Thyroid Hormone Receptor Is Essential for Larval Epithelial Apoptosis and Adult Epithelial Stem Cell Development but Not Adult Intestinal Morphogenesis during Xenopus tropicalis Metamorphosis.

Vertebrate postembryonic development is regulated by thyroid hormone (T3). Of particular interest is anuran metamorphosis, which offers several unique advantages for studying the role of T3 and its two nuclear receptor genes, TRα and TRß, during postembryonic development. We have recently generated TR double knockout (TRDKO) Xenopus tropicalis animals and reported that TR is essential for the completion of metamorphosis. Furthermore, TRDKO tadpoles are stalled at the climax of metamorphosis before eventual death. Here we show that TRDKO intestine lacked larval epithelial cell death and adult stem cell formation/proliferation during natural metamorphosis. Interestingly, TRDKO tadpole intestine had premature formation of adult-like epithelial folds and muscle development. In addition, T3 treatment of premetamorphic TRDKO tadpoles failed to induce any metamorphic changes in the intestine. Furthermore, RNA-seq analysis revealed that TRDKO altered the expression of many genes in biological pathways such as Wnt signaling and the cell cycle that likely underlay the inhibition of larval epithelial cell death and adult stem cell development caused by removing both TR genes. Our data suggest that liganded TR is required for larval epithelial cell degeneration and adult stem cell formation, whereas unliganded TR prevents precocious adult tissue morphogenesis such as smooth-muscle development and epithelial folding.

Hematopoiesis in aged female mice devoid of thyroid hormone receptors.

Hypothyroidism is often associated with anemia and immunological disorders. Similar defects are found in patients and in mice with a mutated dominant-negative thyroid hormone receptor α (TRα) and in knockout mice devoid of this receptor, suggesting that this isoform is responsible for the effects of the thyroid hormones in hematopoiesis. However, the hematological phenotype of mice lacking also TRß has not yet been examined. We show here that TRα1/TRß-knockout female mice, lacking all known thyroid hormone receptors with capacity to bind thyroid hormones, do not have overt anemia and in contrast with hypothyroid mice do not present reduced Gata1 or Hif1 gene expression. Similar to that found in hypothyroidism or TRα deficiency during the juvenile period, the B-cell population is reduced in the spleen and bone marrow of ageing TRα1/TRß-knockout mice, suggesting that TRß does not play a major role in B-cell development. However, splenic hypotrophy is more marked in hypothyroid mice than in TRα1/TRß-knockout mice and the splenic population of T-lymphocytes is not significantly impaired in these mice in contrast with the reduction found in hypothyroidism. Our results show that the overall hematopoietic phenotype of the TRα1/TRß-knockout mice is milder than that found in the absence of hormone. Although other mechanism/s cannot be ruled out, our results suggest that the unoccupied TRs could have a negative effect on hematopoiesis, likely secondary to repression of hematopoietic gene expression.

The orphan nuclear receptor NR4A3 controls the differentiation of monocyte-derived dendritic cells following microbial stimulation.

In response to microbial stimulation, monocytes can differentiate into macrophages or monocyte-derived dendritic cells (MoDCs) but the molecular requirements guiding these possible fates are poorly understood. In addition, the physiological importance of MoDCs in the host cellular and immune responses to microbes remains elusive. Here, we demonstrate that the nuclear orphan receptor NR4A3 is required for the proper differentiation of MoDCs but not for other types of DCs. Indeed, the generation of DC-SIGN+ MoDCs in response to LPS was severely impaired in Nr4a3-/- mice, which resulted in the inability to mount optimal CD8+ T cell responses to gram-negative bacteria. Transcriptomic analyses revealed that NR4A3 is required to skew monocyte differentiation toward MoDCs, at the expense of macrophages, and allows the acquisition of migratory characteristics required for MoDC function. Altogether, our data identify that the NR4A3 transcription factor is required to guide the fate of monocytes toward MoDCs.

