Biology subjects

Hartl, T. A.

Publications and source records attributed to Hartl, T. A..

2 recordsLinked to original sources

bioRxiv2026

Sequence determinants of efficient exon 44 skipping in Duchenne muscular dystrophy define design principles for steric-blocking antisense oligonucleotides

Duchenne muscular dystrophy (DMD) is caused by mutations in the DMD gene that disrupt the reading frame and abolish expression of functional dystrophin protein. Antisense oligonucleotides (ASO) can restore production of partially functional dystrophins by inducing exon skipping to restore the reading frame of dystrophin transcripts. While exon skipping is an FDA approved therapeutic strategy, there are currently no approved therapies for patients amenable to exon 44 skipping (8% of DMD patients). Here, we carried out a discovery campaign to identify phosphorothioate (PS) ASOs that efficiently induce exon 44 skipping and to define key sequence and chemistry features associated with activity. A tiling and micro-tiling approach with 18mer fully PS and 2-O-methoxyethyl (2MOE) modified ASOs in patient-derived myotubes identified five exonic target regions that promote skipping. ASO activity was strongly correlated across skeletal muscle and iPSC-derived cardiomyocytes, indicating similar exon 44 splicing regulation across cell types. Optimization studies showed that for 2MOE PS ASOs, 16-20mers were generally most active, while longer ASOs often had reduced activity due in part to impaired productive uptake into cells. Swapping out 2MOE modifications at both terminal positions for locked nucleic acids (LNAs) rarely improved activity and could also reduce it. Finally, promising candidates were tested in a humanized mouse model with an exon 44 skippable deletion, where one ASO outperformed others, inducing dose-dependent exon 44 skipping and dystrophin restoration in mouse models. These findings define practical design rules for exon 44-targeted ASOs and provide a foundation for therapeutic development.

molecular biology↗

bioRxiv2021

Multi-Species Phenotypic Screening across Disease Models of Mucolipidosis Type IV

Invertebrate model organisms (the nematode Caenorhabditis elegans and the fruit fly Drosophila melanogaster) are valuable tools to bridge the gap between traditional in vitro discovery and preclinical animal models. Invertebrate model organisms are poised to serve as better disease models than 2D cellular monocultures for drug discovery, as well as easier and more cost-effective to scale up than 3D organoids/assembloids or co-cultures. A strength of model organisms is the opportunity to probe conserved biology such as lysosomal function and autophagy in a physiological setting. However, invertebrate models are not without pharmacokinetic and pharmacodynamic challenges, such as poor tissue penetration and confidence in a compounds mechanism of action. To confront those challenges, we took advantage of the Novartis mechanism-of-action box (MoA Box), a compound library of well-annotated and drug-like chemical probes. Curious as to how the MoA Box, comprised of chemical probes optimized for mammalian targets, would fare in an invertebrate setting we screened the MoA Box across three different models of the lysosomal storage disease mucolipidosis Type IV (MLIV). MLIV is caused by mutations in the lysosomal transient receptor potential ion channel mucolipin-1 (TRPML1) resulting in hyper-acidic lysosomes and dysregulated autophagy. The overlap of screening hits from worm, fly, and patient fibroblast screens identified cyclin-dependent kinase (CDK) inhibition as an evolutionarily conserved disease modifier and potential drug repurposing strategy. Summary statementA trio of phenotypic screens across Drosophila, C. elegans, and H. sapiens models of mucolipidosis IV was performed and identified overlapping hits including cyclin-dependent kinase inhibitors.

cell biology↗