Publications

2020
ENCODE PC, Snyder MP, Gingeras TR, Moore JE, Weng Z, Gerstein MB, Ren B, Hardison RC, Stamatoyannopoulos JA, Graveley BR, et al. Perspectives on ENCODE. Nature. 2020;583 (7818) :693-698.Abstract
The Encylopedia of DNA Elements (ENCODE) Project launched in 2003 with the long-term goal of developing a comprehensive map of functional elements in the human genome. These included genes, biochemical regions associated with gene regulation (for example, transcription factor binding sites, open chromatin, and histone marks) and transcript isoforms. The marks serve as sites for candidate cis-regulatory elements (cCREs) that may serve functional roles in regulating gene expression1. The project has been extended to model organisms, particularly the mouse. In the third phase of ENCODE, nearly a million and more than 300,000 cCRE annotations have been generated for human and mouse, respectively, and these have provided a valuable resource for the scientific community.
ENCODE PC, Moore JE, Purcaro MJ, Pratt HE, Epstein CB, Shoresh N, Adrian J, Kawli T, Davis CA, Dobin A, et al. Expanded encyclopaedias of DNA elements in the human and mouse genomes. Nature. 2020;583 (7818) :699-710.Abstract
The human and mouse genomes contain instructions that specify RNAs and proteins and govern the timing, magnitude, and cellular context of their production. To better delineate these elements, phase III of the Encyclopedia of DNA Elements (ENCODE) Project has expanded analysis of the cell and tissue repertoires of RNA transcription, chromatin structure and modification, DNA methylation, chromatin looping, and occupancy by transcription factors and RNA-binding proteins. Here we summarize these efforts, which have produced 5,992 new experimental datasets, including systematic determinations across mouse fetal development. All data are available through the ENCODE data portal (https://www.encodeproject.org), including phase II ENCODE1 and Roadmap Epigenomics2 data. We have developed a registry of 926,535 human and 339,815 mouse candidate cis-regulatory elements, covering 7.9 and 3.4% of their respective genomes, by integrating selected datatypes associated with gene regulation, and constructed a web-based server (SCREEN; http://screen.encodeproject.org) to provide flexible, user-defined access to this resource. Collectively, the ENCODE data and registry provide an expansive resource for the scientific community to build a better understanding of the organization and function of the human and mouse genomes.
2019
ahn SV, Lee JV, Bove-Fenderson E, Park SY, Mannstadt M, Lee S. Incidence of Hypoparathyroidism After Thyroid Cancer Surgery in South Korea, 2007-2016. Journal of the American Medical Association [Internet]. 2019;322 (24) :2441-2443. Publisher's VersionAbstract

In 1999, the SouthKorean government initiated a national cancer screening program, which led to increased high-resolution ultrasonography screening for thyroid cancer. Consequently,thyroid cancer incidence increased from7.2 per 100000 population in 1999 to 68.7 per 100000 population in 2011, and most patients received surgery. However,many screen-detected cancers were small and likely indolent. Concerns about overdiagnosis were raised beginning in2012, and ultrasonographic screening was discouraged in 2014, leading to decreased incidence of thyroid cancer and thyroidectomies. We assessed the changes in incidence rates of postoperative hypoparathyroidism, a complication of thyroidectomy, between 2007 and 2016.

jama_ahn_2019.pdf
Mannstadt M, Clarke BL, Bilezikian JP, Bone H, Denham D, Levine MA, Peacock M, Rothman J, Shoback DM, Warren ML, et al. Safety and Efficacy of 5 Years of Treatment With Recombinant Human Parathyroid Hormone in Adults With Hypoparathyroidism. Journal of Clinical Endocrinology & Metabolism [Internet]. 2019;104 (11) :5136–5147. Publisher's VersionAbstract

Context: Conventional treatment of hypoparathyroidism with oral calcium and active vitamin D is aimed at correcting hypocalcemia but does not address other physiologic defects caused by deficiency of parathyroid hormone (PTH).

Objective: To evaluate long-term safety and tolerability of recombinant human PTH(1-84) (rhPTH[1-84])

Design: Open-label extension study; 5-year interim analysis

Setting: 12 US centers

Patients: Adults (N=49) with chronic hypoparathyroidism

Intervention(s): Patients initially received rhPTH(1-84) 25 or 50 µg/day, with 25-µg adjustments permitted to 100 µg/day maximum.

