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Dr. Jacques Genest Jr. Laboratory Page

Recent Publications

2006

Lee C-Y, Vincent J, Lesimple A, Larsen Å, --Laliberté J, Denis M, Mamer O, Krimbou L Genest J, Marcil M. Increased sphingomyelin content of HDL impairs HDL biogenesis and maturation in human Niemann-Pick Disease Type B. J Lipid Res 2006;47:322-332. [CIHR MOP 15042] [CIHR MOP 62834] [HSFC] [*]

E. Lonn, C. Held, J.M.O. Arnold, J. Probstfield, M.J. McQueen, M. Micks, J. Pogue, P. Sheridan, J. Bosch, J. Genest, S. Yusuf. Rationale, Design and Baseline Characteristics of a Large, Simple, Randomized Trial of Combined Folic Acid and Vitamins B6 and B12 in High-Risk Patients. The Heart Outcomes Prevention Evaluation (HOPE) ?2 Trial. The HOPE-2 Investigators*. Can J Cardiol 2006;22:47-53

Dastani Z, Dangoisse C, Boucher B, DesBiens K, Dufour R, Hegele R, Paivi Pajukanta, Jamie Engert, Krimbou L, Genest J, Marcil M. A Novel Mutation of Apolipoprotein AI (Apo AIE136X) Causes a low HDL-C in French Canadians. Atheroscler 2006;185(1):127-136 [CIHR MOP 62834] [*]

Dastani Z, Quiogue L, Engert JC, Plaisier C, Marcil M, Genest J, Pajukanta P. Evidence of a gene influencing HDL-C on chromosome 4q31.21. Atheroscler Thromb Vasc Biol 2006;26(2):392-7 [*] [CIHR MOP 62834] Dec 1 e-pub PMID 16322534

 Hobbs FD, Gensini G, Mancini JB, Manolis AJ, Bauer B, Bohler S, Genest J, Feldman R, Harvey P, Jenssen TG, Metclafe M, Marques da Silva P, on behalf of the Jewel investigators. Rationale and design for an iInternational, open-label program to assess the effectiveness of a single pill (amlodipine / atorvastatin) to attain recommended target levels for blood pressure and lipids(The JEWEL I and II studies): Int J Cardiol. 2006;110(2):242-50

 Hassan HH, Denis M, Krimbou L, Genest J. Cellular cholesterol homeostasis in vascular endothelial cells. Can J Cardiol 2006;22:35B-40B suppl [CIHR MOP 15042] [*]

Mikael LG, Genest J, Rozen R. Elevated homocysteine reduces expression of apolipoprotein AI in hyperhomocysteinemic mice and in males with coronary artery disease.Circulation Research 2006;98:564-71 [CIHR MOP 15042]

(Clarke R et al. Genest J, collaborator) Homocysteine-lowering trials for the prevention of cardiovascular events: A review of the designs and power of large randomized trials. B-vitamins treatment trialists'. Am Heart J 2006;151:282-87

White M, Ross H, Haddad H, Leblanc M-H, Racine N, Plugfelder P, Giannetti N, Davies R, Azevedo E, Isaac D, Burton J, Ferguson R, Genest J. Subclinical inflammation and prothrombotic state in heart transplant recipients: impact of cyclosporin microemulsion vs. tacrolimus. Transplantation, 2006

Genest J. Combination of Statin and Ezetimibe for the Treatment of Dyslipidemias and the Prevention of Coronary Artery Disease. Can J Cardiol 2006

 The HOPE-2 Investigators. E. Lonn, S. Yusuf, J. M. O. Arnold, P. Sheridan, M. J. McQueen, J. Pogue, J. Probstfield, G. Fodor, C. Held, M. Micks, Genest J. Jr.. Homocysteine lowering with folic acid and B vitamins in vascular disease: The Heart Outcomes Prevention Evaluation (HOPE) -2 Trial. New Eng J Med 2006, March 13th, 2006

Dastani Z, Engert JC, Genest J, Marcil M. Genetics of High-Density Lipoproteins. Curr Op Cardiol 2006;21:329-335 [CIHR MOP 62834] [?]

