RT Journal Article SR Electronic T1 Collagen IV of basement membranes: I. Origin and diversification of COL4 genes enabling animal evolution JF bioRxiv FD Cold Spring Harbor Laboratory SP 2023.10.18.563013 DO 10.1101/2023.10.18.563013 A1 Page-McCaw, Patrick S. A1 Pokidysheva, Elena N. A1 Darris, Carl E. A1 Chetyrkin, Sergei A1 Fidler, Aaron L. A1 Murawala, Prayag A1 Gallup, Julianna A1 Aspirnauts A1 Hudson, Julie K. A1 Hudson, Billy G. YR 2023 UL http://biorxiv.org/content/early/2023/10/21/2023.10.18.563013.abstract AB Collagen IV is a primordial component of basement membranes, a specialized form of extracellular matrix that enabled multi-cellular epithelial tissues. In mammals, collagen IV assembles from a family of six α-chains (α1 to α6), encoded by six genes (COL4A1 to COL4A6), into three distinct scaffolds: the α121, the α345 and a mixed scaffold containing both α121 and α565. The six mammalian COL4A genes occur in pairs that occur in a head-to-head arrangement on three distinct chromosomes. In Alport syndrome, variants in the COL4A3, 4 or 5 genes cause either loss or defective assembly of the collagen IVα345 scaffold which results in a dysfunctional glomerular basement membrane, proteinuria and progression to renal failure in millions of people worldwide. Here, we determine the evolutionary emergence and diversification of the COL4A genes using comparative genomics and biochemical analyses. Using syntenic relationships to genes closely linked to the COL4A genes, we determine that the COL4A3 and COL4A4 gene pair appeared in cyclostomes (hagfish and lampreys) while the COL4A5 and COL4A6 gene pair emerged in gnathostomes, jawed vertebrates. The more basal chordate species, lancelets and tunicates, do not have discrete kidneys and have a single COL4A gene pair, though often with single isolated COL4 genes similar to those found in C elegans. Remarkably, while the six COL4A genes are conserved in vertebrates, amphibians have lost the COL4A3 and COL4A4 genes. Our findings of the evolutionary emergence of these genes, together with the amphibian double-knockout, opens an experimental window to gain insights into functionality of the Col IVα345 scaffold.Competing Interest StatementThe authors have declared no competing interest.ASAlport syndromeBMbasement membraneCOL4Athe Collagen IV gene where found in the head-to-head orientationCOL4Sthe Collagen IV gene where found as a single geneGBMglomerular basement membrane.