The amyloid precursor protein (APP) and its proteolytic product amyloid beta (Aβ) are associated with both familial and sporadic forms of Alzheimer disease (AD). Aberrant expression and function of microRNAs has been observed in AD. Here, we show that in rat hippocampal neurons cultured in vitro, the down-regulation of Argonaute-2, a key component of the RNA-induced silencing complex, produced an increase in APP levels. Using site-directed mutagenesis, a microRNA responsive element (RE) for miR-101 was identified in the 3′-untranslated region (UTR) of APP. The inhibition of endogenous miR-101 increased APP levels, whereas lentiviral-mediated miR-101 overexpression significantly reduced APP and Aβ load in hippocampal neurons. In addition, miR-101 contributed to the regulation of APP in response to the proinflammatory cytokine interleukin-1β (IL-lβ). Thus, miR-101 is a negative regulator of APP expression and affects the accumulation of Aβ, suggesting a possible role for miR-101 in neuropathological conditions. The amyloid precursor protein (APP) and its proteolytic product amyloid beta (Aβ) are associated with both familial and sporadic forms of Alzheimer disease (AD). Aberrant expression and function of microRNAs has been observed in AD. Here, we show that in rat hippocampal neurons cultured in vitro, the down-regulation of Argonaute-2, a key component of the RNA-induced silencing complex, produced an increase in APP levels. Using site-directed mutagenesis, a microRNA responsive element (RE) for miR-101 was identified in the 3′-untranslated region (UTR) of APP. The inhibition of endogenous miR-101 increased APP levels, whereas lentiviral-mediated miR-101 overexpression significantly reduced APP and Aβ load in hippocampal neurons. In addition, miR-101 contributed to the regulation of APP in response to the proinflammatory cytokine interleukin-1β (IL-lβ). Thus, miR-101 is a negative regulator of APP expression and affects the accumulation of Aβ, suggesting a possible role for miR-101 in neuropathological conditions. IntroductionAlzheimer disease (AD) 2The abbreviations used are: ADAlzheimer diseaseAPPamyloid precursor proteinAβamyloid βRISCRNA-induced silencing complexREsresponsive elementsUTRuntranslated regionIL-1βinterleukin-1βEGFPenhanced green fluorescent proteinCox-2cyclooxygenasesAPPsoluble N-terminal fragmentPGE2prostaglandin E2TricineN-[2-hydroxy-1,1-bis(hydroxymethyl)ethyl]glycineAgo2Argonaute-2DIVdays in vitroGAPDHglyceraldehyde-3-phosphate dehydrogenaseTBPTATA-binding protein. is the most common form of dementia in aged individuals and is characterized by Aβ plaques, which contain Aβ aggregates and neurofibrillary tangles which consist primarily of aggregated forms of the microtubule-stabilizing protein tau (reviewed in Ref. 1Haass C. Selkoe D.J. Nat. Rev. Mol. Cell Biol. 2007; 8: 101-112Crossref PubMed Scopus (3811) Google Scholar). Aβ peptides are derived from processing of the type I transmembrane protein APP through sequential cleavages by β and γ secretase (2Yan R. Bienkowski M.J. Shuck M.E. Miao H. Tory M.C. Pauley A.M. Brashier J.R. Stratman N.C. Mathews W.R. Buhl A.E. Carter D.B. Tomasselli A.G. Parodi L.A. Heinrikson R.L. Gurney M.E. Nature. 1999; 402: 533-537Crossref PubMed Scopus (1328) Google Scholar, 3Wolfe M.S. Xia W. Ostaszewski B.L. Diehl T.S. Kimberly W.T. Selkoe D.J. Nature. 1999; 398: 513-517Crossref PubMed Scopus (1676) Google Scholar). The Aβ load during pathology leads to neurological dysfunction. APP is linked to AD; familial AD can be caused by increased expression of APP due to either genomic duplication (4Podlisny M.B. Lee G. Selkoe D.J. Science. 