path: root/academic/spidey/spidey.1

.TH SPIDEY 1 2005-01-25 NCBI "NCBI Tools User's Manual"
.SH NAME
spidey \- align mRNA sequences to a genome
.SH SYNOPSIS
.B spidey
[\|\fB\-\fP\|]
[\|\fB\-F\fP\ \fIN\fP\|]
[\|\fB\-G\fP\|]
[\|\fB\-L\fP\ \fIN\fP\|]
[\|\fB\-M\fP\ \fIfilename\fP\|]
[\|\fB\-N\fP\ \fIfilename\fP\|]
[\|\fB\-R\fP\ \fIfilename\fP\|]
[\|\fB\-S\fP\ \fIp/m\fP\|]
[\|\fB\-T\fP\ \fIN\fP\|]
[\|\fB\-X\fP\|]
[\|\fB\-a\fP\ \fIfilename\fP\|]
[\|\fB\-c\fP\ \fIN\fP\|]
[\|\fB\-d\fP\|]
[\|\fB\-e\fP\ \fIX\fP\|]
[\|\fB\-f\fP\ \fIX\fP\|]
[\|\fB\-g\fP\ \fIX\fP\|]
\fB\-i\fP\ \fIfilename\fP
[\|\fB\-j\fP\|]
[\|\fB\-k\fP\ \fIfilename\fP\|]
[\|\fB\-l\fP\ \fIN\fP\|]
\fB\-m\fP\ \fIfilename\fP
[\|\fB\-n\fP\ \fIN\fP\|]
[\|\fB\-o\fP\ \fIstr\fP\|]
[\|\fB\-p\fP\ \fIN\fP\|]
[\|\fB\-r\fP\ \fIc/d/m/p/v\fP\|]
[\|\fB\-s\fP\|]
[\|\fB\-t\fP\ \fIfilename\fP\|]
[\|\fB\-u\fP\|]
[\|\fB\-w\fP\|]
.SH DESCRIPTION
\fBspidey\fP is a tool for aligning one or more mRNA sequences to a
given genomic sequence.  \fBspidey\fP was written with two main goals
in mind: find good alignments regardless of intron size; and avoid
getting confused by nearby pseudogenes and paralogs.  Towards the
first goal, \fBspidey\fP uses BLAST and Dot View (another local
alignment tool) to find its alignments; since these are both local
alignment tools, \fBspidey\fP does not intrinsically favor shorter or
longer introns and has no maximum intron size.  To avoid mistakenly
including exons from paralogs and pseudogenes, \fBspidey\fP first
defines windows on the genomic sequence and then performs the
mRNA-to-genomic alignment separately within each window.  Because of
the way the windows are constructed, neighboring paralogs or
pseudogenes should be in separate windows and should not be included
in the final spliced alignment.
.SS Initial alignments and construction of genomic windows
\fBspidey\fP takes as input a single genomic sequence and a set of
mRNA accessions or FASTA sequences.  All processing is done one mRNA
sequence at a time.  The first step for each mRNA sequence is a
high-stringency BLAST against the genomic sequence.  The resulting
hits are analyzed to find the genomic windows.
.PP
The BLAST alignments are sorted by score and then assigned into
windows by a recursive function which takes the first alignment and
then goes down the alignment list to find all alignments that are
consistent with the first (same strand of mRNA, both the mRNA and
genomic coordinates are nonoverlapping and linearly consistent).  On
subsequent passes, the remaining alignments are examined and are put
into their own nonoverlapping, consistent windows, until no alignments
are left.  Depending on how many gene models are desired, the
top \fIn\fP windows are chosen to go on to the next step and the others
are deleted.
