Novel Roles of Follistatin/Myostatin in Transforming Growth Factor-β Signaling and Adipose Browning: Potential for Therapeutic Intervention in Obesity Related Metabolic Disorders

Obesity is a global health problem and a major risk factor for several metabolic conditions including dyslipidemia, diabetes, insulin resistance and cardiovascular diseases. Obesity develops from chronic imbalance between energy intake and energy expenditure. Stimulation of cellular energy burning process has the potential to dissipate excess calories in the form of heat via the activation of uncoupling protein-1 (UCP1) in white and brown adipose tissues. Recent studies have shown that activation of transforming growth factor-β (TGF-β) signaling pathway significantly contributes to the development of obesity, and blockade or inhibition is reported to protect from obesity by promoting white adipose browning and increasing mitochondrial biogenesis. Identification of novel compounds that activate beige/brown adipose characteristics to burn surplus calories and reduce excess storage of fat are actively sought in the fight against obesity. In this review, we present recent developments in our understanding of key modulators of TGF-β signaling pathways including follistatin (FST) and myostatin (MST) in regulating adipose browning and brown adipose mass and activity. While MST is a key ligand for TGF-β family, FST can bind and regulate biological activity of several TGF-β superfamily members including activins, bone morphogenic proteins (BMP) and inhibins. Here, we review the literature supporting the critical roles for FST, MST and other proteins in modulating TGF-β signaling to influence beige and brown adipose characteristics. We further review the potential therapeutic utility of FST for the treatment of obesity and related metabolic disorders.

Circulating myokine levels in different stages of glucose intolerance

Type 2 diabetes is the fastest growing metabolic disease in the world. Recently, muscle is considered an endocrine organ which secretes various peptides that play an important role in insulin resistance and metabolic syndrome. We assessed 4 different myokines, irisin, interleukin-13 (IL-13), follistatin-related protein-1 (FSTL-1), and fractalkine, in normal, prediabetes, and diabetes patients.A total of 126 participants who visited Gangnam Severance Hospital were enrolled and divided into normal, prediabetes, and diabetes groups based on oral glucose tolerance test and hemoglobin a1c. A cross-sectional study was conducted to measure and compare serum levels of irisin, IL-13, FSTL-1, and fractalkine among the groups.Irisin level showed a tendency to increase in prediabetes group compared to normal group (P < .1) but showed a significant decrease when comparing diabetes from prediabetes group (P < .001). IL-13 decreased in diabetes group compared to prediabetes and normal group (P < .001, P < .05, respectively). FSTL-1 of diabetes group was lower than that of prediabetes group (P < .05), and fractalkine was higher in diabetes group compared to that of prediabetes and normal group (P < .01, P < .01, respectively).Irisin, IL-13, and FSTL-1 levels were reduced in diabetes group compared to normal or prediabetes group while fractalkine showed a progressive increase from normal to diabetes group. Further studies are warranted to study the roles of various myokine in diabetes through a larger prospective study.

The glycoprotein follistatin-like 1 promotes brown adipose thermogenesis

OBJECTIVES

The thermogenic brown adipose tissue (BAT) has been proposed as a potential target to prevent or treat obesity and related metabolic diseases. BAT secretes adipokines to regulate the thermogenic program in an autocrine or paracrine manner. Follistatin-like 1 (FSTL1), a glycoprotein involved in adipogenesis and obesity, however, the function of FSTL1 in BAT thermogenesis and in the regulation of systemic energy homeostasis are not fully understood.

METHODS

Whole-body ablation Fstl1 heterozygous mice (Fstl1^+/-) and its littermates control were injected with CL316,243 to assess energy balance. A series of FSTL1 overexpression and knockdown experiments were carried out to evaluate its function in regulating thermogenic gene expression in brown adipocytes.

RESULTS

FSTL1 expression was induced upon BAT activation during cold challenge or β3-adrenergic activation. FSTL1 haploinsufficiency in mice led to reduced thermogenic gene expression, impaired BAT recruitment, and decreased heat production. FSTL1 cell-autonomously promoted the β3-adrenergic signaling, which was required to upregulate PPARγ and UCP1 in brown adipocytes. Furthermore, only glycosylated FSTL1 could be secreted from brown adipocytes to induce the β3-adrenergic activation.

