def lowercase_below_qual_threshold(seq, qual, threshold):
''' Returns seq with characters made lowercase at any position for which
qual is below threshold.
'''
seq = list(seq)
qual = fastq.decode_sanger(qual)
for p, (s, q) in enumerate(zip(seq, qual)):
if q <= threshold:
seq[p] = s.lower()
return ''.join(seq)
def lowercase_below_qual_threshold(seq, qual, threshold):
''' Returns seq with characters made lowercase at any position for which
qual is below threshold.
'''
seq = list(seq)
qual = fastq.decode_sanger(qual)
for p, (s, q) in enumerate(zip(seq, qual)):
if q <= threshold:
seq[p] = s.lower()
return ''.join(seq)
def align_reads(
target_fasta_fn,
reads,
bam_fn,
min_path_length=15,
error_fn='/dev/null',
alignment_type='overlap',
):
''' Aligns reads to targets in target_fasta_fn by Smith-Waterman, storing
alignments in bam_fn and yielding unaligned reads.
'''
targets = {r.name: r.seq for r in fasta.reads(target_fasta_fn)}
target_names = sorted(targets)
target_lengths = [len(targets[n]) for n in target_names]
alignment_sorter = sam.AlignmentSorter(
target_names,
target_lengths,
bam_fn,
)
statistics = Counter()
with alignment_sorter:
for original_read in reads:
statistics['input'] += 1
alignments = []
rc_read = fastq.Read(
original_read.name,
utilities.reverse_complement(original_read.seq),
original_read.qual[::-1],
)
for read, is_reverse in ([original_read, False], [rc_read, True]):
qual = fastq.decode_sanger(read.qual)
for target_name, target_seq in targets.iteritems():
alignment = generate_alignments(read.seq, target_seq,
alignment_type)[0]
path = alignment['path']
if len(path) >= min_path_length and alignment['score'] / (
2. * len(path)) > 0.8:
aligned_segment = pysam.AlignedSegment()
aligned_segment.seq = read.seq
aligned_segment.query_qualities = qual
aligned_segment.is_reverse = is_reverse
char_pairs = make_char_pairs(path, read.seq,
target_seq)
cigar = sam.aligned_pairs_to_cigar(char_pairs)
clip_from_start = first_query_index(path)
if clip_from_start > 0:
cigar = [(sam.BAM_CSOFT_CLIP, clip_from_start)
] + cigar
clip_from_end = len(
read.seq) - 1 - last_query_index(path)
if clip_from_end > 0:
cigar = cigar + [
(sam.BAM_CSOFT_CLIP, clip_from_end)
]
aligned_segment.cigar = cigar
read_aligned, ref_aligned = zip(*char_pairs)
md = sam.alignment_to_MD_string(
ref_aligned, read_aligned)
aligned_segment.set_tag('MD', md)
aligned_segment.set_tag('AS', alignment['score'])
aligned_segment.tid = alignment_sorter.get_tid(
target_name)
aligned_segment.query_name = read.name
aligned_segment.next_reference_id = -1
aligned_segment.reference_start = first_target_index(
path)
alignments.append(aligned_segment)
if alignments:
statistics['aligned'] += 1
sorted_alignments = sorted(alignments,
key=lambda m: m.get_tag('AS'),
reverse=True)
grouped = utilities.group_by(sorted_alignments,
key=lambda m: m.get_tag('AS'))
_, highest_group = grouped.next()
primary_already_assigned = False
for alignment in highest_group:
if len(highest_group) == 1:
alignment.mapping_quality = 2
else:
alignment.mapping_quality = 1
if not primary_already_assigned:
primary_already_assigned = True
else:
alignment.is_secondary = True
alignment_sorter.write(alignment)
else:
statistics['unaligned'] += 1
yield read
with open(error_fn, 'w') as error_fh:
for key in ['input', 'aligned', 'unaligned']:
error_fh.write('{0}: {1:,}\n'.format(key, statistics[key]))
def trim_mismatches_from_start(mapping, region_fetcher, type_counts):
''' Remove all consecutive Q30+ mismatches from the beginning of alignments,
under the assumption that these represent untemplated additions during
reverse transcription.