Main Outcome Measure(s): Safety parameters; composite efficacy outcome was the proportion of patients with ≥50% reduction in oral calcium (or ≤500 mg/day) and calcitriol (or ≤0.25 µg/day) doses, and albumin-corrected serum calcium normalized or maintained compared with baseline, not exceeding upper limit of normal.

Results: Forty patients completed 60 months of treatment. Mean albumin-corrected serum calcium remained between 8.2 and 8.7 mg/dL. Between baseline and Month 60, urinary calcium decreased by 101.2±236.24 mg/24 hours, serum phosphorus decreased by 1.0±0.78 mg/dL, and calcium-phosphorus product decreased by 8.5±8.29 mg2/dL2. Serum creatinine and estimated glomerular filtration rate were unchanged. Treatment-emergent adverse events (AEs) were reported in 48 patients (98.0%; hypocalcemia, 36.7%; muscle spasms, 32.7%; paresthesia, 30.6%; sinusitis, 30.6%; nausea, 30.6%) and serious AEs in 13 (26.5%). At Month 60, 28/40 patients (70.0%) achieved the composite efficacy outcome. Bone turnover markers increased, peaked at approximately 12 months, and then declined to values that remained above baseline.

Conclusions: Treatment with rhPTH(1-84) for 5 years demonstrated a safety profile consistent with previous studies and improved key biochemical parameters.

Biebermann H, Kleinau G, Schnabel D, Bockenhauer D, Wilson LC, Tully I, Kiff S, Scheerer P, Reyes M, Paisdzior S, et al. A New Multisystem Disorder Caused by the Gαs Mutation p.F376V. Journal of Clinical Endocrinology & Metabolism [Internet]. 2019;104 (4) :1079-1089. Publisher's VersionAbstract

CONTEXT:

The α subunit of the stimulatory G protein (Gαs) links numerous receptors to adenylyl cyclase. Gαs, encoded by GNAS, is expressed predominantly from the maternal allele in certain tissues. Thus, maternal heterozygous loss-of-function mutations cause hormonal resistance, as in pseudohypoparathyroidism type Ia, whereas somatic gain-of-function mutations cause hormone-independent endocrine stimulation, as in McCune-Albright syndrome.

OBJECTIVE:

We report two unrelated boys presenting with a new combination of clinical findings that suggest both gain and loss of Gαs function.

DESIGN AND SETTING:

Clinical features were studied and sequencing of GNAS was performed. Signaling capacities of wild-type and mutant Gαs were determined in the presence of different G protein-coupled receptors (GPCRs) under basal and agonist-stimulated conditions.

RESULTS:

Both unrelated patients presented with unexplained hyponatremia in infancy, followed by severe early onset gonadotrophin-independent precocious puberty and skeletal abnormalities. An identical heterozygous de novo variant (c.1136T>G; p.F376V) was found on the maternal GNAS allele in both patients; this resulted in a clinical phenotype that differed from known Gαs-related diseases and suggested gain of function at the vasopressin 2 receptor (V2R) and lutropin/choriogonadotropin receptor (LHCGR), yet increased serum PTH concentrations indicative of impaired proximal tubular PTH1 receptor (PTH1R) function. In vitro studies demonstrated that Gαs-F376V enhanced ligand-independent signaling at the PTH1R, LHCGR, and V2R and, at the same time, blunted ligand-dependent responses. Structural homology modeling suggested mutation-induced modifications at the C-terminal α5 helix of Gαs that are relevant for interaction with GPCRs and signal transduction.

CONCLUSIONS:

The Gαs p.F376V mutation causes a previously unrecognized multisystem disorder.

