centroFlye

UPD May 24, 2021: The latest version of cenX and cen6 assemblies in CHM13 cell line are available as a part of a complete assembly of a human genome generated by the Telomere-to-Telomere Consortium (github). Assemblies described below should be considered interim versions and are deprecated.

---

Disclaimer: To replicate the assemblies from the Nature Biotechnology paper (see Publications), please consider branch cF_NatBiotech_paper_Xv0.8.3-6v0.1.3. The version of centroFlye (and the corresponding assemblies) in master branch can be more recent.

Version 0.8.3 cenX + 0.1.3 cen6

Overview

centroFlye (Bzikadze et al., 2020) is an algorithm for centromere assembly using long error-prone reads. Currently it supports assembly of a human centromere 6 (referred to as cen6) and X (referred to as cenX). Here we show how to apply it for the cen6 and cenX of the CHM13hTERT human cell line. The comparison of various cenX assemblies can be found in Bzikadze et al., 2020 and Mikheenko et al., 2020.

Cloning

Please, clone the repository with submodules:

git clone --recurse-submodules --single-branch --branch cF_NatBiotech_paper_Xv0.8.3-6v0.1.3 git@github.com:seryrzu/centroFlye.git

Dependencies

• C++ 14
• Python 3.6

Python packages:

• biopython (tested on version 1.70)
• click (tested on version 7.0)
• joblib (tested on version 0.14.1)
• matplotlib (tested on version 3.0.2)
• networkx (tested on version 2.2)
• numpy (tested on version 1.16.1)
• plotly (tested on version 4.4.1)
• pydot (tested on version 1.4.1)
• python-edlib (tested on version 1.2.4.post1)
• python-slugify (tested on version 4.0.0)
• regex (tested on version 2.4.104)

Required python packages can be installed through Conda with conda install --file requirements.txt.

External software

• Flye (v2.5, tested on commit: 315122d2ff58025aa4c38227239f431490b557ac)
• Noise Cancelling Repeat Finder (NCRF) (Tested on commit : 758206f1689ad1338cf7a841482dbf12548c337a)

Please note that all external software has to be in your PATH. Specifically binaries flye and NCRF have to be in PATH.

Data

• <path_to_CHM13> — path where the T2T ONT reads are located (rel2, Guppy flip-flop 2.3.1, used for cenX assembly and can be downloaded from here; rel3, Guppy flip-flop 3.1.5, is used for cen6 assembly and can be downloaded from here ; also see github). The data is described in Miga, Koren et al., 2020.

Availability

The assemblies produced by the version of centroFlye in this branch are presented in the Nature Biotechnology paper (see Publications). These assemblies and all intermediate results of the pipeline described below are published at ZENODO. For the latest versions of any assemblies produced by centroFlye please consult the master branch.

Quick start guide for cenX (centroFlye)

If you want to run the whole centroFlye pipeline to generate cenX assembly with one command, please run

./run_all_cenX.sh <path_to_CHM13> results_cenX 50

You can customize the output directory and the number of threads:

./run_all_cenX.sh <path_to_CHM13> <output directory> <number of threads>

All intermediate and final results will then be placed in <output directory>. If you want to start from scratch you can simply remove this directory.

Required resources:

• Storage space: ~150GB (mostly from the first step "Recruitment of centromeric reads", see below)
• Clock time: ~9 hours (mostly recruitment of unique k-mers)
• RAM: peak usage up to 800GB

Pipeline for cenX (centroFlye)

In this manual we go step-by-step demonstrating centroFlye algorithm. The detailed information about the algorithm can be found in the paper.

Please, run all commands from the root of the repository. Results of all steps will be stored at results_cenX directory.

1. Recruitment of cenX reads

We use 50x ultra-long Oxford Nanopore dataset generated by Telomere2Telomere Consorsium, rel2. This step is run directly on the reads at the link. The following bash script splits the input file in 50 files and runs DXZ1-based recruitment in 50 threads. DXZ1 is supplied in the current repo at supplementary_data/DXZ1_rc.fasta. The result of this step is a fasta file with centromeric reads that is stored at results_cenX/centromeric_reads/centromeric_reads.fasta

From the root of the project run

make -C scripts/read_recruitment

and start recruitment (<path_to_CHM13> is where the ONT reads are located, see section Dependencies/Data):

bash scripts/read_recruitment/run_read_recruitment.sh \
       <path_to_CHM13>/rel2.fastq.gz \
       results_cenX/centromeric_reads 50 11100000

Required resources:

• Storage space: 150GB
• Clock time: 1 hour
• RAM: < 50MB

2. Applying centroFlye to cenX reads

At this step we are utilizing centromeric reads from step 1 and run centroFlye on them. The result of this step is the final cenX assembly that is stored at results_cenX/final_assembly.fasta. The following command uses 50 threads.

python centroFlye.py \
            --coverage 32 \
            --reads results_cenX/centromeric_reads/centromeric_reads.fasta \
            -t 50 \
            --outdir results_cenX \
            --unit supplementary_data/DXZ1_rc.fasta

Required resources:

• Storage space: < 3GB
• Clock time: ~9 hours (mostly recruitment of unique k-mers)
• RAM: peak usage up to 800GB

Quick start guide for cen6 (centroFlyeMono)

centroFlye has a special module centroFlyeMono that uses only alpha satellite structure to assemble centromeres. The steps below describe how to apply it to cen6 assembly.

