ENHANCEMENT OF S-100-BETA PROTEIN IN BLOOD OF PATIENTS WITH DOWNS-SYNDROME

The human gene encoding the β subunit of S-100 protein (S-100β) was mapped on chromosome 21. In order to confirm the expression of gene-dosage effect of S-100β in patients with Down's syndrome (DS), concentrations of immunoreactive S-100α and S-100β proteins were determined in the blood plasma and lymphocytes fraction of the patients and control subjects. Cu/Zn-superoxide dismutase (SOD), a protein that is known to show the gene-dosage effect on the trisomy of chromosome 21, also was immunoassayed in the same blood samples as control proteins. In blood plasma, S-100β protein as well as Cu/Zn SOD was enhanced (P<0.001) in the patients (160±70 pg S-100β/ml and 87±83 ng SOD/ml, N=44) as compared with control individuals (76±25 pg/ml, and 18±11 ng/ml, respectively, N=28). However, concentrations of S-100α in blood plasma of DS patients were similar to those of normal subjects. Concentrations of S-100β in lymphocyte fractions of DS patients (24.7±10.9 ng/mg protein) were also higher (P<0.001) than those of control subjects (10.1±5.8 ng/mg protein). These results indicate that gene-dosage effect of S-100β levels are expressed in DS patients. © 1990 Humana Press Inc.