2018
Haghighi A, Krier JB, Toth-Petroczy A, Cassa CA, Frank NY, Carmichael N, Fieg E, Bjonnes A, Mohanty A, Briere LC, et al. An integrated clinical program and crowdsourcing strategy for genomic sequencing and Mendelian disease gene discovery. NPJ Genomic Medicine [Internet]. 2018;3 (21) :eCollection. Publisher's VersionAbstract
Despite major progress in defining the genetic basis of Mendelian disorders, the molecular etiology of many cases remains unknown. Patients with these undiagnosed disorders often have complex presentations and require treatment by multiple health care specialists. Here, we describe an integrated clinical diagnostic and research program using whole-exome and whole-genome sequencing (WES/WGS) for Mendelian disease gene discovery. This program employs specific case ascertainment parameters, a WES/WGS computational analysis pipeline that is optimized for Mendelian disease gene discovery with variant callers tuned to specific inheritance modes, an interdisciplinary crowdsourcing strategy for genomic sequence analysis, matchmaking for additional cases, and integration of the findings regarding gene causality with the clinical management plan. The interdisciplinary gene discovery team includes clinical, computational, and experimental biomedical specialists who interact to identify the genetic etiology of the disease, and when so warranted, to devise improved or novel treatments for affected patients. This program effectively integrates the clinical and research missions of an academic medical center and affords both diagnostic and therapeutic options for patients suffering from genetic disease. It may therefore be germane to other academic medical institutions engaged in implementing genomic medicine programs.
Bove-Fenderson E, Mannstadt M. Hypocalcemic disorders. Best Practice & Research Clinical Endocrinology & Metabolism [Internet]. 2018;32 (5) :639-656. Publisher's VersionAbstract
Calcium is vital for life, and extracellular calcium concentrations must constantly be maintained within a precise concentration range. Low serum calcium (hypocalcemia) occurs in conjunction with multiple disorders and can be life-threatening if severe. Symptoms of acute hypocalcemia include neuromuscular irritability, tetany, and seizures, which are rapidly resolved with intravenous administration of calcium gluconate. However, disorders that lead to chronic hypocalcemia often have more subtle manifestations. Hypoparathyroidism, characterized by impaired secretion of parathyroid hormone (PTH), a key regulatory hormone for maintaining calcium homeostasis, is a classic cause of chronic hypocalcemia. Disorders that disrupt the metabolism of vitamin D can also lead to chronic hypocalcemia, as vitamin D is responsible for increasing the gut absorption of dietary calcium. Treatment and management options for chronic hypocalcemia vary depending on the underlying disorder. For example, in patients with hypoparathyroidism, calcium and vitamin D supplementation must be carefully titrated to avoid symptoms of hypocalcemia while keeping serum calcium in the low-normal range to minimize hypercalciuria, which can lead to renal dysfunction. Management of chronic hypocalcemia requires knowledge of the factors that influence the complex regulatory axes of calcium homeostasis in a given disorder. This chapter discusses common and rare disorders of hypocalcemia, symptoms and workup, and management options including replacement of PTH in hypoparathyroidism.
Biebermann H, Kleinau G, Schnabel D, Bockenhauer D, Wilson LC, Tully I, Kiff S, Scheerer P, Reyes M, Paisdzior S, et al. A new multi-system disorder caused by the Gαs mutation p.F376V. Journal of Clinical Endocrinology & Metabolism [Internet]. 2018. Publisher's VersionAbstract

CONTEXT:

The alpha-subunit of the stimulatory G-protein (Gαs) links numerous receptors to adenylyl cyclase. Gαs, encoded by GNAS, is expressed predominantly from the maternal allele in certain tissues. Thus, maternal heterozygous loss-of-function mutations cause hormonal resistance, as in pseudohypoparathyroidism type Ia, while somatic gain-of-function mutations cause hormone-independent endocrine stimulation, as in McCune-Albright Syndrome.

OBJECTIVE:

We here report two unrelated boys presenting with a new combination of clinical findings that suggest both gain and loss of Gαs function.

DESIGN, SETTING:

Clinical features were studied and sequencing of GNAS was performed. Signaling capacities of wild-type and mutant-Gαs were determined in the presence of different G protein-coupled receptors (GPCRs) under basal and agonist-stimulated conditions.

RESULTS:

Both unrelated patients presented with unexplained hyponatremia in infancy, followed by severe early-onset gonadotrophin-independent precocious puberty and skeletal abnormalities. An identical heterozygous de novo variant (c.1136T>G; p.F376V) was found on the maternal GNAS allele, in both patients; this resulted in a clinical phenotype that differ from known Gαs-related diseases and suggested gain-of-function at the receptors for vasopressin (V2R) and lutropin (LHCGR), yet increased serum parathyroid hormone (PTH) concentrations indicative of impaired proximal tubular PTH1 receptor (PTH1R) function. In vitro studies demonstrated that Gαs-F376V enhanced ligand-independent signaling at the PTH1R, LHCGR and V2R and, at the same time, blunted ligand-dependent responses. Structural homology modeling suggested mutation-induced modifications at the C-terminal α5-helix of Gαs that are relevant for interaction with GPCRs and signal transduction.

