BACKGROUND Genomewide association studies can be used to identify disease-relevant genomic regions, but interpretation of the data is challenging. The FTO region harbors the strongest genetic association with obesity, yet the mechanistic basis of this association remains elusive. METHODS We examined epigenomic data, allelic activity, motif conservation, regulator expression, and gene coexpression patterns, with the aim of dissecting the regulatory circuitry and mechanistic basis of the association between the FTO region and obesity. We validated our predictions with the use of directed perturbations in samples from patients and from mice and with endogenous CRISPR–Cas9 genome editing in samples from patients. RESULTS Our data indicate that the FTO allele associated with obesity represses mitochondrial thermogenesis in adipocyte precursor cells in a tissue-autonomous manner. The rs1421085 T-to-C single-nucleotide variant disrupts a conserved motif for the ARID5B repressor, which leads to derepression of a potent preadipocyte enhancer and a doubling of IRX3 and IRX5 expression during early adipocyte differentiation. This results in a cell-autonomous developmental shift from energy-dissipating beige (brite) adipocytes to energy-storing white adipocytes, with a reduction in mitochondrial thermogenesis by a factor of 5, as well as an increase in lipid storage. Inhibition of Irx3 in adipose tissue in mice reduced body weight and increased energy dissipation without a change in physical activity or appetite. Knockdown of IRX3 or IRX5 in primary adipocytes from participants with the risk allele restored thermogenesis, increasing it by a factor of 7, and overexpression of these genes had the opposite effect in adipocytes from nonrisk-allele carriers. Repair of the ARID5B motif by CRISPR–Cas9 editing of rs1421085 in primary adipocytes from a patient with the risk allele restored IRX3 and IRX5 repression, activated browning expression programs, and restored thermogenesis, increasing it by a factor of 7. CONCLUSIONS Our results point to a pathway for adipocyte thermogenesis regulation involving ARID5B, rs1421085, IRX3, and IRX5, which, when manipulated, had pronounced pro-obesity and anti-obesity effects. (Funded by the German Research Center for Environmental Health and others.)
Renal disease variability in autosomal dominant polycystic kidney disease (ADPKD) is strongly influenced by the gene locus (PKD1 versus PKD2). Recent studies identified nontruncating PKD1 mutations in approximately 30% of patients who underwent comprehensive mutation screening, but the clinical significance of these mutations is not well defined. We examined the genotype-renal function correlation in a prospective cohort of 220 unrelated ADPKD families ascertained through probands with serum creatinine #1.4 mg/dl at recruitment. We screened these families for PKD1 and PKD2 mutations and reviewed the clinical outcomes of the probands and affected family members. Height-adjusted total kidney volume (htTKV) was obtained in 161 affected subjects. Multivariate Cox proportional hazard modeling for renal and patient survival was performed in 707 affected probands and family members. Overall, we identified pathogenic mutations in 84.5% of our families, in which the prevalence of PKD1 truncating, PKD1 in-frame insertion/deletion, PKD1 nontruncating, and PKD2 mutations was 38.3%, 4.3%, 27.1%, and 30.3%, respectively. Compared with patients with PKD1 truncating mutations, patients with PKD1 in-frame insertion/deletion, PKD1 nontruncating, or PKD2 mutations have smaller htTKV and reduced risks (hazard ratio Autosomal dominant polycystic kidney disease (ADPKD) is the most common inherited kidney disease worldwide, responsible for 5%-10% of ESRD. 1,2 Mutations in two genes (PKD1 and PKD2) account for most patients with ADPKD. 2,3 Previous studies of European families ascertained through probands enriched with renal failure reported that approximately 85% and approximately 15% of ADPKD families were linked to the PKD1 and PKD2 loci, respectively. 3 However, a higher prevalence of PKD2 of 26% has been recently reported in a population-based study. 4 Disease progression of ADPKD is highly variable, in part because of a strong gene locus effect. [5][6][7][8] Adjusted for age, patients with PKD1 have larger kidneys and earlier onset of ESRD than patients with PKD2 (mean age at ESRD, 53.4 versus 72.7 years old, respectively). 5,6,8 Additionally, significant intrafamilial renal disease variability in ADPKD suggests a modifier effect. [9][10][11] [
Pathogenic variants of CYP24A1 are associated with hypercalcemia due to disruptions in the ability of 24-hydroxylase to break down 1,25-dihydroxyvitamin D (1,25-DHVD). A case involving a heterozygous pathogenic variant of CYP24A1 and primary hyperparathyroidism leading to severe hypercalcemia has not been previously reported. A 23-year-old woman presented with fatigue and was found to be hypercalcemic at 13.8 mg/dL [reference range, 8.4-10.2 pg/mL]. Her parathyroid hormone (PTH) was 62 pg/mL [reference range, 19-88 pg/mL] and 1,25-DHVD was elevated to 242.7 pg/mL [reference range, 18-72 pg/mL]. Other laboratory workup was unrevealing. She had a bone scan, whole body CT scan, and thyroid ultrasound that were normal. Her 25-hydroxy-vitamin D to 24,25-dihydroxy-vitamin D ratio was elevated at 25.18 (normal, < 25). Because of concern for primary hyperparathyroidism, she was referred to an endocrine surgeon and underwent a parathyroidectomy with the removal of a 3.5-gram adenoma. Pathology showed a parafibromin-deficient parathyroid neoplasm. Genetic testing demonstrated a heterozygous pathogenic variant in CYP24A1. Three weeks after surgery, PTH was 14 pg/mL (1.48 pmol/L), calcium and 1,25-DHVD normalized. In summary, we report a case where a patient with severe symptomatic hypercalcemia was found to have primary hyperparathyroidism exacerbated by an underlying heterozygous pathogenic variant in CYP24A1.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.