Fragile X astrocytes induce developmental delays in dendrite maturation and synaptic protein expression.
BACKGROUND
Fragile X syndrome is the most common inherited form of mental impairment characterized by cognitive impairment, attention deficit and autistic behaviours. The mouse model of Fragile X is used to study the underlying neurobiology associated with behavioral deficiencies. The effect of Fragile X glial cells on the development of neurons has not been studied. We used a co-culture technique in combination with morphometrics on immunostained neurons to investigate the role of astrocytes in the development delays associated with hippocampal neuron development.


RESULTS
We found that hippocampal neurons grown on Fragile X astrocytes exhibited a significant difference from the neurons grown with normal astrocytes after 7 days in vitro for many parameters including increases in dendritic branching and in area of the cell body. However, after 21 days in culture, the neurons grown on Fragile X astrocytes exhibited morphological characteristics that did not differ significantly from the neurons grown on normal astrocytes. With antibodies to the pre-synaptic protein, synapsin, and to the excitatory post-synaptic protein, PSD-95, we quantified the number of developing excitatory synapses on the dendrites. In addition to the delays in dendritic patterning, the development of excitatory synapses was also delayed in the hippocampal neurons.


CONCLUSIONS
These experiments are the first to establish a role for astrocytes in the delayed growth characteristics and abnormal morphological features in dendrites and synapses that characterize the Fragile X syndrome.
Department of Pathology & Molecular Medicine, McMaster University, 1200 Main Street West, Hamilton, Ontario, L8N 3Z5, Canada.
Shelley
S
Jacobs
Meera
M
Nathwani
Laurie C
LC
Doering
D000818:Animals; D001253:Astrocytes / Q000378:metabolism* / Q000473:pathology* / Q000648:ultrastructure; D048429:Cell Size; D002478:Cells, Cultured; D018920:Coculture Techniques; D003712:Dendrites / Q000378:metabolism* / Q000473:pathology* / Q000648:ultrastructure; D000076122:Disks Large Homolog 4 Protein; D051860:Fragile X Messenger Ribonucleoprotein 1 / Q000235:genetics / Q000378:metabolism; D005600:Fragile X Syndrome / Q000378:metabolism* / Q000473:pathology*; D051528:Guanylate Kinases; D006624:Hippocampus / Q000166:cytology; D007150:Immunohistochemistry; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins / Q000096:biosynthesis; D051379:Mice; D018345:Mice, Knockout; D008856:Microscopy, Fluorescence; D009419:Nerve Tissue Proteins / Q000096:biosynthesis; D013569:Synapses / Q000378:metabolism* / Q000473:pathology* / Q000648:ultrastructure; D016704:Synapsins / Q000096:biosynthesis / Q000235:genetics
D000076122:Disks Large Homolog 4 Protein; D051860:Fragile X Messenger Ribonucleoprotein 1; D051528:Guanylate Kinases; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D016704:Synapsins; C501447:Dlg4 protein, mouse