Single, short in-del, and copy number variations detection in monogenic dyslipidemia using a next-generation sequencing strategy.

Optimal molecular diagnosis of primary dyslipidemia is challenging to confirm the diagnosis, test and identify at risk relatives. The aim of this study was to test the application of a single targeted next-generation sequencing (NGS) panel for hypercholesterolemia, hypocholesterolemia, and hypertriglyceridemia molecular diagnosis. NGS workflow based on a custom AmpliSeq panel was designed for sequencing the most prevalent dyslipidemia-causing genes (ANGPTL3, APOA5, APOC2, APOB, GPIHBP1, LDLR, LMF1, LPL, PCSK9) on the Ion PGM Sequencer. One hundred and forty patients without molecular diagnosis were studied. In silico analyses were performed using the NextGENe software and homemade tools for detection of copy number variations (CNV). All mutations were confirmed using appropriate tools. Eighty seven variations and 4 CNV were identified, allowing a molecular diagnosis for 40/116 hypercholesterolemic patients, 5/13 hypocholesterolemic patients, and 2/11, hypertriglyceridemic patients respectively. This workflow allowed the detection of CNV contrary to our previous strategy. Some variations were found in previously unexplored regions providing an added value for genotype-phenotype correlation and familial screening. In conclusion, this new NGS process is an effective mutation detection method and allows better understanding of phenotype. Consequently this assay meets the medical need for individualized diagnosis of dyslipidemia.

[International recommandations on physical exercise for pregnant women]. / Activité physique durant la grossesse : point sur les recommandations internationales.

Benefits of physical exercise on the physical and psychological health lead to specifics guidelines during pregnancy. For pregnant women, to take part in aerobics exercise (walking, biking) (i.e. 30 minutes, three times per week at 60-90% of the maximal heart rate) and strength training (i.e. one to two times per week) is recommended. Physical exercise programs during pregnancy have shown benefits for preventing and treating complications pregnancy (e.g. gestational diabetes mellitus, overweight). Benefits of exercise and risks associated with sedentary should be widely diffused among pregnant women and prenatal caregivers.

Modulation of phenotypic expression of APOA5 Q97X and L242P mutations.

OBJECTIVE: To provide phenotypic and functional data in new patients with APOA5 mutations and to identify genetic and metabolic factors influencing their phenotypic expression. METHODS AND RESULTS: By sequencing APOA5 gene in a cohort of 286 hyperchylomicronemic subjects, free of LPL or APOC2 mutations, we identified 4 unrelated carriers of the Q97X mutation (3 heterozygotes and 1 homozygote) and one heterozygote with a new L242P mutation. Postheparin LPL activity level was reduced by about 50% in Q97X heterozygotes and more than 90% in the Q97X homozygote, but was normal in the L242P patient after resolution of hyperchylomicronemia. Plasma apoAV was undetectable in the Q97X homozygote and in the normal range in the L242P and Q97X heterozygous carriers. In Western blot studies, the association of apoAV with plasma lipoproteins was altered in Q97X heterozygous carriers but not in the L242P carrier. Hyperchylomicronemic heterozygotes for both mutations carried an additional APOA5 variant haplotype and/or APOE variant (E2 or E4). Type 2 diabetes or metabolic syndrome were not a major phenotypic determinant. CONCLUSIONS: The L242P mutation was present in a hyperchylomicronemic proband but its causal involvement remains to be established. The Q97X mutation was clearly involved in hyperchylomicronemia with evidence of concomitant altered intravascular lipolysis, and a complete apoAV deficiency in the homozygote. The phenotypic expression variability of APOA5 mutations was mostly influenced by compound heterozygosity with APOA5 variant haplotypes plus additional genetic factors, and in a lesser extent by the metabolic environment.

Acid sphingomyelinase: identification of nine novel mutations among Italian Niemann Pick type B patients and characterization of in vivo functional in-frame start codon.

