Both Congenital Disorders of Glycosylation (CDGs) and dystroglycanopathies are clinically heterogenous,
multisystem disorders that can lead to severe progressive neural and muscular degeneration, which
deleteriously impacts quality of life and is frequently lethal. CDGs are marked by disrupted glycan biosynthesis,
while dystroglycanopathies stem from disrupted glycosylation of dystroglycan (DG), a critical transmembrane
receptor that anchors the intracellular cytoskeleton to the surrounding extracellular matrix. Post-translational
modifications, such as glycosylation, are critical for skeletal muscle development, growth, and homeostasis, so
it is not surprising that disrupted glycosylation can lead to disease. Healthy muscle also requires the
development of neuromuscular junctions (NMJs), which contain cell-matrix adhesion complexes replete with
glycosylated proteins, for neuromuscular crosstalk to occur. In the context of CDGs and dystroglycanopathies,
it is still unknown whether muscle tissue or neural tissue degenerates first, driving disease progression.
Important questions that remain unanswered include: (1) which tissue or tissues that express genes associated
with dystroglycanopathy should be targeted to mitigate degeneration and disease progression, and (2) which
aspects of neuromuscular degeneration are specifically due to the disruption of DG glycosylation versus
disruption of other proteins. The ability to address these questions has been hindered by the lack of viable
vertebrate models to facilitate the discovery of tissue-specific impacts of disrupted glycosylation on cell-matrix
adhesion throughout embryonic development and disease progression. To address this, I have generated a
zebrafish model through CRISPR/Cas9 gene editing of a known dystroglycanopathy gene, dolichol-phosphate
mannosyltransferase subunit 3 (dpm3), which assists in the generation of a foundational mannose residue as a
building block for the glycosylation of DG. Importantly, my model recapitulates the phenotypic variation and
disease progression observed in human dpm3 patients. Through use of dpm3 zebrafish mutants, as well as
dpm3;dg double mutants, I have developed models to elucidate which aspects of Dpm3 function are DG-
dependent and DG-independent in disease progression. I propose to use these models to address my long-
term goal of elucidating tissue-specific impacts of glycosylation during neuromuscular development and
homeostasis. I will leverage my unique genetic model to accomplish two aims: (1) Elucidate tissue-specific
roles for dpm3 during development and homeostasis, and (2) Determine which aspects of Dpm3 protein
function are dependent on versus independent of dystroglycan. Completing these aims will provide a critical
foundation for understanding the basic biology underlying abnormal neuromuscular development in CDGs and
dystroglycanopathies, serving as a basis for identifying future therapeutic targets and significantly impacting
the field of neuromuscular development and homeostasis.