1987; 238: 669-671Crossref PubMed Scopus (117) Google Scholar, 5Rovelet-Lecrux A. Hannequin D. Raux G. Le Meur N. Laquerrière A. Vital A. Dumanchin C. Feuillette S. Brice A. Vercelletto M. Dubas F. Frebourg T. Campion D. Nat. Genet. 2006; 38: 24-26Crossref PubMed Scopus (959) Google Scholar) or regulatory sequence alterations (6Theuns J. Brouwers N. Engelborghs S. Sleegers K. Bogaerts V. Corsmit E. De Pooter T. van Duijn C.M. De Deyn P.P. Van Broeckhoven C. Am. J. Hum. Genet. 2006; 78: 936-946Abstract Full Text Full Text PDF PubMed Scopus (156) Google Scholar). Among the physiological and pathological activators of APP expression (7Mobley W.C. Neve R.L. Prusiner S.B. McKinley M.P. Proc. Natl. Acad. Sci. U.S.A. 1988; 85: 9811-9815Crossref PubMed Scopus (225) Google Scholar, 8Dewji N.N. Do C. Brain Res. Mol. Brain Res. 1996; 35: 325-328Crossref PubMed Scopus (40) Google Scholar) is the proinflammatory cytokine IL-1β (9Rogers J.T. Leiter L.M. McPhee J. Cahill C.M. Zhan S.S. Potter H. Nilsson L.N. J. Biol. Chem. 1999; 274: 6421-6431Abstract Full Text Full Text PDF PubMed Scopus (257) Google Scholar). IL-1β is produced in the central nervous system (CNS) in response to damage and influences neuronal function by interacting with the type I IL-1 receptor expressed on neurons (10Srinivasan D. Yen J.H. Joseph D.J. Friedman W. J. Neurosci. 2004; 24: 6482-6488Crossref PubMed Scopus (150) Google Scholar, 11Viviani B. Bartesaghi S. Gardoni F. Mezzani A. Behrens M.M. Bartfai T. Binaglia. M. Corsini E. Di Luca M. Galli C.L. Marinovich M. J. Neurosci. 2003; 23: 8692-8700Crossref PubMed Google Scholar). IL-1β is overexpressed in AD (12Griffin W.S. Stanley L.C. Ling C. White L. MacLeod V. Perrot L.J. White 3rd, C.L. Araoz C. Proc. Natl. Acad. Sci. U.S.A. 1989; 86: 7611-7615Crossref PubMed Scopus (1640) Google Scholar) and has been implicated in initiation and progression of AD pathology (13Nicoll J.A. Mrak R.E. Graham D.I. Stewart J. Wilcock G. MacGowan S. Esiri M.M. Murray L.S. Dewar D. Love S. Moss T. Griffin W.S. Ann. Neurol. 2000; 47: 365-368Crossref PubMed Scopus (345) Google Scholar). In addition, IL-1β promotes APP transcription (14Goldgaber D. Harris H.W. Hla T. Maciag T. Donnelly R.J. Jacobsen J.S. Vitek M.P. Gajdusek D.C. Proc. Natl. Acad. Sci. U.S.A. 1989; 86: 7606-7610Crossref PubMed Scopus (517) Google Scholar) and translation (9Rogers J.T. Leiter L.M. McPhee J. Cahill C.M. Zhan S.S. Potter H. Nilsson L.N. J. Biol. Chem. 1999; 274: 6421-6431Abstract Full Text Full Text PDF PubMed Scopus (257) Google Scholar) in various cell types. Transcriptional and post-transcriptional regulation of APP expression has been widely studied and correlated to AD pathogenesis (15Theuns J. Van Broeckhoven C. Hum. Mol. Genet. 2000; 9: 2383-2394Crossref PubMed Scopus (65) Google Scholar, 16Amara F.M. Junaid A. Clough R.R. Liang B. Brain Res. Mol. Brain Res. 1999; 71: 42-49Crossref PubMed Scopus (64) Google Scholar). Both cell type-specific promoter elements (17Ge Y.W. Ghosh C. Song W. Maloney B. Lahiri D.K. J. Neurochem. 2004; 90: 1432-1444Crossref PubMed Scopus (23) Google Scholar) and regulatory elements in the 5′- and 3′-UTRs of APP mRNA have been identified (9Rogers J.T. Leiter L.M. McPhee J. Cahill C.M. Zhan S.S. Potter H. Nilsson L.N. J. Biol. Chem. 1999; 274: 6421-6431Abstract Full Text Full Text PDF PubMed Scopus (257) Google Scholar, 18Broytman O. Westmark P.R. Gurel Z. Malter J.S. Neurobiol. Aging. 