New CRISPRi Atlas and X-Cell Model Advance Human iPSC Gene Mapping

Mapping the Human iPSC Transcriptome

A new research resource published in Nature Biotechnology provides a detailed look at how individual genes regulate human induced pluripotent stem cells (iPSCs). By utilizing CRISPR interference (CRISPRi) to systematically silence 11,692 genes, researchers analyzed the impact on the transcriptome across more than 2.5 million single cells.

The study, titled A genome-scale CRISPRi perturbation atlas of human induced pluripotent stem cells, functions as a hypothesis engine for the scientific community. By allowing researchers to look up the results of specific gene perturbations, the atlas aims to reduce the need for labor-intensive, individual experiments. The researchers successfully identified new biological regulators, such as ZBTB41, which serves as a metabolic factor, and RNF7, which contributes to pluripotency regulation.

Xaira Therapeutics and the X-Cell Model

Parallel to academic efforts, Xaira Therapeutics has released a large-scale virtual cell model named X-Cell. The company, which launched in 2024 under the leadership of CEO Marc Tessier-Lavigne, aims to transition drug discovery from an artisanal process to an engineering discipline.

The model is powered by a massive dataset known as X-Atlas/Pisces, which contains 25.6 million cells across 16 biological contexts. Unlike previous autoregressive models that process data sequentially, X-Cell employs a diffusion-based architecture. Bo Wang, senior vice president and head of biomedical AI at Xaira, explained that this approach functions like an iterative editing process.

Enhancer Regulation in Astrocytes

In a separate study published in Nature, researchers investigated the regulatory landscape of human primary astrocytes to identify distal enhancers. The team used a CRISPRi screening method on 979 candidate enhancers, selecting regions that remained in an open chromatin state across different astrocyte datasets.

The researchers confirmed that their normal human astrocytes (NHAs) maintained a fetal identity, providing a stable baseline for observing how distal enhancers control gene expression. This work highlights the utility of large-scale CRISPRi screens in uncovering the functional roles of non-coding genomic regions.

Methodological Advances in Single-Cell Sequencing

The precision of these screens relies on advanced sequencing protocols. A protocol published in Nature describes the use of joint multiomic single-cell DNA-RNA sequencing, known as SDR-seq, to phenotype genomic variants. This method requires meticulous cell preparation, including fixation and permeabilization steps, to ensure data quality. The technique has been applied to WTC-11 iPS cells from the Coriell Institute for Medical Research, verified for normal karyotype, to maintain consistency in experimental outcomes.

While the human genome consists of approximately 3 billion nucleotides, genome.gov notes that there is no consistent correlation between biological complexity and genome size. These recent efforts to map gene function at scale represent a shift toward utilizing large, context-rich datasets to decode the complexity of the genome, moving beyond simple sequencing toward predictive modeling of cell behavior.

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