Cloning and expression of a novel gene for a protein with leucine-rich repeats in the developing mouse nervous system

Abstract In a variety of organisms from yeast to humans, members of the leucine-rich repeat (LRR) family, in which one repeat consists of 24 amino acids and leucine residues appear regularly, have been shown to be involved in protein-protein interactions. In Drosophila , members of this family have significant functions in neural development. It is thus possible that similar molecules play a crucial role in the morphogenesis of the mammalian nervous system. Using a human brain cDNA fragment encoding an LRR as a probe, we have isolated a mouse brain cDNA which encodes a new LRR protein, NLRR-3 protein. The isolated cDNA is 3350 bp long including one open reading frame encoding a protein of 707 amino acids, the deduced amino acid sequence of which has a signal peptide and a transmembrane region. The NLRR-3 protein also contains an RGD sequence and 11 LRRs with amino- and carboxy-terminal LRR-flanking regions which are conserved among adhesive proteins and signal-transducing receptors in this family. Northern-blot analysis revealed strong expression of an approx. 4.2 kb NLRR-3 mRNA in the brain from E17 to P7 and weak expression in adults. Then, in situ hybridization analysis demonstrated that NLRR-3 mRNA was expressed in the brain, in which stronger expression was localized in the ventricular zone and anlage of thalamus, spinal cord, and dorsal root ganglion in E11–17 cerebellum, and cerebral cortex in adults. The molecular structure in addition to the transient and localized expression suggests that the NLRR-3 protein plays a role in the development and maintenance of the nervous system by protein-protein interactions.