Fragile X protein expression is linked to visual functions in healthy male volunteers.

Fragile X syndrome (FXS) is characterized by the impairment of the magnocellular/dorsal visual system. In this study, we explored how fragile X protein (FMRP) expression may affect visual functions in healthy participants. The percentage of FMRP-positive lymphocytes was measured using a rapid antibody test in blood smears of 100 male volunteers. CGG triplet expansion was also determined. Results revealed that participants with fewer FMRP-positive lymphocytes exhibited lower performances on tests biasing information processing toward the magnocellular pathway and dorsal visual stream (contrast sensitivity at low spatial/high temporal frequency and motion coherence). It was not observed in the case of tests biasing information processing toward the parvocellular pathway and ventral stream (contrast sensitivity at high spatial/low temporal frequency and form coherence). These results suggest that healthy persons with lower peripheral FMRP expression display a visual phenotype similar to that described in patients with FXS.