Study Of5-hydroxymethylcytosine And Histone Methylation In Association Of Human Diseases

Although the etiologies and pathogeneses of most human diseases are extremely complex and largely unknown, a plethora of studies have revealed that epigenetic mechanisms play essential roles in many human diseases. Recently a newly identified DNA modification5-hydroxymethylcytosine (5hmC) has been found abundantly present in mammalian genome in a tissue-specific manner. However little is known about its functions and association with most of human diseases. In this thesis, we took molecular, biochemical and genomic approaches in order to uncover the underlying epigenetic mechanisms of5hmC and histone methylation in human diseases such as lung adenocarcinoma and male infertility:Lung adenocarcinoma is the most common type of lung cancer, which is the leading cause of cancer death among the world. We found that the global level of5hmC in lung adenocarcinoma is decreased substantially compared with matched normal lung tissue. Furthermore, we profiled the genomic location of5hmC in one patient and characterized its distribution pattern in lung adenocarcinoma by a chemical labeling and biotin enrichment method. Importantly, we found the "5hmC lost regions" in lung adenocarcinoma is involved in various cancer pathways and cancer related pathways, which strongly suggested that deletion of5hmC is a hallmark of lung adenocarcinoma. In addition, we profiled histone methylations in lung adenocarcinoma, including H3K4me1, H3K9me1, H4K20me1, H4K20me2and H4K20me3. Together, these histone methylations and5hmC maps provide comprehensive epigenetic landscapes in regulating lung adenocarcinoma, which may further cast light on the diagnosis and treatment of lung cancer.Infertility is a major human disease following cancer and cardiovascular disease in the21st century. It has been estimated that approximately one in six young couples suffer from infertility, whereas up to50%of all cases result from male infertility. We separated normal, abnormal sperms from a healthy man and globozoospermia sperms form a globozoospermia patient and performed genomic-scale profiling of5hmC in these samples. We characterized5hmC distribution in sperm and found5hmC is preferentially present in introns. We also demonstrated that5hmC containing genes involve in various pathways important for sperm functions. What’s more, we correlated our data with imprinted genes and found40%imprinted genes contain5hmC in sperms. The abnormal sperm has the largest number of imprinted genes; on the contrary, nearly50%imprinted genes in globozoospermia lose their5hmC marks. Our findings therefore suggest5hmC may have fundamental roles in sperm function and male infertility, and hence open new avenues for investigating epigenetic regulation in spermatogenesis and male infertility.