Rbms3, an RNA-Binding Protein, Mediates the Expression ofPtf1aby Binding to Its 3′UTR During Mouse Pancreas Development

Tumor suppressor function of RBMS3 overexpression in EOC associated with immune cell infiltration

Objectives

Epithelial ovarian cancer (EOC) is considered to be a prevalent female malignancy with both high incidence and mortality. It is reported that RNA-binding protein 3 (RBMS3) executives a tumor suppressor function in different cancers. This investigation was designed to examine the expression of RBMS3 in epithelial ovarian cancer, the effects on EOC cells, and its connection to immune cells that infiltrate tumors in the EOC microenvironment.

Methods

The expression levels of RBMS3 in EOC tissues as well as their correlations with immune cell infiltration and clinical outcome were examined using bioinformatics approaches. Western blotting as well as immunohistochemistry were carried out to determine the protein levels in EOC tissues. In addition, qRT-PCR was employed to look at the expression of the mRNA. The role of RBMS3 in EOC cells was investigated, and an RBMS3 lentiviral vector was developed. The effects of RBMS3 on subcutaneous tumor development, the proliferation protein Ki-67, the tumor angiogenesis indicator CD31, and its function in controlling the tumor immune microenvironment were evaluated by in vivo tests.

Results

There was a considerable decrease in RBMS3 expression in EOC tissues, which was linked to a poor prognosis for patients and the infiltration of multiple immune cell. Given immunohistochemical studies, tissues with increased RBMS3 expression had decreased markers of myeloid-derived suppressor cells, regulatory T cells, and M2 macrophages, whereas M1 macrophage markers were elevated. RBMS3 appears to suppress the capabilities of proliferating, invading, and migrating in EOC cells according to in vitro tests, whereas tumors overexpressing RBMS3 developed more slowly in syngeneic mouse models. The overexpression of RBMS3 led to a decline in the levels of Ki-67 protein and CD31. Additionally, it showed a negatively correlation with markers of regulatory T cell, myeloid-derived suppressor cell, and M2 macrophage but a positive correlation with markers of M1 macrophage.

Conclusions

The findings revealed that elevated RBMS3 expression plays a tumor suppressor role in EOC and was connected to patient survival in EOC. The studies conducted in vitro and in vivo demonstrated a link between RBMS3 expression and the infiltration of certain immune cells, indicating a function for RBMS3 in the immunosuppressive tumor microenvironment and its promising efficiency as a novel target for immunotherapy against EOC.

Expression of RBMS3 in Breast Cancer Progression

The aim of the study was to evaluate the localization and intensity of RNA-binding motif single-stranded-interacting protein 3 (RBMS3) expression in clinical material using immunohistochemical (IHC) reactions in cases of ductal breast cancer (in vivo), and to determine the level of RBMS3 expression at both the protein and mRNA levels in breast cancer cell lines (in vitro). Moreover, the data obtained in the in vivo and in vitro studies were correlated with the clinicopathological profiles of the patients. Material for the IHC studies comprised 490 invasive ductal carcinoma (IDC) cases and 26 mastopathy tissues. Western blot and RT-qPCR were performed on four breast cancer cell lines (MCF-7, BT-474, SK-BR-3 and MDA-MB-231) and the HME1-hTERT (Me16C) normal immortalized breast epithelial cell line (control). The Kaplan-Meier plotter tool was employed to analyze the predictive value of overall survival of RBMS3 expression at the mRNA level. Cytoplasmatic RBMS3 IHC expression was observed in breast cancer cells and stromal cells. The statistical analysis revealed a significantly decreased RBMS3 expression in the cancer specimens when compared with the mastopathy tissues (p < 0.001). An increased expression of RBMS3 was corelated with HER2(+) cancer specimens (p < 0.05) and ER(-) cancer specimens (p < 0.05). In addition, a statistically significant higher expression of RBMS3 was observed in cancer stromal cells in comparison to the control and cancer cells (p < 0.0001). The statistical analysis demonstrated a significantly higher expression of RBMS3 mRNA in the SK-BR-3 cell line compared with all other cell lines (p < 0.05). A positive correlation was revealed between the expression of RBMS3, at both the mRNA and protein levels, and longer overall survival. The differences in the expression of RBMS3 in cancer cells (both in vivo and in vitro) and the stroma of breast cancer with regard to the molecular status of the tumor may indicate that RBMS3 could be a potential novel target for the development of personalized methods of treatment. RBMS3 can be an indicator of longer overall survival for potential use in breast cancer diagnostic process.