CONCLUSIONS:

The Gαs p.F376V mutation causes a previously unrecognized multi-system disorder.

Fan Y, Liu W, Bi R, Densmore MJ, Sato T, Mannstadt M, Yaun Q, Zhou X, Olauson H, Larsson TE, et al. Interrelated role of Klotho and calcium-sensing receptor in parathyroid hormone synthesis and parathyroid hyperplasia. Proceedings of the National Academy of Sciences of the United States of America [Internet]. 2018;115 (16) :E3749-E3758. Publisher's VersionAbstract

The pathogenesis of parathyroid gland hyperplasia is poorly understood, and a better understanding is essential if there is to be improvement over the current strategies for prevention and treatment of secondary hyperparathyroidism. Here we investigate the specific role of Klotho expressed in the parathyroid glands (PTGs) in mediating parathyroid hormone (PTH) and serum calcium homeostasis, as well as the potential interaction between calcium-sensing receptor (CaSR) and Klotho. We generated mouse strains with PTG-specific deletion of Klotho and CaSR and dual deletion of both genes. We show that ablating CaSR in the PTGs increases PTH synthesis, that Klotho has a pivotal role in suppressing PTH in the absence of CaSR, and that CaSR together with Klotho regulates PTH biosynthesis and PTG growth. We utilized the tdTomato gene in our mice to visualize and collect PTGs to reveal an inhibitory function of Klotho on PTG cell proliferation. Chronic hypocalcemia and ex vivo PTG culture demonstrated an independent role for Klotho in mediating PTH secretion. Moreover, we identify an interaction between PTG-expressed CaSR and Klotho. These findings reveal essential and interrelated functions for CaSR and Klotho during parathyroid hyperplasia.

Goltzman D, Mannstadt M, Marcocci C. Physiology of the Calcium-Parathyroid Hormone-Vitamin D Axis. Frontiers of Hormone Research [Internet]. 2018;50 :1-3. Publisher's VersionAbstract

Classic endocrine feedback loops ensure the regulation of blood calcium. Calcium in the extracellular fluid (ECF) binds and activates the calcium sensing receptor (CaSR) on the parathyroid cells, leading to an increase in intracellular calcium. This in turn leads to a reduced parathyroid hormone (PTH) release. Hypocalcemia leads to the opposite sequence of events, namely, lowered intracellular calcium and increased PTH production and secretion. PTH rapidly increases renal calcium reabsorption and, over hours to days, enhances osteoclastic bone resorption and liberates both calcium and phosphate from the skeleton. PTH also increases fibroblast growth factor 23 (FGF23) release from mature osteoblasts and osteocytes. PTH stimulates the renal conversion of 25-hydroxyvitamin D (25[OH]D) to 1,25(OH)2D, likely over several hours, which in turn will augment intestinal calcium absorption. Prolonged hypocalcemia and exposure to elevated PTH may also result in 1,25(OH)2D-mediated calcium and phosphorus release from bone. These effects restore the ECF calcium to normal and inhibit further production of PTH and 1,25(OH)2D. Additionally, FGF23 can be released from bone by 1,25(OH)2D and can in turn reduce 1,25(OH)2D concentrations. FGF23 has also been reported to decrease PTH production. When ECF calcium is in the hypercalcemic range, PTH secretion is reduced and renal 1,25(OH)2D production is decreased. In addition, the elevated calcium per se stimulates the renal CaSR, thus inducing calciuria. Therefore, suppression of PTH release and 1,25(OH)2D synthesis and stimulation of the renal CaSR lead to reduced renal calcium reabsorption, decreased skeletal calcium release, and decreased intestinal calcium absorption, resulting in the normalization of the elevated ECF calcium.

Bove-Fenderson E, Duffy K, Mannstadt M. Sharing the Wealth: ASBMR Journals Update Policies on Data Sharing and Data Repositories. Journal of Bone and Mineral Research [Internet]. 2018;33 (3) :369-370. Publisher's Version
Bove-Fenderson E, Duffy K, Mannstadt M. Broadening Our Horizons: JBMR and JBMR Plus Embrace Preprints. Journal of Bone and Mineral Research [Internet]. 2018;33 (2) :185-187. Publisher's Version
Vokes TJ, Mannstadt M, Levine MA, Clarke BL, Lakatos P, Chen K, Piccolo R, Krasner A, Shoback DM, Bilezikian JP. Recombinant Human Parathyroid Hormone Effect on Health-Related Quality of Life in Adults With Chronic Hypoparathyroidism. Journal of Clinical Endocrinology & Metabolism [Internet]. 2018;103 (2) :722-731. Publisher's VersionAbstract

CONTEXT:

Reduced health-related quality of life (HRQoL) is common in patients with hypoparathyroidism treated conventionally with calcium and active vitamin D supplements.

