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ABSTRACT: Monogenic hypobetalipoproteinemias include three disorders: abetalipoproteinemia (ABL) and chylomicron retention disease (CMRD) with recessive transmission and familial hypobetalipoproteinemia (FHBL) with dominant transmission. We investigated three unrelated Tunisian children born from consanguineous marriages, presenting hypobetalipoproteinemia associated with chronic diarrhea and retarded growth. Proband HBL-108 had a moderate hypobetalipoproteinemia, apparently transmitted as dominant trait, suggesting the diagnosis of FHBL. However, she had no mutations in FHBL candidate genes (APOB, PCSK9 and ANGPTL3). The analysis of MTTP gene was also negative, whereas SAR1B gene resequencing showed that the patient was homozygous for a novel mutation (c.184G>A), resulting in an amino acid substitution (p.Glu62Lys), located in a conserved region of Sar1b protein. In the HBL-103 and HBL-148 probands, the severity of hypobetalipoproteinemia and its recessive transmission suggested the diagnosis of ABL. The MTTP gene resequencing showed that probands HBL-103 and HBL-148 were homozygous for a nucleotide substitution in the donor splice site of intron 9 (c.1236+2T>G) and intron 16 (c.2342+1G>A) respectively. Both mutations were predicted in silico to abolish the function of the splice site. In vitro functional assay with splicing mutation reporter MTTP minigenes showed that the intron 9 mutation caused the skipping of exon 9, while the intron 16 mutation caused a partial retention of this intron in the mature mRNA. The predicted translation products of these mRNAs are non-functional truncated proteins. The diagnosis of ABL and CMRD should be considered in children born from consanguineous parents, presenting chronic diarrhea associated with hypobetalipoproteinemia.
Gene 10/2012; · 2.34 Impact Factor
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Paola Conca,
Silvana Pileggi,
Sara Simonelli,
Emanuela Boer,
Giuliano Boscutti,
Lucia Magnolo, Patrizia Tarugi,
Silvana Penco,
Guido Franceschini,
Laura Calabresi,
Monica Gomaraschi
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ABSTRACT: Lecithin:cholesterol acyltransferase (LCAT) is responsible for cholesterol esterification in plasma. Mutations of LCAT gene cause familial LCAT deficiency, a metabolic disorder characterized by hypoalphalipoproteinemia. Apolipoprotein B (apoB) is the main protein component of very-low-density lipoproteins and low-density lipoprotein (LDL). Mutations of APOB gene cause familial hypobetalipoproteinemia, a codominant disorder characterized by low plasma levels of LDL cholesterol and apoB.
This was a genetic and biochemical analysis of an Italian kindred with hypobetalipoproteinemia whose proband presented with hypoalphalipoproteinemia and severe chronic kidney disease.
Plasma lipids and apolipoproteins, cholesterol esterification, and high-density lipoprotein (HDL) subclass distribution were analyzed. LCAT and APOB genes were sequenced.
The proband had severe impairment of plasma cholesterol esterification and high preβ-HDL content. He was heterozygote for the novel LCAT P406L variant, as were two other family members. The proband's wife and children presented with familial hypobetalipoproteinemia and were heterozygotes for the novel apoB H1401R variant. Cholesterol esterification rate of apoB H1401R carriers was reduced, likely attributable to the low amount of circulating LDL. After renal transplantation, proband's lipid profile, HDL subclass distribution, and plasma cholesterol esterification were almost at normal levels, suggesting a mild contribution of the LCAT P406L variant to his pretransplantation severe hypoalphalipoproteinemia and impairment of plasma cholesterol esterification.
LCAT P406L variant had a mild effect on lipid profile, HDL subclass distribution, and plasma cholesterol esterification. ApoB H1401R variant was identified as possible cause of familial hypobetalipoproteinemia and resulted in a reduction of cholesterol esterification rate.
