Phenotype of Parathyroid-targeted Cdc73 Deletion in Mice Is Strain-dependent.

Hyperparathyroidism jaw-tumor syndrome is an autosomal dominant disorder caused by mutations in the CDC73/HRPT2 tumor suppressor gene, encoding parafibromin, and manifesting benign or malignant parathyroid tumors, ossifying jaw fibromas, uterine tumors, and kidney lesions. Sporadic parathyroid carcinomas also frequently exhibit inactivating CDC73 mutations and loss of parafibromin. To study the role of CDC73 in parathyroid cell proliferation in vivo, we generated mice with a parathyroid-specific deletion of Cdc73. Homozygous knockout mice on a mixed B6/129/CD1 background had decreased serum calcium and PTH and smaller parathyroid glands compared with heterozygous or wild-type littermates, whereas homozygous Cdc73-null mice on other backgrounds exhibited no abnormalities in parathyroid gland function or development. No hypercalcemia or parathyroid hypercellularity was observed in mice of any background examined at any age. Thus, although postnatally acquired complete loss of CDC73 causes parathyroid cell proliferation and hyperparathyroidism, such as seen in human hyperparathyroidism jaw-tumor syndrome, our results suggest that earlier, developmentally imposed complete loss of Cdc73 can cause a primary defect in parathyroid gland structure/function in a strain-dependent manner. This striking disparity in parathyroid phenotype related to genetic background offers a unique opportunity in an in vivo model system to precisely dissect and identify the responsible molecular mechanisms.

Influence of Vitamin D Deficiency on Cyclin D1-Induced Parathyroid Tumorigenesis.

Primary hyperparathyroidism (PHPT) is a common endocrinopathy for which several pathogenic mechanisms, including cyclin D1 overexpression, have been identified. Vitamin D nutritional status may influence parathyroid tumorigenesis, but evidence remains circumstantial. To assess the potential influence of vitamin D insufficiency/deficiency on initiation or progression of parathyroid tumorigenesis, we superimposed vitamin D insufficiency or deficiency on parathyroid tumor-prone parathyroid hormone-cyclin D1 transgenic mice. Mice were placed on diets containing either 2.75 IU/g, 0.25 IU/g, or 0.05 IU/g cholecalciferol, either prior to expected onset of PHPT or after onset of biochemical PHPT. When introduced early, superimposed vitamin D insufficiency/deficiency had no effect on serum calcium or on parathyroid gland growth. However, when introduced after the onset of biochemical PHPT, vitamin D deficiency led to larger parathyroid glands without differences in serum biochemical parameters. Our results suggest that low vitamin D status enhances proliferation of parathyroid cells whose growth is already being tumorigenically driven, in contrast to its apparent lack of direct proliferation-initiating action on normally growing parathyroid cells in this model. These results are consistent with the hypothesis that suboptimal vitamin D status may not increase incidence of de novo parathyroid tumorigenesis but may accelerate growth of a preexisting parathyroid tumor.

Epidemiology, Pathophysiology, and Genetics of Primary Hyperparathyroidism.

In this narrative review, we present data gathered over four decades (1980-2020) on the epidemiology, pathophysiology and genetics of primary hyperparathyroidism (PHPT). PHPT is typically a disease of postmenopausal women, but its prevalence and incidence vary globally and depend on a number of factors, the most important being the availability to measure serum calcium and parathyroid hormone levels for screening. In the Western world, the change in presentation to asymptomatic PHPT is likely to occur, over time also, in Eastern regions. The selection of the population to be screened will, of course, affect the epidemiological data (ie, general practice as opposed to tertiary center). Parathyroid hormone has a pivotal role in regulating calcium homeostasis; small changes in extracellular Ca++ concentrations are detected by parathyroid cells, which express calcium-sensing receptors (CaSRs). Clonally dysregulated overgrowth of one or more parathyroid glands together with reduced expression of CaSRs is the most important pathophysiologic basis of PHPT. The spectrum of skeletal disease reflects different degrees of dysregulated bone remodeling. Intestinal calcium hyperabsorption together with increased bone resorption lead to increased filtered load of calcium that, in addition to other metabolic factors, predispose to the appearance of calcium-containing kidney stones. A genetic basis of PHPT can be identified in about 10% of all cases. These may occur as a part of multiple endocrine neoplasia syndromes (MEN1-MEN4), or the hyperparathyroidism jaw-tumor syndrome, or it may be caused by nonsyndromic isolated endocrinopathy, such as familial isolated PHPT and neonatal severe hyperparathyroidism. DNA testing may have value in: confirming the clinical diagnosis in a proband; eg, by distinguishing PHPT from familial hypocalciuric hypercalcemia (FHH). Mutation-specific carrier testing can be performed on a proband's relatives and identify where the proband is a mutation carrier, ruling out phenocopies that may confound the diagnosis; and potentially prevention via prenatal/preimplantation diagnosis. © 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

GCM2 Variants in Familial and Multiglandular Primary Hyperparathyroidism.

