Heterozygous CAV1 frameshift mutations (MIM 601047) in patients with atypical partial lipodystrophy and hypertriglyceridemia

<p>Abstract</p> <p>Background</p> <p>Mice with a deleted <it>Cav1 </it>gene encoding caveolin-1 develop adipocyte abnormalities and insulin resistance. From genomic DNA of patients with atypical lipodystrophy and hypertriglyceridemia who had no mutations in any known lipodystrophy gene, we used DNA sequence analysis to screen the coding regions of human <it>CAV1 </it>(MIM 601047).</p> <p>Results</p> <p>We found a heterozygous frameshift mutation in <it>CAV1</it>, designated I134fsdelA-X137, in a female patient who had atypical partial lipodystrophy, with subcutaneous fat loss affecting the upper part of her body and face, but sparing her legs, gluteal region and visceral fat stores. She had severe type 5 hyperlipoproteinemia, with recurrent pancreatitis. In addition, she had some atypical features, including congenital cataracts and neurological findings. Her father was also heterozygous for this mutation, and had a similar pattern of fat redistribution, hypertriglyceridemia and congenital cataracts, with milder neurological involvement. An unrelated patient had a different heterozygous frameshift mutation in the <it>CAV1 </it>gene, designated -88delC. He also had a partial lipodystrophy phenotype, with subcutaneous fat loss affecting the arms, legs and gluteal region, but sparing his face, neck and visceral fat stores. He also had severe type 5 hyperlipoproteinemia, with recurrent pancreatitis; however he had no clinically apparent neurological manifestations. The mutations were absent from the genomes of 1063 healthy individuals.</p> <p>Conclusion</p> <p>Thus, very rare <it>CAV1 </it>frameshift mutations appear to be associated with atypical lipodystrophy and hypertriglyceridemia.</p

Alstrom syndrome (OMIM 203800): a case report and literature review

<p>Abstract</p> <p>Background</p> <p>Alstrom syndrome (AS) is a rare autosomal recessive disease characterized by multiorgan dysfunction. The key features are childhood obesity, blindness due to congenital retinal dystrophy, and sensorineural hearing loss. Associated endocrinologic features include hyperinsulinemia, early-onset type 2 diabetes, and hypertriglyceridemia. Thus, AS shares several features with the common metabolic syndrome, namely obesity, hyperinsulinemia, and hypertriglyceridemia. Mutations in the <it>ALMS1 </it>gene have been found to be causative for AS with a total of 79 disease-causing mutations having been described.</p> <p>Case presentation</p> <p>We describe the case of a 27-year old female from an English (Caucasian) kindred. She had been initially referred for hypertriglyceridemia, but demonstrated other features suggestive of AS, including blindness, obesity, type 2 diabetes, renal dysfunction, and hypertension. DNA analysis revealed that she is a compound heterozygote with two novel mutations in the <it>ALMS1 </it>gene – H3882Y and V424I. Examination of her family revealed that her phenotypically unaffected mother and younger sister also had heterozygous mutations in the <it>ALMS1 </it>gene. In addition to presenting these novel molecular findings for AS, we review the clinical and genetic features of AS in the context of our case.</p> <p>Conclusion</p> <p>Two novel mutations in the <it>ALMS1 </it>gene causative for AS have been reported here, thereby increasing the number of reported mutations to 81 and providing a wider basis for mutational screening among affected individuals.</p

Assessing the association of the HNF1A G319S variant with C-reactive protein in Aboriginal Canadians: a population-based epidemiological study

