The radial migration of cortical pyramidal neurons (PNs) during corticogenesis is necessary for establishing a multilayered cerebral cortex. Neuronal migration defects are considered a critical etiology of neurodevelopmental disorders, including autism spectrum disorders (ASDs), schizophrenia, epilepsy, and intellectual disability (ID). TRIO is a high-risk candidate gene for ASDs and ID. However, its role in embryonic radial migration and the etiology of ASDs and ID are not fully understood. In this study, we found that the in vivo conditional knockout or in utero knockout of Trio in excitatory precursors in the neocortex caused aberrant polarity and halted the migration of late-born PNs. Further investigation of the underlying mechanism revealed that the interaction of the Trio N-terminal SH3 domain with Myosin X mediated the adherence of migrating neurons to radial glial fibers through regulating the membrane location of neuronal cadherin (N-cadherin). Also, independent or synergistic overexpression of RAC1 and RHOA showed different phenotypic recoveries of the abnormal neuronal migration by affecting the morphological transition and/or the glial fiber-dependent locomotion. Taken together, our findings clarify a novel mechanism of Trio in regulating N-cadherin cell surface expression via the interaction of Myosin X with its N-terminal SH3 domain. These results suggest the vital roles of the guanine nucleotide exchange factor 1 (GEF1) and GEF2 domains in regulating radial migration by activating their Rho GTPase effectors in both distinct and cooperative manners, which might be associated with the abnormal phenotypes in neurodevelopmental disorders.
Autism Spectrum Disorder/metabolism* ; Cell Movement/genetics* ; Humans ; Interneurons/metabolism* ; Neurodevelopmental Disorders/genetics* ; Neurons/metabolism* ; Rho Guanine Nucleotide Exchange Factors/genetics*

Breast Neoplasms ; metabolism ; pathology ; Cell Line, Tumor ; Cell Proliferation ; drug effects ; Down-Regulation ; drug effects ; Female ; Guanine Nucleotide Exchange Factors ; antagonists & inhibitors ; genetics ; metabolism ; Humans ; Indoles ; pharmacology ; MCF-7 Cells ; Maleimides ; pharmacology ; Protein Isoforms ; genetics ; metabolism ; Protein Kinase C ; antagonists & inhibitors ; genetics ; metabolism ; RNA Interference ; RNA, Small Interfering ; metabolism ; Receptor, ErbB-2 ; genetics ; metabolism ; Tetradecanoylphorbol Acetate ; toxicity

OBJECTIVE: To investigate the effect of T lymphoma invasion and metastasis 1 (Tiam 1) overexpression in head and neck squamous cell carcinoma (HNSCC) cells. METHOD: Endogenous expression of Tiam 1 in 8 head and neck squamous cell carcinoma cell (HNSCC) lines was investigated by real-time RT-PCR. A lentivirus vector containing Tiaml was transfected into UM-SCC-47 cells, a head and neck squamous cell carcinoma cell line with little endogenous Tiaml expression. Stable clone, obtained by G418 screening, were assayed by RT-PCR and Western blot to validate the gene expression efficiency. The biological behaviors of the transduced cells were determined by cell counting, MTT and in-vitro migration assay. RESULT: Tiam 1 gene was highly expressed in M2 cell line and it's low level expression was found in UM-SCC-47. Cell counting and MTT assay showed that over-expression of Tiaml significantly promoted cell proliferation (P < 0.05). The cell monolayers overexpressed Tiaml that resulted in a significant increasment of cell migration in infected head and neck squamous cell carcinoma cell lines (P < 0.05). CONCLUSION Tiam 1 gene plays an important role in the growth and migration in head and neck squamous cell carcinoma cell lines. It may be a useful marker for metastasis of head and neck squamous cell carcinoma.
Blotting, Western ; Carcinoma, Squamous Cell ; metabolism ; pathology ; Cell Line, Tumor ; Cell Movement ; Cell Proliferation ; Guanine Nucleotide Exchange Factors ; genetics ; metabolism ; Head and Neck Neoplasms ; metabolism ; pathology ; Humans ; Squamous Cell Carcinoma of Head and Neck ; T-Lymphoma Invasion and Metastasis-inducing Protein 1 ; Transfection

OBJECTIVETo explore the effect of downregulation of Tiam1 by siRNA on the esophageal squamous cell carcinoma (ESCC) EC9706 cells, and provide theoretical basis for gene therapy of ESCC using Tiam1 as a molecular target.

