Computational methods for DNA copy number detection
Kuupäev
2015-09-16
Autorid
Palta, Priit
Ajakirja pealkiri
Ajakirja ISSN
Köite pealkiri
Kirjastaja
Abstrakt
DNA koopiaarvu variantideks või muutusteks nimetatakse selliseid erinevusi inimeste geneetilises materjalis, mille puhul mingi DNA lõigu koopiaarv on erinev oodatavast koopiaarvust kaks (üks koopia mingit kindlat DNA järjestust emalt päritud kromosoomil ja üks koopia isalt päritud kromosoomil). DNA koopiate vähenemist nimetatakse deletsiooniks ning vastavaid DNA variante nimetatakse deletsioonideks. DNA koopiate juurdetulemist nimetatakse duplitseerumiseks ning selliseid kahest suurema koopiaarvuga variante vastavalt duplikatsioonideks.
Antud doktoritöös uuriti inimese DNA koopiaarvu variante, nende seotust erinevate haigustega ja nende tekkimise ja pärandumise eripärasid. Kasutades DNA mikrokiipe ehk geenikiipe uuriti esmalt kas ja millised DNA koopiaarvu muutused võivad olla seotud vaimse arengu mahajäämusega (VAM-ga). Uurides perekondasid, kus ühel või mitmel liikmel oli diagnoositud VAM, leiti mitmeid juba varem VAM-ga seostatud DNA koopiaarvu muutusi ning lisaks leiti ka mitmeid uusi DNA koopiaarvu variante, mille esinemine võib olla seotud VAM-e väljakujunemisega.
Sarnane uuring viidi läbi ka korduva spontaanse raseduse katkemise probleemiga paaride ja naiste puhul. Võrreldes nende patsientide gruppi kuuluvate naiste DNA koopiaarvu muutusi ning nende sagedusi terveid emasid sisaldavate kontroll-grupi indiviidide omadega, leiti statistiliselt ja bioloogiliselt oluline erinevus muutunud koopiaarvuga DNA lõigus, mis sisaldab PDZD2 ja GOLPH3 geene ja kus esinevate duplikatsioonide „omamine“ suurendas naistel märkimisväärselt spontaanse raseduse katkemise ohtu.
Doktoritöö viimases osas uuriti Tartu Ülikooli Eesti Geenivaramu ja rahvusvahelise HapMap projekti poolt kogutud tõsiste haigusteta inimestel esinevaid DNA koopiaarvu muutusi ja nende pärandumist perekondades. Selle uuringu üheks huvitavamaks tulemuseks oli deletsioonide alapärandumine vanematelt lastele ehk deletsioone kandvaid DNA regioone esines laste genoomides oluliselt vähem, kui normaalse Mendeliaalse (juhusliku) pärandumise korral oleks oodata võinud. Uurides duplikatsioonide regioone perekondades leiti aga, et kaks kolmandikku duplikatsioonides esinevatest DNA koopiatest ei olnud identsed (üksteise täpsed koopiad), vaid mõnevõrra erinevad, demonstreerides seniajani teadmata olnud alleelse varieeruvuse määra DNA duplikatsioonide regioonides.
DNA copy number variation is a type of genetic variation in which case the number of copies of a particular region of a chromosome is altered from its normal state. In the non-repetitive portion of the human genome, the normal haploid copy number is one – one copy of each sequence per chromosome. Accordingly, the normal diploid copy number in humans is two – one copy inherited from both parents. A copy number variant (CNV) can result from either a loss of copies (most often called a deletion) or gain of copies (called a duplication or amplification). In this thesis we studied DNA copy number variation in human – how CNVs emerge and how they are inherited from parents to offspring. We also analysed CNVs in the context of few different diseases. By using DNA microarrays we first aimed to determine if CNVs are associated with mental retardation (MR). For this we studied not only index cases with MR but larger nuclear families, where we discovered several already MR-associated CNVs and also a few novel CNV regions that are possibly associated with predisposition to MR. Similar study was conducted in couples and females suffering from recurrent miscarriage. By comparing CNVs and their frequencies in the latter group to these of healthy mothers, we discovered a multi-copy duplication at 5p13.3 that disrupts PDZD2 and GOLPH3 genes and significantly increases maternal risk for pregnancy complications. In the last part of this thesis we studied how CNVs are inherited in Estonian nuclear families (22 trios and 12 families with multiple siblings) and in HapMap Yoruban trios. We determined that deletion-carrying chromosomal regions were observed in the offspring slightly less frequently than expected by random Mendelian inheritance. By analysing duplication-carrying chromosomal regions in these families, we discovered that in two-thirds of such regions the duplicated copies of the underlying DNA sequence were not exactly identical but somewhat different, allowing us to define alternative allelic copies within these copy number gain-carrying chromosomal regions and demonstrating extensive and to-date unmeasured allelic variability in multi-copy CNV regions of the human genome.
DNA copy number variation is a type of genetic variation in which case the number of copies of a particular region of a chromosome is altered from its normal state. In the non-repetitive portion of the human genome, the normal haploid copy number is one – one copy of each sequence per chromosome. Accordingly, the normal diploid copy number in humans is two – one copy inherited from both parents. A copy number variant (CNV) can result from either a loss of copies (most often called a deletion) or gain of copies (called a duplication or amplification). In this thesis we studied DNA copy number variation in human – how CNVs emerge and how they are inherited from parents to offspring. We also analysed CNVs in the context of few different diseases. By using DNA microarrays we first aimed to determine if CNVs are associated with mental retardation (MR). For this we studied not only index cases with MR but larger nuclear families, where we discovered several already MR-associated CNVs and also a few novel CNV regions that are possibly associated with predisposition to MR. Similar study was conducted in couples and females suffering from recurrent miscarriage. By comparing CNVs and their frequencies in the latter group to these of healthy mothers, we discovered a multi-copy duplication at 5p13.3 that disrupts PDZD2 and GOLPH3 genes and significantly increases maternal risk for pregnancy complications. In the last part of this thesis we studied how CNVs are inherited in Estonian nuclear families (22 trios and 12 families with multiple siblings) and in HapMap Yoruban trios. We determined that deletion-carrying chromosomal regions were observed in the offspring slightly less frequently than expected by random Mendelian inheritance. By analysing duplication-carrying chromosomal regions in these families, we discovered that in two-thirds of such regions the duplicated copies of the underlying DNA sequence were not exactly identical but somewhat different, allowing us to define alternative allelic copies within these copy number gain-carrying chromosomal regions and demonstrating extensive and to-date unmeasured allelic variability in multi-copy CNV regions of the human genome.
Kirjeldus
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Märksõnad
DNA koopiaarvu variatsioonid, genoomid, arvutusmeetodid, bioinformaatika, DNA copy number variations, genomes, numerical methods, bioinformatics