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The molecular mechanisms allowing hair follicles to periodically activate their stem cells (HFSCs) are incompletely characterized. Here, we identify the transcription factor IRX5 as a promoter of HFSC activation. Irx5-/- mice have delayed anagen onset, with increased DNA damage and diminished HFSC proliferation. Open chromatin regions form near cell cycle progression and DNA damage repair genes in Irx5-/- HFSCs. DNA damage repair factor BRCA1 is an IRX5 downstream target. Inhibition of FGF kinase signaling partially rescues the anagen delay in Irx5-/- mice, suggesting that the Irx5-/- HFSC quiescent phenotype is partly due to failure to suppress Fgf18 expression. Interfollicular epidermal stem cells also show decreased proliferation and increased DNA damage in Irx5-/-mice. Consistent with a role for IRX5 as a promoter of DNA damage repair, we find that IRX genes are upregulated in many cancer types and that there is a correlation between IRX5 and BRCA1 expression in breast cancer.

Previous studies have established that transmural gradients of the fast transient outward K+ current (Ito,f) correlate with regional differences in action potential (AP) profile and excitation-contraction coupling (ECC) with high Ito,f expression in the epimyocardium (EPI) being associated with short APs and low contractility and vice versa. Herein, we investigated the effects of altering the Ito,f gradients on transmural contractile properties using mice lacking Irx5 (Irx5-KO) or lacking Kcnd2 (KV4.2-KO) or both. Irx5- KO mice exhibited decreased global LV contractility in association with elevated Ito,f, as well as reduced cell shortening and Ca2+ transient amplitudes in cardiomyocytes isolated from the endomyocardium (ENDO) but not in cardiomyocytes from the EPI. Transcriptional profiling revealed that the primary effect of Irx5 ablation on ECC-related genes was to increase Ito,f gene expression (i.e., Kcnd2 and Kcnip2) in the ENDO, but not the EPI. By contrast, KV4.2-KO mice showed selective increases in cell shortening and Ca2+ transients in isolated EPI cardiomyocytes, leading to enhanced ventricular contractility and mice lacking both Irx5 and Kcnd2 displayed elevated ventricular contractility, comparable to KV4.2-KO mice, demonstrating a dominant role of Irx5- dependent modulation of Ito,f in the regulation of contractility. Our findings show that the transmural electromechanical heterogeneities in the healthy ventricles depend on the Irx5-dependent Ito,f gradients. These observations provide a useful framework for assessing the molecular mechanisms underlying the alterations in contractile heterogeneity seen in the diseased heart. [ABSTRACT FROM AUTHOR]

Aims Several inherited arrhythmic diseases have been linked to single gene mutations in cardiac ion channels and interacting proteins. However, the mechanisms underlying most arrhythmias, are thought to involve altered regulation of the expression of multiple effectors. In this study, we aimed to examine the role of a transcription factor (TF) belonging to the Iroquois homeobox family, IRX5, in cardiac electrical function. Methods and results Using human cardiac tissues, transcriptomic correlative analyses between IRX5 and genes involved in cardiac electrical activity showed that in human ventricular compartment, IRX5 expression strongly correlated to the expression of major actors of cardiac conduction, including the sodium channel, Nav1.5, and Connexin 40 (Cx40). We then generated human-induced pluripotent stem cells (hiPSCs) derived from two Hamamy syndrome-affected patients carrying distinct homozygous loss-of-function mutations in IRX5 gene. Cardiomyocytes derived from these hiPSCs showed impaired cardiac gene expression programme, including misregulation in the control of Nav1.5 and Cx40 expression. In accordance with the prolonged QRS interval observed in Hamamy syndrome patients, a slower ventricular action potential depolarization due to sodium current reduction was observed on electrophysiological analyses performed on patient-derived cardiomyocytes, confirming the functional role of IRX5 in electrical conduction. Finally, a cardiac TF complex was newly identified, composed by IRX5 and GATA4, in which IRX5 potentiated GATA4-induction of SCN5A expression. Conclusion Altogether, this work unveils a key role for IRX5 in the regulation of human ventricular depolarization and cardiac electrical conduction, providing therefore new insights into our understanding of cardiac diseases. [ABSTRACT FROM AUTHOR]

