Gerodermia osteodysplastica is caused by mutations in SCYL1BP1, a Rab-6 interacting golgin

Abstract

Gerodermia osteodysplastica is an autosomal recessive disorder characterized by wrinkly skin and osteoporosis. Here we demonstrate that gerodermia osteodysplastica is caused by loss-of-function mutations in SCYL1BP1, which is highly expressed in skin and osteoblasts. The protein localizes to the Golgi apparatus and interacts with Rab6, identifying SCYL1BP1 as a golgin. These results associate abnormalities of the secretory pathway with age-related changes in connective tissues.

Figure 1. Clinical features of gerodermia osteodysplastica (GO), identification of mutations in SCYL1BP1, and characterization of SCYL1BP1 as a golgin

(a) 9-month old patient. Note the typical facial appearance with sagging cheeks and pronounced wrinkling at the chest and dorsum of the hands giving him a prematurely aged appearance. (b) Haplotype analysis in four Mennonite pedigrees in the candidate region on chromosome 1q24. The shared haplotype defined a 5.1-cM candidate interval and indicated homozygosity by descent and a common founder in the patients from Germany, Canada, and Mexico. The boxes mark the respective homozygous intervals. (c) Schematic representation of the SCYL1BP1 structure showing coiled-coil domains (CC), the uncharacterized domain DUF622, and the nine different mutations found in GO families. (d) GO mutations lead to a complete loss of the protein as shown in a Western blot analysis of patient fibroblast lysates. C1-C3, control fibroblasts. (e) Co-staining of SCYL1BP1 with various Golgi marker proteins in control cells. Signals of γ-adaptin were in the same compartment but did not overlap completely. Co-localization with Rab6 pointed to the localization in the trans-Golgi network. Co-staining with Golgi matrix protein GM130 excluded a localization in the cis-Golgi compartment. Scale bar 10 μm. (f) Yeast two-hybrid screening against a library of ARF, Arl, and Rab small GTPases. Growth on selective medium indicated interaction with Rab6a and Rab6b. (g) Confirmation of the Rab6 interaction by pull-down experiments. A GST-Rab6 fusion protein was used to pull down SCYL1BP1 from HeLa lysates without or in the presence of GTP. Active GTP-bound Rab6 pulled down SCYL1BP1 efficiently while the GDP-locked T27N mutant was unable to interact.