title: Absence of basement membranes after targeting the LAMC1 gene results in embryonic lethality due to failure of endoderm differentiation.
abstract: The LAMC1 gene coding for the laminin gamma1 subunit was targeted by homologous recombination in mouse embryonic stem cells. Mice heterozygous for the mutation had a normal phenotype and were fertile, whereas homozygous mutant embryos did not survive beyond day 5.5 post coitum. These embryos lacked basement membranes and although the blastocysts had expanded, primitive endoderm cells remained in the inner cell mass, and the parietal yolk sac did not develop. Cultured embryonic stem cells appeared normal after targeting both LAMC1 genes, but the embryoid bodies derived from them also lacked basement membranes, having disorganized extracellular deposits of the basement membrane proteins collagen IV and perlecan, and the cells failed to differentiate into stable myotubes. Secretion of the linking protein nidogen and a truncated laminin alpha1 subunit did occur, but these were not deposited in the extracellular matrix. These results show that the laminin gamma1 subunit is necessary for laminin assembly and that laminin is in turn essential for the organization of other basement membrane components in vivo and in vitro. Surprisingly, basement membranes are not necessary for the formation of the first epithelium to develop during embryogenesis, but first become required for extra embryonic endoderm differentiation.
authors.affiliation: Department of Human Anatomy and Cell Biology, University of Liverpool, Liverpool L69 3GE, United Kingdom.
authors.forename: N
authors.initials: N
authors.lastname: Smyth
authors.forename: H S
authors.initials: HS
authors.lastname: Vatansever
authors.forename: P
authors.initials: P
authors.lastname: Murray
authors.forename: M
authors.initials: M
authors.lastname: Meyer
authors.forename: C
authors.initials: C
authors.lastname: Frie
authors.forename: M
authors.initials: M
authors.lastname: Paulsson
authors.forename: D
authors.initials: D
authors.lastname: Edgar
mesh_terms: D000818:Animals; D001485:Basement Membrane / Q000196:embryology; D004707:Endoderm / Q000502:physiology*; D005260:Female; D005313:Fetal Death; D018390:Gene Targeting; D007797:Laminin / Q000235:genetics / Q000502:physiology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL
chemical_list: D007797:Laminin; C089141:laminin gamma 1