CONCLUSIONS

Our results suggest FSTL1 as a novel stimulator of the β-adrenergic signaling and BAT thermogenesis.

Up-Regulation of Follistatin-Like 1 By the Androgen Receptor and Melanoma Antigen-A11 in Prostate Cancer

BACKGROUND

High affinity androgen binding to the androgen receptor (AR) activates genes required for male sex differentiation and promotes the development and progression of prostate cancer. Human AR transcriptional activity involves interactions with coregulatory proteins that include primate-specific melanoma antigen-A11 (MAGE-A11), a coactivator that increases AR transcriptional activity during prostate cancer progression to castration-resistant/recurrent prostate cancer (CRPC).

METHODS

Microarray analysis and quantitative RT-PCR were performed to identify androgen-regulated MAGE-A11-dependent genes in LAPC-4 prostate cancer cells after lentivirus shRNA knockdown of MAGE-A11. Chromatin immunoprecipitation was used to assess androgen-dependent AR recruitment, and immunocytochemistry to localize an androgen-dependent protein in prostate cancer cells and tissue and in the CWR22 human prostate cancer xenograft.

RESULTS

Microarray analysis of androgen-treated LAPC-4 prostate cancer cells indicated follistatin-like 1 (FSTL1) is up-regulated by MAGE-A11. Androgen-dependent up-regulation of FSTL1 was inhibited in LAPC-4 cells by lentivirus shRNA knockdown of AR or MAGE-A11. Chromatin immunoprecipitation demonstrated AR recruitment to intron 10 of the FSTL1 gene that contains a classical consensus androgen response element. Increased levels of FSTL1 protein in LAPC-4 cells correlated with higher levels of MAGE-A11 relative to other prostate cancer cells. FSTL1 mRNA levels increased in CRPC and castration-recurrent CWR22 xenografts in association with predominantly nuclear FSTL1. Increased nuclear localization of FSTL1 in prostate cancer was suggested by predominantly cytoplasmic FSTL1 in benign prostate epithelial cells and predominantly nuclear FSTL1 in epithelial cells in CRPC tissue and the castration-recurrent CWR22 xenograft. AR expression studies showed nuclear colocalization of AR and endogenous FSTL1 in response to androgen.

CONCLUSION

AR and MAGE-A11 cooperate in the up-regulation of FSTL1 to promote growth and progression of CRPC. Prostate 77:505-516, 2017. © 2016 Wiley Periodicals, Inc.

A genetic polymorphism affects the risk and prognosis of renal cell carcinoma: association with follistatin-like protein 1 expression

Few single nucleotide polymorphisms (SNPs) associated with the risk of renal cell carcinoma (RCC) have been identified, yet genetic predisposition contributes significantly to this malignancy. We previously showed that follistatin-like 1 (FSTL1) was significantly down-regulated in clear cell RCC (ccRCC), in particular metastatic ccRCC. In the present study, we systemically investigated the associations of the 6 SNPs within FSTL1-coding genomic region with RCC risk and postoperative prognosis. Age- and gender-matched case-control study (417 vs 855) indicated that rs1259293 variant genotype CC was significantly associated with an increased risk of RCC, with an odds ratio of 2.004 (95% confidence internal [CI] = 1.190-3.375). Multivariate Cox regression analysis in 309 of 417 cases showed that rs1259293 genotype (CC vs TT + CT) independently predicted an unfavorable prognosis, with a hazard ratio of 2.531 (95% CI = 1.052-6.086). Expression of FSTL1 was significantly higher in adjacent renal tissues than in tumors, and significantly higher in the tissues with rs1259293 TT genotype than in those with rs1259293 TC+CC genotypes. rs1259293 C allele might generate a CTCF binding site that blocks trans-activation of FSTL1 expression. Our results indicate that rs1259293 is associated with an increased risk and unfavorable postoperative prognosis of RCC, possibly by down-regulating FSTL1 expression in renal tissues.

