EXPRESSION PATTERN OF THE KALLMANN SYNDROME GENE IN THE OLFACTORY SYSTEM SUGGESTS A ROLE IN NEURONAL TARGETING

Kallmann syndrome is a genetic disorder characterized by a defect in o lfactory system development, which appears to be due to an abnormality in the migration of olfactory axons and gonadotropin releasing hormon e (Gn-RH) producing neurons. The X-linked Kallmann syndrome gene share s significant similarities with molecules involved in neural developme nt. We have now isolated the evolutionarily conserved chicken homologu e of the Kallmann gene. In the developing and adult chicken, high leve ls of expression were found in the mitral cells of the olfactory bulb (the target of olfactory axons) and in the Purkinje cells of the cereb ellar cortex, both areas affected in patients with Kallmann syndrome. We propose a model in which the Kallmann syndrome gene product is a si gnal molecule required for neuronal targeting throughout life.