2009; 30: 1962-1974Crossref PubMed Scopus (11) Google Scholar).MicroRNAs are an intriguing class of small noncoding RNA molecules which, in mammals, regulate gene expression primarily by imperfect base pairing with the 3′-UTR of specific target mRNAs (19Bartel D.P. Cell. 2009; 136: 215-233Abstract Full Text Full Text PDF PubMed Scopus (15577) Google Scholar). MicroRNAs associate with Argonaute proteins (Ago1–4, in mammals) (20Hutvágner G. Zamore P.D. Science. 2002; 297: 2056-2060Crossref PubMed Scopus (1620) Google Scholar, 21Yan K.S. Yan S. Farooq A. Han A. Zeng L. Zhou M.M. Nature. 2003; 426: 468-474Crossref PubMed Scopus (347) Google Scholar), which constitute the core of the RNA-induced silencing complex (RISC), and mediate post-transcriptional repression of target messenger RNAs (19Bartel D.P. Cell. 2009; 136: 215-233Abstract Full Text Full Text PDF PubMed Scopus (15577) Google Scholar). Ago2 is expressed at high levels in human (22Sasaki T. Shiohama A. Minoshima S. Shimizu N. Genomics. 2003; 82: 323-330Crossref PubMed Scopus (324) Google Scholar) and mouse (23González-González E. López-Casas P.P. del Mazo J. Biochim. Biophys. Acta-Gene Regulatory Mechanisms. 2008; 1179: 306-311Crossref Scopus (48) Google Scholar) brain and Argonaute expression profiling or depleting Ago1-4 has been used to identify potential microRNA targets (24Schmitter D. Filkowski J. Sewer A. Pillai R.S. Oakeley E.J. Zavolan M. Svoboda P. Filipowicz W. Nucleic Acids Res. 2006; 34: 4801-4815Crossref PubMed Scopus (163) Google Scholar, 25Hong X. Hammell M. Ambros V. Cohen S.M. Proc. Natl. Acad. Sci. U.S.A. 2009; 106: 15085-15090Crossref PubMed Scopus (39) Google Scholar). Several studies have indicated that microRNAs define the spatial and temporal expression profiles of genes involved in neuronal development and differentiation (26Barbato C. Giorgi C. Catalanotto C. Cogoni C. Mamm. Genome. 2008; 19: 541-551Crossref PubMed Scopus (36) Google Scholar). In addition, microRNAs are recruited during the execution of neuronal signal transduction pathways (27Fiore R. Khudayberdiev S. Christensen M. Siegel G. Flavell S.W. Kim T.K. Greenberg M.E. Schratt G. EMBO J. 2009; 28: 697-710Crossref PubMed Scopus (315) Google Scholar). Emerging evidence suggests that changes in expression of microRNAs are associated with neurodegenerative diseases (28Barbato C. Ruberti F. Cogoni C. J. Biomed. Biotechnol. 2009; (2009): 871313PubMed Google Scholar). Profiling microRNAs from selected human brain areas has revealed significant changes in AD patients (29Lukiw W.J. Neuroreport. 2007; 18: 297-300Crossref PubMed Scopus (526) Google Scholar, 30Hébert S.S. Horré K. Nicolaï L. Papadopoulou A.S. Mandemakers W. Silahtaroglu A.N. Kauppinen S. Delacourte A. De Strooper B. Proc. Natl. Acad. Sci. U.S.A. 2008; 105: 6415-6420Crossref PubMed Scopus (896) Google Scholar, 31Cogswell J.P. Ward J. Taylor I.A. Waters M. Shi Y. Cannon B. Kelnar K. Kemppainen J. Brown D. Chen C. Prinjha R.K. Richardson J.C. Saunders A.M. Roses A.D. Richards C.A. J. Alzheimers Dis. 2008; 14: 27-41Crossref PubMed Scopus (719) Google Scholar). A few microRNAs, involved in the regulation of genes causally linked to Alzheimer's disease, are dysregulated in human AD patients (30Hébert S.S. Horré K. Nicolaï L. Papadopoulou A.S. Mandemakers W. Silahtaroglu A.N. Kauppinen S. Delacourte A. De Strooper B. Proc. Natl. Acad. Sci. U.S.A. 2008; 105: 6415-6420Crossref PubMed Scopus (896) Google Scholar, 32Hébert S.S. Horré K. Nicolaï L. Bergmans B. Papadopoulou A.S. Delacourte A. De Strooper B. Neurobiol. Dis. 2009; 33: 422-428Crossref PubMed Scopus (318) Google Scholar, 33Wang W.X. Rajeev B.W. Stromberg A.J. Ren N. Tang G. Huang Q. Rigoutsos I. Nelson P.T. J. Neurosci. 