Niemann Pick disease (NPD) is an autosomal recessive disorder due to the deficit of lysosomal acid sphingomyelinase, which results in intracellular accumulation of sphingomyelin. In the present work we studied 18 patients with NPD type B, including five individuals who presented an intermediate phenotype characterised by different levels of neurological involvement. We identified nine novel mutations in the SMPD1 gene including six single base changes c.2T>G, c.96G>A, c.308T>C, c.674T>C, c.732G>C, c.841G>A (p.M1_W32del, p.W32X, p.L103P, p.L225P, p.W244C, p.A281T) and three frameshift mutations c.100delC, c.565dupC, c.575dupC (p.G34fsX42, p.P189fsX1 and p.P192fsX14). The novel c.2T>G (p.M1_W32del) mutation inactivates the first in-frame translation start site of the SMPD1 gene and in the homozygous status causes NPD type B indicating that in'vivo translation of wild type SMPD1 initiates from the first in-frame ATG. Moreover, the new c.96G>A (p.W32X) introduces a premature stop codon before the second in-frame ATG. As a consequence of either c.2T>G (p.M1_W32del) or c.96G>A (p.W32X), impaired translation from the first in-frame ATG results in a mild NPD-B phenotype instead of the severe phenotype expected for a complete deficiency of the enzyme, suggesting that when the first ATG is not functional, the second initiation codon (ATG33) still produces a fairly functional sphingomyelinase. Analysis of the patients'clinical and molecular data demonstrated that all five patients with the intermediate phenotype carried at least one severe mutation. No association between the onset of pulmonary symptoms and genotype was observed. Finally, the presence of c.96G>A (p.W32X), the most frequent allele among Italian NPD type B population, and c.1799G>C (p.R600P) as compound heterozygotes in association with severe mutations suggested a beneficial effect for both mutations.

Niemann-Pick C1 disease: correlations between NPC1 mutations, levels of NPC1 protein, and phenotypes emphasize the functional significance of the putative sterol-sensing domain and of the cysteine-rich luminal loop.

To obtain more information of the functional domains of the NPC1 protein, the mutational spectrum and the level of immunoreactive protein were investigated in skin fibroblasts from 30 unrelated patients with Niemann-Pick C1 disease. Nine of them were characterized by mild alterations of cellular cholesterol transport (the "variant" biochemical phenotype). The mutations showed a wide distribution to nearly all NPC1 domains, with a cluster (11/32) in a conserved NPC1 cysteine-rich luminal loop. Homozygous mutations in 14 patients and a phenotypically defined allele, combined with a new mutation, in a further 10 patients allowed genotype/phenotype correlations. Premature-termination-codon mutations, the three missense mutations in the sterol-sensing domain (SSD), and A1054T in the cysteine-rich luminal loop all occurred in patients with infantile neurological onset and "classic" (severe) cholesterol-trafficking alterations. By western blot, NPC1 protein was undetectable in the SSD missense mutations studied (L724P and Q775P) and essentially was absent in the A1054T missense allele. Our results thus enhance the functional significance of the SSD and demonstrate a correlation between the absence of NPC1 protein and the most severe neurological form. In the remaining missense mutations studied, corresponding to other disease presentations (including two adults with nonneurological disease), NPC1 protein was present in significant amounts of normal size, without clear-cut correlation with either the clinical phenotype or the "classic"/"variant" biochemical phenotype. Missense mutations in the cysteine-rich luminal loop resulted in a wide array of clinical and biochemical phenotypes. Remarkably, all five mutant alleles (I943M, V950M, G986S, G992R, and the recurrent P1007A) definitively correlated with the "variant" phenotype clustered within this loop, providing new insight on the functional complexity of the latter domain.

Ex vivo measurement of lipoprotein lipase-dependent very low density lipoprotein (VLDL)-triglyceride hydrolysis in human VLDL: an alternative to the postheparin assay of lipoprotein lipase activity?