Disruption of RBMS3 suppresses PD-L1 and enhances antitumor immune activities and therapeutic effects of auranofin against triple-negative breast cancer

Programmed cell death protein-1 (PD-1)/programmed cell death ligand-1 (PD-L1) interaction exerts a vital role in tumor-associated immune evasion. While strategies disrupting PD-1/PD-L1 axis have shown clinical benefits in various cancers, the limited response rate prompts us to investigate the complex mechanisms underlying the molecular regulation of PD-L1. Here, we identify the RNA binding protein RBMS3 as a crucial PD-L1 regulator in triple-negative breast cancer (TNBC). Correlation analysis shows that Rbms3 significantly correlates with immunosuppressive CD274, Rbms1, NT5E and ENTPD1. RBMS3 protein binds to CD274 mRNA specifically in TNBC cells to increase PD-L1 levels. Mechanistically, RBMS3 stabilizes CD274 mRNA by interacting with its 3'UTR, which represents as an intrinsic cancer cell mechanism for driving PL-D1 upregulation in TNBC. RBMS3 depletion not only destabilizes the mRNA stability and protein expression of PD-L1, but also suppresses the migratory abilities of TNBC MDA-MB-231 cells. Importantly, combination of RBMS3 ablation with auranofin (AUF), an FDA-approved thioredoxin reductase inhibitor, facilitates anti-tumor T-cell immunity in vivo and improves AUF-mediated anti-cancer effect. Taken together, our findings reveal RBMS3 as a key post-transcriptional regulator of PD-L1 and how they contribute to immune escape in TNBC, which could lead to novel combinatorial therapeutic strategies to enhance the efficacy of cancer immunotherapy.

Role of RBMS3 Novel Potential Regulator of the EMT Phenomenon in Physiological and Pathological Processes

RNA-binding protein 3 (RBMS3) plays a significant role in embryonic development and the pathogenesis of many diseases, especially cancer initiation and progression. The multiple roles of RBMS3 are conditioned by its numerous alternative expression products. It has been proven that the main form of RBMS3 influences the regulation of microRNA expression or stabilization. The absence of RBMS3 activates the Wnt/β-catenin pathway. The expression of c-Myc, another target of the Wnt/β-catenin pathway, is correlated with the RBMS3 expression. Numerous studies have focused solely on the interaction of RBMS3 with the epithelial-mesenchymal transition (EMT) protein machinery. EMT plays a vital role in cancer progression, in which RBMS3 is a new potential regulator. It is also significant that RBMS3 may act as a prognostic factor of overall survival (OS) in different types of cancer. This review presents the current state of knowledge about the role of RBMS3 in physiological and pathological processes, with particular emphasis on carcinogenesis. The molecular mechanisms underlying the role of RBMS3 are not fully understood; hence, a broader explanation and understanding is still needed.