NR4A transcription factors limit CAR T cell function in solid tumours.

T cells expressing chimeric antigen receptors (CAR T cells) targeting human CD19 (hCD19) have shown clinical efficacy against B cell malignancies1,2. CAR T cells have been less effective against solid tumours3-5, in part because they enter a hyporesponsive ('exhausted' or 'dysfunctional') state6-9 triggered by chronic antigen stimulation and characterized by upregulation of inhibitory receptors and loss of effector function. To investigate the function of CAR T cells in solid tumours, we transferred hCD19-reactive CAR T cells into hCD19+ tumour-bearing mice. CD8+CAR+ tumour-infiltrating lymphocytes and CD8+ endogenous tumour-infiltrating lymphocytes expressing the inhibitory receptors PD-1 and TIM3 exhibited similar profiles of gene expression and chromatin accessibility, associated with secondary activation of nuclear receptor transcription factors NR4A1 (also known as NUR77), NR4A2 (NURR1) and NR4A3 (NOR1) by the initiating transcription factor NFAT (nuclear factor of activated T cells)10-12. CD8+ T cells from humans with cancer or chronic viral infections13-15 expressed high levels of NR4A transcription factors and displayed enrichment of NR4A-binding motifs in accessible chromatin regions. CAR T cells lacking all three NR4A transcription factors (Nr4a triple knockout) promoted tumour regression and prolonged the survival of tumour-bearing mice. Nr4a triple knockout CAR tumour-infiltrating lymphocytes displayed phenotypes and gene expression profiles characteristic of CD8+ effector T cells, and chromatin regions uniquely accessible in Nr4a triple knockout CAR tumour-infiltrating lymphocytes compared to wild type were enriched for binding motifs for NF-κB and AP-1, transcription factors involved in activation of T cells. We identify NR4A transcription factors as having an important role in the cell-intrinsic program of T cell hyporesponsiveness and point to NR4A inhibition as a promising strategy for cancer immunotherapy.

Deletion of the NR4A nuclear receptor NOR1 in hematopoietic stem cells reduces inflammation but not abdominal aortic aneurysm formation.

BACKGROUND: The NR4A3 orphan nuclear hormone receptor, NOR1, functions as a constitutively active transcription factor to regulate inflammation, proliferation, and cell survival during pathological vascular remodeling. Inflammatory processes represent key mechanisms leading to abdominal aortic aneurysm (AAA) formation. However, a role of NOR1 in AAA formation has not been investigated previously. METHODS: Inflammatory gene expression was analyzed in bone marrow-derived macrophages isolated from NOR1-deficient mice. Low-density lipoprotein receptor-deficient (LDLr-/-) mice were irradiated and reconstituted with hematopoietic stem cells obtained from NOR1-/- or wild-type littermate mice. Animals were infused with angiotensin II and fed a diet enriched in saturated fat to induce AAA formation. Quantification of AAA formation was performed by ultrasound and ex vivo measurements. RESULTS: Among 184 inflammatory genes that were analyzed, 36 genes were differentially regulated in LPS-treated NOR1-deficient macrophages. Albeit this difference in gene regulation, NOR1-deficiency in hematopoietic stem cells did not affect development of AAA formation in bone marrow-derived stem cell transplanted LDLr-deficient mice. CONCLUSION: NOR1 deletion induced differential inflammatory gene transcription in macrophages but did not influence AAA formation in mice.

Effects of 3,3',5-triiodothyronine on microglial functions.

