Mouse ζ- and α-Globin Genes: Embryonic Survival, α-Thalassemia, and Genetic Background Effects

Abstract

A classical notion regarding the expression of murine embryonic ζ- and adult α-globin genes holds that there is a switch in globin production from the embryonic to the adult form during fetal development. Our previous in situ hybridization studies challenged this view, since both ζ- and α-globin mRNAs can be detected simultaneously in the earliest erythrocyte populations. This finding raises the possibility that ζ-globin production might be wholly or partially redundant in embryos in which the adult α-globin is also expressed. To test this possibility, we created a null mutation of the ζ-globin gene using homologous recombination in embryonic stem cells. Many outbred mice homozygous for the ζ-null mutation were able to develop normally, undermining the notion that there is an absolute need for ζ-globin and indicating that α-globin alone can serve the survival needs of the fetus. Interestingly, insertion of the PGK-Neo cassette (used to create the null mutation) into the ζ-globin gene appears to influence the expression of the nearby α-globin genes, giving rise to reduced α-globin production and to an α-thalassemia–like syndrome. There is also evidence indicating the strong influence of genetic background on the ζ-null and α1-null phenotypes, both of which are much more severe in the 129/SvEv inbred genetic background. These quantitative differences can potentially be exploited to identify genes important for erythropoiesis.

Engineering a humanized telomerase reverse transcriptase gene in mouse embryonic stem cells

“…Knock-in experiments were performed by cotransfection of the targeting BAC and two pX458-sgRNAs (targeting the 5′ intergenic region and intron 6 of the mTert locus) into Tc1 cells 29 (Fig. 3A).…”

Chromatin interaction mechanism of transcriptional control invivo

“…There is indirect evidence for competition in the mouse α locus which may be indicative of an alternating transcriptional mechanism. Insertional mutation of the ζ gene with a PGK‐Neo cassette results in decreased expression of the α genes in definitive erythroid cells when ζ would normally be silenced (Leder et al ., 1997). Although the DRB results alone do not allow us to make firm conclusions regarding the mechanism of multiple α gene expression they do show a clear difference compared with the γ and β genes and exclude an artificial lag of reappearing double signals in cis as a consequence of the DRB treatment.…”

Tissue-specific CTCF–cohesin-mediated chromatin architecture delimits enhancer interactions and function in vivo

“…Panels show overlaid, normalised Capture-C data for the α-globin promoter (α1, α2) and the R1 enhancer viewpoints in mouse ES and primary erythroid cells merged from 3 independent experiments, in which 3 animals (erythroid cells) or 3 biologically independent samples (ES cells) were analysed in total. Each of the α-globin promoters interacts with the enhancers independently, resulting in the expression of both genes (α1, α2)17,43. The mean, plus and minus one standard deviation (S.D.…”