Evolution of Class I cytokine receptors.
BACKGROUND
The Class I cytokine receptors have a wide range of actions, including a major role in the development and function of immune and blood cells. However, the evolution of the genes encoding them remains poorly understood. To address this we have used bioinformatics to analyze the Class I receptor repertoire in sea squirt (Ciona intestinalis) and zebrafish (Danio rerio).


RESULTS
Only two Class I receptors were identified in sea squirt, one with homology to the archetypal GP130 receptor, and the other with high conservation with the divergent orphan receptor CLF-3. In contrast, 36 Class I cytokine receptors were present in zebrafish, including representative members for each of the five structural groups found in mammals. This allowed the identification of 27 core receptors belonging to the last common ancestor of teleosts and mammals.


CONCLUSIONS
This study suggests that the majority of diversification of this receptor family occurred after the divergence of urochordates and vertebrates approximately 794 million years ago (MYA), but before the divergence of ray-finned from lobe-finned fishes around 476 MYA. Since then, only relatively limited lineage-specific diversification within the different Class I receptor structural groups has occurred.
Liongue
Clifford
C
School of Medicine, Deakin University, Geelong, Victoria, Australia. liongue@deakin.edu.au <liongue@deakin.edu.au>
Ward
Alister C
AC
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002938:Ciona intestinalis / Q000235:genetics*; D019143:Evolution, Molecular; D008969:Molecular Sequence Data; D018121:Receptors, Cytokine / Q000145:classification / Q000235:genetics*; D015027:Zebrafish / Q000235:genetics*; D029961:Zebrafish Proteins / Q000235:genetics
D018121:Receptors, Cytokine; D029961:Zebrafish Proteins