2008; 28: 213-223Google Scholar) and AD mouse models (34Boissonneault V. Plante I. Rivest S. Provost P. J. Biol. Chem. 2009; 284: 1971-1981Abstract Full Text Full Text PDF PubMed Scopus (250) Google Scholar).The hippocampus is one of the main brain regions affected during the early stages of AD, and changes in the hippocampus coincide with the memory deficits observed in AD patients. Therefore, elucidation of the molecular mechanisms regulating APP expression in primary hippocampal neurons will be useful in understanding this disease.In the present work, we focused on identifying a microRNA regulating APP expression in primary cultures of rat hippocampal neurons. In addition, we have analyzed the response of this microRNA to treatment of the cultures with IL-1β.DISCUSSIONAPP is one of the genes potentially regulated by the microRNA pathway in hippocampal neurons, since APP protein levels were up-regulated in neurons in which Ago2 was silenced. Reducing Ago2 levels did not significantly affect APP mRNA levels, suggesting that APP up-regulation is not the consequence of an indirect effect on APP transcription.The experiments presented here suggest that APP mRNA may be loaded into the RISC complex and may be directly regulated by specific microRNAs. Among microRNAs potentially targeting the APP 3′-UTR, miR-101 is a microRNA with two putative REs within the APP 3′-UTR and is also expressed in adult hippocampal tissue. Expression of miR-101 and APP both in embryonic primary hippocampal cell cultures and in postnatal rat hippocampal tissues further support the hypothesis that miR-101 is a repressor of hippocampal APP expression. Indeed, using a luciferase assay, we demonstrated that miR-101 actively represses a reporter containing the APP 3′-UTR. In addition, using site directed mutagenesis, a functional interaction between miR-101 and one of two microRNA REs within the APP 3′-UTR was identified. A number of regulatory elements which or APP mRNA have been within the APP 3′-UTR Malter J.S. J. Biol. Chem. Full Text PDF PubMed Google Scholar, P.R. Westmark Malter J.S. Neurobiol. Aging. 2006; PubMed Scopus Google Scholar). a demonstrated that a for to the APP expression S.S. Horré K. Nicolaï L. Bergmans B. Papadopoulou A.S. Delacourte A. De Strooper B. Neurobiol. Dis. 2009; 33: 422-428Crossref PubMed Scopus (318) Google Scholar). that the APP 3′-UTR is the target of regulatory which may constitute an will be to define the functional between the regulatory and of function experiments identified miR-101 a negative regulator of APP in rat hippocampal neurons. overexpression reduced Aβ load and levels in neuronal Aβ into and is involved in AD pathogenesis C. Selkoe D.J. Nat. Rev. Mol. Cell Biol. 2007; 8: 101-112Crossref PubMed Scopus (3811) Google Scholar) and levels of which to are associated with AD K. C. Brain Res. 1999; PubMed Scopus Google Scholar). Thus, suggest that miR-101 a role in AD. In the by miR-101 overexpression may to the regulation of APP is for the of and has been to of APP mRNA and R.K. S. R.J. J. Neurosci. 1999; 19: PubMed Google Scholar) and to Aβ T. T. T. K. Y. W. M. S. T. T. J. Biol. Chem. 2007; Full Text Full Text PDF PubMed Scopus Google Scholar). Thus, the of APP and of Aβ in the may suggest that miR-101 can by both APP and which also levels. putative miR-101 targets may be associated with APP and Aβ is an that we will be in of IL-1β on APP expression has been analyzed in various cell in primary neuronal cell IL-1β was to the transcription of APP R. N. E. De G. Neurosci. PubMed Scopus Google Scholar). Here, we demonstrated that treatment of hippocampal cultures with IL-1β