METHODSTiam1 siRNA was transfected into EC9706 cells, and expression changes of Tiam1 mRNA and protein after transfection were detected by quantitative real-time PCR and Western blotting. Cell proliferation was analyzed using CCK-8 kit. Cell cycle and apoptosis of the EC9706 cells were assessed by flow cytometry. Cell cycle-related proteins and cell apoptosis-associated proteins were analyzed by Western blotting.

RESULTSCompared with the untreated group and control siRNA group, the relative expression levels of Tiam1 mRNA (1.00 and 0.11 ± 0.02) were not significantly different (P > 0.05). The relative expression levels of Tiam1 mRNA in the Tiam1 siRNA group at 24, 48 and 72 h after transfection were 0.30 ± 0.04, 0.09 ± 0.01 and 0.09 ± 0.006, respectively, significantly lower than that of the untreated group (P < 0.05 for all). The expression level of Tiam1 protein at 24 h after Tiam1 siRNA transfection in the EC9706 cells was 0.11 ± 0.02, significantly lower than that in the un-treated group (0.44 ± 0.05) and control siRNA group (0.44 ± 0.04, P < 0.05 for all). The percentages of G0/G1 cells in the Tiam1 siRNA group, untreated group and control siRNA group were (54.48 ± 2.14)%, (40.69 ± 1.85)% and (41.78 ± 1.31)%, respectively (P < 0.01). The percentages of S phase cells in the Tiam1 siRNA group, untreated group and control siRNA group were (27.18 ± 1.65)%, (32.32 ± 1.15)% and (30.35 ± 1.09)%, respectively (P < 0.01). The expression levels of cyclin D1 protein in the untreated group, control siRNA group and Tiam1 siRNA group were 0.43 ± 0.02, 0.41 ± 0.01 and 0.11 ± 0.02, respectively (P < 0.05). The expression levels of p27 protein in the untreated group, control siRNA group and Tiam1 siRNA group were 0.10 ± 0.01, 0.09 ± 0.02 and 0.20 ± 0.02, respectively (P < 0.05). The ratios of early apoptotic cells in the untreated group, control siRNA group and Tiam1 siRNA group were (10 ± 0.9)%, (10 ± 0.5)% and (27 ± 0.7)%, respectively (P < 0.01). The expression levels of Mcl-1 protein in EC9706 cells of untreated group, control siRNA group and Tiam1 siRNA group were 0.47 ± 0.12, 0.48 ± 0.13 and 0.16 ± 0.02, respectively (P < 0.05). The expression levels of Bcl-2 protein in EC9706 cells of the untreated group, control siRNA group and Tiam1 siRNA group were 0.49 ± 0.08, 0.50 ± 0.05 and 0.04 ± 0.03, respectively (P < 0.05). The caspase-3 activities in the untreated group, control siRNA group and Tiam1 siRNA group were 2.3 ± 0.09, 2.3 ± 0.10 and 16.0 ± 1.50, respectively; and that of caspase-9 were 2.3 ± 0.08, 2.3 ± 0.11 and 14.5 ± 0.9, respectively (P < 0.05 for all).

CONCLUSIONSTiam1 siRNA can significantly inhibit the proliferation of esophageal cancer EC9706 cells, induce cell cycle arrest and cell apoptosis. These effects are related to the regulation of the expressions of cell cycle-related genes (cyclin D1 and p27) and cell apoptosis-related genes (Mcl-1, Bcl-1, caspase-3 and caspase-9) by Tiam1 siRNA.

Apoptosis ; Carcinoma, Squamous Cell ; genetics ; metabolism ; pathology ; Caspase 3 ; metabolism ; Caspase 9 ; metabolism ; Cell Cycle Checkpoints ; Cell Line, Tumor ; Cell Proliferation ; Cyclin D1 ; metabolism ; Cyclin-Dependent Kinase Inhibitor p27 ; metabolism ; Down-Regulation ; Esophageal Neoplasms ; genetics ; metabolism ; pathology ; Guanine Nucleotide Exchange Factors ; genetics ; metabolism ; Humans ; Myeloid Cell Leukemia Sequence 1 Protein ; metabolism ; Proto-Oncogene Proteins c-bcl-2 ; metabolism ; RNA Interference ; RNA, Messenger ; metabolism ; RNA, Small Interfering ; genetics ; T-Lymphoma Invasion and Metastasis-inducing Protein 1 ; Transfection

BACKGROUNDT-lymphoma and metastasis gene 1 (Tiam1) produces a guanine nucleotide exchange factor (GNEF) that regulates guanosine triphosphatase, which transforms guanosine diphosphate to guanosine triphosphate. Recently published data indicate that Tiam1 was associated with gastric cancer. The aim of this study was to investigate biological effects and potential mechanisms of Tiam1 in gastric carcinoma.

