Expressions of Cushing’s syndrome in multiple endocrine neoplasia type 1

Cushing’s syndrome (CS) resulting from endogenous hypercortisolism can be sporadic or can occur in the context of familial disease because of pituitary or extra-pituitary neuroendocrine tumors. Multiple endocrine neoplasia type 1 (MEN1) is unique among familial endocrine tumor syndromes because hypercortisolism in this context can result from pituitary, adrenal, or thymic neuroendocrine tumors and can therefore reflect either ACTH-dependent or ACTH-independent pathophysiologies. The prominent expressions of MEN1 include primary hyperparathyroidism, tumors of the anterior pituitary, gastroenteropancreatic neuroendocrine tumors, and bronchial carcinoid tumors along with several common non-endocrine manifestations such as cutaneous angiofibromas and leiomyomas. Pituitary tumors are present in about 40% of MEN1 patients, and up to 10% of such tumors secrete ACTH that can result in Cushing’s disease. Adrenocortical neoplasms occur frequently in MEN1. Although such adrenal tumors are mostly clinically silent, this category can include benign or malignant tumors causing hypercortisolism and CS. Ectopic tumoral ACTH secretion has also been observed in MEN1, almost exclusively originating from thymic neuroendocrine tumors. The range of clinical presentations, etiologies, and diagnostic challenges of CS in MEN1 are reviewed herein with an emphasis on the medical literature since 1997, when the MEN1 gene was identified

Familial Syndromes of Primary Hyperparathyroidism

Regulation of serum calcium in vertebrates is maintained by the actions of the parathyroid glands working in concert with vitamin D and critical target tissues that include the renal tubules, the small intestine, and bone cells. The parathyroid glands release parathyroid hormone (PTH) into the systemic circulation as is required in order to maintain the serum calcium concentration within a narrow physiologic range. Excessive secretion of PTH from one or more abnormal parathyroid glands however results in primary hyperparathyroidism (HPT), a metabolic disease typically associated with abnormally elevated serum calcium. Although HPT is typically a sporadic disease, it can represent a manifestation of an inherited syndrome. Many sporadic parathyroid tumors result from inactivating mutations in tumor suppressor genes that were first discovered by the analysis of genomic DNA from patients with HPT as part of an inherited syndrome. Somatic and inherited alterations in DNA encoding proto-oncogenes can also cause parathyroid neoplasia. Two promising future approaches for the discovery of novel genes pertinent to parathyroid tumor development are the analysis of acquired genetic alterations in DNA isolated from parathyroid tumors and the investigation of familial HPT in kindreds lacking germline mutation in the known genes predisposing to HPT

The parafibromin tumor suppressor protein interacts with actin-binding proteins actinin-2 and actinin-3

<p>Abstract</p> <p>Background</p> <p>Germline and somatic inactivating mutations in the <it>HRPT2 </it>gene occur in the inherited hyperparathyroidism-jaw tumor syndrome, in some cases of parathyroid cancer and in some cases of familial hyperparathyroidism. <it>HRPT2 </it>encodes parafibromin. To identify parafibromin interacting proteins we used the yeast two-hybrid system for screening a heart cDNA library with parafibromin as the bait.</p> <p>Results</p> <p>Fourteen parafibromin interaction positive preys representing 10 independent clones encoding actinin-2 were isolated. Parafibromin interacted with muscle alpha-actinins (actinin-2 and actinin-3), but not with non-muscle alpha-actinins (actinin-1 and actinin-4). The parafibromin-actinin interaction was verified by yeast two-hybrid, GST pull-down, and co-immunoprecipitation. Yeast two-hybrid analysis revealed that the N-terminal region of parafibromin interacted with actinins. In actin sedimentation assays parafibromin did not dissociate skeletal muscle actinins from actin filaments, but interestingly, parafibromin could also bundle/cross-link actin filaments. Parafibromin was predominantly nuclear in undifferentiated proliferating myoblasts (C2C12 cells), but in differentiated C2C12 myotubes parafibromin co-localized with actinins in the cytoplasmic compartment.</p> <p>Conclusion</p> <p>These data support a possible contribution of parafibromin outside the nucleus through its interaction with actinins and actin bundling/cross-linking. These data also suggest that actinins (and actin) participate in sequestering parafibromin in the cytoplasmic compartment.</p

R7-binding protein targets the G protein β5/R7-regulator of G protein signaling complex to lipid rafts in neuronal cells and brain