Marcil M, Vu H, Cui W, Dastani Z, Engert J, Gaudet D, Castro-Cabezas  M, Sniderman AD, Genest J, Cinaflone K. Identification of a C5L2 mutation in a Québec family. Atheroscler Thromb Vasc Biol 2006 [CIHR MOP 62834] [*] e-pub Apr 20, 2006 ATV.0000222907.72985.0b

Krimbou L, Marcil M, Genest J. New Insights Into the Biogenesis of Human High Density Lipoprotein. Curr Op Lipidol 2006;17:258-267 [CIHR MOP 15042]

 

2005

Dorval J-F, Anderson T, Buithieu J, Shan S, Hutchison S, Huyhn T, Jobin J, Lonn E, Poirier J, Title L, Walling A, Charbonneau F, Genest J. Reaching recommended lipid and blood pressure targets with amlodipine/atorvastatin combination in patients with CAD. Am J Cardiol 2005;95:249-253

Alawadhi M, Thanassoulis G, Marcil M, Genest J. Genetics of Coronary Atherosclerosis. Current Atheroscler Rep  2005;7:196-203 [CIHR MOP 62834]

Genest J, McPherson R, Frohlich J, Fodor G. The analysis by Manuel and colleagues creates controversy with headlines, not data. Can Med Ass J 2005;172:1033-4

 Lee C-Y, Lesimple A, Larsen A, Mamer O, Genest J. Electron spray ionization – mass spectroscopy quantitation of increased sphingomyelin in Niemann-Pick disease B HDL. J Lipid Res 2005;46(6)1213-1228 e-pub 15741650 [CIHR MOP 15042]

 Krimbou L, Hassan HH, Blain S, Rashid S, Denis M, Marcil M, Genest J. Biogenesis and speciation of nascent apo AI – containing particles in various cell lines. J Lipid Res 2005;46:1668-1677 [CIHR MOP 15042] [*]

White W, Haddad H, LeBlanc M-H, Giannetti N, Pfugfelder P,Davies R,Isaac D, Burton J, Chan M, Azevedo E, Howlett J, Ignaszewski A, Busque S, Cantarovich M, Ferguson R, Genest J, Ross H Conversion from Cyclosporine microemulsion to Tacrolimus-based Immunoprophylaxis Improves Cholesterol Profile in Heart Transplant Recipients with Treated but Persistent Dyslipidemia. The Canadian Multicentre Randomized Trial of Tacrolimus vs. Cyclosporine microemulsion. J Heart Lung Transplant 2005;24(7):798-809

Hassan HH, Blain S , Boucher B, Denis M, Krimbou L, Genest J.  Structural Modification of Plasma HDL by Phospholipids Promotes Efficient ABCA1-mediated Cholesterol Release. J Lipid Res 2005;46:1457-65 [CIHR MOP 15042] [*]

Bourgault,  Davignon J, Fodor G, Gagné C, Gaudet D, Genest J, Lavoie, M-A, Leiter L, McPherson R, Sénécal M, Marentette M, Sebaldt R.  Statin therapy in Canadian patients with hypercholesterolemia: the CALIPSO study. Can J Cardiol 2005;21:1187-93

Dastani Z, Dangoisse C, Boucher B, DesBiens K, Dufour R, Hegele R, Paivi Pajukanta, Jamie Engert, Krimbou L, Genest  J, Marcil M. A Novel Mutation of Apolipoprotein AI (Apo AIE136X) Causes a low HDL-C in French Canadians. [CIHR MOP 62834] [*] Atheroscler 2005; July 12 pub med PMID 16023124

 Alrasadi K, Ruel I, Marcil M, Genest J. Functional mutations in the ABCA1 gene in subjects of French Canadian descent with HDL deficiency [CIHR MOP 62834] [*] Atheroscler 2005 Dec 7 (e-pub)

 Dastani Z, Quiogue L, Engert JC, Plaisier C, Marcil M, Genest J,  Pajukanta P. Evidence of a gene influencing HDL-C on chromosome 4q31.21. [*] [CIHR MOP 62834] Atheroscler Thromb Vasc Biol 2005 Dec 1 e-pub PMID 16322534

 Lee C-Y, Vincent J, Lesimple A, Larsen Å, ­­Laliberté J, Denis M, Mamer O, Krimbou L Genest J, Marcil M. Increased sphingomyelin content of HDL impairs HDL biogenesis and maturation in human Niemann-Pick Disease Type B. J Lipid Res Nov 2005 Nov 30 e-pub PMID 16319418 [CIHR MOP 15042] [CIHR MOP 62834] [HSFC] [*]

 Hobbs FD, Gensini G, Mancini JB, Manolis AJ, Bauer B, Bohler S, Genest J, Feldman R, Harvey P, Jenssen TG, Metclafe M, Marques da Silva P, on behalf of the Jewel investigators. Rationale and design for an iInternational, open-label program to assess the effectiveness of a single pill (amlodipine / atorvastatin) to attain recommended target levels for blood pressure and lipids(The JEWEL I and II studies):  Intl J Cardiol 2005 Dec 7 (e-pub)

 

2003

1: Marcil M, Bissonnette R, Vincent J, Krimbou L, Genest J. Related Articles, Links Cellular phospholipid and cholesterol efflux in high-density lipoprotein deficiency. Circulation. 2003 Mar 18;107(10):1366-71.

