Description
- Abstract:
- Christianson syndrome (CS) is an X-linked, monogenic, neurological disorder caused by mutations in SLC9A6, the gene encoding Na+/H+ exchanger 6 (NHE6). Symptoms of CS include intellectual disability, autistic features, epilepsy, ataxia, microcephaly, non-verbal status, and hyperkinesis. CS is one of the most common forms of X-linked intellectual disability; however, the cellular mechanisms driving CS are not fully understood. NHE6 localizes to endosomes which function to transport membranes and proteins from the plasma membrane for turnover in the lysosome or recycling back to the cell surface. Endosomal pH decreases along the endocytic vesicle trafficking pathway from early endosomes to lysosomes. In order to regulate endosomal pH, NHE6 functions as a proton leak allowing protons to move from the endosomal lumen to the cytosol in exchange for sodium ions. Proper trafficking through the endosomal system is critical for the health and growth of neurons. CS patient-derived iPSCs differentiated to cortical forebrain neurons provide an invaluable system for investigation of CS disease mechanisms. We have generated iPSCs from CS patients and paired unaffected siblings. Expression of NHE6 protein and mRNA is undetectable or reduced in CS iPSCs. iPSCs differentiated to cortical neuronal fate by dual SMAD inhibition express markers of cortical layers at timepoints mirroring in vivo development. The growth and branching of neurites was evaluated using confocal imaging followed by reconstruction in Neurolucida. A decrease in neurite length and number of branchpoints was seen in CS neurons as compared to control. We tested the extent of arborization rescue by cell autonomous and non autonomous methods. Further, we investigated the intraendosomal pH of CS iPSC-derived neurons using ratiometric live imaging of fluorescently tagged transferrin. The defects in neurite growth and arborization observed in CS iPSC-derived neurons may link to the microcephaly, intellectual disability, and other neurological symptoms seen in CS patients. The establishment of an iPSC model for CS has identified critical disease mechanisms and potential therapies while providing a platform for future drug discovery.
- Notes:
- Thesis (Ph. D.)--Brown University, 2017
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Citation
Maguire, Abbie Madeline,
"Investigating Christianson syndrome neuronal development in induced pluripotent stem cells"
(2017).
Molecular Biology, Cell Biology, and Biochemistry Theses and Dissertations.
Brown Digital Repository. Brown University Library.
https://doi.org/10.7301/Z01G0JRP
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Molecular Biology, Cell Biology, and Biochemistry Theses and Dissertations
Theses and Dissertations for the Molecular Biology, Cell Biology, and Biochemistry department....