Biallelic loss-of-function mutations in TRIP11, encoding the golgin GMAP-210, cause the lethal human chondrodysplasia achondrogenesis 1A (ACG1A). We now find that a homozygous splice-site mutation of the lamin B receptor (LBR) gene results in the same phenotype. Intrigued by the genetic heterogeneity, we compared GMAP-210– and LBR-deficient primary cells to unravel how particular mutations in LBR cause a phenocopy of ACG1A. We could exclude a regulatory interaction between LBR and GMAP-210 in patients’ cells. However, we discovered a common disruption of Golgi apparatus architecture that was accompanied by decreased secretory trafficking in both cases. Deficiency of Golgi-dependent glycan processing indicated a similar downstream effect of the disease-causing mutations upon Golgi function. Unexpectedly, our results thus point to a common pathogenic mechanism in GMAP-210– and LBR-related diseases attributable to defective secretory trafficking at the Golgi apparatus.
Anika Wehrle, Tomasz M. Witkos, Judith C. Schneider, Anselm Hoppmann, Sidney Behringer, Anna Köttgen, Mariet Elting, Jürgen Spranger, Martin Lowe, Ekkehart Lausch
C14 sterol reductase activity is impaired in LBR-deficient cells.