CONTEXT: Multiglandular and familial parathyroid disease constitute important fractions of primary hyperparathyroidism (PHPT). Germline missense variants of GCM2, a regulator of parathyroid development, were observed in familial isolated hyperparathyroidism and sporadic PHPT. However, as these previously reported GCM2 variants occur at relatively high frequencies in the population, understanding their potential clinical utility will require both additional penetrance data and functional evidence relevant to tumorigenicity. OBJECTIVE: Determine the frequency of GCM2 variants of interest among patients with sporadic multigland or familial parathyroid disease and assess their penetrance. DESIGN AND PATIENTS: DNA-encoding PHPT-associated GCM2 germline variants were polymerase chain reaction-amplified and sequenced from 107 patients with either sporadic multigland or suspected/confirmed familial parathyroid tumors. RESULTS: GCM2 variants were observed in 9 of 107 cases (8.4%): Y282D in 4 patients (6.3%) with sporadic multigland disease; Y394S in 2 patients (11.1%) with familial PHPT and 3 (4.8%) with sporadic multigland disease. Compared with the general population, Y282D was enriched 5.9-fold in multigland disease, but its penetrance was very low (0.02%). Y394S was enriched 79-fold in sporadic multigland disease and 93-fold in familial PHPT, but its penetrance was low (1.33% and 1.04%, respectively). CONCLUSIONS: Observed in vitro-activating GCM2 variant alleles are significantly overrepresented in PHPT patients with multiglandular or familial disease compared to the general population, yet penetrance values are very low; that is, most individuals with these variants in the population have a very low risk of developing PHPT. The potential clinical utility of detecting these GCM2 variants requires further investigation, including assessing their possible role as pathogenic/low-penetrance alleles.

Mutations in EPHB4 cause human venous valve aplasia.

Venous valve (VV) failure causes chronic venous insufficiency, but the molecular regulation of valve development is poorly understood. A primary lymphatic anomaly, caused by mutations in the receptor tyrosine kinase EPHB4, was recently described, with these patients also presenting with venous insufficiency. Whether the venous anomalies are the result of an effect on VVs is not known. VV formation requires complex "organization" of valve-forming endothelial cells, including their reorientation perpendicular to the direction of blood flow. Using quantitative ultrasound, we identified substantial VV aplasia and deep venous reflux in patients with mutations in EPHB4. We used a GFP reporter in mice to study expression of its ligand, ephrinB2, and analyzed developmental phenotypes after conditional deletion of floxed Ephb4 and Efnb2 alleles. EphB4 and ephrinB2 expression patterns were dynamically regulated around organizing valve-forming cells. Efnb2 deletion disrupted the normal endothelial expression patterns of the gap junction proteins connexin37 and connexin43 (both required for normal valve development) around reorientating valve-forming cells and produced deficient valve-forming cell elongation, reorientation, polarity, and proliferation. Ephb4 was also required for valve-forming cell organization and subsequent growth of the valve leaflets. These results uncover a potentially novel cause of primary human VV aplasia.

Parafibromin Abnormalities in Ossifying Fibroma.

Ossifying fibromas are very rare tumors that are sometimes seen as part of the hyperparathyroidism-jaw tumor syndrome (HPT-JT), which is caused by inactivating mutations of the HRPT2/CDC73 tumor suppressor gene. CDC73 mutations have been identified in a subset of sporadic cases but aberrant expression of the encoded protein, parafibromin, has not been demonstrated in ossifying fibroma. We sought to determine if loss of parafibromin regularly contributes to the development of sporadic, nonsyndromic ossifying fibroma. We examined a series of 9 ossifying fibromas, including ossifying, cemento-ossifying, and juvenile active variants, for parafibromin protein expression by immunohistochemistry and for CDC73 sequence abnormalities by Sanger sequencing and/or targeted AmpliSeq panel sequencing. Four ossifying fibromas showed a complete absence of nuclear parafibromin expression; loss of parafibromin expression was coupled with aberrant cytoplasmic parafibromin expression in 1 case. CDC73 mutations were detected in 2 cases with aberrant parafibromin expression. These results provide novel evidence, at the level of protein expression, that loss of the parathyroid CDC73/parafibromin tumor suppressor may play a role in the pathogenesis of a subset of ossifying fibromas.

