Murine hippocampal neurons expressing Fmr1 gene premutations show early developmental deficits and late degeneration.
Premutation CGG repeat expansions (55-200 CGG repeats; preCGG) within the fragile X mental retardation 1 (FMR1) gene give rise to the neurodegenerative disorder, fragile X-associated tremor/ataxia syndrome (FXTAS), primary ovarian insufficiency and neurodevelopmental problems. Morphometric analysis of Map2B immunofluorescence reveals that neurons cultured from heterozygous female mice with preCGG repeats in defined medium display shorter dendritic lengths and fewer branches between 7 and 21 days in vitro compared with wild-type (WT) littermates. Although the numbers of synapsin and phalloidin puncta do not differ from WT, preCGG neurons possess larger puncta. PreCGG neurons display lower viability, and express elevated stress protein as they mature. PreCGG neurons have inherently different patterns of growth, dendritic complexity and synaptic architecture discernable early in the neuronal trajectory to maturation, and may reflect a cellular basis for the developmental component of the spectrum of clinical involvement in carriers of premutation alleles. The reduced viability of preCGG neurons is consistent with the mRNA toxicity and neurodegeneration associated with FXTAS.
Chen
Yucui
Y
Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, CA 95616, USA. ycachen@ucdavis.edu
Tassone
Flora
F
Berman
Robert F
RF
Hagerman
Paul J
PJ
Hagerman
Randi J
RJ
Willemsen
Rob
R
Pessah
Isaac N
IN
D000818:Animals; D002470:Cell Survival; D003712:Dendrites / Q000235:genetics / Q000473:pathology; D051860:Fragile X Messenger Ribonucleoprotein 1 / Q000235:genetics* / Q000378:metabolism; D006570:Heterochromatin / Q000378:metabolism; D006579:Heterozygote; D006624:Hippocampus / Q000002:abnormalities* / Q000473:pathology*; D051379:Mice; D009410:Nerve Degeneration / Q000235:genetics* / Q000473:pathology*; D009474:Neurons / Q000378:metabolism / Q000473:pathology*; D010590:Phalloidine / Q000378:metabolism; D017729:Presynaptic Terminals / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D016704:Synapsins / Q000378:metabolism; D013997:Time Factors; D019680:Trinucleotide Repeat Expansion / Q000235:genetics*
D051860:Fragile X Messenger Ribonucleoprotein 1; D006570:Heterochromatin; D010590:Phalloidine; D012333:RNA, Messenger; D016704:Synapsins