This study shows that mutations effecting Gα11 loss of function cause familial hypocalciuric hypercalcemia type 2, and mutations effecting Gα11 gain of function result in autosomal dominant ...hypocalcemia type 2. Important aspects of Gα11 function are also described.
Familial hypocalciuric hypercalcemia, an autosomal dominant disorder, is characterized by lifelong elevations of serum calcium concentrations with low urinary calcium excretion (mean urinary calcium:creatinine clearance ratio, <0.01) and normal circulating parathyroid hormone concentrations in 80% of patients (see Table S1 in the Supplementary Appendix, available with the full text of this article at NEJM.org).
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Patients with familial hypocalciuric hypercalcemia are generally asymptomatic, although pancreatitis or chondrocalcinosis may develop in some affected adults.
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Familial hypocalciuric hypercalcemia is genetically heterogeneous, with three reported variants. Type 1 is due to loss-of-function mutations of the calcium-sensing receptor (encoded by
CASR
), type 2 is . . .
Context:
The tumorigenic role of genetic abnormalities in sporadic pituitary nonfunctioning adenomas (NFAs), which usually originate from gonadotroph cells, is unknown.
Objective:
The objective of ...the study was to identify somatic genetic abnormalities in sporadic pituitary NFAs.
Design:
Whole-exome sequencing was performed using DNA from 7 pituitary NFAs and leukocyte samples obtained from the same patients. Somatic variants were confirmed by dideoxynucleotide sequencing, and candidate driver genes were assessed in an additional 24 pituitary NFAs.
Results:
Whole-exome sequencing achieved a high degree of coverage such that approximately 97% of targeted bases were represented by more than 10 base reads; 24 somatic variants were identified and confirmed in the discovery set of 7 pituitary NFAs (mean 3.5 variants/tumor; range 1–7). Approximately 80% of variants occurred as missense single nucleotide variants and the remainder were synonymous changes or small frameshift deletions. Each of the 24 mutations occurred in independent genes with no recurrent mutations. Mutations were not observed in genes previously associated with pituitary tumorigenesis, although somatic variants in putative driver genes including platelet-derived growth factor D (PDGFD), N-myc down-regulated gene family member 4 (NDRG4), and Zipper sterile-α-motif kinase (ZAK) were identified; however, DNA sequence analysis of these in the validation set of 24 pituitary NFAs did not reveal any mutations indicating that these genes are unlikely to contribute significantly in the etiology of sporadic pituitary NFAs.
Conclusions:
Pituitary NFAs harbor few somatic mutations consistent with their low proliferation rates and benign nature, but mechanisms other than somatic mutation are likely involved in the etiology of sporadic pituitary NFAs.
Cushing's syndrome, which is characterized by excessive circulating glucocorticoid concentrations, may be due to ACTH-dependent or -independent causes that include anterior pituitary and adrenal ...cortical tumors, respectively. ACTH secretion is stimulated by CRH, and we report a mouse model for Cushing's syndrome due to an N-ethyl-N-nitrosourea (ENU) induced Crh mutation at −120 bp of the promoter region, which significantly increased luciferase reporter activity and was thus a gain-of-function mutation. Crh−120/+ mice, when compared with wild-type littermates, had obesity, muscle wasting, thin skin, hair loss, and elevated plasma and urinary concentrations of corticosterone. In addition, Crh−120/+ mice had hyperglycemia, hyperfructosaminemia, hyperinsulinemia, hypercholesterolemia, hypertriglyceridemia, and hyperleptinemia but normal adiponectin. Crh−120/+ mice also had low bone mineral density, hypercalcemia, hypercalciuria, and decreased concentrations of plasma PTH and osteocalcin. Bone histomorphometry revealed Crh−120/+ mice to have significant reductions in mineralizing surface area, mineral apposition, bone formation rates, osteoblast number, and the percentage of corticoendosteal bone covered by osteoblasts, which was accompanied by an increase in adipocytes in the bone marrow. Thus, a mouse model for Cushing's syndrome has been established, and this will help in further elucidating the pathophysiological effects of glucocorticoid excess and in evaluating treatments for corticosteroid-induced osteoporosis.
