Date of Award

Fall 8-16-2024

Level of Access Assigned by Author

Open-Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biomedical Sciences

Advisor

Gregory Cox

Second Committee Member

Robert Burgess

Third Committee Member

Catherine Kaczorowski

Additional Committee Members

Dustin Updike

Bruce O'Hara

Abstract

Orphan diseases, or diseases that affect less than 200,000 people around the globe, are less extensively researched leaving patients with questions and often without treatments let alone a cure. Developing models to research orphan diseases requires documentation of the few human patients suffering from the disease, development of a model, and extensive phenotyping of that model to determine viability as a translatable model of the disease. This dissertation is in itself rare as it follows the development of an animal model all the way through to human clinical trials of an Investigational New Drug. The disease of interest is a severe neuromuscular degenerative disease called Spinal Muscular Atrophy with Respiratory Distress type 1, or SMARD1, affecting young children. This disease is caused by recessive mutations in IGHMBP2 and marked by diaphragmatic paralysis within the first years of life leading to respiratory distress followed by severe muscular atrophy starting in the distal limbs. However, there is phenotypic severity with some milder cases occurring later in childhood not always accompanied by respiratory distress categorized as a Charcot-Marie-Tooth disease type 2S (CMT2S) and even some more severe cases initially diagnosed as Sudden Infant Death Syndrome (SIDS). As such, to reflect the range of disease severity, the Cox lab made several models via CRISPR. The 11 alleles made encompass off-target mutations as well as human alleles. Through histological analysis of key muscles

and nerves and genetic crosses of transgenic models, the spectrum of severity has been documented as well as the fact that IGHMBP2 associated diseases are neurogenic though do impact muscle as well. To test respiratory distress of these animals, the PiezoSleep system was troubleshooted to analyze breath rate and it was found that there is indeed respiratory distress in our severe models. RNAseq of the spinal cords also indicated that the RNA sensing innate immune system pathway, the RIG-I Like Receptor pathway, played a part in these diseases as well as NEMF associated diseases. Due to these models and phenotyping, we were able to test gene therapy in these models finding that treatment greatly mitigated the NMD phenotype and lengthened lifespan. The creation and characterization, of rare disease models are vital to creating and testing therapeutics. The relationship between IGHMBP2 and NEMF also shows potential for finding novel categories of neuromuscular disease opening up avenues for treatments that treat a larger amount of patients as well as increase our understanding of neuromuscular development and maintenance.

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