[mRNA expression of Follistatin and follistatin-like 3, bone morphogenetic protein-4 antagonists in lung tissues of hypoxic mice]

OBJECTIVE

To observe the expression changes of Follistatin (FSN) and follistatin-like 3 (FSRP) mRNA, both of bone morphogenetic protein-4(BMP4) antagonists, in mice lung tissue under different hypoxic time and its relation with BMP4.

METHODS

Thirty BMP4+/+ C57BL/6J wild type mice were randomly divided into normoxic control group, and 4 groups including 1 day, 3 days, 7 days and 21 days under hypoxic condition. The hypoxic animal model was established by exposing the mice to hypoxic condition for different time. The expressing level of FSN and FSRP mRNA in lung tissues were measured by Quantitative Real-Time PCR.

RESULTS

FSN and FSRP mRNA increased in hypoxic 1 day group as (28.0 ± 9.4) and (2.0 ± 0.4), in hypoxic 3 day group, FSN mRNA increased by (6.3 ± 3.2) and FSRP mRNA by (1.67 ± 0.7) (P < 0. 05). Compared with the normoxic group (1.77 ± 0.36) and (1.22 ± 0.15) (P < 0. 01), FSN and FSRP mRNA up-regulated in hypoxic 7 day group. The positive degree of FSN and FSRP mRNA in hypoxic 21 day group were (1.04 ± 0.27) and (0.85 ± 0.10) (P < 0. 05). In normoxic 1 day group, FSN mRNA of lung tissues of BMP4+/- C57BL/6J mice was (0.95 ± 0.05); FSRP mRNA was (1.11 ± 0.03) (P < 0. 05). In BMP4+/- C57BL/6J mice lung tissues, FSN mRNA were (1.10 ± 0.40) (P < 0. 05); FSRP mRNA were (0.85 ± 0.18).

CONCLUSIONS

The expression of FSN and FSRP mRNA in hypoxic 1;3;7 day mice lung tissues increased obviously, and FSN may play an important role in the hypoxic pulmonary hypertension through BMP4.

Therapeutic impact of follistatin-like 1 on myocardial ischemic injury in preclinical models

BACKGROUND

Acute coronary syndrome is a leading cause of death in developed countries. Follistatin-like 1 (FSTL1) is a myocyte-derived secreted protein that is upregulated in the heart in response to ischemic insult. Here, we investigated the therapeutic impact of FSTL1 on acute cardiac injury in small and large preclinical animal models of ischemia/reperfusion and dissected its molecular mechanism.

METHODS AND RESULTS

Administration of human FSTL1 protein significantly attenuated myocardial infarct size in a mouse or pig model of ischemia/reperfusion, which was associated with a reduction of apoptosis and inflammatory responses in the ischemic heart. Administration of FSTL1 enhanced the phosphorylation of AMP-activated protein kinase in the ischemia/reperfusion-injured heart. In cultured cardiac myocytes, FSTL1 suppressed apoptosis in response to hypoxia/reoxygenation and lipopolysaccharide-stimulated expression of proinflammatory genes through its ability to activate AMP-activated protein kinase. Ischemia/reperfusion led to enhancement of bone morphogenetic protein-4 expression and Smad1/5/8 phosphorylation in the heart, and FSTL1 suppressed the increased phosphorylation of Smad1/5/8 in ischemic myocardium. Treating cardiac myocytes with FSTL1 abolished the bone morphogenetic protein-4-stimulated increase in apoptosis, Smad1/5/8 phosphorylation, and proinflammatory gene expression. In cultured macrophages, FSTL1 diminished lipopolysaccharide-stimulated expression of proinflammatory genes via activation of AMP-activated protein kinase and abolished bone morphogenetic protein-4-dependent induction of proinflammatory mediators.

CONCLUSIONS

Our data indicate that FSTL1 can prevent myocardial ischemia/reperfusion injury by inhibiting apoptosis and inflammatory response through modulation of AMP-activated protein kinase- and bone morphogenetic protein-4-dependent mechanisms, suggesting that FSTL1 could represent a novel therapeutic target for post-myocardial infarction, acute coronary syndrome.

