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Systematic contextual biases in SegmentNT relevant to all nucleotide transformer models

Ebbert, M. T. W.; Ho, A.; Dutch, B.; Page, M. L.; Byer, B. K.; Hankins, K. L.; Sabra, H.; Aguzzoli Heberle, B.; Wadsworth, M. E.; Fox, G. A.; Karki, B.; Hickey, C.; Fardo, D. W.; Bumgardner, C.; Jakubek, Y. A.; Steely, C. J.; Miller, J. B.

2025-04-15 bioinformatics
10.1101/2025.04.09.647946 bioRxiv
Show abstract

Recent advances in large language models (LLMs) have extended to genomic applications, yet model robustness relative to context changes is unclear. Here, we demonstrate two intrinsic biases (input sequence length and position) affecting SegmentNT, a model included with the Nucleotide Transformer that uniquely provides nucleotide-level predictions of biological features. We demonstrate that nucleotide position within the input sequence (beginning, middle, or end) alters the nature of SegmentNTs prediction probabilities, and that longer input sequence improves model performance, but with diminishing returns, suggesting the surprisingly small optimal input length of [~]3,072 nucleotides. We identify notable discrepancies between SegmentNT and gene annotations that may indicate the model is identifying additional biological characteristics, but further work is needed. Finally, we identify a 24-nucleotide periodic oscillation in SegmentNTs prediction probabilities, revealing an intrinsic bias potentially linked to the models training tokenization (6-mers) and the models architecture. Our findings provide actionable and generalizable insights to improve foundation model training and application by mitigating intrinsic biases.

Published in Nucleic Acids Research (predicted rank #8) · training set

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