2002 Fiscal Year Final Research Report Summary
ANALYSIS OF CYCLIC CHANGES OF X CHROMOSOME ACTIVITY IN MOUSE DEVELOPMENT
| Project/Area Number |
13440223
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (B)
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Field |
遺伝
|
|---|
| Research Institution | HOKKAIDO UNIVERSITY |
|---|
Principal Investigator |
TAKAGI Nobuo Hokkaido Univ., Grad. Sch. Environ. Earth Sci., Prof., 大学院・地球環境科学研究科, 教授 (20001852)
|
|---|
| Project Period (FY) |
2001 – 2002
|
| Keywords | Mouse / Early development / X-inactivation / Dosage compensation / Xist gene / FISH / GFP / ES cells |
|---|
| Research Abstract |
Only the morphologically normal X chromosome is inactivated in female mice heterozygous for Searle's X-autosome translocation. We performed a visual study of the primary and secondary events that culminate in the cmpletely non-random inactivation in female embryos having his translocation. The data we have obtained so far indicate that the initial choice of the future inactive X chromosome is biased: the degree of skewing is somewhere between 70 : 30% and 90 : 10% in favor of the morphologically normal X chromosome. The majority of genetically unbalanced cells that inactivate a translocated X chromosome are quickly eliminated from the embryo by proper E8.5.
Applying RNA fluorescence in situ hybridization to parthenogenetic embryos with two maternally derived X (Xm) chromosomes and embryos with X chromosome aneuploidy such as Xp0 (Xp, paternally derived X chromosome), XmXmXp and XmXmY, we studied the control of Xist. Tsix expression for silencing the X chromosome in mice. The data show t
… More
hat the paternally derived Xist allele is highly expressed in every cell of the embryo from the 4-cell stage onward, irrespective of the number of X chromosomes in a diploid cell. The high level of Xist transcription is maintained in non-epiblast cells culminating in Xp-inactivation, whereas in Xp0 embryos it is terminated by the blastocyst stage, probably as a result of counting the number of X chromosomes in a cell occurring at the morula/blastocyst stage. Xist is also down-regulated in epiblast cells of XmXp and XmXmXp embroys to make X-inactivation random.
Three female ES cell lines carrying X-linked GFP and lacZ transgenes in cis were established for visual study of X-inactivation in vitro. X-inactivation assessed by extinction of GFP fluorescence and expression of β-galactosidase appeared normal in differentiating embryoid bodies. However, loss of GFP fluorescence does not coincide with the lack of β-galactosidase activity in a considerable proportion of apparently differentiated cells in response to retinoic acid treatment. It is likely that X-inactivation does not occur normally in such cells. Less
|