PMID: 12642355 [PubMed - in process]

2: Krimbou L, Marcil M, Chiba H, Genest J Jr. Related Articles, Links Structural and functional properties of human plasma high density-sized lipoprotein containing only apoE particles (HDL-LpE). J Lipid Res. 2003 Mar 1 [epub ahead of print]

PMID: 12611904 [PubMed - as supplied by publisher]

3: Lee CY, Krimbou L, Vincent J, Bernard C, Larramee P, Genest J Jr, Marcil M. Related Articles, Links Compound heterozygosity at the sphingomyelin phosphodiesterase-1 (SMPD1) gene is associated with low HDL cholesterol. Hum Genet. 2003 Feb 27 [epub ahead of print]

PMID: 12607113 [PubMed - as supplied by publisher]

4: Sniderman AD, Zhang Z, Genest J, Cianflone K. Related Articles, Links Effects on apoB-100 secretion and bile acid synthesis by redirecting cholesterol efflux from HepG2 cells. J Lipid Res. 2003 Mar;44(3):527-32.

PMID: 12562860 [PubMed - in process]

5: Zha X, Gauthier A, Genest J, McPherson R. Related Articles, Links Secretory Vesicular Transport from the Golgi Is Altered during ATP-binding Cassette Protein A1 (ABCA1)-mediated Cholesterol Efflux. J Biol Chem. 2003 Mar 21;278(12):10002-5.

PMID: 12551894 [PubMed - in process]

6: Schwahn BC, Chen Z, Laryea MD, Wendel U, Lussier-Cacan S, Genest J Jr, Mar MH, Zeisel SH, Castro C, Garrow T, Rozen R. Related Articles, Links Homocysteine-betaine interactions in a murine model of 5,10-methylenetetrahydrofolate reductase deficiency. FASEB J. 2003 Mar;17(3):512-4.

7. Denis M, Bissonnette R, O'Connell B, Haidar B, Krimbou L, Bouvier M, Genest J Jr, Expression, regulation and activity of ABCA1 in human cell lines. Mol Genet Metab 2003 2003;78:265-274

8.Denis M, Haidar B, Marcil M, Krimbou L, Genest J. Molecular and cellular physiology of apolipoprotein A-I lipidation by ATP biding cassette A1 (ABCA1). J Biol Chem published December 4, 2003 as doi:10.1074/jbc.M306963200

 

Genetics of High Density Lipoproteins

Genetic lipoprotein disorders are frequently encountered in patients with premature coronary artery disease (CAD). In recent years, the emphasis has shifted from the identification of single gene disorders being causally linked to disease states, to the study of complex metabolic disorders which, because of their effects of cardiovascular risk factors, are a major cause of CAD in affluent Western societies and in emerging market economies. The identification of single genes disorders may lead the way to the better understanding of complex metabolic pathways. Because of their importance on lipoprotein metabolism and vascular endothelial function, understanding the genes that regulate HDL metabolism may pave the way for novel therapeutic approaches

Hypothesis

HDL deficiency is genetically heterogeneous; the study of well characterized probands and families will allow the identification of novel genes related to high density lipoproteins.

Objectives

The objective of this proposal is to discover new genes leading to disorders of HDL. We will target patients with low plasma levels of HDL-C, defined as a plasma HDL-C <5th percentile for age and gender and subjects with elevated HDL-C, >95th percentile. Strict entry criteria will eliminate confounding factors (medications, hormones, concomitant illness –diabetes, cancer, alcohol intake).

Specific Aims

In addition to collecting probands and their families, we will use three approaches to identify the genes involved in HDL.

Probands. Collection of probands with HDL-C <5th percentile for age and gender-matched subjects defining hypoalphalipoproteinemia (HA), and with an HDL-C >95th precentile, defining hyperalphalipoproteinemia (HAL).
Family studies. Collection of extended families with hypoalphalipoproteinemia. Objectives 1 and 2 have been ongoing for the past several years
Candidate gene approach. Candidate genes will be screened either by direct sequencing or by haplotyping a collection of well characterized families, using informative markers near the genes of interest.
Genome-wide scan. In families with sufficient meiosis and affected individuals, we will perform genome-wide scan on individual families, using a set of 400-800 markers situated at intervals of ~4-10 centiMorgans (cM). Using a positional cloning strategy, as well as candidate genes obtained from in-silico research on the human genome project database, we plan to identify and sequence novel genes leading to disorders of HDL metabolism. We will also examine the genome scan data to determine the presence of quantative trait loci (QTL) for HDL-C in a set of combined families.
Gene expression micro arrays. In selected individuals, in whom a clear cellular phenotype can be determined based on the examination of cellular lipid homeostasis and in whom specific candidate genes have been eliminated, we plan to use gene expression arrays to examine genes expressed in conditions of cellular cholesterol loading. This approach has been used by Lawn et al. [Lawn 2000] to identify the ABCA1 gene in their families with Tangier disease. We have also successfully used this approach in human vascular endothelial cells to identify the ABCG1 gene in promoting cellular cholesterol efflux.

