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GEO Data

Query and access Gene Expression Omnibus datasets using Biopython's Entrez module.

Required Setup

python
from Bio import Entrez

Entrez.email = 'your.email@example.com'  # Required by NCBI
Entrez.api_key = 'your_api_key'          # Optional

GEO Database Types

| Database | db value | Description | |----------|----------|-------------| | GEO DataSets | gds | Curated datasets (GDS) | | GEO Profiles | geoprofiles | Individual gene profiles |

GEO Record Types: | Prefix | Type | Description | |--------|------|-------------| | GSE | Series | Complete study/experiment | | GSM | Sample | Individual sample | | GPL | Platform | Array/sequencing platform | | GDS | DataSet | Curated, normalized dataset |

Searching GEO

Search GEO DataSets (GDS)

python
from Bio import Entrez

Entrez.email = 'your.email@example.com'

# Search curated datasets
handle = Entrez.esearch(db='gds', term='breast cancer AND Homo sapiens[orgn]', retmax=10)
record = Entrez.read(handle)
handle.close()

print(f"Found {record['Count']} datasets")
print(f"IDs: {record['IdList']}")

Search GEO Series (GSE)

python
# Search GEO Series via gds database
# Use entry_type filter
handle = Entrez.esearch(db='gds', term='RNA-seq[title] AND human[orgn] AND gse[entry_type]', retmax=10)
record = Entrez.read(handle)
handle.close()

Common Search Fields

| Field | Description | Example | |-------|-------------|---------| | [orgn] | Organism | human[orgn] | | [title] | Dataset title | breast cancer[title] | | [description] | Description text | stem cell[description] | | [platform] | Platform GPL | GPL570[platform] | | [entry_type] | Record type | gse[entry_type], gds[entry_type] | | [gdstype] | Study type | expression profiling[gdstype] | | [pubmed] | PubMed ID | 35412348[pubmed] | | [pdat] | Publication date | 2024[pdat] |

GDS Types

python
# Expression profiling by array
term = 'expression profiling by array[gdstype] AND cancer'

# RNA-seq expression
term = 'expression profiling by high throughput sequencing[gdstype]'

# ChIP-seq
term = 'genome binding/occupancy profiling[gdstype]'

Fetching GEO Information

Get GEO DataSet Summary

python
# Fetch summary for GDS records
handle = Entrez.esummary(db='gds', id='200024320')
record = Entrez.read(handle)
handle.close()

summary = record[0]
print(f"Accession: {summary['Accession']}")
print(f"Title: {summary['title']}")
print(f"Summary: {summary['summary'][:200]}...")
print(f"Organism: {summary['taxon']}")
print(f"Platform: {summary['GPL']}")
print(f"Samples: {summary['n_samples']}")

Summary Fields

python
summary['Accession']     # GSE/GDS accession
summary['title']         # Dataset title
summary['summary']       # Description
summary['taxon']         # Organism
summary['GPL']           # Platform ID
summary['n_samples']     # Number of samples
summary['FTPLink']       # FTP download link
summary['PubMedIds']     # Associated publications
summary['gdsType']       # Dataset type
summary['ptechType']     # Platform technology

Code Patterns

Search and List GEO Series

python
from Bio import Entrez

Entrez.email = 'your.email@example.com'

def search_geo(term, entry_type='gse', max_results=20):
    full_term = f'{term} AND {entry_type}[entry_type]'
    handle = Entrez.esearch(db='gds', term=full_term, retmax=max_results)
    search = Entrez.read(handle)
    handle.close()

    if not search['IdList']:
        return []

    handle = Entrez.esummary(db='gds', id=','.join(search['IdList']))
    summaries = Entrez.read(handle)
    handle.close()

    results = []
    for s in summaries:
        results.append({
            'accession': s['Accession'],
            'title': s['title'],
            'organism': s['taxon'],
            'samples': s['n_samples'],
            'platform': s['GPL']
        })
    return results

datasets = search_geo('breast cancer RNA-seq AND human[orgn]')
for ds in datasets:
    print(f"{ds['accession']}: {ds['title'][:60]}... ({ds['samples']} samples)")

Find RNA-Seq Datasets

python
def find_rnaseq_datasets(organism, keywords, max_results=20):
    term = f'{keywords} AND {organism}[orgn] AND expression profiling by high throughput sequencing[gdstype] AND gse[entry_type]'

    handle = Entrez.esearch(db='gds', term=term, retmax=max_results)
    search = Entrez.read(handle)
    handle.close()

    if not search['IdList']:
        return []

    handle = Entrez.esummary(db='gds', id=','.join(search['IdList']))
    summaries = Entrez.read(handle)
    handle.close()

    return summaries

datasets = find_rnaseq_datasets('Homo sapiens', 'COVID-19')
for ds in datasets:
    print(f"{ds['Accession']}: {ds['n_samples']} samples - {ds['title'][:50]}...")

