Polymorphic Variations in 5 HT2A, 5 HTT and DISC 1 in first episode schizophrenia patients

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1 PolymorphicVariationsin5 HT2A,5 HTTandDISC1infirst episodeschizophreniapatients L.MedinaGonzález,DepartmentofClinicalChemistry,RamónyCajalHospital,Madrid. PhD.MJArranz,SectionofClinicalNeuropharmacologyattheInstituteofPsychiatry, London. Introduction Schizophreniaisaseverepsychoticdisordercharacteristicallymarkedbyaretreatfrom realitywithdelusionformation,hallucinations,emotionaldisharmony,andregressive behaviour.affectingapproximately1%oftheworldwidepopulationandisassociatedwitha highrateofmorbidityandmortality.studiessuggestthatgenetics,earlyenvironment, neurobiologyandpsychologicalandsocialprocessesareimportantcontributoryfactors. Family,twin,andadoptionstudiesprovidedstrongevidenceofageneticcontributiontothe aetiologyofschizophrenia.however,attemptstoisolatingspecificgenesthatconfer vulnerabilitytothedisorderhavethusfarbeenonlymoderatelysuccesful.schizophreniaisa conditionofcomplexinheritance,withseveralgenespossiblyinteractingtogenerateriskfor schizophrenia.schizophreniaisachronicdiseasewithoutremissionandthetreatment requirestheuseofantipsychoticdrugs.antipsychoticshaveamultitargetprofilewithouta clearmechanismofaction.theaimsofpharmacogeneticinvestigationsaretheidentification ofgenesinfluencingresponse,validationoftargets,predictionoftreatmentresponse, predictionofside effects,identificationofpatientslikelytorespondtoaparticular treatment,andtheselectionofmostbeneficialtreatmentaccordingtogeneticprofile. Identificationofdrug targetmutationswithadirectinfluenceontreatmentoutcomewould constituteevidenceofspecificmediatorsofdrugactivity(1).currentlyavailable antipsychoticdrugsachieveacertaindegreeofclinicalimprovementinthetreatmentof psychosisinabout50%ofschizophreniapatients(1 3).Antipsychotictreatmentfailurehas substantialclinicalandeconomiccosts.delayinfindinganadequatetreatmentforpsychosis hasadetrimentaleffectonpatients prognosisandchancesofrecovery(4 5).Thesestrong implicationsreinforcetheneedforpharmacogeneticresearchintofactorsaffecting antipsychoticresponseandwaystopredictclinicaloutcome.

2 Aimofstudy Thestandardisationofmethodstogenotypethreepolymorphism(5HT2A102T/C, 5HTTLPRandrs25531)andtwomicrosatellitemarkers(D1S2709andD1S2833),inorder tostudythesepolymorphismsinschizophreniapatients.asampleof200spanishcaucasian firstepisodeschizophreniapatientsandasampleof340healthycontrolsubjectsmatched forethnicoriginwereusedinthestudy.thesepatientswereevaluatedatbaseline,andafter 3,6and12monthsafterthestartofthetreatmenttoassesstreatmentresponse. Methods1.Selectionof polymorphisms Polymorphismswereselectedfrompreviousreportswhichshowedassociationwith schizophreniaandtreatmentoutcome. 1.1Serotoninsystem Alterationsoftheserotonergicsystemhavebeenimplicatedindepression,anxiety,eating disordersandnegativesymptomsofschizophrenia.antipsychoticdrugs,speciallythe atypicalantipsychotics,showaffinityforserotonin(5 HT)neurotransmitterreceptorsand themostextensivelystudiedhavebeenthe5ht2aand5 HT2C.Manyreportshave associatedasilent5ht2a102 T/Cpolymorphismwiththeresponsetoclozapineand risperidone.thispolymorphismisinnearlycompletelinkagedisequilibrium(ld)witha 1438 G/ApromoterpolymorphisminCaucasianpopulations(1,6,7,8).Theselective serotoninreuptakeinhibitors(ssris)arethemostwidelyprescribedantidepressants worldwide.despiterecentadvancesinantidepressantpharmacotherapy,responseratesare variableandcanbelowas60%forthefirstdrugadministered.theunderlyingmechanism forthisvariationiscomplex,involvingbothenvironmentalandgeneticsfactorsandtheir interactions.onepossiblegeneticmechanisminvolvestheserotonintransportergene (SLC6A4)whichencodestheserotonintransporter(5 HTT)protein.Thisproteininitiates theantidepressanteffectofssris,whicharedrugsthatarethoughttoactprimarilyby terminatingserotoninreuptakebythepresynapticserotonergicneuron.geneticvariations in5 HTT LPRpolymorphismhavebeenalsofoundtobeassociatedwithvariationsin antipsychoticdrugresponse(arranzetal.,2000(9).moststudieshavefocusedonasingle commonpolymorphismlocatedinthepromoterregionoftheslc6a4.this insertion/deletionpolymorphism,reportedtobe43bpinlength,iscommonlysubdivided intos(short)andl(long)(10,11)alleles.thelongallelehasshownahigherprotein transcriptionthantheshortallele(12).recentreportshavedetectedasinglenucleotide polymorphism

