Developmental expression of FMRP in the astrocyte lineage: implications for fragile X syndrome.
One of the most common causes of mental retardation in humans, Fragile X syndrome, results from the absence of FMRP, the protein product of the FMR1 gene. In the nervous system, expression of FMRP has been thought to be confined mainly to neurons as little research has examined FMRP expression in non-neuronal lineages. We present evidence that, in addition to neuronal expression, FMRP is expressed in developing CNS glial cells in vitro and in vivo. The neurosphere assay was used to establish cultures of stem and progenitor cells from the brains of wildtype and FMRP knockout (B6.129.FMR1/FvBn) mouse pups. When the neurospheres were differentiated in vitro, approximately 50% of the FMRP positive cells also expressed GFAP. Immunocytochemical studies of the embryonic and postnatal mouse brain revealed coexpression of FMRP and GFAP in the developing hippocampus. Prominent coexpression was also observed in ependymal cells surrounding the third ventricle and astrocytes of the glia limitans. No double-labeled cells were evident in the brains of young adult mice. Cells coexpressing FMRP and the oligodendrocyte precursor marker NG2 were also identified in the hippocampus and corpus callosum of the early postnatal brain. Our results suggest that FMRP is expressed in cells of non-neuronal lineage(s) during development. This represents potential involvement of glial cells in the neural development of fragile X syndrome.
Pacey
Laura K K
LK
Department of Pathology and Molecular Medicine, Health Science Centre, HSC 1R1, McMaster University, 1200 Main Street West, Hamilton, Ontario, Canada L8N 3Z5.
Doering
Laurie C
LC
D000818:Animals; D001253:Astrocytes / Q000378:metabolism* / Q000648:ultrastructure; D001921:Brain / Q000166:cytology / Q000502:physiology; D002454:Cell Differentiation / Q000502:physiology; D019070:Cell Lineage; D002473:Cell Wall / Q000378:metabolism; D051860:Fragile X Messenger Ribonucleoprotein 1 / Q000096:biosynthesis* / Q000235:genetics; D005600:Fragile X Syndrome / Q000235:genetics* / Q000473:pathology; D018507:Gene Expression Regulation, Developmental / Q000235:genetics / Q000502:physiology; D005819:Genetic Markers; D005904:Glial Fibrillary Acidic Protein / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D051379:Mice; D018345:Mice, Knockout; D009474:Neurons / Q000502:physiology / Q000648:ultrastructure; D009836:Oligodendroglia / Q000378:metabolism / Q000648:ultrastructure; D013569:Synapses / Q000502:physiology / Q000648:ultrastructure; D020542:Third Ventricle / Q000166:cytology / Q000378:metabolism / Q000502:physiology