Gene / Protein ID Lookup

Resolve accessions to gene symbols across biological databases. Add new databases as we encounter them.

When to Use

• Tree tip labels contain accessions instead of gene symbols (e.g., tr|Q9R1A3|...)
• Need gene names for model species in a phylogenetic tree
• Building an accession_gene_map.tsv for the tree-formatting skill
• Any analysis where you have protein/gene IDs and need readable gene symbols

Quick ID Detection

Identify the database from the accession pattern:

General Workflow

1. Identify which accession types are present — inspect labels, match patterns above
2. Swiss-Prot entries (sp|) already have gene names embedded — parse directly from the label: sp|O95631|NET1_HUMAN → gene = NET1
3. Other entries need API lookup — batch-query the appropriate database (see below)
4. Save results to TSV — accession_gene_map.tsv with columns: accession, gene_name (and optionally database, species)
5. Load TSV in downstream scripts — tree-formatting templates read this file

Database: UniProt

ID patterns

• sp|ACC|GENE_SPECIES or tr|ACC|ACC_SPECIES in tip labels
• Bare accessions: 6-10 alphanumeric (e.g., Q9R1A3, A0A8C1NMY5)

Lookup

• sp| entries: gene name embedded in label — parse directly, no API needed
• tr| entries and bare accessions: REST API batch query

# Batch up to ~200 accessions per request
query_str <- paste0("(", paste0("accession:", accessions, collapse = " OR "), ")")
url <- paste0(
  "https://rest.uniprot.org/uniprotkb/search?",
  "query=", URLencode(query_str, reserved = TRUE),
  "&fields=accession,gene_primary&format=tsv&size=500"
)
result <- read.delim(url(url), stringsAsFactors = FALSE)
# Columns: "Entry" (accession), "Gene.Names..primary." (gene symbol)

UniProt ID Mapping Service

For cross-database conversions (e.g., FBgn → UniProt, WBGene → UniProt):

• POST to https://rest.uniprot.org/idmapping/run with from, to, ids
• Poll https://rest.uniprot.org/idmapping/status/{jobId}
• Supports from=FlyBase, from=WormBase, to=UniProtKB
• Up to 100,000 IDs per job

Notes

• Rate limit: ~100 requests/minute
• For >500 accessions, paginate or split into multiple queries

Database: Ensembl

ID patterns

ENS + optional species code + feature type letter + 11 digits.

Ensembl Metazoa species (Amphimedon, Nematostella, etc.) use the same REST API.

Lookup

Base URL: https://rest.ensembl.org

Gene IDs → symbol (1 batch call):

• POST /lookup/id with {"ids": ["ENSG...", ...]} (max 1000 per request)
• Gene symbol is in display_name field

Protein IDs → symbol (2 batch calls): Protein (Translation) objects have NO display_name. Must chain through parents:

1. POST protein IDs → get Parent transcript IDs
2. POST transcript IDs → get display_name (format: GENE-NNN, e.g., BRCA2-201)
3. Strip isoform suffix: sub("-\\d+$", "", display_name)

# Batch POST (up to 1000 IDs)
resp <- httr2::request("https://rest.ensembl.org") |>
  httr2::req_url_path("lookup", "id") |>
  httr2::req_headers("Content-Type" = "application/json",
                     "Accept" = "application/json") |>
  httr2::req_body_json(list(ids = id_vector)) |>
  httr2::req_perform()
results <- httr2::resp_body_json(resp)

Gotchas

• Protein IDs return no gene symbol — must chain through Parent transcript
• expand=1 fails on protein IDs — returns null
• Batch returns null for unknown IDs — handle gracefully
• Rate limit: 55,000 requests/hour (no API key needed)
• Both versioned (ENSG...19) and unversioned IDs accepted

Database: FlyBase

ID patterns

FBgn, FBpp, FBtr + 7-digit zero-padded number (e.g., FBgn0000490).

Lookup

Best approach: FlyBase precomputed bulk file (not the API — it lacks ID-to-symbol endpoints and is unreliable).

For FBgn only — lightweight file:

https://s3ftp.flybase.org/releases/current/precomputed_files/genes/fbgn_annotation_ID_fb_YYYY_NN.tsv.gz

Columns: gene_symbol, organism_abbreviation, primary_FBgn#, ...

For FBgn, FBtr, AND FBpp — expanded file (needed for polypeptide IDs):

https://s3ftp.flybase.org/releases/current/precomputed_files/genes/fbgn_fbtr_fbpp_expanded_fb_YYYY_NN.tsv.gz

Columns: gene_ID, gene_symbol, transcript_ID, polypeptide_ID, ... ~36K rows. Download once, cache locally.

