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Transient expression of a human β‐actin promoter/ lacZ gene introduced into mouse embryos correlates with a low degree of methylation
Author(s) -
Nilsson Erik,
Lendahl Urban
Publication year - 1993
Publication title -
molecular reproduction and development
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.745
H-Index - 105
eISSN - 1098-2795
pISSN - 1040-452X
DOI - 10.1002/mrd.1080340206
Subject(s) - biology , embryo , microbiology and biotechnology , transgene , blastocyst , gene , lac operon , gene expression , blastomere , genetically modified mouse , dna methylation , genetics , embryogenesis
We have analysed the correlation between expression and methylation for the human β‐actin promoter introduced into mouse embryos. The β‐actin promoter was fused to the reporter gene lacZ , and expression was analysed after pronuclear injection into fertilized mouse eggs. We analysed transient expression in in vitro cultured preimplantation embryos and expression after chromosomal integration in 5 independent lines of transgenic mice. The in vitro cultured preimplantation embryos expressed lacZ from the 2‐cell to the blastocyst stages, and most abundantly at the morula stage. By increasing the amount of injected DNA, a larger proportion of embryos expressed lacZ . Embryos expressing lacZ in only a subset of the blastomeres were detected at all preimplantation stages. In contrast to the transient expression after injection, we have not detected lacZ expression in any of the 5 analysed lines of transgenic mice carrying the same construct. The lack of expression in transgenic mice correlates with hypermethylation of C residues in the vast majority of CG sequences in the integrated β‐actin/ lacZ construct, whereas the injected construct was completely nonmethylated. We discuss methylation and other possible reasons for the observed differences in expression between injected and integrated copies of the β‐actin/ lacZ construct and for lacZ expression in only a subset of blastomeres in preimplantation embryos. © 1993 Wiley‐Liss, Inc.