ALG14 encodes a subunit of the UDP-N-acetylglucosamine transferase complex essential for N-linked glycoprotein biosynthesis 1. As a protein-membrane adapter, ALG14 recruits ALG13 at the endoplasmic reticulum cytoplasmic face, catalyzing the second step of dolichol-linked oligosaccharide assembly by transferring N-acetylglucosamine from UDP-GlcNAc to produce N,N'-diacetylchitobiosyl diphosphodolichol 1. This intermediate serves as substrate for subsequent glycosylation pathway enzymes. ALG14 complex formation depends critically on C-terminal interactions between ALG13 and ALG14 1. Pathogenic ALG14 variants cause congenital disorders of glycosylation with diverse clinical presentations. Mutations are associated with congenital myasthenic syndromes characterized by neuromuscular junction dysfunction 23, and expanded phenotypes including severe early neurodegeneration, progressive cerebral atrophy, therapy-refractory epilepsy, and myopathy with fatal outcomes typically in infancy 4. ALG14 variants also contribute to myopathies with tubular aggregates, where reduced protein expression impairs glycosylation pathways 5. These glycosylation defects underscore ALG14's critical role in proper protein folding and neuromuscular function, making it essential for normal neurodevelopment and muscle physiology.