Molecular and functional analysis ofSUMF1 mutations in multiple sulfatase deficiency

Abstract

Multiple sulfatase deficiency (MSD) is a rare disorder characterized by impaired activity of all known sulfatases. The gene mutated in this disease is SUMF1, which encodes a protein involved in a post-translational modification at the catalytic site of all sulfatases that is necessary for their function. SUMF1 strongly enhances the activity of sulfatases when coexpressed with sulfatase in Cos-7 cells. We performed a mutational analysis of SUMF1 in 20 MSD patients of different ethnic origin. The clinical presentation of these patients was variable, ranging from severe neonatal forms to mild phenotypes showing mild neurological involvement. A total of 22 SUMF1 mutations were identified, including missense, nonsense, microdeletion, and splicing mutations. We expressed all missense mutations in culture to study their ability to enhance the activity of sulfatases. Of the predicted amino acid changes, 11 (p.R349W, p.R224W, p.L20F, p.A348P, p.S155P, p.C218Y, p.N259I, p.A279V, p.R349Q, p.C336R, p.A177P) resulted in severely impaired sulfatase-enhancing activity. Two (p.R345C and p.P266L) showed a high residual activity on some, but not all, of the nine sulfatases tested, suggesting that some SUMF1 mutations may have variable effects on the activity of each sulfatase. This study compares, for the first time, clinical, biochemical, and molecular data in MSD patients. Our results show lack of a direct correlation between the type of molecular defect and the severity of phenotype.

A non-conserved miRNA regulates lysosomal function and impacts on a human lysosomal storage disorder

“…Analysis of the SUMF1 mutations in MSD revealed multiple types including missense, nonsense, deletions and splice mutations 32 . The effect of these mutations on enzyme activity is variable as is the clinical picture in MSD patients; however, a lack of genotype-phenotype correlation indicates the existence of additional causative factors, either genetic or non-genetic, which could contribute to disease pathogenesis 32 .…”

“…The effect of these mutations on enzyme activity is variable as is the clinical picture in MSD patients; however, a lack of genotype-phenotype correlation indicates the existence of additional causative factors, either genetic or non-genetic, which could contribute to disease pathogenesis 32 . This leads to the speculation that miR-95, via its regulation of SUMF1, and perhaps also additional targets related to lysosomal function, could contribute to the pathogenesis MSD or other LSDs.…”

“…The importance of lysosomal sulfatases in human metabolism is underlined by the study of inherited diseases resulting from defects in sulfatase function 31 . Since SUMF1 is an essential activator of all cellular sulfatases, mutations in this gene cause the most severe disease variant, MSD, in which all sulfatase activity is severely reduced 12,32 . To assess the physiological importance of miR-95 in relation to MSD, we stably knocked down endogenous miR-95 in two lymphoblast and four fibroblast lines derived from six MSD patients harbouring different mutations in the SUMF1 gene (see Methods).…”

SUMF1 mutations affecting stability and activity of formylglycine generating enzyme predict clinical outcome in multiple sulfatase deficiency

“…25 Until now, more than 30 different SUMF1 mutations were found, most of which are missense mutations. 9,23,26,20,27 In a first approach, we investigated the consequences of four different MSD causing SUMF1 mutations on FGE 13 expression, localization, stability and activity in either an overexpressing cell-culture model or in patient fibroblasts. We found that all four variant FGE proteins could be expressed in HT-1080 cells, correctly localizing to the ER.…”

Molecular analysis ofSUMF1 mutations: stability and residual activity of mutant formylglycine-generating enzyme determine disease severity in multiple sulfatase deficiency

“…So far, 30 mutations in SUMF1 have been described in MSD patients including nine nonsense and 21 missense mutations [Dierks et al, 2003;Cosma et al, 2003;Cosma et al, 2004;Dierks et al, 2005;Diaz-Font et al, 2005]. Mature FGE is made up of a 341-amino acid polypeptide, which adopts a single domain monomeric structure with a unique fold .…”