increased APP through regulation of since the of APP mRNA did not increase IL-1β treatment APP protein levels were In addition, miR-101 may to the in APP expression IL-1β suggesting a role for miR-101 in the of APP expression in response to the regulation of APP translation may be the of have in human (9Rogers J.T. Leiter L.M. McPhee J. Cahill C.M. Zhan S.S. Potter H. Nilsson L.N. J. Biol. Chem. 1999; 274: 6421-6431Abstract Full Text Full Text PDF PubMed Scopus (257) Google Scholar), IL-1β translation of APP through the of the APP Thus, further of the role of miR-101 in regulating APP and its potential interaction with regulatory pathways will be expression of microRNAs has been in AD patients. expression profiles (30Hébert S.S. Horré K. Nicolaï L. Papadopoulou A.S. Mandemakers W. Silahtaroglu A.N. Kauppinen S. Delacourte A. De Strooper B. Proc. Natl. Acad. Sci. U.S.A. 2008; 105: 6415-6420Crossref PubMed Scopus (896) Google Scholar, J. Zhou PubMed Scopus Google Scholar) have that miR-101 is in the human AD suggesting that miR-101 down-regulation may a role in the development of AD. hypothesis is in with that a role of miR-101 in APP translation and Aβ studies in AD models will be to define the of miR-101 in the development and progression of AD IntroductionAlzheimer disease (AD) 2The abbreviations used are: ADAlzheimer diseaseAPPamyloid precursor proteinAβamyloid βRISCRNA-induced silencing complexREsresponsive elementsUTRuntranslated regionIL-1βinterleukin-1βEGFPenhanced green fluorescent proteinCox-2cyclooxygenasesAPPsoluble N-terminal fragmentPGE2prostaglandin E2TricineN-[2-hydroxy-1,1-bis(hydroxymethyl)ethyl]glycineAgo2Argonaute-2DIVdays in vitroGAPDHglyceraldehyde-3-phosphate dehydrogenaseTBPTATA-binding protein. is the most common form of dementia in aged individuals and is characterized by Aβ plaques, which contain Aβ aggregates and neurofibrillary tangles which consist primarily of aggregated forms of the microtubule-stabilizing protein tau (reviewed in Ref. 1Haass C. Selkoe D.J. Nat. Rev. Mol. Cell Biol. 2007; 8: 101-112Crossref PubMed Scopus (3811) Google Scholar). Aβ peptides are derived from processing of the type I transmembrane protein APP through sequential cleavages by β and γ secretase (2Yan R. Bienkowski M.J. Shuck M.E. Miao H. Tory M.C. Pauley A.M. Brashier J.R. Stratman N.C. Mathews W.R. Buhl A.E. Carter D.B. Tomasselli A.G. Parodi L.A. Heinrikson R.L. Gurney M.E. Nature. 1999; 402: 533-537Crossref PubMed Scopus (1328) Google Scholar, 3Wolfe M.S. Xia W. Ostaszewski B.L. Diehl T.S. Kimberly W.T. Selkoe D.J. Nature. 1999; 398: 513-517Crossref PubMed Scopus (1676) Google Scholar). The Aβ load during pathology leads to neurological dysfunction. APP is linked to AD; familial AD can be caused by increased expression of APP due to either genomic duplication (4Podlisny M.B. Lee G. Selkoe D.J. Science. 1987; 238: 669-671Crossref PubMed Scopus (117) Google Scholar, 5Rovelet-Lecrux A. Hannequin D. Raux G. Le Meur N. Laquerrière A. Vital A. Dumanchin C. Feuillette S. Brice A. Vercelletto M. Dubas F. Frebourg T. Campion D. Nat. Genet. 2006; 38: 24-26Crossref PubMed Scopus (959) Google Scholar) or regulatory sequence alterations (6Theuns J. Brouwers N. Engelborghs S. Sleegers K. Bogaerts V. Corsmit E. De Pooter T. van Duijn C.M. De Deyn P.P. Van Broeckhoven C. Am. J. Hum. Genet. 