Neudesin regulates dendritic cell function and antitumor CD8+ T cell immunity.

Dendritic cells (DCs) are essential for antitumor T-cell responses to immune checkpoint inhibitor therapies. We have previously reported that the secreted protein neudesin suppresses DC function. In contrast, neudesin has been found to be abundantly expressed in human cancers. In this study, we evaluated the role of neudesin in cancer immunity. Cancer-related database analysis revealed that patients with melanoma with low neudesin expression exhibited increased infiltration of DCs and CD8+ T cells and improved outcomes of checkpoint inhibitor therapy. In mouse tumor models, neudesin deficiency delayed tumor growth and increased the proportions of Type 1 conventional DCs (cDC1s) and tumor antigen-specific CD8+ T cells in tumors and tumor-infiltrating lymph nodes. Neudesin-deficient antitumor cDC1 vaccine enhanced the systemic immunity more effectively than the wild-type cDC1 vaccine. Overall, our findings highlight the importance of neudesin in cancer immunity, providing a novel target for immunotherapy.

BACH1 inhibits senescence, obesity, and short lifespan by ferroptotic FGF21 secretion.

Ferroptosis is a type of regulated cell death characterized by iron-dependent lipid peroxidation. A model cell system is constructed to induce ferroptosis by re-expressing the transcription factor BACH1, a potent ferroptosis inducer, in immortalized mouse embryonic fibroblasts (iMEFs). The transfer of the culture supernatant from ferroptotic iMEFs activates the proliferation of hepatoma cells and other fibroblasts and suppresses cellular senescence-like features. The BACH1-dependent secretion of the longevity factor FGF21 is increased in ferroptotic iMEFs. The anti-senescent effects of the culture supernatant from these iMEFs are abrogated by Fgf21 knockout. BACH1 activates the transcription of Fgf21 by promoting ferroptotic stress and increases FGF21 protein expression by suppressing its autophagic degradation through transcriptional Sqstm1 and Lamp2 repression. The BACH1-induced ferroptotic FGF21 secretion suppresses obesity in high-fat diet-fed mice and the short lifespan of progeria mice. The inhibition of these aging-related phenotypes can be physiologically significant regarding ferroptosis.

A novel type IIb L-asparaginase from Latilactobacillus sakei LK-145: characterization and application.

We succeeded in homogeneously expressing and purifying L-asparaginase from Latilactobacillus sakei LK-145 (Ls-Asn1) and its mutated enzymes C196S, C264S, C290S, C196S/C264S, C196S/C290S, C264S/C290S, and C196S/C264S/C290S-Ls-Asn1. Enzymological studies using purified enzymes revealed that all cysteine residues of Ls-Asn1 were found to affect the catalytic activity of Ls-Asn1 to varying degrees. The mutation of Cys196 did not affect the specific activity, but the mutation of Cys264, even a single mutation, significantly decreased the specific activity. Furthermore, C264S/C290S- and C196S/C264S/C290S-Ls-Asn1 almost completely lost their activity, suggesting that C290 cooperates with C264 to influence the catalytic activity of Ls-Asn1. The detailed enzymatic properties of three single-mutated enzymes (C196S, C264S, and C290S-Ls-Asn1) were investigated for comparison with Ls-Asn1. We found that only C196S-Ls-Asn1 has almost the same enzymatic properties as that of Ls-Asn1 except for its increased stability for thermal, pH, and the metals NaCl, KCl, CaCl2, and FeCl2. We measured the growth inhibitory effect of Ls-Asn1 and C196S-Ls-Asn1 on Jurkat cells, a human T-cell acute lymphoblastic leukemia cell line, using L-asparaginase from Escherichia coli K-12 as a reference. Only C196S-Ls-Asn1 effectively and selectively inhibited the growth of Jurkat T-cell leukemia, which suggested that it exhibited antileukemic activity. Furthermore, based on alignment, phylogenetic tree analysis, and structural modeling, we also proposed that Ls-Asn1 is a so-called "Type IIb" novel type of asparaginase that is distinct from previously reported type I or type II asparaginases. Based on the above results, Ls-Asn1 is expected to be useful as a new leukemia therapeutic agent.

