Postmenopausal osteoporosis, a global public health problem, has for decades been attributed solely to declining estrogen levels. Although FSH levels rise sharply in parallel, a direct effect of FSH on the skeleton has never been explored. We show that FSH is required for hypogonadal bone loss. Neither FSHbeta nor FSH receptor (FSHR) null mice have bone loss despite severe hypogonadism. Bone mass is increased and osteoclastic resorption is decreased in haploinsufficient FSHbeta+/- mice with normal ovarian function, suggesting that the skeletal action of FSH is estrogen independent. Osteoclasts and their precursors possess G(i2alpha)-coupled FSHRs that activate MEK/Erk, NF-kappaB, and Akt to result in enhanced osteoclast formation and function. We suggest that high circulating FSH causes hypogonadal bone loss.

RNA is known to be an abundant and important structural component of the nuclear matrix, including long noncoding RNAs (lncRNA). Yet the molecular identities, functional roles, and localization dynamics of lncRNAs that influence nuclear architecture remain poorly understood. Here, we describe one lncRNA, Firre, that interacts with the nuclear matrix factor hnRNPU, through a 156 bp repeating sequence and Firre localizes across a ~5 Mb domain on the X-chromosome. We further observed Firre localization across at least five distinct trans-chromosomal loci, which reside in spatial proximity to the Firre genomic locus on the X-chromosome. Both genetic deletion of the Firre locus or knockdown of hnRNPU resulted in loss of co-localization of these trans-chromosomal interacting loci. Thus, our data suggest a model in which lncRNAs such as Firre can interface with and modulate nuclear architecture across chromosomes.

It is unclear how physical activity stimulates new bone synthesis. We explored whether irisin, a newly discovered myokine released upon physical activity, displays anabolic actions on the skeleton. Young male mice were injected with vehicle or recombinant irisin (r-irisin) at a low cumulative weekly dose of 100 µg kg(-1). We observed significant increases in cortical bone mass and strength, notably in cortical tissue mineral density, periosteal circumference, polar moment of inertia, and bending strength. This anabolic action was mediated primarily through the stimulation of bone formation, but with parallel notable reductions in osteoclast numbers. The trabecular compartment of the same bones was spared, as were vertebrae from the same mice. Higher irisin doses (3,500 µg kg(-1) per week) cause browning of adipose tissue; this was not seen with low-dose r-irisin. Expectedly, low-dose r-irisin modulated the skeletal genes, Opn and Sost, but not Ucp1 or Pparγ expression in white adipose tissue. In bone marrow stromal cell cultures, r-irisin rapidly phosphorylated Erk, and up-regulated Atf4, Runx2, Osx, Lrp5, β-catenin, Alp, and Col1a1; this is consistent with a direct receptor-mediated action to stimulate osteogenesis. We also noted that, although the irisin precursor Fndc5 was expressed abundantly in skeletal muscle, other sites, such as bone and brain, also expressed Fndc5, albeit at low levels. Furthermore, muscle fibers from r-irisin-injected mice displayed enhanced Fndc5 positivity, and irisin induced Fdnc5 mRNA expression in cultured myoblasts. Our data therefore highlight a previously unknown action of the myokine irisin, which may be the molecular entity responsible for muscle-bone connectivity

The prevalence of obesity has led to a surge of interest in understanding the detailed mechanisms underlying adipocyte development. Many protein-coding genes, mRNAs, and microRNAs have been implicated in adipocyte development, but the global expression patterns and functional contributions of long noncoding RNA (lncRNA) during adipogenesis have not been explored. Here we profiled the transcriptome of primary brown and white adipocytes, preadipocytes, and cultured adipocytes and identified 175 lncRNAs that are specifically regulated during adipogenesis. Many lncRNAs are adipose-enriched, strongly induced during adipogenesis, and bound at their promoters by key transcription factors such as peroxisome proliferator-activated receptor γ (PPARγ) and CCAAT/enhancer-binding protein α (CEBPα). RNAi-mediated loss of function screens identified functional lncRNAs with varying impact on adipogenesis. Collectively, we have identified numerous lncRNAs that are functionally required for proper adipogenesis.

Over the last two decades, we have extensively studied the genetics of congenital adrenal hyperplasia caused by 21-hydroxylase deficiency (CAH) and have performed 8,290 DNA analyses of the CYP21A2 gene on members of 4,857 families at risk for CAHthe largest cohort of CAH patients reported to date. Of the families studied, 1,507 had at least one member affected with one of three known forms of CAH, namely salt wasting, simple virilizing, or nonclassical CAH. Here, we report the genotype and phenotype of each affected patient, as well as the ethnic group and country of origin for each patient. We showed that 21 of 45 genotypes yielded a phenotypic correlation in our patient cohort. In particular, contrary to what is generally reported in the literature, we found that certain mutations, for example, the P30L, I2G, and I172N mutations, yielded different CAH phenotypes. In salt wasting and nonclassical CAH, a phenotype can be attributed to a genotype; however, in simple virilizing CAH, we observe wide phenotypic variability, particularly with the exon 4 I172N mutation. Finally, there was a high frequency of homozygous I2G and V281L mutations in Middle Eastern and Ashkenazi Jewish populations, respectively. By identifying the predominant phenotype for a given genotype, these findings should assist physicians in prenatal diagnosis and genetic counseling of parents who are at risk for having a child with CAH.pseudogene-derived mutations | genotype-phenotype association T he most common cause of congenital adrenal hyperplasia (CAH) is 21-hydroxylase deficiency (1). Phenotypically, CAH can be divided into classical and nonclassical (NC) forms, with the classical form presenting as salt-wasting (SW) or simple-virilizing (SV) CAH (1), both of which can result in genital ambiguity in the affected female. Mutations in the CYP21A2 gene cause varying degrees of loss of 21-hydroxylase activity, resulting in different severities. In vitro studies performed on a relatively limited number of mutations have confirmed a correlation between disease severity and the degree of functional loss of 21-hydroxylase. Mutations resulting in complete inactivation of 21-hydroxylase activity are associated with the SW phenotype. Those that reduce enzyme activity to ∼2% cause the SV phenotype, whereas those that reduce activity to between 10% and 75% result in the mild NC phenotype (2-12).We recently used computational modeling to correlate disease severity with 113 known mutations on the basis of the extent to which the enzyme is disrupted in silico (13). By humanizing the crystal structure of bovine CYP21A2, we found that mutations that affect critical enzyme functions, such as membrane anchoring, heme binding, and substrate binding, or alter enzyme stability result in a complete loss of functionality and SW disease. In contrast, mutations that affect the transmembrane region or conserved hydrophobic patches result in up to a 98% reduction in enzyme activity and SV disease. Mild NC disease arises from interference in oxidoreductase interactions,...

