We have studied the genetic basis of LPL deficiency in a 62-year-old black male with undetectable pre- and post-heparin plasma LPL mass and activity, DNA sequence analysis of the patient's LPL cDNA and gene as well as digestion with Bcl I and Asu I revealed that the proband is a homozygote for two separate gene defects.
A compound heterozygote for lipoprotein lipase deficiency, Val69-->Leu and Gly188-->Glu: correlation between in vitro LPL activity and clinical expression.
A naturally occurring mutation at the second base of codon asparagine 43 in the proposed N-linked glycosylation site of human lipoprotein lipase: in vivo evidence that asparagine 43 is essential for catalysis and secretion.
In vitro mutagenesis revealed that the Ser172-->Cys mutation caused a mutant LPL protein that had residual activity higher than that seen in all eight other missense mutations in patients with LPL deficiency identified in our laboratory.
We conclude: (a) diabetic carriers of dysfunctional LPL alleles are at risk for severe lipemia; and (b) the physiologic defects in NIDDM may be additive or synergistic with heterozygous LPL deficiency.
A novel missense mutation in the gene for lipoprotein lipase resulting in a highly conservative amino acid substitution (Asp180-->Glu) causes familial chylomicronemia (type I hyperlipoproteinemia).
Two naturally occurring mutations at the first and second bases of codon aspartic acid 156 in the proposed catalytic triad of human lipoprotein lipase. In vivo evidence that aspartic acid 156 is essential for catalysis.
We have previously reported two common lipoprotein lipase (LPL) gene mutations underlying LPL deficiency in the majority of 37 French Canadians (Monsalve et al., 1990.J. Clin.Invest.86: 728-734; Ma et al., 1991.N. Engl.J. Med.324: 1761-1766).
To understand the molecular basis of LPL deficiency, two siblings with drastically reduced postheparin plasma lipolytic activities were selected for analysis of their LPL gene.
Amino acid substitution (Ile194----Thr) in exon 5 of the lipoprotein lipase gene causes lipoprotein lipase deficiency in three unrelated probands. Support for a multicentric origin.
Studies of site-directed in vitro mutagenesis have confirmed that this mutation generates inactive lipoprotein lipase and is the cause of lipoprotein lipase deficiency.
The mutant LPLs, Asp156----Gly and Asp156----Gly/Ser447----Ter, were devoid of enzyme activity, indicating that the Asp156----Gly mutation is the underlying defect for the LPL deficiency in the two patients.