If you want to run the whole centroFlyeMono pipeline to generate cen6 assembly with one command, please run

./run_all_cen6.sh <path_to_CHM13> results_cen6 50

You can customize the output directory and the number of threads:

./run_all_cen6.sh <path_to_CHM13> <output directory> <number of threads>

All intermediate and final results will then be placed in <output directory>. If you want to start from scratch you can simply remove this directory.

Pipeline for cen6 (centroFlyeMono)

In this manual we go step-by-step demonstrating centroFlyeMono algorithm. The detailed information about the algorithm can be found in the paper.

Please, run all commands from the root of the repository. Results of all steps will be stored at results_cen6 directory.

1. Recruitment of cen6 reads

We use 120x ultra-long Oxford Nanopore dataset generated by Telomere2Telomere Consorsium, rel3. This step is run directly on the reads at the link. The following bash script splits the input file in 50 files and runs D6Z1-based recruitment in 50 threads. D6Z1 is supplied in the current repo at supplementary_data/D6Z1.fasta. The result of this step is a fasta file with centromeric reads that is stored at results_cen6/centromeric_reads/centromeric_reads.fasta

From the root of the project run

make -C scripts/read_recruitment

and start recruitment (<path_to_CHM13> is where the ONT reads are located, see section Dependencies/Data):

bash scripts/read_recruitment/run_read_recruitment.sh \
       <path_to_CHM13>/rel3.fastq.gz \
       results_cen6/centromeric_reads 50 29000000 \
       supplementary_data/D6Z1.fasta \
       550

Required resources:

• Storage space: 150GB
• Clock time: 1 hour
• RAM: < 50MB

2. Running String Decomposer on cen6 reads

We use String Decomposer (SD; Dvorkina et al., 2020) to partition cen6 reads into distinct monomers of D6Z1. These monomers are supplied in the current repo at supplementary_data/D6Z1_monomers.fasta. The result of this step is the report of SD which is stored at results_cen6/string_decomposer_report

The following commands take 50 threads

python scripts/ext/stringdecomposer/longreads_decomposer.py \
            -s results_cen6/centromeric_reads/centromeric_reads.fasta \
            -m supplementary_data/D6Z1_monomers.fasta \
            -t 50
mkdir results_cen6/string_decomposer_report
mv decomposition{.tsv,_alt.tsv} results_cen6/string_decomposer_report

Required resources:

• Storage space: 6GB
• Clock time: 9h
• RAM: < 10GB

3. Running centroFlyeMono on cen6 reads using SD output

At this step we are utilizing string decomposer output on cen6 reads and run centromFlyeMono on them. The final cen6 assembly is located in results_cen6/centroFlyeMono_cen6/polishing/scaffold_0/scaffold_0.fasta.

python scripts/centroFlyeMono.py \
       --sd-report results_cen6/string_decomposer_report/decomposition.tsv \
       --monomers supplementary_data/D6Z1_monomers.fasta \
       --centromeric-reads results_cen6/centromeric_reads/centromeric_reads.fasta \
       --outdir results_cen6/centroFlyeMono_cen6

Required resources:

• Storage space: 120MB
• Clock time: 30 mins
• RAM: < 1GB

Publications

• Bzikadze A.V., Pevzner P.A. centroFlye: Assembling Centromeres with Long Error-Prone Reads, Nature Biotechnology, in press, 2020
• Dvorkina T., Bzikadze A.V., Pevzner P.A. The String Decomposition Problem and its Applications to Centromere Assembly, Bioinformatics, in press, 2020
• Miga, K.H., Koren, S., Rhie, A., Vollger, M.R., Gershman, A., Bzikadze, A., Brooks, S., Howe, E., Porubsky, D., Logsdon, G.A., et al. Telomere-to-telomere assembly of a complete human X chromosome, Nature, in press, 2020
• Mikheenko, A., Bzikadze, A.V., Gurevich, A., Miga, K.H., and Pevzner, P.A. TandemMapper and TandemQUAST: mapping long reads and assessing/improving assembly quality in extra-long tandem repeats, Bioinformatics, in press, 2020

Contacts

Please report any problems to the issue tracker. Alternatively, you can write directly to abzikadze@ucsd.edu.