| Complex diseases are conditions that are influenced by the actions of multiple genes, their interactions with each other and with the environment. The prevalence of complex diseases is higher than 1% in general population, hence also called common diseases, such as schizophrenia, age-related macular degeneration, diabetes, asthmas, cardiovascular disease, et al. Since we know little about them and lack of effective treatments, more and more scientists participate in research on pathology and etiology of these complex diseases. The main work of my thesis is about linkage disequilibrium study on susceptible genes of schizophrenia and age-related macular degeneration in Chinese population.Schizophrenia (MIM 181500) is a common severe mental illness that affects 1% of the population worldwide. Data from twin, family, and adoption studies provide strong evidence that genetic factors play a major role in schizophrenia. Though its etiology remains unknown, it is well known that schizophrenia is a kind of complex disease.N-methyl-D-aspartate (NMDA) receptors have been proposed as mediators in glutamate hypothesis of schizophrenia. NO mainly catalyzed by NOS1 is the second messenger of NMDA and plays a vital role in nervous system, immune system and cardiovascular system. NOS1 is located in 12q22-24, a linkage location that has been linked to many neuropsychiatric phenotypes. We chose 11 variants including a microsatellite in NOS1 gene and genotyped 1705 case-control samples in our Han Chinese population by directly sequencing. Among these markers, rs3782206 revealed significant association with schizophrenia in our samples, even after corrected by 10000 permutations. And its haplotype with rs3837437 also showed the association with schizophrenia and S-P subtype. Our results supported NOS1 as a susceptible gene of schizophrenia and solidified the glutamate hypothesis.DISC1 gene is disrupted by the chromosome 1 breakpoint of a balanced t (1;11) translocation that co-segregates with schizophrenia and related mood disorders in a large multi-generational Scottish pedigree. It is always the hottest candidate gene of schizophrenia. Recent research has elucidated that the DISC1 binding partners, such as ATF4, PDE4B, NDEL1, LIS1 and FEZ1, and how they interact with DISC1 to effect the neuronal migration, cytoskeletal location and neuronal signaling. The biochemical evidence supports the hypothesis of neurodevelopment of schizophrenia and provides the convincing explanation for deficit cognition performance. We selected 16 SNPs covering the whole genomic DNA of DISC1 and genotyped in 576 case-control samples by TaqMan method. Our results found that rs1322784, rs7514199, rs2738864, rs1000731 and rs16841582 showed significant deviation of allelic distribution between case and control. Furthermore, the core haplotype of rs1322784, rs7514199 and rs2738864 was associated with schizophrenia as well. Meanwhile, we conducted RT-PCR to measure the expression of DISC1 and its binding molecular on peripheral blood mononuclear cell. We found a high correlation between them, particularly the expression of NDEL1 and PDE4B which was increased in case compared to the control. Logistic multiple regression model including NDEL1 and DISC1 made 73.74% contribution to diagnosis the status of disease. Our results provided further evidence for DISC1 as the important gene in the etiology of schizophrenia in Han Chinese population.Age-related macular degeneration (AMD, MIM 153800) is an age-associated progressive disease affecting the central regions of the retina and choroid, which can lead to loss of central vision. The whole genome linkage and association studies have identified two convincing genes, CFH and ARMS2 in the etiology of AMD currently.We performed an association study on our 192 case-control Han Chinese AMD samples. As for Y402H in CFH, we did not get the significant signal in Y402H as in Caucasian. Instead, we found many other mutations as rs800292, rs2274700, rs3753396, rs1329428 and rs1065489 showing positive result in our samples (P<0.05, OR>1.5). As for ARMS2, we gained the consistent result and P value of A69S reached to 1.55×10-7 when we stratified samples into wet type of AMD. We evaluated the role of epistasis among these positive mutations in two genes; we observed no statistically significant non-additive interactions, which suggested these loci independently contributed to the disease. Our results provided a further support for CFH and ARMS2 as the susceptible genes to AMD in Han Chinese population.Another part of my work was about the ENU (ethylnitrosourea) mutagenesis mouse model. ENU is a synthetic compound described as the most potent mutagen in mice. Large-scale ENU mutagenesis program has provided us with a large number of new mouse mutants applied for the analysis of gene function and further for good models of some human diseases. We screened circling phenotype mice by ENU mutagenesis, mapping the related gene in chromosome 4 and sequenced a novel mutant in exon13 of mouse Chd7 gene. This novel mutant resulted in functional change from arginine to premature stop codon. It has been reported that human CHD7 gene was linked to autosome dominant disease CHARGE syndrome. On the basis of the overlap in clinical features between Chd7 mutant mice and CHARGE, we believe that these mice will be a valuable tool in further analysis of the pathology underlying the abnormalities in CHARGE syndrome. |
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