SYNAPTIC DEFECTS IN <EM>TARDBP </EM>CONDITIONAL KNOCK-OUT AUTAPTIC NEURONS

Recent studies have identified TDP-43 as a critical regulator of mRNA processing. Loss of nuclear TDP-43 leads to widespread splicing abnormalities, including the incorporation of toxic cryptic exons into dozens of transcripts, many encoding proteins essential for synaptic transmission. Consequently, aberrant splicing of key synaptic mRNAs may disrupt multiple steps of the neurotransmission process in TDP43-proteinopathies. A prominent example is UNC13A, a core active zone protein whose transcript undergoes cryptic exon inclusion leading to markedly reduced UNC13A levels following TDP-43 knockdown (Ma, X. R., et al., 2022; Brown, A. L., et al., 2022). Despite these findings, the mechanisms by which cryptic exon inclusion resulting from nuclear TDP-43 depletion alters synaptic structure and function remain poorly understood.
Neuronal autaptic cultures, in which isolated neurons form synapses onto themselves, provide a powerful system for studying synaptic function at the single-cell level. This approach enables precise separation of presynaptic and postsynaptic contributions at both structural and electrophysiological levels. Using primary hippocampal cultures from conditional Tardbp knockout mice expressing a tamoxifen-inducible CRE (CAGCre-ER; Tardbp^flox/flox), we investigated the effects of nuclear TDP-43 depletion in autaptic primary neurons, focusing on both glutamatergic and GABAergic neurotransmission.
Immunofluorescence analyses revealed presynaptic abnormalities in TDP-43–deficient neurons, including a reduced number of active zones compared with wild-type controls. Ongoing studies aim to determine whether these structural deficits are accompanied by functional impairments in synaptic transmission.