Journal of Clinical Lipidology 05/2012; 6(3):244-50. · 1.58 Impact Factor
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Davide Noto,
Angelo B Cefalù,
Vincenza Valenti,
Francesca Fayer,
Elisa Pinotti,
Mariangela Ditta,
Rossella Spina,
Giovanni Vigna,
Pin Yue,
Sekar Kathiresan, Patrizia Tarugi,
Maurizio R Averna
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ABSTRACT: Mutations of the ANGPTL3 gene have been associated with a novel form of primary hypobetalipoproteinemia, the combined hypolipidemia (cHLP), characterized by low total cholesterol and low HDL-cholesterol levels. The aim of this work is to define the role of ANGPTL3 gene as determinant of the combined hypolipidemia phenotype in 2 large cohorts of 913 among American and Italian subjects with primary hypobetalipoproteinemia (total cholesterol<5th percentile).
The combined hypolipidemia cut-offs were chosen according to total cholesterol and HDL-cholesterol levels reported in the ANGPTL3 kindred described to date: total cholesterol levels, <2nd percentile and HDL-cholesterol, levels<2nd decile. Seventy-eight subjects with combined hypolipidemia were analyzed for ANGPTL3 and APOB genes. We identified nonsense and/or missense mutations in ANGPTL3 gene in 8 subjects; no mutations of the APOB gene were found. Mutated ANGPTL3 homozygous/compound heterozygous subjects showed a more severe biochemical phenotype compared to heterozygous or ANGPTL3 negative subjects, although ANGPTL3 heterozygotes did not differ from ANGPTL3 negative subjects.
These results demonstrated that in a cohort of subjects with severe primary hypobetalipoproteinemia the prevalence of ANGPTL3 gene mutations responsible for a combined hypolipidemia phenotype is about 10%, whereas mutations of APOB gene are absent.
Arteriosclerosis Thrombosis and Vascular Biology 03/2012; 32(3):805-9. · 6.37 Impact Factor
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ABSTRACT: Hyperalphalipoproteinemia, as observed in patients who are either homozygous or heterozygous for cholesteryl ester transfer protein (CETP) deficiency, has been shown to be associated with striking changes in apolipoprotein size distribution, namely, of high-density lipoprotein (HDL) and HDL-like particles. We compared the effect of varying degrees of CETP activity on the HDL apolipoprotein profile in Caucasian CETP-deficient subjects and following pharmacological decrease in CETP activity, using Size Exclusion Chromatography followed by Reverse Phase Protein Array (SEC RPA). The main HDL-associated apolipoproteins (Apo), i.e. ApoA-I, ApoA-II, ApoC-I, and ApoC-III, co-eluted with the HDL peak. The presence of a HDL-like peak migrating between the ApoB-LDL and ApoA-I-HDL was identified in a Caucasian patient with homozygosity for a point mutation in exon 2 of the CETP gene (c.109 C > T) resulting in a premature termination codon (R37X) and complete CETP deficiency. This HDL-like peak was not observed either in healthy volunteers treated with the CETP modulator dalcetrapib, patients heterozygous for the same mutation, or in patients heterozygous with G165X mutations. SEC RPA offers the possibility to investigate the distribution of a large number of apolipoproteins simultaneously under non-denaturing separation in normal and dyslipidemic subjects. This is only limited by the availability of antibodies against specific apolipoproteins to be investigated.
Current Vascular Pharmacology 02/2012; 10(4):422-31. · 2.90 Impact Factor
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Livia Pisciotta,
Elda Favari,
Lucia Magnolo,
Sara Simonelli,
Maria Pia Adorni,
Raffaella Sallo,
Tatiana Fancello,
Ivana Zavaroni,
Diego Ardigò,
Franco Bernini,
Laura Calabresi,
Guido Franceschini, Patrizia Tarugi,
Sebastiano Calandra,
Stefano Bertolini
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ABSTRACT: Angiopoietin-like protein 3 (ANGPTL3) affects lipid metabolism by inhibiting the activity of lipoprotein and endothelial lipases. Angptl3 knockout mice have marked hypolipidemia, and heterozygous carriers of ANGPLT3, loss-of-function mutations were found among individuals in the lowest quartile of plasma triglycerides in population studies. Recently, 4 related individuals with primary hypolipidemia were found to be compound heterozygotes for ANGPTL3 loss-of-function mutations.
