mRNA transport is an integral step in gene regulatory control. Understanding this process in the context of development is essential to determine how spatially regulated protein production impacts cell differentiation. Post-transcriptional control is especially important in embryos when de novo transcription is paused. We have identified maternal mRNAs with cell-specific and subcellular patterning in the early embryos of Caenorhabditis elegans. In particular,
erm-1 (Ezrin/Radixin/Moesin) mRNA is asymmetrically enriched in anterior blastomeres and localizes to the cell cortex where the ERM-1 protein is also enriched. ERM-1 is a membrane-actin linker essential for apical membrane morphogenesis and is critical for intestine and excretory canal formation and function. How
erm-1 mRNA arrives at the cell cortex and how mRNA localization interplays with translation regulation remain unclear. Broadly, mRNA can localize subcellularly in either translation-independent or dependent manners. In the translation-independent model, localization is driven by an mRNA sequence feature often found within the 3'UTR. In the translation-dependent model, a peptide signal or domain within the protein directs transport. Prior studies from our lab have demonstrated the 3'UTR of
erm-1 is not sufficient for mRNA localization. Here, recoding the nucleotide sequence of
erm-1 while preserving its amino acid sequence did not alter
erm-1 mRNA cortical localization suggesting the information directing
erm-1 mRNA localization resides in the protein. Further, we employed multiple methods of translation inhibition, through small molecule inhibitors, heat stress, or genetic depletion of translational machinery. By all three measures, localization of
erm-1 mRNA was impaired upon translational disruption illustrating that
erm-1 mRNA localization is translation-dependent. ERM-1 contains an N-terminal PIP2-binding FERM domain important for ERM-1 protein function. To test whether FERM domain containing transcripts generally to the cell cortex in the early embryo, we computationally identified 14 early embryonic genes containing FERM or a similar domain and we are assessing their mRNA localization patterns. The first transcript screened,
frm-7, does indeed have cortical localization. Future studies will seek to identify cytoskeletal and motor dependencies of ERM-1 localization, whether ERM-1 translation is paused during transport, and whether future rounds of translation occur at the cortex.