Characterization of hydra type IV collagen - Type IV collagen is essentialfor head regeneration and its expression is up-regulated upon exposure to glucose

Hydra vulgaris mesoglea is a primitive basement membrane that also exhibits some features of an interstitial matrix. We have characterized cDNAs that encode the full-length hydra alpha1(IV) chain. The 5169-base pair transcrip t encodes a protein of 1723 amino acids, including an interrupted 1455-resi due collagenous domain and a 228-residue C-terminal noncollagenous domain. N-terminal sequence analyses of collagen IV peptides suggest the molecule i s homotrimeric. Denatured hydra type IV collagen protein occurs as dimers a nd higher order aggregates held together by nonreducible cross-links. Hydra collagen TV exhibits no functional evidence for the presence of a 7 S doma in. Type TV collagen is expressed by the ectoderm along the entire longitud inal axis of the animal but is most intense at the base of the tentacles at the site of battery cell transdifferentiation. Antisense studies show that inhibition of collagen IV translation causes a blockage in head regenerati on, indicating its importance in normal hydra development. Exposure of adul t hydra to 15 mm glucose resulted in up-regulation of type IV collagen mRNA levels within 48 h and significant thickening of the mesoglea within 14 da ys, suggesting that basement membrane thickening seen in diabetes may be, i n evolutionary terms, an ancient glucose-mediated response.