OBJECTIVE:

To examine the effects of recombinant human parathyroid hormone [rhPTH(1-84)] on HRQoL as measured by the 36-Item Short-Form Health Survey (SF-36) during a multinational, randomized, placebo-controlled study.

PATIENTS:

Adults (N = 122) with chronic hypoparathyroidism.

INTERVENTION(S):

After an optimization period when calcium and/or active vitamin D supplements were adjusted to reach target serum calcium levels (8.0 to 9.0 mg/dL; 2.0 to 2.2 mmol/L), patients were randomly assigned to receive placebo (n = 39) or rhPTH(1-84) (n = 83) (starting dose, 50 μg/d, could be titrated up to 100 μg/d); supplement doses were adjusted to maintain target serum calcium levels.

MAIN OUTCOME MEASURE(S):

Change from baseline (postoptimization, at randomization) to week 24 in HRQoL as assessed by the SF-36.

RESULTS:

Overall, the between-group differences were not statistically significant. However, in the rhPTH(1-84) group, there were significant improvements in the physical component summary score (P = 0.004), and in body pain (P < 0.05), general health (P < 0.05), and vitality (P < 0.001) domains as compared with baseline values. In the placebo group, there were no significant changes for any domains. The magnitude of change between 0 and 24 weeks in SF-36 scores was negatively correlated with baseline scores, such that patients with lower HRQoL at baseline were more likely to experience improvement in response to treatment.

CONCLUSION:

Treatment with rhPTH(1-84) may improve HRQoL in adults with hypoparathyroidism.

2017
Vokes TJ, Mannstadt M, Levine MA, Clarke BL, Lakatos P, Chen K, Piccolo R, Krasner A, Shoback DM, Bilezikian JP. Recombinant Human Parathyroid Hormone Effect on Health-Related Quality of Life in Adults With Chronic Hypoparathyroidism. Journal of Clinical Endocrinology & Metabolism [Internet]. 2017 :1-15. Publisher's VersionAbstract

CONTEXT:

Reduced health-related quality of life (HRQoL) is common in patients with hypoparathyroidism on conventional therapy with calcium and active vitamin D supplements.

OBJECTIVE:

To examine the effects of recombinant human parathyroid hormone (rhPTH[1-84]) on HRQoL as measured by the 36-Item Short Form Health Survey (SF-36) during the multinational, randomized, placebo-controlled REPLACE study.

PATIENTS:

122 adults with chronic hypoparathyroidism.

INTERVENTION(S):

Following an optimization period when calcium and/or active vitamin D supplements were adjusted to reach target serum calcium levels (8.0-9.0 mg/dL; 2.0-2.2 mmol/L), patients were randomized to receive placebo (n=39) or rhPTH(1-84) (n=83) (starting dose 50 μg/day, could be titrated up to 100 μg/day); supplement doses were adjusted to maintain target serum calcium levels.

MAIN OUTCOME MEASURE(S):

Change from baseline (post-optimization, at randomization) to Week 24 in HRQoL as assessed by the SF-36v2 health survey.

RESULTS:

Overall, the between-group differences were not statistically significant. However, in the rhPTH(1-84) group, there were significant improvements in the physical component summary score (P=0.004) and in body pain (P<0.05), general health (P<0.05), and vitality (P<0.001) domains as compared with baseline values. In the placebo group, there were no significant changes for any of the domains. The magnitude of change between 0 and 24 weeks in SF-36 scores was negatively correlated with baseline scores, such that patients with lower HRQoL at baseline were more likely to experience improvement in response to treatment.

CONCLUSIONS:

Treatment with rhPTH(1-84) may improve HRQoL in adults with hypoparathyroidism.