We resequenced ANGPTL3 in 4 members of 3 kindreds originally identified for very low levels of low-density lipoprotein cholesterol and high-density lipoprotein cholesterol (0.97±0.16 and 0.56±0.20 mmol/L, respectively) in whom no mutations of known candidate genes for monogenic hypobetalipoproteinemia and hypoalphalipoproteinemia had been detected. These subjects were found to be homozygous or compound heterozygous for ANGPTL3 loss-of-function mutations (p.G400VfsX5, p.I19LfsX22/p.N147X) associated with the absence of ANGPTL3 in plasma. They had reduced plasma levels of triglyceride-containing lipoproteins and of HDL particles that contained only apolipoprotein A-I and pre-β-high-density lipoprotein. In addition, their apolipoprotein B-depleted sera had a reduced capacity to promote cell cholesterol efflux through the various pathways (ABCA1-, SR-BI-, and ABCG1-mediated efflux); however, these subjects had no clinical evidence of accelerated atherosclerosis. Heterozygous carriers of the ANGPTL3 mutations had low plasma ANGPTL3 and moderately reduced low-density lipoprotein cholesterol (2.52±0.38 mmol/L) but normal plasma high-density lipoprotein cholesterol.
Complete ANGPTL3 deficiency caused by loss-of-function mutations of ANGPTL3 is associated with a recessive hypolipidemia characterized by a reduction of apolipoprotein B and apolipoprotein A-I-containing lipoproteins, changes in subclasses of high-density lipoprotein, and reduced cholesterol efflux potential of serum. Partial ANGPTL3 deficiency is associated only with a moderate reduction of low-density lipoprotein.
Circulation Cardiovascular Genetics 11/2011; 5(1):42-50. · 6.11 Impact Factor
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ABSTRACT: This review integrates historical biochemical and modern genetic findings that underpin our understanding of the low-density lipoprotein (LDL) dyslipidemias that bear on human disease. These range from life-threatening conditions of infancy through severe coronary heart disease of young adulthood, to indolent disorders of middle- and old-age. We particularly focus on the biological aspects of those gene mutations and variants that impact on sterol absorption and hepatobiliary excretion via specific membrane transporter systems (NPC1L1, ABCG5/8); the incorporation of dietary sterols (MTP) and of de novo synthesized lipids (HMGCR, TRIB1) into apoB-containing lipoproteins (APOB) and their release into the circulation (ANGPTL3, SARA2, SORT1); and receptor-mediated uptake of LDL and of intestinal and hepatic-derived lipoprotein remnants (LDLR, APOB, APOE, LDLRAP1, PCSK9, IDOL). The insights gained from integrating the wealth of genetic data with biological processes have important implications for the classification of clinical and presymptomatic diagnoses of traditional LDL dyslipidemias, sitosterolemia, and newly emerging phenotypes, as well as their management through both nutritional and pharmaceutical means.
The Journal of Lipid Research 08/2011; 52(11):1885-926. · 5.56 Impact Factor
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ABSTRACT: Primary hypobetalipoproteinemia (pHBL) is characterized by plasma cholesterol levels <5th percentile of a population distribution. Plasma non-cholesterol sterols (NCS) are markers of cholesterol liver synthesis and intestinal absorption. Plasma NCS were measured in 111 pHBL subjects, 108 low cholesterol (LC) and 253 normal cholesterol (NC) controls to gain information on cholesterol metabolism in pHBL, and to assess whether NCS measurements may aid in distinguishing pHBL from LC controls. pHBL subjects compared with LC controls were characterized by increased cholesterol absorption (campesterol/TC) while the synthesis (lathosterol/TC) was not increased. The analysis of pHBL subjects divided by gene defect showed a high campesterol/TC ratio in familial HBL (FHBL) carriers of apolipoproteinB (ApoB) truncations longer than ApoB48 and in FHBL without known gene defect ("not linked"). One not linked kindred was characterized by an increase of the 7-dehydrocholesterol/latho ratio. In a discriminant analysis plasma NCS did not improve the power of TC levels to distinguish FHBL from LC controls. In conclusion, increased cholesterol absorption was found in FHBL subjects harbouring truncations of ApoB>ApoB48, and FHBL harbouring as yet unknown molecular defects. Not linked FHBL kindred are not homogeneous in terms of plasma NCS levels. NCS cannot replace genetic HBL analysis.
