Integrins of the Starlet Sea Anemone Nematostella vectensis

Integrins are extracellular matrix receptors composed of alpha and beta subunits. Here we describe two alpha subunits and four beta subunits from the starlet sea anemone Nematostella vectensis. Phylogenetic analysis suggests that the alpha subunits are most closely related to RGD- and LDV-dependent alpha subunits of chordates. The beta subunits cluster with the previously described beta integrins of the hard coral Acropora millepora. The expression of one of the alpha subunits and three of the beta subunits was confirmed by reverse transcription PCR and in situ hybridization. The alpha subunit is primarily expressed in cells near muscles, by a subset of gastrodermal cells, and in the gonad. The three beta subunits each have distinctive patterns of expression: one is concentrated in the gonad and mesenteric filament, another is found in a subset of cells in the epidermis of the oral region and in a subset of gastrodermal cells in the mesenteries, and a third is expressed widely. Changes in expression were also studied 48 h after horizontal transection by quantitative reverse transcription PCR and in situ hybridization. One of the beta subunits is expressed 8-fold higher during regeneration, and its expression is observed in cells within both the epidermis and the gastrodermis at the site of regeneration. Our observations confirm that complex patterns of integrin expression were already present in basal metazoans. The integrins expressed in the gonads may play roles in mediating sperm-egg interactions in N. vectensis, while others may play a role in regulating proliferation during regeneration.