.SS Aligning in each window
Once the genomic windows are constructed, the initial BLAST alignments
are freed and another BLAST search is performed, this time with the
entire mRNA against the genomic region defined by the window, and at a
lower stringency than the initial search.  \fBspidey\fP then uses a
greedy algorithm to generate a high-scoring, nonoverlapping subset of
the alignments from the second BLAST search.  This consistent set is
analyzed carefully to make sure that the entire mRNA sequence is
covered by the alignments.  When gaps are found between the
alignments, the appropriate region of genomic sequence is searched
against the missing mRNA, first using a very low-stringency BLAST and,
if the BLAST fails to find a hit, using DotView functions to locate
the alignment.  When gaps are found at the ends of the alignments, the
BLAST and DotView searches are actually allowed to extend past the
boundaries of the window.  If the 3' end of the mRNA does not align
completely, it is first examined for the presence of a poly(A) tail.
No attempt is made to align the portion of the mRNA that seems to be a
poly(A) tail; sometimes there is a poly(A) tail that does align to the
genomic sequence, and these are noted because they indicate the
possibility of a pseudogene.
.PP
Now that the mRNA is completely covered by the set of alignments, the
boundaries of the alignments (there should be one alignment per exon
now) are adjusted so that the alignments abut each other precisely and
so that they are adjacent to good splice donor and acceptor sites.
Most commonly, two adjacent exons' alignments overlap by as much as 20
or 30 base pairs on the mRNA sequence.  The true exon boundary may lie
anywhere within this overlap, or (as we have seen empirically) even a
few base pairs outside the overlap.  To position the exon boundaries,
the overlap plus a few base pairs on each side is examined for splice
donor sites, using functions that have different splice matrices
depending on the organism chosen.  The top few splice donor sites (by
score) are then evaluated as to how much they affect the original
alignment boundaries.  The site that affects the boundaries the least
is chosen, and is evaluated as to the presence of an acceptor site.
The alignments are truncated or extended as necessary so that they
terminate at the splice donor site and so that they do not overlap.
.SS Final result
The windows are examined carefully to get the percent identity per
exon, the number of gaps per exon, the overall percent identity, the
percent coverage of the mRNA, presence of an aligning or non-aligning
poly(A) tail, number of splice donor sites and the presence or absence
of splice donor and acceptor sites for each exon, and the occurrence
of an mRNA that has a 5' or 3' end (or both) that does not align to
the genomic sequence.  If the overall percent identity and percent
length coverage are above the user-defined cutoffs, a summary report
is printed, and, if requested, a text alignment showing identities and
mismatches is also printed.
.SS Interspecies alignments
\fBspidey\fP is capable of performing interspecies alignments.  The
major difference in interspecies alignments is that the mRNA-genomic
identity will not be close to 100% as it is in intraspecies
alignments; also, the alignments have numerous and lengthy gaps.  If
\fBspidey\fP is used in its normal mode to do interspecies alignments,
it produces gene models with many, many short exons.  When the
interspecies flag is set, \fBspidey\fP uses different BLAST parameters
to encourage longer and more gaps and to not penalize as heavily for
mismatches.  This way, the alignments for the exons are much longer
and more closely approximate the actual gene structure.
.SS Extracting CDS alignments
When \fBspidey\fP is run in network-aware mode or when ASN.1 files are
used for the mRNA records, it is capable of extracting a CDS alignment
from an mRNA alignment and printing the CDS information also.  Since
the CDS alignment is just a subset of the mRNA alignment, it is
relatively straightforward to truncate the exon alignments as
necessary and to generate a CDS alignment.  Furthermore, the
untranslated regions are now defined, so the percent identity for the
5' and 3' untranslated regions is also calculated.
.PP
.SH OPTIONS
A summary of options is included below.
.TP
\fB\-\fP
Print usage message.
.TP
\fB\-F\fP\ \fIN\fP
Start of genomic interval desired (from; 0-based).
.TP
\fB\-G\fP
Input file is a GI list.
.TP
\fB\-L\fP\ \fIN\fP
The extra-large intron size to use (default = 220000).
.TP
\fB\-M\fP\ \fIfilename\fP
File with donor splice matrix.
.TP
\fB\-N\fP\ \fIfilename\fP
File with acceptor splice matrix.