Characterize the mismatches into type_counts.
'''
if sam.contains_indel_pysam(mapping) or mapping.is_unmapped:
set_nongenomic_length(mapping, 0)
return mapping
if mapping.is_reverse:
aligned_pairs = mapping.aligned_pairs[::-1]
index_lookup = utilities.base_to_complement_index
else:
aligned_pairs = mapping.aligned_pairs
index_lookup = utilities.base_to_index
decoded_qual = fastq.decode_sanger(mapping.qual)
bases_to_trim = 0
found_trim_point = False
first_ref_index = None
for read_index, ref_index in aligned_pairs:
if read_index == None:
# This shouldn't be able to be triggered since alignments
# containing indels are ruled out above.
continue
if mapping.is_reverse:
corrected_read_index = mapping.qlen - 1 - read_index
else:
corrected_read_index = read_index
ref_base = region_fetcher(mapping.tid, ref_index, ref_index + 1)
read_base = mapping.seq[read_index]
read_qual = decoded_qual[read_index]
coords = (
mapping.qlen,
corrected_read_index,
read_qual,
index_lookup[ref_base],
index_lookup[read_base],
)
type_counts[coords] += 1
if not found_trim_point:
if read_base != ref_base and read_qual >= 30:
bases_to_trim += 1
else:
first_ref_index = ref_index
found_trim_point = True
if first_ref_index == None:
raise ValueError('first_ref_index not set')
if bases_to_trim == 0:
trimmed_mapping = mapping
else:
trimmed_mapping = pysam.AlignedRead()
trimmed_mapping.qname = mapping.qname
trimmed_mapping.tid = mapping.tid
# first_ref_index has been set above to the be index of the
# reference base aligned to the first non-trimmed base in the
# read. If the mapping is forward, this will be the new pos.
# If the mapping is reverse, the pos won't change.
if mapping.is_reverse:
first_ref_index = mapping.pos
trimmed_mapping.pos = first_ref_index
trimmed_mapping.is_reverse = mapping.is_reverse
trimmed_mapping.is_secondary = mapping.is_secondary
trimmed_mapping.mapq = mapping.mapq
if mapping.is_reverse:
# bases_to_trim is never zero here, so there is no danger
# of minus zero
trimmed_slice = slice(None, -bases_to_trim)
else:
trimmed_slice = slice(bases_to_trim, None)
trimmed_mapping.seq = mapping.seq[trimmed_slice]
trimmed_mapping.qual = mapping.qual[trimmed_slice]
trimmed_mapping.rnext = -1
trimmed_mapping.pnext = -1
trimmed_length = len(mapping.seq) - bases_to_trim
if mapping.is_reverse:
# Remove blocks from the end
trimmed_cigar = sam.truncate_cigar_blocks_up_to(
mapping.cigar, trimmed_length)
else:
# Remove blocks from the beginning
trimmed_cigar = sam.truncate_cigar_blocks_from_beginning(
mapping.cigar, trimmed_length)
trimmed_mapping.cigar = trimmed_cigar
return trimmed_mapping
def combine_paired_mappings(R1_mapping, R2_mapping, verbose=False):
''' Takes two pysam mappings representing opposite ends of a fragment and
combines them into one mapping, (ab)using BAM_CREF_SKIP to bridge the gap
(if any) between them.
