title: Funtional characterization of four novel MAN2B1 mutations causing juvenile onset alpha-mannosidosis.
abstract: Alpha-mannosidosis is a recessively inherited disorder due to the deficiency of the lysosomal alpha-mannosidase. We report the molecular analysis performed in two patients with the late onset form of alpha-mannosidosis. Four new alleles were identified: three missense mutations involving highly conserved residues, c.597 C>A (p.H200N), c.1553 T>C (p.L518P) and c.2746 C>A (p.R916S) and a single nucleotide deletion, c.2660delC. In vitro expression studies in COS-1 cells demonstrated that pH200N, p.L518P and p.R916S proteins are expressed but retained no residual enzyme activity. These data are supported by structural 3D analysis which predicted that both p.L518P and p.R916S could affect the interaction of the small E-domain with the active site domain or the main body of the structure while the pH200N might alter substrate binding or other catalytic properties. Finally, the c.2660delC causes a frameshift introducing a premature stop codon (p.T887SfsX45), presuming to be a severe mutation.
authors.affiliation: Unità Malattie Metaboliche, IRCCS Burlo Garofolo, Trieste, Italy.
authors.forename: M G
authors.initials: MG
authors.lastname: Pittis
authors.forename: A L E
authors.initials: AL
authors.lastname: Montalvo
authors.forename: P
authors.initials: P
authors.lastname: Heikinheimo
authors.forename: M
authors.initials: M
authors.lastname: Sbaragli
authors.forename: C
authors.initials: C
authors.lastname: Balducci
authors.forename: E
authors.initials: E
authors.lastname: Persichetti
authors.forename: L
authors.initials: L
authors.lastname: Van Maldergem
authors.forename: M
authors.initials: M
authors.lastname: Filocamo
authors.forename: B
authors.initials: B
authors.lastname: Bembi
authors.forename: T
authors.initials: T
authors.lastname: Beccari
mesh_terms: D000328:Adult; D000818:Animals; D019556:COS Cells; D002648:Child; D002522:Chlorocebus aethiops; D005260:Female; D005838:Genotype; D006801:Humans; D008297:Male; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D011487:Protein Conformation; D043323:alpha-Mannosidase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D008363:alpha-Mannosidosis / Q000201:enzymology / Q000235:genetics*
chemical_list: D043323:alpha-Mannosidase