Obesity has become a genuine global pandemic due to lifestyle and environmental modifications, and is associated with chronic lethal comorbidities. Various environmental factors such as lack of physical activity due to modernization and higher intake of energy‐rich diets are primary obesogenic factors in pathogenesis of obesity. Genome‐wide association study has identified the crucial role of FTO (fat mass and obesity) in human obesity. A bunch of SNPs in the first intron of FTO has been identified and subsequently correlated to body mass index and body composition. Findings of in silico, in vitro, and in vivo studies have manifested the robust role of FTO in regulation of energy expenditure and food consumption. Numerous studies have highlighted the mechanistic pathways behind the concomitant functions of FTO in adipogenesis and body size. Current investigation has also revealed the link of FTO neighbouring genes i.e., RPGRIP1L, IRX3 and IRX5 and epigenetic factors with obesity phenotypes. The motive behind this review is to cite the consequences of FTO on obesity vulnerability. [ABSTRACT FROM AUTHOR]

Background/Aims: The long-noncoding RNA colorectal neoplasia differentially expressed (CRNDE) gene was first found to be activated in colorectal neoplasia. Now, it also has been found to be upregulated in many other solid tumors. Whether CRNDE affects tumorigenesis remains unknown. Methods: We conducted bioinformatics, real-time polymerase chain reaction (PCR), Western blot analysis, cell proliferation assay, colony formation assay, wound healing assay, cell migration and invasion assays, RNA immunoprecipitation, and reporter vector construction and luciferase assays. Results: CRNDE was upregulated in hepatocellular carcinoma (HCC). The overexpression of CRNDE promoted HCC cellular proliferation, migration, and invasion in intro and in vivo, and acted as an oncogene in HCC progression. Furthermore, CRNDE impaired miR-136-5P expression in a RISC manner, and a reciprocal repression feedback loop was possible between CRNDE and miR-136-5P. We found that the neighboring mRNA of CRNDE was IRX5, and IRX5 increased the tumorigenicity of HCC cells. IRX5 was a potential downstream target gene of miR-136-5P. MiR-136 regulated IRX5 by interacting with its 3’UTR. In addition, miR-136-5P was involved in the CRNDE-regulated expression of IRX5. Conclusion: CRNDE acted as a tumor oncogene by exhibiting oncogenic properties of human HCC and revealed a novel CRNDE-miR-136-5P-IRX5 regulatory network in HCC. CRNDE may be considered to be a potential target for HCC therapies based on its ability to upregulate IRX5, and it deserves further investigation.

Hepatocellular carcinoma (HCC) is the fifth most common cancer worldwide and the third most frequent cause of cancer‐related death. The IRX5 transcription factor plays a different role in multiple cancers and contributes to the development of many tumours. However, little is known about the molecular mechanisms of IRX5 in HCC. In this study, we found that IRX5 was abnormally upregulated in HCC tissues compared with adjacent normal tissues. IRX5 promoted HCC cell proliferation and upregulated the expression of cyclin D1 and knockdown of IRX5 suppressed tumorigenicity in vivo. Furthermore, knockdown of IRX5 increased p53 and Bax expression and decreased Bcl‐2 expression. Thus, IRX5 suppressed apoptosis in HCC cells by inhibiting the p53 signalling pathway, indicating its role as a treatment target for HCC. Significance of the study: Our study demonstrated that IRX5 was abnormally upregulated in HCC tissues compared with adjacent normal tissues. IRX5 promoted HCC cell proliferation and upregulated the expression of cyclin D1, and knockdown of IRX5 suppressed tumorigenicity in vivo. Furthermore, knockdown of IRX5 increased p53 and Bax expression and decreased Bcl‐2 expression. IRX5 suppressed apoptosis in HCC cells by inhibiting the p53 signalling pathway, indicating its role as a treatment target for HCC. [ABSTRACT FROM AUTHOR]