Atherosclerosis 06/2011; 216(2):409-13. · 3.79 Impact Factor
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ABSTRACT: Hypobetalipoproteinemias (HBL) represent a heterogeneous group of disorders characterized by reduced plasma levels of total cholesterol (TC), low density lipoprotein-cholesterol (LDL-C) and apolipoprotein B (apoB) below the 5th percentile of the distribution in the population. HBL are defined as primary or secondary according to the underlying causes. Primary monogenic HBL are caused by mutations in several known genes (APOB, PCSK9, MTP, SARA2) or mutations in genes not yet identified. Familial hypobetalipoproteinemia (FHBL) is the most frequent monogenic form of HBL with a dominant mode of inheritance. It may be due to loss-of-function mutations in APOB or, less frequently, in PCSK9 genes. The rare recessive forms of primary monogenic HBL are represented by abetalipoproteinemia (ABL) and chylomicron retention disease (CMRD) due to mutations in MTP and SARA2 genes, respectively. The clinical phenotype of heterozygous FHBL is usually mild, being frequently characterized by fatty liver. The clinical phenotype of homozygous FHBL, ABL, and CMRD is usually severe being characterized by intestinal lipid malabsorption and fat-soluble vitamin deficiency. Secondary HBL are due to several nongenetic factors such as diet, drugs, and disease-related conditions. The aim of this review is to discuss the biochemistry, genetics, and clinical spectrum of HBL and to provide a clinical and laboratory diagnostic algorithm.
Advances in clinical chemistry 01/2011; 54:81-107. · 3.20 Impact Factor
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ABSTRACT: To review recent publications concerning the functional assessment on pre-mRNA splicing of genomic variants found in some monogenic dyslipidemias. Examples are derived from familial hypercholesterolemia, familial HDL deficiency/Tangier disease and familial hypobetalipoproteinemia.
About 5-10% of genomic variants found in familial hypercholesterolemia, FHD/Tangier disease and familial hypobetalipoproteinemia are located in the introns of the candidate genes and are classified as splicing mutations. Although variants affecting highly conserved GT/AG dinucleotides at the splice sites are likely to be pathogenic, it is difficult to predict the effects of variants located deep in the introns. Algorithms were developed to predict the effect of these variants and to provide the rationale for functional studies. Combined in-silico and wet bench analysis revealed that some intronic variants classified as pathogenic have no effect, whereas others generated abnormal transcripts. Nucleotide substitutions at the 5' and the 3' of exons might change the splice site consensus sequence, causing splicing defects. Rare silent mutations were identified which create new splice sites within exons, with the consequent production of abnormal transcripts.
Intronic variants, even if located deep in introns, as well as exonic variants could affect splicing with the formation of abnormal transcripts encoding structurally abnormal proteins.
Current opinion in lipidology 12/2010; 22(2):93-9. · 6.13 Impact Factor
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Shumei Zhong,
Antonia Lucia Magnolo,
Meenakshi Sundaram,
Hu Zhou,
Erik F Yao,
Enza Di Leo,
Paola Loria,
Shuai Wang,
Michelle Bamji-Mirza,
Lisheng Wang,
C Jamie McKnight,
Daniel Figeys,
Yuwei Wang, Patrizia Tarugi,
Zemin Yao
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ABSTRACT: Five nontruncating missense APOB mutations, namely A31P, G275S, L324M, G912D, and G945S, were identified in heterozygous carriers of familial hypobetalipoproteinemia (FHBL) in the Italian population. To test that the FHBL phenotype was a result of impaired hepatic secretion of mutant apoB proteins, we performed transfection studies using McA-RH7777 cells stably expressing wild type or mutant forms of human apolipoprotein B-48 (apoB-48). All mutant proteins displayed varied impairment in secretion, with G912D the least affected and A31P barely secreted. Although some A31P was degraded by proteasomes, a significant proportion of it (although inappropriately glycosylated) escaped endoplasmic reticulum (ER) quality control and presented in the Golgi compartment. Degradation of the post-ER A31P was achieved by autophagy. Expression of A31P also decreased secretion of endogenous apoB and triglycerides, yet the impaired lipoprotein secretion did not lead to lipid accumulation in the cells or ER stress. Rather, expression of genes involved in lipogenesis was down-regulated, including liver X receptor alpha, sterol regulator element-binding protein 1c, fatty acid synthase, acetyl-CoA carboxylase 1, stearoyl-CoA desaturase 1, and lipin-1. These results suggest that feedback inhibition of hepatic lipogenesis in conjunction with post-ER degradation of misfolded apoB proteins can contribute to reduce fat accumulation in the FHBL liver.
