Altered differentiation of neural stem cells in fragile X syndrome

doi:10.1073/pnas.0508995102

Altered differentiation of neural stem cells in fragile X syndrome

^*Neuroscience Center, University of Helsinki, P.O. Box 56, 00014 Helsinki, Finland; ^‡A. I. Virtanen Institute and ^§Department of Obstetrics and Gynecology, University of Kuopio, P.O. Box 1627, 70211 Finland; and ^¶Department of Clinical Genetics, Erasmus Medical Center, Doctor Molewaterplein 50, 3000 DR Rotterdam, The Netherlands

Communicated by William T. Greenough, University of Illinois at Urbana-Champaign, Urbana, IL, October 15, 2005 (received for review December 16, 2004)

Abstract

Fragile X syndrome, a common form of inherited mental retardation, is caused by the absence of the fragile X mental retardation protein (FMRP) due to a mutation in the FMR1 gene. We investigated the differentiation of neural stem cells generated from the brains of fmr1-knockout (KO) mice and from postmortem tissue of a fragile X fetus. Mouse and human FMRP-deficient neurospheres generated more TuJ1-positive cells (3-fold and 5-fold, respectively) than the control neurospheres generated from normal mouse and human brains, and these cells showed morphological alterations with fewer and shorter neurites and a smaller cell body volume. The number of cells expressing glial fibrillary acidic protein and generated by these neurospheres was reduced because of increased apoptotic cell death. Furthermore, there was an increase in a population of cells with intense oscillatory Ca²⁺ responses to neurotransmitters in differentiated cells lacking FMRP. In addition, the number of cells in a cohort of bromodeoxyuridine-labeled newborn cells was increased in the subventricular zone of the telencephalon of the fmr1-KO mouse in vivo. These results demonstrate substantial alterations in the early maturation of FMRP-deficient neural stem cells in fragile X syndrome and in the fmr1-KO mice.

Footnotes

↵ † To whom correspondence should be addressed. E-mail: maija.castren{at}helsinki.fi.
Author contributions: M.C. and K.Å. designed research; M.C., T.T., and V.K. performed research; S.H., C.E.B., and B.A.O. contributed new reagents/analytic tools; M.C., T.T., V.K., and K.L. analyzed data; and M.C., E.C., and K.Å. wrote the paper.
Conflict of interest statement: No conflicts declared.
Abbreviations: KO, knockout; FMRP, fragile X mental retardation protein; NSC, neural stem cell; mGluR, metabotropic glutamate receptor; E13, embryonic day 13; P6, postnatal day 6; [Ca²⁺]_i, intracellular Ca²⁺; ACh, acetylcholine; MPEP, 2-methyl-6-(phenylethynyl)pyridine; SVZ, subventricular zone.