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XIST expression in human oocytes and preimplantation embryos
R Daniels1, M Zuccotti, T Kinis
1Molecular Embryology Unit, Institute of Child Health, London, United Kingdom.
American Journal of Human Genetics
|July 1, 1997
Summary
Early XIST gene expression in human embryos differs from mice, occurring in both sexes from the zygote stage. This pattern challenges the role of early XIST expression in paternal X inactivation in human extraembryonic lineages.
Area of Science:
- Developmental Biology
- Genetics
- Reproductive Science
Background:
- Paternally inherited X chromosome inactivation is crucial in female mammalian development, particularly in extraembryonic tissues.
- The Xist gene is known to initiate X chromosome inactivation in mice, with paternal allele expression being key.
- Recent findings suggest paternal X chromosome inactivation also occurs in human extraembryonic lineages.
Purpose of the Study:
- To investigate the pattern of XIST gene expression in human preimplantation embryos.
- To determine if XIST expression correlates with paternal X inactivation in humans, similar to mice.
- To analyze XIST and HPRT expression and sexing simultaneously at the single-cell level.
Main Methods:
- Development of sensitive single-cell procedures for simultaneous XIST and HPRT expression analysis and sexing.
- Initial validation of methods using human fibroblast cells.
- Application of these techniques to human cleavage-stage embryos generated via in vitro fertilization.
Main Results:
- XIST gene transcripts were detected as early as the 1-cell zygote stage in human embryos.
- XIST expression increased in efficiency through to the 8-cell stage.
- Transcripts were found in both male and female preimplantation embryos, indicating maternal allele expression in males.
Conclusions:
- The observed pattern of XIST expression in human preimplantation embryos differs significantly from that in mice.
- Early XIST expression in human embryos is not restricted to the paternal allele or specific to females.
- This expression pattern is inconsistent with a role for early XIST expression in the choice of paternal X inactivation in human extraembryonic lineages.