Journal of Biological Chemistry 02/2010; 285(9):6453-64. · 4.77 Impact Factor
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Shumei Zhong,
Antonia Lucia Magnolo,
Meenakshi Sundaram,
Hu Zhou,
Erik F. Yao,
Enza Di Leo,
Paola Loria,
Shuai Wang,
Michelle Bamji-Mirza,
Lisheng Wang,
C. Jamie McKnight,
Daniel Figeys,
Yuwei Wang, Patrizia Tarugi,
Zemin Yao
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ABSTRACT: Five nontruncating missense APOB mutations, namely A31P, G275S, L324M, G912D, and G945S, were identified in heterozygous carriers of familial hypobetalipoproteinemia
(FHBL) in the Italian population. To test that the FHBL phenotype was a result of impaired hepatic secretion of mutant apoB
proteins, we performed transfection studies using McA-RH7777 cells stably expressing wild type or mutant forms of human apolipoprotein
B-48 (apoB-48). All mutant proteins displayed varied impairment in secretion, with G912D the least affected and A31P barely
secreted. Although some A31P was degraded by proteasomes, a significant proportion of it (although inappropriately glycosylated)
escaped endoplasmic reticulum (ER) quality control and presented in the Golgi compartment. Degradation of the post-ER A31P
was achieved by autophagy. Expression of A31P also decreased secretion of endogenous apoB and triglycerides, yet the impaired
lipoprotein secretion did not lead to lipid accumulation in the cells or ER stress. Rather, expression of genes involved in
lipogenesis was down-regulated, including liver X receptor α, sterol regulator element-binding protein 1c, fatty acid synthase,
acetyl-CoA carboxylase 1, stearoyl-CoA desaturase 1, and lipin-1. These results suggest that feedback inhibition of hepatic
lipogenesis in conjunction with post-ER degradation of misfolded apoB proteins can contribute to reduce fat accumulation in
the FHBL liver.
Journal of Biological Chemistry 02/2010; 285(9):6453-6464. · 4.77 Impact Factor
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ABSTRACT: Pseudoxanthoma Elasticum (PXE), an autosomal recessive disease due to mutations in ABCC6 gene, is characterised by fragmentation of elastic fibres with involvement of the cardiovascular system. We investigated a 60-year-old female with angina pectoris found to have PXE, associated with elevated plasma LDL-C suspected to be due to autosomal-co-dominant hypercholesterolemia.
ABCC6, LDLR, PCSK9 and exon 26 of APOB genes were re-sequenced. Cardiovascular involvement was assessed by coronary angiography, single-photon emission computed tomography (SPECT) and ultrasound examination.
The patient was a compound heterozygous for two ABCC6 mutations (p.S317R and p.R1141X) and heterozygous for a novel LDLR mutation (p.R574H). She had severe coronary stenosis and calcification of the arteries of the lower limbs. Treatment with ezetimibe/simvastatin 10/60mg/day, maintained over a 4.5-year period, reduced of LDL-C and the myocardial ischemic area. In PXE patients LDL-lowering treatment might contribute to delay macrovascular complications.
Atherosclerosis 11/2009; 210(1):173-6. · 3.79 Impact Factor
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Angelo B Cefalù,
Davide Noto,
Maria Luisa Arpi,
Fen Yin,
Rossella Spina,
Hannele Hilden,
Carlo M Barbagallo,
Antonio Carroccio, Patrizia Tarugi,
Sebastiano Squatrito,
Riccardo Vigneri,
Marja-Riitta Taskinen,
Miklós Péterfy,
Maurizio R Averna
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ABSTRACT: Lipase maturation factor 1 (LMF1) gene is a novel candidate gene in severe hypertriglyceridemia. Lmf1 is involved in the maturation of lipoprotein lipase (LPL) and hepatic lipase in endoplasmic reticulum. To date only one patient with severe hypertriglyceridemia and related disorders was found to be homozygous for a nonsense mutation in LMF1 gene (Y439X).
