Autosomal dominant hypoparathyroidism caused by germline mutation in GNA11: phenotypic and molecular characterization.

CONTEXT: Most cases of autosomal dominant hypoparathyroidism (ADH) are caused by gain-of-function mutations in CASR or dominant inhibitor mutations in GCM2 or PTH. OBJECTIVE: Our objectives were to identify the genetic basis for ADH in a multigenerational family and define the underlying disease mechanism. SUBJECTS: Here we evaluated a multigenerational family with ADH in which affected subjects had normal sequences in these genes and were shorter than unaffected family members. METHODS: We collected clinical and biochemical data from 6 of 11 affected subjects and performed whole-exome sequence analysis on DNA from two affected sisters and their affected father. Functional studies were performed after expression of wild-type and mutant Gα11 proteins in human embryonic kidney-293-CaR cells that stably express calcium-sensing receptors. RESULTS: Whole-exome-sequencing followed by Sanger sequencing revealed a heterozygous mutation, c.179G>T; p.R60L, in GNA11, which encodes the α-subunit of G11, the principal heterotrimeric G protein that couples calcium-sensing receptors to signal activation in parathyroid cells. Functional studies of Gα11 R60L showed increased accumulation of intracellular concentration of free calcium in response to extracellular concentration of free calcium with a significantly decreased EC50 compared with wild-type Gα11. By contrast, R60L was significantly less effective than the oncogenic Q209L form of Gα11 as an activator of the MAPK pathway. Compared to subjects with CASR mutations, patients with GNA11 mutations lacked hypercalciuria and had normal serum magnesium levels. CONCLUSIONS: Our findings indicate that the germline gain-of-function mutation of GNA11 is a cause of ADH and implicate a novel role for GNA11 in skeletal growth.

Generation of mice encoding a conditional null allele of Gcm2.

Glial cells missing homolog 2 (GCM2) is a transcription factor that is expressed predominately in the pharyngeal pouches and, at later stages, in the developing and mature parathyroid glands. In humans, loss of GCM2 function, either through recessive apomorphic mutations or dominant inhibitor mutations in the human GCM2 gene, leads to isolated hypoparathyroidism. In mice, homozygous disruption of Gcm2 by conventional gene targeting results in parathyroid aplasia and hypoparathyroidism. In this study, we report the generation and functional characterization of mice encoding a conditional null allele of Gcm2. We demonstrate the functional integrity of the conditional Gcm2 allele and report successful in vivo deletion of exon 2 using Cre recombinase. The mice with conditional deletion of Gcm2 displayed phenotypes similar to those previously described for a conventional Gcm2 knockout, including perinatal lethality, hypocalemia, low or undetectable serum levels of parathyroid hormone, and absent parathyroid glands. The production of a conditional mutant allele for Gcm2 represents a valuable resource for the study of the temporal- and spatial-specific roles for Gcm2, and for understanding the postnatal activities of GCM2 protein.

Identification of an anabolic selective androgen receptor modulator that actively induces death of androgen-independent prostate cancer cells.

Prostate cancer (PCa) initially responds to inhibition of androgen receptor (AR) signaling, but inevitably progresses to hormone ablation-resistant disease. Much effort is focused on optimizing this androgen deprivation strategy by improving hormone depletion and AR antagonism. However we found that bicalutamide, a clinically used antiandrogen, actually resembles a selective AR modulator (SARM), as it partially regulates 24% of endogenously 5α-dihydrotestosterone (DHT)-responsive genes in AR(+) MDA-MB-453 breast cancer cells. These data suggested that passive blocking of all AR functions is not required for PCa therapy. Hence, we adopted an active strategy that calls for the development of novel SARMs, which induce a unique gene expression profile that is intolerable to PCa cells. Therefore, we screened 3000 SARMs for the ability to arrest the androgen-independent growth of AR(+) 22Rv1 and LNCaP PCa cells but not AR(-) PC3 or DU145 cells. We identified only one such compound; the 4-aza-steroid, MK-4541, a potent and selective SARM. MK-4541 induces caspase-3 activity and cell death in both androgen-independent, AR(+) PCa cell lines but spares AR(-) cells or AR(+) non-PCa cells. This activity correlates with its promoter context- and cell-type dependent transcriptional effects. In rats, MK-4541 inhibits the trophic effects of DHT on the prostate, but not the levator ani muscle, and triggers an anabolic response in the periosteal compartment of bone. Therefore, MK-4541 has the potential to effectively manage prostatic hypertrophic diseases owing to its antitumor SARM-like mechanism, while simultaneously maintaining the anabolic benefits of natural androgens.

Discovery of the selective androgen receptor modulator MK-0773 using a rational development strategy based on differential transcriptional requirements for androgenic anabolism versus reproductive physiology.

Selective androgen receptor modulators (SARMs) are androgen receptor (AR) ligands that induce anabolism while having reduced effects in reproductive tissues. In various experimental contexts SARMs fully activate, partially activate, or even antagonize the AR, but how these complex activities translate into tissue selectivity is not known. Here, we probed receptor function using >1000 synthetic AR ligands. These compounds produced a spectrum of activities in each assay ranging from 0 to 100% of maximal response. By testing different classes of compounds in ovariectomized rats, we established that ligands that transactivated a model promoter 40-80% of an agonist, recruited the coactivator GRIP-1 <15%, and stabilized the N-/C-terminal interdomain interaction <7% induced bone formation with reduced effects in the uterus and in sebaceous glands. Using these criteria, multiple SARMs were synthesized including MK-0773, a 4-aza-steroid that exhibited tissue selectivity in humans. Thus, AR activated to moderate levels due to reduced cofactor recruitment, and N-/C-terminal interactions produce a fully anabolic response, whereas more complete receptor activation is required for reproductive effects. This bimodal activation provides a molecular basis for the development of SARMs.

