Асоциативни изследвания на кандидат гени при български пациенти с афективни разстройства
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Дата
2016-02-18
Автори
Иванова-Стоевска/Ivanova-Stoevska, Мина Ангелова/ Mina Angelova
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ISSN на списанието
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Издател
Резюме
Цел и задачи ***** ЦЕЛ
Целта на настоящата дисертация е оценка на приноса на генетични варианти в
кандидат гени, подбрани на базата на ключови хипотези за етиологията на АР и
асоциирания с тях риск чрез провеждане на асоциативно изследване от типа случаи–
контроли и фамилно асоциативно изследване при българи и роми. ***
ІІІ. ЗАДАЧИ:
1. Събиране на биологичен материал и екстракция на ДНК от венозна кръв от
пациенти с поставена клинична диагноза АР, както и събиране на материал от техни
родственици и здрави контроли. Клиничната диагноза на пациентите е поставена чрез
валидизирани диагностични инструменти (DSM-IV, Diagnostic and Statistical Manual of
Mental Disorders).
2. Подбор на подходящи кандидат гени и ДНК полиморфизми с предполагаемо
участие в патогенезата на афективните разстройства.
3. Избор на подходящ метод за генотипиране и оптимизиране на условията на
реакциите.
4. Генотипиране на избраните маркери в група от пациенти с афективни
разстройства от български и ромски произход, техни родственици и съответстващите им
контроли чрез Real-Time PCR.
5. Статистическа обработка и анализ на получените резултати.
5.1. Определяне на алелните и генотипните честоти на изследваните маркери.
5.2. Сравняване на алелните и генотипните честоти между групите на болни с
афективни разстройства и съответстващите им здрави контроли от български и ромски
етнически произход.
5.3. Провеждане на фамилно-асоциативно изследване на ядрени семейства от двете
етнически групи и търсене на неравновесно предаване на определени генетични
варианти в засегнатото поколение.
5.4. Хаплотипен анализ и търсене на асоциирани хаплотипи или неравновесно
предаване на определени хаплотипи на пациентите от техните родители при семействата.
5.6. Изследване за статистическа епистаза между всички генотипирани варианти. ***** SUMMARY:
Affective disorders (AD) are among the most severe psychiatric conditions having great
impact on normal life of the patients with high comorbid risk for suicide attempts and addiction
behavior. They are recognized as global burden in the annual reports of the WHO. The detailed
understanding of the etiology and pathology of AD is aiming development of more
individualized treatment approach and improvement of patient’s quality of life.
There are few hypothesis based mainly on the observed changes in neurotransmission,
neuroplasticity, inefficient communication between neurons and some somatic functions. In the
present study we investigated genetic variants in TPH2 and SLC6A4, responsible for serotonin
synthesis and transport and variants in DRD2 candidate gene from the dopamine
neurotransmission. Genetic variants in BDNF and DISC1 genes, involved in genesis, survival
and differentiation of neurons were investigate in relation to neuroplasticity changes.
Apart from inadequate neuroplasticity, the inefficient communication between neurons
could be as well consequence from membrane transport changes. Moreover recent genomewide
association studies (GWAS) drew attention to variants in genes coding membrane
channels and therefore we investigated variants in CACNA1C and ANK3A candidate genes.
Dysregulation of circadian rhythms and hypothalamic-pituitary axis are common in AD
as well and variants in CLOCK and CRH genes were investigated.
Case control study, family association study and analysis of statistical epistasis were
conducted. Two affection status definitions were considered, the narrow (A1) included subjects
with Bipolar Disorder type I (BDI), BD II and schizoaffective disorder, bipolar type (SAD)
while in the broad (A2) major depressive disorder (MDD) patients were included. The case
control study consisted of 304 patients from А1, 414 from А2 and 205 healthy prescreened
controls, matched by gender, ethnicity and age. The family sample consisted of 119 Bulgarian
and 56 Roma families with 197 patients from А1 and 269 from А2 status definitions. All cases
met DSM–IV criteria for AD and all participants provided written informed consent. Totally
1240 individuals with Bulgarian and 230 with Roma origin were genotyped.
Genomic DNA was extracted from venous blood and genotyping was performed with
TaqMan™ method with call rate for 384 plates over 95%. Overall 24 SNPs situated in 9 AD
candidate genes were investigated.
The results for TPH2 are demonstrating small effect for the investigated polymorphisms
in regards to AD susceptibility. Two preferentially transmitted haplotypes with the participation
of previously associated with panic disorder allele T of rs4570625 and the associated with AD
allele G of rs11178998 and allele A of rs4290270 were identified. Epistasis with variants in
DISC1 and SLC6A4 genes were also observed.
Allele and genotype association for rs12150214 (SLC6A4) with higher frequency of
allele C and genotypes containing it among patients was observed corresponding to dominant
effect of this allele leading to high AD risk. No association of the functional promoter
polymorphism but protective effect of L variant only in the context of epistasis with the TPH2
variant rs1386483 was noticed.
The relatively small effect of DRD2 gene for AD susceptibility was confirmed with the
identification of preferentially transmitted allele A of the situated in 5'UTR variant rs6589377
and transmission disequilibrium for few haplotypes (CG, CCG - over-transmitted; CCTG - under-transmitted). No involvement in statistical interactions of DRD2 polymorphisms is
detected.
The important role of neuroplasticity and more specifically the impact of DISC1 was
supported with the identification of transmission disequilibrium of several haplotypes and the
located in 3'UTR variant rs980989 as well as with the participation of DISC1 variants in
numerous interactions with different phenotype effect. Allele G of rs980989 and haplotype
TGT were found to be more frequently transmitted while haplotypes ATT, ATTA, GAT and
CGAT are under-transmitted.
Association for the situated in exon-intron boundaries rs16917237 in BDNF surviving
Bonferroni correction was reported for first time. Homozygote and heterozygote presence of
allele G was associated with high AD risk and several associated haplotypes were identified.
Interactions with protective effect with variants in DISC1 and CLOCK genes are also observed.
The hypothesis of influence of the investigated variants rs3805154 in CLOCK,
rs12721510 in CRH and rs1006737 in CACNA1C on AD susceptibility cannot be rejected.
Though no association or transmission disequilibrium was detected, interactions with various
phenotype effect of the investigated CLOCK and CRH variants with DISC1, BDNF and ANK3
variants were observed.
Preferential transmission of allele C of rs9804190 in ANK3 and participation in
protective epistasis with CRH variants were identified.
The lack of association for some of the investigated variants may be consequence of
absence of impact in our sample, insufficient sample size for detection of small effect variants
or influence only on certain endophenotype. Nevertheless the limitations of the statistical
epistasis analysis, the obtained results could be further used in hypothesis generating and
prioritization of approaches. Further studies in larger samples or in specific endophenotypes
could provide more detailed information about the impact of the investigated variants.
Описание
Дисертационен труд за присъждане на образователна и научна степен "Доктор" - София, 2015 г. Научни ръководители:
Академик проф. д-р В. Митев, дм, дбн;
Доц. Радка Кънева, дб;
Консултант: Проф. Иво Кременски ***** Област на висше образование: 4.Природни науки, математика и информатика
Професионално направление: 4.3.Биологически науки: Молекулярна генетика
Ключови думи
афективни разстройства - генетика; Кандидат-гени; Генотипизиране , Affective disorders--genetics; Candidate-genes; Genotyping