GENXPRO GMBH, ALTENHÖFERALLEE 3, 60438 FRANKFURT MAIN, GERMANY

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http://rosalind.info/problems/list-view/

Address of the bookmark: http://rosalind.info/problems/list-view/

Address of the bookmark: http://www.sthda.com/english/wiki/rna-seq-differential-expression-work-flow-using-deseq2

What Are Kallisto and Salmon?

At their core, both Kallisto and Salmon are tools for quantifying transcript abundance from RNA-Seq reads. They bypass traditional alignment-based methods, replacing them with pseudoalignment or quasi-mapping, which drastically speeds up the process.

• Kallisto was developed by Lior Pachter’s lab and introduced the concept of pseudoalignment using a de Bruijn graph.
• Salmon, developed by Rob Patro’s group, builds on this idea with quasi-mapping and offers additional features like advanced bias correction.

Head-to-Head Comparison

1. Algorithm

• Kallisto uses pseudoalignment, focusing on matching k-mers from reads to a transcriptome index.
• Salmon uses quasi-mapping, which adds more flexibility and can also work with aligned reads (BAM files).

2. Input and Flexibility

• Kallisto works with raw FASTQ reads and requires a custom transcriptome index.
• Salmon accepts FASTQ or pre-aligned BAM files, giving you more workflow options.

3. Bias Correction

One of Salmon’s major advantages is its sophisticated bias correction system. It corrects for:

• Sequence-specific bias
• Positional bias
• GC-content bias

Kallisto offers basic sequence bias correction but lacks the comprehensive models found in Salmon.

4. Speed and Resources

• Kallisto is blazing fast and slightly more memory-efficient.
• Salmon is still very fast, but the added features can come at a small computational cost.

5. Output and Downstream Analysis

• Both tools provide transcript-level quantifications and support bootstrapping for variance estimation.
• Salmon can also summarize counts at the gene level if provided with a mapping file (--geneMap).
• Kallisto integrates seamlessly with Sleuth for differential expression analysis.
• Salmon works well with tximport, DESeq2, edgeR, and other Bioconductor tools.

Choosing the Right Tool

Example Command Lines

Kallisto (paired-end):

kallisto quant -i transcriptome.idx -o output -b 100 sample_R1.fastq sample_R2.fastq

Salmon (paired-end, bias correction):

salmon quant -i salmon_index -l A -1 sample_R1.fastq -2 sample_R2.fastq \
  -p 8 --validateMappings --seqBias --gcBias -o output

Conclusion

Both Kallisto and Salmon are exceptional tools that have transformed RNA-Seq analysis. Your choice largely depends on your priorities—whether it's speed, accuracy, flexibility, or compatibility with downstream tools.

For many users, Salmon offers a more complete and flexible solution, especially when bias correction and gene-level outputs are essential. However, Kallisto remains a favorite for quick, accurate quantification, especially when paired with the Sleuth pipeline.

Address of the bookmark: http://hibberdlab.com/transrate/index.html

Speaker:

Mario Deng MD FACC FESC
Professor of Medicine
Advanced Heart Failure/Mechanical
Support/Heart Transplant
David Geffen School of 
Medicine at UCLA
Ronald Reagan UCLA Medical Center

Abstract:

The webinar will highlight some of the interesting case studies wherein multi-gene testing with NGS was helpful in arriving at a confirmatory as well as differential diagnosis, even for complex clinical conditions. With robust bioinformatic analysis, we were able to detect few complex variations in few cases which a conventional test had missed. Some of those cases will also be discussed.

Session 1: 9 am CET, 18 Apr 2018
Session 2: 8 am CET, 18 Apr 2018 
To attend, register here: http://www.strand-ngs.com/webinar_registration

About Speaker: Dr. Aparna Ganapathy is Senior scientist- Clinical Diagnostics at Strand Life Sciences. She has over 8 years of experience in human genetics and molecular biology. She received her Ph.D. in Human Molecular Genetics from Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore. At Strand Life Sciences, she is involved in the interpretation and clinical reporting of the genetic disorders. The focus of these genetic tests is to provide accurate and rapid clinical diagnosis for various inherited disorders.