Gene Associated With Alzheimer's Disease And Apoe-deficient Mice Brain Tissue, Abnormal Expression Of Mirna Identification And Preliminary Function Study

Folate is a cofactor in one-carbon metabolism,during which it promotes the remethylation of homocysteine.Recent epidemiological and experimental studies have linked folate deficiency and resultant increased homocysteine levels with Alzheimer's disease.Then,association between folate related genes polymorphisms and AD is a logic extension of the well-established connection between folate,homocysteine and AD.In this study,we tested single nucleotide polymorphisms in folate metabolism related genes for association with late onset AD(LOAD) by restriction fragment length polymorphism(RFLP) method.Polymorphisms in 5,10-methylenetetrahydrofolate reductase(MTHFR),the reduced folate carrier 1(RFC1),5,10-methylenetetrahydrofolate dehydrogenase(MTHFD1),cystathionine beta-synthase(CβS) and phosphatidyl-ethanolamine N-methyltransferase(PEMT) were examined in 386AD cases and 375 matched controls.Plasma levels of homocysteine,folate and cysteine were measured in 106 cases and 120 controls by microbiological assay and high-performance liquid chromatography(HPLC).Results showed that AD patients had significantly decreased plasma folate and cysteine concentrations,and increased plasma homocysteine levels.Significant associations of RFC1 80G allele and GG genotype with AD(p=0.008,OR=1.312,95%CI 1.072-1.605, and p=0.042,OR=1.383,95%CI 1.012-1.890) were found.Further stratification of total samples by APOEε4 status,age/age at onset and gender reveled that RFC1 80G allele was an APOEε4-independent risk factor for late-onset AD,and it might increase the risk of AD in females.No significant associations of MTHFR 677C/T allele and genotype with AD were observed in total samples,but significant associations of T allele and TT genotype with AD(p=0.031,OR=1.586,95%CI=1.042-2.414,and p=0.028,OR=2.250, 95%CI=1.074-4.712) were identified in APOEε4 carrier subgroup.No relationship between MTHFD1 1958G/A,CβS 844in68 and PEMT 523G/A polymorphisms with AD were found. For the total samples,the subjects with the RFC1 80 GG genotype exhibited lower plasma folate levels,and higher homocysteine levels than the subjects with GA plus AA genotype,but the difference was not statistically significant.The similar results were observed in the subgroups of AD and control samples.It seemed to suggest a trend of lower folate levels and higher homocysteine levels in the subjects with GG genotypes than that the subjects with the GA plus AA genotypes although the difference did not reach statistical significance.No significant differences for the plasma levels of folate and homocysteine between the genotypes of MTHFR 677C/T,CβS 844ins68 and MTHFD1 1958G/A were observed.Our findings suggest that genetic variant of RFC1 80A/G increases the risk of Alzheimer's disease,,suggesting that MTHFR 677T allele and APOEε4 allele may synergistically act to increase AD risk.The mechanism need further studied. A class of small,non-coding transcripts called microRNAs(miRNAs) that provide a crucial and pervasive layer of post-transcriptional gene regulation has recently emerged and become the focus of intense research,miRNAs are abundant in the nervous system, where they have key roles in development and are likely to be important mediators of plasticity.There are several evidence that miRNAs may play an important role in aging and neurodegeneration disease.Alzheimer's disease is one of the most prevalent dementia, and characterized with neuronal loss,extracellular senile plaques containing the peptideβamyloid,and neurofibrillary protein tau.Polymorphism in APOE is an risk factor of Alzheimer's disease,apoE-deficient mouse offer an opportunity to study some of the possible functions of apoE in the Alzheimer's disease.We examined the expression of 41 miRNAs in the frontal cortex and hippocampus of 7 months old apoE-deficient mouse and control mouse by multiplex qRT-PCR.The data showed that mmu-miR-7f2,mmu-miR-29a levels were decreased significantly in frontal cortex of apoE^-/- mouse,and mmu-miR-143 levels was decreased significantly both in the frontal cortex and hippocampus regions of apoE^-/- mouse.Then we analyzed the expression of miR-143 in 2 and 13 months old apoE^-/- and control mouse,found that miR-143 levels was increased with age both in frontal cortex and hippocampus in control mouse.In the frontal cortex of apoE^-/- mouse,miR-143 levels was a little higher than that in the control mouse at the second month,and it increased with age too,but failed to paralle to the control mouse when 7 and 13 months old.In the hippocampus of apoE^-/- mouse,the expression of miR-143 was not defferent with control mouse significantly at 2 months old, there was a increase at the 7th month,but in the 13months old mouse,the miR-143 level decreased to a lower levels than 2 months old,and lower than control mouse too.The 3'-untranslated region(UTR) of ERK5,CREBZF,CREB5,DYRK1B and TAOK1 were presumed to be targeted by miR-143 through computational analysis.The luciferase reporter assay suggested that the ERK5,CREBZF and TAOK1 were the target gene of miR-143.The function of the three genes suggest that miR-143 may change the MAPKK-MAPK-ERK pathway and long-term synaptic changes and memory formation, which need further confirmation.