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Hunting for viruses in French Guiana
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Nacho Caballero
April 29, 2014
Science
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58
Hunting for viruses in French Guiana
Lab meeting presentation about my work doing viral metagenomic analysis in French Guiana
Nacho Caballero
April 29, 2014
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Transcript
French Guiana Virus Hunting in Nacho Caballero
French Guiana
Rodents Bats
Rodents Bats Leishmania
Capture
Capture Isolate viral particles
Capture Isolate viral particles Extract RNA
Capture Isolate viral particles Extract RNA Sequence
Estimated read coverage % reads with coverage smaller than x
Rodents
Estimated read coverage % reads with coverage smaller than x
Rodents
Estimated read coverage % reads with coverage smaller than x
Rodents Bats
Read How can we estimate the coverage without a reference
genome?
Read How can we estimate the coverage without a reference
genome?
K-mers Read How can we estimate the coverage without a
reference genome?
How can we estimate the coverage without a reference genome?
1 1 1 1 1 1 1 How can we
estimate the coverage without a reference genome?
7 8 10 8 11 3 6
7 8 10 8 11 3 6 Median k-mer count
≈ Read coverage
None
k-mers make it possible to align without a reference
None
Problem: each sequencing error introduces k erroneous k-mers
Problem: each sequencing error introduces k erroneous k-mers
7 8 10 8 11 3 6 Over a threshold,
additional reads are redundant
5 5 5 5 5 3 5 Solution: digital normalization
reduces redundancy and errors
Assembly
Assembly SPADes
Assembly Alignment
Assembly Alignment BLAST
Assembly Taxonomy Alignment
Assembly Taxonomy Alignment NCBI
Problem: 67% of contigs in rodent dataset (serum) align to
human sequences
Problem: 67% of contigs in rodent dataset (serum) align to
human sequences Night-heron coronavirus HKU19 (1 Kb) Simian hemorrhagic fever virus (300 bp) Equine arteritis virus (3.7 Kb) Possum nidovirus Rodent hepacivirus Chipmunk parvovirus Theiler's disease-associated virus Reticuloendotheliosis virus Mosquito VEM Anellovirus SDBVL A Porcine reproductive and respiratory syndrome virus Dragonfly-associated circular virus 1 Gemycircularvirus 3 Rodent pegivirus Cyclovirus PK5510 Hypericum japonicum associated circular DNA virus
Pig stool associated circular ssDNA virus (1Kb) Avian gyrovirus 2
Torque teno sus virus 1a Mosquito VEM virus SDBVL G Turdivirus 3 Problem: 92% of contigs in bat dataset (droppings) don’t align to anything in NCBI
Lymphocytic choriomeningitis virus (7kb) Hepatitis C virus Amphotropic murine leukemia
virus Murid herpesvirus 1 Mosquito VEM Anellovirus SDBVL A Rat retrovirus SC1 Mason-Pfizer monkey virus (retrovirus) Eidolon helvum parvovirus 2 Periplaneta fuliginosa densovirus (also a parvovirus) Moloney murine sarcoma virus Sclerotinia sclerotiorum hypovirulence associated DNA virus 1 Problem: 95% of contigs in rodent dataset 2 (serum, spleen) align to mouse sequences (2)
7 out of 10 samples contained more than 1Kb of
Leishmania RNA virus (94% ident) 5 Kb genome
Lessons
Assume that 50% of your samples are going to fail
Lessons
Assume that 50% of your samples are going to fail
Lessons Design a small experiment, then iterate
Assume that 50% of your samples are going to fail
Lessons Design a small experiment, then iterate Come up with excuses to learn