Single-center experience of N-linked Congenital Disorders of Glycosylation with a Summary of Molecularly Characterized Cases in Arabs.

Congenital disorders of glycosylation (CDG) represent an expanding group of conditions that result from defects in protein and lipid glycosylation. Different subgroups of CDG display considerable clinical and genetic heterogeneity due to the highly complex nature of cellular glycosylation. This is further complicated by ethno-geographic differences in the mutational landscape of each of these subgroups. Ten Arab CDG patients from Latifa Hospital in Dubai, United Arab Emirates, were assessed using biochemical (glycosylation status of transferrin) and molecular approaches (next-generation sequencing [NGS] and Sanger sequencing). In silico tools including CADD and PolyPhen-2 were used to predict the functional consequences of uncovered mutations. In our sample of patients, five novel mutations were uncovered in the genes: MPDU1, PMM2, MAN1B1, and RFT1. In total, 9 mutations were harbored by the 10 patients in 7 genes. These are missense and nonsense mutations with deleterious functional consequences. This article integrates a single-center experience within a list of reported CDG mutations in the Arab world, accompanied by full molecular and clinical details pertaining to the studied cases. It also sheds light on potential ethnic differences that were not noted before in regards to CDG in the Arab world.

Novel PDE6A mutation in an Emirati patient with retinitis pigmentosa.

Mutations in the PDE6A gene are known to cause a form of retinitis pigmentosa (RP43), characterized by progressive retinal degeneration. We describe an Emirati patient with RP caused by a novel mutation in PDE6A. Clinical diagnosis of RP was made based on clinical evaluation and electroretinograms. The molecular analysis involved performing whole-exome sequencing, which enabled the identification of a homozygous 2-bp deletion (c.1358_1359delAT) in PDE6A, which was predicted to result in a frameshift and premature termination (p.Ile452Serfs*7). The mutation completely removed the catalytic PDEase domain in the protein. The parents were found to be heterozygous carriers of the variant. We thus report the first known case of a pathological variant in the PDE6A gene from the Arabian Peninsula.

Identification of a novel CTCF mutation responsible for syndromic intellectual disability - a case report.

BACKGROUND: Autosomal dominant mental retardation 21 (MRD21) is a very rare condition, characterized by short stature, microcephaly, mild facial dysmorphisms and intellectual disability that ranged from mild to severe. MRD21 is caused by mutations in CCCTC-binding factor (CTCF) and this was established through only four unrelated cases, two of which had frameshift mutations. CTCF is a master transcriptional regulator that controls chromatin structure and may serve as insulator and transcriptional activator and repressor. CASE PRESENTATION: This study presents, clinically and molecularly, an Emirati patient with de novo frameshift mutation in CTCF. This novel mutation was uncovered using whole exome sequencing and was confirmed by Sanger sequencing in the trio. In silico analysis, using SIFT Indel, indicates that this frameshift; p.Lys206Profs*13 is functionally damaging with the likely involvement of nonsense-mediated mRNA decay. CONCLUSIONS: Upon comparing the clinical picture of the herewith-reported individual with previously reported cases of MRD21, there seems to be many common symptoms, and few new ones that were not observed before. This helps to further define this rare condition and its molecular underpinnings.

Novel ECHS1 mutation in an Emirati neonate with severe metabolic acidosis.

ECHS1 is a mitochondrial matrix enzyme that catalyzes an important step in the ß-oxidation spiral of fatty acid catabolism, and individuals with mutations in the ECHS1 gene suffer from an autosomal recessive condition typified by delayed psychomotor development, mitochondrial encephalopathy, hypotonia, and cardiomyopathy. Here we report the first Arab case of ECHS1 Deficiency. The patient was born to consanguineous parents with all growth parameters being low for gestational age, and was persistently desaturated. Cord blood gas and later blood analysis showed severe metabolic acidosis. Tandem MS revealed increased levels of valine, and Leucine/Isoleucine and decreased level of Glutamine. There was also a large patent ductus arteriosus with right to left shunt and a possible small muscular ventricular septal defect. Whole Exome Sequencing revealed a novel homozygous missense mutation in the ECHS1 gene; c.842 A > G (p.Glu281Gly). In-silico analysis suggests that the residue affected by this mutation may be involved in an important functional or structural role.