CRISPR enables complete control of neuronal LRRTM2

Researchers have used a two-guide CRISPR knock-in technique to replace the entire coding sequence (CDS) of the synaptic LRRTM2 protein (Leucine-Rich Repeat Transmembrane neuronal protein 2) with a freely editable custom donor sequence. The approach overcomes the limitations of traditional editing, which often disrupts neuronal function, and it allows for the detailed study of the critical adhesion molecule's trafficking and function.

By: Gorm Palmgren - Jan. 21, 2025

LRRTM2 is critical for synapse development and function but remains challenging to study due to the limitations of conventional genome editing. By replacing the entire endogenous LRRTM2 CDS with an editable donor sequence in rat hippocampal neurons, the researchers tagged LRRTM2 at its N-terminus, enabling precise analysis of its localisation.

They found LRRTM2 in 80% of synapses, with its synaptic abundance correlating with levels of the scaffolding protein PSD-95 and the glutamate receptor AMPAR. Unexpectedly, LRRTM2 was also enriched with AMPAR outside synapses, highlighting novel aspects of its distribution.

By further mutating LRRTM2's C-terminal domain, the researchers increased synaptic LRRTM2 levels without corresponding changes in AMPAR enrichment, separating its trafficking from functional outcomes.

The study was conducted by Stephanie Pollitt and Thomas Blanpied from University of Maryland School of Medicine, and it was published in Journal of Neuroscience on 17 January 2025.

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