Mannstadt M, Bilezikian JP, Thakker RV, Hannan FM, Clarke BL, Reijnmark L, Mitchell DM, Vokes TJ, Winer KK, Shoback DM. Hypoparathyroidism. Nature Reviews Disease Primers [Internet]. 2017;3 :1-20. Publisher's VersionAbstract
Hypoparathyroidism is a disease characterized by inadequately low circulating concentrations of parathyroid hormone (PTH) resulting in low calcium levels and increased phosphate levels in the blood. Symptoms of the disease result from increased neuromuscular irritability caused by hypocalcaemia and include tingling, muscle cramps and seizures. The most common cause of the disease is inadvertent removal of, or injury to, the parathyroid glands during neck surgery, followed by genetic, idiopathic and autoimmune aetiologies. Conventional treatment includes activated vitamin D and/or calcium supplements, but this treatment does not fully replace the functions of PTH and can lead to short-term problems (such as hypocalcaemia, hypercalcaemia and increased urinary calcium excretion) and long-term complications (which include nephrocalcinosis, kidney stones and brain calcifications). PTH replacement has emerged as a new treatment option. Clinical trials using human PTH(1-34) and PTH(1-84) showed that this treatment was safe and effective in studies lasting up to 6 years. Recombinant human PTH(1-84) has been approved in the United States and Europe for the management of hypoparathyroidism; however, its effect on long-term complications is still being evaluated. Clinical practice guidelines, which describe the consensus of experts in the field, have been published and recognize the need for more research to optimize care. In this Primer, we summarize current knowledge of the prevalence, pathophysiology, clinical presentation and management of hypoparathyroidism.
Bi R, Fan Y, Yuan Q, Mannstadt M. Two Techniques to Create Hypoparathyroid Mice: Parathyroidectomy Using GFP Glands and Diphtheria-Toxin-Mediated Parathyroid Ablation. Journal of Visualized Experiments. 2017;(121) :1-6.Abstract

Hypoparathyroidism (HP) is a disorder characterized by low levels of PTH which lead to hypocalcemia, hyperphosphatemia, and low bone turnover. The most common cause of the disease is accidental removal of the parathyroid glands during thyroid surgery. Novel therapies for HP are needed, but testing them requires reliable animal models of acquired HP.

Here, we demonstrate the generation of two mouse models of acquired HP. In the GFP-PTX model, mice with green fluorescent protein (GFP) expressed specifically in the parathyroids (PTHcre-mTmG) were created by crossing PTHcre+ mice with Rosa-mTmGfl/fl mice. Green fluorescing parathyroid glands are easily identified under a fluorescence dissecting microscope and parathyroidectomy is performed in less than 20 min. After fluorescence-guided surgery, mice are profoundly hypocalcemic. Contrary to the traditional thyro-parathyroidectomy, this precise surgical approach leaves thyroid glands and thyroid function intact. The second model, which does not require surgery, is based on a diphtheria-toxin approach. PTHcre-iDTR mice, which express the diphtheria toxin (DT) receptor specifically in the parathyroids, were generated by crossing the inducible DTR mouse with the PTHcre mouse. Parathyroid cells are thus rendered sensitive to diphtheria toxin (DT) and can be selectively destroyed by systemically injecting mice with DT. The resulting hypocalcemic phenotype is stable.

jove-121-55010.pdf
Stephen AE, Mannstadt M, Hodin RA. Indications for Surgical Management of Hyperparathyroidism: A Review. JAMA Surgery Review. 2017 :E1 - E5.Abstract

IMPORTANCE: Primary hyperparathyroidism (pHPT) is a common clinical entity, with approximately 100 000 new cases diagnosed each year in the United States. Most patients with pHPT have a relatively mild form of the disease and present with few if any overt signs or symptoms. This has led to a dilemma regarding which patients should be considered for parathyroid surgery. In this article, we review the established literature on the indications for surgery in asymptomatic pHPT and discuss the most recent consensus conference guidelines.

OBSERVATIONS: The reviewed literature suggests that there were improved outcomes among patients with asymptomatic pHPT who underwent curative surgery.

