Signaling defects in iPSC-derived fragile X premutation neurons.
Fragile X-associated tremor/ataxia syndrome (FXTAS) is a leading monogenic neurodegenerative disorder affecting premutation carriers of the fragile X (FMR1) gene. To investigate the underlying cellular neuropathology, we produced induced pluripotent stem cell-derived neurons from isogenic subclones of primary fibroblasts of a female premutation carrier, with each subclone bearing exclusively either the normal or the expanded (premutation) form of the FMR1 gene as the active allele. We show that neurons harboring the stably-active, expanded allele (EX-Xa) have reduced postsynaptic density protein 95 protein expression, reduced synaptic puncta density and reduced neurite length. Importantly, such neurons are also functionally abnormal, with calcium transients of higher amplitude and increased frequency than for neurons harboring the normal-active allele. Moreover, a sustained calcium elevation was found in the EX-Xa neurons after glutamate application. By excluding the individual genetic background variation, we have demonstrated neuronal phenotypes directly linked to the FMR1 premutation. Our approach represents a unique isogenic, X-chromosomal epigenetic model to aid the development of targeted therapeutics for FXTAS, and more broadly as a model for the study of common neurodevelopmental (e.g. autism) and neurodegenerative (e.g. Parkinsonism, dementias) disorders.
Stem Cell Program and Institute for Regenerative Cures, Health System, University of California, Davis, Health System, Sacramento CA, 95817, USA.
Jing
J
Liu
Katarzyna A
KA
Koscielska
Zhengyu
Z
Cao
Susan
S
Hulsizer
Natalie
N
Grace
Gaela
G
Mitchell
Catherine
C
Nacey
Jackline
J
Githinji
Jeannine
J
McGee
Dolores
D
Garcia-Arocena
Randi J
RJ
Hagerman
Jan
J
Nolta
Isaac N
IN
Pessah
Paul J
PJ
Hagerman
D000200:Action Potentials; D000483:Alleles; D002118:Calcium / Q000378:metabolism; D002454:Cell Differentiation; D002999:Clone Cells; D005260:Female; D005347:Fibroblasts / Q000378:metabolism / Q000473:pathology; D051860:Fragile X Messenger Ribonucleoprotein 1 / Q000235:genetics / Q000378:metabolism; D005600:Fragile X Syndrome / Q000235:genetics* / Q000473:pathology* / Q000503:physiopathology; D005786:Gene Expression Regulation; D006801:Humans; D057026:Induced Pluripotent Stem Cells / Q000378:metabolism*; D008875:Middle Aged; D009154:Mutation / Q000235:genetics*; D009474:Neurons / Q000378:metabolism* / Q000473:pathology*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics*; D013569:Synapses / Q000378:metabolism / Q000473:pathology; D014019:Tissue Donors; D049951:X Chromosome Inactivation / Q000235:genetics
D002118:Calcium; D051860:Fragile X Messenger Ribonucleoprotein 1; D012333:RNA, Messenger