[Change of the chromosome conformation of human alpha-globin gene locus in transgenic mice].

OBJECTIVE

To establish chromosome conformation capture (3C) strategy and to use this method for exploring the effect of chromosome conformation on human alpha-globin gene expression in the human alpha-globin transgenic mouse.

METHODS

Homozygous human alpha-globin transgenic male mouse was crossed with KM female mouse. The 14.5-day post-coitum (dpc) embryos were used for the isolation of fetal liver and fetal brain cells. Homogeneous single-cell suspension was treated with formaldehyde to crosslink the chromatin conformation in the nuclear. The cross-linked chromatin compound was digested with Nco I and then ligated with T4 DNA ligase. The ligated compound was reversely cross-linked and then the ligated genomic DNA was purified for PCR analysis. The primers were designed along the two sides of cut and ligated sites. Semi-quantitative PCR was used to analyze the chromosome conformation of the whole human alpha-globin gene locus in fetal liver and fetal brain cells.

RESULTS

When HS40 fragment was used as the fixed fragment, in fetal brain cells, the ligation frequencies of HS40 fragment with other fragments were decreased as the linear distances to HS40 fragment were increasing; while in fetal liver cells, two active genes (alpha1 and alpha2) fragments showed higher ligation frequencies with HS40 fragment than other fragments. However, the fragment containing an inactive gene (xi) displayed the comparable low ligation frequency as that in fetal brain. When alpha2 fragment was used as the fixed fragment, similarly, in fetal brain cells the ligation frequencies of alpha2 fragment with other ones were decreased as the linear distances increasing; when in fetal liver cells, it showed higher ligation frequencies with two upstream regulatory elements (HS 40 and 33). However, it showed a little bit lower ligation frequency with another two upstream regulatory elements (HS10 and 8) than those in fetal brain.

CONCLUSION

In fetal liver cells, the distant regulatory elements are in close proximity to the downstream of the expressed globin genes through looping out, the interval region; however, in fetal brain, they were not in vicinity to the expressed globin genes.