Editor's Choice - A Comparison of Computed Tomography Angiography and Colour Duplex Ultrasound Surveillance Post Infrarenal Endovascular Aortic Aneurysm Repair: Financial Implications and Impact of Different International Surveillance Guidelines.

OBJECTIVE: Use of colour duplex ultrasound (CDUS) and computed tomography angiography (CTA) for infrarenal endovascular aortic aneurysm repair (EVAR) surveillance differs in internationally published guidelines. This study aimed firstly to compare CDUS detection of significant sac abnormalities with CTA. Secondly, a sensitivity analysis was conducted to compare financial estimates of the, predominantly CDUS based, local and Society of Vascular Surgery (SVS) protocols, the risk stratified European Society of Vascular Surgery (ESVS) protocol, and the CTA based National Institute of Health and Care Excellence (NICE) protocol. METHODS: Agreement between CDUS and CTA was assessed for detection of significant sac abnormalities. Surveillance protocols were extrapolated from published guidelines and applied to infrarenal EVAR patients active on local surveillance at a large, single centre. Surveillance intensity was dependent on presence of endoleak and subsequent risk of treatment failure in accordance with surveillance recommendations. Estimates for each surveillance protocol were inclusive of a range of published incidences of endoleak, contrast associated acute kidney injury (AKI), and excess hospital bed days, and estimated for a hypothetical five year surveillance period. RESULTS: The kappa coefficient between CDUS and CTA for detecting sac abnormalities was 0.68. Maximum five year surveillance cost estimates for the 289 active EVAR patients were £272 359 for SVS, £230 708 for ESVS, £643 802 for NICE, and £266 777 for local protocols, or £1 270, £1 076, £3 003, and £1 244 per patient. Differences in endoleak incidence accounted for a 1.1 to 1.4 fold increase in costs. AKI incidence accounted for a 3.3 to 6.2 fold increase in costs. CONCLUSION: A combined CTA and CDUS EVAR surveillance protocol, with CTA reserved for early seal assessment and confirmatory purposes, provides an economical approach without compromising detection of sac abnormalities. AKI, as opposed to direct imaging costs, accounted for the largest differences in surveillance cost estimates.

Molecular analysis of cyclin D1 modulators PRKN and FBX4 as candidate tumor suppressors in sporadic parathyroid adenomas.

OBJECTIVE: Primary hyperparathyroidism is most often caused by a sporadic single-gland parathyroid adenoma (PTA), a tumor type for which cyclin D1 is the only known and experimentally validated oncoprotein. However, the molecular origins of its frequent overexpression have remained mostly elusive. In this study, we explored a potential tumorigenic mechanism that could increase cyclin D1 stability through a defect in molecules responsible for its degradation. METHODS: We examined two tumor suppressor genes known to modulate cyclin D1 ubiquitination, PRKN and FBXO4 (FBX4), for evidence of classic two-hit tumor suppressor inactivation within a cohort of 82 PTA cases. We examined the cohort for intragenic inactivating and splice site mutations by Sanger sequencing and for locus-associated loss of heterozygosity (LOH) by microsatellite analysis. RESULTS: We identified no evidence of bi-allelic tumor suppressor inactivation of PRKN or FBXO4 via inactivating mutation or splice site perturbation, neither in combination with nor independent of LOH. Among the 82 cases, we encountered previously documented benign single nucleotide polymorphisms (SNPs) in 35 tumors at frequencies similar to those reported in the germlines of the general population. Eight cases exhibited intragenic LOH at the PRKN locus, in some cases extending to cover at least an additional 1.7 Mb of chromosome 6q25-26. FBXO4 was not affected by LOH. CONCLUSION: The absence of evidence for specific bi-allelic inactivation in PRKN and FBXO4 in this sizeable cohort suggests that these genes only rarely, if ever, serve as classic driver tumor suppressors responsible for the growth of PTAs.

Oculocardiac Reflex During ROP Exams.

