Meeting Abstract
P1.63 Friday, Jan. 4 Collagens in the ctenophore Pleurobrachia bachei : Remarkable expansion and diversity of genes controlling the extracellular matrix in basal metazoans. CHURCHES, N*; KOHN, A.B.; KOCOT, K.M.; SWALLA, B.J.; MOROZ , L.L.; Univ of Washington; Univ of Florida; Auburn Univ; Univ of Washington; Univ of Florida nthnchrchs@yahoo.com
The evolution of multicellular animals required the development of epithelial tissues that function in controlling the transport of molecules from environment to organism. Collagen proteins are crucial to the formation of epithelial tissues, and are therefore critical in understanding the origins of multicellularity and Metazoan evolution. We characterized the collagen complement from the sequenced genome of the ctenophore Pleurobrachia bachei. 1) We discovered that P.bachei has 7 distinct type IV collagen genes, an expansion unseen in any organism sequenced to date. These genes show unique distribution across the genome: four were in an in-line pattern (αA and αB, αD and αE); two were found independent of other genes (αF, αG), while another two were aligned in a head-to-head fashion (αB,αC). This exceptional arrangement suggests both traditional and inverted gene duplication events in the ctenophore lineage. Ctenophore collagen intron/exon arrangements were also uniquely diverse, with a range of 14-40 exons, depending on the gene. 2) Phylogenetic analysis revealed two distinct collagen groups, the α1-like and α2-like sub-families that are common in bilaterians. Yet, gene to gene comparisons reveal a more diverse type IV collagen complement than even found in chordates including humans. 3) We found differential expression between the sub-family gene types, indicating unique physiological use of different collagens. Our findings imply that the common ancestor to all Metazoa might have contained a much more developed collagen complement than was previously appreciated. At the same time, there is extensive parallel evolution of ancestral collagens with remarkable functional specification and diversity of body plans in ctenophores.
