Spatial Gene Expression Format Conversion

Overview

SGE datasets vary widely in format and resolution across platforms. Since FICTURE requires SGE in a specific format, cartloader toolkit provides this sge_convert module to standardize the raw, platform-specific SGE into a FICTURE-compatible format.

Requirements

Input Data Requirement:

Please make sure the input data (raw, platform-specific SGE) contains at least the following information. should be a transcript-indexed SGE containing at least:

• Spatial coordinates (X coordinates, Y coordinates)
• Feature metadata (such as gene symbols)
• Expression Counts

Platform Compatibility

The current sge_convert supports standarizing SGE from the following platforms:

Source	--platform Option	Required Input Files
10x Visium HD	10x_visium_hd	--in-mex, --in-parquet, --scale-json
Seq-Scope	seqscope	--in-mex
10x Xenium	10x_xenium	--in-csv
Stereo-seq	bgi_stereoseq	--in-csv
CosMx SMI	cosmx_smi	--in-csv
Vizgen MERSCOPE	vizgen_merscope	--in-csv
Pixel-seq	pixel_seq	--in-csv
Generic CSV/TSV input 1	generic	--in-csv

_{¹: For SGE from platforms not yet explicitly supported by cartloader, or from custom/preprocessed sources, sge_convert provides a generic option that accepts CSV/TSV files with basic required fields (e.g., gene, spatial coordinates, expression count) for standardization and processing.}

Example Usages

Input SGE in MEX Format

Seq-Scope

cartloader sge_convert \
    --platform seqscope \
    --in-mex /path/to/input/dir/of/mex \   
    --units-per-um 1000 \
    --icols-mtx 1 \
    --out-dir /path/to/output/dir \
    --colnames-count count \
    --filter-by-density \
    --out-filtered-prefix filtered \
    --genomic-feature count \
    --sge-visual \
    --north-up \
    --spatula /path/to/spatul/binary 

10X Visium HD

cartloader sge_convert \
    --platform 10x_visium_hd \
    --in-mex /path/to/input/dir/of/mex \   
    --in-parquet /path/to/input/parquet/file \
    --scale-json /path/to/input/json/file \
    --exclude-feature-regex '^(BLANK.*$|NegCon.*$|NegPrb.*$)' \
    --out-dir /path/to/output/dir \
    --spatula /path/to/spatul/binary \
    --sge-visual 

Input SGE in TSV/CSV Format

This applies to input SGE in TSV/CSV format from platforms including 10X Xenium, StereoSeq, Cosmx SMI, MERSCOPE, Pixel-seq. To simplify preprocessing, sge_convert automatically applies platform-specific defaults for common CSV/TSV parameters.

Below is an example converting SGE from StereoSeq.

cartloader sge_convert \
    --platform bgi_stereoseq \
    --in-csv /path/to/input/csv/file \
    --units-per-um 28.75 \
    --out-dir /path/to/output/dir \
    --colnames-count count \
    --exclude-feature-regex '^(BLANK.*$|NegCon.*$|NegPrb.*$)' \
    --filter-by-density \
    --out-filtered-prefix filtered \
    --genomic-feature count \
    --sge-visual \
    --north-up \
    --spatula /path/to/spatul/binary 

Verify your input structure

Always double-check the column names and metadata format of your input files. If they differ from the expected defaults, override them using --csv-* and --min-phred-score options.

Click to view platform-specific default settings

To streamline the process, sge_convert automatically applies platform-dependent defaults for CSV/TSV parsing based on known file formats and column conventions. Below summarizes the default values for key parameters per supported platform:

Platform	--csv-comment1	--csv-delim	--csv-colname-x	--csv-colname-y	--csv-colnames-count	--csv-colname-feature-name
10X Xenium2	False	,	x_location	y_location	-	feature_name
StereoSeq	False	\t	x	y	MIDCounts	geneID
CosMx SMI	False	,	x_local_px	y_local_px	-	target
MERSCOPE	False	,	global_x	global_y	-	gene
Pixel-seq	False	\t	xcoord	ycoord	-	geneName

_{¹ --csv-comment: If True, the lines starts with # will be treated as comments and will be skipped.}

_{² 10X Xenium: Besides the above default settings, for 10X Xenium data, sge_convert also applies --csv-colname-phredscore qv and --min-phred-score 20.}

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Actions

SGE Conversion

Converting SGE into a FICTURE-compatible TSV format. During conversion, SGE coordinates are rescaled to micrometer units based on the pixel resolution specified in the input. It's also available to apply feature (typically, genes) filtering.

