title: Factors affecting cellular mosaicism in the expression of a lacZ transgene in two-cell stage mouse embryos.
abstract: In the present study, we have analysed the expression pattern of a lacZ transgene (CMZ12) in preimplantation stage mouse embryos. The transgene is expressed at the two-cell stage, where it shows cellular mosaicism due to variable expressivity. The variable gene expression indicates a partial penetrance of the transgene. The extent of variation in expression is influenced by the genetic background of the oocyte. DBA/2 and CFLP genetic backgrounds promote high expression of the transgene, while Balb/c, C57BL/6, DDK, and F1 (C57BL/6 x CBA) genetic backgrounds give none or very little lacZ activity. In vitro culture of one-cell embryos to the two-cell stage induces the expression of lacZ in all strain backgrounds tested. The variation in CMZ12 expression is a transient phenomenon and does not affect later stage activity of the transgene. Nuclear transfer experiments and DNA methylation analysis suggests that a heritable modification of the transgene locus has not occurred.
authors.affiliation: Institut du cancer de Montréal, Qué., Canada.
authors.forename: R K
authors.initials: RK
authors.lastname: Kothary
authors.forename: N D
authors.initials: ND
authors.lastname: Allen
authors.forename: S C
authors.initials: SC
authors.lastname: Barton
authors.forename: M L
authors.initials: ML
authors.lastname: Norris
authors.forename: M A
authors.initials: MA
authors.lastname: Surani
mesh_terms: D000818:Animals; D002970:Cleavage Stage, Ovum / Q000378:metabolism*; D004247:DNA / Q000032:analysis; D005260:Female; D015971:Gene Expression Regulation, Enzymologic; D008297:Male; D008745:Methylation; D051379:Mice; D008815:Mice, Inbred Strains; D008822:Mice, Transgenic; D009030:Mosaicism / Q000235:genetics*; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D013045:Species Specificity; D001616:beta-Galactosidase / Q000096:biosynthesis*
chemical_list: D011993:Recombinant Fusion Proteins; D004247:DNA; D001616:beta-Galactosidase