A compound heterozygous mutation in DPAGT1 results in a congenital disorder of glycosylation with a relatively mild phenotype.

European journal of human genetics : EJHG

PubMedID: 23249953

Iqbal Z, Shahzad M, Vissers LE, van Scherpenzeel M, Gilissen C, Razzaq A, Zahoor MY, Khan SN, Kleefstra T, Veltman JA, de Brouwer AP, Lefeber DJ, van Bokhoven H, Riazuddin S. A compound heterozygous mutation in DPAGT1 results in a congenital disorder of glycosylation with a relatively mild phenotype. Eur J Hum Genet. 2013;21(8):844-9.
Congenital disorders of glycosylation (CDG) are a large group of recessive multisystem disorders caused by impaired protein or lipid glycosylation. The CDG-I subgroup is characterized by protein N-glycosylation defects originating in the endoplasmic reticulum. The genetic defect is known for 17 different CDG-I subtypes. Patients in the few reported DPAGT1-CDG families exhibit severe intellectual disability (ID), epilepsy, microcephaly, severe hypotonia, facial dysmorphism and structural brain anomalies. In this study, we report a non-consanguineous family with two affected adults presenting with a relatively mild phenotype consisting of moderate ID, epilepsy, hypotonia, aggressive behavior and balance problems. Exome sequencing revealed a compound heterozygous missense mutation, c.85A>T (p.I29F) and c.503T>C (p.L168P), in the DPAGT1 gene. The affected amino acids are located in the first and fifth transmembrane domains of the protein. Isoelectric focusing and high-resolution mass spectrometry analyses of serum transferrin revealed glycosylation profiles that are consistent with a CDG-I defect. Our results show that the clinical spectrum of DPAGT1-CDG is much broader than appreciated so far.