Spinal Muscular Atrophy with Respiratory Distress Type I (SMARD1) is a devastating neurodegenerative disease with no effective treatment or cure. SMARD1 is caused by mutations within the IGHMPB2 gene, encoding a ubiquitously expressed multi-functional protein. Disease-causing patient mutations are scattered throughout IGHMPB2 and within its various biochemical domains such as the helicase domain, the ATP binding pocket, and the nucleic acid binding region; however, the precise IGHMBP2-associated function responsible for disease development is currently unknown. To date, the bulk of the in vivo analyses has centered upon the mouse ?nmd? model of SMARD1. The SMARD1 mouse carries a single spontaneous mutation within intron 4 of IGHMBP2, giving rise to an aberrant splicing event in ~75-80% of the IGHMPB2 transcripts. Our lab has recently demonstrated that early delivery of AAV9-IGHMBP2 has exciting promise for therapeutic application. While this rodent model has been a valuable resource, the reality is that to move forward from a translational perspective, additional models will provide robust experimental contexts for novel therapeutics, such as gene therapy. There are several reasons why SMARD1 research will specifically benefit from a large animal model: 1) the ability to evaluate the respiratory phenotypes associated with SMARD1 via imaging, respiratory tests and tissue collection is key and not truly possible in mice, 2) the ability to collect tissue from distinct regions of the muscles, nervous system and organs, 3) size, development and metabolism in swine are more consistent with humans when considering therapeutic applications, 4) the ability to evaluate therapeutic efficacy based on intrathecal delivery in swine which is currently utilized for therapeutic delivery in SMA patients and not possible in mice, and 5) the ability to examine intrauterine growth and development. There is a range of phenotypes associated with SMARD1 as it pertains to disease onset, severity of symptoms and disease progression; however, there is no clear correlation between mutation type and clinical presentation. Our overreaching goal is to have animals that have four mutations analogous to the human mutations C496X, D565N, R603C, and R605X. Towards that goal, we have targeted fetal fibroblast cells with the corresponding D565N mutation and are performing SCNT/ETs. We anticipate that these different mutations will allow us to shed light on the function of IGHMBP2 and its role in SMARD1 development. The SMARD1 swine will be generated utilizing the CRISPR technology (Clustered Regularly Interspaced Short Palindromic Repeats) to facilitate the introduction of site-specific mutations through homology-directed repair of the endogenous swine IGHMBP2 gene. Leveraging the experience of the research team, we are well positioned to successfully complete this project and provide important biological models as well as models for therapeutic analysis to the research community.
Spinal Muscular Atrophy with Respiratory Distress Type I (SMARD1) is a devastating neurodegenerative disease with no effective treatment or cure. This project is designed to develop important models of disease that will shed light upon the underlying function responsible for disease development as well as provide a valuable disease context to develop novel SMARD1 therapeutics. !