Growth differentiation factor 9 (GDF9) suppresses follistatin and follistatin-like 3 production in human granulosa-lutein cells

Background

We have demonstrated that growth differentiation factor 9 (GDF9) enhances activin A-induced inhibin β_B-subunit mRNA levels in human granulosa-lutein (hGL) cells by regulating receptors and key intracellular components of the activin signaling pathway. However, we could not exclude its effects on follistatin (FST) and follistatin-like 3 (FSTL3), well recognized extracellular inhibitors of activin A.

Methodology

hGL cells from women undergoing in vitro fertilization (IVF) treatment were cultured with and without siRNA transfection of FST, FSTL3 or GDF9 and then treated with GDF9, activin A, FST, FSTL3 or combinations. FST, FSTL3 and inhibin β_B-subunit mRNA, and FST, FSTL3 and inhibin B protein levels were assessed with real-time RT-PCR and ELISA, respectively. Data were log transformed before ANOVA followed by Tukey's test.

Principal Findings

GDF9 suppressed basal FST and FSTL3 mRNA and protein levels in a time- and dose-dependent manner and inhibited activin A-induced FST and FSTL3 mRNA and protein expression, effects attenuated by BMPR2 extracellular domain (BMPR2 ECD), a GDF9 antagonist. After GDF9 siRNA transfection, basal and activin A-induced FST and FSTL3 mRNA and protein levels increased, but changes were reversed by adding GDF9. Reduced endogenous FST or FSTL3 expression with corresponding siRNA transfection augmented activin A-induced inhibin β_B-subunit mRNA levels as well as inhibin B levels (P values all <0.05). Furthermore, the enhancing effects of GDF9 in activin A-induced inhibin β_B-subunit mRNA and inhibin B production were attenuated by adding FST.

Conclusion

GDF9 decreases basal and activin A-induced FST and FSTL3 expression, and this explains, in part, its enhancing effects on activin A-induced inhibin β_B-subunit mRNA expression and inhibin B production in hGL cells.

Activin-A and myostatin response and steroid regulation in human myometrium: disruption of their signalling in uterine fibroid

CONTEXT

Investigation of activin-A (A) and myostatin (M) in human myometrium (HM) and leiomyoma (HL) will explain their involvement in human myometrial pathophysiology.

OBJECTIVE

We aimed to investigate A and M response and steroid regulation in HM. We also evaluated A and M expression and response in HL.

DESIGN

Tissues were analyzed and cultured.

PATIENTS

Patients included fertile (in proliferative phase) and menopausal women undergoing hysterectomy.

INTERVENTIONS

HM explant cultures were treated with A and M (for Smad-7 mRNA quantification) or estrogen and progesterone (for A and M mRNA quantification). A and M expression levels were also evaluated in menopausal (physiological absence of steroids) HM specimens. A and M and their receptors were evaluated in HL (n = 8, diameter 5-8 cm) compared with their matched HM. HL explants cultures were treated with A and M (for Smad7 mRNA quantification), and, to explain the absence of response, the levels of follistatin, follistatin-related gene (FLRG), and Cripto were evaluated.

RESULTS

A and M increased Smad7 expression in HM explants. A and M mRNAs were both reduced after estradiol treatment, unchanged after progesterone treatment, but were higher in menopausal than fertile (in proliferative phase) specimens. A, M, and FLRG were expressed at higher levels in HL compared with adjacent HM, whereas the receptors, follistatin, and Smad7 mRNAs resulted unchanged. Cripto mRNA was expressed only in HL.

CONCLUSIONS

A and M act on human HM and are regulated by steroids. In HL there is an increase of A, M, FLRG, and Cripto expression.

