White et al. · bioRxiv (preprint) · 2026
Synaptotagmin isoforms differentially regulate glutamate and GABA release in the lateral habenula
White Dustin N., Kushner J. Keenan, Winther Kelly E., McGovern Dillon J., Basta Tamara, Donaldson Zoe R., Hoeffer Charles A., Root David H., Stowell Michael H. B.
The study
What was asked, and what was found
White et al., bioRxiv, 2026 asked how one nerve terminal can release two opposing neurotransmitters and control each of them separately. Projections from the entopeduncular nucleus to the lateral habenula release both glutamate and GABA, and the authors found the two sitting in separate vesicle populations inside the same terminal, each paired with its own calcium sensor: Synaptotagmin 2 with the glutamate vesicles and Synaptotagmin 3 with the GABA vesicles.
To test that pairing they used AUMsilence sdASOs from AUM BioTech. Five oligonucleotides were designed against mouse Syt2 and five against Syt3, 20 to 21 nucleotides each, and injected stereotaxically as 400 nL directly into the entopeduncular nucleus of live mice, with the same nucleus on the other side of the brain left untreated as the control. Fluorescently labelled control oligonucleotides were injected separately to measure how far the material spread. Tissue was taken 3 to 5 days after injection.
Recording from lateral habenula neurons afterwards gave two clean and opposite results. Knocking down Syt2 raised the frequency and amplitude of miniature excitatory currents and broadened their half width and decay, while leaving the inhibitory currents unchanged. Knocking down Syt3 did the reverse, raising the frequency of miniature inhibitory currents with no effect on the excitatory ones. Protein knockdown itself was checked by western blot against the untreated side and the authors describe it as variable, so the functional recordings are what carry the conclusion. This is a preprint and has not been peer reviewed.
Key findings
- AUMsilence sdASOs injected straight into one entopeduncular nucleus of a live mouse knocked down Syt2 and changed the excitatory currents recorded downstream in the lateral habenula.(Results, Figure 4)
- Knocking down Syt2 left the inhibitory currents untouched, so the effect was specific to the glutamate side of the same terminal.(Results, Figure 4)
- The Syt2 knockdown also widened the excitatory events and slowed their decay, which the authors read as more glutamate packed into each vesicle rather than only more vesicles released.(Abstract)
- Knocking down Syt3 produced the mirror image, raising the frequency of inhibitory currents and leaving the excitatory ones alone.(Results, Figure 5)
- The two knockdowns together show that one presynaptic terminal can run its glutamate and its GABA vesicles on separate calcium sensors.(Discussion)
- Knockdown was checked by western blot against the untreated side of the same brain and was uneven, so the functional recordings rather than the protein measurement carry the result.(Methods, Western Blot Analysis and ASO Knockdown Quantification)
For research use only. Not for use in diagnostic or therapeutic procedures.