EXPRESSION OF THE KALLMANN-SYNDROME GENE IN HUMAN FETAL BRAIN AND IN THE MANIPULATED CHICK-EMBRYO

Kallmann syndrome is an inherited disorder characterized by an abnorma lity in olfactory system development. The gene for the X-linked form o f this disorder (KAL) maps to Xp22.3 and encodes a protein sharing hom ologies with molecules involved in neuronal migration and axonal pathf inding. Here we report the expression pattern of the KAL gene in vario us parts of the human fetal brain. We found KAL transcripts in granule cells of the olfactory bulb and the cerebellum, in the dorsomedial th alamus and in the developing cerebral cortex. To determine whether or not signals from the olfactory nerve are required for KAL expression i n the olfactory bulb, we analyzed chick embryos in which the olfactory placode was surgically removed. Those embryos lacking an olfactory ne rve had a histologically abnormal bulb which nevertheless expressed th e KAL gene at high levels. These findings indicate that, while the dev elopment of the proper cytoarchitecture of the olfactory bulb requires the innervation by olfactory axons, the expression of KAL is independ ent of such developmental processes.