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| Author(s): |
Joana Carvalho Moreira de Mello
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Instituto de Biociências (IBIOC/SB) |
| Defense date: | 2010-04-08 |
| Examining board members: |
Lygia da Veiga Pereira Carramaschi;
Miriam Galvonas Jasiulionis;
Angela Maria Vianna Morgante
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| Advisor: | Lygia da Veiga Pereira Carramaschi |
| Abstract | |
Imprinted inactivation of the paternal X chromosome in marsupials is the primordial mechanism of dosage compensation for X-linked genes between females and males in Therians. In Eutherian mammals, X chromosome inactivation (XCI) evolved into a random process in cells from the embryo proper, where either the maternal or paternal X can be inactivated. However, species like mouse and bovine maintained imprinted XCI exclusively in extraembryonic tissues. The existence of imprinted XCI in humans remains controversial, with studies based on the analyses of only one or two X-linked genes in different extraembryonic tissues. Here we readdress this issue in human term placenta by performing a robust analysis of allele-specific expression of 23 X-linked genes, including XIST, using 28 SNPs in transcribed regions. We show that XCI is random in human placenta, and that this organ is arranged in relatively large patches of cells with either maternal or paternal inactive X. In addition, this chromosome-wide analysis indicated heterogeneous maintenance of the epigenetic state along the inactive X, which combined with the extensive mosaicism found in placenta, can explain the lack of agreement among previous studies. Our results illustrate the differences of XCI mechanism between humans and mice, and highlight the importance of addressing the issue of imprinted XCI in other species in order to understand the evolution of dosage compensation in placental mammals (AU) | |
| FAPESP's process: | 06/05382-5 - X-chromosome inactivation pattern in human extra-embryonic tissue |
| Grantee: | Joana Carvalho Moreira de Mello |
| Support Opportunities: | Scholarships in Brazil - Master |