To investigate the effect of IRX5 on the invasion and migration of hepatocellular carcinoma (HCC) cells and verify the targeted relationship between miR-136-5p and IRX5. Methods The SMMC7721 cells were divided into empty plasmid (pcDNA3.1) group and overexpress IRX5 (pcDNA3.1-IRX5) group in the overexpression IRX5 experiment. For knockdown IRX5 experiment a negative control (sh-NC) group and knockdown IRX5 (sh-IRX5) group were set up. The overexpression and knockdown efficiency rates of IRX5 were detected by Western blot assay. The effects of IRX5 on the invasion and migration of HCC cells were detected by wound healing assay and Transwell assay. miRNA and binding sites of IRX5 were predicted by miRanda and Targetscan. The 3' untranslated regions (UTR) of IRX5 were amplified by PCR and connected to pGL3-Control vector. To verified recombinant plasmid by enzyme digestion and gene sequencing methods. The 293T cells were divided into four groups: IRX5-3'UTR-Wt+NC group, IRX5-3'UTR-Wt+miR-136-5p group, IRX5- 3'UTR-Mut+NC group and IRX5-3'UTR-Mut+miR-136-5p group in dual luciferase assay. The luciferase activity was detected by dual luciferase reporter system. Results The expression level of IRX5 was significantly higher in the overexpression IRX5 group than that of the empty plasmid group (P＜0.05). Compared with the negative control group, the expression level of IRX5 was significantly reduced in the knockdown IRX5 group (P＜0.01). IRX5 promoted the invasion and migration of HCC cells (P＜0.05). The IRX5-3'UTR-Wt and IRX5-3'UTR-Mut were successfully constructed. The results of dual luciferase assay showed that miR-136-5p can reduce IRX5-3'UTR-Wt luciferase activity (P＜0.01), which showed no effect on IRX5-3'UTR-Mut luciferase activity (P＞0.05). Conclusion IRX5 promotes the invasion and migration of HCC cells. IRX5 acts as a target gene of miR-136-5p. miR-136-5p may inhibit the invasion and migration of HCC cells through the 3'UTR of IRX5. [ABSTRACT FROM AUTHOR]

Wilms tumour is a paediatric malignancy with features of halted kidney development. Here, we demonstrate that the Iroquois homeobox genes IRX3 and IRX5 are essential for mammalian nephrogenesis and govern the differentiation of Wilms tumour. Knock‐out Irx3−/Irx5− mice showed a strongly reduced embryonic nephron formation. In human foetal kidney and Wilms tumour, IRX5 expression was already activated in early proliferative blastema, whereas IRX3 protein levels peaked at tubular differentiation. Accordingly, an orthotopic xenograft mouse model of Wilms tumour showed that IRX3−/− cells formed bulky renal tumours dominated by immature mesenchyme and active canonical WNT/β‐catenin‐signalling. In contrast, IRX5−/− cells displayed activation of Hippo and non‐canonical WNT‐signalling and generated small tumours with abundant tubulogenesis. Our findings suggest that promotion of IRX3 signalling or inhibition of IRX5 signalling could be a route towards differentiation therapy for Wilms tumour, in which WNT5A is a candidate molecule for enforced tubular maturation. © 2018 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland. [ABSTRACT FROM AUTHOR]