PURPOSE: Reducing physiologic stress including bradycardia during staging eye exams for retinopathy of prematurity (ROP) is desirable. We observed heart rate change during routine retinopathy of prematurity eye examinations and compared the response with our ongoing study of oculocardiac reflex (OCR) elicited by uniform EOM tension during strabismus surgery. PATIENTS AND METHODS: Electrocardiograph was prospectively monitored during ROP exams featuring indirect ophthalmoscopy with Alfonso lid speculum and see-through scleral depressor without topical anesthesia. Clinical data were retrieved from ROP-Check software. OCR was defined as maximally changed heart rate (HR) as a percent of baseline. Strabismus surgery patients under general anesthesia served as controls. RESULTS: From 10/2017 to 9/2020, 281 infants had ROP exams, and the median OCR was 55.9% of baseline HR (IQR 41.4% to 72.6%), the kurtosis 0.93 and skewness 1.01 representing a drop from HR 169 ± 16 bpm to 102 ± 39 bpm. In comparison, 1493 adult and pediatric strabismus surgery patients had less OCR median bradycardia 87.8% (IQR 72-98%), kurtosis 1.60 and skewness -1.18. ROP %OCR correlated with birth gestational age (%OCR = 2.5 (GA) - 11, r(279)=0.33, p<0.01) and with birthweight (%OCR = 0.02 (BW) + 38, r(279) =0.35, p<0.01). The duration of bradycardia induced by ROP exam averaged 92 ± 34 seconds (range 34-240 seconds). CONCLUSION: Bradycardia is common during eye exams in the smallest premature infants with greater degree, more rapid onset and longer duration than OCR during strabismus surgery.

The Impact of Re-Operation, Relatives and Race on the Oculocardiac Reflex During Strabismus Surgery.

PURPOSE: The oculocardiac reflex (OCR) is a trigeminovagal bradycardia elicited by tension on an extraocular muscle (EOM). Using three decades of observational data, we investigated whether or not individual strabismus patients are prone to oculocardiac reflex. PATIENTS AND METHODS: All patients undergoing strabismus surgery from 1992 to 2019 had deliberate 10-second, 200-gram square-wave tension on extraocular rectus muscles with anesthetic variables recorded. OCR was defined as the maximally tension-altered heart rate as a percent of stable baseline heart rate. RESULTS: OCR was compared in 2532 original cases with 323 re-operations. The 169 cases that used anticholinergics (99% OCR) were excluded from the analysis. The median OCR, a 15% drop, was found to be 85% (95% CI 39%, 102%,; range 5-151%). Factors that showed a significant effect on the OCR were the type of EOM with lateral rectus least (Kruskal-Wallis X2(3)=8, p<0.05), and adults had less OCR compared to the children (X2(2)=105, p<0.01). Factors that showed an augmenting effect on the OCR were peri-operative opioids (X2(6)=62, p<0.01) and Caucasian race (X2(4)=12, p<0.02). Gender and iris color were not found to have an impact on OCR. Re-operations and first-degree relatives did not differ from age-matched controls, but EOM- and opioid-adjusted re-operations correlated with their initial cases (r=0.37). CONCLUSION: We confirmed the previously published blocking effect of atropine, augmenting impact of opioids, and an inverse relationship of age on OCR. There was a weak proclivity for individuals to be prone to OCR. We found an impact of race with Caucasians having more OCR.

CDK4/6 Dependence of Cyclin D1-Driven Parathyroid Neoplasia in Transgenic Mice.

The protein product of the cyclin D1 oncogene functions by activating partner cyclin-dependent kinases (cdk)4 or cdk6 to phosphorylate, thereby inactivating, the retinoblastoma protein pRB. Nonclassical, cdk-independent, functions of cyclin D1 have been described but their role in cyclin D1-driven neoplasia, with attendant implications for recently approved cdk4/6 chemotherapeutic inhibitors, requires further examination. We investigated whether cyclin D1's role in parathyroid tumorigenesis in vivo is effected primarily through kinase-dependent or kinase-independent mechanisms. Using a mouse model of cyclin D1-driven parathyroid tumorigenesis (PTH-D1), we generated new transgenic lines harboring a mutant cyclin D1 (KE) that is unable to activate its partner kinases. While this kinase-dead KE mutant effectively drove mammary tumorigenesis in an analogous model, parathyroid-overexpressed cyclin D1 KE mice did not develop the characteristic biochemical hyperparathyroidism or parathyroid hypercellularity of PTH-D1 mice. These results strongly suggest that in parathyroid cells, cyclin D1 drives tumorigenesis predominantly through cdk-dependent mechanisms, in marked contrast with the cdk-independence of cyclin D1-driven mouse mammary cancer. These findings highlight crucial tissue-specific mechanistic differences in cyclin D1-driven tumorigenesis, suggest that parathyroid/endocrine cells may be more tumorigenically vulnerable to acquired genetic perturbations in cdk-mediated proliferative control than other tissues, and carry important considerations for therapeutic intervention.