'''
R1_strand = sam.get_strand(R1_mapping)
if R1_strand == '+':
left_mapping, right_mapping = R1_mapping, R2_mapping
elif R1_strand == '-':
left_mapping, right_mapping = R2_mapping, R1_mapping
left_md = dict(left_mapping.tags)['MD']
right_md = dict(right_mapping.tags)['MD']
right_aligned_pairs = sam.cigar_to_aligned_pairs(
right_mapping.cigar, right_mapping.reference_start)
right_after_overlap_pair_index = len(right_aligned_pairs)
for i, (read, ref) in enumerate(right_aligned_pairs):
if ref != None and ref >= left_mapping.aend:
right_after_overlap_pair_index = i
break
right_overlap_pairs = right_aligned_pairs[:right_after_overlap_pair_index]
right_after_overlap_pairs = right_aligned_pairs[
right_after_overlap_pair_index:]
right_reads_after = [
read for read, ref in right_after_overlap_pairs
if read != None and read != 'N'
]
right_refs_after = [
ref for read, ref in right_after_overlap_pairs if ref != None
]
right_overlap_cigar = sam.aligned_pairs_to_cigar(right_overlap_pairs)
right_after_overlap_cigar = sam.aligned_pairs_to_cigar(
right_after_overlap_pairs)
right_after_overlap_md = sam.truncate_md_string_from_beginning(
right_md, len(right_refs_after))
right_after_overlap_read_start = len(
right_mapping.seq) - len(right_reads_after)
right_overlap_seq = right_mapping.seq[:right_after_overlap_read_start]
right_overlap_qual = right_mapping.qual[:right_after_overlap_read_start]
right_after_overlap_seq = right_mapping.seq[
right_after_overlap_read_start:]
right_after_overlap_qual = right_mapping.qual[
right_after_overlap_read_start:]
left_aligned_pairs = sam.cigar_to_aligned_pairs(
left_mapping.cigar, left_mapping.reference_start)
left_before_overlap_pair_index = -1
for i, (read, ref) in list(enumerate(left_aligned_pairs))[::-1]:
if ref != None and ref < right_mapping.pos:
left_before_overlap_pair_index = i
break
left_overlap_pairs = left_aligned_pairs[left_before_overlap_pair_index +
1:]
left_before_overlap_pairs = left_aligned_pairs[:
left_before_overlap_pair_index
+ 1]
left_reads_before = [
read for read, ref in left_before_overlap_pairs
if read != None and read != 'N'
]
left_refs_before = [
ref for read, ref in left_before_overlap_pairs if ref != None
]
left_overlap_cigar = sam.aligned_pairs_to_cigar(left_overlap_pairs)
left_before_overlap_cigar = sam.aligned_pairs_to_cigar(
left_before_overlap_pairs)
left_before_overlap_md = sam.truncate_md_string_up_to(
left_md, len(left_refs_before))
left_overlap_read_start = len(left_reads_before)
left_overlap_seq = left_mapping.seq[left_overlap_read_start:]
left_overlap_qual = left_mapping.qual[left_overlap_read_start:]
left_before_overlap_seq = left_mapping.seq[:left_overlap_read_start]
left_before_overlap_qual = left_mapping.qual[:left_overlap_read_start]
if left_overlap_pairs or right_overlap_pairs:
gap_length = 0
left_has_splicing = sam.contains_splicing(left_mapping)
right_has_splicing = sam.contains_splicing(right_mapping)
if left_overlap_cigar == right_overlap_cigar:
# If the two mappings agree about the location of indels in their overlap,
# use the seq from the mapping with the higher average quality in the
# overlap.
left_mean_qual = np.mean(fastq.decode_sanger(left_overlap_qual))
right_mean_qual = np.mean(fastq.decode_sanger(right_overlap_qual))
if left_mean_qual > right_mean_qual:
use_overlap_from = 'left'
else:
use_overlap_from = 'right'
elif left_has_splicing != right_has_splicing:
# A temporary(?) heuristic - if one read has splicing and the other
# doesn't, use the overlap from the one with splicing under the
# assumption that the other just has a few bases overhanging the
# splice junction.
if left_has_splicing:
use_overlap_from = 'left'
else:
use_overlap_from = 'right'
else:
