Translational research of the quaking gene : Focusing on the conjunction between development and disease

Sammanfattning: Quaking (QKI) is an RNA binding protein involved in the post-transcriptional regulation of gene expression. Originally identified as the cause of hypomyelination in a mouse mutant, it has since been consistently implicated in a wide range of neurological diseases. As a gene exclusively expressed in glial cells of the central nervous system, such associations emphasise the importance of an indirect, or non-neuronal link to aberrant neural function. A role in early neural development has also been suggested from the viable and embryonic lethal mouse mutants, yet detailed and in vivo study has been precluded thus far by the murine uterine gestation, and mutant lethality prior to oligodendrogenesis. This thesis examines the role of QKI in human neurological disease, and explores the use of the zebrafish as a model organism to allow the unimpeded study of neural development.We first examined the expression of QKI in human post-mortem brain samples, in separate studies of Alzheimer’s disease (AD) and schizophrenia. In AD we found that QKI and the splice variants QKI5, QKI6, and QKI7 were all significantly upregulated, and were additionally implicated in the regulation of genes related to AD pathogenesis. Within schizophrenic samples, we explored the expression of QKI6B, a newly identified splice variant of QKI, alongside GFAP. We found that both were significantly upregulated, and a previously implicated regulation of GFAP by QKI was supported. In order to advance investigations of the potential of QKI to disturb neural development, we established the suitability of zebrafish for studying qki. This was achieved through phylogenetic and syntenic analysis, coupled with examination of the qki genes expression patterns. We found that qkib and qki2 are orthologues of human QKI, and both have distinct, yet overlapping expression patterns in neural progenitors, and are not found in differentiated neurons. Following from this, we explored the effects of knockdown to qkib and qki2, finding that qkib exclusively led to aberrant motor neuron development, cerebellar abnormalities, and alterations to the progenitor domain. This clearly demonstrated the crucial role of qki in early neural development, and confirms a previously speculated, yet occluded, function prior to oligodendrogenesis.