The objective of the study was to investigate LMF1 gene in hypertriglyceridemic patients in whom mutations in LPL, APOC2, and APOA5 genes had been excluded.
The resequencing of LMF1 gene led to the discovery of a novel homozygous nonsense mutation in one patient with severe hypertriglyceridemia and recurrent episodes of pancreatitis. The mutation causes a G>A substitution in exon 9 (c.1395G>A), leading to a premature stop codon (W464X). LPL activity and mass were reduced by 76 and 50%, respectively, compared with normolipidemic controls. The proband over the years has shown a good response to treatment. The proband's son, heterozygous for the W464X, shows normal plasma triglyceride levels.
We identified the second novel pathogenic mutation in LMF1 gene in a patient with severe hypertriglyceridemia. LPL deficiency in our patient was milder than in the carrier of the Y439X previously described.
The Journal of clinical endocrinology and metabolism 10/2009; 94(11):4584-90. · 6.50 Impact Factor
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Bertrand Cariou,
Khadija Ouguerram,
Yassine Zaïr,
Raphael Guerois,
Cédric Langhi,
Sanae Kourimate,
Isabelle Benoit,
Cédric Le May,
Constance Gayet,
Khaldia Belabbas,
Fabienne Dufernez,
Maud Chétiveaux, Patrizia Tarugi,
Michel Krempf,
Pascale Benlian,
Philippe Costet
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ABSTRACT: Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a central player in the regulation of cholesterol homeostasis, increasing the low-density lipoprotein (LDL) receptor degradation. Our study aimed at exploring the pathogenic consequences in vivo and in vitro of a PCSK9 prodomain mutation found in a family with hypobetalipoproteinemia (FHBL).
A white 49-year-old diabetic man had profound FBHL (LDLC: 16 mg/dL) whereas his daughter and sister displayed a milder phenotype (LDLC 44 mg/dL and 57 mg/dL, respectively), all otherwise healthy with a normal liver function. A monoallelic PCSK9 double-mutant R104C/V114A cosegregated with FBHL, with no mutation found at other FHBL-causing loci. A dose-effect was also found in FBHL relatives for plasma APOB and PCSK9 (very-low to undetectable in proband, approximately 50% decreased in sister and daughter) and LDL catabolic rate (256% and 88% increased in proband and daughter). Transient transfection in hepatocytes showed severely impaired processing and secretion of the double mutant which acted as a dominant negative over secretion of wild-type PCSK9.
These results show that heterozygous PCSK9 missense mutations may associate with profound hypobetalipoproteinemia and constitute the first direct evidence in human that decrease of plasma LDLC concentrations associated to PCSK9 LOF mutations are attributable to an increased clearance rate of LDL.