New Insights on the Regulation of the Insulin-Degrading Enzyme: Role of microRNAs and RBPs

The evident implication of the insulin-degrading enzyme (IDE) in Alzheimer’s disease (AD) and type 2 diabetes mellitus (T2DM), among its capacity to degrade insulin and amyloid-β peptide (Aβ), suggests that IDE could be an essential link in the relation between hyperinsulinemia, insulin resistance and AD. However, little is known about the cellular and molecular regulation of IDE expression, and even less has been explored regarding the post-transcriptional regulation of IDE, although it represents a great molecular target of interest for therapeutic treatments. We recently described that miR-7, a novel candidate for linking AD and T2DM at the molecular level, regulates IDE and other key genes in both pathologies, including some key genes involved in the insulin signaling pathway. Here, we explored whether other miRNAs as well as other post-transcriptional regulators, such as RNA binding proteins (RBP), could potentially participate in the regulation of IDE expression in vitro. Our data showed that in addition to miR-7, miR-125, miR-490 and miR-199 regulate IDE expression at the post-transcriptional level. Moreover, we also found that IDE contains multiple potential binding sites for several RBPs, and a narrow-down prediction analysis led us to speculate on a novel regulation of IDE by RALY and HuD. Taken together, these results demonstrate the novel players controlling IDE expression that could represent potential therapeutical targets to treat several metabolic diseases with a high impact on human health, including AD and T2DM.

RNA binding protein RBMS3 is a common EMT effector that modulates triple-negative breast cancer progression via stabilizing PRRX1 mRNA

The epithelial-to-mesenchymal transition (EMT) has been recognized as a driving force for tumor progression in breast cancer. Recently, our group identified the RNA Binding Motif Single Stranded Interacting Protein 3 (RBMS3) to be significantly associated with an EMT transcriptional program in breast cancer. Additional expression profiling demonstrated that RBMS3 was consistently upregulated by multiple EMT transcription factors and correlated with mesenchymal gene expression in breast cancer cell lines. Functionally, RBMS3 was sufficient to induce EMT in two immortalized mammary epithelial cell lines. In triple-negative breast cancer (TNBC) models, RBMS3 was necessary for maintaining the mesenchymal phenotype and invasion and migration in vitro. Loss of RBMS3 significantly impaired both tumor progression and spontaneous metastasis in vivo. Using a genome-wide approach to interrogate mRNA stability, we found that ectopic expression of RBMS3 upregulates many genes that are resistant to degradation following transcriptional blockade by actinomycin D (ACTD). Specifically, RBMS3 was shown to interact with the mRNA of EMT transcription factor PRRX1 and promote PRRX1 mRNA stability. PRRX1 is required for RBMS3-mediated EMT and is partially sufficient to rescue the effect of RBMS3 knockdown in TNBC cell lines. Together, this study identifies RBMS3 as a novel and common effector of EMT, which could be a promising therapeutic target for TNBC treatment.

Roles of Plant Glycine-Rich RNA-Binding Proteins in Development and Stress Responses

In recent years, much progress has been made in elucidating the functional roles of plant glycine-rich RNA-binding proteins (GR-RBPs) during development and stress responses. Canonical GR-RBPs contain an RNA recognition motif (RRM) or a cold-shock domain (CSD) at the N-terminus and a glycine-rich domain at the C-terminus, which have been associated with several different RNA processes, such as alternative splicing, mRNA export and RNA editing. However, many aspects of GR-RBP function, the targeting of their RNAs, interacting proteins and the consequences of the RNA target process are not well understood. Here, we discuss recent findings in the field, newly defined roles for GR-RBPs and the actions of GR-RBPs on target RNA metabolism.

Tumor Suppressor Effect of RBMS3 in Breast Cancer

Background:

RBMS3 (RNA-binding motif, single-stranded-intervacting protein 3) acts as a tumor-suppressive gene in a number of human cancers, however, its role in breast cancer is not fully understood. This study aimed to investigate the expression and clinicopathological significance of RBMS3 in breast cancer.

Methods:

A total of 998 breast cancer tissue samples in The Cancer Genome Atlas (TCGA) database with survival outcomes were divided into high RBMS3 expression and low expression groups using the median as the cutoff. Clinicopathological characteristics and prognosis were compared between the 2 groups.

