Fidler, A.L., Vanacore, R.M., Chetyrkin, S.V., Pedchenko, V.K., Bhave, G., Yin, V.P., Stothers, C.L., Rose, K.L., McDonald, W.H., Clark, T.A., Borza, D.B., Steele, R.E., Ivy, M.T., Hudson, J.K., and Hudson, B.G. (2014) A unique covalent bond in basement membrane is a primordial innovation for tissue evolution. Proceedings of the National Academy of Sciences of the United States of America. 111(1):331-336.
Basement membrane, a specialized ECM that underlies polarized epithelium of eumetazoans, provides signaling cues that regulate
cell behavior and function in tissue genesis and homeostasis. A collagen IV scaffold, a major component, is essential for
tissues and dysfunctional in several diseases. Studies of bovine and Drosophila tissues reveal that the scaffold is stabilized by sulfilimine chemical bonds (S = N) that covalently cross-link methionine
and hydroxylysine residues at the interface of adjoining triple helical protomers. Peroxidasin, a heme peroxidase embedded
in the basement membrane, produces hypohalous acid intermediates that oxidize methionine, forming the sulfilimine cross-link.
We explored whether the sulfilimine cross-link is a fundamental requirement in the genesis and evolution of epithelial tissues
by determining its occurrence and evolutionary origin in Eumetazoa and its essentiality in zebrafish development; 31 species,
spanning 11 major phyla, were investigated for the occurrence of the sulfilimine cross-link by electrophoresis, MS, and multiple
sequence alignment of de novo transcriptome and available genomic data for collagen IV and peroxidasin. The results show that
the cross-link is conserved throughout Eumetazoa and arose at the divergence of Porifera and Cnidaria over 500 Mya. Also,
peroxidasin, the enzyme that forms the bond, is evolutionarily conserved throughout Metazoa. Morpholino knockdown of peroxidasin
in zebrafish revealed that the cross-link is essential for organogenesis. Collectively, our findings establish that the triad—a
collagen IV scaffold with sulfilimine cross-links, peroxidasin, and hypohalous acids—is a primordial innovation of the ECM
essential for organogenesis and tissue evolution.