New rare genetic variants of LMF1 gene identified in severe hypertriglyceridemia

Abstract : Background The LMF1 (lipase maturation factor 1) gene encodes a protein involved in lipoprotein lipase and hepatic lipase maturation. Homozygous mutations in LMF1 leading to severe hypertriglyceridemia (SHTG) are rare in the literature. A few additional rare LMF1 variants have been described with poor functional studies. Objective The aim of this study was to assess the frequency of LMF1 variants in a cohort of 385 patients with SHTG, without homozygous or compound heterozygous deleterious mutations identified in lipoprotein lipase (LPL), apolipoprotein A5 (APOA5), apolipoprotein C2 (APOC2), glycosylphosphatidylinositol-anchored high-density lipoprotein binding protein 1 (GPIHBP1) genes, and to determine their functionality. Methods LMF1 coding variants were screened using denaturing high-performance liquid chromatography followed by direct sequencing. In silico studies of LMF1 variants were performed, followed by in vitro functional studies using human embryonic kidney 293T (HEK-293T) cells cotransfected with vectors encoding human LPL and LMF1 cDNA. LPL activity was measured in cell culture medium after heparin addition using human VLDL-TG as substrate. Results Nineteen nonsynonymous coding LMF1 variants were identified in 65 patients; 10 variants were newly described in SHTG. In vitro, p.Gly172Arg, p.Arg354Trp, p.Arg364Gln, and p.Arg537Trp LMF1 variants decreased LPL activity, and the p.Trp464Ter variant completely abolished LPL activity. We identified a young girl heterozygote for the p.Trp464Ter variant and a homozygote carrier of the p.Gly172Arg variant with a near 50% decreased LPL activity in vitro and in vivo. Conclusion The study confirms the rarity of LMF1 variants in a large cohort of patients with SHTG. LMF1 variants are likely to be involved in multifactorial hyperchylomicronemia. Partial LMF1 defects could be associated with intermittent phenotype as described for p.Gly172Arg homozygous and p.Trp464Ter heterozygous carriers.
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https://hal-univ-bourgogne.archives-ouvertes.fr/hal-01881223
Contributeur : Lnc - Université de Bourgogne <>
Soumis le : mardi 25 septembre 2018 - 15:28:19
Dernière modification le : mercredi 3 avril 2019 - 01:56:38

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Marine Serveaux Dancer, Mathilde Di Filippo, Oriane Marmontel, René Valéro, Maria del Carmen Piombo Rivarola, et al.. New rare genetic variants of LMF1 gene identified in severe hypertriglyceridemia. JOURNAL OF CLINICAL LIPIDOLOGY, 2018, 12 (5), pp.1244-1252. ⟨https://www.sciencedirect.com/science/article/pii/S1933287418302939?via%3Dihub⟩. ⟨10.1016/j.jacl.2018.06.018⟩. ⟨hal-01881223⟩

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