Human and Mammalian Brain Atlas v0.5

_{BRAIN Initiative Cell Atlas Network (BICAN)}

The HMBA Whole-Brain (WB) Atlas is a cross-species, whole-brain single-cell RNA-seq taxonomy. It covers human, macaque, and marmoset, using the mouse and human whole-brain taxonomies (Yao et al., Siletti et al.) as reference, and spans roughly 21 million cells.

This page documents the v0.5 data share: what is delivered, how it is organized, and what every metadata column means.

Status: v0.5 is a working release. Known gaps and planned fixes are tracked in GitHub issues.

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Contents

• At a glance
• Regional annotation working groups
• Community annotation
• Planned versions
• Data release
  • Downloading
  • 1. AIT taxonomy files
  • 2. MapMyCells mapping files
• Sampling overview
• Pipeline
• Metadata dictionary
• Contact

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At a glance

Version	v0.5
Species	human, macaque, marmoset
References	mouse and human whole brain (Yao et al., Siletti et al.)
Cells	~21 million
Taxonomy hierarchy	neighborhood → class → subclass → cluster
Ortholog gene space	15,138 genes shared across human / macaque / marmoset / mouse
Cluster ID format	{species}:{neighborhood}:{int}

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Regional annotation working groups

Annotation is organized into working groups, each responsible for one brain region or cross-cutting slice of the taxonomy. Groups review the cell types in their region across all species, reconcile them against the reference taxonomies and the spatial data, and settle the subclass and class labels that ship. Questions about a specific region are best directed to its leads.

Region	Lead(s)
Neocortex	Rebecca Hodge
Medial temporal lobe	Aaron Garcia, Yuanyuan Fu
Basal ganglia	Nelson Johansen, Yuanyuan Fu
Thalamus	Brian Long, Meghan Turner
Hypothalamus	Fenna Krienen, Stephanie Seeman
Midbrain, Medulla, Pons	Dan Yuan, Zizhen Yao, Cindy van Velthoven, Hongkui Zeng
Cerebellum	Rebecca Hodge
Spinal cord	Matthew Schmitz, Nelson Johansen
Non-neuronal WB	Yuanyuan Fu
Cross-species WB	Zizhen Yao, Trygve Bakken

To request membership in a working group, contact Lauren Kruse (lauren.kruse@alleninstitute.org).

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Community annotation

Annotating a taxonomy this large is a community effort. Two routes are in progress, and both will be made available to the regional annotation working groups.

ABC Atlas. The v0.5 data will be browsable through the ABC Atlas. (Link to come.)

Taxonomy editing tool. A taxonomy editing tool will be made available so annotators can propose and record changes to cluster, subclass, and class labels directly against the released taxonomy. (Link to come.)

In the meantime, feedback on cell type annotations is welcome; see Contact.

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Planned versions

v0.5 is the current release. Dates are targets, not commitments.

Version	Target	Access	Focus
v1.0	December 2026	BICAN	Regional working group feedback, improved spatial mapping, cross-species subclass alignment
v2.0	Q2 2027	Public	New data pull adding donors across species; delivered through ABC Atlas, MapMyCells, and brain-map
v3.0	TBD	Public	Complete cortical and subcortical sampling in all species

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Data release

All v0.5 artifacts live under a single S3 prefix:

s3://released-taxonomies-802451596237-us-west-2/HMBA/whole_brain/0.5/

One subfolder per species, each holding that species' AIT taxonomy file and its MapMyCells assets:

0.5/
├── human/       AIT file + MapMyCells files
├── macaque/     AIT file + MapMyCells files
└── marmoset/    AIT file + MapMyCells files

Downloading

The bucket allows anonymous reads, so no AWS account or credentials are needed. You do need the AWS CLI, and every command needs both --no-sign-request and --region us-west-2.

See what is available, with sizes:

aws s3 ls s3://released-taxonomies-802451596237-us-west-2/HMBA/whole_brain/0.5/ --no-sign-request --region us-west-2 --recursive --human-readable

Download everything for one species:

aws s3 sync s3://released-taxonomies-802451596237-us-west-2/HMBA/whole_brain/0.5/human/ ./human/ --no-sign-request --region us-west-2

Download a single file:

aws s3 cp s3://released-taxonomies-802451596237-us-west-2/HMBA/whole_brain/0.5/human/<filename> . --no-sign-request --region us-west-2

Check your disk space first. Individual files run to several GB, and the MapMyCells reference markers are roughly 8 GB per species. aws s3 sync is resumable, so an interrupted transfer can be restarted with the same command and will skip what already arrived.

1. AIT taxonomy files

AIT (Allen Institute Taxonomy) is an AnnData-based container that bundles a taxonomy into a single self-describing file: the expression matrix, per-cell metadata, the full label hierarchy, and the latent spaces the clustering was built on all travel together. Anything you would normally have to reassemble from a matrix plus a handful of side-car tables is already joined and aligned, so one file is enough to browse the taxonomy, re-analyze it, or map new query data onto it.

One AIT file per species, carrying both gene spaces: the species-native full gene set and the 15,138-gene ortholog space shared across species. Use the ortholog space for cross-species comparisons, and the full gene set when you need species-specific genes that have no one-to-one ortholog.

