Teloscope

Introduction

Teloscope is a comprehensive telomere annotation tool. It rapidly matches, counts, and reports telomeric repeats from genome assemblies (.fa) or (.fa.gz). Teloscope reports all these metrics in BED/BEDgraph files and produces a summary report. To install teloscope, use:

git clone https://github.com/vgl-hub/teloscope.git --recursive;
cd teloscope; 
make -j

Usage

teloscope -f input.[fa][.gz] -o [output/dir] -j [threads] -c [canonical] -p [patterns] -w [window size] -s [step size] -d [max-block-dist] -l [min-block-len]

Note: Teloscope automatically explores the input repeats and their reverse complements. If none are provided, it will scan for the canonical CCCTAA/TTAGGG repeats.

Examples

• Example: Minimal single case to run Teloscope.

    teloscope -f "${file}"
  

• Example: Multiple input case to run Teloscope.

    teloscope -f "${file}" -c TTAGGG -p TTAGGG,TCAGGG,TGAGGG,TTGGGG
  

• Example: Set window and step sizes. Calculating window metrics.

    teloscope -f "${file}" -o "${out_path}" -j 16 -c TTAGGG -p NNNGGG -w 2000 -s 1000 -g -e -r --verbose
  

• Example: Allowing all outputs and using all flags.

    teloscope -f "${file}" -o "${out_path}" -j 16 -c TTAGGG -p TBAGGG,TTRGGG,YTAGGG  -w 2000 -s 1000 -d 200 -l 1000 -r -g -e -m -i -t 50000 --verbose --cmd
  

Note: Teloscope accepts nucleotides in IUPAC format and generates all possible pattern combinations.

Parameters

To check out all options and flags, please use: teloscope -h

Required Parameters:
        '-f'    --input-sequence        Initiate tool with fasta file.
        '-o'    --output        Set output route. [Default: Input path]
        '-c'    --canonical     Set canonical pattern. [Default: TTAGGG]
        '-p'    --patterns      Set patterns to explore, separate them by commas [Default: TTAGGG]
        '-j'    --threads       Set maximum number of threads. [Default: max. available]
        '-t'    --terminal-limit        Set terminal limit for exploring telomere variant regions (TVRs). [Default: 50000]
        '-k'    --max-match-distance    Set maximum distance for merging matches. [Default: 50]
        '-d'    --max-block-distance    Set maximum block distance for extension. [Default: 200]
        '-l'    --min-block-length      Set minimum block length. [Default: 500]
        '-y'    --min-block-density     Set minimum block density. [Default: 0.5]

Optional Parameters:
        '-w'    --window        Set sliding window size. [Default: 1000]
        '-s'    --step  Set sliding window step. [Default: 500]
        '-r'    --out-win-repeats       Output canonical/noncanonical repeats and density by window. [Default: false]
        '-g'    --out-gc        Output GC content for each window. [Default: false]
        '-e'    --out-entropy   Output Shannon entropy for each window. [Default: false]
        '-m'    --out-matches   Output all canonical and terminal non-canonical matches. [Default: false]
        '-i'    --out-its       Output assembly interstitial telomere (ITSs) regions.[Default: false]
        '-u'    --ultra-fast    Ultra-fast mode. Only scans terminal telomeres at contig ends. [Default: true]
        '-v'    --version       Print current software version.
        '-h'    --help  Print current software options.
        --verbose       Verbose output.
        --cmd   Print command line.

Outputs

Teloscope outputs telomere annotations in BED format:

• terminal_telomeres.bed Annotation of the full telomere in the assembly. This is made of canonical and non-canonical repeats.

Additional optional outputs (Disabled with --ultra-fast):

• interstitial_telomeres.bed Blocks of adjacent canonical repeat matches. Outside of the ends, it represents interstitial telomeres (ITSs).
• window_metrics.bedgraph Tabulated file with calculated window metrics such as forward repeats, reverse repeats, canonical repeats, non-canonical repeats (-r), GC% (-g) and Shannon Entropy (-e) by window.
• canonical_matches.bed Coordinates of canonical repeats throughout the assembly.
• noncanonical_matches.bed Coordinates of non-canonical repeats in terminal regions of contigs.

How it works

Briefly, Teloscope reads an assembly and decomposes its parts. It uses prefix trees and sliding windows to efficiently perform multiple string matching and counting of telomeric repeats. It analyzes the informational properties of the sliding windows to find telomeric blocks. These blocks are collected, post-processed, and filtered according to their positional and conformational properties.

How to cite

Teloscope is part of the gfastar tool suite. If you use Teloscope in your research, please cite:

Gfastats: conversion, evaluation and manipulation of genome sequences using assembly graphs. Giulio Formenti, Linelle Abueg, Angelo Brajuka, Nadolina Brajuka, Cristo Gallardo, Alice Giani, Olivier Fedrigo, Erich D. Jarvis

doi: https://doi.org/10.1093/bioinformatics/btac460