Elevated plasma levels of apolipoprotein B (apo B100) and low density lipoprotein (LDL) are associated with a higher risk for atherosclerotic coronary heart disease, a leading cause of mortality in the industrialized world. Apo B is required for the secretion of very low-density lipoproteins (VLDL) from the liver and is the mandatory protein constituent of both plasma VLDL and LDL. Overproduction of apo B is a major characteristics of familial combined hyperlipidemia (FCHL), a prevalent disease with heterogeneous genetic basis. Genetic studies have shown that plasma apo B levels are controlled by unknown major genes. The investigators hypothesize that plasma apoB levels are controlled, in part by the secretion rate of apo B-containing lipoproteins, which is genetically regulated. To determine the genetic basis of plasma apo B levels, we have chosen to use the human apo B only in the liver. The preliminary studies provided evidence of genetic control of hepatic B-100 secretion resulting in varying plasma human apo B levels in F1 offspring from crosses between a congenic HuBTg and various inbred mouse strains. Further genetic studies in crosses between C57BL/6 and 129/Sv have identified two novel major quantitative trait loci (QTL) (designated apo B regulator loci), which account for a majority of genetic variance of plasma human apo B levels in these crosses. The long-term goal of the proposal is to clone and characterize one of the major apo B regulator genes. This gene will be a novel regulator affecting the pathways involved in the assembly and secretion of apo B-containing lipoproteins and is a strong candidate gene for FCHL. It is also a potential target for therapeutic intervention. The goals will be achieved through the following aims.
Aim 1 : Generation and characterization of partial congenic HuBTg mouse lines containing chromosomal intervals regulating plasma human apo B levels. Specific breeding strategies will be used to generate interval-specific partial congenic lines (i.e., incipient congenics) for fine mapping and biochemical characterization.
Aim 2 : High resolution mapping of the interval containing a major apo B regulator locus using interval-specific incipient congenics. The incipient congenic line with a greater effect on the plasma apo B levels will be selected for fine mapping.
Aim 3 : Identification and characterization of transcripts within the critical interval containing the apo B regulator locus. A BAC contig containing the critical interval will be analyzed and transcripts identified. Allelic variants for the candidate gene will be identified and tested for their functional significance.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
1R01HL062583-01A1
Application #
6130099
Study Section
Metabolism Study Section (MET)
Project Start
2000-04-01
Project End
2004-02-28
Budget Start
2000-04-01
Budget End
2001-02-28
Support Year
1
Fiscal Year
2000
Total Cost
$424,356
Indirect Cost
Name
Columbia University (N.Y.)
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
167204994
City
New York
State
NY
Country
United States
Zip Code
10032
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