• species ∈ {human, macaque, marmoset}. No AIT file is shipped for mouse. The mouse and human whole-brain taxonomies (Yao et al., Siletti et al.) served as the references that these were mapped and aligned to.
• All neighborhoods for a species are contained in the same file; there is no per-neighborhood split.
• obs holds the per-cell metadata; see the Metadata dictionary.
• obsm carries the scVI latent representations used for integration and clustering, along with the global 2D UMAP coordinates as X_umap. The UMAP was computed from projected scVI embeddings from the global integration.
• Cells flagged as junk during global or per-neighborhood integration have been removed.

2. MapMyCells mapping files

Reference assets for mapping new query data onto the HMBA WB taxonomy with MapMyCells / cell_type_mapper, provided per species alongside the AIT file.

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Sampling overview

Sampling concentrates on subcortical structures in human, macaque, and marmoset. Neocortex is already covered in depth by earlier atlases, so this collection goes deep on the subcortex instead: basal ganglia, thalamus, hypothalamus, amygdala and extended amygdala, hippocampal formation, claustrum-endopiriform, midbrain, pons, medulla, and cerebellum. Marmoset was collected as whole-brain tiled sampling rather than dissected region by region.

Species	Donors	Libraries	Nuclei
Human	12	1,390	9.7M
Macaque	15	364	2.7M
Marmoset	6	324	1.7M

The polar plots break sampling down by HOMBA higher anatomical region, so wedge length reflects sampling effort rather than cell yield. These counts cover the nuclei newly generated for HMBA by 10X Multiome; the taxonomy also incorporates cells from the external studies listed under study in the Metadata dictionary.

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Pipeline

The taxonomy is built by an iterative loop rather than a single pass. Clusters are proposed, stress-tested against QC and spatial evidence, and the partition is revised, repeating until the structure holds up.

1. Basic QC. Per-cell filtering on gene count, UMI count, and mitochondrial fraction, plus doublet scoring with both dblFinder and SOLO. Scores are retained on every cell rather than used only as a hard filter.

2. Data partition. Cells are mapped to the human WB v1.5 reference (which itself integrates Siletti and AIT21) and partitioned into neighborhoods using the mapped subclass labels. A global integration and label transfer runs across the full dataset to establish the initial cross-species frame.

3. Integration within each neighborhood. Each neighborhood is integrated separately, at a tractable scale:

• Down-sampling by mapped human WB v1.5 cluster, capped at 400 cells per cluster, so abundant types don't dominate the embedding.
• Feature selection from the union of 4k HVGs per species per neighborhood, augmented with neighborhood-level transcription-factor markers drawn from human WB v1.5 and AIT33.

4. Cross-species clustering. Within-species clustering runs in the shared integrated space using transcriptomic_clustering. Subclass and class labels are then assigned by transfer from AIT33. Clustering within species inside a common space is what makes clusters comparable across species without forcing them to merge.

5. Post-clustering QC. Clusters are flagged as doublet, low-quality, or species-specific. Nothing is silently dropped.

6. Iterate. If the QC pass surfaces problems, the neighborhood partition is revised and steps 2 through 5 rerun. Only once the partition is stable does the release move on.

7. Spatial validation. The atlas is developed in a tight loop with the HMBA spatial transcriptomics teams. Clusters showing diffuse or absent spatial patterns, either in the cluster itself or across its cross-species matches, are flagged, and their subclass/class assignments are refined against what the spatial data actually supports. This feedback is a first-class input to the taxonomy, not a downstream check.

8. Joint cell type annotation. The transcriptomic and spatial evidence are reconciled into the final annotation: within-species clusters with their QC flags, cross-species subclass and class labels, and cross-species cluster correspondence.

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Metadata dictionary

The obs schema is identical across the ortholog and full-gene-space files.

Cell-type labels (HMBA WB taxonomy v0.5, final)

Column	Description
cluster	Cluster ID, formatted {species}:{neighborhood}:{int}
subclass	Subclass label
class	Class label
neighborhood	Final neighborhood assignment used for clustering

Sample / donor identity

Column	Description
species	human / macaque / marmoset
donor	Donor ID
sample	Library / 10X load ID
sex	Donor sex
age	Donor age
study	Source study the cell came from: HMBA, Siletti, AIT21, or Macosko
chemistry	10X chemistry: multiome (HMBA), snRNAseq (Siletti), 10Xv2 / 10Xv3 (AIT21), Macosko_snRNAseq (Macosko)

Anatomical

Column	Description
brain region	Coarse brain region
roi	Region of interest, finer than brain region. Currently inaccurate for marmoset; values should all be brain

QC metrics (continuous)

Column	Description
n_genes_by_counts	Genes detected per cell
total_counts	Total UMI count per cell
pct_counts_mt	Mitochondrial read percentage
doublet_score	dblFinder doublet score
solo_doublet_score	solo doublet score
tso_reads_fraction	Fraction of reads containing the 10X TSO sequence (Optimus pipeline)
reads_exonic_intronic_fraction	Fraction of reads mapping to exons + introns (Optimus pipeline)

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Contact

Questions, access requests, or issues with the data share: open an issue or reach out to the HMBA cross-species working group.

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Related tools

• AllenInstituteTaxonomy: AIT taxonomy file format and utilities
• transcriptomic_clustering: large-scale clustering
• cell_type_mapper: MapMyCells reference mapping