ARGENTINEAN PROGRAM FOR THE DIAGNOSIS AND RESEARCH OF CONGENITAL DISORDER OF GLYCOSYLATION: An experience which is growing up.

BISTUÉ MILLÓN MB.1; DELGADO MA.1; STURIALE L.2; MATTHIJS G. 3; JAEKEN J.4; DODELSON DE KREMER R.1; ASTEGGIANO CG. 1,5,6

Villa Carlos Paz

Simposio; “Congenital Disorders of Glycosylation (CDG) 1st Latin American Symposium”; 2010

CDG Latin American Network / CEMECO, UNC, Argentina

ARGENTINEAN PROGRAM FOR THE DIAGNOSIS AND RESEARCH OF CONGENITAL DISORDER OF GLYCOSYLATION: An experience which is growing up. Bistué Millón MB.1; Delgado MA.1; Sturiale L.2; Matthijs G. 3; Jaeken J.4; Dodelson de Kremer R.1; Asteggiano CG. 1,5,6. (1) CEMECO (Centro de Estudio de las Metabolopatías Congénitas), Facultad de Ciencias Médicas, Universidad Nacional de Córdoba, Hospital de Niños S.T., Córdoba, Argentina; (2)CNR Institute per la Chimica e la Tecnologia dei Polimeri, Catania, Italy; (3) Department for Human Genetics, Katholieke Universiteit Leuven, Belgium; (4) Center for Metabolic Diseases,Katholieke Universiteit Leuven, Belgium; (5) Cátedra Química Biológica, Facultad de Medicina, Universidad Católica de Córdoba, Argentina; (6) Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina. E-mail: asteggianocarla@hotmail.com “Congenital Disorders of Glycosylation” (CDG) are a growing group of hereditary diseases caused by abnormal protein glycosylation, which follows a sequential pathway in the cytoplasm, ER, and Golgi apparatus. The clinical phenotypic spectrum of the glycosylation defects is highly variable, ranging from severe multisystem disorders to alteration of specific organs or tissues such us Multiple Hereditary Exostoses (MHE). Protein glycosylation disorders, involving N-glycosylation and combined N- and O-glycosylation defects, were previously divided into CDG type I or II, according to the intracellular localization of the molecular defect. The new nomenclature indicates the specific disorder under the name of the gene or the protein involved, which allows the inclusion of all protein glycosylation disorders, N- and O-glycosylation defects, and expanded to the lipid glycosylation defects. However, there is still a large group of unsolved cases of patients with altered glycosylation patterns that are classified as CDG-x. Aim: To communicate the detection and diagnosis of CDG and an important number of MHE affected patients as a reference center in Argentina. Methodology: A) Analysis of serum N-glycoproteins using different assays: 1) Western blot (Wb), isoelectric focusing (IEF) and High Performance Liquid Chromatography (HPLC) of serum transferrin (Tf). 2) Enzymatic analysis of phosphomannomutase and phosphomannose isomerase activities in leucocytes. B) Lipid-linked oligosaccharide (LLO) analysis in fibroblasts. C) Transferin MALDI-TOF Mass Spectrometry (MS) and D) Molecular analysis in different genes affecting N- or O-glycosylation. Results: N-glycosylation defects were investigated by a complex algorithm to detect altered glycosylation profiles. All the samples were obtained after the written consents of the patients. Complementary studies (LLO, MS) were done in collaboration with Euroglycanet group. We found several patients CDG-x that showed transferrin patterns type I (n = 2) and type II (n = 3). Their characterizations are in progress to identify the basic defect in these patients. As regards O-glycosylation defects, we have studied 25 MHE patients, ages ranging from 2 to 50 years old. PCR and direct sequencing of EXT1 and EXT2 genes were 30 performed. Clinical and radiological assessments, allow us to detect 70% of the patients that presented a severe phenotype ranging from IS to IVS and 30% with a mild phenotype. A total of 10 exonic changes were identified, of which 20% were previously described mutations in EXT1 and 80% novel mutations (60% in EXT1 and 20% in EXT2). One of the novel mutations was found in a patient with a malignant transformation of osteochondroma to chondrosarcoma. Discussion: The extremely wide clinical spectrum of CDG makes a broad screening for these disorders in children as well as in adults. The diagnosis of CDG should be considered in each patient with hypotonia, dysmorphic features and developmental delay with frequent cataract. MHE seems to have a high frequency in Argentinean population and this interdisciplinary study represents the first genotype-phenotype investigation in our country. Likewise, this first Argentinean CDG Program allowed us to start a new genetic and metabolic chapter in our country. We hope to work in a future Latin American CDG Network that would make possible the diagnosis and possibility the research of human glycosylation disorders.