# If the two mappings disagree about the location of indels in their overlap,
# we need a heuristic for picking which mapping we believe reflects the
# true structure of the input fragment. The most innocuous explanation
# is that a 'true' indel happened to lie close to the edge of one of the
# mappings. A more problematic situation is a 'false' indel (that is,
# produced during cluster generation or sequencing-by-synthesis, NOT
# template production). Our strategy is: realign the overlapping part of
# left mapping starting from the left edge of the overlap according to the
# cigar of the right mapping and realign the overlapping part of the right
# mapping starting from the right edge of the overlap according to the cigar
# of the left mapping. Count the number of mismatches produced by each.
# If the left overlap can accomodate the right cigar with fewer mismatches,
# use the right cigar and seq. If the right overlap can accomodate the left
# cigar with fewer mismatches, use the left cigar and seq.
# The leftmost aligned_pair from the right mapping is guaranteed by the
# mapping process to not involve a gap.
_, overlap_ref_start = right_overlap_pairs[0]
# Similarly, the rightmost aligned_pair from the left mapping can't be a
# gap.
_, overlap_ref_end = left_overlap_pairs[-1]
realigned_left_cigar = sam.truncate_cigar_blocks_up_to(
right_mapping.cigar, len(left_overlap_seq))
realigned_right_cigar = sam.truncate_cigar_blocks_from_beginning(
left_mapping.cigar, len(right_overlap_seq))
ref_dict = sam.merge_ref_dicts(
sam.ref_dict_from_mapping(left_mapping),
sam.ref_dict_from_mapping(right_mapping),
)
try:
left_using_right_mismatches = realigned_mismatches(
left_overlap_seq, overlap_ref_start, realigned_left_cigar,
ref_dict)
right_using_left_mismatches = realigned_mismatches_backwards(
right_overlap_seq, overlap_ref_end, realigned_right_cigar,
ref_dict)
except ValueError:
print left_mapping
print right_mapping
raise
if verbose:
logging.info('disagreements in {0}'.format(left_mapping.qname))
logging.info('left overlap cigar is {0}'.format(
str(left_overlap_cigar)))
logging.info('right overlap cigar is {0}'.format(
str(right_overlap_cigar)))
logging.info('left_using_right_mismatches - {0}'.format(
len(left_using_right_mismatches)))
logging.info('right_using_left_mismatches - {0}'.format(
len(right_using_left_mismatches)))
if len(left_using_right_mismatches) < len(
right_using_left_mismatches):
use_overlap_from = 'right'
elif len(right_using_left_mismatches) < len(
left_using_right_mismatches):
use_overlap_from = 'left'
else:
logging.info('disagreements in {0}'.format(left_mapping.qname))
logging.info('left overlap cigar is {0}'.format(
str(left_overlap_cigar)))
logging.info('right overlap cigar is {0}'.format(
str(right_overlap_cigar)))
logging.info('left_using_right_mismatches - {0}'.format(
len(left_using_right_mismatches)))
logging.info('right_using_left_mismatches - {0}'.format(
len(right_using_left_mismatches)))
logging.info('ambiguous disagreement')
return False
else:
gap_length = right_mapping.pos - left_mapping.aend
# It doesn't matter what use_overlap_from is set to; there is no overlap
use_overlap_from = 'left'
combined_mapping = pysam.AlignedRead()
combined_mapping.qname = left_mapping.qname
combined_mapping.tid = left_mapping.tid
combined_mapping.mapq = min(left_mapping.mapq, right_mapping.mapq)
combined_mapping.rnext = -1
combined_mapping.pnext = -1
combined_mapping.pos = left_mapping.pos
if R1_strand == '-':
combined_mapping.is_reverse = True
gap_cigar = [(sam.BAM_CREF_SKIP, gap_length)]
if use_overlap_from == 'left':
combined_mapping.seq = left_mapping.seq + right_after_overlap_seq
combined_mapping.qual = left_mapping.qual + right_after_overlap_qual
combined_mapping.cigar = left_mapping.cigar + gap_cigar + right_after_overlap_cigar
combined_md = sam.combine_md_strings(left_md, right_after_overlap_md)
combined_mapping.setTag('MD', combined_md)
overlap_seq_tag = right_overlap_seq
overlap_qual_tag = right_overlap_qual
elif use_overlap_from == 'right':
combined_mapping.seq = left_before_overlap_seq + right_mapping.seq
combined_mapping.qual = left_before_overlap_qual + right_mapping.qual
combined_mapping.cigar = left_before_overlap_cigar + gap_cigar + right_mapping.cigar
combined_md = sam.combine_md_strings(left_before_overlap_md, right_md)
combined_mapping.setTag('MD', combined_md)
overlap_seq_tag = left_overlap_seq
overlap_qual_tag = left_overlap_qual
if len(overlap_seq_tag) > 0:
# Having empty tags causes problems, so don't create them.
combined_mapping.setTag('Xs', overlap_seq_tag)
combined_mapping.setTag('Xq', overlap_qual_tag)
combined_mapping.setTag('Xw', use_overlap_from)
return combined_mapping
def collapseUMIs(reads, readThres, outfile):
# collpase reads assuming cellBC and UMI are true
# identifies consensus sequence and reports as sequence for each cellBC-UMI combination
numReadsQualFilt = 0
UMIGrps = {}
for r in reads: # itertools.islice(reads,10000):
avgQ50 = np.mean(fastq.decode_sanger(r.qual[0:50]))
if avgQ50 < 20:
numReadsQualFilt = numReadsQualFilt + 1
continue
n = r.name.split('_')
cellGroup = n[1] + "_" + n[2]
readcount = int(n[3])
if cellGroup in UMIGrps:
[seqs, counts] = UMIGrps[cellGroup]
seqs.append(r.seq)
counts.append(readcount)
else:
UMIGrps[cellGroup] = [[r.seq], [readcount]]
print("# of cell-UMI groups: " + str(len(UMIGrps)) + " (includes <" +
str(readThres) + ")")
read_dist = []
for u in UMIGrps:
[seqs, counts] = UMIGrps[u]
read_dist.append(sum(counts))
h = plt.figure(figsize=(14, 10))
ax = plt.hist(read_dist, log=True)
plt.ylabel("Frequency")
plt.xlabel("Number of Reads")
plt.title("Reads Per UMI")
plt.savefig("collapsedUMIs_reads_per_umi.init.png")
plt.close()
readThresh = np.percentile(read_dist, 99) / 10
print("Filtering out UMIs with less than " + str(readThresh) + " reads")
fh = open(outfile, 'w')
fh.write("cellBC\tUMI\treadCount\tconsensusSeq\n")
numBelowReadThres = 0
numMaj = 0
numCon = 0
numSingles = 0
counter = 1
for k in UMIGrps: # each UMI group consists of reads from the same molecule
[seqs, counts] = UMIGrps[k]
grpSize = sum(counts)
if grpSize < readThres: # too few reads to include
numBelowReadThres = numBelowReadThres + 1
continue
n = k.split("_")
if len(seqs) == 1: # trivial case added 9/11/2017
numSingles = numSingles + 1
fh.write("\t".join([str(n[0]),
str(n[1]),
str(counts[0]), seqs[0]]) + "\n")
else:
#
# Update 9/1/2017: try to improve speeds by increasing the number of same reads to feed
# into majority instead of consensus finding
# trim to length of 25th percentile read ranked by length
#
s1 = pd.DataFrame({"seq": seqs, "readCount": counts})
s1["seqLen"] = s1["seq"].str.len()
s1 = s1.sort_values("seqLen").reset_index(
drop=True) # sorts reads by length in ascending
totalReads = s1["readCount"].sum()
cReads = s1["readCount"].cumsum() # cumulative
rPctile = 0.3 * totalReads # 30th percentile
rPctileIndex = cReads[cReads >= rPctile].index[
0] # index of seq length
sLen = s1.loc[rPctileIndex, "seqLen"]
s1["seq"] = s1["seq"].str[0:sLen]
s2 = s1.groupby(["seq"]).agg({
"readCount": np.sum
}).sort_values("readCount", ascending=False) # indexed by seq
grpProp = s2.loc[s2.index[0], "readCount"] / float(totalReads)
if grpProp > .50:
consensusSeq = s2.index[0]
numMaj = numMaj + 1
else:
consensusSeq = get_consensus(s2.index.tolist(),
s2["readCount"].tolist())
numCon = numCon + 1
# print Entry
fh.write("\t".join([
str(n[0]), str(n[1]),
str(totalReads), consensusSeq
]) + "\n")
counter = counter + 1
if counter % 1000 == 0:
print(str(counter) + " groups processed...")