L-tri-iodothyronine (3, 3', 5-triiodothyronine; T3) is an active form of the thyroid hormone (TH) essential for the development and function of the CNS. Though nongenomic effect of TH, its plasma membrane-bound receptor, and its signaling has been identified, precise function in each cell type of the CNS remained to be investigated. Clearance of cell debris and apoptotic cells by microglia phagocytosis is a critical step for the restoration of damaged neuron-glia networks. Here we report nongenomic effects of T3 on microglial functions. Exposure to T3 increased migration, membrane ruffling and phagocytosis of primary cultured mouse microglia. Injection of T3 together with stab wound attracted more microglia to the lesion site in vivo. Blocking TH transporters and receptors (TRs) or TRα-knock-out (KO) suppressed T3-induced microglial migration and morphological change. The T3-induced microglial migration or membrane ruffling was attenuated by inhibiting Gi /o -protein as well as NO synthase, and subsequent signaling such as phosphoinositide 3-kinase (PI3K), mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK). Inhibitors for Na(+) /K(+) -ATPase, reverse mode of Na(+) /Ca(2+) exchanger (NCX), and small-conductance Ca(2+) -dependent K(+) (SK) channel also attenuated microglial migration or phagocytosis. Interestingly, T3-induced microglial migration, but not phagocytosis, was dependent on GABAA and GABAB receptors, though GABA itself did not affect migratory aptitude. Our results demonstrate that T3 modulates multiple functional responses of microglia via multiple complex mechanisms, which may contribute to physiological and/or pathophysiological functions of the CNS.

Impaired hair growth and wound healing in mice lacking thyroid hormone receptors.

Both clinical and experimental observations show that the skin is affected by the thyroidal status. In hypothyroid patients the epidermis is thin and alopecia is common, indicating that thyroidal status might influence not only skin proliferation but also hair growth. We demonstrate here that the thyroid hormone receptors (TRs) mediate these effects of the thyroid hormones on the skin. Mice lacking TRα1 and TRß (the main thyroid hormone binding isoforms) display impaired hair cycling associated to a decrease in follicular hair cell proliferation. This was also observed in hypothyroid mice, indicating the important role of the hormone-bound receptors in hair growth. In contrast, the individual deletion of either TRα1 or TRß did not impair hair cycling, revealing an overlapping or compensatory role of the receptors in follicular cell proliferation. In support of the role of the receptors in hair growth, TRα1/TRß-deficient mice developed alopecia after serial depilation. These mice also presented a wound-healing defect, with retarded re-epithelialization and wound gaping, associated to impaired keratinocyte proliferation. These results reinforce the idea that the thyroid hormone nuclear receptors play an important role on skin homeostasis and suggest that they could be targets for the treatment of cutaneous pathologies.

TR4 promotes fatty acid synthesis in 3T3-L1 adipocytes by activation of pyruvate carboxylase expression.

We show that testicular orphan nuclear receptor 4 (TR4) increases the expression of pyruvate carboxylase (PC) gene in 3T3-L1 adipocytes by direct binding to a TR4 responsive element in the murine PC promoter. While TR4 overexpression increased PC activity, oxaloacetate (OAA) and glycerol levels with enhanced incorporation of (14)C from (14)C-pyruvate into fatty acids in 3T3-L1 adipocytes, PC knockdown by short interfering RNA (siRNA) or inhibition of PC activity by phenylacetic acid (PAA) abolished TR4-enhanced fatty acid synthesis. Moreover, TR4 microRNA reduced PC expression with decreased fatty acid synthesis in 3T3-L1 adipocytes, suggesting that TR4-mediated enhancement of fatty acid synthesis in adipocytes requires increased expression of PC gene.

Deficiency of the NR4A orphan nuclear receptor NOR1 in hematopoietic stem cells accelerates atherosclerosis.

