ClinVar database of global familial hypercholesterolemia-associated DNA variants.

Accurate and consistent variant classification is imperative for incorporation of rapidly developing sequencing technologies into genomic medicine for improved patient care. An essential requirement for achieving standardized and reliable variant interpretation is data sharing, facilitated by a centralized open-source database. Familial hypercholesterolemia (FH) is an exemplar of the utility of such a resource: it has a high incidence, a favorable prognosis with early intervention and treatment, and cascade screening can be offered to families if a causative variant is identified. ClinVar, an NCBI-funded resource, has become the primary repository for clinically relevant variants in Mendelian disease, including FH. Here, we present the concerted efforts made by the Clinical Genome Resource, through the FH Variant Curation Expert Panel and global FH community, to increase submission of FH-associated variants into ClinVar. Variant-level data was categorized by submitter, variant characteristics, classification method, and available supporting data. To further reform interpretation of FH-associated variants, areas for improvement in variant submissions were identified; these include a need for more detailed submissions and submission of supporting variant-level data, both retrospectively and prospectively. Collaborating to provide thorough, reliable evidence-based variant interpretation will ultimately improve the care of FH patients.

[Familial hypertriglyceridemia: biochemical, clinical and molecular study in a Moroccan family]. / Hypertriglycéridémie familiale : étude biochimique, clinique et moléculaire dans une famille marocaine.

Familial hypertriglyceridemia is a rare autosomal recessive inborn error of metabolism. Mutation within the LPL gene constitutes the first cause of monogenic etiology. Lipoprotein lipase (LPL) is the key enzyme in triglyceride-rich lipoproteins catabolism. Familial LPL deficiency is expressed by eruptive xanthomatosis and acute pancreatitis. We report a Moroccan case with a monstrous hypertriglyceridemia caused by LPL gene mutation. We discuss pathophysiology aspects according to available investigations data and the relevance of familial screening. The proband is a 19-year-old woman originating from the village of Taourirt (South of Morocco). She was admitted in emergency for diabetic ketoacidosis. Clinical investigations and routine laboratory tests were performed upon admission. Then lipoprotein electrophoresis and sequencing of the LPL gene were practiced. A monstrous hypertriglyceridemia up to 199 mmol/L was found. Lipoprotein electrophoresis has objectified profound disturbances on chylomicrons, VLDL and IDL. The sequencing detected a missense mutation p.S286R at homozygous state in a consanguinity context. Discovery of this LPL gene mutation is the first indigenous and documented case, never related in any other ethnic group. It constitutes a novel proof of a founder effect in the south Moroccan population. Prevalence studies with familial screening should be done for preventative action which is the only acceptable way to limit the cardiovascular and pancreatitis risks in this population where inbreeding is a general rule.

Phenotypic spectrum of fetal Smith-Lemli-Opitz syndrome.

The Smith-Lemli-Opitz syndrome (SLOS) is an autosomal recessive multiple congenital malformation syndrome caused by dehydrocholesterol reductase deficiency. The diagnosis is confirmed by high 7- and secondarily 8-dehydrocholesterol levels in plasma and tissues and/or by detection of biallelic mutations in the DHCR7 gene. The phenotypic spectrum of SLOS is broad, ranging from a mild phenotype combining subtle physical anomalies with behavioral and learning problems, to a perinatally lethal multiple malformations syndrome. The fetal phenotype of SLOS has been poorly described in the literature. We report a series of 10 fetuses with molecularly proven SLOS. Even in young fetuses, the facial dysmorphism appears characteristic. Genital abnormalities are rare in 46,XX subjects. Gonadal differentiation appears histologically normal and in agreement with the chromosomal sex, contrary to what has been previously stated. We observed some previously unreported anomalies: ulnar hypoplasia, vertebral segmentation anomalies, congenital pulmonary adenomatoid malformation, fused lungs, gastroschisis, holomyelia and hypothalamic hamartoma. This latter malformation proves that SLOS phenotypically overlaps with Pallister-Hall syndrome which remains clinically a major differential diagnosis of SLOS.

