Although this might suggest a developmental role for microglia in the migration of GnRH neurons out of the olfactory placode, in contrast with human Kallmann's syndrome patients, adult Csf1op/op mice have normal GnRH neuron numbers and location within the preoptic area [5], and synthesis of GnRH appears normal (Erblich and Pollard, unpublished). The gene discussed is GNRH1; the disease is Kallmann syndrome.