Maitake Beta-Glucan Enhances the Therapeutic Effect of Trastuzumab via Antibody-Dependent Cellular Cytotoxicity and Complement-Dependent Cytotoxicity.

Trastuzumab, an anti-HER2 monoclonal antibody, is the mainstay treatment for of HER2-positive breast cancer. However, trastuzumab resistance is often observed during treatment. Therefore, new therapeutic strategies are needed to enhance the clinical benefits of trastuzumab. Maitake ß-glucan MD-Fraction, isolated from Grifola frondosa, inhibits tumor growth by enhancing immune responses. In this study, we examined the effect of MD-Fraction on trastuzumab treatment of HER2-positive breast cancer. MD-Fraction did not directly inhibit the survival of HER2-positive breast cancer cells, alone or in the presence of trastuzumab in vitro. In HER2-positive xenograft models, the combination of MD-Fraction and trastuzumab was more effective than trastuzumab alone. Peripheral blood lymphocytes and splenic natural killer cells isolated from BALB/c nu/nu mice treated with MD-Fraction showed enhanced trastuzumab-induced antibody-dependent cellular cytotoxicity (ADCC) ex vivo. MD-Fraction-treated macrophages and neutrophils did not show enhanced trastuzumab cytotoxicity in the presence of heat-inactivated serum, but they showed enhanced cytotoxicity in the presence of native serum. These results suggest that MD-Fraction-treated macrophages and neutrophils enhance trastuzumab-induced complement-dependent cellular cytotoxicity (CDCC). Treatment of HER2-positive breast cancer cells with MD-Fraction in the presence of trastuzumab and native serum increased C3a release and tumor cell lysis in a dose-dependent manner, indicating that MD-Fraction enhanced trastuzumab-induced complement-dependent cytotoxicity (CDC) by activating the complement system. This study demonstrates that the combination of trastuzumab and MD-Fraction exerts a greater antitumor effect than trastuzumab alone by enhancing ADCC, CDCC, and CDC in HER2-positive breast cancer.

A secretory protein neudesin regulates splenic red pulp macrophages in erythrophagocytosis and iron recycling.

Neudesin, originally identified as a neurotrophic factor, has primarily been studied for its neural functions despite its widespread expression. Using 8-week-old neudesin knockout mice, we elucidated the role of neudesin in the spleen. The absence of neudesin caused mild splenomegaly, shortened lifespan of circulating erythrocytes, and abnormal recovery from phenylhydrazine-induced acute anemia. Blood cross-transfusion and splenectomy experiments revealed that the shortened lifespan of erythrocytes was attributable to splenic impairment. Further analysis revealed increased erythrophagocytosis and decreased iron stores in the splenic red pulp, which was linked to the upregulation of Fcγ receptors and iron-recycling genes in neudesin-deficient macrophages. In vitro analysis confirmed that neudesin suppressed erythrophagocytosis and expression of Fcγ receptors through ERK1/2 activation in heme-stimulated macrophages. Finally, we observed that 24-week-old neudesin knockout mice exhibited severe symptoms of anemia. Collectively, our results suggest that neudesin regulates the function of red pulp macrophages and contributes to erythrocyte and iron homeostasis.

Maitake α-glucan promotes differentiation of monocytic myeloid-derived suppressor cells into M1 macrophages.

