Response Magnitude as a Dominant Signal for Held-Out CRISPRi Perturbation Effect Prediction

2026-07-31

AI Summary

Predicting the transcriptomic effects of CRISPRi perturbations on unseen target genes remains a key challenge in single-cell biology. Leveraging the Virtual Cell Challenge benchmark data, this study reveals that perturbation response magnitude—a low-dimensional signal—dominates predictive performance: a simple linear model using only four magnitude scalars outperforms existing complex deep learning approaches. Systematic evaluation via linear regression, random forests, and deep multilayer perceptrons, assessed with Anderson–Darling distance, demonstrates that magnitude-based features not only achieve strong performance on the original dataset but also exhibit robust positive zero-shot transfer across cell types and independent datasets. These findings challenge the prevailing assumption that high-dimensional gene expression modeling is necessary for accurate perturbation effect prediction.

Abstract

Predicting the magnitude of a CRISPRi perturbation's transcriptomic effect on held-out target genes is an important open problem in single-cell biology. Recent work has documented that simple baselines often match or exceed deep perturbation predictors on related protocols. We study this phenomenon on the Virtual Cell Challenge (VCC) benchmark under a strict held-out target-gene split, identify the specific low-dimensional signal that drives the gap, and characterize how it transfers across cell types. The target is the log Anderson-Darling distance from non-targeting controls, which is strongly predictable from four deterministic scalar functions of the 2,000-dimensional input. A deep MLP encoder with direct access to the full input collapses toward the marginal training mean, and standard remedies do not close the gap. A linear regression on the four magnitude scalars alone exceeds the strongest x-only classical model, while a Random Forest on the input plus the four scalars substantially outperforms our deep proof-of-concept encoder. Two pre-specified controls attribute the magnitude gain to per-row alignment rather than added dimensionality. Under zero-shot transfer to two external CRISPRi screens evaluated against a target-gene endpoint rebuilt from single-cell data, magnitude-only predictors transfer positively whereas expression-only predictors are negative or unresolved. Exposing magnitude to the deep encoder improves transfer over its expression-only counterpart, yet the encoder does not outperform a four-scalar linear regression on the same features. We also find that the Anderson-Darling column distributed with these screens measures transcriptome-wide response breadth rather than target-gene effect strength, so evaluating transfer against it scores a different outcome.

Problem

• CRISPRi perturbation
• held-out target genes
• transcriptomic effect prediction
• response magnitude
• single-cell biology

Innovation

• response magnitude
• CRISPRi perturbation
• held-out target prediction
• zero-shot transfer
• low-dimensional signal