PIK3CA Mutational Analysis of Parathyroid Adenomas.

Benign parathyroid adenoma is the most common cause of primary hyperparathyroidism, whereas malignant parathyroid carcinoma is exceedingly rare. Distinguishing parathyroid carcinoma from benign adenoma is often difficult, and may be considerably delayed even after surgical resection until the rigorous diagnostic criteria of local invasion of surrounding tissues and/or distant metastases are fulfilled. Thus, new insights into their respective molecular bases may potentially aid in earlier diagnostic discrimination between the two, as well as informing new directions for treatment. In two recent studies, gain-of-function mutations in PIK3CA, a recognized driver oncogene in many human malignancies, have been newly identified in parathyroid carcinoma. To assess the potential specificity for malignant, as opposed to benign parathyroid disease, of PIK3CA hotspot mutations, we PCR-amplified and Sanger sequenced codons 111, 542/545, and 1047 and the immediate flanking regions in genomic DNA from 391 typical, sporadic parathyroid adenomas. Four parathyroid adenomas (1%) had subclonal, somatic, heterozygous, activating PIK3CA mutations. The rarity of PIK3CA activating mutations in benign parathyroid adenomas suggests that tumorigenic activation of PIK3CA is strongly associated with malignant parathyroid neoplasia. However, it does not appear that such mutations, at least in isolation, can be relied upon for definitive molecular diagnosis of parathyroid carcinoma. © 2020 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

HEREDITARY ENDOCRINE TUMOURS: CURRENT STATE-OF-THE-ART AND RESEARCH OPPORTUNITIES: New and future perspectives for parathyroid carcinoma.

This report summarizes published data on parathyroid cancer, with the inclusion of topics discussed at MEN2019: 16th International Workshop on Multiple Endocrine Neoplasia, 27-29 March 2019, Houston, TX, USA. An expert panel on parathyroid cancer was constituted by the Steering Committee to address key questions in the field. The objectives were to recap open forum discussion of interested parties from multiple disciplines. The expert panel met in a closed session to consult on the data to be highlighted on the evidence-based results and on the future directions. Preceding the Conference, members of the expert panel conducted an extensive literature search. All presentations were based upon the best peer-reviewed information taking into account the historical and current literature. Questions were developed by the expert panel on parathyroid carcinoma. A comprehensive literature search for relevant studies was undertaken. This report represents the expert panel's synthesis of the conference material placed in a context designed to be relevant to clinicians and those engaged in cutting-edge studies of parathyroid carcinoma. This document not only provides a summary of our current knowledge but also places recent advances in its management into a context that should enhance future advances in our understanding of parathyroid carcinoma.

Direct OPTOS Nerve Size Determination of Prevalent Optic Nerve Hypoplasia in Alaska.

BACKGROUND: Optic nerve hypoplasia (ONH), one of the most common causes of pediatric blindness in developed countries, has been difficult to directly quantify. We sought to measure optic nerve size in Alaskan pediatric patients with optic nerve hypoplasia using ultra-widefield fundus imaging. METHODS: Adult and pediatric patients underwent conventional ultra widefield fundus imaging (OPTOS, Dunfermline, Scotland) with manual image processing to determine optic nerve size validated against refractive error and nystagmus and compared to optical spectral domain tomography. De-identified cases were then compared relative to visual acuity and birth prevalence. RESULTS: In Alaska's only pediatric ophthalmology outreach clinic, 108 cases of ONH less than 20 years old were clinically identified with 80 having ultra-widefield analysis. Median horizontal optic nerve diameter for 135 normals was 1.70 (95% C.I. 1.49, 2.14) whereas in patients clinically diagnosed with optic nerve hypoplasia was 1.23 (95% C.I 0.38, 1.45). Visual acuity (20/y) was related to horizontal optic nerve diameter (x) by y = 187 x-4.1. Horizontal nerve diameter h could be estimated from vertical nerve diameter v by h = 0.73v + 0.3 even in nystagmus patients. From 108 with ONH, 6 had threshold retinopathy of prematurity, 12 profound nystagmus, 32 legally blind, 6 with septo-optic dysplasia, and 5 with fetal alcohol syndrome. ONH is very prevalent in Alaska occurring at least 8-10 per 10,000 births. CONCLUSION: Compared to vertical diameter, horizontal diameter was more distinctive of optic nerve hypoplasia and more perturbed by nystagmus. Both were independent of refractive error. When hand-held, spectral domain OCT is not convenient, ultra-widefield fundus analysis is recommended for direct estimation of optic nerve size in children and adults. Optic nerve hypoplasia is prevalent in Alaskan children.