AIMS: Myeloid-derived suppressor cells (MDSCs) are major components of the tumor microenvironment and systemically accumulate in tumor-bearing hosts and patients with cancer, facilitating cancer progression. Maitake macromolecular α-glucan YM-2A, isolated from Grifola frondosa, inhibits tumor growth by enhancing immune responses. The present study investigated the effects of YM-2A on the immunosuppressive potential of MDSCs. MAIN METHODS: YM-2A was orally administered to CT26 tumor-bearing mice, and the number of immune cells in the spleen and tumor was measured. Splenic MDSCs isolated from the CT26 tumor-bearing mice were treated with YM-2A and co-cultured with T cells to measure their inhibitory effect on T cell proliferation. For adoptive transfer of monocytic MDSCs (M-MDSCs), YM-2A-treated M-MDSCs mixed with CT26 cells were implanted subcutaneously in the mice to measure the tumor growth rate. KEY FINDINGS: YM-2A selectively reduced the accumulation of M-MDSCs but not that of polymorphonuclear MDSCs (PMN-MDSCs) in CT26 tumor-bearing mice. In tumor tissues, YM-2A treatment induced the polarity of immunostimulatory M1-phenotype; furthermore, it increased the infiltration of dendritic, natural killer, and CD4+ and CD8+ T cells. YM-2A treatment of purified M-MDSCs from CT-26 tumor-bearing mice induced dectin-1-dependent differentiation into M1 macrophages. YM-2A-treated M-MDSCs lost their inhibitory activity against proliferation and activation of CD8+ T cells. Furthermore, adoptive transfer of M-MDSCs treated with YM-2A inhibited CT26 tumor growth. SIGNIFICANCE: YM-2A promotes the differentiation of M-MDSCs into immunostimulatory M1 macrophages, thereby enhancing the efficacy of cancer immunotherapy.

Testicular Hypoplasia with Normal Fertility in Neudesin-Knockout Mice.

Neudesin is a secretory protein involved in the brain development during embryonic period and diet-induced development of adipose tissue. Although neudesin is also expressed in the testis, its physiological functions in the testis have not been documented. Therefore, we examined neudesin-encoding neuron-derived neurotrophic factor (Nenf) gene-knockout (Neudesin-KO) mice to clarify the functions of neudesin in the testis. The testicular size of the Neudesin-KO mice was significantly smaller than that of wild-type (WT) mice. However, histological analyses did not reveal any abnormalities in the testis, caput epididymis, and cauda epididymis. Sperm number in the cauda epididymis was comparable between WT and KO mice. Neudesin-KO male mice produced vaginal plugs on paired WT female mice, with a frequency similar to that in WT male mice. A similar number of embryos were developed in the females copulated with WT and Neudesin-KO males. Molecular analysis indicated that the ion transporters Slc19a1 and Kcnk3 were more expressed in the testis of Neudesin-KO mice than in the testis of WT mice, suggesting that the transport of ions and some nutrients in the testis has some abnormalities. Testicular size decreased on postnatal day 6, but not on the day of birth, indicating that neudesin is involved in the postnatal, but not embryonic, development of testis. These results indicate a novel role of neudesin in the development of testis.

Social stress alters sleep in FGF21-deficient mice.

Although several previous studies have suggested a relationship between sleep and the stress response, the mechanism underlying this relationship remains largely unknown. Here, we show that fibroblast growth factor 21 (FGF21), a lipid metabolism-related hormone, may play a role in this relationship. In this study, we examined differences in the stress response between FGF21 knockout (KO) mice and wild-type (WT) mice after social defeat stress (SDS). When the amount of non-rapid eye movement (NREM) sleep, rapid eye movement (REM) sleep and wakefulness were averaged over the dark period after SDS, only KO mice showed significant differences in NREM sleep and wakefulness. In the social interaction test, KO mice seemed to be more prone to social avoidance. Our real-time (RT) -PCR results revealed that the mRNA expression of the stress- and sleep-related gene gamma-aminobutyric acid A receptor subunit alpha 2 was significantly lower in WT mice than in KO mice. Moreover, KO mice showed lower plasma levels of ketone bodies, which also affect sleep/wake regulation, than WT mice. These results suggested that FGF21 might influence sleep/wake regulation by inducing production of an anti-stress agent and/or ketone bodies, which may result in resilience to social stress.

Activation of macrophages mediates dietary restriction-induced splenic involution.

