Neurl4Δ1 mutants display a dominant misshapen primordial germ cells (PGC) in well over half of the embryos from heterozygous mothers. The frequency of PGC defects is similar in progeny embryos of Neurl4Δ1/+ females crossed with either Neurl4Δ1 or wild-type males, demonstrating that the PGC phenotype is independent of zygotic genotype. Embryos from wild-type females crossed to homozygous Neurl4Δ1 males do not shot the PGC phenotype.
Embryos from Neurl4Δ1 mutant mothers show multiple PGC defects at stage 10 during migration: the protrusion on PGCs are often smaller than normal; there are displaced vesicles just as seen in stage 5 embryos; and some PGCs are elongated relative to those in wild-type embryos.
Neither wild-type nor Neurl4Δ1/+ mutant stage 5 embryos PGCs are positive for a marker of apoptosis.
Homozygous or hemizygous mutants are viable and appear healthy. However, a fraction of the progeny of Neurl4Δ1 mutant mothers are agametic and thus infertile. Examination of embryos from Neurl4Δ1 mutant mothers reveals that, in addition to the abnormal PGC morphology, the number of PGCs is reduced compared with wild-type.