Results:

TCGA showed that RBMS3 mRNA was downregulated in breast cancer tissues, and RBMS3 downregulation was correlated with poor prognosis. Immunohistochemistry staining of 127 paraffin-embedded breast cancer tissues showed that RBMS3 protein was localized in the cytoplasm and nucleus; however, nuclear staining was present in 90.0% of normal breast tissues but only 28.3% of breast cancer tissues. Decreased RBMS3 protein expression was significantly correlated with estrogen receptor (ER)-negative status and death at final follow-up. Patients with lower RBMS3 protein expression had substantially shorter survival than those with higher RBMS3 expression. Univariate and multivariate analysis indicated that the combination of RBMS3 expression and ER status (a variable designated as “cofactor”) was an independent prognostic factor in patients with breast cancer (hazard ratio [HR] = 0.420, 95% confidence interval [CI]: 0.223-0.791, P = 0.007).

Conclusion:

RBMS3 downregulation was correlated with poor prognosis in breast cancer patients, and the combination of RBMS3 expression and ER status was an independent prognostic factor.

LncRNA MEG3 regulates breast cancer proliferation and apoptosis through miR-141-3p/RBMS3 axis

Maternally expressed 3 (MEG3) and RNA binding motif single stranded interacting protein 3 (RBMS3) are abnormally expressed in breast cancer susceptibility genes (BRCA), but the mechanism of the two in breast cancer (BC) is unclear. By performing in vivo and in vitro experiments, we found that MEG3 and RBMS3 were low-expressed, negatively correlated with high-expressed miR-141-3p, were positively correlated with each other in BC. MEG3 targeted miR-141-3p, and miR-141-3p targeted RBMS3. MEG3, which was mainly distributed in BC cytoplasm, could down-regulate miR-141-3p and up-regulate RBMS3, and reverse effect of miR-141-3p on related gene expressions and on promoting cancer development. Overexpressed MEG3 inhibited growth of xenografts, promoted cell apoptosis via regulating apoptosis related factors, and up-regulated RBMS3 expression but down-regulated miR-141-3p. The findings of this study showed that MEG3 inhibited proliferation and promoted apoptosis of BC cells through the miR-141-3p/RBMS3 axis, and MEG3 inhibited growth of xenografts through miR-141-3p.

Genome-wide association studies for the concentrations of insulin, triiodothyronine, and thyroxine in Chinese Holstein cattle

To further understand the genetic structure that is associated with insulin (INS) and thyroid hormones (TH), including triiodothyronine (T₃) and thyroxine (T₄), in Chinese Holstein cows, we conducted a genome-wide association study (GWAS) of thyroid hormones and insulin in cows. We conducted GWAS analysis on 1217 Chinese Holstein cows raised in southern China and found 19 significant single nucleotide polymorphisms (SNPs) in this study: 10 SNPs were associated with INS, 5 SNPs were associated with T₃, and 4 SNPs were associated with T₄. In our study, the GWAS method was used for preliminary screening on related genes of traits, and due to insufficient relevant literature, a functional analysis of genes could only be based on human studies. We observed that DGKB from Bos taurus chromosome (BTA)4 is strongly associated with insulin secretion. We found that EXOC4 gene was significantly correlated with T₃ and T₄ traits. Another significant SNP was located in the CYP7A1 gene, which has been confirmed to be affected by thyroid hormones.

Transcription factor Ptf1a in development, diseases and reprogramming

The transcription factor Ptf1a is a crucial helix-loop-helix (bHLH) protein selectively expressed in the pancreas, retina, spinal cord, brain, and enteric nervous system. Ptf1a is preferably assembled into a transcription trimeric complex PTF1 with an E protein and Rbpj (or Rbpjl). In pancreatic development, Ptf1a is indispensable in controlling the expansion of multipotent progenitor cells as well as the specification and maintenance of the acinar cells. In neural tissues, Ptf1a is transiently expressed in the post-mitotic cells and specifies the inhibitory neuronal cell fates, mostly mediated by downstream genes such as Tfap2a/b and Prdm13. Mutations in the coding and non-coding regulatory sequences resulting in Ptf1a gain- or loss-of-function are associated with genetic diseases such as pancreatic and cerebellar agenesis in the rodent and human. Surprisingly, Ptf1a alone is sufficient to reprogram mouse or human fibroblasts into tripotential neural stem cells. Its pleiotropic functions in many biological processes remain to be deciphered in the future.

