Phenotypic Analysis of Periimplantation to Mid-Gestation Lethality in Mice

Periimplantation to mid-gestation lethality is indicated if no living homozygous mutants are recovered at E12.5 and the number of empty implantation sites or degenerating/abnormal embryos fits the expected number of homozygous mutants. To determine the time of death, this overview details the characteristic features of lethality shortly after implantation (E4.5-E5.5) or lethality between gastrulation and allantoic fusion (E6.5-E9.5). Determining the phenotype of the mutants involves making a gross morphological assessment, staging the embryos, and photodocumenting any abnormalities. Further levels of analysis discussed are histological assessment, molecular characterization of gene expression in the mutant embryos, and measurements of cell proliferation and cell death.