Obsl1, or obscurin-like 1, is a gene with diverse functions. It is part of the obscurin protein family, and its members play roles in muscle-related functions such as sarcolemmal integrity, sarcoplasmic reticulum organization, and muscle metabolism. It may also be involved in the regulation of insulin-like growth factor binding proteins (IGFBPs) and a ubiquitin ligase signaling mechanism related to Golgi morphology and dendrite patterning [1,3,4].

Global Obsl1 knockout mice are embryonically lethal, while skeletal muscle-specific Obsl1 knockouts show a benign phenotype similar to obscurin knockouts. Only when both obscurin and Obsl1 are deleted, their roles in sarcolemmal stability, sarcoplasmic reticulum organization, and muscle metabolism become evident. In the heart, combined loss of Obsc and Obsl1 leads to diastolic dysfunction, altered metabolism, and deregulated mitophagy [1,5].

In conclusion, Obsl1 is crucial for muscle-related functions including sarcolemmal and sarcoplasmic reticulum integrity, and metabolism. Its knockout models, especially in muscle-specific and combined knockouts with obscurin, have revealed its role in cardiac diastolic function and metabolism-related disease conditions. Mutations in Obsl1 are also associated with 3M syndrome, a growth-retardation disorder, highlighting its importance in human growth-related processes [1,2,3,5,6].