The authors created a CRISPR knock-in zebrafish line in which eGFP is fused to the C‑terminus of endogenous SNRNP70. The design retained the native 3′ untranslated region of the gene to preserve endogenous regulatory elements. This strategy was selected to enable direct visualisation of SNRNP70 at physiological expression levels and to avoid confounding effects associated with protein overexpression or transgenic reporters that do not include full native regulatory context.
The knock-in line was validated as a faithful reporter of endogenous SNRNP70 expression. The authors report that the SNRNP70-eGFP allele reflects physiological expression and localisation patterns, thereby providing confidence that observed localisation and dynamics reflect endogenous protein behaviour rather than artefacts from ectopic expression. The source does not provide further technical validation metrics or quantitative expression comparisons in the abstract; those specific details were not reported in the source text.
Using the validated knock-in, the study shows that endogenous SNRNP70 is widely localised throughout the developing zebrafish nervous system. The reporter reveals prominent enrichment of SNRNP70 within axonal and synaptic compartments in developing neurons. These observations extend the classical view of SNRNP70 as a core spliceosome RNA‑binding protein largely associated with nuclear pre‑mRNA splicing by demonstrating substantial extranuclear presence in neuronal processes under physiological expression conditions.
Crucially, live in vivo imaging of the knock-in zebrafish demonstrates that endogenous SNRNP70 is dynamically localised within neuronal mRNP granules. This provides direct evidence that under physiological expression levels, SNRNP70 participates in dynamic cytoplasmic ribonucleoprotein structures in neurons. Because the approach images the endogenous protein fused to eGFP, these dynamics are observed without the confounders introduced by overexpression or non‑native promoters.
Proximity ligation analyses performed in the study reveal associations between endogenous SNRNP70 and established neuronal mRNP granule proteins PABPC1B, FUS, and UPF1. These molecular associations support the imaging findings and link SNRNP70 to known components involved in mRNA regulation within neuronal granules. The source text reports these associations but does not list further biochemical details, binding affinities, or the precise cellular contexts of each interaction; such specifics were not reported in the source abstract.
The SNRNP70-eGFP knock-in line is presented as a validated genetic and imaging resource for studying SNRNP70 at endogenous levels in a living vertebrate nervous system. By overcoming limitations of conventional transgenic and overexpression‑based approaches, the model enables physiological analysis of localisation and dynamic behaviour, particularly within axonal and synaptic compartments and neuronal mRNP granules.
The authors emphasise that endogenous fluorescent tagging can serve as a versatile platform for resolving spatial organisation of RNA‑binding proteins in living neurons and for gaining new insight into mechanisms that regulate neuronal mRNA fate. The work therefore has methodological significance beyond the specific biology of SNRNP70, illustrating an approach that can be applied to other RNA‑binding proteins to study their physiological localisation and dynamics.
The source is a bioRxiv preprint; the abstract summarises experimental outcomes but does not include detailed methods, quantitative validation data, or extended datasets within the provided text. Specific experimental parameters, numbers of animals imaged, imaging conditions, or statistical analyses were not reported in the abstract and therefore are not described here. Competing interests were declared as none. Funding sources were listed by agency but the abstract did not attribute specific experiments to particular funders.
Overall, the study introduces a CRISPR knock-in zebrafish line that enables visualisation of endogenous SNRNP70 and documents its widespread and dynamic localisation in the developing nervous system, including enrichment in axons, synapses, and neuronal mRNP granules, and molecular association with PABPC1B, FUS, and UPF1.