Transgenic mice expressing a human apolipoprotein[a] allele.
The most important determinant of plasma levels of Lp[a] are sequence differences at the highly polymorphic apolipoprotein[a] (apo[a]) locus. To define the sequences that mediate the regulation of apo[a] expression, we cloned a 370 kb DNA fragment that included a 130 kb apo[a] gene, and 40 kb 5'- and 200 kb 3'-flanking region from an individual with high plasma levels of Lp[a] using a YAC vector. This genomic clone was used to generate transgenic mice. In the YAC-apo[a] transgenic mouse, apo[a] was only expressed in the liver, as it is in humans. The mean serum level of apo[a] in 4-week-old YAC-apo[a] transgenic mice was 20 mg/dl. In the female mice the levels of apo[a] varied over a 1.5-fold range during the 4-day estrus cycle and the levels correlated directly with serum progesterone levels. The serum levels of apo[a] decreased to almost undetectable level in male mice after puberty and this decrease was reversed by castration. Ingestion of a high-fat diet resulted in a approximately 100-fold fall in hepatic apo[a] mRNA levels and >60-fold decrease in serum apo[a] levels. To delimit the control elements that mediate tissue-specific and sex hormone-responsive apo[a] transcription, we derived a reporter YAC in which 40 kb of 5' flanking sequences from the cloned apo[a] allele were linked to a luciferase reporter gene. Analysis of four independent transgenic lines revealed no hepatic luciferase expression, suggesting that important cis -acting elements located outside the apo[a] 5'-flanking region are necessary for in vivo expression of apo[a].
Acquati
F
F
Department of Molecular Biology, Boehringer Mannheim GmbH, Mannheim, Germany.
Hammer
R
R
Ercoli
B
B
Mooser
V
V
Tao
R
R
Rönicke
V
V
Michalich
A
A
Chiesa
G
G
Taramelli
R
R
Hobbs
H H
HH
Müller
H J
HJ
D000483:Alleles; D000818:Animals; D001054:Apolipoproteins A / Q000235:genetics* / Q000378:metabolism; D002369:Castration; D018244:Chromosomes, Artificial, Yeast / Q000235:genetics; D004041:Dietary Fats / Q000008:administration & dosage; D004971:Estrus; D005260:Female; D005786:Gene Expression Regulation; D005822:Genetic Vectors; D012739:Gonadal Steroid Hormones / Q000502:physiology; D006801:Humans; D008099:Liver / Q000378:metabolism; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D011374:Progesterone / Q000097:blood; D012333:RNA, Messenger / Q000378:metabolism; D012741:Sexual Maturation
D001054:Apolipoproteins A; D004041:Dietary Fats; D012739:Gonadal Steroid Hormones; D012333:RNA, Messenger; D011374:Progesterone