Placental expression of myostatin and follistatin-like-3 protein in a model of developmental programming

Maternal undernutrition during gestation is known to be detrimental to fetal development, leading to a propensity for metabolic disorders later in the adult lives of the offspring. Identifying possible mediators and physiological processes involved in modulating nutrient transport within the placenta is essential to prevent and/or develop treatments for the effects of aberrant nutrition, nutrient transfer, and detrimental changes to fetal development. A potential role for myostatin as a mediator of nutrient uptake and transport from the mother to the fetus was shown through the recent finding that myostatin acts within the human placenta to modulate glucose uptake and therefore homeostasis. The mRNA and protein expression of myostatin and its inhibitor, follistatin-like-3 (FSTL3), was studied in the placenta and skeletal muscle of a transgenerational Wistar rat model of gestational maternal undernutrition in which the F2 offspring postweaning consumed a high-fat (HF) diet. Alterations in placental characteristics and offspring phenotype, specifically glucose homeostasis, were evident in the transgenerationally undernourished (UNAD) group. Myostatin and FSTL3 protein expression were also higher (P < 0.05) in the placentae of the UNAD compared with the control group. At maturity, UNAD HF-fed animals had higher (P < 0.05) skeletal muscle expression of FSTL3 than control animals. In summary, maternal undernutrition during gestation results in the aberrant regulation of myostatin and FSTL3 in the placenta and skeletal muscle of subsequent generations. Myostatin, through the disruption of maternal nutrient supply to the fetus, may thus be a potential mediator of offspring phenotype.

Deranged expression of follistatin and follistatin-like protein in women with ovarian endometriosis

OBJECTIVE

To evaluate the messenger RNA (mRNA) expression and peptide localization of follistatin and follistatin-like protein (FLRG) in ovarian endometriosis, compared to healthy human endometrium.

DESIGN

Samples of ovarian endometriotic and healthy endometrial tissues were processed by semiquantitative reverse transcriptase-polymerase chain reaction and immunohistochemistry.

SETTING

Academic health centers in Siena, Italy, and Belo Horizonte, Brazil.

PATIENT(S)

Women with endometrioma who underwent laparoscopic excision of ovarian endometriotic cysts (n = 16), and healthy, nonpregnant women (n = 18, control group).

MAIN OUTCOME MEASURE(S)

Immunostaining and relative quantification of follistatin and FLRG mRNA in ovarian endometriosis and eutopic endometrium.

RESULT(S)

Both ovarian endometriosis and healthy endometrium expressed and localized follistatin and FLRG. In endometriotic glands, follistatin immunostaining was homogeneously distributed throughout the cytoplasm of the epithelial cells, contrasting with normal eutopic endometrium, where follistatin expression was focal, irregular, and confined to the basal side of the glands. Follistatin-like protein was immunolocalized in the nuclei of both glandular epithelial cells and stromal cells, with less intense staining in endometriotic samples. The relative intensity of follistatin and FLRG immunostaining was significantly higher and lower, respectively, in endometriosis than in controls. The expression of follistatin mRNA was higher, while that of FLRG mRNA was lower, in ovarian endometriosis than in healthy eutopic endometrium.

CONCLUSION(S)

Ovarian endometriotic lesions show a deranged expression of FLRG and follistatin, which are activin A-binding proteins. This may result in an altered effect of activin A on angiogenesis and/or endometrial differentiation.

Differential biosynthesis and intracellular transport of follistatin isoforms and follistatin-like-3

Follistatin (FST) and FST-like-3 (FSTL3) are structurally related proteins that bind and neutralize activin and closely related members of the TGFbeta superfamily. Three FST isoforms (FST288, FST303, and FST315) are produced from the Fst gene that are primarily secreted proteins. FSTL3 is secreted, but is also observed within the nucleus of most cells. We used pulse-chase (35)S labeling to examine the biosynthetic and intracellular transport patterns that lead to differential secretion and intracellular retention of these proteins. Among the FST isoforms, FST315 was secreted fastest and FST288 was secreted more slowly, with some remaining intracellular. In contrast, FSTL3 was secreted the slowest, with newly synthesized proteins being both secreted and trafficked to the nucleus. This nuclear FSTL3 was N-glycosylated, although not to the same degree as secreted FSTL3. Both FST and FSTL3 have two Mets in their signal sequence. Mutation of the first Met in FST288 eliminated protein translation, whereas FSTL3 could be translated from either Met. However, although FSTL3 translated from the second Met, which had no signal sequence, was confined to the nucleus, it was not glycosylated. Interestingly, this FSTL3 retained activin-antagonizing activity. Thus, although bioactive, nuclear FSTL3 can be translated from the second Met when the first Met is mutated, the glycosylated nuclear FSTL3 produced endogenously indicates that a different mechanism must be used under natural conditions that apparently includes N-glycosylation. Moreover, the differential biosynthetic and intracellular transport patterns for FST288 and FSTL3 suggest that these two activin-binding proteins may have distinct intracellular roles.