METHODSWe analyzed the expression of Tiam1 in 114 pair-matched gastric neoplastic and adjacent non-neoplastic tissues by quantitative real-time PCR. We investigated Tiam1 expression and its prognostic value for gastric cancer. Furthermore, the functions of Tiam1 over-expression were analyzed with stable-expression Tiam1 plasmid in human gastric cancer cell lines.

RESULTSTiam1 expression was significantly associated with cell differentiation and lymphatic metastasis; expression of Tiam1 mRNA was up-regulated in gastric cancer compared to pair-matched adjacent non-tumor tissues. Analyses of surgical tissue samples and 5-year survival of gastric cancer patients showed that those with strong Tiam1 expression had significantly shorter overall survival time than those with negative Tiam1 expression. Ectopic expression of Tiam1 promoted cell growth, migration and invasion of gastric cancer cells in vitro.

CONCLUSIONSIn gastric cancer cells, Tiam1 affects multiple properties associated with acquisition of the metastatic phenotype, and may be a marker of gastric cancer progression and metastasis in a subset of cancer.

Cell Line, Tumor ; Cell Movement ; genetics ; physiology ; Cell Proliferation ; Guanine Nucleotide Exchange Factors ; genetics ; metabolism ; Humans ; Neoplasm Metastasis ; genetics ; Stomach Neoplasms ; genetics ; metabolism ; pathology ; T-Lymphoma Invasion and Metastasis-inducing Protein 1

OBJECTIVETo investigate the significance of Tiam1 in invasion and metastasis of breast carcinoma and its mechanisms.

METHODSImmunohistochemistry was used to detect Tiam1 expression in tumor tissue of 126 breast carcinomas. Tiam1 was silenced by siRNA in breast carcinoma cell line MDA-MB-435, then the expressions of phosphor-ERK 1, ERK 2 and VEGF were detected, and electrophoretic mobility shift assay (EMSA) was used to examine the transcription activiy of AP-1.

RESULTSThere was a significant relationship between Tiam1 expression and lymph node metastasis (P < 0.05). Furthermore, after silencing of Tiam1, the expressions of phosphor-ERK 1, ERK 2 and VEGF were decreased, and the transcription activity of AP-1 was down-regulated in the MDA-MB-435 cells.

CONCLUSIONTiam1 is closely related with invasion and metastasis of breast carcinoma, and the cascade Tiam1 through ERK, AP-1 and VEGF pathways may play an important role in enhancing angiogenesis, therefore, to promote invasion and metastasis of breast carcinoma.

Breast Neoplasms ; metabolism ; pathology ; Cell Line, Tumor ; Female ; Gene Expression Regulation, Neoplastic ; Gene Silencing ; Guanine Nucleotide Exchange Factors ; genetics ; metabolism ; Humans ; Lymphatic Metastasis ; Mitogen-Activated Protein Kinase 1 ; metabolism ; Mitogen-Activated Protein Kinase 3 ; metabolism ; Neoplasm Invasiveness ; RNA, Messenger ; metabolism ; RNA, Small Interfering ; genetics ; Signal Transduction ; T-Lymphoma Invasion and Metastasis-inducing Protein 1 ; Transcription Factor AP-1 ; metabolism ; Vascular Endothelial Growth Factor A ; metabolism

Previously, we demonstrated that the p190 Rho guanine nucleotide exchange factor (p190RhoGEF) was induced following CD40 stimulation of B cells. In this study, we examined whether p190RhoGEF and a downstream effector molecule RhoA are required for B cell differentiation. Expression of p190RhoGEF positively correlated with the expression of surface markers and transcriptional regulators that are characteristic of mature B cells with plasma cell (PC) phenotypes. Moreover, either the overexpression of p190RhoGEF or the expression of a constitutively active RhoA drove cellular differentiation toward PC phenotypes. B cell maturation was abrogated in cells that overexpressed p190RhoGEF and a dominant-negative form of RhoA simultaneously. CD40-mediated maturation events were also abrogated in cells that overexpressed either dominant-negative p190RhoGEF or RhoA. Together, these data provide evidence that p190RhoGEF signaling through RhoA in CD40-activated B cells drives the induction of the PC differentiation.
Animals ; B-Lymphocytes/*cytology/*metabolism ; Cell Differentiation/genetics/*physiology ; Cell Line ; Cells, Cultured ; Female ; Guanine Nucleotide Exchange Factors/genetics/*metabolism ; Humans ; Lymphocyte Activation/genetics/*physiology ; Mice ; Mice, Inbred BALB C ; Plasma Cells/*cytology/*metabolism ; rhoA GTP-Binding Protein/genetics/metabolism