We report that oxytocin (OT), a primitive neurohypophyseal hormone, hitherto thought solely to modulate lactation and social bonding, is a direct regulator of bone mass. Deletion of OT or the OT receptor (Oxtr) in male or female mice causes osteoporosis resulting from reduced bone formation. Consistent with low bone formation, OT stimulates the differentiation of osteoblasts to a mineralizing phenotype by causing the up-regulation of BMP-2, which in turn controls Schnurri-2 and 3, Osterix, and ATF-4 expression. In contrast, OT has dual effects on the osteoclast. It stimulates osteoclast formation both directly, by activating NF-B and MAP kinase signaling, and indirectly through the up-regulation of RANK-L. On the other hand, OT inhibits bone resorption by mature osteoclasts by triggering cytosolic Ca 2؉ release and NO synthesis. Together, the complementary genetic and pharmacologic approaches reveal OT as a novel anabolic regulator of bone mass, with potential implications for osteoporosis therapy.osteoblast ͉ osteoclast ͉ osteoporosis ͉ pituitary hormones ͉ bone density O xytocin (OT), a hypothalamic nanopeptide secreted into the circulation from the posterior pituitary, is indispensable for lactation. It acts on a G protein-coupled receptor (Oxtr), the expression of which in reproductive tissues is regulated by sex steroids and OT. In humans and rodents, plasma OT levels are elevated maximally during suckling (1, 2).Mice lacking OT or its receptor (Oxtr) are unable to lactate, despite unperturbed breast tissue and milk formation (3, 4). Most notably, newborn pups die shortly after birth in the absence of a foster mother postpartum. This effect of OT is exerted peripherally, as the i.p. administration of recombinant OT to OT Ϫ/Ϫ mice rescues milk ejection, allowing the newborn to feed normally. In contrast to the milk ejection defect, no deficits in copulation, gestation, fecundity, or parturition have been noted in either OT Ϫ/Ϫ or Oxtr Ϫ/Ϫ mice, suggesting that these mice are typically eugonadal (5). Furthermore, compound mutants with both the Oxtr and the prostaglandin F2␣ receptor deleted exhibit no defects in parturition, indicating significant redundancy in the birth process per se (5). However, in view of the established pharmacology of circulating OT on the uterine myometrium, the possibility of a physiological action of OT during childbirth cannot be excluded, even without a loss-of-function phenotype.Two other key actions of OT warrant mention: effects on social , behavior and on the regulation of food intake. Male OT Ϫ/Ϫ and Oxtr Ϫ/Ϫ mice show deficits in social recognition, without altered cognition or olfactory learning. That this social amnesia is a central rather than a peripheral action of OT is supported by the observation that recombinant OT injected directly into the amygdala rescues the defect (6). Compared with males, female OT or Oxtr null mice display anxiety and exaggerated stress responses, which are likewise mediated through central OT-ergic neurones (7). OT also is involved in the reg...

Mammals have two principal types of fat. White adipose tissue (WAT) primarily serves to store extra energy as triglycerides, while brown adipose tissue (BAT) is specialized to burn lipids for heat generation and energy expenditure as a defense against cold and obesity 1, 2. Recent studies demonstrate that brown adipocytes arise in vivo from a Myf5-positive, myoblastic progenitor by the action of Prdm16 (PR domain containing 16). Here, we identified a brown fat-enriched miRNA cluster, miR-193b-365, as a key regulator of brown fat development. Blocking miR-193b and/or miR-365 in primary brown preadipocytes dramatically impaired brown adipocyte adipogenesis by enhancing Runx1t1 (runt-related transcription factor 1; translocated to, 1) expression whereas myogenic markers were significantly induced. Forced expression of miR-193b and/or miR-365 in C2C12 myoblasts blocked the entire program of myogenesis, and, in adipogenic condition, miR-193b induced myoblasts to differentiate into brown adipocytes. MiR-193b-365 was upregulated by Prdm16 partially through Pparα. Our results demonstrate that miR-193b-365 serves as an essential regulator for brown fat differentiation, in part by repressing myogenesis.

Menopause is associated with bone loss and enhanced visceral adiposity. We have shown previously that a polyclonal antibody (Ab) to the β-subunit of the pituitary hormone Fsh increases bone mass in mice. Here, we report that this Ab sharply reduces adipose tissue in wild type mice, phenocopying genetic Fshr haploinsufficiency. The Ab also causes profound beiging, increases cellular mitochondrial density, activates brown adipose tissue, and enhances thermogenesis. These actions result from the specific binding of Ab to Fshβ to block its action. Our studies uncover novel opportunities for co-treating obesity and osteoporosis.