<p>Abstract</p> <p>Background</p> <p>Heterotrimeric guanine nucleotide-binding regulatory proteins (G proteins), composed of Gα, Gβ, and Gγ subunits, are positioned at the inner face of the plasma membrane and relay signals from activated G protein-coupled cell surface receptors to various signaling pathways. Gβ5 is the most structurally divergent Gβ isoform and forms tight heterodimers with regulator of G protein signalling (RGS) proteins of the R7 subfamily (R7-RGS). The subcellular localization of Gβ 5/R7-RGS protein complexes is regulated by the palmitoylation status of the associated R7-binding protein (R7BP), a recently discovered SNARE-like protein. We investigate here whether R7BP controls the targeting of Gβ5/R7-RGS complexes to lipid rafts, cholesterol-rich membrane microdomains where conventional heterotrimeric G proteins and some effector proteins are concentrated in neurons and brain.</p> <p>Results</p> <p>We show that endogenous Gβ5/R7-RGS/R7BP protein complexes are present in native neuron-like PC12 cells and that a fraction is targeted to low-density, detergent-resistant membrane lipid rafts. The buoyant density of endogenous raft-associated Gβ5/R7-RGS protein complexes in PC12 cells was similar to that of lipid rafts containing the palmitoylated marker proteins PSD-95 and LAT, but distinct from that of the membrane microdomain where flotillin was localized. Overexpression of wild-type R7BP, but not its palmitoylation-deficient mutant, greatly enriched the fraction of endogenous Gβ5/R7-RGS protein complexes in the lipid rafts. In HEK-293 cells the palmitoylation status of R7BP also regulated the lipid raft targeting of co-expressed Gβ5/R7-RGS/R7BP proteins. A fraction of endogenous Gβ5/R7-RGS/R7BP complexes was also present in lipid rafts in mouse brain.</p> <p>Conclusion</p> <p>A fraction of Gβ5/R7-RGS/R7BP protein complexes is targeted to low-density, detergent-resistant membrane lipid rafts in PC12 cells and brain. In cultured cells, the palmitoylation status of R7BP regulated the lipid raft targeting of endogenous or co-expressed Gβ5/R7-RGS proteins. Taken together with recent evidence that the kinetic effects of the Gβ5 complex on GPCR signaling are greatly enhanced by R7BP palmitoylation through a membrane-anchoring mechanism, our data suggest the targeting of the Gβ5/R7-RGS/R7BP complex to lipid rafts in neurons and brain, where G proteins and their effectors are concentrated, may be central to the G protein regulatory function of the complex.</p

Patients with MEN1 are at an increased risk for venous thromboembolism VTE risk in MEN1

Background: Multiple endocrine neoplasia type 1 (MEN1) is a rare inherited disorder predisposing to the development of multiple functional and non-functional neuroendocrine tumors (NETs). Only uncommon MEN1-associated functional NETs such as glucagonomas (&lt;1%) and ACTH-producing tumors (&lt;5%) are known to be associated with hypercoagulability. It is unknown if patients with MEN1 generally have increased risk of VTE. Methods: We queried a prospective natural history study of germline mutation positive MEN1 patients (n=286) between 1991-2019 for all lifetime events of VTE. Search terms were: DVT, thromb, embol, PE, pulmonary embolism, clot, hematology consult, anticoagulant, coumadin, lovenox, xarelto, warfarin, aspirin, rivaroxaban and apixaban. Incidence rates were calculated accounting for age and sex. Comparison was made to published incidence rates in healthy populations, different types of cancer, and Cushing's syndrome. Results: Thirty-six subjects (median age 45 years, range 16-75) experienced a VTE event, yielding a prevalence rate of 12.9%. The age-sex adjusted incidence rate of VTE is 9.11 per 1,000 patient-years, with a sex-adjusted lifetime incidence rate of 2.81 per 1,000 patient-years. MEN1-associated lifetime incidence rates are ~two-fold higher than the estimated annual incidence rate in the general population and are comparable to known risk in the setting of various types of cancer. Approximately 80% were diagnosed with pancreatic NETs, of which 24% were insulinomas. Fourteen patients (42%) experienced peri-operative VTE events. Conclusions: MEN1 patients have an increased risk of VTE. Further mechanistic investigation and validation from other MEN1 cohorts are needed to confirm the increased prevalence of VTE in MEN1

GateFinder: projection-based gating strategy optimization for flow and mass cytometry

Motivation: High-parameter single-cell technologies can reveal novel cell populations of interest, but studying or validating these populations using lower-parameter methods remains challenging.Results: Here, we present GateFinder, an algorithm that enriches high-dimensional cell types with simple, stepwise polygon gates requiring only two markers at a time. A series of case studies of complex cell types illustrates how simplified enrichment strategies can enable more efficient assays, reveal novel biomarkers and clarify underlying biology

Inhibition of G-protein signalling in cardiac dysfunction of intellectual developmental disorder with cardiac arrhythmia (IDDCA) syndrome.