The plasma lipolysis of triglyceride (TG)-rich lipoproteins is mainly due to the activity of lipoprotein lipase (LPL). Albeit important for our analysis of certain physiopathological situations, the determination of the magnitude of LPL-dependent lipolysis is not easy to perform. This essentially results from the binding of LPL to the luminal surface of vascular endothelium. The measurements of the whole putative LPL activity have been achieved after injection of heparin, a procedure that releases LPL from endothelium. However, the physiopathological relevance of this postheparin lipolysis assay (PHLA) remains questionable because it has never been demonstrated that the bulk of endothelium-bound LPL was active. It has been recently shown that a small part of LPL is associated to circulating lipoproteins in nonheparinized plasma, raising the possibility that the lipolysis mediated by this circulating LPL might reflect the overall LPL-dependent TG hydrolysis in plasma. To address this question, we developed a new lipolysis assay in which the very low density lipoprotein (VLDL)-bound LPL-dependent VLDL-TG hydrolysis (LVTH) was directly determined through the measurement of nonesterified fatty acid (NEFA) release during in vitro incubations. LVTH measurements were performed in control subjects, in type 2 diabetics, and in either heterozygous or homozygous LPL-deficient patients. In the latter group, LVTH values were extremely low. Those of heterozygous patients and of diabetics were similarly decreased by about 40% with respect to control group. Plasma TG concentrations exhibited an inverse relationship with LVTH level. In a subgroup of subjects, LVTH and PHLA were positively correlated and the inverse correlation of LVTH with plasma or VLDL-TG concentration was stronger than that obtained with PHLA. To further study the validity of this new assay, we measured LVTH in nine subjects who were studied for their catabolism of VLDL labeled with stable isotope. No relation was observed between the direct hepatic removal of VLDL and LVTH, whereas the latter was strikingly correlated with the rate of conversion of VLDL to intermediary density lipoprotein. Collective consideration of these findings strongly suggests that LVTH is a physiologically relevant index which could advantageously replace the measurements of PHLA in numerous physiopathological situations.

[Familial hyperchylomicronemia with a new mutation of the lipoprotein lipase gene]. / Hyperchylomicronémie familiale avec nouvelle mutation du gène de la lipoprotéine lipase.

INTRODUCTION: Familial hyperchylomicronemia is a rare autosomal recessive disease caused by lipoprotein lipase deficiency. CASE-REPORT: A nine month-old girl presented with eruptive xanthomas revealing a familial hyperchylomicronemia. No lipoprotein lipase activity was found. DNA analysis revealed a novel homozygous non-sense mutation of the lipoprotein lipase gene at the codon 288. The parents were heterozygous carriers. DISCUSSION: Familial hyperchylomicronemia usually presents with eruptiva xanthomas, abdominal pain, pancreatic manifestation and lipemia retinalis. Papulo-nodular xanthomas occur more frequently in children as in our case. Eighty lipoprotein lipase gene mutations have been recorded to date. The gene locates on chromosome 8. Only 9 non-sense mutations have been described which lead to a truncated protein. In our case, no enzymatic activity was detected probably due to an absence of secretion of the enzyme, even though catalytic activity persisted. The homozygous carrier status leads to hyperchylomicronemia whereas the heterozygote status may lead to mixed hyperlipidemia with an increased risk of atherosclerosis. The screening of lipoprotein lipase gene mutations should be carried out in all families with hyperchylomicronemia, regardless of the presence or absence of xanthomas.

Severe hypertriglyceridaemia in Type II diabetes: involvement of apoC-III Sst-I polymorphism, LPL mutations and apo E3 deficiency.

AIMS/HYPOTHESIS: Hypertriglyceridaemia is common in Type II (non-insulin-dependent) diabetes mellitus. Only subgroups of patient however have type V hyperlipidaemia. To investigate the coordination between genetic factors in the modulation of hypertriglyceridaemia in Type II diabetes, we studied three major modifier loci: apoC-III (both Sst-I and insulin-responsive element polymorphisms), apolipoprotein E genotypes and lipoprotein-lipase mutations. METHODS: We studied apoCIII gene polymorphisms, apolipoprotein E genotypes and lipoprotein-lipase gene mutations in 176 patients with Type II (non-insulin-dependent) diabetes mellitus, either normolipaemic (group N, n = 116), mildly hypertriglyceridaemic (group T, n = 28) or with a history of severe hypertriglyceridaemia (triglyceride > 15 g/l) (group H, n = 32). RESULTS: Mild hypertriglyceridaemia in Type II diabetes did not associate with any gene variants in this study. Severe hypertriglyceridaemia was, however, associated with the presence of the apoC-III S2 allele (50% of the patients in group H compared with 15.5 % in group N, p < 0.0001). Additionally this particular phenotype was associated with a low prevalence of the apo E3 allele (35.9% in group H vs 18.1 % in group N, p < 0.005) and a statistically significant over-representation of the E2E4 genotypes. Inactivating lipoprotein-lipase mutations were found in four patients (three heterozygotes, one homozygote), none was found in group N or T. Thus 68.7 % of group H patients (22/32) (vs 21.4 % in group T, p < 0.0005) were carriers of either S2 allele, lipoprotein-lipase mutants or E2E4 genotype with most lipoprotein-lipase mutants or E2E4 genotypes or both in the non-carriers for the S2 allele (6/7). CONCLUSION/INTERPRETATION: Our results strongly support the hypothesis that severe hyperlipaemia in Type II diabetes crucially depends on genetic factors which impair the clearance of triglyceride-rich lipoproteins.

