Browsing by Author "Etxebarria, Aitor"
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- Characterization of the First PCSK9 Gain of Function HomozygotePublication . Alves, Ana Catarina; Etxebarria, Aitor; Medeiros, Ana Margarida; Benito-Vicente, Asier; Thedrez, Aurélie; Passard, Maxime; Croyal, Mikaël; Martin, Cesar; Lambert, Gilles; Bourbon, MafaldaGain of function (GOF) mutations in proprotein convertase subtilisin kexin type 9 (PCSK9) are a rare cause of familial hypercholesterolemia (FH). We identified a child with a clinical diagnosis of FH with 2 novel putative PCSK9 GOF missense variants (p.[(Ala62Asp)]; [(Pro467Ala)]), and no mutation in the low-density lipoprotein (LDL) receptor (LDLR) or in apolipoprotein B100 (APOB) genes. The proband was referred to the Portuguese FH Study (1) at age 11 and presented a total cholesterol of 316 mg/dl and low-density lipoprotein cholesterol (LDL-C) of 234 mg/dl on a strict diet. The phenotype presented by all PCSK9 heterozygous carriers within this large pedigree is similar to APOB heterozygous carriers (LDL-C, 198.75 ± 14.98 mg/dl vs. LDL-C, 211.57 ± 42.02 mg/dl; p = 0.227) but significantly different than heterozygous LDLR carriers (LDL-C, 198.75 ± 14.98 mg/dl vs. LDL-C, 230.63 ± 76.50 mg/dl; p = 0.012) when comparing the relatives’ phenotype in our cohort.
- Novel functional APOB mutations outside LDL-binding region causing familial hypercholesterolaemiaPublication . Alves, Ana Catarina; Etxebarria, Aitor; Soutar, Anne Katherine; Martin, Cesar; Bourbon, Mafalda
- Novel functional APOB mutations outside LDL-binding region causing familial hypercholesterolaemiaPublication . Alves, Ana Catarina; Etxebarria, Aitor; Soutar, Anne Katherine; Martin, Cesar; Bourbon, MafaldaFamilial hypercholesterolaemia (FH) is characterized by increased circulating low-density lipoprotein (LDL) cholesterol leading to premature atherosclerosis and coronary heart disease. Although FH is usually caused by mutations in LDLR, mutations in APOB and PCSK9 also cause FH but only a few mutations have been reported, APOB p.R3527Q being the most common. However, 30-80% of clinical FH patients do not present an identifiable mutation in any of the described genes. To identify the genetic cause of the hypercholesterolaemia in 65 patients without mutations in LDLR, PCSK9 or in fragments of exon 26 and 29 of APOB currently analysed, we performed whole sequencing of APOB by pyrosequencing. A total of 10 putative mutations in APOB were identified. Flow cytometry with fluorescently labelled LDL from patients and relatives showed that p.Arg1164Thr (exon 22) and p.Gln4494del (exon 29) presented a 40% decrease in internalization in lymphocytes and HepG2 cells, very similar to APOB3527. The proliferation assays with U937 cells showed reduced growth for both cases. The variant p.Tyr1247Cys was found to be neutral and other three alterations were considered polymorphisms. Our results emphasize the need to study the whole APOB in routine protocols to improve patient identification and cardiovascular risk assessment.