Gene ID Lookup & Nomenclature Reference

Gene ID Format Reference

Format	Example	Database	Description
Gene Symbol	`BRCA1`	HGNC	Official HGNC-approved human gene name — always uppercase, italicized in publications
Entrez Gene ID	`672`	NCBI Gene	Numeric identifier assigned by NCBI — stable, unique, used in many tools and databases
Ensembl Gene ID	`ENSG00000012048`	Ensembl	Stable gene identifier from Ensembl — ENSG prefix for human genes, includes version number
Ensembl Transcript ID	`ENST00000357654`	Ensembl	Identifies a specific transcript isoform — ENST prefix
UniProt ID	`P38398`	UniProt	Swiss-Prot/TrEMBL protein identifier — reviewed (Swiss-Prot) entries are most curated
RefSeq mRNA	`NM_007294`	NCBI	NCBI reference sequence for mRNA — NM_ prefix, followed by version number
RefSeq Protein	`NP_009225`	NCBI	NCBI reference sequence for protein — NP_ prefix
OMIM ID	`113705`	OMIM	Online Mendelian Inheritance in Man identifier — links gene to disease phenotypes
HGNC ID	`HGNC:1100`	HGNC	HUGO Gene Nomenclature Committee identifier — authoritative human gene naming body
MGI ID	`MGI:88190`	MGI	Mouse Genome Informatics — mouse gene ortholog identifier

Lookup Gene Information

Enter a gene symbol, Entrez ID, or Ensembl ID to search across multiple databases simultaneously.

Quick examples:

BRCA1 TP53 EGFR KRAS PTEN MYC APOE ACE2 FOXP2 HTT

Converting Between Gene ID Systems

Different tools and databases use different identifier systems. Here are the recommended resources for cross-database ID conversion:

Recommended Conversion Tools

NCBI Gene — Authoritative; links all ID types including Entrez, RefSeq, Ensembl, OMIM, HGNC
Ensembl BioMart — Bulk conversion of Ensembl IDs to/from Entrez, gene symbols, transcript/protein IDs
MyGene.info — REST API for programmatic gene ID conversion; supports batch queries
g:Convert (g:Profiler) — Converts gene IDs across species and ID types with enrichment analysis
R/Bioconductor: org.Hs.eg.db — Annotation package for human gene IDs with bitr() function (clusterProfiler)

Programmatic Example (Python)

import mygene
mg = mygene.MyGeneInfo()

# Convert gene symbol to Entrez ID
result = mg.query('BRCA1', scopes='symbol',
                  fields='entrezgene,ensembl.gene',
                  species='human')

# Bulk conversion
genes = ['BRCA1', 'TP53', 'EGFR', 'KRAS']
results = mg.querymany(genes,
    scopes='symbol',
    fields='entrezgene,ensembl.gene,uniprot',
    species='human')

HGNC Gene Symbol Nomenclature Guidelines

Human gene symbols follow strict conventions established by the HUGO Gene Nomenclature Committee (HGNC):

All uppercase, no spaces: BRCA1, TP53, EGFR

Italicized in publications: BRCA1, TP53

No leading digits: H3F3A (not 3H3FA)

Protein products: Non-italicized, not all-caps depending on convention: BRCA1 protein

Mouse orthologs: Only first letter uppercase: Brca1, Tp53

Gene families: Root symbol + number: CYP1A1, CYP1A2, CYP3A4

Pseudogenes: Root + "P" + number: BRCA1P1

microRNAs: MIR21, MIR155

Long non-coding RNAs: Often end in "-AS" (antisense), "-OT" (opposite strand), or use descriptive names

HGNC Symbol Approval: Gene symbols must be approved by HGNC to be official. The HGNC database at genenames.org is the authoritative source for approved human gene nomenclature.