The human reelin gene: isolation, sequencing, and mapping on chromosome 7

The mouse reelin gene (Reln) encodes a novel protein that, when mutated, results in the characteristic reeler phenotype. A key component of this phenotype is the extensive disruption of the organization of many brain structures. Reelin is believed to be an extracellular protein that controls neural cell positioning during brain development. The reelin gene is conserved in many vertebrate species, including humans. To study the role of the reelin homolog in human brain development, we have isolated and characterized the human gene (RELN). Like its murine counterpart, RELN is large, encoding an mRNA of approximately 12 kb. Overlapping cDNA clones containing the entire open reading frame were isolated and sequenced, revealing that the predicted mouse and human proteins are similar in size (388 kD) and that the amino acid and nucleotide sequences are 94.2% and 87.2% identical, respectively. Northern hybridization analyses revealed that RELN is expressed in fetal and postnatal brain as well as liver. The expression of RELN in postnatal human brain was high in the cerebellum. RELN was mapped to human chromosome 7q22, based on both fluorescence in situ hybridization studies and localization within a well-positioned yeast artificial chromosome (YAC) contig. The YAC contig also contains a number of gentic markers. Together, these studies provide the sequence information and genetic tools for performing more detailed analyses of RELN in an attempt to define its role in human brain development and possibly in human disease.