BACKGROUND: Pathogenic variants of GNB5 encoding the β5 subunit of the guanine nucleotide-binding protein cause IDDCA syndrome, an autosomal recessive neurodevelopmental disorder associated with cognitive disability and cardiac arrhythmia, particularly severe bradycardia. METHODS: We used echocardiography and telemetric ECG recordings to investigate consequences of Gnb5 loss in mouse. RESULTS: We delineated a key role of Gnb5 in heart sinus conduction and showed that Gnb5-inhibitory signalling is essential for parasympathetic control of heart rate (HR) and maintenance of the sympathovagal balance. Gnb5-/- mice were smaller and had a smaller heart than Gnb5+/+ and Gnb5+/- , but exhibited better cardiac function. Lower autonomic nervous system modulation through diminished parasympathetic control and greater sympathetic regulation resulted in a higher baseline HR in Gnb5-/- mice. In contrast, Gnb5-/- mice exhibited profound bradycardia on treatment with carbachol, while sympathetic modulation of the cardiac stimulation was not altered. Concordantly, transcriptome study pinpointed altered expression of genes involved in cardiac muscle contractility in atria and ventricles of knocked-out mice. Homozygous Gnb5 loss resulted in significantly higher frequencies of sinus arrhythmias. Moreover, we described 13 affected individuals, increasing the IDDCA cohort to 44 patients. CONCLUSIONS: Our data demonstrate that loss of negative regulation of the inhibitory G-protein signalling causes HR perturbations in Gnb5-/- mice, an effect mainly driven by impaired parasympathetic activity. We anticipate that unravelling the mechanism of Gnb5 signalling in the autonomic control of the heart will pave the way for future drug screening

Familial isolated hyperparathyroidism

The investigation of familial isolated hyperparathyroidism (FIHP) has been greatly facilitated in recent years by the identification of the genes responsible for most cases of syndromic familial hyperparathyroidism (HPT). Kindreds with apparently isolated hyperparathyroidism have been evaluated with clinical, biochemical, imaging and gene mutational tests designed to recognize multiple endocrine neoplasia type 1 (MEN1), the hyperparathyroidism-jaw tumor syndrome (HPTJT), and familial hypocalciuric hypercalcemia (FHH). Approximately 100 kindreds with the apparent diagnosis of FIHP were studied in clinical series that included screening by germline DNA mutational testing of one or more of the genes for these three syndromes since 1997. Of these provisionally diagnosed FIHP kindreds, some 10 to 20% had occult MEN1 and roughly 10% each had unrecognized HPT-JT or an FHH-related disorder evidenced by mutation of the calcium sensing receptor. Thus nearly 70% of FIHP kindreds are apparently non-syndromic. Even accounting for the likely underestimation in this group of syndromic causes for familial HPT due to shortcomings in current clinical and gene mutational testing methods, this finding suggests the majority of FIHP kindreds have no currently recognized syndromic etiology. Further study of this subset of carefully evaluated and apparently non-syndromic FIHP kindreds should assist in the identification of novel gene(s) important for neoplasia in the parathyroid and whose mutation can result in the FIHP phenotyp

Geochemical and Geophysical Examination of Submarine Groundwater Discharge and Associated Nutrient Loading Estimates into Lynch Cove, Hood Canal, WA

Geochemical tracer data (i.e., 222Rn and four naturally occurring Ra isotopes), electromagnetic (EM) seepage meter results, and high-resolution, stationary electrical resistivity images were used to examine the bi-directional (i.e., submarine groundwater discharge and recharge) exchange of a coastal aquifer with seawater. Our study site for these experiments was Lynch Cove, the terminus of Hood Canal, WA, where fjord-like conditions dramatically limit water column circulation that can lead to recurring summer-time hypoxic events. In such a system a precise nutrient budget may be particularly sensitive to groundwater-derived nutrient loading. Shore-perpendicular time-series subsurface resistivity profiles show clear, decimeter-scale tidal modulation of the coastal aquifer in response to large, regional hydraulic gradients, hydrologically transmissive glacial terrain, and large (4-5 m) tidal amplitudes. A 5-day 222Rn time-series shows a strong inverse covariance between 222Rn activities (0.5−29 dpm L-1) and water level fluctuations, and provides compelling evidence for tidally modulated exchange of groundwater across the sediment/water interface. Mean Rn-derived submarine groundwater discharge (SGD) rates of 85 ± 84 cm d-1 agree closely in the timing and magnitude with EM seepage meter results that showed discharge during low tide and recharge during high tide events. To evaluate the importance of fresh versus saline SGD, Rn-derived SGD rates (as a proxy of total SGD) were compared to excess 226Ra-derived SGD rates (as a proxy for the saline contribution of SGD). The calculated SGD rates, which include a significant (\u3e80%) component of recycled seawater, are used to estimate associated nutrient (NH4+, Si, PO43-, NO3 + NO2, TDN) loads to Lynch Cove. The dissolved inorganic nitrogen (DIN = NH4 + NO2 + NO3) SGD loading estimate of 5.9 × 104 mol d-1 is 1−2 orders of magnitude larger than similar estimates derived from atmospheric deposition and surface water runoff, respectively