package jalview.ext.ensembl;
import jalview.datamodel.AlignmentI;
import jalview.datamodel.Sequence;
import jalview.datamodel.SequenceFeature;
import jalview.datamodel.SequenceI;
import jalview.io.gff.SequenceOntology;
import jalview.util.MapList;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
/**
* A class that fetches genomic sequence and all transcripts for an Ensembl gene
*
* @author gmcarstairs
*/
public class EnsemblGene extends EnsemblSeqProxy
{
private static final EnsemblFeatureType[] FEATURES_TO_FETCH = {
EnsemblFeatureType.gene, EnsemblFeatureType.transcript,
EnsemblFeatureType.exon, EnsemblFeatureType.cds,
EnsemblFeatureType.variation };
@Override
public String getDbName()
{
return "ENSEMBL (GENE)";
}
@Override
protected EnsemblFeatureType[] getFeaturesToFetch()
{
return FEATURES_TO_FETCH;
}
@Override
protected EnsemblSeqType getSourceEnsemblType()
{
return EnsemblSeqType.GENOMIC;
}
/**
* Builds an alignment of all transcripts for the requested gene:
*
* - fetches the gene sequence
* - fetches features on the sequence
* - identifies "transcript" features whose Parent is the requested gene
* - fetches the transcript sequence for each transcript
* - makes a mapping from the gene to each transcript
* - copies features from gene to transcript sequences
* - fetches the protein sequence for each transcript, maps and saves it as
* a cross-reference
* - aligns each transcript against the gene sequence based on the position
* mappings
*
*/
@Override
public AlignmentI getSequenceRecords(String query) throws Exception
{
// TODO ? if an ENST identifier is supplied, convert to ENSG?
AlignmentI al = super.getSequenceRecords(query);
if (al.getHeight() > 0)
{
getTranscripts(al, query);
}
return al;
}
/**
* Constructs all transcripts for the gene, as identified by "transcript"
* features whose Parent is the requested gene. The coding transcript
* sequences (i.e. with introns omitted) are added to the alignment.
*
* @param al
* @param accId
* @throws Exception
*/
protected void getTranscripts(AlignmentI al, String accId)
throws Exception
{
SequenceI gene = al.getSequenceAt(0);
List transcriptFeatures = getTranscriptFeatures(accId,
gene);
for (SequenceFeature transcriptFeature : transcriptFeatures)
{
makeTranscript(transcriptFeature, al, gene);
}
}
/**
* Constructs a spliced transcript sequence by finding 'exon' features for the
* given id (or failing that 'CDS'). Copies features on to the new sequence.
* 'Aligns' the new sequence against the gene sequence by padding with gaps,
* and adds it to the alignment.
*
* @param transcriptFeature
* @param al
* the alignment to which to add the new sequence
* @param gene
* the parent gene sequence, with features
* @return
*/
SequenceI makeTranscript(SequenceFeature transcriptFeature,
AlignmentI al, SequenceI gene)
{
String accId = (String) transcriptFeature.getValue("transcript_id");
if (accId == null)
{
return null;
}
/*
* NB we are mapping from gene sequence (not genome), so do not
* need to check for reverse strand (gene and transcript sequences
* are in forward sense)
*/
/*
* make a gene-length sequence filled with gaps
* we will fill in the bases for transcript regions
*/
char[] seqChars = new char[gene.getLength()];
Arrays.fill(seqChars, al.getGapCharacter());
/*
* look for exon features of the transcript, failing that for CDS
* (for example ENSG00000124610 has 1 CDS but no exon features)
*/
String parentId = "transcript:" + accId;
List splices = findFeatures(gene,
SequenceOntology.EXON, parentId);
if (splices.isEmpty())
{
splices = findFeatures(gene, SequenceOntology.CDS, parentId);
}
int transcriptLength = 0;
final char[] geneChars = gene.getSequence();
int offset = gene.getStart(); // to convert to 0-based positions
List mappedFrom = new ArrayList();
