Kamiya - cho , Kasugai , Aichi 480 - 03 , Japan . a ring 21 chromosome : parental

Biochemical studies showed that the proband had half normal activities of IDH1 and RPE, suggesting that she was a heterozygote for both enzymes. The gene for IDH, has been assigned to sub-band 2q33.3 by Narahara et al.4 High resolution GTG and RBA banding analysis showed that the segment 2q32. 1->q34 was deleted in the proband in agreement with their observations. On the other hand, the gene for RPE has been assigned to the segment 2q32qter by Gross et al,5 using interspecific hybridisation. From the gene dosage effect, our observations suggest that the gene for RPE is located on the more proximal portion of this segment, 2q32.1-*q34. Further studies of patients with similar deletions of the long arm of chromosome 2 are required to elucidate the critical band for the expression of RPE.