(Optional) Density-based Filtering

Automatically identify and retain high-quality tissue regions based on transcript density and spatial structure. This step takes the format-standardized SGE as input and generate a density-based filtered SGE.

(Optional) SGE Visualization

Draws an image of 2D points provided as an input. In this step, it is optional to enable the --north-up option to ensuring correct spatial orientation (i.e., Y-axis increases upward/north and X-axis increases to the right/east).

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Parameters

The following outlines the minimum required parameters.

For most auxiliary parameters, the default values are recommended and could be modified when they do not suit your use case. See more details in the collapsible sections below or by running:

cartloader sge_convert --help

SGE Conversion

• --platform (str): Source platform to infer the input file format and default setting (options: "10x_visium_hd", "seqscope", "10x_xenium", "bgi_stereoseq", "cosmx_smi", "vizgen_merscope", "pixel_seq", "generic").
• --in-mex (str): Path to the input SGE directory in MEX format. Required for MEX-formatted data (e.g., 10X Visium HD, SeqScope).
• --in-csv (str): Path to the input SGE file in CSV or TSV format. Required for CSV/TSV-formatted data (e.g., 10X Xenium, StereoSeq, CosMX SMI, MERSCOPE, Pixel-seq).
• --in-parquet (str) : Path to the input parquet file with spatial coordinates, if available. Typically named tissue_positions.parquet (10X Visium HD).
• --scale-json (str): Path to the scale JSON file to compute --units-per-um, if available. Typically named scalefactors_json.json (10X Visium HD).
• --units-per-um (float): Coordinate units per micrometer (default: 1.00). Skip if --scale-json is provided.
• --out-dir (str) : Path to the output directory.
• --include-feature-regex (regex): (Optional) A regex pattern of feature/gene names to be included.
• --exclude-feature-regex (regex): (Optional) A regex pattern of feature/gene names to be excluded.

Auxiliary SGE Conversion Paramaters

Auxiliary Input MEX Parameters:

• --icols-mtx (int or comma-spearated list): Comma-separated, 1-based indices of the target genomic features among the count columns in the input matrix file. (Default: 1)
• --colnames-count (string or comma-spearated list): Comma-separated output column names for the specified genomic features. (Default: count). The number of names specified by --colnames-count must match the number of indices provided in --icols-mtx.

Auxiliary Input CSV/TSV Parameters:

• --csv-comment (flag): If enabled, lines starts with # will be skipped (default: False for 10X Xenium, StereoSeq, CosMx SMI, MERSCOPE, and Pixel-seq).
• --csv-delim (str): Delimiter for the input file (default: "," for 10X Xenium, CosMx SMI, and MERSCOPE; "\t" for StereoSeq, Pixel-seq).
• --csv-colname-x (str): Column name for X coordinates (default: x_location for 10X Xenium; x for StereoSeq; x_local_px for CosMx SMI; global_x for MERSCOPE; xcoord for Pixel-seq).
• --csv-colname-y (str): Column name for Y coordinates (default: y_location for 10X Xenium; y for StereoSeq; y_local_px for CosMx SMI; global_y for MERSCOPE; ycoord for Pixel-seq).
• --csv-colnames-count (str): Comma-separated column names for expression count. If not provided, a count of 1 per transcript (default: MIDCounts for StereoSeq).
• --csv-colname-feature-name (str): Column name for gene name (default: feature_name for 10X Xenium; geneID for StereoSeq; target for CosMx SMI; gene for MERSCOPE; geneName for Pixel-seq).
• --csv-colnames-others (str): Columns names to keep.
• --csv-colname-phredscore (str): Column name for Phred-scaled quality value estimating the probability of incorrect calls (default: qv for 10X Xenium).
• --min-phred-score (int): Phred-scaled quality score cutoff (default: 20 for 10X Xenium).