OBJECTIVETo observe the subcellular localization of Rac1 and the expression of Tiam1 and Rac1 in gastric carcinoma, in order to reveal the relationship between the distribution of Rac1 and progression of gastric carcinoma.

METHODSBoth carcinoma and adjacent normal tissue of 48 patients with gastric carcinoma were studied in this study. Tissue distribution and expression of Rac1 and Tiam1 were analyzed by immunohistochemistry and real-time polymerase chain reaction (PCR).

RESULTSCompared with that of adjacent non-cancerous gastric mucosa, the expression of Rac1 in cancer tissues was significantly increased. The positive rate of Rac1 expression was 18.8% (9/48 cases) in adjacent non-neoplastic gastric and 79.2% (38/48 cases) in cancer tissues. The positive staining was mainly located in the cell nuclei (31 samples). The real-time PCR results demonstrated that the expression levels of Tiam1 and Rac1 mRNA in cancerous tissues with nuclear localization of Rac1 were evidently increased. Furthermore, nuclear localization of Rac1 was associated with tumor stage and metastasis.

CONCLUSIONSThe majority of gastric cancer tissues show nuclear dislocalization of Rac1 expression, which may be a sign of abnormal activation of Tiam1-Rac1 pathway. It may suggest enhanced invasion ability of the gastric carcinoma.

Adult ; Aged ; Aged, 80 and over ; Cell Nucleus ; metabolism ; Disease Progression ; Female ; Guanine Nucleotide Exchange Factors ; genetics ; metabolism ; Humans ; Immunohistochemistry ; Lymphatic Metastasis ; Male ; Middle Aged ; Neoplasm Invasiveness ; Neoplasm Metastasis ; Neoplasm Staging ; Polymerase Chain Reaction ; RNA, Messenger ; metabolism ; Stomach Neoplasms ; metabolism ; pathology ; T-Lymphoma Invasion and Metastasis-inducing Protein 1 ; rac1 GTP-Binding Protein ; genetics ; metabolism

OBJECTIVETo investigate the expression of T lymphoma invasion and metastasis inducing factor 1 (Tiam1) in breast carcinomas, and explore its association with the clinicopathological features of breast carcinoma.

METHODSImmunohistochemistry was used to detect Tiam1 expression in normal breast tissue and 126 breast carcinoma tissues, and the expression levels of Tiam1 mRNA and protein were detected by reverse transcriptase polymerase chain reaction (RT-PCR) and Western blotting, respectively.

RESULTSThe expression of Tiam1 was significantly higher in breast carcinomas than in normal breast tissue (P<0.05). Tiam1 expression was not correlated to the age of the patients or the histological type (P>0.05), but to lymph node metastasis and clinical stages of the tumor (P<0.01). Tiam1 mRNA and protein expressions were stronger in breast carcinoma cell line MDA-MB-435 with high metastatic potential than in breast carcinoma cell line MCF-7.

CONCLUSIONTiam1 is closely related to the metastasis of breast carcinoma, and may play an important role in promoting metastasis of breast carcinoma.

Adult ; Aged ; Breast Neoplasms ; metabolism ; pathology ; Cell Line, Tumor ; Female ; Guanine Nucleotide Exchange Factors ; genetics ; metabolism ; Humans ; Lymphatic Metastasis ; Middle Aged ; RNA, Messenger ; genetics ; metabolism ; Reverse Transcriptase Polymerase Chain Reaction ; T-Lymphoma Invasion and Metastasis-inducing Protein 1

Adult ; Aged ; Aged, 80 and over ; Female ; Guanine Nucleotide Exchange Factors ; genetics ; metabolism ; Humans ; Keratin-18 ; genetics ; metabolism ; Lymph Nodes ; metabolism ; pathology ; Lymphatic Metastasis ; Male ; Middle Aged ; RNA, Messenger ; metabolism ; Stomach Neoplasms ; metabolism ; pathology ; T-Lymphoma Invasion and Metastasis-inducing Protein 1