.TP
\fB\-R\fP\ \fIfilename\fP
File (including path) to repeat blast database for filtering.
.TP
\fB\-S\fP\ \fIp/m\fP
Restrict to plus (p) or minus (m) strand of genomic sequence.
.TP
\fB\-T\fP\ \fIN\fP
Stop of genomic interval desired (to; 0-based).
.TP
\fB\-X\fP
Use extra-large intron sizes (increases the limit for initial and
terminal introns from 100kb to 240kb and for all others from 35kb to
120kb); may result in significantly longer compute times.
.TP
\fB\-a\fP\ \fIfilename\fP
Output file for alignments when directed to a separate file with
\fB-p\ 3\fP (default = spidey.aln).
.TP
\fB\-c\fP\ \fIN\fP
Identity cutoff, in percent, for quality control purposes.
.TP
\fB\-d\fP
Also try to align coding sequences corresponding to the given mRNA
records (may require network access).
.TP
\fB\-e\fP\ \fIX\fP
First-pass e-value (default = 1.0e-10).  Higher values increase speed
at the cost of sensitivity.
.TP
\fB\-f\fP\ \fIX\fP
Second-pass e-value (default = 0.001).
.TP
\fB\-g\fP\ \fIX\fP
Third-pass e-value (default = 10).
.TP
\fB\-i\fP\ \fIfilename\fP
Input file containing the genomic sequence in ASN.1 or FASTA format.
If your computer is running on a network that can access GenBank, you
can substitute the desired accession number for the filename.
.TP
\fB\-j\fP
Print ASN.1 alignment?
.TP
\fB\-k\fP\ \fIfilename\fP
File for ASN.1 output with \fB-k\fP (default = spidey.asn).
.TP
\fB\-l\fP\ \fIN\fP
Length coverage cutoff, in percent.
.TP
\fB\-m\fP\ \fIfilename\fP
Input file containing the mRNA sequence(s) in ASN.1 or FASTA format,
or a list of their accessions (with \fB-G\fP).  If your computer is
running on a network that can access GenBank, you can substitute a
single accession number for the filename.
.TP
\fB\-n\fP\ \fIN\fP
Number of gene models to return per input mRNA (default = 1).
.TP
\fB\-o\fP\ \fIstr\fP
Main output file (default = stdout; contents controlled by \fB-p\fP).
.TP
\fB\-p\fP\ \fIN\fP
Print alignment?
.RS
.PD 0
.IP \fB0\fP
summary and alignments together (default)
.IP \fB1\fP
just the summary
.IP \fB2\fP
just the alignments
.IP \fB3\fP
summary and alignments in different files
.PD
.RE
.TP
\fB\-r\fP\ \fIc/d/m/p/v\fP
Organism of genomic sequence, used to determine splice matrices.
.RS
.PD 0
.IP \fBc\fP
C. elegans
.IP \fBd\fP
Drosophila
.IP \fBm\fP
Dictyostelium discoideum
.IP \fBp\fP
plant
.IP \fBv\fP
vertebrate (default)
.PD
.RE
.TP
\fB\-s\fP
Tune for interspecies alignments.
.TP
\fB\-t\fP\ \fIfilename\fP
File with feature table, in 4 tab-delimited columns:
.RS
.PD 0
.IP \fIseqid\fP
(e.g., \fBNM_04377.1\fP)
.IP \fIname\fP
(only \fBrepetitive_region\fP is currently supported)
.IP \fIstart\fP
(0-based)
.IP \fIstop\fP
(0-based)
.PD
.RE
.TP
\fB\-u\fP
Make a multiple alignment of all input mRNAs (which must overlap on
the genomic sequence).
.TP
\fB\-w\fP
Consider lowercase characters in input FASTA sequences to be masked.
.SH AUTHOR
Sarah Wheelan and others at the National Center for Biotechnology
Information; Steffen Moeller contributed to this documentation.
.SH SEE ALSO
.BR blast (1),
<http://www.ncbi.nlm.nih.gov/spidey>