Background-Recent studies indicate an increased frequency of mutations in the gene for Gaucher disease, glucocerebrosidase (GBA), among patients with Parkinson disease. An international collaborative study was conducted to ascertain the frequency of GBA mutations in ethnically diverse patients with Parkinson disease.

Inheritance of a defect in a neuronal mechanism that regulates response to auditory stimuli was studied in nine families with multiple cases of schizophrenia. The defect, a decrease in the normal inhibition of the P50 auditoryevoked response to the second of paired stimuli, is associated with attentional disturbances in schizophrenia. Decreased P50 inhibition occurs not only in most schizophrenics, but also in many of their nonschizophrenic relatives, in a distribution consistent with inherited vulnerability for the illness. Neurobiological investigations in both humans and animal models indicated that decreased function of the ␣7-nicotinic cholinergic receptor could underlie the physiological defect. In the present study, a genome-wide linkage analysis, assuming autosomal dominant transmission, showed that the defect is linked [maximum logarithm of the odds (lod) score ‫؍‬ 5.3 with zero recombination] to a dinucleotide polymorphism at chromosome 15q13-14, the site of the ␣7-nicotinic receptor. Despite many schizophrenics' extremely heavy nicotine use, nicotinic receptors were not previously thought to be involved in schizophrenia. The linkage data thus provide unique new evidence that the ␣7-nicotinic receptor gene may be responsible for the inheritance of a pathophysiological aspect of the illness.