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

ABSTRACT: 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.

SUBMITTER: Iqbal Z

PROVIDER: S-EPMC3722673 | biostudies-literature | 2013 Aug

REPOSITORIES: biostudies-literature

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

Iqbal Zafar Z Iqbal Zafar Z Shahzad Mohsin M Vissers Lisenka E L M LE van Scherpenzeel Monique M Gilissen Christian C Razzaq Attia A Zahoor Muhammad Yasir MY Khan Shaheen N SN Kleefstra Tjitske T Veltman Joris A JA de Brouwer Arjan P M AP Lefeber Dirk J DJ van Bokhoven Hans H Riazuddin Sheikh S

European journal of human genetics : EJHG 20121219 8

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 an ...[more]

PMID: 23249953

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Project description:Bruck syndrome (BRKS) is the rare disorder that features congenital joint contractures often with pterygia and subsequent fractures, also known as osteogenesis imperfecta (OI) type XI (OMIM # 610968). Its two forms, BRKS1 (OMIM # 259450) and BRKS2 (OMIM # 609220), reflect autosomal recessive (AR) inheritance of FKBP10 and PLOD2 loss-of-function mutations, respectively. A 10-year-old girl was referred with blue sclera, osteopenia, poorly-healing fragility fractures, Wormian skull bones, cleft soft palate, congenital fusion of cervical vertebrae, progressive scoliosis, bell-shaped thorax, restrictive and reactive pulmonary disease, protrusio acetabuli, short stature, and additional dysmorphic features without joint contractures. Iliac crest biopsy after alendronate treatment that improved her bone density revealed low trabecular connectivity, abundant patchy osteoid, and active bone formation with widely-spaced tetracycline labels. Chromosome 22q11 deletion analysis for velocardiofacial syndrome, COL1A1 and COL1A2 sequencing for prevalent types of OI, and Sanger sequencing of LRP5, PPIB, FKBP10, and IFITM5 for rare pediatric osteoporoses were negative. Copy number microarray excluded a contiguous gene syndrome. Instead, exome sequencing revealed two missense variants in PLOD2 which encodes procollagen-lysine, 2-oxoglutarate 5-dioxygenase 2 (lysyl hydroxylase 2, LH2); exon 8, c.797G>T, p.Gly266Val (paternal), and exon 12, c.1280A>G, p.Asn427Ser (maternal). In the Exome Aggregation Consortium (ExAC) database, low frequency (Gly266Val, 0.0000419) and absence (Asn427Ser) implicated both variants as mutations of PLOD2. The father, mother, and sister (who carried the exon 12 defect) were reportedly well with normal parental DXA findings. BRKS2, characterized by under-hydroxylation of type I collagen telopeptides compromising their crosslinking, has been reported in at least 16 probands/families. Most PLOD2 mutations involve exons 17-19 (of 20 total) encoding the C-terminal domain with LH activity. However, truncating defects (nonsense, frameshift, splice site mutations) are also found throughout PLOD2. In three reports, AR PLOD2 mutations are not associated with congenital contractures. Our patient's missense defects lie within the central domain of unknown function of PLOD2. In our patient, compound heterozygosity with PLOD2 mutations is associated with a clinical phenotype distinctive from classic BRKS2 indicating that when COL1A1 and COL1A2 mutation testing is negative for OI without congenital contractures or pterygia, atypical BRKS should be considered.

Dataset Information

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

Publications

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

Similar Datasets

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