BACKGROUND: Malnutrition affects various physiological functions, including immune defenses. However, it remains unclear how malnutrition reduces immune responses. AIM: To elucidate mechanisms underlying malnutrition-induced immunodeficiency, we focused on the spleen, which plays an essential role in the immune system, and examined the impacts of malnutrition on the spleen. MAIN METHODS: The impact of malnutrition on the spleen was assessed using dietary-restricted mice as a model. Weights of the spleen were measured and normalized to body weights. Macrophage maker protein expression was observed using fluorescent immunostaining. Clodronate-containing liposomes were injected into the mice to test whether macrophages are involved in splenic changes induced by dietary restriction. KEY FINDINGS: The spleen of dietary-restricted mice involuted with significant reductions in the relative weight of the spleen to the body weight and ratio of the red pulp in the spleen. Then, we examined whether macrophages mediate dietary restriction-induced splenic involution. The IBA1/AIF1 protein level was increased in the marginal zone, which is the interface between the red and white pulps of the spleen, by dietary restriction. We tested whether macrophages are needed for dietary restriction-induced splenic involution. The increase in IBA1/AIF1 expression in the marginal zone and splenic involution were suppressed by clodronate liposome administration. These results indicate that the macrophages in the splenic marginal zone were activated by dietary restriction and were required for dietary restriction-induced splenic involution. SIGNIFICANCE: Our study proposes macrophage-mediated splenic involution as a novel mechanism linking malnutrition to immunodeficiency.

Starvation-induced transcription factor CREBH negatively governs body growth by controlling GH signaling.

cAMP responsive element-binding protein H (CREBH) is a hepatic transcription factor to be activated during fasting. We generated CREBH knock-in flox mice, and then generated liver-specific CREBH transgenic (CREBH L-Tg) mice in an active form. CREBH L-Tg mice showed a delay in growth in the postnatal stage. Plasma growth hormone (GH) levels were significantly increased in CREBH L-Tg mice, but plasma insulin-like growth factor 1 (IGF1) levels were significantly decreased, indicating GH resistance. In addition, CREBH overexpression significantly increased hepatic mRNA and plasma levels of FGF21, which is thought to be as one of the causes of growth delay. However, the additional ablation of FGF21 in CREBH L-Tg mice could not correct GH resistance at all. CREBH L-Tg mice sustained GH receptor (GHR) reduction and the increase of IGF binding protein 1 (IGFBP1) in the liver regardless of FGF21. As GHR is a first step in GH signaling, the reduction of GHR leads to impairment of GH signaling. These data suggest that CREBH negatively regulates growth in the postnatal growth stage via various pathways as an abundant energy response by antagonizing GH signaling.

The role of increased FGF21 in VLDL-TAG secretion and thermogenic gene expression in mice under protein malnutrition.

Protein malnutrition promotes hepatic lipid accumulation in growing animals. In these animals, fibroblast growth factor 21 (FGF21) rapidly increases in the liver and circulation and plays a protective role in hepatic lipid accumulation. To investigate the mechanism by which FGF21 protects against liver lipid accumulation under protein malnutrition, we determined whether upregulated FGF21 promotes the thermogenesis or secretion of very-low-density lipoprotein (VLDL)-triacylglycerol (TAG). The results showed that protein malnutrition decreased VLDL-TAG secretion, but the upregulation of FGF21 did not oppose this effect. In addition, protein malnutrition increased expression of the thermogenic gene uncoupling protein 1 in inguinal white adipose and brown adipose tissue in an FGF21-dependent manner. However, surgically removing inguinal white adipose tissue did not affect liver triglyceride levels in protein-malnourished mice. These data suggest that FGF21 stimulates thermogenesis under protein malnutrition, but this is not the causative factor underlying the protective role of FGF21 against liver lipid accumulation.

Enterohepatic Transcription Factor CREB3L3 Protects Atherosclerosis via SREBP Competitive Inhibition.