The NR4A orphan nuclear receptor NOR1 functions as a constitutively active transcription factor regulating cellular inflammation and proliferation. In this study, we used bone marrow transplantation to determine the selective contribution of NOR1 expression in hematopoietic stem cells to the development of atherosclerosis. Reconstitution of lethally irradiated apoE(-/-) mice with NOR1-deficient hematopoietic stem cells accelerated atherosclerosis formation and macrophage recruitment following feeding a diet enriched in saturated fat. NOR1 deficiency in hematopoietic stem cells induced splenomegaly and monocytosis, specifically the abundance of inflammatory Ly6C(+) monocytes. Bone marrow transplantation studies further confirmed that NOR1 suppresses the proliferation of macrophage and dendritic progenitor (MDP) cells. Expression analysis identified RUNX1, a critical regulator of hematopoietic stem cell expansion, as a target gene suppressed by NOR1 in MDP cells. Finally, in addition to inducing Ly6C(+) monocytosis, NOR1 deletion increased the replicative rate of lesional macrophages and induced local foam cell formation within the atherosclerotic plaque. Collectively, our studies demonstrate that NOR1 deletion in hematopoietic stem cells accelerates atherosclerosis formation by promoting myelopoiesis in the stem cell compartment and by inducing local proatherogenic activities in the macrophage, including lesional macrophage proliferation and foam cell formation.

Mice lacking the p43 mitochondrial T3 receptor become glucose intolerant and insulin resistant during aging.

Thyroid hormones (TH) play an important regulatory role in energy expenditure regulation and are key regulators of mitochondrial activity. We have previously identified a mitochondrial triiodothyronine (T3) receptor (p43) which acts as a mitochondrial transcription factor of the organelle genome, which leads in vitro and in vivo, to a stimulation of mitochondrial biogenesis. Recently, we generated mice carrying a specific p43 invalidation. At 2 months of age, we reported that p43 depletion in mice induced a major defect in insulin secretion both in vivo and in isolated pancreatic islets, and a loss of glucose-stimulated insulin secretion. The present study was designed to determine whether p43 invalidation influences life expectancy and modulates blood glucose and insulin levels as well as glucose tolerance or insulin sensitivity during aging. We report that from 4 months old onwards, mice lacking p43 are leaner than wild-type mice. p43-/- mice also have a moderate reduction of life expectancy compared to wild type. We found no difference in blood glucose levels, excepted at 24 months old where p43-/- mice showed a strong hyperglycemia in fasting conditions compared to controls animals. However, the loss of glucose-stimulated insulin secretion was maintained whatever the age of mice lacking p43. If up to 12 months old, glucose tolerance remained unchanged, beyond this age p43-/- mice became increasingly glucose intolerant. In addition, if up to 12 months old p43 deficient animals were more sensitive to insulin, after this age we observed a loss of this capacity, culminating in 24 months old mice with a decreased sensitivity to the hormone. In conclusion, we demonstrated that during aging the depletion of the mitochondrial T3 receptor p43 in mice progressively induced an increased glycemia in the fasted state, glucose intolerance and an insulin-resistance several features of type-2 diabetes.

Excitatory superficial dorsal horn interneurons are functionally heterogeneous and required for the full behavioral expression of pain and itch.

To what extent dorsal horn interneurons contribute to the modality specific processing of pain and itch messages is not known. Here, we report that loxp/cre-mediated CNS deletion of TR4, a testicular orphan nuclear receptor, results in loss of many excitatory interneurons in the superficial dorsal horn but preservation of primary afferents and spinal projection neurons. The interneuron loss is associated with a near complete absence of supraspinally integrated pain and itch behaviors, elevated mechanical withdrawal thresholds and loss of nerve injury-induced mechanical hypersensitivity, but reflex responsiveness to noxious heat, nerve injury-induced heat hypersensitivity, and tissue injury-induced heat and mechanical hypersensitivity are intact. We conclude that different subsets of dorsal horn excitatory interneurons contribute to tissue and nerve injury-induced heat and mechanical pain and that the full expression of supraspinally mediated pain and itch behaviors cannot be generated solely by nociceptor and pruritoceptor activation of projection neurons; concurrent activation of excitatory interneurons is essential.

Depletion of the p43 mitochondrial T3 receptor in mice affects skeletal muscle development and activity.