3 (SNP),rs25531A>G,nearthepromoterregionoftheSLC6A4(13).ThisSNPsubdividedthe previoussandlpolymorphismintola,sa,lgandsg. 1.2Disrupted in Schizophrenia 1(DISC1) Disrupted in Schizophrenia 1(DISC 1)wasidentifiedasthesolegeneinwhichamutant truncationbyabalancedtraslocation(1;11)(p42.1;q14.3)iscosegregatedwith schizophreniainalargescottishfamily(14).thedisc1locushasnowbeenimplicatedby cytogenetics,linkageandassociationstudiesasapredisposingriskfactorfor neuropsychiatricillnesses,includingschizophrenia,schizophreniaspectrum,bipolar, depressionandautismspectrumdisorders.despiteafewnegativereports,theaccumulating geneticevidenceisstronglypositive.weselectedtwomicrosatellitemarkersd1sc2709and thed1s2833whichwerefoundbyekelundandcolleagues.thesetwomicrosatellitemarkers inthedisc1geneprovidedstrongevidenceforlinkagetoschizophreniainafinnishfamily (15,16). 2.Genotypingmethods 2.1GenotypingbyRFLPof5 HT2A102 T/Candthe5 HTTLPR&25531 polymorphisms Westandardisedtwopolymerasechainreactionprotocolsfollowedbyrestrictionfragment lengthpolymorphismanalyses(pcr RFLP)forgenotypingthe5 HT2A102 T/Candthe5 HTTLPR&25531polymorphisms.DNAwasamplifiedin25uLcontaining50nggenomic DNA,10mMdNTPs,0.5UofTaqpolymerase,afinalconcentrationofMgCl2of3mMfor the5 HT2A102 T/Cand1mMforthe5 HTTLPR& Table1showsthefinalconcentrationsandthesequencesofoligonucleotideprimersfor eachpolymorphism.thermalcyclingconsistedof35cyclesof96oc(35s),60oc(60s)for the5ht2a102 T/Cor65.5oC(60s)forthe5 HTTLPR&25531and72o(60s)eachwitha finalextensionstepof10minat72ac.subsequently,15ulofpcrproductweredigestedby MspIat37oCovernight.FinallythePCRandthedigestionproductwereloadedontoan agarosegelandvisualizedbyethidiumbromide(table1,figure1and2).

4 Table 1. Description of the primers concentrations, sequences and PCR products.

5 Figure 1. PCR product of the 5-HT2A 102-T/C. The picture shows the three possibles genotypes T/T,T/C and C/C.

Figure 2. 5-HTT LPR & 25531 genotype. The first lane of each individual represent the PCR product,and the second one, the digestion product. 2.2AutomaticgenotypingofD1S2709andD1S2833microsatellites DNA was amplified in 25uL containing 2ng genomic DNA, 10mM dntps, 0.

6 Figure 2. 5-HTT LPR & genotype. The first lane of each individual represent the PCR product,and the second one, the digestion product. 2.2AutomaticgenotypingofD1S2709andD1S2833microsatellites DNA was amplified in 25uL containing 2ng genomic DNA, 10mM dntps, 0.5 U of Taq polymerase,afinalconcentrationofmgcl2of2mmforthed1s2709and1mmforthed1s 2833.Thermalcyclingconsistedof35cyclesof96oC(35s),60oC(60s)fortheD1S2709or 63oC(60s)fortheD1S2833and72oC(60s)eachwithafinalextensionstepof10minat 72oC. The primer sequences and concentrations are shown in Table 1. Subsequently, the lengthofthepcrproductwasanalyzedintheabiprism 3100bycapillaryelectrophoresis. Our electrophoregrams results showed a microsatellite size range between bp for thed1s2709and bpfortheD1S2833. Results Atthemomentwehavetheresultsofthegenotypingof5 HT2A102 T/Candthe5 HTTLPR &25531polymorphismsincontrolsandpatients.However,weonlyhavethefirstresultsfor thedisc1microsatellitegenotypingandmoretestsshouldbecarriedout.nowwe

