A new study indicates an essential role for a maternally inherited gene in embryonic development. The study found that zebrafish that failed to inherit specific genetic instructions from Mom developed fatal defects earlier in development, even if the fish could make their own version of the gene. When female animals form egg cells inside their ovaries, they deposit messenger RNAs (mRNAs) -- a sort of genetic instruction set -- in the egg cell cytoplasm. After fertilization, these maternally supplied mRNAs can be translated into proteins required for the early stages of embryonic development, before the embryo is able to produce mRNAs and proteins of its own. In the study, researchers used CRISPR/Cas9 gene editing to remove Vg1, known as Gdf3 in zebrafish. Embryos that couldn't produce any Gdf3 of their own -- but received a healthy portion of the gdf3 mRNA from their mothers–developed perfectly normally. But embryos that didn't receive maternal gdf3 mRNA showed major defects early on in their development, dying just three days after fertilization.
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