Evidence of postzygotic mosaicism in a transmitted form of Conradi-Hunermann-Happle syndrome associated with a novel EBP mutation.

BACKGROUND: X-linked dominant chondrodysplasia punctata, also known as Conradi-Hünermann-Happle syndrome, is a rare skeletal dysplasia characterized by short stature, craniofacial defects, cataracts, ichthyosis, coarse hair, and alopecia. Conradi-Hünermann-Happle syndrome is caused by mutations in the gene EBP encoding Δ(8)-Δ(7) sterol isomerase emopamil-binding protein. Random X-inactivation could account for the intrafamilial variability of the phenotype of X-linked dominant chondrodysplasia punctata. OBSERVATIONS: We describe a girl with clinical features of X-linked dominant chondrodysplasia punctata. Biochemical analysis showed an abnormal sterol profile consistent with a defect in Δ(8)-Δ(7) sterol isomerase. Molecular studies confirmed the diagnosis by identifying a novel heterozygous missense EBP mutation (c.199C>T; p.Cys67Arg). The mutation was not detectable on genomic DNA extracted from blood lymphocytes in both parents. The mother presented with an erythematous and ichthyosiform skin lesion. EBP analysis of DNA extracted from a lesional skin biopsy revealed the presence of p.Cys67Arg mutation. CONCLUSION: To our knowledge, we report the first molecular confirmation of postzygotic mosaicism on an ichthyosiform skin lesion in the mother of a girl with X-linked dominant chondrodysplasia punctata associated with a novel EBP mutation.

[Genetic factors associated with age-related macular degeneration]. / Génétique de la dégénérescence maculaire liée à l'âge.

Age related macular degeneration (AMD) is the leading cause of vision loss in the elderly in developed countries. Genetic factors play a major role in this multifactorial and polygenic disease. Genomewide analysis identified two loci on 1q25-31 and 10q26 chromosomes associated with AMD, and association studies highlighted the implication of SNPs located in the complement H factor gene (CFH) on 1q25-31 and in PLEKHA1-HTRA1-LOC387715 on 10q26 in the disease. Homozygous carriers for the at-risk alleles of the CFH, HTRA1, and LOC387715 genes have an increased risk to develop exudative AMD with odds ratio of 6.2, 6.9, et 7.3 respectively. Moreover, other genes involved in the complement cascade, namely the genes of the C2, C3 component, and factor B, are associated to the disease. The SCARB1 gene has also recently been associated to AMD. Genotype-phenotype correlations have been performed in AMD patients and found that occult CNV are more often associated to CFH at-risk allele and classic CNV to HTRA1 at-risk allele. This last allele seems also linked to more severe forms of the disease. These new major genetic factors could lead to a new clinical approach of AMD and to the discovery of new therapeutic targets.

Genotype-phenotype correlations for exudative age-related macular degeneration associated with homozygous HTRA1 and CFH genotypes.

PURPOSE: Major genetic factors for age-related macular degeneration (AMD) have recently been identified as susceptibility risk factors, including polymorphisms of HTRA1 and CFH genes. The purpose was to analyze the angiographic features of patients harboring homozygous genotypes for HTRA1 and CFH genes in a French exudative AMD population. METHODS: Two hundred patients affected with exudative AMD were genotyped for the polymorphisms rs11200638 of the HTRA1 gene and rs10611710 of the CFH gene. Four homozygous groups were extracted from the entire cohort: double homozygous for wild-type alleles of both genes (group 1), homozygous for the polymorphism of the HTRA1 gene only (group 2), homozygous for the polymorphism of the CFH gene only (group 3), and double homozygous carriers for both polymorphisms (group 4). Choroidal neovascularization (CNV) was graded as classic and predominantly classic (PC), occult, minimally classic (MC), or retinal angiomatosis proliferation (RAP). RESULTS: Group 1 (n = 9) presented 44.4% classic and PC, 33.3% occult, 11.1% MC, and 11.1% RAP. Group 2 (n = 12) presented 50.0% classic and PC, 33.3% occult, no MC CNV and 16.7% RAP. Group 3 (n = 28) presented 10.7% classic and PC, 67.9% occult, 14.3% MC, and 7.1% RAP. Group 4 (n = 17) presented 29.4% classic and PC, 52.9% occult, 11.8% MC, and 5.9% RAP. Occult CNV or MC CNV was more frequently observed in group 3 than in group 2 (82.1% vs 33.3%; P < 0.02). Classic and PC CNV were more frequently observed in group 2 than in group 3 (50% vs. 10.7%; P < 0.03). CONCLUSIONS: This attempt at a genotypic-angiographic correlation in an exudative AMD sample suggests an association between occult or MC CNV and the CFH polymorphism and between classic and PC CNV and the HTRA1 polymorphism.

