Characterizing the Spatial Distribution of Dendritic RNA at Single Molecule Resolution

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    eLife Assessment

    This useful study combines multiplexed RNA-FISH with downstream analyses and modelling to describe novel dendritic mRNA distribution and behavioural features. Although the downstream analysis pipeline is novel, the results from this study are as of yet incomplete. Further inclusion of key missing controls, further work to better assess the physiological relevance, or additional modelling to expand their conclusions would make this work of greater interest to RNA biologists.

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Abstract

Neurons possess highly polarized morphology that require intricate molecular organization, partly facilitated by RNA localization. By localizing specific mRNA, neurons can modulate synaptic features through local translation and subsequent modification of protein concentrations in response to stimuli. The resulting activity-dependent modifications are essential for synaptic plasticity, and consequently, fundamental for learning and memory. Consequently, high-resolution characterization of the spatial distribution of dendritic transcripts and the spatial relationship across transcripts is critical for understanding the pathways and mechanisms underlying synaptic plasticity. In this study, we characterize the spatial distribution of six previously uncharacterized genes ( Adap2 , Colec12 , Dtx3L , Kif5c , Nsmf , Pde2a ) within the dendrites at a sub-micrometer scale, using single-molecule fluorescence in situ hybridization (smFISH). We found that spatial distributions of dendritically localized mRNA depended on both dendrite morphology and gene identity that cannot be recreated by diffusion alone, suggesting involvement of active mechanisms. Furthermore, our analysis reveals that dendritically localized mRNAs are likely co-transported and organized into clusters at larger spatial scales, indicating a more complex organization of mRNA within dendrites.

Article activity feed

  1. eLife Assessment

    This useful study combines multiplexed RNA-FISH with downstream analyses and modelling to describe novel dendritic mRNA distribution and behavioural features. Although the downstream analysis pipeline is novel, the results from this study are as of yet incomplete. Further inclusion of key missing controls, further work to better assess the physiological relevance, or additional modelling to expand their conclusions would make this work of greater interest to RNA biologists.

  2. Reviewer #1 (Public review):

    Summary:

    Characterizing the molecular and spatial organization of dendritically localized RNAs is an important endeavor as the authors nicely articulate in their abstract and introduction. In particular, identifying patterns of mRNA distribution and colocalization between groups of RNAs could characterize new mechanisms of transport and/or reveal new functional relationships between RNAs. However, it's not clear to me how much the current study addresses those gaps in knowledge. The manuscript by Kim et al uses 8 overlapping combinations of 3-color fluorescence in situ hybridization to characterize the spatial distributions and pairwise colocalizations of six previously uncharacterized dendritically localized RNAs in cultured neurons (15 DIV). The strength of the work is in the graph-based analyses of …

  3. Reviewer #2 (Public review):

    In the manuscript by Kim et al titled, "Characterizing the Spatial Distribution of Dendritic RNA at Single Molecule Resolution," the authors perform multiplex single-molecule FISH in cultured neurons, along with analysis and modeling, to show the spatial features, including differing mRNA densities between soma and dendrites, dendritic length-related distributions and clustering, of multiple mRNAs in dendrites. Although the clustering analyses and modeling are intriguing and offer previously underappreciated spatial association within and across mRNA molecules, the data is difficult to interpret and the conclusions lack novelty in their current form. There is a need for a stronger rationale as to why the methodology employed in the manuscript is better suited to characterize the clustering of mRNA in …

  4. Reviewer #3 (Public review):

    Summary:

    The paper by Kim et al utilizes smFISH method to probe for six genes to understand the spatial distribution of the mRNAs in dendrites and identify the spatial relationships between the transcripts. While they have delved into a high-resolution characterization of the dendritic transcripts and compared their data with existing datasets, the analysis needs more robustness, and therefore the findings are inconclusive. The rationale of the study and choosing these genes is not clear - it appears more like a validation of some of the datasets without much biological significance.

    Overall, several conclusions for spatial distribution of dendritic RNAs were based on correlations and it is difficult to understand whether this represents a true biological phenomenon or if it is an artifact of the imaging and …