VLDL-bound lipoprotein lipase facilitates the cholesteryl ester transfer protein-mediated transfer of cholesteryl esters from HDL to VLDL.

In recent years, it has been established that lipoprotein lipase (LPL) is partly associated with circulating lipoproteins. This report describes the effects of physiological amounts of very low density lipoprotein (VLDL)-bound LPL on the cholesteryl ester transfer protein (CETP)-mediated cholesteryl ester transfer (CET) from high density lipoprotein (HDL) to VLDL. Three patients with severe LPL deficiency exhibited a strong decrease in net mass CET that was more than 80% lower than that of common hypertriglyceridemic subjects. Recombination experiments showed that this was due to an abnormal behavior of the VLDL fraction. Replacement of the latter by normal VLDL totally normalized net mass CET. We therefore prepared VLDL containing controlled amounts of bound LPL that we used as CE acceptors in experiments involving unidirectional radioisotopic CET measurements. These were carried out either in the absence or in the presence of inhibitors of LPL lipolytic activity. When LPL-induced lipolysis was totally blocked, the stimulating effect of the enzyme on the CETP-dependent CET was only reduced by about 50%, showing that it did not entirely result from its lipolytic action. These data were dependent upon neither the type of LPL inhibitor (E600 or THL) nor the source of CETP (delipidated plasma or partially purified CETP). Thus, in addition to the well-known stimulating effect of LPL-dependent lipolysis on CET, our work demonstrates that physiological amounts of VLDL-bound LPL may facilitate CET through a mechanism partially independent of its lipolytic activity.

Niemann-Pick C1 disease: the I1061T substitution is a frequent mutant allele in patients of Western European descent and correlates with a classic juvenile phenotype.

Niemann-Pick type C (NPC) disease is an autosomal recessive lipid-storage disorder usually characterized by hepatosplenomegaly and severe progressive neurological dysfunction, resulting from mutations affecting either the NPC1 gene (in 95% of the patients) or the yet-to-be-identified NPC2 gene. Our initial study of 25 patients with NPC1 identified a T3182-->C transition that leads to an I1061T substitution in three patients. The mutation, located in exon 21, affects a putative transmembrane domain of the protein. PCR-based tests with genomic DNA were used to survey 115 unrelated patients from around the world with all known clinical and biochemical phenotypes of the disease. The I1061T allele constituted 33 (14.3%) of the 230 disease-causing alleles and was never found in controls (>200 alleles). The mutation was particularly frequent in patients with NPC from Western Europe, especially France (11/62 alleles) and the United Kingdom (9/32 alleles), and in Hispanic patients whose roots were in the Upper Rio Grande valley of the United States. The I1061T mutation originated in Europe and the high frequency in northern Rio Grande Hispanics results from a founder effect. All seven unrelated patients who were homozygous for the mutation and their seven affected siblings had a juvenile-onset neurological disease and severe alterations of intracellular LDL-cholesterol processing. The mutation was not found (0/40 alleles) in patients with the severe infantile neurological form of the disease. Testing for this mutation therefore has important implications for genetic counseling of families affected by NPC.

RER(+) phenotype in prostate intra-epithelial neoplasia associated with human prostate-carcinoma development.

The mutator (RER(+)) phenotype has been shown to be a mutational mechanism for tumour-suppressor-gene inactivation in colorectal cancer. A group of 60 prostate-carcinoma patients was studied to determine the frequency, intratumour distribution and timing of mutator phenotype in this cancer. Ten microsatellite loci were analyzed in 172 carcinoma foci (CF) and in 57 associated non-cancerous prostate tissues, including 31 areas of prostate intra-epithelial neoplasia (PIN) and 26 non-dysplastic areas with glandular hyperplasia (HP). We detected lesions with the RER(+) phenotype in 42% (25/60) of the prostate tumours. Clonal foci with RER(+) phenotype were detected at similar frequencies in pre-cancereous PIN (16%, 5/31) as in associated carcinoma foci (22%, 37/172), but were detected in only one of the 26 non-dysplastic prostate tissues studied (4%). Thus, clonal RER(+) foci were significantly more frequent in CF than in HP (p < 0.05). MI itself was significantly more frequent in CF (53%, p < 0.0001) and in PIN (35%, p < 0.05) than in HP (12%). Furthermore, 5 PIN harboured microsatellite mutations also detected in the associated cancer. Our overall results therefore strongly suggest that the mutator phenotype may occur as an early event in prostate tumorigenesis.

ras, p53 and HPV status in benign and malignant prostate tumors.