In vertebrates, skeletal muscle myofibers display different contractile and metabolic properties associated with different mitochondrial content and activity. We have previously identified a mitochondrial triiodothyronine receptor (p43) regulating mitochondrial transcription and mitochondrial biogenesis. When overexpressed in skeletal muscle, it increases mitochondrial DNA content, stimulates mitochondrial respiration, and induces a shift in the metabolic and contractile features of muscle fibers toward a slower and more oxidative phenotype. Here we show that a p43 depletion in mice decreases mitochondrial DNA replication and respiratory chain activity in skeletal muscle in association with the induction of a more glycolytic muscle phenotype and a decrease of capillary density. In addition, p43(-/-) mice displayed a significant increase in muscle mass relative to control animals and had an improved ability to use lipids. Our findings establish that the p43 mitochondrial receptor strongly affects muscle mass and the metabolic and contractile features of myofibers and provides evidence that this receptor mediates, in part, the influence of thyroid hormone in skeletal muscle.

Characterization of multiple sclerosis traits: nuclear receptors (NR) impaired apoptosis pathway and the role of 1-α 25-dihydroxyvitamin D3.

Low expression of NR4A gene family members (NR4A1, NR4A3) and 1-alpha, 25-dihydroxyvitamin D(3) receptor (VDR) genes was demonstrated in peripheral blood mononuclear cells (PBMC) of subjects evaluated during the pre-disease state of multiple sclerosis (MS-to-be, MS2b), in patients with clinically isolated syndrome (CIS) during the very early presentation of neurological symptomatology and in relapsing-remitting MS (RRMS) patients. Both NR4A1 and NR4A3 are known to be involved in T-cell receptor-induced apoptosis and are regulated by VDR. We further evaluated the precise implications of apoptosis signaling regulators in relation to MS pathogenesis at the cellular level by studying the effects of 1-alpha, 25-dihydroxyvitamin D(3) (Vit D(3)) upon NR4A1 expression. We demonstrated that the low apoptotic level in MS patients was repaired by Vit D(3) mainly through NR4A1 and to a lesser extent thorough BCL2-associated X protein (BAX). These findings prove a role for Vit D(3) as a possible therapeutic intervention in MS patients aimed to activate the repressed apoptosis and enhance better control of the disease.

Mice lacking TR4 nuclear receptor develop mitochondrial myopathy with deficiency in complex I.

The estimated incidence of mitochondrial diseases in humans is approximately 1:5000 to 1:10,000, whereas the molecular mechanisms for more than 50% of human mitochondrial disease cases still remain unclear. Here we report that mice lacking testicular nuclear receptor 4 (TR4(-/-)) suffered mitochondrial myopathy, and histological examination of TR4(-/-) soleus muscle revealed abnormal mitochondrial accumulation. In addition, increased serum lactate levels, decreased mitochondrial ATP production, and decreased electron transport chain complex I activity were found in TR4(-/-) mice. Restoration of TR4 into TR4(-/-) myoblasts rescued mitochondrial ATP generation capacity and complex I activity. Further real-time PCR quantification and promoter studies found TR4 could modulate complex I activity via transcriptionally regulating the complex I assembly factor NDUFAF1, and restoration of NDUFAF1 level in TR4(-/-) myoblasts increased mitochondrial ATP generation capacity and complex I activity. Together, these results suggest that TR4 plays vital roles in mitochondrial function, which may help us to better understand the pathogenesis of mitochondrial myopathy, and targeting TR4 via its ligands/activators may allow us to develop better therapeutic approaches.

Nuclear orphan receptor TAK1/TR4-deficient mice are protected against obesity-linked inflammation, hepatic steatosis, and insulin resistance.

