SPLISOSM — Spatial Isoform Statistical Modeling

SPLISOSM (SPatiaL ISOform Statistical Modeling, pronounced spliceosome) is a Python package for analyzing RNA-processing patterns in spatial transcriptomics (ST) data. It uses multivariate, kernel-based association tests to detect:

1. Spatial variability (SV) of isoform usage, isoform expression, or gene expression across spatial locations; and
2. Differential isoform usage (DU) against spatial covariates such as region annotations or RNA-binding-protein (RBP) expression, optionally conditioned on spatial autocorrelation.

Built on the Hilbert–Schmidt Independence Criterion (HSIC), the tests are multivariate — each gene is summarized by a single p-value aggregated across all of its isoforms — and well-calibrated without permutation sampling.

Supported platforms & feature types

SPLISOSM is platform-agnostic. Confirmed-compatible data types include:

SPLISOSM does not perform isoform quantification itself. See the Feature Quantification guide for per-platform preprocessing recipes and loaders in splisosm.io.

Choosing a model class

SPLISOSM exposes three entry-point classes with a shared setup_data → test_* → get_formatted_test_results lifecycle:

*SplisosmGLMM is calibrated for DU testing only; its SV test is conservative.

Decision tree:

Is your data on a REGULAR GRID (Visium HD, Xenium binned, etc.)?
├── YES →  SplisosmFFT  (fastest; requires SpatialData input)
└── NO  →  Interested in parametric effect sizes?
          ├── YES →  SplisosmGLMM  (GLM/GLMM; DU only)
          └── NO  →  SplisosmNP    (recommended default)

Installation

# stable release from PyPI
pip install splisosm

# or latest from GitHub
pip install git+https://github.com/JiayuSuPKU/SPLISOSM.git#egg=splisosm

Optional extras:

# SpatialData input support for SplisosmFFT, plus gpytorch/FINUFFT GP backends for DU
pip install "splisosm[sdata,gp]"

Quick start

from splisosm import SplisosmNP

model = SplisosmNP()
model.setup_data(
    adata,                         # AnnData of shape (n_spots, n_isoforms)
    spatial_key="spatial",         # adata.obsm key for coordinates
    layer="counts",                # raw isoform counts
    group_iso_by="gene_symbol",    # adata.var column grouping isoforms → gene
)

# Spatial variability of isoform usage (SVP genes)
model.test_spatial_variability(method="hsic-ir")
df_sv = model.get_formatted_test_results("sv", with_gene_summary=True)

# Differential usage vs. a covariate matrix (e.g. RBP expression), conditioned on space
model.setup_data(
    adata, spatial_key="spatial", layer="counts", group_iso_by="gene_symbol",
    design_mtx=covariates, covariate_names=cov_names,
    skip_spatial_kernel=True,      # DU-only: no CAR kernel needed
)
model.test_differential_usage(method="hsic-gp")
df_du = model.get_formatted_test_results("du")

SPLISOSM works with non-spatial / single-cell data too: pass adj_key pointing to an adata.obsp[...] neighborhood graph (e.g. "connectivities" from scanpy.pp.neighbors) in place of spatial_key.

For gene-level spatial variability as a drop-in for SPARK-X or Moran's I:

from splisosm.utils import run_hsic_gc
res = run_hsic_gc(gene_counts, coordinates)     # or run_hsic_gc(adata=adata, spatial_key="spatial")

See the Quick Start for the full-defaults reference and Statistical Methods for the underlying HSIC framework, CAR kernel, cumulant null approximations, GP backends, and the GLMM parametric alternative.

Documentation & tutorials

• Documentation: https://splisosm.readthedocs.io/
• Tutorial gallery: long-read (SiT, Visium-HD ONT), short-read 3′ (Visium HD, Slide-seq), FFPE probe (Visium / Visium HD), in situ codeword (Xenium Prime 5K, segmented single-cell).
• Paper-companion code and analyses: https://github.com/JiayuSuPKU/SPLISOSM_paper
• Interactive visualization of spatial transcript diversity in mouse and human brain:
  • Adult mouse brain (Visium, Visium + ONT, Xenium Prime 5K): Open Google Colab.
  • Human DLPFC and glioma samples (Visium, Visium + ONT): Open Google Colab.

Change log

See the changelog for detailed release notes.

Reporting issues

Please file bugs and feature requests on the GitHub Issues page.

References

SplisosmNP and SplisosmGLMM are described in

Su, Jiayu, et al. “Mapping isoforms and regulatory mechanisms from spatial transcriptomics data with SPLISOSM.” Nature Biotechnology (2026): 1–12.

link to paper

The FFT-based acceleration of SplisosmFFT is described in

Su, Jiayu, et al. "On the consistent and scalable detection of spatial patterns." arXiv preprint arXiv:2602.02825 (2026).

link to preprint