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Title: Modelling SMA using induced pluripotent stem cells from a discordant affected family
Author: Boza Moran, Maria
Awarding Body: Royal Holloway, University of London
Current Institution: Royal Holloway, University of London
Date of Award: 2013
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Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disease in which low levels of survival of motor neuron (SMN) protein lead to the degeneration of alpha motor neurons (MNs) in the spinal cord. The pathological mechanism of SMA is highly controversial and until recently it was not possible to obtain human MNs to study the disease. The development of induced pluripotent stem cell (iPSC) technology has made it possible to bypass this obstacle and iPSC-based models of SMA type I have already been validated by two separate groups. Encouraged by these pioneering findings I have produced and characterized iPSCs from several members of a discordant consanguineous family in which four haploidentical siblings share the same homozygous SMNl mutation, but nonetheless show different phenotypes of the disease. I have differentiated iPSC clones from three of the siblings and the carrier unaffected mother, as well as a control unaffected clone and a clone derived from a patient with SMA type I, into ISL1+/ChAT+ MNs. No obvious phenotypic difference was observed between the MN cultures of the siblings during the period of study, but cells from the SMA type I patient did show an impaired ability to form rosettes. The study of SMN and PLS3 levels during the differentiation from iPSCs to ChAT+ MNs showed a gradual decay of these proteins during MN development in all clones. Furthermore, SMN protein levels did not correlate with the pattern of mRNA expression, c suggesting the existence of post-transcriptional and/or post-translational regulation of full-length SMN (FL-SMN) transcripts and protein. The FL/.d7-SMN mRNA ratio and total SMN (tSMN) mRNA levels were found to be possible biomarkers to distinguish unaffected individuals from SMA patients and the severity of SMA pathology, respectively. PLS3 protein level was higher in the SMA type IV/asymptomatic sibling than in two of the type III SMA siblings, but it could not be confirmed as a modifier factor in the family. These results suggest that SMN levels are regulated during MN development, and that low levels may impair the generation of rosettes but not necessarily of MNs. SMN levels in MNs only show minor differences between patients, suggesting that there may be a threshold after which reduced levels of SMN within a narrow range become suddenly and increasingly detrimental unless modifier factors can compensate for the cellular function(s) lost. 3
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Spinal Muscular Atrophy ; Stem Cells ; Induced Pluripotent Stem Cells ; Motor Neurons