title: Mutations causing Greenberg dysplasia but not Pelger anomaly uncouple enzymatic from structural functions of a nuclear membrane protein.
abstract: The lamin B receptor (LBR) is an inner nuclear membrane protein with a structural function interacting with chromatin and lamins, and an enzymatic function as a sterol reductase. Heterozygous LBR mutations cause nuclear hyposegmentation in neutrophils (Pelger anomaly), while homozygous mutations cause prenatal death with skeletal defects and abnormal sterol metabolism (Greenberg dysplasia). It has remained unclear whether the lethality in Greenberg dysplasia is due to cholesterol defects or altered nuclear morphology.To answer this question we characterized two LBR missense mutations and showed that they cause Greenberg dysplasia. Both mutations affect residues that are evolutionary conserved among sterol reductases. In contrast to wildtype LBR, both mutations failed to rescue C14 sterol reductase deficient yeast, indicating an enzymatic defect. We found no Pelger anomaly in the carrier parent excluding marked effects on nuclear structure. We studied Lbr in mouse embryos and demonstrate expression in skin and the developing skeletal system consistent with sites of histological changes in Greenberg dysplasia. Unexpectedly we found in disease-relevant cell types not only nuclear but also cytoplasmatic LBR localization. The cytoplasmatic LBR staining co-localized with ER-markers and is thus consistent with the sites of endogeneous sterol synthesis. We conclude that LBR missense mutations can abolish sterol reductase activity, causing lethal Greenberg dysplasia but not Pelger anomaly. The findings separate the metabolic from the structural function and indicate that the sterol reductase activity is essential for human intrauterine development.
authors.affiliation: UCL Institute of Child Health with Great Ormond Street Hospital for ChildrenNHS Trust, London, UK.
authors.forename: Peter
authors.initials: P
authors.lastname: Clayton
authors.forename: Björn
authors.initials: B
authors.lastname: Fischer
authors.forename: Anuska
authors.initials: A
authors.lastname: Mann
authors.forename: Sahar
authors.initials: S
authors.lastname: Mansour
authors.forename: Eva
authors.initials: E
authors.lastname: Rossier
authors.forename: Markus
authors.initials: M
authors.lastname: Veen
authors.forename: Christine
authors.initials: C
authors.lastname: Lang
authors.forename: Sevjidmaa
authors.initials: S
authors.lastname: Baasanjav
authors.forename: Moritz
authors.initials: M
authors.lastname: Kieslich
authors.forename: Katja
authors.initials: K
authors.lastname: Brossuleit
authors.forename: Sophia
authors.initials: S
authors.lastname: Gravemann
authors.forename: Nele
authors.initials: N
authors.lastname: Schnipper
authors.forename: Mohsen
authors.initials: M
authors.lastname: Karbasyian
authors.forename: Ilja
authors.initials: I
authors.lastname: Demuth
authors.forename: Monika
authors.initials: M
authors.lastname: Zwerger
authors.forename: Amparo
authors.initials: A
authors.lastname: Vaya
authors.forename: Gerd
authors.initials: G
authors.lastname: Utermann
authors.forename: Stefan
authors.initials: S
authors.lastname: Mundlos
authors.forename: Sigmar
authors.initials: S
authors.lastname: Stricker
authors.forename: Karl
authors.initials: K
authors.lastname: Sperling
authors.forename: Katrin
authors.initials: K
authors.lastname: Hoffmann
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D005347:Fibroblasts / Q000378:metabolism; D005838:Genotype; D006367:HeLa Cells; D006579:Heterozygote; D006720:Homozygote; D006801:Humans; D051379:Mice; D020125:Mutation, Missense; D009685:Nuclear Envelope / Q000378:metabolism; D010009:Osteochondrodysplasias / Q000235:genetics* / Q000473:pathology; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism; D010381:Pelger-Huet Anomaly / Q000235:genetics* / Q000473:pathology; D010641:Phenotype; D018160:Receptors, Cytoplasmic and Nuclear / Q000032:analysis / Q000235:genetics* / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism; D000097682:Lamin B Receptor
chemical_list: D010088:Oxidoreductases; D018160:Receptors, Cytoplasmic and Nuclear; D029701:Saccharomyces cerevisiae Proteins; D000097682:Lamin B Receptor; C022672:delta(14)-sterol reductase