Front–back mRNA distribution in Stentor cells: MYB suppression reveals defects in posterior regeneration
Background: How does a single cell distinguish front from back?
A study published in PNAS reports that messenger RNA (mRNA) is distributed differently between the front and back of the giant single-celled organism Stentor coeruleus. Suppressing some MYB genes whose mRNAs are enriched at the rear caused defects in posterior structure regeneration. Suppressing the expression of microtubule component proteins or the cytoplasmic dynein intermediate chain also disrupted the front–back distribution of multiple mRNAs.
About 1 mm long, Stentor has a band of cilia at its front and an attachment structure at its rear. Even when cut in half, each half can regenerate the part it has lost. The consistent positioning of these structures suggests that positional information exists inside the cell, but the molecular principles that convey it are not well understood. Drawing on findings from embryonic development linking mRNAs concentrated in specific regions with positional information, the researchers investigated Stentor’s front–back axis.
Key findings: Comparing anterior and posterior RNA and testing regeneration by gene suppression
The researchers cut cells into anterior and posterior halves, pooled 50 anterior fragments and 50 posterior fragments separately for each sample, and performed bulk RNA sequencing (RNA-seq). At the exploratory threshold of q<0.2, they identified 6,276 genes with different degrees of anterior and posterior enrichment. The researchers estimated that, after accounting for a 20% false discovery rate, the number corresponds to about 15% of all gene models. Because the threshold was chosen to search broadly for candidates, the full list should not be interpreted as a set of confirmed positioning genes.
mRNAs enriched at the front tended to encode structural and metabolic proteins, while those enriched at the rear tended to encode proteins involved in signaling and regulation. Of 50 transcripts encoding proteins with an MYB DNA-binding domain that showed front–back enrichment differences, 40 were enriched at the rear.
The researchers used RNA interference (RNAi) to suppress two MYB genes corresponding to posterior-enriched transcripts, then cut the cells. At 24 hours after cutting, some anterior half-cells had failed to properly regenerate the tapering tail structure at the rear. In posterior half-cells that already had the rear structure, the frequency of the same defect was similar to that in controls. This supports the interpretation that the gene products are involved in forming new posterior structures. However, reduced gene expression alone does not establish that mRNA localization itself is essential for regeneration.
In experiments suppressing β-tubulin, a microtubule component, or the dynein intermediate chain, cell morphology and mRNA distribution both changed. Paired anterior and posterior halves from the same cell were compared by RNA-seq; the distribution differences of multiple transcripts narrowed or reversed. Under dynein-suppression condition G04, the researchers identified 403 candidates with significantly reversed distribution bias. Under G05, which targeted a different gene, the front–back distinction at the overall sample level became less clear, but no significant bias change was detected for individual transcripts. It remains unclear whether the difference between the two conditions reflects biological characteristics or technical effects.
Meaning and outlook: Candidates for positional information, but transport mechanisms remain unresolved
This study provides a basis for examining mRNA distribution within a single cell and testing the regenerative function of some candidate genes. The researchers proposed that motor proteins may transport mRNAs along microtubules. However, the experiments did not directly track mRNA movement, and dynein suppression may also have affected microtubule organization.
The idea that transcription at specific sites and motor-based transport together produce the distribution is also a model that still needs testing. Follow-up work should examine the roles of kinesins and RNA-binding adaptors, and the relationship between mRNA location and protein location. It will also be necessary to distinguish how the amount of a gene product and its placement within the cell each contribute to regeneration.
The methods and results are available in the full PNAS paper.
Proceedings of the National Academy of Sciences, Volume 123, Issue 25, June 2026. SignificanceJust as embryos develop into complex forms, single cells also form complicated structures, but much less is known about pattern formation in cells. We used a single-celled organism, Stentor, to ask how a cell forms different structures in ...
The most direct application of these findings is in basic research on cell morphogenesis and regeneration. Researchers can select candidates from the list of transcripts enriched at the front or rear, then combine RNAi, observations of mRNA localization, and protein distribution analysis to narrow down factors needed to form posterior structures. In particular, distinguishing experiments that reduce gene expression from those that alter mRNA localization can help determine whether a regeneration defect stems from a shortage of protein or is linked to changes in its placement within the cell. This study examined Stentor; it did not assess human regenerative therapies or the delivery or manufacturing performance of RNA therapeutics. Before considering clinical or industrial applications, researchers would first need to establish whether the same principle operates in other cells.