Integrins of the starlet sea anemone Nematostella vectensis

Integrins are extracellular matrix receptors composed of α and β subunits. Here we describe two α subunits and four β subunits from the starlet sea anemone Nematostella vectensis. Phylogenetic analysis suggests that the α subunits are most closely related to RGD- and LDV-dependent α subunits of chordates. The β subunits cluster with the previously described β integrins of the hard coral Acropora millepora. The expression of one of the α subunits and three of the β subunits was confirmed by reverse transcription PCR and in situ hybridization. The α subunit is primarily expressed in cells near muscles, by a subset of gastrodermal cells, and in the gonad. The three β 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 β 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.