title: Modification of survival rate of mouse embryos developing in heterozygous females for ovum mutant gene.
abstract: The DDK syndrome (polar infertility) is caused by an incompatibility system due to the ovum mutant (Om) locus. For brevity, the following gene symbols are used in the present report: DDK allele, Om; C57BL/6Cr allele, +. In this investigation, we first attempted to introduce the Om allele of DDK strain into the genetic background of C57BL/6Cr strain. The attempt resulted in the production of no young at the third generation of successive backcrosses. Secondly, mating experiments were performed with heterozygous (Om/+) females having background genes of C57BL/6Cr and DDK strains in the ratios 1:1(B1D), 3:1(B3D), 7:1(B7D), and 15:1(B15D). The survival rate of the embryos as judged by the percentage number of live fetuses/number of corpora lutea at Day 12 of pregnancy was 41.3 +/- 3.2%, 27.3 +/- 3. 2%, 16.4 +/- 3.3%, and 11.3 +/- 3.2% (mean +/- SEM) in the B1D, B3D, B7D, and B15D females, respectively, when they were mated with C57BL/6Cr males. Furthermore, the increased embryonic mortality in the heterozygous (Om/+) females with more background genes of C57BL/6Cr strain was found to be due to a failure in blastocyst formation, as in the DDK syndrome. The parallelism between the proportion of C57BL/6Cr background genes and embryonic mortality has led to a hypothesis proposing the participation of a modifier gene, namely that a mechanism similar to allelic exclusion may be working in the synthesis of cytoplasmic factor of eggs and that only the Om allele is activated during oogenesis to produce DDK-type cytoplasmic factor in heterozygous (Om/+) females having a modifier gene in the homozygous state.
authors.affiliation: Laboratory of Animal Reproduction, Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa, Nagoya, Aichi, 464-8601, Japan.
authors.forename: W D
authors.initials: WD
authors.lastname: Zhao
authors.forename: H J
authors.initials: HJ
authors.lastname: Chung
authors.forename: N
authors.initials: N
authors.lastname: Wakasugi
mesh_terms: D000483:Alleles; D000818:Animals; D001757:Blastomeres / Q000502:physiology; D003433:Crosses, Genetic; D005314:Embryonic and Fetal Development / Q000235:genetics*; D005260:Female; D006579:Heterozygote; D007247:Infertility, Female / Q000235:genetics* / Q000503:physiopathology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008815:Mice, Inbred Strains; D009154:Mutation / Q000235:genetics*; D010063:Ovum / Q000502:physiology*; D011247:Pregnancy; D012098:Reproduction / Q000235:genetics; D013534:Survival