Auxiliary Output Parameters:

• --out-transcript (str): File name for output compressed transcript-indexed SGE file in TSV format (default: transcripts.unsorted.tsv.gz).
• --out-minmax (str): File name for coordinate min-max values in TSV format (default: coordinate_minmax.tsv).
• --out-feature (str): File name for compressed UMI count per gene in TSV format (default: feature.clean.tsv.gz).
• --precision-um (int): Decimal precision for transcript coordinates; set to 0 to round to integers (default: 2).
• --colname-x (str): Column name for the X-coordinate in the output SGE (default: X).
• --colname-y (str): Column name for the Y-coordinate in the output SGE (default: Y).
• --colnames-count (str): Comma-separated column names for expression count in the output SGE (default: count).
• --colname-feature-name (str): Column name for the gene name in the output SGE(default: gene).

Auxiliary Environment Parameters
If the binaries are already available in your system's PATH, you may omit these options.

• --gzip (str): Path to gzip binary; consider pigz -p 4 for faster processing. (Default: gzip)
• --spatula (str): Path to spatula binary. (Default: spatula)
• --parquet-tools (str): Required if --in-parquet is used; path to parquet-tools binary. (Default: parquet-tools)

(Optional) Density-based Filtering

• --filter-by-density (flag): Enable filtering of SGE by density.
• --out-filtered-prefix (str): Prefix for output filtered SGE files (default: filtered).
• --genomic-feature (str): Genomic feature to be used for density-based filtering. Defaults to the value of --colnames-count if only one column name is provided.

Auxiliary Density-based Filtering Paramaters

• --mu-scale (float): Scale factor for the polygon area calculation (default: 1.0).
• --radius (int): Radius for the polygon area calculation (default: 15).
• --quartile (int): Quartile for the polygon area calculation (default: 2).
• --hex-n-move (int): Sliding step (default: 1).
• --polygon-min-size (int): The minimum polygon size (default: 500).

(Optional) SGE Visualization

• sge-visual (flag): Enable SGE visualization.
• --north-up (flag): Enable the north-up orientation for the SGE visualization.

Auxiliary SGE Visualization Paramaters

• --out-xy (str): File name for output SGE visualization image (default: xy.png).
• --out-northup-tif (str): File name for output north-up orientated image (default: xy_northup.tif).
• --srs (str): If --north-up, define the spatial reference system (default: EPSG:3857).
• --resample (str): If --north-up, Define the resampling method (default: cubic). Options: near, bilinear, cubic, etc.
• --gdal_translate (str): Required if --north-up; path to gdal_translate binary. (Default: gdal_translate)
• --gdalwarp (str): Required if --north-up; path to gdalwarp binary. (Default: gdalwarp)

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Output

cartloader generates the following harmonized outputs:

Unified SGE matrix

Both SGE conversion and density-based filtering generate a unified SGE matrix, consisting of:

transcripts.unsorted.tsv.gz: transcript-indexed SGE in TSV

X        Y        gene     count
295.29   1422.35  Myo3a    0
1745.54  1110.72  Med14    1
1745.54  1110.72  Ntpcr    1

• X: X coordinates in um
• Y: Y coordinates in um
• gene: gene symbols
• count: expression count per pixel per gene

feature.clean.tsv.gz: UMI counts on a per-gene basis in TSV

gene           gene_id             count
Gm29155        ENSMUSG00000100764  1
Pcmtd1         ENSMUSG00000051285  431
Gm26901        ENSMUSG00000097797  1

* gene: gene symbols * gene_id: gene IDs * count: expression count per gene

coordinate_minmax.tsv: X Y min/max coordinates

xmin    0.14
xmax    2359.90
ymin    0.23
ymax    1439.95

• xmin xmax: min and max X coordinates in um
• ymin ymax: min and max Y coordinates in um

SGE Images

• When --sge-visual is enabled, a monochrome PNG image is generated to visualize the SGE data.
• When --north-up is enabled, a georeferenced TIFF image is produced with a north-up orientation.