Purification, cDNA cloning, and secretory properties of FLRG protein from PC12 cells and the distribution of FLRG mRNA and protein in rat tissues

A 35 kD protein was isolated and purified from conditioned media of Bcl-2 cDNA-transfected PC12 cells and its cDNA cloned. A database analysis showed that the 35 kD protein is a rat homologue of the human FLRG protein. The biochemical as well as morphological properties of the rat FLRG protein in PC12 cells were examined and its distribution in rat tissues determined. The levels of FLRG mRNA expressed were low during the fetal period, compared with those of follistatin mRNA. The distribution of FLRG and follistatin mRNAs differed from each other after birth; the expression levels of FLRG mRNA were abundant in the adrenal gland and testis, whereas those of follistatin mRNA and activin A were markedly high in the ovary. The presence of FLRG mRNA and/or protein was confirmed in spermatocytes at various differentiating stages andin endocrine cells of both the adrenal cortex and medulla. When overexpressed in PC12 cells, the FLRG protein was found to be stored in secretory granules of the cells and largely secreted by a regulated pathway, while activin A enhancedthe constitutive secretion of the FLRG protein from wild-typpe PC12 cells, indicating that the FLRG protein possesses dualproperties in secretory pathways. The different distribution between FLRG and follistatin mRNA suggests that, like follistatin in the ovary, the FLRG protein may be involved in the maintenance of spermatogenesis in the testis and the growth and function of adrenal tissue cells, probably by regulating the functions of its binding partners such as the TGF-beta ( superfamily members.

Overexpression of follistatin-like 3 in gonads causes defects in gonadal development and function in transgenic mice

Activin has numerous biological activities including regulation of follicular development, spermatogenesis, and steroidogenesis within the gonads. Activities of activin are regulated by follistatin (FST), an activin binding protein, and perhaps follistatin-like 3 (FSTL3; also known as FLRG and FSRP). FSTL3 is a recently described member of the FST family having an overall structure and activity profile similar to that of FST, including binding and neutralization of activin. FSTL3 is most highly expressed in the placenta and testis, whereas FST is highest in the ovary and kidney, suggesting that FSTL3 has biological actions that do not entirely overlap those of FST. To investigate the role of local FSTL3 as a potential regulator of activin action in gonad development and function, we examined FSTL3 expression in the mouse testis. FSTL3 protein was localized to Leydig cells, spermatagonia, and mature spermatids in normal male mice. We then created transgenic mice using a human FSTL3 cDNA driven by the mouse alpha-inhibin promoter. Three of five transgenic founders were fertile and were bred to establish lines. In the highest expressing line 3, transgene expression was largely restricted to gonads, with pituitary, adrenal, brain, and uterine expression being substantially lower. Gonad weights, sperm counts, and fertility were significantly reduced in transgenic males, and reduced litter size was evident in line 3 females. Within the testis, highest transgene expression was observed in Sertoli cells, and although most tubules showed evidence of normal spermatogenic development, degenerating tubules devoid of germ cells and Leydig cell hyperplasia were also evident in every line 3 animal examined. Ovaries from line 3 females contained fewer antral follicles and more apparent follicular atresia. Although circulating human FSTL3 levels were undetectable, FSH and LH levels in adult transgenic mice were not significantly different from wild-type animals. However, testosterone levels were significantly increased at d 21 and significantly reduced at d 60 compared with wild-type males. These results suggest that FSTL3 is likely to be a local regulator of activin action in gonadal development and gametogenesis and, further, that activin appears to have important actions in gonadal development and function that are critical for normal reproduction.