 

This proposal is CIHR funded (2003-2006). A recent Canadian Fund for Innovation award allows us to purchase an ABI Avent DNA sequencer for this grant.

ABCA1 and the molecular physiology of defective cellular cholesterol efflux.

Objectives And Hypothesis. In the past 10 years, we have investigated genetic lipoprotein disorders in patients with premature coronary artery disease. We have focused our attention on disorders of low HDL cholesterol. Under grant MRC 12884 (1995-8), we have described the clinical and cellular defect in Familial HDL Deficiency (FHD). Under the term of grant MRC 15042 (1998-01), and under a collaboration with Dr. M. Hayden (UBC) we identified the ABCA1 gene as the cause of FHD and Tangier Disease. The aims of this grant renewal application is to continue our work on the genetics of HDL deficiency states. We propose to investigate the cellular physiology of ABCA1-mediated cellular cholesterol efflux and examine the following hypothesis:

1. ABCA1 gene is regulated by cholesterol and hydroxysterols in fibroblasts.

2. ABCA1-induced cellular cholesterol efflux is mediated by a dual pathway of phospholipid hydrolysis, and by protein phosphorylation (via PKC and PKA pathways).

Specific mutations of ABCA1 impair apo AI-ABCA1 interaction, PKC activation and cellular cholesterol efflux mechanisms.

Severe HDL deficiency is genetically heterogeneous.

Under hypothesis 1, we will explore the following: a) ABCA1 is regulated by free cholesterol in fibroblasts; b) ABCA1 is regulated by hydroxysterols in fibroblasts; c) Inhibition of the LxR/RxR pathway by a DNA sense decoy strategy does not impair cholesterol-mediated ABCA1 mRNA increase; d) ABCA1 gene expression is not regulated by cAMP in fibroblasts and e) ABCA1 gene expression is differentially regulated in fibroblasts and macrophages. The rationale for these studies lies in the observation that cellular free cholesterol and oxysterols are the main regulators of ABCA1 mRNA and protein levels, at least in macrophages and fibroblasts. cAMP regulates ABCA1 in macrophages but our preliminary observations suggest that this is not the case in fibroblasts. Our data indicates that cholesterol up-regulates ABCA1 gene expression (increases in cellular cholesterol concentrations usually decreases transcription of genes involved in cholesterol homeostasis). Understanding ABCA1 gene regulation may lead to modulation of its expression.

In the second hypothesis, we will examine the dual role of PKC activation and phosphatidic acid in mediating cellular cholesterol efflux. We propose to verify the following hypothesis: a) Apo AI–cell interaction lead to increased membrane bound PKC; b) PKC activation and PKA leads to increased cellular cholesterol efflux; c) Cyclic AMP regulates cellular cholesterol efflux in fibroblasts. d) The phosphatidic acid pathway is a key regulator of cellular cholesterol efflux and d) Protein phosphatase inhibitors modulate cholesterol efflux.

The rationale for these experiments stems from our observation that PKC and phosphatidic acid are required to promote cellular cholesterol efflux. Previous work by Walter et al. suggests that the generation of phosphatidic acid is impaired in Tangier disease. We now propose a model to reconcile our observations and that of others. We will also test the hypothesis that ABCA1 phosphorylation is a key modulator of its activity and that inhibition of protein phosphatases leads to an increase in cellular cholesterol efflux.

In the third hypothesis, we will study structure-function relationship between our naturally occuring ABCA1 mutants (n=13 different mutations) on the postulated roles of ABCA1. ABCA1 appears to function as a ligand for apo AI but not HDL3. We will test the hypothesis that mutations at the ABCA1 gene locus in some of our patients is associated with reduced apo AI binding, reduced PKC activation in the plasma membrane, reduced PA generation and decreased efflux.

Finally, we will continue our efforts to identify novel forms of HDL deficiency by extensive family studies.

This study is CIHR funded (2001-2006) and has been underway since the identification of the ABCA1 gene in 1999.