By Levi Clancy for Student Reader on
The oocyte prepares massive quantities of mRNA by performing intensely synthesizing mRNA for a long period of time (even months) and by creating a more stable mRNA environment than in somatic cells.
Maternal mRNA Importance
|Enucleation||An urchin blastomere underwent centrifugal enucleation, forming one nucleated and one enucleated blastomere.|
|Development||Enucleated blastomere gets to blastula stage before arresting. Nucleated blastomere develops normally.|
|Other Species||Same outcome via centrifugal or chemical enucleation in many other organisms (except mammals).|
|Conclusions||Embryonic transcription is not needed until the blastula stage in many species (except mammals). However, translation is necessary since puromycin (a translation inhibitor) stops development before the first cleavage.|
Control of maternal mRNAs?
|Localization||Example: bicoid mRNA in the Drosophila embryo. The mRNA is bound to the cytoskeleton, primarily microtubles (proven by treating with certain microtubule-inhibiting chemicals). Specific gene products are required for localization. The mRNAs and proteins are transported along microtubules.|
|Translation||How is translation of specific mRNAs and of total mRNA controlled? Example: bcd mRNA translation is activated at fertilization. Specific proteins bind its 3' UTR and repress translation until fertilization.|