Extraordinary Radiation Hardness of Atomically Thin MoS2.

We demonstrate that atomically thin layered two-dimensional (2D) semiconductors are promising candidates for space electronics owing to their inherent and extraordinary resilience to radiation damage from energetic heavy charged particles. In particular, we found that ultrathin MoS2 nanosheets can easily withstand proton and helium irradiation with fluences as high as ∼1016 and ∼1015 ions/cm2, respectively, corresponding to hundreds or thousands of years of unshielded exposure to radiation in space. While radiation effects on 2D material-based field effect transistors have been reported in the recent past, none of these studies could isolate the impact of irradiation on standalone ultrathin 2D layers. By adopting a unique experimental approach that exploits the van der Waals epitaxy of 2D materials, we were able to differentiate the effects of radiation on the 2D semiconducting channel from that of the underlying dielectric substrate, semiconductor/substrate interface, and metal/semiconductor contact interface, revealing the ultimate potential of these 2D materials. Furthermore, we used a statistical approach to evaluate the effect of radiation damage on critical device and material parameters, including threshold voltage, subthreshold slope, and carrier mobility. The statistical approach lends additional credence to the general conclusions drawn from this study, overcoming a common drawback of methods applied in this area of research. Our findings do not only offer exciting prospects for the operation of modern electronics in space, but may also benefit electronics applications in high-altitude flights, military aircraft, satellites, nuclear reactors, particle accelerators, and other high-radiation environments. Additionally, they highlight the importance of evaluating the impact of damage to the substrate and surrounding materials on electrical characteristics during future radiation studies of 2D materials.

Analysis of Activating GCM2 Sequence Variants in Sporadic Parathyroid Adenomas.

CONTEXT: Sporadic, solitary parathyroid adenoma is the most common cause of primary hyperparathyroidism (PHPT). Apart from germline variants in certain cyclin-dependent kinase inhibitor genes and occasionally in MEN1, CASR, or CDC73, little is known about possible genetic variants in the population that may confer increased risk for development of typical sporadic adenoma. Transcriptionally activating germline variants, especially within in the C-terminal conserved inhibitory domain (CCID) of glial cells missing 2 (GCM2), encoding a transcription factor required for parathyroid gland development, have recently been reported in association with familial and sporadic PHPT. OBJECTIVE: To evaluate the potential role of specific GCM2 activating variants in sporadic parathyroid adenoma. DESIGN AND PATIENTS: Regions encoding hyperparathyroidism-associated, activating GCM2 variants were PCR amplified and sequenced in genomic DNA from 396, otherwise unselected, cases of sporadic parathyroid adenoma. RESULTS: Activating GCM2 CCID variants (p.V382M and p.Y394S) were identified in six of 396 adenomas (1.52%), and a hyperparathyroidism-associated GCM2 non-CCID activating variant (p.Y282D) was found in 20 adenomas (5.05%). The overall frequency of tested activating GCM2 variants in this study was 6.57%, approximately threefold greater than their frequency in the general population. CONCLUSIONS: The examined, rare CCID variants in GCM2 were enriched in our cohort of patients and appear to confer a moderately increased risk of developing sporadic solitary parathyroid adenoma compared with the general population. However, penetrance of these variants is low, suggesting that the large majority of individuals with such variants will not develop a sporadic parathyroid adenoma.

Molecular genetic insights into sporadic primary hyperparathyroidism.