OBJECTIVE: The nuclear receptor TAK1/TR4/NR2C2 is expressed in several tissues that are important in the control of energy homeostasis. In this study, we investigate whether TAK1 functions as a regulator of lipid and energy homeostasis and has a role in metabolic syndrome. RESEARCH DESIGN AND METHODS: We generated TAK1-deficient (TAK1⁻(/)⁻) mice to study the function of TAK1 in the development of metabolic syndrome in aged mice and mice fed a high-fat diet (HFD). (Immuno)histochemical, biochemical, and gene expression profile analyses were performed to determine the effect of the loss of TAK1 expression on lipid homeostasis in liver and adipose tissues. In addition, insulin sensitivity, energy expenditure, and adipose-associated inflammation were compared in wild-type (WT) and TAK1⁻(/)⁻ mice fed a HFD. RESULTS: TAK1-deficient (TAK1⁻(/)⁻) mice are resistant to the development of age- and HFD-induced metabolic syndrome. Histo- and biochemical analyses showed significantly lower hepatic triglyceride levels and reduced lipid accumulation in adipose tissue in TAK1⁻(/)⁻ mice compared with WT mice. Gene expression profiling analysis revealed that the expression of several genes encoding proteins involved in lipid uptake and triglyceride synthesis and storage, including Cidea, Cidec, Mogat1, and CD36, was greatly decreased in the liver and primary hepatocytes of TAK1⁻(/)⁻ mice. Restoration of TAK1 expression in TAK1⁻(/)⁻ hepatocytes induced expression of several lipogenic genes. Moreover, TAK1⁻(/)⁻ mice exhibited reduced infiltration of inflammatory cells and expression of inflammatory genes in white adipose tissue, and were resistant to the development of glucose intolerance and insulin resistance. TAK1⁻(/)⁻ mice consume more oxygen and produce more carbon dioxide than WT mice, suggesting increased energy expenditure. CONCLUSIONS: Our data reveal that TAK1 plays a critical role in the regulation of energy and lipid homeostasis, and promotes the development of metabolic syndrome. TAK1 may provide a new therapeutic target in the management of obesity, diabetes, and liver steatosis.

Deficiency of the NR4A orphan nuclear receptor NOR1 decreases monocyte adhesion and atherosclerosis.

RATIONALE: The orphan nuclear receptor NOR1 is a member of the evolutionary highly conserved and ligand-independent NR4A subfamily of the nuclear hormone receptor superfamily. Members of this subfamily have been characterized as early response genes regulating essential biological processes including inflammation and proliferation; however, the role of NOR1 in atherosclerosis remains unknown. OBJECTIVE: The goal of the present study was to determine the causal contribution of NOR1 to atherosclerosis development and to identify the mechanism by which this nuclear receptor participates in the disease process. METHODS AND RESULTS: In the present study, we demonstrate expression of NOR1 in endothelial cells of human atherosclerotic lesions. In response to inflammatory stimuli, NOR1 expression is rapidly induced in endothelial cells through a nuclear factor kappaB-dependent transactivation of the NOR1 promoter. Overexpression of NOR1 in human endothelial cells increased the expression of vascular cell adhesion molecule (VCAM)-1 and intercellular adhesion molecule-1, whereas NOR1 deficiency altered adhesion molecule expression in response to inflammatory stimuli. Transient transfection experiments and chromatin immunoprecipitation assays revealed that NOR1 induces VCAM-1 promoter activity by binding to a canonical response element for NR4A receptors in the VCAM-1 promoter. Further functional studies confirmed that NOR1 mediates monocyte adhesion by inducing VCAM-1 and intercellular adhesion molecule-1 expression in endothelial cells. Finally, we demonstrate that NOR1 deficiency reduces hypercholesterolemia-induced atherosclerosis formation in apoE(-/-) mice by decreasing the macrophage content of the lesion. CONCLUSIONS: In concert, these studies identify a novel pathway underlying monocyte adhesion and establish that NOR1 serves a previously unrecognized atherogenic role in mice by positively regulating monocyte recruitment to the vascular wall.

Cutting edge: IL-7 regulates the peripheral pool of adult ROR gamma+ lymphoid tissue inducer cells.