Members of theWnt,Fz, andFrp gene families expressed in postnatal mouse cerebral cortex

The functions of Wingless-Int (Wnt) signaling, studied intensely in embryonic brain development, have been comparatively little investigated in the postnatal brain. We report remarkably patterned gene expression of Wnt signaling components in postnatal mouse cerebral cortex, lasting into young adulthood. Wnt genes are expressed in gene-specific regional and lamina patterns in each of the major subdivisions of the cerebral cortex: the olfactory bulb (OB), the hippocampal formation, and the neocortex. Genes encoding Frizzled (Fz) Wnt receptors, or secreted Frizzled-related proteins (sFrps), are also expressed in regional and lamina patterns. These findings suggest that Wnt signaling is active and regulated in the postnatal cortex and that different cortical cell populations have varying requirements for a Wnt signal. The OB, in particular, shows gene expression of a large variety of Wnt signaling components, making it a prime target for future functional studies. The penultimate components of the canonical Wnt pathway are the Tcf/Lef1 transcription factors, which regulate transcription of Wnt signaling target genes. Surprisingly, we found little Tcf/Lef1 expression in the postnatal neocortex. These observations suggest that noncanonical Wnt pathways predominate, which will require functional testing. However, Lef1 is widely expressed in the dorsal thalamus, and Wnt ligands and receptors are expressed, respectively, in cortical areas and thalamic nuclei that are interconnected. Thus, canonical Wnt signaling could be utilized in a major cortical input by Fz- and Lef1-expressing thalamic cells that innervate the Wnt-expressing cortex.

Follistatin-related gene (FLRG) expression in human endometrium: sex steroid hormones regulate the expression of FLRG in cultured human endometrial stromal cells

Follistatin-related gene (FLRG) encodes a novel secreted glycoprotein that is highly homologous to follistatin and binds activins and bone morphogenetic proteins, members of the TGF beta superfamily of growth/differentiation factors. FLRG protein inhibits activin-induced and bone morphogenetic protein-2-induced transcriptional responses in a dose-dependent manner, and its mRNA is abundantly expressed in human placenta, heart, aorta, testis, and adrenal gland. In this study we showed that FLRG mRNA was expressed in human endometrium across the menstrual cycle and in decidua of early pregnancy. In the proliferative phase of the menstrual cycle, FLRG protein was detected predominantly in the cytoplasm of endometrial epithelium. In the secretory phase and in early pregnancy, it was also detected in the nuclei of endometrial stromal cells. Using in vitro decidualization model, we demonstrated that 17 beta-estradiol plus progesterone, but not 17 beta-estradiol or progesterone alone, induced FLRG expression significantly. These results suggest that FLRG expression in endometrial stromal cells is regulated by the concerted action of ovarian steroid hormones via decidualization, and FLRG protein may participate in the regulation of stromal cell decidualization as a binding protein for members of TGF beta superfamily.

Occ1 mRNA expression reveals a characteristic feature in the hippocampal CA2 field of adult macaques

The gene occ1 is preferentially expressed in the primary visual cortex in an activity-dependent and developmentally regulated manner. In this report, we show the characteristic distribution of occ1 transcripts in the CA2 subfield of the hippocampal formation in adult monkeys. occ1 mRNA signals were observed selectively in the pyramidal cell layer of CA2. In addition to these signals, a relatively sparse distribution of occ1 was found in the stratum oriens and, occasionally, in the outermost regions of the pyramidal cell layers of both CA1 and CA2. A few labeled cells were detected in CA3. The elevated expression of occ1 in the CA2 subfield provides a new approach for investigating the function of this subregion, whose role has still not been well clarified.