Primary hyperparathyroidism (PHPT) is a common endocrine disorder characterized by dysregulation of parathyroid hormone release. The large majority of PHPT cases are attributable to sporadic, single-gland parathyroid adenoma, in which MEN1 and CCND1/cyclin D1 are the most well-established drivers of tumorigenesis. Sporadic parathyroid carcinoma, which appears to mostly arise through molecular pathways distinct from those causing benign parathyroid tumors, is rare and is most frequently driven by mutational inactivation of the CDC73 (HRPT2) tumor suppressor gene. Targeted investigation of suspected tumor driver genes, as well as unbiased whole-genome or exome sequencing of small cohorts, have revealed additional novel candidate tumor genes in sporadic parathyroid neoplasia, generally at modest or low mutational frequencies consistent with marked molecular genetic heterogeneity from tumor to tumor. The ability of these additional candidates to participate in the pathogenic process of driving parathyroid tumorigenesis in vivo largely remains to be demonstrated experimentally. This review will summarize the molecular genetic abnormalities identified to date in sporadic PHPT and discuss the strength of evidence for their proposed roles in parathyroid tumor formation.

Mutational Analysis of ZFY in Sporadic Parathyroid Adenomas.

CONTEXT: The molecular pathogenesis of sporadic parathyroid adenomas is incompletely understood, with alterations in cyclin D1/PRAD1 and MEN1 most firmly established as genetic drivers. The gene encoding the X-linked zinc finger protein (ZFX) has recently been implicated in the pathogenesis of a subset of parathyroid adenomas after recurrent, hotspot-focused somatic mutations were identified. ZFX escapes X inactivation and is transcribed from both alleles in women, and a highly homologous gene encoding the Y-linked zinc finger protein (ZFY) provides dosage compensation in males. OBJECTIVE: We sought to investigate the role of ZFY mutation in sporadic parathyroid adenoma. INTERVENTION: Polymerase chain reaction and Sanger sequencing were used to examine DNA from typically presenting, sporadic (nonfamilial, nonsyndromic) parathyroid adenomas from male patients for mutations within the ZFY gene. RESULTS: No mutations were identified among 117 adenomas. CONCLUSIONS: The absence of ZFY mutations in this series suggests that ZFY rarely, if ever, acts as a driver oncogene in sporadic parathyroid adenomas. The apparent differences in tumorigenic capabilities between the closely related zinc finger proteins ZFX and ZFY suggest that structure-function studies could represent an opportunity to gain insight into neoplastic processes in the parathyroid glands.

Insights into beta cell regeneration for diabetes via integration of molecular landscapes in human insulinomas.

Although diabetes results in part from a deficiency of normal pancreatic beta cells, inducing human beta cells to regenerate is difficult. Reasoning that insulinomas hold the "genomic recipe" for beta cell expansion, we surveyed 38 human insulinomas to obtain insights into therapeutic pathways for beta cell regeneration. An integrative analysis of whole-exome and RNA-sequencing data was employed to extensively characterize the genomic and molecular landscape of insulinomas relative to normal beta cells. Here, we show at the pathway level that the majority of the insulinomas display mutations, copy number variants and/or dysregulation of epigenetic modifying genes, most prominently in the polycomb and trithorax families. Importantly, these processes are coupled to co-expression network modules associated with cell proliferation, revealing candidates for inducing beta cell regeneration. Validation of key computational predictions supports the concept that understanding the molecular complexity of insulinoma may be a valuable approach to diabetes drug discovery.Diabetes results in part from a deficiency of functional pancreatic beta cells. Here, the authors study the genomic and epigenetic landscapes of human insulinomas to gain insight into possible pathways for therapeutic beta cell regeneration, highlighting epigenetic genes and pathways.

Genomic profiling reveals mutational landscape in parathyroid carcinomas.

Parathyroid carcinoma (PC) is an extremely rare malignancy lacking effective therapeutic intervention. We generated and analyzed whole-exome sequencing data from 17 patients to identify somatic and germline genetic alterations. A panel of selected genes was sequenced in a 7-tumor expansion cohort. We show that 47% (8 of 17) of the tumors harbor somatic mutations in the CDC73 tumor suppressor, with germline inactivating variants in 4 of the 8 patients. The PI3K/AKT/mTOR pathway was altered in 21% of the 24 cases, revealing a major oncogenic pathway in PC. We observed CCND1 amplification in 29% of the 17 patients, and a previously unreported recurrent mutation in putative kinase ADCK1. We identified the first sporadic PCs with somatic mutations in the Wnt canonical pathway, complementing previously described epigenetic mechanisms mediating Wnt activation. This is the largest genomic sequencing study of PC, and represents major progress toward a full molecular characterization of this rare malignancy to inform improved and individualized treatments.