Does spastin expression occur in a tissue-specific manner to confer a synaptic mutant phenotype?

Author: Shibani Mallik

Mentor: Nina Tang Sherwood, Ph.D.

Department of Biology

Spastin is a microtubule-severing protein important for microtubule degradation and growth. Spastin mutations in humans are known to cause Autosomal Dominant Hereditary Spastic Paraplegia (AD-HSP), a neurodegenerative disease of the motor system. Ubiquitous deletion of spastin in Drosophila also causes motor defects in adult flies, as well as defects in synaptic bouton morphology and function. While spastin is thought to be expressed in neurons, the true site of action of Spastin remains unknown. This study used the CRISPR-Cas9 genome-editing tool to generate spastin deletions in only neurons or glia using tissue-specific drivers, along with ubiquitous drivers, to discover Spastin’s site of action. This was accomplished through a series of genetic crosses, larval dissection, and immunofluorescence microscopy to visualize boutons at the neuromuscular junction. This study also evaluated the efficacy of using CRISPR-Cas9 as an editing tool in Drosophila. If Spastin is required only in specific tissues, then the larvae with certain tissue-specific drivers will display the mutant phenotype. A ubiquitous driver should also display the mutant phenotype, depending on the functionality of the CRISPR-Cas9 system. This study has important implications for future therapy development for AD-HSP and future projects on the spastin gene, among others implicated in microtubule development.

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