OBSL1 (obscurin like cytoskeletal adaptor 1) is a cytoskeletal adaptor protein that functions as a core component of the 3M complex, which regulates microtubule dynamics and genome integrity 1. The protein physically interacts with CCDC8 and participates in a growth-regulatory pathway alongside CUL7 and CCDC8 that controls mammalian growth 1. OBSL1 acts as a regulator of the Cul7-RING(FBXW8) ubiquitin-protein ligase and is required to localize CUL7 to the Golgi apparatus in neurons. In striated muscle, OBSL1 shows functional redundancy with obscurin, playing roles in sarcolemmal stability, sarcoplasmic reticulum organization, and muscle metabolism 2. Biallelic mutations in OBSL1 cause 3M syndrome 2, an autosomal recessive disorder characterized by severe pre- and post-natal growth retardation, facial dysmorphism, and normal intelligence 34. OBSL1 mutations account for approximately 16-44% of 3M syndrome cases 34. Cellular studies reveal that OBSL1-deficient cells show impaired signaling responses to both growth hormone and IGF1, suggesting dysregulation of the GH-IGF axis contributes to growth restriction 5. The phenotypic spectrum associated with OBSL1 mutations can include atypical features such as disproportionate short stature, thoracic abnormalities, and hypogonadism 6.