Unusual subcellular confinement of the fragile X mental retardation protein (FMRP) in circulating human platelets: complete polyribosome dissociation.

FMRP, a RNA-binding protein, was shown in association with polyribosomes in every cell types studied so far, suggesting a ubiquitous role as a translational regulator. Platelets are known for their limited protein synthesis potential. However, current investigations put forward that RNA metabolism is more developed than previously thought. Unexpectedly, our results provide evidence that FMRP, in platelets, is not constitutively associated with heavy particles, such as polyribosomes, and possesses a sedimentation coefficient of less than 10S contrasting with values of 150 to 500S as reported in other cell types. In summary, this report brings to light platelets as a simple human biological system to delineate novel FMRP functions as well as strengthening our comprehension of the pathophysiology of the fragile X syndrome which results from the absence of FMRP.