Collagen IV alpha 3, alpha 4, and alpha 5 chains in rodent basal laminae: sequence, distribution, association with laminins, and developmental switches.

TLDR

Collagen IV is a major component of vertebrate basal laminae and humans possess six α chains (α1–α6), with α3–α6 linked to diseases such as Goodpasture and Alport syndromes. The study aimed to extend human collagen IV research to a model organism by cloning partial mouse cDNAs for collagen α3, α4, and α5(IV) chains. The authors cloned partial mouse collagen IV cDNAs, produced chain‑specific antibodies, and used them for expression and localization studies. Ribonuclease protection and immunohistochemistry showed that α3, α4, and α5(IV) are most highly expressed in kidney and lung (α5 also in heart), that α3 and α4 co‑express only in α5‑positive basal laminae, that α3–α5 chains associate with S‑laminin, and that during kidney development the glomerular basal lamina transitions from fetal α1/α2–B1 laminin to mature α3/α5–S laminin.

Abstract

Collagen IV is a major component of vertebrate basal laminae (BLs). Studies in humans have revealed a family of genes encoding alpha 1-alpha 6 collagen IV chains and implicated alpha 3-alpha 6 in disease processes (Goodpasture and Alport syndromes and diffuse leiomyomatosis). To extend studies of these components to an experimentally accessible animal, we cloned cDNAs encoding partial collagen alpha 3, alpha 4, and alpha 5(IV) chains from the mouse. Ribonuclease protection assays showed that all three genes were expressed at highest levels in kidney and lung; alpha 5(IV) was also expressed at high levels in heart. We then made antibodies specific for each collagen IV chain. Immunohistochemical studies of several tissues revealed many combinations of collagen IV chains; however, alpha 3 and alpha 4 (IV) were always coexpressed, and only appeared in BLs that were alpha 5(IV) positive. The alpha 3-alpha 5(IV) chains were frequently but not exclusively associated with the S (beta 2) chain of laminin, as were the alpha 1, 2 (IV) collagen chains with laminin B1 (beta 1). An analysis of developing rat kidney BLs showed that newly formed (S-shaped) nephrons harbored collagen alpha 1 and alpha 2(IV) and laminin B1; maturing (capillary loop stage) BLs contained collagen alpha 1-alpha 5(IV) and laminin B1 and S-laminin; and mature glomerular BLs contained mainly collagen alpha 3-alpha 5(IV) and S-laminin. Thus, collagen alpha 1 and alpha 2(IV) and laminin B1 appear to be fetal components of the glomerular BL, and there is a developmental switch to collagen alpha 3-alpha 5(IV) and S-laminin expression.