Control of rat tail skin temperature regulation by estrogen receptor-beta selective ligand.

OBJECTIVE: To test the role of ERbeta in the control of estrogen-dependent thermoregulation in rats. METHODS: Test the ability of an ERbeta-selective ligand to suppress the elevation in basal rat tail skin temperature (TST) caused by ovariectomy (OVX). RESULTS: ERbeta-19 is a tetrahydrofluorenone ERbeta-selective ligand that displaces 0.1 nM estradiol from ERbeta with an IC50 of 1.8 nM compared to an IC50 of 141 nM for ERalpha. Like estradiol, it acts as an agonist on ERbeta-mediated transactivation and transrepression with 25- and 60-fold selectivity, respectively, over ERalpha-controlled transcription. Administration of estradiol to estrogen-depleted rats suppresses the ovariectomy-induced elevation of TST. Similar treatment of OVX rats with ERbeta-19 also results in suppression of elevated TST. However, in contrast to estradiol, ERbeta-19 does not suppress body weight, does not increase uterine weight, nor does it stimulate uterocalin biomarker expression which is under the control of ERalpha. Thus, the ERbeta-19 suppression of rat TST is mediated by ERbeta without eliciting the activity of ERalpha. CONCLUSION: Estrogen-sensitive thermoregulation in ovariectomized rats can be controlled by an ERbeta-selective ligand.

Estrogenic control of thermoregulation in ERalphaKO and ERbetaKO mice.

OBJECTIVE: Estrogen is the most effective treatment for preventing the vasomotor symptoms in women. The ability of estrogen to control tail skin temperature (TST) in rats is used as an animal model for the studies of estrogens on menopausal hot flushes. Today, we know that estrogen can mediate its actions via the interaction with two different estrogen receptors: ERalpha and ERbeta. To elucidate the function of each estrogen receptor subtype control of thermoregulation, we developed an animal model demonstrating estrogen control of TST in mice. METHODS AND RESULTS: We determined that estrogen depletion by ovariectomy (OVX) of mice causes an elevation of basal tail skin temperature. Administration of estradiol cypionate suppressed this increase in TST in a dose dependent manner. Estrogen depletion by OVX in either ERalpha-knockout (ERalphaKO) or ERbeta-knockout (ERbetaKO) mice resulted in an increase in TST that could be suppressed by estrogen treatment. CONCLUSION: We show that mice serve as a suitable animal model for estrogen-controlled thermoregulation and that the expression of either ERalpha or ERbeta alone in mice is sufficient to maintain control TST by estrogen.

Cross-talk between an activator of nuclear receptors-mediated transcription and the D1 dopamine receptor signaling pathway.

Nuclear receptors are transcription factors that usually interact, in a ligand-dependent manner, with specific DNA sequences located within promoters of target genes. The nuclear receptors can also be controlled in a ligand-independent manner via the action of membrane receptors and cellular signaling pathways. 5-Tetradecyloxy-2-furancarboxylic acid (TOFA) was shown to stimulate transcription from the MMTV promoter via chimeric receptors that consist of the DNA binding domain of GR and the ligand binding regions of the PPARbeta or LXRbeta nuclear receptors (GR/PPARbeta and GR/LXRbeta). TOFA and hydroxycholesterols also modulate transcription from NF-kappaB- and AP-1-controlled reporter genes and induce neurite differentiation in PC12 cells. In CV-1 cells that express D(1) dopamine receptors, D(1) dopamine receptor stimulation was found to inhibit TOFA-stimulated transcription from the MMTV promoter that is under the control of chimeric GR/PPARbeta and GR/LXRbeta receptors. Treatment with the D(1) dopamine receptor antagonist, SCH23390, prevented dopamine-mediated suppression of transcription, and by itself increased transcription controlled by GR/LXRbeta. Furthermore, combined treatment of CV-1 cells with TOFA and SCH23390 increased transcription controlled by the GR/LXRbeta chimeric receptor synergistically. The significance of this in vitro synergy was demonstrated in vivo, by the observation that SCH23390 (but not haloperidol)-mediated catalepsy in rats was potentiated by TOFA, thus showing that an agent that mimics the in vitro activities of compounds that activate members of the LXR and PPAR receptor families can influence D1 dopamine receptor elicited responses.

Rat tail skin temperature regulation by estrogen, phytoestrogens and tamoxifen.

OBJECTIVE: Develop a rat model for the evaluation of estrogenic agents on estrogen deficiency-induced changes in thermoregulation. METHODS: OVX rats are impaired in thermoregulation which manifests itself as an elevation in basal tail skin temperature (TST) and are less able to respond to temperature changes than intact rats. RESULTS: Administration of estrogen subcutaneously to estrogen-depleted rats either as depot formulation, biodegradable pellets, or daily injections, suppressed the increased TST. OVX rats maintained on a diet devoid of phytoestrogens had a higher TST by several degrees than OVX rats fed normal chow, offering greater ability to test estrogenic agents on thermoregulation. Depletion of estrogen in intact rats via chronic administration of leuprolide acetate, a GnRH agonist, also increased TST, which was in turn suppressed by estrogen. In intact rats, tamoxifen exhibited estrogen antagonistic activity elevating TST, while in OVX rats, tamoxifen acted as an agonist by suppressing TST. CONCLUSION: OVX rats kept on a diet devoid of phytoestrogens are a sensitive model for estrogen-dependent thermoregulation.