Cloning and gene defects in microsomal triglyceride transfer protein associated with abetalipoproteinaemia.
The microsomal triglyceride transfer protein (MTP), which catalyses the transport of triglyceride, cholesteryl ester and phospholipid between phospholipid surfaces, is a heterodimer composed of the multifunctional protein, protein disulphide isomerase, and a unique large subunit with an apparent M(r) of 88K (refs 1-3). It is isolated as a soluble protein from the lumen of the microsomal fraction of liver and intestine. The large subunit of MTP was not detectable in four unrelated subjects with abetalipoproteinaemia, a rare autosomal recessive disease characterized by a defect in the assembly or secretion of plasma lipoproteins that contain apolipoprotein B (ref. 6). We report here the isolation and sequencing of complementary DNA encoding the large subunit of MTP. A comparison of this sequence to corresponding genomic sequences from two abetalipoproteinaemic subjects revealed a homozygous frameshift mutation in one subject and a homozygous nonsense mutation in the other. The results indicate that a defect in the gene for the large subunit of MTP is the proximal cause of abetalipoproteinaemia in these two subjects, and that MTP is required for the secretion of plasma lipoproteins that contain apolipoprotein B.
Sharp
D
D
Department of Metabolic Diseases, Bristol-Myers Squibb, Princeton, New Jersey 08543-4000.
Blinderman
L
L
Combs
K A
KA
Kienzle
B
B
Ricci
B
B
Wager-Smith
K
K
Gil
C M
CM
Turck
C W
CW
Bouma
M E
ME
Rader
D J
DJ
D000012:Abetalipoproteinemia / Q000235:genetics* / Q000378:metabolism; D000293:Adolescent; D000328:Adult; D000595:Amino Acid Sequence; D000818:Animals; D001055:Apolipoproteins B / Q000378:metabolism; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics*; D002417:Cattle; D002478:Cells, Cultured; D053480:Cholesterol Ester Transfer Proteins; D003001:Cloning, Molecular; D004247:DNA; D004252:DNA Mutational Analysis; D005260:Female; D005347:Fibroblasts; D006023:Glycoproteins; D006801:Humans; D007421:Intestine, Small / Q000378:metabolism; D008074:Lipoproteins / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D016415:Sequence Alignment; D014280:Triglycerides
D001055:Apolipoproteins B; C506642:CETP protein, human; D002352:Carrier Proteins; D053480:Cholesterol Ester Transfer Proteins; D006023:Glycoproteins; D008074:Lipoproteins; D014280:Triglycerides; C106092:microsomal triglyceride transfer protein; D004247:DNA