7 havetocheckthesequenceofthemicrosatellitepolymorphisminordertoidentifythetrue lengthoftheallelebetweenthestutterproducts.theaimistoknowtheallelefrequenciesof thesepolymorphismsinourpopulationandtostudytheassociationbetweeneach polymorphismandthetreatmentresponse.forthisstudywearegoingtousestatistical analysesoffrequencydistributionandhaplotypecombinations. Conclusion Pharmacogeneticsfindingsconstituteaclearadvancetowardsafuturetailoringof antipsychotictreatmenttoindividualneeds.however,furtherdevelopmentofthefieldcan beobtainedbytheapplicationofpharmacogenomicstrategiestotheidentificationofnovel factorsinfluencingresponse. References 1. Arranz MJ and de Leon J. Pharmacogenetics and pharmacogenomics of schizophrenia: a review of last decade of research. Mol Psychiatry Aug;12(8): Miyamoto S, Duncan GE, Marx CE, Lieberman JA. Treatments for schizophrenia: a critical review of pharmacology and mechanisms of action of antipsychotic drugs. Mol Psychiatry Jan;10(1): Kerwin RW, Osborne S. Antipsychotic drugs. Medicine 2000; 28: Perkins DO, Gu H, Boteva K, Lieberman JA. Relationship between duration of untreated psychosis and outcome in first-episode schizophrenia: a critical review and meta-analysis. Am J Psychiatry Oct;162(10): Lieberman JA, Stroup TS, McEvoy JP, Swartz MS, Rosenheck RA, Perkins DO, Keefe RS, Davis SM, Davis CE, Lebowitz BD, Severe J, Hsiao JK; Clinical Antipsychotic Trials of Intervention Effectiveness (CATIE) Investigators Effectiveness of antipsychotic drugs in patients with chronic schizophrenia. N Engl J Med Sep 22;353(12): Arranz MJ, Munro J, Sham P, Kirov G, Murray RM, Collier DA, Kerwin RW. Meta-analysis of studies on genetic variation in 5-HT2A receptors and clozapine response. Schizophr Res Jul 27;32(2): Arranz MJ, Munro J, Owen MJ, Spurlock G, Sham PC, Zhao J, Kirov G, Collier DA, Kerwin RW. Evidence for association between polymorphisms in the promoter and coding regions of the 5-HT2A receptor gene and response to clozapine. Mol Psychiatry Jan;3(1): Lane HY, Chang YC, Chiu CC, Chen ML, Hsieh MH, Chang WH. Association of risperidone treatment response with a polymorphism in the 5-HT(2A) receptor gene. Am J Psychiatry Sep;159(9): Arranz MJ, Bolonna AA, Munro J, Curtis CJ, Collier DA and Kerwin RW The serotonin transporter and Clozapine response. Molecular Psychiatry 5: Serretti A, Artioli. Pharmacogennomics J 2004; 4: Murphy DL, Lerner A, Rudnick G, Lesch KP. Serotonin transporter: gene, genetic disorders, and pharmacogenetics. Mol Interv Apr;4(2): Lesch KP, Balling U, Gross J, Strauss K, Wolozin BL, Murphy DL, Riederer P. Organization of the human serotonin transporter gene. J Neural Transm Gen Sect. 1994;95(2): Kraft JB, Peters EJ, Slager SL, Jenkins GD, Reinalda MS, McGrath PJ, Hamilton SP. Analysis of association between the serotonin transporter and antidepressant response in a large clinical sample. Biol Psychiatry Mar 15;61(6): Millar JK, James R, Christie S, Taylor MS, Devon RS, Hogg G et al. Functional characterisation of DISC 1, a candidate susceptibility gene for major psychiatric illness. Am J Med Genet 2002; 114: Ekelund J, Lichtermann D, Hovatta I, Ellonen P, Suvisaari J, Terwilliger JD, et al. Genome-wide scan for schizophrenia in the Finnish population: evidence for a locus on chromosome 7q22. Hum Mol Genet Apr 12;9(7): Ekelund J, Hovatta I, Parker A, Paunio T, Varilo T, Martin R, et al. Chromosome 1 loci in Finnish schizophrenia families. Hum Mol Genet Jul 15;10(15):

8 Acknowledgements IwouldliketothanktheIFCC(InternationalFederationofClinicalChemistryandLaboratory Medicine)foritssupportandtheSEQC(SpanishSocietyofClinicalBiochemistryandMolecular Pathology).IamalsogratefultoallthestaffoftheSectionofClinicalNeuropharmacologyatthe InstituteofPsychiatryinLondon,speciallyDr.MaríaJesúsArranz.

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www.lilly.com Eli Lilly and Company Lilly Corporate Center Indianapolis, Indiana 46285 U.S.A. Phone 317 276 2000 October 5, 2007 Re: Safety data on Zyprexa (olanzapine) and Symbyax (olanzapine and fluoxetine