Magnitude of HDL cholesterol variation after high-dose atorvastatin is genetically determined at the LDL receptor locus in patients with homozygous familial hypercholesterolemia.

OBJECTIVE: The combination of LDL apheresis with high doses of a potent hepatic hydroxymethylglutaryl coenzyme A reductase inhibitor, such as atorvastatin, has been the best therapy available for the prevention of cardiovascular disease in patients with homozygous familial hypercholesterolemia (HFH). However, some concerns have been made about the effect of atorvastatin on HDL cholesterol levels in these patients. METHODS AND RESULTS: HDL cholesterol levels were determined bimonthly over the course of 2 years of treatment with high-dose atorvastatin in genotypically defined HFH patients either receptor-defective (n=6) or receptor-negative (n=6) under long-term treatment with LDL apheresis. We additionally stratified the atorvastatin effect on HDL cholesterol according to the genotype as an indicator of residual in vivo LDL receptor activity. Our findings indicate that (1) an early and transitory reduction of plasma HDL cholesterol levels occurs during the first 4 weeks of atorvastatin treatment; (2) the degree of the transient HDL reduction is higher in receptor-negative than in receptor-defective patients (-21+/-11 versus -10+/-4%; P=0.01); and (3) after long-term treatment, HDL cholesterol concentration remains higher in receptor-defective than receptor-negative patients (P=0.026). CONCLUSIONS: The present study reveals that HDL cholesterol reduction after high-dose atorvastatin is an early and transient event in HFH patients which magnitude depends on the presence of a residual LDL-R activity.

Intronic mutations outside of Alu-repeat-rich domains of the LDL receptor gene are a cause of familial hypercholesterolemia.

Familial hypercholesterolemia (FH), a frequent monogenic condition complicated by premature cardiovascular disease, is characterized by high allelic heterogeneity at the low-density lipoprotein receptor ( LDLR) locus. Despite more than a decade of genetic testing, knowledge about intronic disease-causing mutations has remained limited because of lack of available genomic sequences. Based on the finding from bioinformatic analysis that Alu repeats represent 85% of LDLR intronic sequences outside exon-intron junctions, we designed a strategy to improve the exploration of genomic regions in the vicinity of exons in 110 FH subjects from an admixed population. In the first group of 42 patients of negative mutation carriers, as previously established by former screening strategies (denaturing gradient gel electrophoresis, DNA sequencing with former primers overlapping splice-sites, Southern Blotting), about half ( n=22) were found to be carriers of at least one heterozygous mutation. Among a second group of 68 newly recruited patients, 27% of mutation carriers ( n=37) had a splicing regulatory mutation. Overall, out of the 54 mutations identified, 13 were intronic, and 18 were novel, out of which nearly half were intronic. Two novel intronic mutations (IVS8-10G-->A within the polypyrimidine tract and IVS7+10G-->A downstream of donor site) might create potential aberrant splice sites according to neural-network computed estimation, contrary to 31 common single nucleotide variations also identified at exon-intron junctions. This new strategy of detecting the most likely disease-causing LDLR mutations outside of Alu-rich genomic regions reveals that intronic mutations may have a greater impact than previously reported on the molecular basis of FH.