Background/Aims: The long-noncoding RNA colorectal neoplasia differentially expressed (CRNDE) gene was first found to be activated in colorectal neoplasia. Now, it also has been found to be upregulated in many other solid tumors. Whether CRNDE affects tumorigenesis remains unknown. Methods: We conducted bioinformatics, real-time polymerase chain reaction (PCR), Western blot analysis, cell proliferation assay, colony formation assay, wound healing assay, cell migration and invasion assays, RNA immunoprecipitation, and reporter vector construction and luciferase assays. Results: CRNDE was upregulated in hepatocellular carcinoma (HCC). The overexpression of CRNDE promoted HCC cellular proliferation, migration, and invasion in intro and in vivo, and acted as an oncogene in HCC progression. Furthermore, CRNDE impaired miR-136-5P expression in a RISC manner, and a reciprocal repression feedback loop was possible between CRNDE and miR-136-5P. We found that the neighboring mRNA of CRNDE was IRX5, and IRX5 increased the tumorigenicity of HCC cells. IRX5 was a potential downstream target gene of miR-136-5P. MiR-136 regulated IRX5 by interacting with its 3'UTR. In addition, miR-136-5P was involved in the CRNDE-regulated expression of IRX5. Conclusion: CRNDE acted as a tumor oncogene by exhibiting oncogenic properties of human HCC and revealed a novel CRNDE-miR-136-5P-IRX5 regulatory network in HCC. CRNDE may be considered to be a potential target for HCC therapies based on its ability to upregulate IRX5, and it deserves further investigation. [ABSTRACT FROM AUTHOR]

To systematically unveil transcription factors (TFs) that are critical to lung carcinogenesis, here we conducted a genome-wide lethality screening in non-small cell lung cancer (NSCLC) cells and reported that among the 1530 TFs tested, 21 genes were required for NSCLC cell proliferation and were negatively or positively associated with overall survival (OS) of patients with NSCLC. These included 11 potential tumor suppressing genes (AFF3, AhR, AR, CBFA2T3, CHD4, KANK2, NR3C2, PTEN, PRDM16, RB1, and STK11) and 10 potential oncogenic TFs (BARX1, DLX6, ELF3, EN1, ETV1, FOXE1, HOXB7, IRX4, IRX5, and SALL1). The expression levels of IRX5 were positively associated with OS of smoker and inversely associated with OS of non-smoker patients with lung adenocarcinoma. We showed that tobacco carcinogen benzo(a)pyrene (BaP) induced upregulation of IRX5 in lung epithelial cells, and Cyclin D1 was a downstream target of IRX5. Furthermore, silencing of IRX5 by lentivirus mediated transfection of short hairpin RNA significantly inhibited tumor growth in nude mice. These results indicate that tobacco smoke can modulate TFs to facilitate lung carcinogenesis, and inhibition of IRX5 may have therapeutic potentials in NSCLCs. [ABSTRACT FROM AUTHOR]

The Iroquois homeobox (Irx5) gene is essential in embryonic development and cardiac electrophysiology. Although recent studies have reported that IRX5 protein is involved in regulation of the cell cycle and apoptosis in prostate cancer cells, little is known about the role of IRX5 in the adult vasculature. Here we report novel observations on the role of IRX5 in adult vascular smooth muscle cells (VSMCs) during proliferation in vitro and in vivo. Comparative studies using primary human endothelial cells, VSMCs, and intact carotid arteries to determine relative expression of Irx5 in the peripheral vasculature demonstrate significantly higher expression in VSMCs. Sprague-Dawley rat carotid arteries were subjected to balloon catherization, and the presence of IRX5 was examined by immunohistochemistry after 2 wk. Results indicate markedly elevated IRX5 signal at 14 days compared with uninjured controls. Total RNA was isolated from injured and uninjured arteries, and Irx5 expression was measured by RT-PCR. Results demonstrate a significant increase in Irx5 expression at 3-14 days postinjury compared with controls. Irx5 genetic gain- and loss-of-function studies using thymidine and 5-bromo-2'-deoxyuridine incorporation assays resulted in modulation of DNA synthesis in primary rat aortic VSMCs. Quantitative RT-PCR results revealed modulation of cyclin-dependent kinase inhibitor 1B (p27kip1), E2F transcription factor 1 (E2f1), and proliferating cell nuclear antigen (Pcna) expression in Irx5-transduced VSMCs compared with controls. Subsequently, apoptosis was observed and confirmed by morphological observation, caspase-3 cleavage, and enzymatic activation compared with control conditions. Taken together, these results indicate that Irx5 plays an important role in VSMC G1/S-phase cell cycle check-point control and apoptosis. [ABSTRACT FROM AUTHOR]