<p>Abstract</p> <p>Background</p> <p>C-reactive protein (CRP), a biomarker of inflammation, has been associated with increased risk of developing cardiovascular disease. Common variants of the hepatocyte nuclear factor 1A (<it>HNF1A) </it>gene encoding HNF-1α have been associated with plasma CRP in predominantly European Caucasian samples. <it>HNF1A </it>might therefore have an impact on vascular disease and diabetes risk that is mediated by CRP. In an Aboriginal Canadian population, a private polymorphism, <it>HNF1A </it>G319S, was associated with increased prevalence of type 2 diabetes. However, it has not been investigated whether this association is mediated by CRP. We aimed to investigate whether CRP was mediating the association between <it>HNF1A </it>G319S and type 2 diabetes in an Aboriginal Canadian population with a high prevalence of diabetes.</p> <p>Methods</p> <p>A total of 718 individuals who participated in a diabetes prevalence and risk factor survey were included in the current analysis. Participants were genotyped for <it>HNF1A </it>G319S. Fasting plasma samples were analyzed for CRP. Fasting plasma glucose and a 75-g oral glucose tolerance test were obtained to determine type 2 diabetes.</p> <p>Results</p> <p>The prevalence rate of type 2 diabetes was 17.4% (125/718) using the 1999 World Health Organization definition and was higher among S319 allele carriers compared to G/G homozygotes (p < 0.0001). Among participants without type 2 diabetes, CRP levels were higher among G/G homozygotes (1.64 [95% confidence interval 1.35-2.00] mg/l) than in S319 carriers (1.26 [1.04-1.54] mg/l) (p = 0.009) after adjustment for age, sex, 2-h post-load glucose, waist circumference, and serum amyloid A. CRP levels were elevated among those with diabetes after similar adjustment (4.39 [95% confidence interval 3.09-6.23] and 4.44 [3.13-6.30] mg/L, respectively), and no significant difference in CRP was observed between S319 carriers and non-carriers (p = 0.95).</p> <p>Conclusions</p> <p>CRP levels were lower in S319 allele carriers of the <it>HNF1A </it>gene compared to non-carriers among individuals without diabetes, but this difference was not present among those with diabetes, who uniformly had elevated CRP levels. Therefore, while <it>HNF1A </it>appears to influence CRP concentrations in the non-diabetic state, chronic elevation of CRP is unlikely mediating the association between the <it>HNF1A </it>polymorphism and the high prevalence of type 2 diabetes in this Aboriginal population.</p

Disparate associations of a functional promoter polymorphism in PCK1 with carotid wall ultrasound traits

Background and Purpose - Cytosolic phosphoenolpyruvate carboxykinase (PEPCK; EC 4.1.1.32), encoded by PCK1, catalyzes the first committed step in gluconeogenesis. We previously showed that a -232C\u3eG promoter polymorphism within a cis-acting element required for basal and cAMP-mediated PCK1 gene transcription results in loss of negative regulation by insulin, contributing to worsened metabolic control in the context of insulin resistance. We hypothesized that this polymorphism would be associated with carotid atherosclerosis in a sample of 150 aboriginal Canadians. Methods - Dependent variables were 2 distinct carotid traits, namely intima-media thickness (IMT) assessed using B-mode ultrasound and total carotid plaque volume (TPV) assessed using 3D ultrasound. Results - Multivariate analysis showed significant but opposite associations of PCK1 genotype with these traits. Specifically, subjects with the PCK1-232G/G genotype had more carotid IMT (0.80±0.02 versus 0.73±0.03 mm; P=0.007) but less TPV (0.10±0.09 versus 0.38±0.13; P=0.03) than subjects with other genotypes. Conclusions - The findings connect the key enzyme in gluconeogenesis with atherosclerosis. The meaning of the opposing associations of PCK1 genotype with IMT and TPV is unclear; more work is required to confirm whether these might be distinct quantitative traits with different biological determinants. © 2005 American Heart Association, Inc

Peroxisomal proliferator activated receptor-γ deficiency in a Canadian kindred with familial partial lipodystrophy type 3 (FPLD3)

BACKGROUND: Familial partial lipodystrophy (Dunnigan) type 3 (FPLD3, Mendelian Inheritance in Man [MIM] 604367) results from heterozygous mutations in PPARG encoding peroxisomal proliferator-activated receptor-γ. Both dominant-negative and haploinsufficiency mechanisms have been suggested for this condition. METHODS: We present a Canadian FPLD3 kindred with an affected mother who had loss of fat on arms and legs, but no increase in facial, neck, suprascapular or abdominal fat. She had profound insulin resistance, diabetes, severe hypertriglyceridemia and relapsing pancreatitis, while her pre-pubescent daughter had normal fat distribution but elevated plasma triglycerides and C-peptide and depressed high-density lipoprotein cholesterol. RESULTS: The mother and daughter were each heterozygous for PPARG nonsense mutation Y355X, whose protein product in vitro was transcriptionally inactive with no dominant-negative activity against the wild-type receptor. In addition the mutant protein appeared to be markedly unstable. CONCLUSION: Taken together with previous studies of human PPARG mutations, these findings suggest that PPAR-γ deficiency due either to haploinsufficiency or to substantial activity loss due to dominant negative interference of the normal allele product's function can each contribute to the FPLD3 phenotype

A polygenic basis for four classical Fredrickson hyperlipoproteinemia phenotypes that are characterized by hypertriglyceridemia

