Reducing pathological accumulations of phosphorylated Neurofilament-H through modulation of Pin1 activity: Implications in Amyotrophic Lateral Sclerosis

Abstract

One of the pathological hallmarks of motor neuron death in Amyotrophic Lateral Sclerosis (ALS) is the abnormal accumulations of phosphorylated neurofilaments in the neuronal cell body. Previous reports suggested that Pin1, a prolyl-isomerase that catalyses the cis-trans isomerisation of the phosphorylated serine/threonine-proline motifs, may be responsible for the aberrant accumulations of phosphorylated neurofilament heavy chain (p-NF-H) in neurons, which are observed during neurotoxicity. The aim of this thesis is to investigate the reduction of aberrant p-NF-H accumulations through knockdown of Pin1 activity using recombinant adeno-associated virus (AAV)-mediated transduction of Pin1 shRNA in vivo in the G93A SOD1 ALS mouse model. This was achieved using the Pin1 shRNA construct, which showed effective and stable knockdown of Pin1 in HEK 293T/17 cells and in primary neuronal cultures. To produce an in vivo gene delivery system into the spinal motor neurons by intramuscular route of administration, the transduction efficiencies of AAV serotypes 1, 2, 5, 6, 8 and 9 were compared. AAV9 yielded the highest level of motor neuron transduction in the spinal cord and was used for Pin1 shRNA gene delivery. Accumulations of p-NF-H in the spinal motor neurons of G93A SOD1 transgenic mice were observed prior to motor neuron cell death, astrocyte activation and behavioural deficits. This suggested that early prevention of p-NF-H accumulations may be beneficial. The spinal motor neurons transduced with AAV9-Pin1 shRNA showed significant reduction in aberrant p-NF-H accumulations indicating the Pin1 knockdown strategy may be of therapeutic potential in reducing the neurotoxic accumulations in ALS.