Arteriosclerosis Thrombosis and Vascular Biology 09/2009; 29(12):2191-7. · 6.37 Impact Factor
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Tatiana Fancello,
Andrea Dardis,
Camillo Rosano, Patrizia Tarugi,
Barbara Tappino,
Stefania Zampieri,
Elisa Pinotti,
Fabio Corsolini,
Simona Fecarotta,
Adele D'Amico,
Maja Di Rocco,
Graziella Uziel,
Sebastiano Calandra,
Bruno Bembi,
Mirella Filocamo
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ABSTRACT: Niemann-Pick C, the autosomal recessive neuro-visceral disease resulting from a failure of cholesterol trafficking within the endosomal-lysosomal pathway, is due to mutations in NPC1 or NPC2 genes. We characterized 34 unrelated patients including 32 patients with mutations in NPC1 gene and two patients in NPC2 gene. Overall, 33 distinct genotypes were encountered. Among the 21 unpublished NPC1 alleles, 15 were due to point mutations resulting in 13 codon replacements (p.C100S, p.P237L, p.R389L, p.L472H, p.Y634C, p.S636F, p.V780G, p.Q921P, p.Y1019C, p.R1077Q, p.L1102F, p.A1187V, and p.L1191F) and in two premature stop codons (p.R934X and p.Q447X); a new mutant carried two in cis mutations, p.[L648H;M1142T] and four other NPC1 alleles were small deletions/insertions leading both to frame shifts and premature protein truncations (p.C31WfsX26, p.F284LfsX26, p.E1188fsX54, and p.T1205NfsX53). Finally, the new intronic c.464-2A>C change at the 3' acceptor splice site of intron 4 affected NPC1 messenger RNA processing. We also found a new NPC2 mutant caused by a change of the first codon (p.M1L). The novel missense mutations were further investigated by two bioinformatics approaches. Panther proein classification system computationally predicted the detrimental effect of all new missense mutations occurring at evolutionary conserved positions. The other bioinformatics approach was based on prediction of structural alterations induced by missense mutations on the NPC1 atomic models. The in silico analysis predicted protein malfunctioning and/or local folding alteration for most missense mutations. Moreover, the effects of the missense mutations (p.Y634C, p.S636F, p.L648H, and p.V780G) affecting the sterol-sensing domain (SSD) were evaluated by docking simulation between the atomic coordinates of SSD model and cholesterol.
Neurogenetics 02/2009; 10(3):229-39. · 3.35 Impact Factor
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Laura Calabresi,
Peter Nilsson,
Elisa Pinotti,
Monica Gomaraschi,
Elda Favari,
Maria Pia Adorni,
Franco Bernini,
Cesare R Sirtori,
Sebastiano Calandra,
Guido Franceschini, Patrizia Tarugi
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ABSTRACT: To analyze the cholesteryl ester transfer protein (CETP) gene and the plasma HDL phenotype in a Caucasian subject with extremely elevated plasma high density lipoprotein-cholesterol (HDL-C).
The proband, a 63-year-old male of Swedish ancestry with elevated HDL-C (208mg/dl) and apoA-I (and 272mg/dl), was found to be homozygous for a point mutation in exon 2 of CETP gene (c.109 C>T) resulting in a premature termination codon (R37X). Plasma CETP mass and activity were undetectable. Plasma HDL were characterized by predominance of large HDL with enhanced prebeta-HDL content. The proband's sons, heterozygotes for the mutation, had reduced plasma CETP activity and moderately elevated HDL-C. Serum of CETP deficient subjects showed a normal or enhanced cholesterol efflux capacity via ABCG1/SR-BI; cholesterol efflux via ABCA1 and macrophage cholesterol removal were lower than normal. The proband was healthy and had no atherosclerotic plaques in carotid or femoral arteries.
Complete CETP deficiency caused by mutations in CETP gene is exceedingly rare in Caucasians; the description of this single case indicates that CETP deficiency does not predispose to atherosclerosis in the absence of major cardiovascular risk factors.
Atherosclerosis 01/2009; 205(2):506-11. · 3.79 Impact Factor
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Enza Di Leo,
Lucia Magnolo,
Elisa Pinotti,
Scipione Martini,
Irene Cortella,
Nicola Vitturi,
Claudio Rabacchi,
Alessia Wunsch,
Francesco Pucci,
Stefano Bertolini,
Sebastiano Calandra, Patrizia Tarugi
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ABSTRACT: Familial hypobetalipoproteinemia (FHBL) is a co-dominant disorder characterized by reduced plasma levels of low density lipoprotein cholesterol (LDL-C) and its protein constituent apolipoprotein B (apoB), which may be due to mutations in APOB gene, mostly located in the coding region of this gene. We report two novel APOB gene mutations involving the acceptor splice site of intron 11 (c.1471-1G>A) and of intron 23 (c.3697-1G>C), respectively, which were identified in two patients with heterozygous FHBL associated with severe fatty liver disease. The effects of these mutations on APOB pre-mRNA splicing were assessed in COS-1 cells expressing the mutant APOB minigenes. The c.1471-1G>A APOB minigene generated two abnormal mRNAs. In one mRNA the entire intron 11 was retained; in the other mRNA exon 11 joined to exon 12, in which the first nucleotide was deleted due to the activation of a novel acceptor splice site. The predicted products of these mRNAs are truncated proteins of 546 and 474 amino acids, designated apoB-12.03 and apoB-10.45, respectively. The c.3697-1G>C APOB minigene generated a single abnormal mRNA in which exon 23 joined to exon 25, with the complete skipping of exon 24. This abnormal mRNA is predicted to encode a truncated protein of 1220 amino acids, designated apoB-26.89. These splice site mutations cause the formation of short truncated apoBs, which are not secreted into the plasma as lipoprotein constituents. This secretion defect is the major cause of severe fatty liver observed in carriers of these mutations.