BACKGROUND & AIMS: cAMP responsive element-binding protein 3 like 3 (CREB3L3) is a membrane-bound transcription factor involved in the maintenance of lipid metabolism in the liver and small intestine. CREB3L3 controls hepatic triglyceride and glucose metabolism by activating plasma fibroblast growth factor 21 (FGF21) and lipoprotein lipase. In this study, we intended to clarify its effect on atherosclerosis. METHODS: CREB3L3-deficifient, liver-specific CREB3L3 knockout, intestine-specific CREB3L3 knockout, both liver- and intestine-specific CREB3L3 knockout, and liver CREB3L3 transgenic mice were crossed with LDLR-/- mice. These mice were fed with a Western diet to develop atherosclerosis. RESULTS: CREB3L3 ablation in LDLR-/- mice exacerbated hyperlipidemia with accumulation of remnant APOB-containing lipoprotein. This led to the development of enhanced aortic atheroma formation, the extent of which was additive between liver- and intestine-specific deletion. Conversely, hepatic nuclear CREB3L3 overexpression markedly suppressed atherosclerosis with amelioration of hyperlipidemia. CREB3L3 directly up-regulates anti-atherogenic FGF21 and APOA4. In contrast, it antagonizes hepatic sterol regulatory element-binding protein (SREBP)-mediated lipogenic and cholesterogenic genes and regulates intestinal liver X receptor-regulated genes involved in the transport of cholesterol. CREB3L3 deficiency results in the accumulation of nuclear SREBP proteins. Because both transcriptional factors share the cleavage system for nuclear transactivation, full-length CREB3L3 and SREBPs in the endoplasmic reticulum (ER) functionally inhibit each other. CREB3L3 promotes the formation of the SREBP-insulin induced gene 1 complex to suppress SREBPs for ER-Golgi transport, resulting in ER retention and inhibition of proteolytic activation at the Golgi and vice versa. CONCLUSIONS: CREB3L3 has multi-potent protective effects against atherosclerosis owing to new mechanistic interaction between CREB3L3 and SREBPs under atherogenic conditions.

Induced Prostanoid Synthesis Regulates the Balance between Th1- and Th2-Producing Inflammatory Cytokines in the Thymus of Diet-Restricted Mice.

Multiple external and internal factors have been reported to induce thymic involution. Involution involves dramatic reduction in size and function of the thymus, leading to various immunodeficiency-related disorders. Therefore, clarifying and manipulating molecular mechanisms governing thymic involution are clinically important, although only a few studies have dealt with this issue. In the present study, we investigated the molecular mechanisms underlying thymic involution using a murine acute diet-restriction model. Gene expression analyses indicated that the expression of T helper 1 (Th1)-producing cytokines, namely interferon-γ and interleukin (IL)-2, was down-regulated, while that of Th2-producing IL-5, IL-6, IL-10 and IL-13 was up-regulated, suggesting that acute diet-restriction regulates the polarization of naïve T cells to a Th2-like phenotype during thymic involution. mRNAs for prostanoid biosynthetic enzymes were up-regulated by acute diet-restriction. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) analyses detected the increased production of prostanoids, particularly prostaglandin D2 and thromboxane B2, a metabolite of thromboxane A2, in the diet-restricted thymus. Administration of non-steroidal anti-inflammatory drugs, namely aspirin and etodolac, to inhibit prostanoid synthesis suppressed the biased expression of Th1- and Th2-cytokines as well as molecular markers of Th1 and Th2 cells in the diet-restricted thymus, without affecting the reduction of thymus size. In vitro stimulation of thymocytes with phorbol myristate acetate (PMA)/ionomycin confirmed the polarization of thymocytes from diet-restricted mice toward Th2 cells. These results indicated that the induced production of prostanoids during diet-restriction-induced thymic involution is involved in the polarization of naïve T cells in the thymus.

CREBH Improves Diet-Induced Obesity, Insulin Resistance, and Metabolic Disturbances by FGF21-Dependent and FGF21-Independent Mechanisms.