R/Bioconductor alternative (FBgn only):

library(org.Dm.eg.db)
symbols <- AnnotationDbi::mapIds(org.Dm.eg.db,
  keys = fbgn_ids, column = "SYMBOL", keytype = "FLYBASE")

Use keytype = "FLYBASE" (not "ENSEMBL") for FBgn IDs.

UniProt ID mapping also works for FBgn → gene symbol (via from=FlyBase, to=UniProtKB), but does NOT work for FBpp or FBtr.

Gotchas

• FlyBase REST API has no ID-to-symbol endpoint — use bulk files instead
• Dmel\ prefix: FlyBase uses species prefixes for non-melanogaster genes (e.g., Dvir\Dfd). In UniProt, Drosophila gene names sometimes carry Dmel\ prefix — strip with sub("^Dmel\\\\", "", gene)
• Case conventions: lowercase initial = recessive phenotype (e.g., dpp), uppercase initial = dominant or molecular function (e.g., Abd-B)
• Bulk files update ~6x/year — current URL alias always points to latest

Database: WormBase

ID patterns

• Gene: WBGene + 8-digit zero-padded number (e.g., WBGene00006763)
• Protein: CE + digits (e.g., CE28580)
• Sequence names (cosmid-based): e.g., JC8.10, C15F1.7

Lookup

Best approach: WormBase ParaSite REST API (has batch support, works for all nematode species).

POST https://parasite.wormbase.org/rest-19/lookup/id
Content-Type: application/json
Accept: application/json

{"ids": ["WBGene00006763", "WBGene00004930"]}

• Max 1000 IDs per request
• Gene symbol is in display_name field (e.g., unc-26, sod-1)
• Use versioned URL (rest-19) or follow 307 redirect from /rest/

For richer per-gene data (aliases, descriptions), use the WormBase REST API:

GET https://rest.wormbase.org/rest/field/gene/WBGene00006763/name

Returns data.label = gene symbol. No batch support — single-gene queries only.

Gotchas

• C. elegans naming: 3-4 lowercase letters + hyphen + number (e.g., unc-26, spc-1). Letter prefix is the "gene class" from mutant phenotype
• Genes without standard names use cosmid/sequence names (e.g., JC8.10)
• UniProt ID mapping (from=WormBase) works for WBGene IDs but is a multi-step process — ParaSite is simpler
• from=WBParaSite does NOT work with WBGene IDs in UniProt ID mapping

Database: NCBI / RefSeq

ID patterns

PREFIX_DIGITS.VERSION:

Both versioned and unversioned forms accepted by NCBI APIs.

Lookup

Best approach: NCBI Datasets API (single GET, clean JSON — much simpler than E-utilities).

GET https://api.ncbi.nlm.nih.gov/datasets/v2/gene/accession/{comma_separated_accessions}

• Gene symbol in reports[].gene.symbol
• Also returns gene_id, description, taxname
• Batch: comma-separate accessions in URL (~400 per request due to URL length)
• Accepts XP_, NP_, XM_, NM_ directly

url <- paste0(
  "https://api.ncbi.nlm.nih.gov/datasets/v2/gene/accession/",
  paste(accessions, collapse = ",")
)
resp <- httr2::request(url) |>
  httr2::req_headers(Accept = "application/json") |>
  httr2::req_perform()
body <- httr2::resp_body_json(resp)
# body$reports[[i]]$gene$symbol

Gotchas

• Use Datasets API, not E-utilities — E-utilities requires multiple steps (ESearch → ELink → ESummary) and XML parsing
• Rate limits: 5 req/sec without API key, 10 req/sec with key
• API key: register at https://account.ncbi.nlm.nih.gov/settings/, pass via ?api_key=KEY parameter
• Non-model organisms may return LOC + number as gene symbol (e.g., LOC5512993 for Nematostella) — this means no official symbol assigned

Output Format

All lookups should produce a TSV file (accession_gene_map.tsv) with at minimum:

accession	gene_name
Q9R1A3	Sptbn1
Q23158	unc-70
Q9VZU3	betaSpec
XP_032238380.2	LOC5512993

Optional extra columns: database, species, gene_id.

The tree-formatting templates load this file automatically:

gene_map <- read.delim(file.path(out_dir, "accession_gene_map.tsv"))
acc_to_gene <- setNames(gene_map$gene_name, gene_map$accession)

Related Skills

• tree-formatting: Consumes gene_map TSV for tip labeling
• protein-phylogeny: May produce trees with mixed accession formats