RBMS2 inhibits the proliferation by stabilizing P21 mRNA in breast cancer

Background

RNA binding proteins (RBPs) play an important role in regulating the metabolism of target RNAs. Aberrant expression of RBPs plays a vital role in the initiation and development of many cancers. The RBM family, which has the conserved RNA binding motif RNP1 and RNP2, shares the similar function in RNA processing and RBMS2 is a member of them. P21, also named CDKN1A, promotes cell cycle arrest and plays an important role in halting cell proliferation. In our study, we identified RBMS2 as a tumor suppressor in breast cancer. It inhibited the proliferation of breast cancer by positively regulating the stability of P21 mRNA in posttranscriptional way.

Methods

TCGA was used to identify differentially expressed RBPs in breast cancer.

The effect of RBMS2 on breast cancer proliferation was evaluated in vitro using CCK-8 assays, colony formation assays and cell-cycle assays and the in vivo effect was investigated using a mouse tumorigenicity model.

The main pathway and genes regulated by RBMS2 was detected by RNA sequencing. The RNA immunoprecipitation combined with dual-luciferase reporter assay were conducted to testify the direct binding between RBMS2 and P21. Rescue assay was used to detect P21 as the main target of RBMS2.

Results

The expression of RBMS2 was lower in breast cancer compared with normal tissues and was a favorable biomarker in breast cancer. RBMS2 inhibited the proliferation of breast cancer and P21 was the main target of RBMS2. RBMS2 stabilized the mRNA of P21 by directly binding to the AU-rich element of 3′-UTR region. Anti-proliferation activity induced by overexpression of RBMS2 was rescued by interfering with the expression of P21.

Conclusion

In conclusion, RBMS2 acted as a tumor suppressor in breast cancer and positively regulated the expression of P21 by stabilizing its mRNA.

Electronic supplementary material

The online version of this article (10.1186/s13046-018-0968-z) contains supplementary material, which is available to authorized users.

Loss of RBMS3 Confers Platinum Resistance in Epithelial Ovarian Cancer via Activation of miR-126-5p/β-catenin/CBP signaling

PURPOSE

The development of resistance to platinum-based chemotherapy remains the unsurmountable obstacle in cancer treatment and consequently leads to tumor relapse. This study aims to investigate the mechanism by which loss of RBMS3 induced chemoresistance in epithelial ovarian cancer (EOC).

EXPERIMENTAL DESIGN

FISH and IHC were used to determine deletion frequency and expression of RBMS3 in 15 clinical EOC tissues and 150 clinicopathologically characterized EOC specimens. The effects of RBMS3 deletion and CBP/β-catenin antagonist PRI-724 in chemoresistance were examined by clone formation and Annexin V assays in vitro, and by intraperitoneal tumor model in vivo. The mechanism by which RBMS3 loss sustained activation of miR-126-5p/β-catenin/CBP signaling and the effects of RBMS3 and miR-126-5p competitively regulating DKK3, AXIN1, BACH1, and NFAT5 was explored using CLIP-seq, RIP, electrophoretic mobility shift, and immunoblotting and immunofluorescence assays.

RESULTS

Loss of RBMS3 in EOC was correlated with the overall and relapse-free survival. Genetic ablation of RBMS3 significantly enhanced, whereas restoration of RBMS3 reduced, the chemoresistance ability of EOC cells both in vitro and in vivo. RBMS3 inhibited β-catenin/CBP signaling through directly associating with and stabilizing multiple negative regulators, including DKK3, AXIN1, BACH1, and NFAT5, via competitively preventing the miR-126-5p-mediated repression of these transcripts. Importantly, cotherapy of CBP/β-catenin antagonist PRI-724 induced sensitization of RBMS3-deleted EOC to platinum therapy.

