ABSTRACT
Objective To analyze the resenilin-1 (PS-1) gene mutations in Alzheimer' s disease (AD) patients and investigate the influence of the initiation codon mutation on the mRNA expression of PS-1 and amyloid precursor protein (APP) genes and the expression of PS-1 proteins.Methods (1) All 111 AD patients were enrolled by the Department of Neurology,Second Affiliated Hospital,College of Medicine,Zhejiang University from July 2004 to June 2010.Mutations in the 13 exons and flanking regions of PS-1 gene were examined by direct sequencing.(2) cDNAs encoding full-length wild-type and mutant (c.1A ＞G) PS-1 were subcloned into enhanced green fluorescent protein.Levels of the mRNA expression of PS-1 and APP genes and PS-1 proteins expression in the transfected cells were detected by quantitative real-time PCR and Western blot,respectively.Results A new heterozygous initiation codon mutation changing from ATG to GTG in one individual was identified.Compared to the control groups,the mRNA expression of the mutant PS-1 gene in HEK293 and N2a was significantly lower than the normal PS-1 gene(116.8 ± 3.9 vs 49.5 ±3.3,t =13.27,P ＜0.01 ;69.0 ± 1.9 vs 29.5 ± 1.3,t =17.20,P ＜0.01) and the APP gene was not obviously altered.The proteins were detected by Western blot analysis in HEK293 cells but not in N2a cells.Conclusions Since we only identified one novel heterozygous initiation codon mutation (from ATG to GTG),mutations in PS-1 are likely to be rare in AD patients.Initiation codon mutation would reduce the expression of PS-1 proteins.Inactivation of some of the PS-1 proteins could be insufficient to lead to AD and could be more likelv to act as a risk factor.
ABSTRACT
Objective To study the role of deleted in liver cancer-1 (DLC-1) gene main domains on the regulation of human colon cancer HT29 cell proliferation.Methods Subcloning recombinant plasmid vectors with Rho GTPase activating protein (RhoGAP),sterile alpha motif (SAM) or steroidogenic acute regulatory-related lipid-transfer (START) domains of DLC-1 gene knockout were constructed and transfected into human colon cancer cell HT29.Wild HT29 cell group (control group),pcDNA3.1-HT29 cell group (vector group) and pcDNA3.1-HT29-DLC-1 cell group (whole DLC-1 gene transfected group) were set as control.The change of cell proliferation was detected by methylthiazolyldiphenyl-tetrazolium bromide (MTT) assay and colony formation test.The cell apoptosis was analyzed by flow cytometry.The activity of RhoA protein was detected by pull-down assay.The differences between the groups were analyzed by the analysis of variance.Results At 48 hours after the successful transfection,compared with control group and vector group,cells proliferation and the activity of RhoA protein were significantly suppressed in whole DLC-1 gene transfected group (F=146.36,698.08,both P＜0.05) and early cell apoptosis increased (F=294.08,P＜0.05).Compared with control group and vector group,there was no significant difference in cell proliferation ability,cell apoptosis and the activity of RhoA protein activity in RhoGAP knockout transfected cells (F=0.99,0.049,5.769,all P＞0.05).Compared with whole DLC-1 gene transfected group,the suppression of cell proliferation was more significant in SAM knockout transfected cells (F=31.00,P＜0.05),the activity of RhoA protein down regulated (F=92.57,P＜0.05) and apoptosis increased (F=130.44,P＜0.05).Compared with whole DLC-1 gene transfected group,the ability of cell proliferation increased (F=15.47,P＜0.05),apoptosis cell decreased (F＝110.23,P＜0.05) and the activity of RhoA protein up regulated (F=199.39,P＜0.05) in START knockout transfected cells.Conclusions The role of DLC-1 gene in the suppression of cell proliferation in HT29 cells was RhoGAP-dependent.SAM domain may be the self suppression domain for endogenous RhoGAP activity.START domain may take effect through enhancing RhoGAP domain.