Background: The long noncoding RNA (lncRNA) colorectal neoplasia differentially expressed - h (CRNDE-h) plays important roles in the early stages of human development and cancer progression. We investigated the expression and clinical significance of lncRNA CRNDE-h in colorectal cancer (CRC). Methods: The expression level of lncRNA CRNDE-h was analyzed in 142 CRC tissues and 142 paired adjacent nontumorous tissues, along with 21 inflammatory bowel diseases, 69 hyperplastic polyp, and 73 colorectal adenoma samples, using quantitative real-time polymerase chain reaction. The association between lncRNA CRNDE-h, and Iroquois homeobox protein 5 (IRX5) mRNA was examined in the same 142 CRC tissues. Results: We found that lncRNA CRNDE-h level was elevated in the CRC and adenoma groups compared with the other groups (all at P<0.001). In CRC, upregulation of lncRNA CRNDE-h was significantly correlated with large tumor size, positive regional lymph node metastasis, and distant metastasis (all at P<0.05). Area under the curve for lncRNA CRNDE-h showed diagnostic capability for distinguishing CRC from other groups. Patients with CRC with high lncRNA CRNDE-h expression level had poorer overall survival than those with low lncRNA CRNDE-h expression (log-rank test, P<0.001). Further, multivariable Cox regression analysis suggested that increased expression of lncRNA CRNDE-h was an independent prognostic indicator for CRC (hazard ratio [HR]=2.173; 95% confidence interval [CI], 1.282-3.684, P=0.004). Furthermore, lncRNA CRNDE-h expression was positively correlated with IRX5 mRNA in CRC tissues. Conclusions: Our data offers convincing evidence for the first time that lncRNA CRNDE-h is associated with adverse clinical characteristics and poor prognosis, which suggests that it might play an important role in CRC development and progression and might have clinical potential as a useful prognostic predictor. [ABSTRACT FROM AUTHOR]

Previous studies have established that transmural gradients of the fast transient outward K + current ( I to,f ) correlate with regional differences in action potential (AP) profile and excitation-contraction coupling (ECC) with high I to,f (Irx5-KO) or lacking I to,f 4.2-KO) or both. Irx5-KO mice exhibited decreased global LV contractility in association with elevated Irx5 (Irx5-KO) or lacking Kcnd2 (K V 4.2-KO) or both. Irx5-KO mice exhibited decreased global LV contractility in association with elevated I to,f , as well as reduced cell shortening and Ca 2+ transient amplitudes in cardiomyocytes isolated from the endomyocardium (ENDO) but not in cardiomyocytes from the EPI. Transcriptional profiling revealed that the primary effect of Irx5 ablation on ECC-related genes was to increase I to,f gene expression (i.e., Kcnd2 and Kcnip2 ) in the ENDO, but not the EPI. By contrast, K V 4.2-KO mice showed selective increases in cell shortening and Ca 2+ transients in isolated EPI cardiomyocytes, leading to enhanced ventricular contractility and mice lacking both Irx5 and Kcnd2 displayed elevated ventricular contractility, comparable to K V Irx5 is a vital transcription factor that establishes the transmural heterogeneity of ventricular myocyte contractility, thereby ensuring proper contractile function in the healthy heart. Regional differences in excitation-contraction coupling in the ventricular myocardium are primarily mediated through the inverse relationship between Irx5 and the fast transient outward K Irx5 -dependent modulation of I to,f in the regulation of contractility. Our findings show that the transmural electromechanical heterogeneities in the healthy ventricles depend on the Irx5 -dependent I to,f gradients. These observations provide a useful framework for assessing the molecular mechanisms underlying the alterations in contractile heterogeneity seen in the diseased heart. NEW & NOTEWORTHY Irx5 is a vital transcription factor that establishes the transmural heterogeneity of ventricular myocyte contractility, thereby ensuring proper contractile function in the healthy heart. Regional differences in excitation-contraction coupling in the ventricular myocardium are primarily mediated through the inverse relationship between Irx5 and the fast transient outward K + current ( I to,f ) across the ventricular wall.