CONCLUSIONS

Our results demonstrate that genetic ablation of RBMS3 contributes to chemoresistance and PRI-724 may serve as a potential tailored treatment for patients with RBMS3-deleted EOC.

Identification of transcription factors that may reprogram lung adenocarcinoma

BACKGROUND

Lung adenocarcinoma is one of most threatening disease to human health. Although many efforts have been devoted to its genetic study, few researches have been focused on the transcription factors which regulate tumor initiation and progression by affecting multiple downstream gene transcription. It is proved that proper transcription factors may mediate the direct reprogramming of cancer cells, and reverse the tumorigenesis on the epigenetic and transcription levels.

METHODS

In this paper, a computational method is proposed to identify the core transcription factors that can regulate as many as possible lung adenocarcinoma associated genes with as little as possible redundancy. A greedy strategy is applied to find the smallest collection of transcription factors that can cover the differentially expressed genes by its downstream targets. The optimal subset which is mostly enriched in the differentially expressed genes is then selected.

RESULTS

Seven core transcription factors (MCM4, VWF, ECT2, RBMS3, LIMCH1, MYBL2 and FBXL7) are detected, and have been reported to contribute to tumorigenesis of lung adenocarcinoma. The identification of the transcription factors provides a new insight into its oncogenic role in tumor initiation and progression, and benefits the discovery of functional core set that may reverse malignant transformation and reprogram cancer cells.

The E3 ubiquitin ligase thyroid hormone receptor-interacting protein 12 targets pancreas transcription factor 1a for proteasomal degradation

Pancreas transcription factor 1a (PTF1a) plays a crucial role in the early development of the pancreas and in the maintenance of the acinar cell phenotype. Several transcriptional mechanisms regulating expression of PTF1a have been identified. However, regulation of PTF1a protein stability and degradation is still unexplored. Here, we report that inhibition of proteasome leads to elevated levels of PTF1a and to the existence of polyubiquitinated forms of PTF1a. We used the Sos recruitment system, an alternative two-hybrid system method to detect protein-protein interactions in the cytoplasm and to map the interactome of PTF1a. We identified TRIP12 (thyroid hormone receptor-interacting protein 12), an E3 ubiquitin-protein ligase as a new partner of PTF1a. We confirmed PTF1a/TRIP12 interaction in acinar cell lines and in co-transfected HEK-293T cells. The protein stability of PTF1a is significantly increased upon decreased expression of TRIP12. It is reduced upon overexpression of TRIP12 but not a catalytically inactive TRIP12-C1959A mutant. We identified a region of TRIP12 required for interaction and identified lysine 312 of PTF1a as essential for proteasomal degradation. We also demonstrate that TRIP12 down-regulates PTF1a transcriptional and antiproliferative activities. Our data suggest that an increase in TRIP12 expression can play a part in PTF1a down-regulation and indicate that PTF1a/TRIP12 functional interaction may regulate pancreatic epithelial cell homeostasis.

Pancreatic differentiation of human dental pulp CD117⁺ stem cells

AIM

Adult stem cells cannot proliferate to produce enough cells for human transplantation with keeping stem cell characteristics shown in the primary culture. We established a novel culture protocol using human dental pulp stem cells (DPSCs) that can produce quantities sufficient for human transplantation. The present study assessed differentiation of DPSCs toward a pancreatic lineage in serum-free conditions, which is essential for safe transplantation.

MATERIALS & METHODS

CD117⁺ stem cells were separated from human exfoliated deciduous teeth (stem cells from human exfoliated deciduous teeth; SHED) and adult DPSCs. The cells were characterized with real-time reverse-transcription PCR for a panel of embryonal lineage markers.