CONCLUSIONS AND RELEVANCE: Most patients with pHPT should be considered for parathyroidectomy. More randomized clinical trials are needed to strongly support a surgical recommendation for all asymptomatic patients with pHPT.

jamasurgery_stephen_2017_rv_170005.pdf
Bi R, Yan Y, Luo E, Mannstadt M. Two Techniques to Create Hypoparathyroid Mice: Parathyroidectomy Using GFP Glandsand Diphtheria-Toxin-Mediated Parathyroid Ablation. Journal of Visualized Experiments [Internet]. 2017;(121) :1-6. Publisher's VersionAbstract

Hypoparathyroidism (HP) is a disorder characterized by low levels of PTH which lead to hypocalcemia, hyperphosphatemia, and low bone turnover. The most common cause of the disease is accidental removal of the parathyroid glands during thyroid surgery. Novel therapies for HP are needed, but testing them requires reliable animal models of acquired HP. Here, we demonstrate the generation of two mouse models of acquired HP. In the GFP-PTX model, mice with green fluorescent protein (GFP) expressed specifically in the parathyroids (PTHcre-mTmG) were created by crossing PTHcre+ mice with Rosa-mTmGfl/fl mice. Green fluorescing parathyroid glands are easily identified under a fluorescence dissecting microscope and parathyroidectomy is performed in less than 20 min. After fluorescence-guided surgery, mice are profoundly hypocalcemic. Contrary to the traditional thyro-parathyroidectomy, this precise surgical approach leaves thyroid glands and thyroid function intact. The second model, which does not require surgery, is based on a diphtheria-toxin approach. PTHcre-iDTR mice, which express the diphtheria toxin (DT) receptor specifically in the parathyroids, were generated by crossing the inducible DTR mouse with the PTHcre mouse. Parathyroid cells are thus rendered sensitive to diphtheria toxin (DT) and can be selectively destroyed by systemically injecting mice with DT. The resulting hypocalcemic phenotype is stable.

Roszko KL, Gorvin CM, Bräuner-Osborne H, Xiong XF, Inoue A, Thakker RV, Strømgaard K, Gardella T, Mannstadt M. Knockin mouse with mutant Gα11 mimics human inherited hypocalcemia and is rescued by pharmacologic inhibitors. JCI Insight [Internet]. 2017;2 (3) :1-15. Publisher's VersionAbstract

Heterotrimeric G proteins play critical roles in transducing extracellular signals generated by 7-transmembrane domain receptors. Somatic gain-of-function mutations in G protein α subunits are associated with a variety of diseases. Recently, we identified gain-of-function mutations in Gα11 in patients with autosomal-dominant hypocalcemia type 2 (ADH2), an inherited disorder of hypocalcemia, low parathyroid hormone (PTH), and hyperphosphatemia. We have generated knockin mice harboring the point mutation GNA11 c.C178T (p.Arg60Cys) identified in ADH2 patients. The mutant mice faithfully replicated human ADH2. They also exhibited low bone mineral density and increased skin pigmentation. Treatment with NPS 2143, a negative allosteric modulator of the calcium-sensing receptor (CASR), increased PTH and calcium concentrations in WT and mutant mice, suggesting that the gain-of-function effect of GNA11R6OC is partly dependent on coupling to the CASR. Treatment with the Gα11/q-specific inhibitor YM-254890 increased blood calcium in heterozygous but not in homozygous GNA11R60Cmice, consistent with published crystal structure data showing that Arg60 forms a critical contact with YM-254890. This animal model of ADH2 provides insights into molecular mechanism of this G protein-related disease and potential paths toward new lines of therapy.

Fan Y, Hanai J, Bi R, Maridas D, DeMambro V, Figueroa CA, Kir S, Zhou X, Mannstadt M, Baron R, et al. Parathyroid Hormone Directs Bone Marrow Mesenchymal Cell Fate. Cell Metabolism. 2017 :13.Abstract

Intermittent PTH administration builds bone mass and prevents fractures, but its mechanism of action is unclear. We genetically deleted the PTH/PTHrP receptor (PTH1R) in mesenchymal stem cells using Prx1Cre and found low bone formation, increased bone resorption, and high bone marrow adipose tissue (BMAT). Bone marrow adipocytes traced to Prx1 and expressed classic adipogenic markers and high receptor activator of nuclear factor kappa B ligand (Rankl) expression. RANKL levels were also elevated in bone marrow supernatant and serum, but undetectable in other adipose depots. By cell sorting, Pref1+RANKL+ marrow progenitors were twice as great in mutant versus control marrow. Intermittent PTH administration to control mice reduced BMAT significantly. A similar finding was noted in male osteoporotic patients. Thus, marrow adipocytes exhibit osteogenic and adipogenic characteristics, are uniquely responsive to PTH, and secrete RANKL. These studies reveal an important mechanism for PTH's therapeutic action through its ability to direct mesenchymal cell fate.

cell_metabolism_2017.pdf

Pages