2006; 78: 936-946Abstract Full Text Full Text PDF PubMed Scopus (156) Google Scholar). Among the physiological and pathological activators of APP expression (7Mobley W.C. Neve R.L. Prusiner S.B. McKinley M.P. Proc. Natl. Acad. Sci. U.S.A. 1988; 85: 9811-9815Crossref PubMed Scopus (225) Google Scholar, 8Dewji N.N. Do C. Brain Res. Mol. Brain Res. 1996; 35: 325-328Crossref PubMed Scopus (40) Google Scholar) is the proinflammatory cytokine IL-1β (9Rogers J.T. Leiter L.M. McPhee J. Cahill C.M. Zhan S.S. Potter H. Nilsson L.N. J. Biol. Chem. 1999; 274: 6421-6431Abstract Full Text Full Text PDF PubMed Scopus (257) Google Scholar). IL-1β is produced in the central nervous system (CNS) in response to damage and influences neuronal function by interacting with the type I IL-1 receptor expressed on neurons (10Srinivasan D. Yen J.H. Joseph D.J. Friedman W. J. Neurosci. 2004; 24: 6482-6488Crossref PubMed Scopus (150) Google Scholar, 11Viviani B. Bartesaghi S. Gardoni F. Mezzani A. Behrens M.M. Bartfai T. Binaglia. M. Corsini E. Di Luca M. Galli C.L. Marinovich M. J. Neurosci. 2003; 23: 8692-8700Crossref PubMed Google Scholar). IL-1β is overexpressed in AD (12Griffin W.S. Stanley L.C. Ling C. White L. MacLeod V. Perrot L.J. White 3rd, C.L. Araoz C. Proc. Natl. Acad. Sci. U.S.A. 1989; 86: 7611-7615Crossref PubMed Scopus (1640) Google Scholar) and has been implicated in initiation and progression of AD pathology (13Nicoll J.A. Mrak R.E. Graham D.I. Stewart J. Wilcock G. MacGowan S. Esiri M.M. Murray L.S. Dewar D. Love S. Moss T. Griffin W.S. Ann. Neurol. 2000; 47: 365-368Crossref PubMed Scopus (345) Google Scholar). In addition, IL-1β promotes APP transcription (14Goldgaber D. Harris H.W. Hla T. Maciag T. Donnelly R.J. Jacobsen J.S. Vitek M.P. Gajdusek D.C. Proc. Natl. Acad. Sci. U.S.A. 1989; 86: 7606-7610Crossref PubMed Scopus (517) Google Scholar) and translation (9Rogers J.T. Leiter L.M. McPhee J. Cahill C.M. Zhan S.S. Potter H. Nilsson L.N. J. Biol. Chem. 1999; 274: 6421-6431Abstract Full Text Full Text PDF PubMed Scopus (257) Google Scholar) in various cell types. Transcriptional and post-transcriptional regulation of APP expression has been widely studied and correlated to AD pathogenesis (15Theuns J. Van Broeckhoven C. Hum. Mol. Genet. 2000; 9: 2383-2394Crossref PubMed Scopus (65) Google Scholar, 16Amara F.M. Junaid A. Clough R.R. Liang B. Brain Res. Mol. Brain Res. 1999; 71: 42-49Crossref PubMed Scopus (64) Google Scholar). Both cell type-specific promoter elements (17Ge Y.W. Ghosh C. Song W. Maloney B. Lahiri D.K. J. Neurochem. 2004; 90: 1432-1444Crossref PubMed Scopus (23) Google Scholar) and regulatory elements in the 5′- and 3′-UTRs of APP mRNA have been identified (9Rogers J.T. Leiter L.M. McPhee J. Cahill C.M. Zhan S.S. Potter H. Nilsson L.N. J. Biol. Chem. 1999; 274: 6421-6431Abstract Full Text Full Text PDF PubMed Scopus (257) Google Scholar, 18Broytman O. Westmark P.R. Gurel Z. Malter J.S. Neurobiol. Aging. 2009; 30: 1962-1974Crossref PubMed Scopus (11) Google Scholar).MicroRNAs are an intriguing class of small noncoding RNA molecules which, in mammals, regulate gene expression primarily by imperfect base pairing with the 3′-UTR of specific target mRNAs (19Bartel D.P. Cell. 2009; 136: 215-233Abstract Full Text Full Text PDF PubMed Scopus (15577) Google Scholar). MicroRNAs associate with Argonaute proteins (Ago1–4, in mammals) (20Hutvágner G. Zamore P.D. Science. 2002; 297: 2056-2060Crossref PubMed Scopus (1620) Google Scholar, 21Yan K.S. Yan S. Farooq A. Han A. Zeng L. Zhou M.M. Nature. 2003; 426: 468-474Crossref PubMed Scopus (347) Google Scholar), which constitute the core of the RNA-induced silencing complex (RISC), and mediate post-transcriptional repression of target messenger RNAs (19Bartel D.P. Cell. 2009; 136: 215-233Abstract Full Text Full Text PDF PubMed Scopus (15577) Google Scholar). Ago2 is expressed at high levels in human (22Sasaki T. Shiohama A. Minoshima S. Shimizu N. Genomics. 