The author discusses functional circuitry of fat mass and obesity associated gene (FTO) locus and adipocyte browning in humans.

We report on 2 cousins, a girl and a boy, born to first-cousin Lebanese parents with Hamamy syndrome, exhibiting developmental delay, intellectual disability, severe telecanthus, abnormal ears, dentinogenesis imperfecta, and bone fragility. Whole-exome sequencing studies performed on the 2 affected individuals and one obligate carrier revealed the presence of a homozygous c.503G>A (p.Arg168His) missense mutation in IRX5 in both sibs, not reported in any other family. Review of the literature and differential diagnoses are discussed., Competing Interests: The authors have no conflicts of interest to report., (Copyright © 2021 by S. Karger AG, Basel.)

Aims: Several inherited arrhythmic diseases have been linked to single gene mutations in cardiac ion channels and interacting proteins. However, the mechanisms underlying most arrhythmias, are thought to involve altered regulation of the expression of multiple effectors. In this study, we aimed to examine the role of a transcription factor (TF) belonging to the Iroquois homeobox family, IRX5, in cardiac electrical function., Methods and Results: Using human cardiac tissues, transcriptomic correlative analyses between IRX5 and genes involved in cardiac electrical activity showed that in human ventricular compartment, IRX5 expression strongly correlated to the expression of major actors of cardiac conduction, including the sodium channel, Nav1.5, and Connexin 40 (Cx40). We then generated human-induced pluripotent stem cells (hiPSCs) derived from two Hamamy syndrome-affected patients carrying distinct homozygous loss-of-function mutations in IRX5 gene. Cardiomyocytes derived from these hiPSCs showed impaired cardiac gene expression programme, including misregulation in the control of Nav1.5 and Cx40 expression. In accordance with the prolonged QRS interval observed in Hamamy syndrome patients, a slower ventricular action potential depolarization due to sodium current reduction was observed on electrophysiological analyses performed on patient-derived cardiomyocytes, confirming the functional role of IRX5 in electrical conduction. Finally, a cardiac TF complex was newly identified, composed by IRX5 and GATA4, in which IRX5 potentiated GATA4-induction of SCN5A expression., Conclusion: Altogether, this work unveils a key role for IRX5 in the regulation of human ventricular depolarization and cardiac electrical conduction, providing therefore new insights into our understanding of cardiac diseases., (Published on behalf of the European Society of Cardiology. All rights reserved. © The Author(s) 2020. For permissions, please email: journals.permissions@oup.com.)

The Iroquois homeobox gene 5 (IRX5), one of the members of the Iroquois homeobox family, has been identified to correlate with worse prognosis in many cancers, including colorectal cancer (CRC). In this study, upregulation of IRX5 revealed a great reduction in the proliferation of CRC colorectal cancer cell line SW480 and DLD-1, which was accompanied by G1/S arrest, increased expression in cyclin E1, P21, and P53 and a decrease in cyclin A2, B1, and D1. Furthermore, IRX5-mediated an increase expression of RH2A protein, the biomarker of DNA damage. Consequently, the SA-β-gal level is higher in IRX5-overexpression cells compared to control ones, which showed elevated DNA damage triggered cellular senescence. Recapitulating the above findings, IRX5 exhibited higher levels of genomic instability. IRX5 may be a perspective target for cancer therapy and it deserves further investigation., (© 2020 Wiley Periodicals, Inc.)