Numerous single nucleotide polymorphisms (SNPs) have been found in recent genome wide association studies (GWAS) to be associated with subtle plasma triglyceride (TG) variation in normolipidemic subjects. However, since these GWAS did not specifically evaluate patients with rare disorders of lipoprotein metabolism—‘hyperlipoproteinemia’ (HLP)—it remains largely unresolved whether any of these SNP determinants of modest physiological changes in TG are necessarily also determinants of most HLP phenotypes. To address this question, we evaluated 28 TG-associated SNPs from GWAS in 386 unrelated adult patients with one of five Fredrickson phenotypes (HLP types 2A, 2B, 3, 4 and 5) and 242 matched normolipidemic controls. We found that several SNPs associated with TG in normolipidemic samples, including APOA5 p.S19W and -1131T>C, TRIB1 rs17321515, TBL2 rs17145738, GCKR rs780094, GALNT2 rs4846914 and ANGPTL3 rs12130333, were significantly associated with HLP types 2B, 3, 4 and 5. The findings indicate that: (i) the TG-associated Fredrickson HLP types 2B, 3, 4 and 5 are polygenic traits; (ii) these Fredrickson HLP types share numerous genetic determinants among themselves; and (iii) genetic determinants of modest TG variation in normolipidemic population samples also underlie—to an apparently even greater degree—susceptibility to these rare HLP phenotypes. Thus, the TG-associated Fredrickson HLP types 2B, 3, 4 and 5, although historically considered to be distinct are actually complex traits sharing among them several common genetic determinants seen in GWAS of normolipidemic population samples

HNF1A G319S variant, active cigarette smoking and incident type 2 diabetes in Aboriginal Canadians: a population-based epidemiological study

<p>Abstract</p> <p>Background</p> <p>In a recent report of large-scale association analysis, a type 2 diabetes susceptibility locus near <it>HNF1A </it>was identified in predominantly European descent populations. A population-specific G319S polymorphism in <it>HNF1A </it>was previously identified in Aboriginal Canadians who have a high prevalence of type 2 diabetes. We aimed to investigate the association of the <it>HNF1A </it>G319S polymorphism with incident type 2 diabetes and to assess whether clinical risk variables for type 2 diabetes influence the association in an Aboriginal population.</p> <p>Methods</p> <p>Of 606 participants who were free of diabetes at baseline in 1993-1995, 540 (89.1%) participated in 10-year follow-up assessments in 2003-2005. Fasting glucose and a 75-g oral glucose tolerance test were obtained to determine incident type 2 diabetes. Participants were genotyped for the <it>HNF1A </it>G319S polymorphism. Interviewers administered questionnaires on smoking behavior.</p> <p>Results</p> <p>The incidence rates of type 2 diabetes were 14.2% (55/388) in major allele homozygotes and 31.2% (29/93) in minor allele carriers (p < 0.001). The <it>HNF1A </it>G319S carrier status was associated with incident type 2 diabetes (odds ratio [OR] 3.78 [95% CI 2.13-6.69]) after adjustment for age, sex, hypertension, triglyceride, HDL cholesterol, and waist circumference. A statistical interaction was observed between <it>HNF1A </it>G319S and baseline active cigarette smoking on the development of type 2 diabetes with similar adjustment (p = 0.006). When participants were stratified by baseline smoking status, <it>HNF1A </it>G319S carriers who were active smokers had increased risk of developing diabetes (OR 6.91 [95% CI 3.38-14.12]), while the association was attenuated to non-significance among non-smokers (1.11 [0.40-3.08]).</p> <p>Conclusions</p> <p>The <it>HNF1A </it>G319S variant is associated with incident type 2 diabetes in Aboriginal Canadians. Furthermore, cigarette smoking appears to amplify incident diabetes risk in carriers of <it>HNF1A </it>G319S.</p

Targeted Next-generation Sequencing and Bioinformatics Pipeline to Evaluate Genetic Determinants of Constitutional Disease

Next-generation sequencing (NGS) is quickly revolutionizing how research into the genetic determinants of constitutional disease is performed. The technique is highly efficient with millions of sequencing reads being produced in a short time span and at relatively low cost. Specifically, targeted NGS is able to focus investigations to genomic regions of particular interest based on the disease of study. Not only does this further reduce costs and increase the speed of the process, but it lessens the computational burden that often accompanies NGS. Although targeted NGS is restricted to certain regions of the genome, preventing identification of potential novel loci of interest, it can be an excellent technique when faced with a phenotypically and genetically heterogeneous disease, for which there are previously known genetic associations. Because of the complex nature of the sequencing technique, it is important to closely adhere to protocols and methodologies in order to achieve sequencing reads of high coverage and quality. Further, once sequencing reads are obtained, a sophisticated bioinformatics workflow is utilized to accurately map reads to a reference genome, to call variants, and to ensure the variants pass quality metrics. Variants must also be annotated and curated based on their clinical significance, which can be standardized by applying the American College of Medical Genetics and Genomics Pathogenicity Guidelines. The methods presented herein will display the steps involved in generating and analyzing NGS data from a targeted sequencing panel, using the ONDRISeq neurodegenerative disease panel as a model, to identify variants that may be of clinical significance