall TL, Tucker B, Lumsden AL, Nornes S, Lardelli MT, Richards RI. Selective neuronal requirement for huntingtin in the developing zebrafish. Hum Mol Genet 2009; 18:4830-42. [PMID: 19797250 PMCID: PMC2778375 DOI: 10.1093/hmg/ddp455] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2009] [Revised: 09/03/2009] [Accepted: 09/23/2009] [Indexed: 12/13/2022] Open
Abstract
Huntington's disease shares a common molecular basis with eight other neurodegenerative diseases, expansion of an existing polyglutamine tract. In each case, this repeat tract occurs within otherwise unrelated proteins. These proteins show widespread and overlapping patterns of expression in the brain and yet the diseases are distinguished by neurodegeneration in a specific subset of neurons that are most sensitive to the mutation. It has therefore been proposed that expansion of the polyglutamine region in these genes may result in perturbation of the normal function of the respective proteins, and that this perturbation in some way contributes to the neuronal specificity of these diseases. The normal functions of these proteins have therefore become a focus for investigation as potential pathogenic pathways. We have used synthetic antisense morpholinos to inhibit the translation of huntingtin mRNA during early zebrafish development and have previously reported the effects of huntingtin reduction on iron transport and homeostasis. Here we report an analysis of the effects of huntingtin loss-of-function on the developing nervous system, observing distinct defects in morphology of neuromasts, olfactory placode and branchial arches. The potential common origins of these defects were explored, revealing impaired formation of the anterior-most region of the neural plate as indicated by reduced pre-placodal and telencephalic gene expression with no effect on mid- or hindbrain formation. These investigations demonstrate a specific 'rate-limiting' role for huntingtin in formation of the telencephalon and the pre-placodal region, and differing levels of requirement for huntingtin function in specific nerve cell types.
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Affiliation(s)
| | | | | | | | | | - Robert I. Richards
- ARC Special Research Centre for the Molecular Genetics of Development and Discipline of Genetics, School of Molecular and Biomedical Sciences, The University of Adelaide, Adelaide, SA 5005, Australia
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Lumsden AL, Henshall TL, Dayan S, Lardelli MT, Richards RI. Huntingtin-deficient zebrafish exhibit defects in iron utilization and development. Hum Mol Genet 2007; 16:1905-20. [PMID: 17567778 DOI: 10.1093/hmg/ddm138] [Citation(s) in RCA: 125] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Huntington's disease (HD) is one of nine neurodegenerative disorders caused by expansion of CAG repeats encoding polyglutamine in their respective, otherwise apparently unrelated proteins. Despite these proteins having widespread and overlapping expression patterns in the brain, a specific and unique subset of neurons exhibits particular vulnerability in each disease. It has been hypothesized that perturbation of normal protein function contributes to the specificity of neuronal vulnerability; however, the normal biological functions of many of these proteins including the HD gene product, Huntingtin (Htt), are unclear. To explore the roles of Htt, we have used antisense morpholino oligonucleotides to observe the effects of Htt deficiency in early zebrafish development. Knockdown of Htt expression resulted in a variety of developmental defects. Most notably, Htt-deficient zebrafish had hypochromic blood due to decreased hemoglobin production, despite the presence of iron within blood cells. Furthermore, transferrin receptor 1 transcripts were increased, suggesting cellular iron starvation. Provision of iron to the cytoplasm in a bio-available form restored hemoglobin production in Htt-deficient embryos. Since erythroid cells acquire iron via receptor-mediated endocytosis of transferrin, these results suggest a role for Htt in making endocytosed iron accessible for cellular utilization. Iron is required for oxidative energy production, and defects in iron homeostasis and energy metabolism are features of HD pathogenesis that are most pronounced in the major region of neurodegeneration. It is therefore plausible that perturbation of Htt's normal role in the iron pathway (by polyglutamine tract expansion) contributes to HD pathology, and particularly to its neuronal specificity.
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Affiliation(s)
- Amanda L Lumsden
- ARC Special Research Centre for the Molecular Genetics of Development and Discipline of Genetics, School of Molecular and Biomedical Science, The University of Adelaide, Adelaide, SA, Australia
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