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Buchwald, L. M.

Publications and source records attributed to Buchwald, L. M..

2 recordsLinked to original sources

Raw-count embeddings improve single-cell foundation models

Single-cell transformer foundation models have grown to hundreds of millions of parameters, yet the preprocessing choices that underlie them, including gene ranking and library-size normalisation, have not been systematically benchmarked. Testing seven strategies, we find these elaborations are largely unnecessary: non-normalised, log-transformed counts give the best performance, and gene order barely matters, with even random ordering outperforming sophisticated rank-based schemes. The resulting model, Gene Intelligence, projects log1p-transformed raw counts directly onto each token embedding and jointly predicts masked tokens and counts, using no normalisation, positional encoding, or read-depth tokens. Despite this simplicity, it achieves state-of-the-art performance in the tested gene-level tasks and in doublet detection, and matches large current foundation models on cell-classification tasks while using 10-to 200-fold fewer parameters.

bioinformatics↗

GephyrinΔ199-233 - an epileptogenic microdeletion

Gephyrin, as the main organizer of inhibitory synapses, is crucial for inhibitory signal transmission, and implicated in various neurological disorders. Various studies have identified gephyrin microdeletions in conditions of autism, schizophrenia, and epilepsy. Those deletions affected the N-terminal G-domain and/or the central C-domain of gephyrin while the receptor binding C-terminal E-domain was not affected. Here, we investigated the importance of a specific microdeletion ({Delta}199-233) within the C-domain using a full-body knock-in mouse model. Homozygous mice displayed a severe phenotype characterized by reduced fertility, increased mortality, and neurological deficits at early developmental stages. Analyses in dissociated hippocampal neurons demonstrated disrupted synaptic targeting of gephyrin {Delta}199-233 that harbors the functionally important S-palmitoylation site at Cys212. Simultaneously, we found adaptations at the excitatory synapse, with smaller, but more numerous clusters of the excitatory scaffolding protein PSD95. Although, gephyrin {Delta}199-233 showed unexpectedly a facilitated receptor interaction, inhibitory signal transmission was reduced. We hypothesize, that the gephyrin {Delta}199-233-mediated reduction of inhibition triggers compensatory excitation, which possibly fails and/or disrupts the excitation/inhibition ratio in our mouse model. These findings highlight the critical role of the gephyrin C-domain and its post-translational modifications in synaptic function and neuronal health, offering a novel mouse model for the development of potential therapeutic targets addressing gephyrin-associated neurological disorders.

neuroscience↗