RESULTS

82 out of 84 markers were expressed in different levels in SHED or DPSCs. After pancreatic differentiation in vitro, we found expression of pancreatic-specific endocrine markers insulin, glucagon, somatostatin and pancreatic polypeptide, and exocrine marker amylase-2a in both cultures. We also found reprogramming in both cell cultures mimicking the embryonal stages of development of the pancreas. Transcription factors PDX1, HHEX, MNX1, NEUROG3, PAX4, PAX6 and NKX6-1, crucial markers for the pancreatic development, were all activated. Expression of these factors strongly implies that the cells differentiated toward a distinguished pancreatic lineage.

CONCLUSION

Our results show that CD117⁺ SHED and DPSCs are capable of differentiation toward all functional endocrine and exocrine subsets of pancreatic cells in serum-free conditions. SHED and DPSCs may therefore have great potential for future cell therapy of pancreatic disorders.

Genetic mapping with multiple levels of phenotypic information reveals determinants of lymphocyte glucocorticoid sensitivity

Clinical response to glucocorticoids, steroid hormones widely used as pharmaceuticals, varies extensively in that many individuals (∼30%) show a weak response to treatment. Although little is known about the molecular basis of this variation, regulatory polymorphisms are likely to play a key role given that glucocorticoids act largely through activation of a transcription factor, the glucocorticoid receptor. In an effort to characterize the molecular basis of variation in glucocorticoid sensitivity, we measured in vitro lymphocyte glucocorticoid sensitivity and transcriptome-wide response to glucocorticoids in peripheral-blood mononuclear cells from African American healthy donors. We found that variation in lymphocyte glucocorticoid sensitivity was correlated with transcriptional response at 27 genes (false-discovery rate < 0.1). Furthermore, a genome-wide association scan revealed a quantitative trait locus (QTL) for lymphocyte glucocorticoid sensitivity (rs11129354, p = 4 × 10(-8)); it was also associated with transcriptional response at multiple genes, including many (14/27) where transcriptional response was correlated with lymphocyte glucocorticoid sensitivity. Using allelic-imbalance assays, we show that this QTL is a glucocorticoid-dependent cis-regulatory polymorphism for RBMS3, which encodes an RNA-binding protein known as a tumor suppressor. We found that siRNA-mediated knockdown of RBMS3 expression increased cellular proliferation in PBMCs, consistent with the role of the gene as a negative regulator of proliferation. We propose that differences in lymphocyte glucocorticoid sensitivity reflect variation in transcriptional response, which is influenced by a glucocorticoid-dependent regulatory polymorphism that acts in cis relative to RBMS3 and in trans to affect the transcriptional response of multiple distant genes.

Rbms3 functions in craniofacial development by posttranscriptionally modulating TGF-β signaling

Rbms3 regulates TGF-βr signaling, a critical pathway for chondrogenesis, by binding and stabilizing Smad2 transcripts.

Cranial neural crest cells form much of the facial skeleton, and abnormalities in their development lead to severe birth defects. In a novel zebrafish protein trap screen, we identified an RNA-binding protein, Rbms3, that is transiently expressed in the cytoplasm of condensing neural crest cells within the pharyngeal arches. Morphants for rbms3 displayed reduced proliferation of prechondrogenic crest and significantly altered expression for chondrogenic/osteogenic lineage markers. This phenotype strongly resembles cartilage/crest defects observed in Tgf-βr2:Wnt1-Cre mutants, which suggests a possible link with TGF-β signaling. Consistent with this are the findings that: (a) Rbms3 stabilized a reporter transcript with smad2 3′ untranslated region, (b) RNA immunoprecipitation with full-length Rbms3 showed enrichment for smad2/3, and (c) pSmad2 levels were reduced in rbms3 morphants. Overall, these results suggest that Rbms3 posttranscriptionally regulates one of the major pathways that promotes chondrogenesis, the transforming growth factor β receptor (TGF-βr) pathway.