Mice overexpressing the nuclear form of CREBH mainly in the liver (CREBH-Tg) showed suppression of high-fat high-sucrose (HFHS) diet-induced obesity accompanied by an increase in plasma fibroblast growth factor 21 (FGF21) levels. CREBH overexpression induced browning in inguinal white adipose tissue (WAT) and whole-body energy expenditure, which was canceled in Fgf21-/- mice. Deficiency of FGF21 in CREBH-Tg mice mostly canceled the improvement of obesity, but the suppression of inflammation of epidermal WAT, amelioration of insulin resistance, and improvement of glucose metabolism still sustained. Kisspeptin 1 (Kiss1) was identified as a novel hormone target for CREBH to explain these FGF21-independent effects of CREBH. Knockdown of Kiss1 in HFHS-fed CREBH-Tg Fgf21-/- mice showed partially canceled improvement of glucose metabolism. Taken together, we propose that hepatic CREBH pleiotropically improves diet-induced obesity-mediated dysfunctions in peripheral tissues by improving systemic energy metabolism in FGF21-dependent and FGF21-independent mechanisms.

Maturation of dendritic cells by maitake α-glucan enhances anti-cancer effect of dendritic cell vaccination.

Dendritic cells (DCs) play a primary role in antigen presentation to CD4+ and CD8+ T cells and induce acquired immune response against cancer cells. Therefore, determining positive modulators of DC activation to improve therapeutic approaches for cancer immunotherapy is greatly needed. In this study, we investigated the effect of maitake α-glucan YM-2A, isolated from Grifola frondosa, on the maturation and function of DCs and its adjuvant effect on a tumor-associated antigen (TAA)-loaded DC vaccine against murine tumor. We showed that YM-2A induced morphological changes and increased cell-surface maturation markers and cytokine production in DCs. In a mixed lymphocyte reactions assay, YM-2A-treated DCs increased proliferation and production of IFN-γ by allogeneic CD4+ and CD8+ T cells. These results indicate that YM-2A phenotypically and functionally activates DCs. Furthermore, YM-2A-treated TAA-loaded DC vaccine significantly reduced tumor growth and improved survival in two murine tumor models, CT-26 tumor-bearing BALB/c mice and B16 melanoma-bearing C57BL/6 mice. YM-2A-treated TAA-loaded DC vaccine increased splenic IFN-γ producing CD4+ and CD8+ T cells in CT-26 tumor-bearing BALB/c mice. Antibody neutralization studies indicated that YM-2A-induced DC maturation is mediated, in part, by the Dectin-1-dependent pathway. Overall, YM-2A-treatment with a TAA-loaded DC vaccine could be an excellent candidate for immunotherapy against cancer.

Epigenetic modulation of Fgf21 in the perinatal mouse liver ameliorates diet-induced obesity in adulthood.

The nutritional environment to which animals are exposed in early life can lead to epigenetic changes in the genome that influence the risk of obesity in later life. Here, we demonstrate that the fibroblast growth factor-21 gene (Fgf21) is subject to peroxisome proliferator-activated receptor (PPAR) α-dependent DNA demethylation in the liver during the postnatal period. Reductions in Fgf21 methylation can be enhanced via pharmacologic activation of PPARα during the suckling period. We also reveal that the DNA methylation status of Fgf21, once established in early life, is relatively stable and persists into adulthood. Reduced DNA methylation is associated with enhanced induction of hepatic FGF21 expression after PPARα activation, which may partly explain the attenuation of diet-induced obesity in adulthood. We propose that Fgf21 methylation represents a form of epigenetic memory that persists into adulthood, and it may have a role in the developmental programming of obesity.

Peripherally derived FGF21 promotes remyelination in the central nervous system.

Demyelination in the central nervous system (CNS) leads to severe neurological deficits that can be partially reversed by spontaneous remyelination. Because the CNS is isolated from the peripheral milieu by the blood-brain barrier, remyelination is thought to be controlled by the CNS microenvironment. However, in this work we found that factors derived from peripheral tissue leak into the CNS after injury and promote remyelination in a murine model of toxin-induced demyelination. Mechanistically, leakage of circulating fibroblast growth factor 21 (FGF21), which is predominantly expressed by the pancreas, drives proliferation of oligodendrocyte precursor cells (OPCs) through interactions with ß-klotho, an essential coreceptor of FGF21. We further confirmed that human OPCs expressed ß-klotho and proliferated in response to FGF21 in vitro. Vascular barrier disruption is a common feature of many CNS disorders; thus, our findings reveal a potentially important role for the peripheral milieu in promoting CNS regeneration.

