DSCAM

DSCAM and Dscam are both abbreviations for Down Syndrome Cell Adhesion Molecule. The case difference is significant: DSCAM refers to the gene, and Dscam refers to protein the gene codes.

Down Syndrome (DS) caused by trisomy 21 is the most common birth defect associated with mental retardation. Recently, a novel gene named, DSCAM, has been identified in the DS critical region. DSCAM is predicted to be a transmembrane protein with a very high structural and sequence homology to immunoglobulin (Ig) superfamily of cell adhesion molecules and is expressed in the developing nervous system with the highest level in fetal brain. Diverse glycoproteins of cell surfaces and extracellular matrices operationally termed as 'adhesion molecule' are important in the specification of cell interactions during development, maintenance and regeneration of the nervous system.

Of particular interest is that Dscam in drosophila has 38,016 isoforms from four variable exon clusters (12, 48, 33 and 2 alternatives respectively). The diversity of isoforms from alternative splicing of the Dscam1 gene in D. melanogaster allows every neuron in the fly to display a unique set of Dscam proteins on its cell surface. Dscam interaction stimulates self-avoidance mechanisms that are essential for normal neural circuit development.