endoplasmic reticulum membrane,
integral component of lumenal side of endoplasmic reticulum membrane
Dol-P-Man:Man(7)GlcNAc(2)-PP-Dol alpha-1,6-mannosyltransferase (ALG12) (Chantret et al. 2002) normally tranfers the 8th mannose moiety to the lipid-linked oligosaccharide (LLO aka N-glycan precursor) which is required for subsequent N-glycosylation of proteins. Defects in ALG12 are associated with congenital disorder of glycosylation 1g (ALG12-CDG, CDG1g; MIM:607143), a multisystem disorder caused by a defect in glycoprotein biosynthesis and characterised by under-glycosylated serum glycoproteins (Chantret et al. 2002, Grubenmann et al. 2002). CDG type 1 diseases result in a wide variety of clinical features, such as defects in the nervous system development, psychomotor retardation, dysmorphic features, hypotonia, coagulation disorders, and immunodeficiency. Point mutations that can cause ALG12-CDG are F142V, T67M, R146Q, G101R, L158P and Y414* (Chantret et al. 2002, Grubenmann et al. 2002).