Get GSE Download Link

python
def get_geo_ftp(gse_accession):
    '''Get FTP download link for a GSE'''
    handle = Entrez.esearch(db='gds', term=f'{gse_accession}[accn]')
    search = Entrez.read(handle)
    handle.close()

    if not search['IdList']:
        return None

    handle = Entrez.esummary(db='gds', id=search['IdList'][0])
    summary = Entrez.read(handle)[0]
    handle.close()

    return summary.get('FTPLink')

ftp_link = get_geo_ftp('GSE123456')
print(f"Download from: {ftp_link}")

Link GEO to SRA

Many GEO RNA-seq datasets have associated SRA data.

python
def geo_to_sra(gse_accession):
    '''Find SRA runs associated with a GEO series'''
    # Search GEO
    handle = Entrez.esearch(db='gds', term=f'{gse_accession}[accn]')
    search = Entrez.read(handle)
    handle.close()

    if not search['IdList']:
        return []

    # Link to SRA
    handle = Entrez.elink(dbfrom='gds', db='sra', id=search['IdList'][0])
    links = Entrez.read(handle)
    handle.close()

    if not links[0]['LinkSetDb']:
        return []

    sra_ids = [link['Id'] for link in links[0]['LinkSetDb'][0]['Link']]

    # Get SRA accessions
    handle = Entrez.esummary(db='sra', id=','.join(sra_ids[:50]))
    summaries = Entrez.read(handle)
    handle.close()

    runs = []
    for s in summaries:
        expxml = s.get('ExpXml', '')
        if 'SRR' in str(expxml) or 'SRX' in str(expxml):
            runs.append(s)
    return runs

sra_data = geo_to_sra('GSE123456')
print(f"Found {len(sra_data)} SRA records")

Search by PubMed ID

python
def geo_from_pubmed(pmid):
    '''Find GEO datasets associated with a publication'''
    handle = Entrez.elink(dbfrom='pubmed', db='gds', id=pmid)
    links = Entrez.read(handle)
    handle.close()

    if not links[0]['LinkSetDb']:
        return []

    gds_ids = [link['Id'] for link in links[0]['LinkSetDb'][0]['Link']]

    handle = Entrez.esummary(db='gds', id=','.join(gds_ids))
    summaries = Entrez.read(handle)
    handle.close()

    return summaries

datasets = geo_from_pubmed('35412348')
for ds in datasets:
    print(f"{ds['Accession']}: {ds['title']}")

Download GEO Data (GEOparse)

For full data parsing, use the GEOparse library:

python
# pip install GEOparse
import GEOparse

# Download and parse GSE
gse = GEOparse.get_GEO('GSE123456')

# Access metadata
print(f"Title: {gse.metadata['title'][0]}")
print(f"Samples: {len(gse.gsms)}")

# Get sample metadata
for gsm_name, gsm in gse.gsms.items():
    print(f"{gsm_name}: {gsm.metadata['title'][0]}")

# Get expression table
if gse.gpls:
    gpl_name = list(gse.gpls.keys())[0]
    expression_table = gse.pivot_samples('VALUE')

Download Options

Direct FTP Download

bash
# Download entire GSE
wget -r -np -nd ftp://ftp.ncbi.nlm.nih.gov/geo/series/GSE123nnn/GSE123456/

# Download specific file types
wget ftp://ftp.ncbi.nlm.nih.gov/geo/series/GSE123nnn/GSE123456/suppl/*counts*.txt.gz

Series Matrix Files

python
import gzip
import urllib.request

def download_series_matrix(gse):
    '''Download series matrix file'''
    gse_prefix = gse[:len(gse)-3] + 'nnn'
    url = f'https://ftp.ncbi.nlm.nih.gov/geo/series/{gse_prefix}/{gse}/matrix/{gse}_series_matrix.txt.gz'

    filename = f'{gse}_series_matrix.txt.gz'
    urllib.request.urlretrieve(url, filename)
    return filename

Common Errors

| Error | Cause | Solution | |-------|-------|----------| | Empty results | Wrong entry_type | Add gse[entry_type] or gds[entry_type] | | No FTPLink | Superseries or no data | Check if series has supplementary files | | No SRA link | Microarray data | SRA only for sequencing data |

Decision Tree

Need GEO expression data?
├── Looking for curated datasets?
│   └── Search gds with [entry_type]=gds
├── Looking for any experiment?
│   └── Search gds with [entry_type]=gse
├── Want RNA-seq specifically?
│   └── Add 'expression profiling by high throughput sequencing[gdstype]'
├── Have a publication?
│   └── Link pubmed -> gds
├── Need raw sequencing data?
│   └── Link gds -> sra, then use sra-data skill
├── Need processed expression matrix?
│   └── Download series matrix or use GEOparse
└── Need full metadata?
    └── Use GEOparse library

Related Skills

• entrez-search - General database searching
• entrez-link - Link GEO to SRA and other databases
• sra-data - Download raw sequencing data from linked SRA
• batch-downloads - Download multiple GEO records

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