fh.close()
print("# of cell-UMI groups = " + str(len(UMIGrps)))
print("# reads qual <20 (filtered) = " + str(numReadsQualFilt))
print("# grps w/ reads<" + str(readThres) + " = " + str(numBelowReadThres))
print("# grps singles = " + str(numSingles))
print("# grps >0.5 = " + str(numMaj))
print("# grps concensus = " + str(numCon))
def trim_mismatches_from_start(mapping, region_fetcher, type_counts):
''' Remove all consecutive Q30+ mismatches from the beginning of alignments,
under the assumption that these represent untemplated additions during
reverse transcription.
Characterize the mismatches into type_counts.
'''
if sam.contains_indel_pysam(mapping) or mapping.is_unmapped:
set_nongenomic_length(mapping, 0)
return mapping
if mapping.is_reverse:
aligned_pairs = mapping.aligned_pairs[::-1]
index_lookup = utilities.base_to_complement_index
else:
aligned_pairs = mapping.aligned_pairs
index_lookup = utilities.base_to_index
decoded_qual = fastq.decode_sanger(mapping.qual)
bases_to_trim = 0
found_trim_point = False
first_ref_index = None
for read_index, ref_index in aligned_pairs:
if read_index == None:
# This shouldn't be able to be triggered since alignments
# containing indels are ruled out above.
continue
if mapping.is_reverse:
corrected_read_index = mapping.qlen - 1 - read_index
else:
corrected_read_index = read_index
ref_base = region_fetcher(mapping.tid, ref_index, ref_index + 1)
read_base = mapping.seq[read_index]
read_qual = decoded_qual[read_index]
coords = (mapping.qlen,
corrected_read_index,
read_qual,
index_lookup[ref_base],
index_lookup[read_base],
)
type_counts[coords] += 1
if not found_trim_point:
if read_base != ref_base and read_qual >= 30:
bases_to_trim += 1
else:
first_ref_index = ref_index
found_trim_point = True
if first_ref_index == None:
raise ValueError('first_ref_index not set')
if bases_to_trim == 0:
trimmed_mapping = mapping
else:
trimmed_mapping = pysam.AlignedRead()
trimmed_mapping.qname = mapping.qname
trimmed_mapping.tid = mapping.tid
# first_ref_index has been set above to the be index of the
# reference base aligned to the first non-trimmed base in the
# read. If the mapping is forward, this will be the new pos.
# If the mapping is reverse, the pos won't change.
if mapping.is_reverse:
first_ref_index = mapping.pos
trimmed_mapping.pos = first_ref_index
trimmed_mapping.is_reverse = mapping.is_reverse
trimmed_mapping.is_secondary = mapping.is_secondary
trimmed_mapping.mapq = mapping.mapq
if mapping.is_reverse:
# bases_to_trim is never zero here, so there is no danger
# of minus zero
trimmed_slice = slice(None, -bases_to_trim)
else:
trimmed_slice = slice(bases_to_trim, None)
trimmed_mapping.seq = mapping.seq[trimmed_slice]
trimmed_mapping.qual = mapping.qual[trimmed_slice]
trimmed_mapping.rnext = -1
trimmed_mapping.pnext = -1
trimmed_length = len(mapping.seq) - bases_to_trim
if mapping.is_reverse:
# Remove blocks from the end
trimmed_cigar = sam.truncate_cigar_blocks_up_to(mapping.cigar, trimmed_length)
else:
# Remove blocks from the beginning
trimmed_cigar = sam.truncate_cigar_blocks_from_beginning(mapping.cigar, trimmed_length)
trimmed_mapping.cigar = trimmed_cigar
return trimmed_mapping
