title: Premature aggregation of type IV collagen and early lethality in lysyl hydroxylase 3 null mice.
abstract: Collagens carry hydroxylysine residues that act as attachment sites for carbohydrate units and are important for the stability of crosslinks but have been regarded as nonessential for vertebrate survival. We generated mice with targeted inactivation of the gene for one of the three lysyl hydroxylase isoenzymes, LH3. The null embryos developed seemingly normally until embryonic day 8.5, but development was then retarded, with death around embryonic day 9.5. Electron microscopy (EM) revealed fragmentation of basement membranes (BMs), and immuno-EM detected type IV collagen within the dilated endoplasmic reticulum and in extracellular aggregates, but the typical BM staining was absent. Amorphous intracellular and extracellular particles were also seen by collagen IV immunofluorescence. SDS/PAGE analysis demonstrated increased mobilities of the type IV collagen chains, consistent with the absence of hydroxylysine residues and carbohydrates linked to them. These results demonstrate that LH3 is indispensable for biosynthesis of type IV collagen and for BM stability during early development and that loss of LH3's functions leads to embryonic lethality. We propose that the premature aggregation of collagen IV is due to the absence of the hydroxylysine-linked carbohydrates, which thus play an essential role in its supramolecular assembly.
authors.affiliation: Collagen Research Unit and Department of Medical Biochemistry and Molecular Biology, Biocenter Oulu, University of Oulu, 90014 Oulu, Finland.
authors.forename: Kati
authors.initials: K
authors.lastname: Rautavuoma
authors.forename: Kati
authors.initials: K
authors.lastname: Takaluoma
authors.forename: Raija
authors.initials: R
authors.lastname: Sormunen
authors.forename: Johanna
authors.initials: J
authors.lastname: Myllyharju
authors.forename: Kari I
authors.initials: KI
authors.lastname: Kivirikko
authors.forename: Raija
authors.initials: R
authors.lastname: Soininen
mesh_terms: D000818:Animals; D001485:Basement Membrane / Q000378:metabolism; D015153:Blotting, Western; D024141:Collagen Type IV / Q000096:biosynthesis* / Q000737:chemistry / Q000378:metabolism; D047108:Embryonic Development / Q000502:physiology*; D004721:Endoplasmic Reticulum / Q000378:metabolism; D005313:Fetal Death / Q000235:genetics / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D018507:Gene Expression Regulation, Developmental / Q000502:physiology; D020868:Gene Silencing; D018390:Gene Targeting; D005838:Genotype; D006579:Heterozygote; D008648:Mesoderm / Q000166:cytology / Q000648:ultrastructure; D051379:Mice; D018345:Mice, Knockout; D008854:Microscopy, Electron / Q000379:methods; D008240:Procollagen-Lysine, 2-Oxoglutarate 5-Dioxygenase / Q000172:deficiency* / Q000235:genetics / Q000502:physiology*
chemical_list: D024141:Collagen Type IV; D008240:Procollagen-Lysine, 2-Oxoglutarate 5-Dioxygenase