A maternal genetic effect on the composition of mouse aggregation chimaeras

Publisher Website
Google Scholar
Abstract
Two series of 12½ day mouse chimaeric conceptuses were produced by aggregating (C57BL × CBA)F2 strain preimplantation embryos with embryos that differed at the Gpi-1s locus that encodes glucose phosphate isomerase, GPI-1. The composition of individual issues was evaluated by quantitative electrophoresis to estimate the % GPI-1A in the chimaeric tissue containing GPI-1A and GPI-1B. In one series of chimaeras, the GPI-1A cells were derived from a backcross between inbred BALB/c strain females and (BC × BALB/c)F1 males, where BC is the partly congenic strain C57BL/Ola.AKR-Gpi-lsa,c/Ws. In the other series of chimaeras, the GPI-1A cells were derived from the reciprocal backcross between (BC × BALB/c)F1 females and inbred BALB/c strain males. The [(BC × BALB/c)F1 female × BALB/c male] ↔ (C57BL × CBA)F2 series of chimaeras was reasonably balanced so that GPI-1 A and GPI-1B cells were fairly equally represented in the foetuses, placentas and extraembryonic membranes (tissue means: 37–51 % GPI-1A). This series did not differ significantly in composition from an earlier series of (BC × BALB/c)F2 ↔ (C57BL × CBA)F2 chimaeras. However, the [BALB/c female × (BC × BALB/c)F1 male] ↔ (C57BL × CBA)F2 series of chimaeras was unbalanced, with mean tissue compositions (28–33% GPI-1A) that were intermediate between the above two balanced series and the unbalanced (BALB/c × BALB/c) ↔ (C57BL × CBA)F2 series (tissue means: 14–22% GPI-1 A), that was studied previously. Thus, both (BALB/c×BALB/c) and [BALB/c×(BC x BALB/c)F1 embryos contributed less to the tissues of chimaeric conceptuses than either (BC × BALB/c)F2or [(BC × BALB/c)F1 × BALB/c] embryos. This implies that embryos from BALB/c mothers contributed less to the tissues of chimaeric conceptuses than embryos from (BC × BALB/c)F1 mothers. We, therefore, conclude that a maternal genetic effect is responsible for some of the differences in composition among the four groups of chimaeras. This maternal effect must act before the 8-cell stage but it is not yet known whether it is mediated via cytoplasmic inheritance, genomic imprinting or by the reproductive tract. Evidence that a maternal effect retards preimplantation development of embryos from BALB/c females is reviewed and the possibility that this might cause them to contribute poorly to chimaeric conceptuses when aggregated with more precociously developing embryos is discussed.