Mutations of UDP-N-acetyl-alpha-D-galactosamine polypeptide N-acetyl galactosaminyl transferase 3 (GALNT3) result in familial tumoural calcinosis (FTC) and the hyperostosis-hyperphosphataemia ...syndrome (HHS), which are autosomal recessive disorders characterised by soft-tissue calcification and hyperphosphataemia. To facilitate in vivo studies of these heritable disorders of phosphate homeostasis, we embarked on establishing a mouse model by assessing progeny of mice treated with the chemical mutagen N-ethyl-N-nitrosourea (ENU), and identified a mutant mouse, TCAL, with autosomal recessive inheritance of ectopic calcification, which involved multiple tissues, and hyperphosphataemia; the phenotype was designated TCAL and the locus, Tcal. TCAL males were infertile with loss of Sertoli cells and spermatozoa, and increased testicular apoptosis. Genetic mapping localized Tcal to chromosome 2 (62.64-71.11 Mb) which contained the Galnt3. DNA sequence analysis identified a Galnt3 missense mutation (Trp589Arg) in TCAL mice. Transient transfection of wild-type and mutant Galnt3-enhanced green fluorescent protein (EGFP) constructs in COS-7 cells revealed endoplasmic reticulum retention of the Trp589Arg mutant and Western blot analysis of kidney homogenates demonstrated defective glycosylation of Galnt3 in Tcal/Tcal mice. Tcal/Tcal mice had normal plasma calcium and parathyroid hormone concentrations; decreased alkaline phosphatase activity and intact Fgf23 concentrations; and elevation of circulating 1,25-dihydroxyvitamin D. Quantitative reverse transcriptase-PCR (qRT-PCR) revealed that Tcal/Tcal mice had increased expression of Galnt3 and Fgf23 in bone, but that renal expression of Klotho, 25-hydroxyvitamin D-1α-hydroxylase (Cyp27b1), and the sodium-phosphate co-transporters type-IIa and -IIc was similar to that in wild-type mice. Thus, TCAL mice have the phenotypic features of FTC and HHS, and provide a model for these disorders of phosphate metabolism.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Primary defects of the E3 binding protein component of the pyruvate dehydrogenase complex appear to be a rare cause of pyruvate dehydrogenase deficiency. We describe two new, unrelated patients with ...mutations in the E3 binding protein gene, in both cases involving the conserved dinucleotides of splice junctions. Both patients presented with delayed development and lactic acidosis, features that are also found in patients with the more common pyruvate dehydrogenase E1 alpha subunit deficiency; however, they both had significant residual enzyme activity in cultured fibroblasts and prolonged survival.
A study was conducted to evaluate the association, if any, between mutations affecting G-protein subunit alpha11 in hypercalcemia and hypocalcemia. Results indicated that a relationship does exist ...between the two.
Context:
Genetic abnormalities, such as those of multiple endocrine neoplasia type 1 (MEN1) and Cyclin D1 (CCND1) genes, occur in <50% of nonhereditary (sporadic) parathyroid adenomas.
Objective:
To ...identify genetic abnormalities in nonhereditary parathyroid adenomas by whole-exome sequence analysis.
Design:
Whole-exome sequence analysis was performed on parathyroid adenomas and leukocyte DNA samples from 16 postmenopausal women without a family history of parathyroid tumors or MEN1 and in whom primary hyperparathyroidism due to single-gland disease was cured by surgery. Somatic variants confirmed in this discovery set were assessed in 24 other parathyroid adenomas.
Results:
Over 90% of targeted exons were captured and represented by more than 10 base reads. Analysis identified 212 somatic variants (median eight per tumor; range, 2–110), with the majority being heterozygous nonsynonymous single-nucleotide variants that predicted missense amino acid substitutions. Somatic MEN1 mutations occurred in six of 16 (∼35%) parathyroid adenomas, in association with loss of heterozygosity on chromosome 11. However, no other gene was mutated in more than one tumor. Mutations in several genes that may represent low-frequency driver mutations were identified, including a protection of telomeres 1 (POT1) mutation that resulted in exon skipping and disruption to the single-stranded DNA-binding domain, which may contribute to increased genomic instability and the observed high mutation rate in one tumor.
Conclusions:
Parathyroid adenomas typically harbor few somatic variants, consistent with their low proliferation rates. MEN1 mutation represents the major driver in sporadic parathyroid tumorigenesis although multiple low-frequency driver mutations likely account for tumors not harboring somatic MEN1 mutations.
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