QuakingRegulatesNeurofascin 155Expression for Myelin and Axoglial Junction Maintenance

Abstract

RNA binding proteins required for the maintenance of myelin and axoglial junctions are unknown. Herein, we report that deletion of the Quaking (QKI) RNA binding proteins in oligodendrocytes (OLs) using Olig2-Cre results in mice displaying rapid tremors at postnatal day 10, followed by death at postnatal week 3. Extensive CNS hypomyelination was observed as a result of OL differentiation defects during development. The QKI proteins were also required for adult myelin maintenance, because their ablation using PLP-CreERT resulted in hindlimb paralysis with immobility at ϳ30 d after 4-hydroxytamoxifen injection. Moreover, deterioration of axoglial junctions of the spinal cord was observed and is consistent with a loss of Neurofascin 155 (Nfasc155) isoform that we confirmed as an alternative splice target of the QKI proteins. Our findings define roles for the QKI RNA binding proteins in myelin development and maintenance, as well as in the generation of Nfasc155 to maintain healthy axoglial junctions.

Transcriptome profiling of mouse brains with qkI-deficient oligodendrocytes reveals major alternative splicing defects including self-splicing

“…Experimental protocols involving animal use were approved by the McGill University Animal Care Committee. QKI FL / FL ; Olig2 - Cre and QKI FL / FL ;- mice were generated as described 2 . Exon 2 of the qkI gene is flanked with loxP sites and the recombination with Cre results in a null.…”

“…The deletion of the QKI isoforms in OLs using Olig2-Cre ( QKI FL / FL ; Olig2 - Cre ) leads to severe CNS hypomyelination with tremors by post-natal day 10 (P10) and death at the third post-natal week. Ablation of qkI in adult mice using PLP-CreERT results in hindlimb paralysis, thoracic kyphosis and immobility by the third to fourth week post-4-hydroxytamoxifen (OHT) administration 2 . This work defines the QKI isoforms as major regulators of OL differentiation and maintenance.…”

An RNA-binding protein, Qki5, regulates embryonic neural stem cells through pre-mRNA processing in cell adhesion signaling

“…In the nervous system, Qki proteins are predominantly expressed in oligodendrocyte lineage cells (Hardy et al 1996;Hardy 1998) and are key regulators of oligodendrocyte differentiation and myelination. These effects are mediated by RNA-level regulation of cell cycle-and myelin-related genes (Larocque et al 2002(Larocque et al , 2005Wu et al 2002;Darbelli et al 2016). In addition, our immunohistochemical analysis in the present study and a previous report revealed unique cellular distributions of these proteins during brain development ( Fig.…”

STARs in the CNS

“…Nfasc155 is known to be present at axoglial junctions in the spinal cord. By crossing QkI FL/FL with PLP-CreERT and inducibly deleting the quaking gene in adult mice, the investigators found defects in axoglial junctions of the spinal cords and notable loss of Nfasc155 staining [17]. Therefore, these conditional mutant mice have been used to uncover a splicing change which results in a phenotypic defect.…”

“…Genetically modified animals are very informative in vivo models to answer these questions. Currently, there are viable homozygous knockout mouse models for all the STAR proteins except SF1 which can be exploited to study alternative splicing in an intact organism (the Sf1 null mouse is lethal) [11][12][13][14][15][16][17]. The brain has been shown to have the largest amount of alternative splicing in the body [18], perhaps because of its complex function.…”