for (SequenceFeature sf : splices)
{
int start = sf.getBegin() - offset;
int end = sf.getEnd() - offset;
int spliceLength = end - start + 1;
System.arraycopy(geneChars, start, seqChars, start, spliceLength);
transcriptLength += spliceLength;
mappedFrom.add(new int[] { sf.getBegin(), sf.getEnd() });
}
Sequence transcript = new Sequence(accId, seqChars, 1, transcriptLength);
transcript.createDatasetSequence();
al.addSequence(transcript);
/*
* transfer features to the new sequence; we use EnsemblCdna to do this,
* to filter out unwanted features types (see method retainFeature)
*/
List mapTo = new ArrayList();
mapTo.add(new int[] { 1, transcriptLength });
MapList mapping = new MapList(mappedFrom, mapTo, 1, 1);
new EnsemblCdna().transferFeatures(gene.getSequenceFeatures(),
transcript.getDatasetSequence(), mapping, parentId);
/*
* and finally fetch the protein product and save as a cross-reference
*/
addProteinProduct(transcript);
return transcript;
}
/**
* Returns a list of the transcript features on the sequence whose Parent is
* the gene for the accession id. Also removes all transcript features from
* the gene sequence, as we have no further need for them and they obscure
* more useful features on the display.
*
* @param accId
* @param geneSequence
* @return
*/
protected List getTranscriptFeatures(String accId,
SequenceI geneSequence)
{
List transcriptFeatures = new ArrayList();
List keptFeatures = new ArrayList();
String parentIdentifier = "gene:" + accId;
SequenceFeature[] sfs = geneSequence.getSequenceFeatures();
if (sfs != null)
{
for (SequenceFeature sf : sfs)
{
if (isTranscript(sf.getType()))
{
String parent = (String) sf.getValue(PARENT);
if (parentIdentifier.equals(parent))
{
transcriptFeatures.add(sf);
}
}
else
{
keptFeatures.add(sf);
}
}
}
SequenceFeature[] featuresRetained = keptFeatures.toArray(new SequenceFeature[keptFeatures.size()]);
geneSequence.getDatasetSequence().setSequenceFeatures(featuresRetained);
return transcriptFeatures;
}
@Override
public String getDescription()
{
return "Fetches all transcripts and variant features for a gene";
}
/**
* Default test query is a transcript
*/
@Override
public String getTestQuery()
{
return "ENSG00000157764"; // BRAF, 5 transcripts, reverse strand
// ENSG00000090266 // NDUFB2, 15 transcripts, forward strand
// ENSG00000101812 // H2BFM histone, 3 transcripts, forward strand
// ENSG00000123569 // H2BFWT histone, 2 transcripts, reverse strand
}
/**
* Answers true for a feature of type 'gene' (or a sub-type of gene in the
* Sequence Ontology), whose ID is the accession we are retrieving
*/
@Override
protected boolean identifiesSequence(SequenceFeature sf, String accId)
{
if (SequenceOntology.getInstance().isA(sf.getType(),
SequenceOntology.GENE))
{
String id = (String) sf.getValue(ID);
if (("gene:" + accId).equals(id))
{
return true;
}
}
return false;
}
/**
* Answers true unless feature type is 'gene', or 'transcript' with a parent
* which is a different gene. We need the gene features to identify the range,
* but it is redundant information on the gene sequence. Checking the parent
* allows us to drop transcript features which belong to different
* (overlapping) genes.
*/
@Override
protected boolean retainFeature(SequenceFeature sf, String accessionId)
{
if (SequenceOntology.getInstance().isA(sf.getType(),
SequenceOntology.GENE))
{
return false;
}
if (isTranscript(sf.getType()))
{
String parent = (String) sf.getValue(PARENT);
if (!("gene:" + accessionId).equals(parent))
{
return false;
}
}
return true;
}
/**
* Answers false. This allows an optimisation - a single 'gene' feature is all
* that is needed to identify the positions of the gene on the genomic
* sequence.
*/
@Override
protected boolean isSpliceable()
{
return false;
}
}