Human placenta and fetal membranes express follistatin-related gene mRNA and protein

Activin A is a placental glycoprotein and possible biological actions during pregnancy, suggested by experimental data, are the modulation of cytotrophoblast differentiation, placental hormonogenesis and uterotonins secretion. Follistatin-related gene (FLRG) is a 70 amino acids protein which binds activin A with high affinity, and which modulates its biological effects on target tissues by preventing the activin A interaction with its receptors. The present study investigated whether trophoblast, decidua and fetal membranes express FLRG mRNA (by RT-PCR) and peptide (by immunohistochemistry). Tissue specimens were collected at first and third trimester of pregnancy, from patients undergoing voluntary pregnancy interruption (no.=6; from 8 to 12 gestational weeks) and elective caesarean section at term (no.=6; 39-40 weeks of pregnancy). FLRG mRNA was expressed by the various gestational tissues both at early gestation and at term pregnancy. Immunoreactive protein was found in the trophoblast cells, epithelial amniotic and chorionic cells and maternal decidua; nevertheless, the most intense FLRG stain was detected in the walls of decidual and placental blood vessels. In conclusion, FLRG mRNA and peptide are expressed by placenta and fetal membranes. Its different immunolocalization with respect to follistatin and activin A supports a different role for FLRG in modulating activin A actions into gestational tissues.

Regulation of FLRG expression in rat primary astroglial cells and injured brain tissue by transforming growth factor-beta 1 (TGF-beta 1)

Follistatin-related gene (FLRG) is a member of the follistatin family of proteins and interacts with transforming growth factor (TGF) superfamily proteins like follistatin. To understand the expression level of FLRG in brain tissue, we examined whether primary neurons and glial cells from rat embryos express FLRG mRNA and produce its protein product. FLRG and follistain mRNAs were mainly expressed in astroglial cells, while activin A mRNA was abundant in primary neurons. TGF-beta1 highly enhanced expression levels of FLRG mRNA in astroglial cells, compared with those of follistatin and activin A mRNAs. Particularly, TGF-beta1 facilitated the secretion of FLRG protein from primary astroglial cells in a dose-dependent manner. Moreover, changes in expression levels of FLRG mRNA and protein in brain tissue were also analyzed after a penetrating injury, using quantitative polymerase chain reactin (PCR) and immunohistochemical methods. Expression levels of FLRG mRNA were significantly increased in damaged regions after penetrating injury together with those of activin A and TGF-beta1 mRNAs. Immunohistochemical observations showed that positive signals of FLRG protein were colocalized in glial fibrillary acidic protein-positive reactive astroglial cells located in damaged regions after a penetrating injury. The expression of follistatin mRNA rather decreased in damage regions after the brain injury. These results suggest that FLRG is synthesized in and secreted from astroglial cells. In particular, FLRG, but not follistatin, may play a role in the regulation of activin A in brain wound healing in response to TGF-beta1.

Expression of Wnt and Notch pathway genes in a pluripotent human embryonal carcinoma cell line and embryonic stem cell

Embryonal carcinoma (EC) cells, the pluripotent stem cells of teratocarcinomas, show many similar-ities to embryonic stem (ES) cells. Since EC cells are malignant but their terminally differentiated derivatives are not, understanding the molecular mechanisms that regulate their differentiation maybe of value for diagnostic and therapeutic purposes. We have examined the expression of multiple components of two developmentally important cell-cell signalling pathways, Wnt and Notch, in the pluripotent human EC cell line, NTERA2, and the human ES cell line, H7. Both pathways have well-documented roles in controlling neurogenesis, a process that occurs largely in response to retinoicacid (RA) treatment of NTERA2 cultures and spontaneously in H7 cultures. In NTERA2, many ofthe genes tested showed altered transcriptional regulation following treatment with RA. These include members of the frizzled gene family (FZDI, FZD3, FZD4, FZD5, FZD6), encoding receptors forWnt proteins, the Frizzled Related Protein family (SFRPI, SFRP2, FRZB, SFRP4), encoding solubleWnt antagonists and also ligands and receptors of the Notch pathway (Dlkl, Jaggedl; Notchl, Notch2, Notch3). Few differences were found in the repertoire of Wnt and Notch pathway genes expressed by NTERA2 EC cells and H7 ES cells. We present a model in which interactions between and regulation of Wnt and Notch signalling are important in maintaining EC/ES stem cells and also controlling their differentiation.