Microdeletions of the 22q11 region, responsible for the velo-cardio-facial syndrome (VCFS), are associated with an increased risk for psychosis and mental retardation. Recently, it has been shown in a hyperprolinemic mouse model that an interaction between two genes localized in the hemideleted region, proline dehydrogenase (PRODH) and catechol-o-methyl-transferase (COMT), could be involved in this phenotype. Here, we further characterize in eight children the molecular basis of type I hyperprolinemia (HPI), a recessive disorder resulting from reduced activity of proline dehydrogenase (POX). We show that these patients present with mental retardation, epilepsy and, in some cases, psychiatric features. We next report that, among 92 adult or adolescent VCFS subjects, a subset of patients with severe hyperprolinemia has a phenotype distinguishable from that of other VCFS patients and reminiscent of HPI. Forward stepwise multiple regression analysis selected hyperprolinemia, psychosis and COMT genotype as independent variables influencing IQ in the whole VCFS sample. An inverse correlation between plasma proline level and IQ was found. In addition, as predicted from the mouse model, hyperprolinemic VCFS subjects bearing the Met-COMT low activity allele are at risk for psychosis (OR = 2.8, 95% CI = 1.04-7.4). Finally, from the extensive analysis of the PRODH gene coding sequence variations, it is predicted that POX residual activity in the 0-30% range results into HPI, whereas residual activity in the 30-50% range is associated either with normal plasma proline levels or with mild-to-moderate hyperprolinemia.

Laterality (hand, foot, ear, and eye) was assessed in participants with Trisomy 21 (62) and Williams-Beuren syndrome (WBS) (39). Handedness was also assessed in a card reaching task. The comparison group included 184 typically developing persons. Two independent age sub-groups were formed: 7 to 10 years old and 11 to 34 years old. We confirmed previous data: individuals with T21 were more frequently left- or mixed-handed than typically developing persons; individuals with WBS had intermediate scores. The two groups with genetic disorders had less right foot preference. Manual and foot inconsistencies characterized both groups with genetic disorders. Cross hand-foot preference was lower in the typically developing group. Differences in IQ levels did not correlate with differences in laterality scores. Overall laterality profiles were not the same in the two groups with genetic disorders: the greatest differences were observed between typically developing persons and persons with Trisomy 21.