Molecular Genetics and Metabolism 12/2008; 96(2):66-72. · 3.19 Impact Factor
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Mohamed Najah,
Enza Di Leo,
Jelassi Awatef,
Lucia Magnolo,
Jgurim Imene,
Elisa Pinotti,
Mahjoub Bahri,
Sihem Barsaoui,
Ines Brini,
Moncef Fekih,
Mohamed Naceur Slimane, Patrizia Tarugi
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ABSTRACT: Abetalipoproteinemia (ABL) and Homozygous Familial Hypobetalipoproteinemia (Ho-FHBL) are rare monogenic diseases characterised by very low plasma levels of cholesterol and triglyceride and the absence or a great reduction of apolipoprotein B (apoB)-containing lipoproteins. ABL results from mutations in the MTP gene; Ho-FHBL may be due to mutations in the APOB gene.
We sequenced MTP and APOB genes in three Tunisian children, born from consanguineous marriage, with very low levels of plasma apoB-containing lipoproteins associated with severe intestinal fat malabsorption.
Two of them were found to be homozygous for two novel mutations in intron 5 (c.619-3T>G) and in exon 8 (c.923 G>A) of the MTP gene, respectively. The c.619-3T>G substitution caused the formation of an abnormal mRNA devoid of exon 6, predicted to encode a truncated MTP of 233 amino acids. The c.923 G>A is a nonsense mutation resulting in a truncated MTP protein (p.W308X). The third patient was homozygous for a novel nucleotide deletion (c.2172delT) in exon 15 of APOB gene resulting in the formation of a truncated apoB of 706 amino acids (apoB-15.56).
These mutations are expected to abolish the apoB lipidation and the assembly of apoB-containing lipoproteins in both liver and intestine.
Clinica chimica acta; international journal of clinical chemistry 12/2008; 401(1-2):51-6. · 2.54 Impact Factor
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ABSTRACT: Cholesteryl ester transfer protein (CETP) is a plasma glycoprotein that catalyses the transfer of cholesteryl esters from HDL to the other plasma lipoproteins. Genetic deficiency of CETP is one of the known causes of elevation of plasma HDL-C (primary hyperalphalipoproteinemia, HALP). We sequenced CETP gene in a group of 24 Italian subjects with primary HALP (HDL-C>80 mg/dl) suspected to have CETP deficiency. Two unrelated subjects both coming from the same geographical district, were found to be heterozygous for a nucleotide substitution in exon 6 (c.544C>T) and another subject was found to be heterozygous for a C>T transition in exon 9 (c.802C>T). Both mutations introduce a premature stop codon and are predicted to cause the production of truncated proteins (Q165X and R268X, respectively) devoid of function. The fourth proband was found to carry a T>C substitution in intron 15 (c.1407+2T>C) predicted to abolish the function of the donor splice site. To define the effect of this mutation on CETP pre-mRNA splicing we analysed CETP mRNA in COS-1 cells expressing a CETP minigene harbouring the mutation. The analysis of minigene transcript in COS-1 cells showed that IVS15+2T>C mutation caused the formation of an abnormal mRNA in which exon 14 joins directly to exon 16, predicted to encode a truncated peptide of 435 amino acids. In mutation carriers plasma CETP activity was found to be reduced by 38-60%. These are the first mutations in the CETP gene found in Italian subjects with HALP.
Atherosclerosis 09/2008; 204(1):202-7. · 3.79 Impact Factor
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Current Opinion in Lipidology 05/2008; 19(2):208-11. · 6.09 Impact Factor