2003; 82: 323-330Crossref PubMed Scopus (324) Google Scholar) and mouse (23González-González E. López-Casas P.P. del Mazo J. Biochim. Biophys. Acta-Gene Regulatory Mechanisms. 2008; 1179: 306-311Crossref Scopus (48) Google Scholar) brain and Argonaute expression profiling or depleting Ago1-4 has been used to identify potential microRNA targets (24Schmitter D. Filkowski J. Sewer A. Pillai R.S. Oakeley E.J. Zavolan M. Svoboda P. Filipowicz W. Nucleic Acids Res. 2006; 34: 4801-4815Crossref PubMed Scopus (163) Google Scholar, 25Hong X. Hammell M. Ambros V. Cohen S.M. Proc. Natl. Acad. Sci. U.S.A. 2009; 106: 15085-15090Crossref PubMed Scopus (39) Google Scholar). Several studies have indicated that microRNAs define the spatial and temporal expression profiles of genes involved in neuronal development and differentiation (26Barbato C. Giorgi C. Catalanotto C. Cogoni C. Mamm. Genome. 2008; 19: 541-551Crossref PubMed Scopus (36) Google Scholar). In addition, microRNAs are recruited during the execution of neuronal signal transduction pathways (27Fiore R. Khudayberdiev S. Christensen M. Siegel G. Flavell S.W. Kim T.K. Greenberg M.E. Schratt G. EMBO J. 2009; 28: 697-710Crossref PubMed Scopus (315) Google Scholar). Emerging evidence suggests that changes in expression of microRNAs are associated with neurodegenerative diseases (28Barbato C. Ruberti F. Cogoni C. J. Biomed. Biotechnol. 2009; (2009): 871313PubMed Google Scholar). Profiling microRNAs from selected human brain areas has revealed significant changes in AD patients (29Lukiw W.J. Neuroreport. 2007; 18: 297-300Crossref PubMed Scopus (526) Google Scholar, 30Hébert S.S. Horré K. Nicolaï L. Papadopoulou A.S. Mandemakers W. Silahtaroglu A.N. Kauppinen S. Delacourte A. De Strooper B. Proc. Natl. Acad. Sci. U.S.A. 2008; 105: 6415-6420Crossref PubMed Scopus (896) Google Scholar, 31Cogswell J.P. Ward J. Taylor I.A. Waters M. Shi Y. Cannon B. Kelnar K. Kemppainen J. Brown D. Chen C. Prinjha R.K. Richardson J.C. Saunders A.M. Roses A.D. Richards C.A. J. Alzheimers Dis. 2008; 14: 27-41Crossref PubMed Scopus (719) Google Scholar). A few microRNAs, involved in the regulation of genes causally linked to Alzheimer's disease, are dysregulated in human AD patients (30Hébert S.S. Horré K. Nicolaï L. Papadopoulou A.S. Mandemakers W. Silahtaroglu A.N. Kauppinen S. Delacourte A. De Strooper B. Proc. Natl. Acad. Sci. U.S.A. 2008; 105: 6415-6420Crossref PubMed Scopus (896) Google Scholar, 32Hébert S.S. Horré K. Nicolaï L. Bergmans B. Papadopoulou A.S. Delacourte A. De Strooper B. Neurobiol. Dis. 2009; 33: 422-428Crossref PubMed Scopus (318) Google Scholar, 33Wang W.X. Rajeev B.W. Stromberg A.J. Ren N. Tang G. Huang Q. Rigoutsos I. Nelson P.T. J. Neurosci. 2008; 28: 213-223Google Scholar) and AD mouse models (34Boissonneault V. Plante I. Rivest S. Provost P. J. Biol. Chem. 2009; 284: 1971-1981Abstract Full Text Full Text PDF PubMed Scopus (250) Google Scholar).The hippocampus is one of the main brain regions affected during the early stages of AD, and changes in the hippocampus coincide with the memory deficits observed in AD patients. Therefore, elucidation of the molecular mechanisms regulating APP expression in primary hippocampal neurons will be useful in understanding this disease.In the present work, we focused on identifying a microRNA regulating APP expression in primary cultures of rat hippocampal neurons. In addition, we have analyzed the response of this microRNA to treatment of the cultures with
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