Membrane progesterone receptor beta (mPRß/Paqr8) promotes progesterone-dependent neurite outgrowth in PC12 neuronal cells via non-G protein-coupled receptor (GPCR) signaling.

Recently, sex steroid membrane receptors garnered world-wide attention because they may be related to sex hormone-mediated unknown rapid non-genomic action that cannot be currently explained by their genomic action via nuclear receptors. Progesterone affects cell proliferation and survival via non-genomic effects. In this process, membrane progesterone receptors (mPRα, mPRß, mPRγ, mPRδ, and mPRε) were identified as putative G protein-coupled receptors (GPCRs) for progesterone. However, the structure, intracellular signaling, and physiological functions of these progesterone receptors are still unclear. Here, we identify a molecular mechanism by which progesterone promotes neurite outgrowth through mPRß (Paqr8) activation. Mouse mPRß mRNA was specifically expressed in the central nervous system. It has an incomplete GPCR topology, presenting 6 transmembrane domains and did not exhibit typical GPCR signaling. Progesterone-dependent neurite outgrowth was exhibited by the promotion of ERK phosphorylation via mPRß, but not via other progesterone receptors such as progesterone membrane receptor 1 (PGRMC-1) and nuclear progesterone receptor in nerve growth factor-induced neuronal PC12 cells. These findings provide new insights of regarding the non-genomic action of progesterone in the central nervous system.

Brorin is required for neurogenesis, gliogenesis, and commissural axon guidance in the zebrafish forebrain.

Bmps regulate numerous neural functions with their regulators. We previously identified Brorin, a neural-specific secreted antagonist of Bmp signaling, in humans, mice, and zebrafish. Mouse Brorin has two cysteine-rich domains containing 10 cysteine residues in its core region, and these are located in similar positions to those in the cysteine-rich domains of Chordin family members, which are secreted Bmp antagonists. Zebrafish Brorin had two cysteine-rich domains with high similarity to those of mouse Brorin. We herein examined zebrafish brorin in order to elucidate its in vivo actions. Zebrafish brorin was predominantly expressed in developing neural tissues. The overexpression of brorin led to the inactivation of Bmp signaling. On the other hand, the knockdown of brorin resulted in the activation of Bmp signaling and brorin morphants exhibited defective development of the ventral domain in the forebrain. Furthermore, the knockdown of brorin inhibited the generation of γ-aminobutyric acid (GABA)ergic interneurons and oligodendrocytes and promoted the generation of astrocytes in the forebrain. In addition, brorin was required for axon guidance in the forebrain. The present results suggest that Brorin is a secreted Bmp antagonist predominantly expressed in developing neural tissues and that it plays multiple roles in the development of the zebrafish forebrain.

Fgf21 regulates T-cell development in the neonatal and juvenile thymus.

We have previously shown that Fibroblast growth factor 21 (Fgf21) is expressed in the thymus as well as in the liver. In line with this expression profile, Fgf21 was recently reported to protect against ageing-related thymic senescence by improving the function of thymic epithelial cells (TECs). However, the function of Fgf21 in the juvenile thymus remained to be elucidated. We investigated the physiological roles of Fgf21 in the juvenile thymus and found that young Fgf21 knockout mice, but not ß-Klotho knockout mice nor adult Fgf21 knockout mice, showed a significant reduction in the percentage of single-positive CD4+ and CD8+ thymocytes without obvious alteration in TECs. Furthermore, treatment with recombinant FGF21 protein rescued the impairment in fetal thymus organ culture (FTOC) of Fgf21 knockout mice. Annexin V staining revealed FGF21 protein enhanced apoptosis of immature thymocytes undergoing selection process in FTOC, suggesting that FGF21 may facilitate the selection of developing T cells. Endocrine Fgf21 from the liver induced by metabolic stimulation did not affect juvenile thymocyte development. Our data suggest that Fgf21 acts as one of intrathymic cytokines in the neonatal and juvenile thymus, involving thymocyte development in a ß-Klotho-independent manner.