During fetal life, CD4(+)CD3(-) lymphoid tissue inducer (LTi) cells are required for lymph node and Peyer's patch development in mice. In adult animals, CD4(+)CD3(-) cells are found in low numbers in lymphoid organs. Whether adult CD4(+)CD3(-) cells are LTi cells and are generated and maintained through cytokine signals has not been directly addressed. In this study we show that adult CD4(+)CD3(-) cells adoptively transferred into neonatal CXCR5(-/-) mice induced the formation of intestinal lymphoid tissues, demonstrating for the first time their bona fide LTi function. Increasing IL-7 availability in wild-type mice either by IL-7 transgene expression or treatment with IL-7/anti-IL-7 complexes increased adult LTi cell numbers through de novo generation from bone marrow cells and increased the survival and proliferation of LTi cells. Our observations demonstrate that adult CD4(+)lineage(-) cells are LTi cells and that the availability of IL-7 determines the size of the adult LTi cell pool.

The roles of testicular orphan nuclear receptor 4 (TR4) in cerebellar development.

Since Testicular Receptor 4 (TR4) was cloned, efforts have been made to elucidate its physiological function. To examine the putative functions of TR4, the conventional TR4 knockout (TR4(-/-)) mouse model was generated. Throughout postnatal and adult stages, TR4(-/-) mice exhibited behavioral deficits in motor coordination, suggesting impaired cerebellar function. Histological examination of the postnatal and adult TR4(-/-) cerebellum revealed gross abnormalities in foliation. Further analyses demonstrated changes in the lamination of the TR4(-/-) cerebellar cortex, including reduction in the thickness of both the molecular layer (ML) and the internal granule layer (IGL). Analyses of the developing TR4(-/-) cerebellum indicate that the lamination irregularities observed may result from disrupted granule cell proliferation within the external granule cell layer (EGL), delayed inward migration of post-mitotic granule cells, and increased apoptosis during cerebellar development. In addition, abnormal development of Purkinje cells was observed in the postnatal TR4(-/-) cerebellum, as indicated by aberrant dendritic arborization. In postnatal, neuronal-specific TR4 knockout mice, architectural changes in the cerebellum were similar to those seen in TR4(-/-) animals, suggesting that TR4 function in neuronal lineages might be important for cerebellar morphogenesis, and that the effect on Purkinje cell development is likely mediated by changes elsewhere, such as in granule cells, or is highly dependent on developmental stage. Together, our findings from various TR4 knockout mouse models suggest that TR4 is required for normal cerebellar development and that failure to establish proper cytoarchitecture results in dysfunction of the cerebellum and leads to abnormal behavior.

Subfertility with defective folliculogenesis in female mice lacking testicular orphan nuclear receptor 4.

Testicular orphan nuclear receptor 4 (TR4) plays essential roles for normal spermatogenesis in male mice. However, its roles in female fertility and ovarian function remain largely unknown. Here we found female mice lacking TR4 (TR4-/-) displayed subfertility and irregular estrous cycles. TR4-/- female mice ovaries were smaller with fewer or no preovulatory follicles and corpora lutea. After superovulation, TR4-/- female mice produced fewer oocytes, preovulatory follicles, and corpora lutea. In addition, more intensive granulosa apoptosis was found in TR4-/- ovaries. Functional analyses suggest that subfertility in TR4-/- female mice can be due to an ovarian defect with impaired folliculogenesis rather than a deficiency in pituitary gonadotropins. Molecular mechanism dissection of defective folliculogenesis found TR4 might induce LH receptor (LHR) gene expression via direct binding to its 5' promoter. The consequence of reduced LHR expression in TR4-/- female mice might then result in reduced gonadal sex hormones via reduced expression of enzymes involved in steroidogenesis. Together, our results showed TR4 might play essential roles in normal folliculogenesis by influencing LHR signals. Modulation of TR4 expression and/or activation via its upstream signals or unidentified ligand(s) might allow us to develop small molecule(s) to control folliculogenesis.