Microphthalmia is a malformation that reduces the size of the ocular globe. The etiologies of this anomaly are various, but the genetic background appears to have a predominant influence on its development through mutations of genes controlling ocular developmental processes. LRP4 is a type I single transmembrane protein that is essential for the formation of neuromuscular junctions. We created and experimented on homozygous Lrp4-deficient mice and found the microphthalmia phenotype in their eyes. The loss of Lrp4 resulted in an elevated incidence of microphthalmia and affected the mRNA expression of the members of bone morphogenetic protein, fibroblast growth factor, Sonic hedgehog, and WNT signaling pathways and of several pathogenic genes for microphthalmia. Moreover, the loss of Lrp4 enhanced the incidence of aberrant retinal folds, which appeared pleated and corrugated in the eyeball. (C) 2018 Elsevier Inc. All rights reserved.