Prenatal Diagnosis of Mucopolysaccharidosis I by LC-MS/MS Determination of Disease-specific Oligosaccharides in Amniotic Fluid

Larissa Faqueti ^1,2 Gabrielle Dineck Iop ^1,2 Layzon A. Lemos Silva ^1,2 Henrique B.L. Borges ^1,2 Kristiane Michelin-Tirelli ³ Fernanda Medeiros ³ Sandra Leistner-Segal ³ Rejane Gus ³ Carolina F. M. Souza ³ Maria Teresa V. Sanseverino ³ Jose Antonio Magalhaes ⁴ Franciele B. Trapp ^2,3 Roberto Giugliani ^1,2,3,5,6

¹BioDiscovery Laboratory, Hospital de Clinicas de Porto Alegre, Brazil
²Casa Dos Raros, Brazil
³Medical Genetics Service, Hospital de Clinicas de Porto Alegre, Brazil
⁴Fetal Medicine Unit, Hospital de Clinicas de Porto Alegre, Brazil
⁵Department of Genetics, Federal University of Rio Grande do Sul, Brazil
⁶Dasa Genomics, Brazil

Background: Mucopolysaccharidosis (MPS) is a severe and progressive disease related to the storage of glycosaminoglycans (GAGs). A very challenging aspect associated with this context is the time of diagnosis, since better outcomes are observed in patients who start treatment early before the development of irreversible damage, with protocols for prenatal therapy in clinical development. The development of new analytical tools is helping to improve the diagnostic processes in the prenatal stage. Herein, we report a prenatal diagnosis of MPS I in a conceptus at 24 weeks of gestation with a positive family history. Although the prenatal diagnosis of MPS is usually performed by enzyme quantification and/or molecular analysis in amniocytes, we report an alternative approach based on the analysis of MPS I-specific oligosaccharides derived from GAGs by UPLC-MS/MS in the supernatant of amniotic fluid (AF). Additionally, confirmatory measurement of IDUA activity and molecular analysis of the IDUA gene were performed from the cultured amniocytes.

Results: Increased levels of specific-MPS I oligosaccharide HNAc-UA (0.402 apparent pmol/nmol of creatinine; reference: 0.025 apparent pmol/nmol of creatinine) were found in the AF supernatant. There were also increased dermatan and heparan sulphate levels. These findings were supported by the deficiency of IDUA activity (0.35 nmol/h/mg of protein; reference: 92-264 nmol/h/mg of protein) in the foetal cells, as well as the presence of pathogenic variants (c.1205G>A[p.Trp402Ter] and c.623G>A[p.Gly208Asp]) in compound heterozygosity in the IDUA gene.

Conclusions: Disease-specific oligosaccharides can be quantified in the supernatant of AF of MPS I foetuses, potentially providing a faster and more accurate approach to the detection of this condition. Further analysis are being developed to highlight the potential of MS/MS for the identification of additional MPS subtypes in the amniotic fluid supernatant.

Acknowledgement: CNPq, BioMarin