Chicken β-defensin gene cluster
Chicken genome encodes 13 β-defensin (Gal) genes in a single innate-immunity cluster.
Source
A genome-wide screen identifies a single beta-defensin gene cluster in the chicken: implications for the origin and evolution of mammalian defensins
Study at a glance
- Design
- Computational / modelling — TBLASTN/genome and EST screens plus RT-PCR confirmation of chicken β-defensin genes
- N
- Gene discovery across genomic/EST databases; 13 Gal β-defensin genes reported — not a sample-N study
- Population
- Chicken genome and EST sequence resources
- Outcome
- Size and clustering of the chicken β-defensin gene repertoire
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Chicken β-defensin gene cluster
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13 Gal genes are the full β-defensin repertoire.
No other sequence containing β-defensin-like six-cysteine motif has been found in NR, EST or genomic databases, suggesting that 13 Gal genes constitute the entire repertoire of the β-defensin family encoded in the chicken genome.
Nine novel Gal 4–12 sequences found.
In addition to three known chicken β-defensins ( Gal 1–3 ) [,], nine novel putative sequences, namely Gal 4–12 , have been found in the EST database with at least two hits for each, and such sequences have also been confirmed in genomic sequences (Table ).
What they did
TBLASTN/genome screens plus RT-PCR confirmed novel chicken β-defensin genes and compared them phylogenetically to mammals.
What they found
Nine novel Gal4–12 plus Gal13 yield 13 total β-defensins; bird–mammal split ~310 mya implies ancient β-defensin subfamilies.
The limits
What it doesn't show
Does not measure antimicrobial activity of every Gal peptide in vivo.
Key terms
- β-defensin
- Cationic cysteine-rich antimicrobial peptide.
- Gal genes
- Gallus β-defensin gene family members.
- Innate immunity
- Immediate, germline-encoded host defense.
- Gene cluster
- Tandemly arranged related genes.
- EST
- Expressed sequence tag evidence of transcription.
- Cysteine motif
- Six-cysteine signature of defensins.
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Gal repertoire size:
Common questions
How many chicken β-defensins?
13 Gal genes.
Novel Gal4–12 count?
Nine.
Bird–mammal split estimate?
~310 million years ago.
Gal13 confirmed how?
RT-PCR from kidney.
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