In the first part of this thesis, two chromosome Y specific genes ( SRYand TSPY) were chosen as the molecular targets to investigate the characteristics of fetal-specific DNA fragments in maternal plasma. By employing the touch down ligation-mediated PCR coupled with cloning and sequencing, the end property and the fragment species of fetal DNA were studied. / Noninvasive prenatal detection of fetal chromosomal aneuploidies is a much sought-after goal in fetomaternal medicine. The discovery of fetal DNA in the plasma of pregnant women has offered new opportunities for this purpose. However, the fact that fetal DNA amounts to just a minor fraction of all DNA in maternal plasma makes it challenging for locus-specific DNA assays to detect the small increase in sequences derived from a trisomic chromosome. On the other hand, although the clinical applications of plasma DNA for prenatal diagnosis are expanding rapidly, the biological properties of circulating DNA in plasma remain unclear. Recently, next-generation sequencing technologies have transformed the landscape of biomedical research through the ultra-high-throughput sequence information generated in a single run. Massively parallel sequencing allows us to study plasma DNA at an unprecedented resolution and also precisely detect fetal chromosomal aneuploidies in a locus-independent way. / Our group has demonstrated the use of massively parallel sequencing to quantify maternal plasma DNA sequences for the noninvasive prenatal detection of fetal trisomy 21. In the second part of this thesis, the clinical utility of this new sequencing approach was extended to the prenatal detection of fetal trisomy 18 and 13. A region-selection method was developed to minimize the effects of GC content on the diagnostic sensitivity and precision for the prenatal diagnosis of trisomy 13. To facilitate the next-generation sequencing-based maternal plasma DNA analysis for clinical implementation, two measures, i.e., lowering the starting volume of maternal plasma and barcoding multiple maternal plasma samples, were investigated. / Taken together, the results presented in this thesis have demonstrated the clinical utility of massively parallel sequencing of maternal plasma DNA and have also provided us a better understanding of the biology of circulating DNA molecules. / The third part of this thesis focuses on the massively parallel paired-end sequencing of plasma DNA. By analyzing millions of sequenced DNA fragments, the biological properties of maternal plasma DNA were elucidated, such as the size distribution of fetal-derived and maternally-contributed DNA molecules and the potential effect of epigenetic modification on DNA fragmentation. Moreover, the plasma DNA from hematopoietic stem cell transplant patients was characterized by paired-end sequencing approach. These sequencing data not only confirmed the predominant hematopoietic origin of cell-free DNA but also revealed the size difference between hematologically-derived and other tissue-derived DNA molecules in plasma. / Zheng, Wenli. / Adviser: Lo Yu Ming Dennis. / Source: Dissertation Abstracts International, Volume: 73-03, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 261-275). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.
| Identifer | oai:union.ndltd.org:cuhk.edu.hk/oai:cuhk-dr:cuhk_344944 |
| Date | January 2010 |
| Contributors | Zheng, Wenli., Chinese University of Hong Kong Graduate School. Division of Chemical Pathology. |
| Source Sets | The Chinese University of Hong Kong |
| Language | English, Chinese |
| Detected Language | English |
| Type | Text, theses |
| Format | electronic resource, microform, microfiche, 1 online resource (xx, 275 leaves : ill. (some col.)) |
| Rights | Use of this resource is governed by the terms and conditions of the Creative Commons “Attribution-NonCommercial-NoDerivatives 4.0 International” License (http://creativecommons.org/licenses/by-nc-nd/4.0/) |
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