Healthy development of ovarian follicles depends on appropriate interactions and function between oocytes and their surrounding granulosa cells. Previously, we showed that double knockout of Irx3 and Irx5 (Irx3/5 DKO) in mice resulted in abnormal follicle morphology and follicle death. Further, female mouse models of individual Irx3 or Irx5 knockouts were both subfertile but with distinct defects. Notably, the expression profile of each gene suggests independent roles for each; first, they are colocalized in pre-granulosa cells during development that then progresses to include oocyte expression during germline nest breakdown and primordial follicle formation. Thereafter, their expression patterns diverge between oocytes and granulosa cells coinciding with the formulation and maturation of intimate oocyte-granulosa cell interactions. The objective of this study was to investigate the contributions of Irx5 and somatic cell-specific expression of Irx3 during ovarian development. Our results show that Irx3 and Irx5 contribute to female fertility through different mechanisms and that Irx3 expression in somatic cells is important for oocyte quality and survival. Based on evaluation of a series of genetically modified mouse models, we conclude that IRX3 and IRX5 collaborate in the same cells and then in neighboring cells to foster a healthy and responsive follicle. Long after these two factors have extinguished, their legacy enables these intercellular connections to mature and respond to extracellular signals to promote follicle maturation and ovulation., (© The Author(s) 2020. Published by Oxford University Press on behalf of Society for the Study of Reproduction. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Colorectal cancer (CRC) is one of the most common malignant tumors worldwide. As tumor metastasis is the leading cause of death in patients with CRC, it is important to elucidate the molecular mechanisms that drive CRC metastasis. Studies have shown a close relationship between Iroquois homeobox (IRX) family genes and multiple cancers, while the mechanism by which IRX5 promotes CRC metastasis is unclear. Therefore, we focused on the involvement of IRX5 in CRC metastasis. In this study, analyses of clinical data indicated that the expression of IRX5 was coincided with metastatic colorectal tumors tissues and was negatively correlated with the overall survival of patients with CRC. Functional analysis showed that IRX5 promoted the migration and invasion of CRC cells, accompanied by a large number of cellular protrusions. IRX5-overexpressing cells were more likely to form metastatic tumors in nude mice. Further analysis demonstrated that the core components of the RHOA/ROCK1/LIMK1 pathway were significantly inhibited in IRX5-overexpressing cells. Overexpression of LIMK1 effectively reversed the enhanced cellular motility caused by IRX5 overexpression. Moreover, we found that high levels of IRX5 in intestinal tissues were correlated with the inflammatory response. IRX5 was significantly increased in azoxymethane/dextran sodium sulfate intestinal tissue of mice and IRX5-overexpressing may also enhance chemokines CXCL1 and CXCL8. In summary, our findings suggested that IRX5 promoted CRC metastasis by inhibiting the RHOA-ROCK1-LIMK1 axis, which correlates with a poor prognosis., (© 2019 Wiley Periodicals, Inc.)

The Iroquois homeobox (Irx5) gene is essential in embryonic development and cardiac electrophysiology. Although recent studies have reported that IRX5 protein is involved in regulation of the cell cycle and apoptosis in prostate cancer cells, little is known about the role of IRX5 in the adult vasculature. Here we report novel observations on the role of IRX5 in adult vascular smooth muscle cells (VSMCs) during proliferation in vitro and in vivo. Comparative studies using primary human endothelial cells, VSMCs, and intact carotid arteries to determine relative expression of Irx5 in the peripheral vasculature demonstrate significantly higher expression in VSMCs. Sprague-Dawley rat carotid arteries were subjected to balloon catherization, and the presence of IRX5 was examined by immunohistochemistry after 2 wk. Results indicate markedly elevated IRX5 signal at 14 days compared with uninjured controls. Total RNA was isolated from injured and uninjured arteries, and Irx5 expression was measured by RT-PCR. Results demonstrate a significant increase in Irx5 expression at 3-14 days postinjury compared with controls. Irx5 genetic gain- and loss-of-function studies using thymidine and 5-bromo-2'-deoxyuridine incorporation assays resulted in modulation of DNA synthesis in primary rat aortic VSMCs. Quantitative RT-PCR results revealed modulation of cyclin-dependent kinase inhibitor 1B (p27(kip1)), E2F transcription factor 1 (E2f1), and proliferating cell nuclear antigen (Pcna) expression in Irx5-transduced VSMCs compared with controls. Subsequently, apoptosis was observed and confirmed by morphological observation, caspase-3 cleavage, and enzymatic activation compared with control conditions. Taken together, these results indicate that Irx5 plays an important role in VSMC G1/S-phase cell cycle checkpoint control and apoptosis., (Copyright © 2016 the American Physiological Society.)