To study the role of ras, p53 genes and HPV virus (16 and 18) in the development of prostate cancer, we analyzed tissue sections from 27 patients affected with carcinomas (stages A to D) and from 24 patients with adenomas. Mutations of H, K and N-ras and p53 (exons 2-9) were studied by SSCP and DNA sequencing. Accumulation of p53 protein was studied by immunohistochemistry on tissue sections. Tumors were also analyzed for the presence of HPV16 and -18 sequences by PCR and DNA hybridization with sequence-specific oligonucleotides. No mutation was found in the three ras genes studied, either in carcinomas or adenomas. By SSCP analysis we identified p53 mutations in only 2 of 19 carcinomas studied, both in exon 7. Immunohistochemical results strongly correlate with the SSCP results: p53 protein was positive in tumors with p53 mutation but not in others; 32% of studied adenomas had detectable HPV16 DNA, while 53% of carcinomas were HPV16+. Among these I presented a p53 mutation. No HPV18 E6 sequence could be detected. Our data show that in prostate tumors from France, mutations of p53 and ras are rare events but that these tumors display detectable HPV16 DNA at a high frequency. The low incidence of p53 mutation, associated to a significant proportion of tumors showing HPV16 DNA, could suggest that in prostate cancer HPV16 infection could participate in p53 inactivation by E6.

Two germ-line mutations affecting the same nucleotide at codon 257 of p53 gene, a rare site for mutations.

Codon 257 of the p53 gene is an extremely rare target for somatic mutations (accounting for only two of 1600 published mutations). We report here two constitutional mutations both affecting the second nucleotide of codon 257. A thymine to adenine transversion resulting in an amino acid change from leucine to glutamine was found in one proband who developed multiple independent malignant tumors (osteosarcoma, phyllodes tumor, soft-tissue sarcoma). Her mother died of early-onset breast cancer. In the other case, a deletion resulting in a frameshift in the C-terminal coding region of p53 was found in a woman who was diagnosed with breast cancer at age 34. This woman belongs to a family with features of Li-Fraumeni syndrome. In both cases, the p53 mutations identified in the proband was found in other members of the family. Codon 257, even if rarely mutated in somatic cells, may thus be an important target for germ-line mutations.

Genetic heterogeneity of hepatocellular carcinoma.

We studied 80 hepatocellular carcinomas from three continents for p53 gene (TP53) mutations and hepatitis B virus (HBV) sequences. p53 mutations were frequent in tumors from Mozambique but not in tumors from South Africa, China, and Germany. Independent of geographic origin, most tumors were positive for HBV sequences. X gene coding sequences of HBV were detected in 78% of tumors, whereas viral sequences in the surface antigen- and core antigen-encoding regions were present in less than 45% of tumors. These observations indicate that hepatocellular carcinomas are genetically heterogeneous. Mozambican-type of hepatocellular carcinomas are characterized by a high incidence of p53 mutations related to aflatoxins. In other tumors, the rarity of p53 mutations combined with the frequent presence of viral X gene coding sequences suggests a possible interference of HBV with the wild-type p53 function.

Retinoblastoma and p53 tumor suppressor genes in human hepatoma cell lines.

We analyzed the status of retinoblastoma and p53 genes in 10 human hepatoma cell lines. Polyclonal anti-peptide antibodies generated against peptides homologous to COOH-terminal and leucine-zipper domains of the retinoblastoma protein allowed us to identify two cell lines (Hep 3B and FOCUS) with abnormal expression. The same cell lines have both lacked p53 expression. In contrast to the retinoblastoma gene, the expression of the p53 gene was abnormal in six additional cell lines. Indeed, only the Hep G2 hepatoblastoma cell line (and its derivative Hep G2/2215) appeared to have normal p53 and retinoblastoma gene expression. Our studies indicate that p53 abnormalities are common but retinoblastoma gene aberrations are rare in human hepatoma cell lines.