Fuad Al Mutairi

Expanded Newborn Screening Program in Saudi Arabia: Incidence of screened disorders.

To address the implementation of the National Newborn Screening Program (NBS) in Saudi Arabia and stratify the incidence of the screened disorders.

The fragile site WWOX gene and the developing brain

WWOX was cloned as a tumor suppressor gene mapping to chromosomal fragile site FRA16D. Loss of WWOX is closely related to tumorigenesis, cancer progression, and therapy resistance. Recent studies demonstrate the growing role of WWOX gene in other human pathologies such as metabolic and nervous system-related conditions. The neurologic phenotype of WWOX mutation includes seizures, ataxia, developmental delay, and spasticity of variable severity. WWOX is a ubiquitous protein with high expression in many tissues including brain, cerebellum, brain stem, and spinal cord. WWOX is highly expressed in different brain regions during murine fetal development and remained unchanged in the cortex and the corpus callosum in adult mice. The mechanism or the putative role of WWOX in the nervous system is still unclear but may include abnormal signaling protein, disruption of neuronal pathways, neuronal differentiation, mitochondrial dysfunction, or apoptosis. Homozygous mutations affecting WWOX in humans are likely to be more described in the future using exome sequencing. The described findings highlight that WWOX plays a critical role in normal central nervous system development and disease. The aim of this review is to summarize the roles of WWOX in the developing brain.

A multicenter clinical exome study in unselected cohorts from a consanguineous population of Saudi Arabia demonstrated a high diagnostic yield

Abstract Purpose Whole-exome sequencing (WES) can help identify known and novel pathogenic molecular aberrations. Here, we examined the diagnostic yield of WES in population from consanguineous unions. Methods We preformed retrospective review of multicenter WES results of an unselected cohort of patients with a wide range of phenotypes. Clinical data and WES reports of 454 patients from 5 centers across Saudi Arabia were analyzed. Testing was performed in accredited commercial laboratories, and all the WES laboratory reports were reviewed again using additional clinical information available to the treating physicians. Results Among the 454 probands, we identified highly likely disease-causing variants in 222, thereby achieving a 49% molecular diagnostic yield. The diagnostic yield was 53% in consanguineous unions and 39% in non-consanguineous unions. About 66% of the identified variants in consanguineous families were homozygous, with an autosomal recessive mode of inheritance. Additional clinical data reclassified 11 positive reported results into 4 inconclusive and 7 negative results, and 22 inconclusive results into 17 positive and 5 negative results. Conclusions The diagnostic yield from WES in our unselected cohort is similar to other studies from the same region, which is a higher yield compared to other international regions largely because of the high rate of consanguinity and partly due to simplified variant interpretation and classification in consanguineous unions.

Further delineation of the phenotypic spectrum of ISCA2 defect: A report of ten new cases

Iron-Sulfur Cluster (ISC) biogenesis is a vital cellular process required to produce various ISC-containing proteins. These ISC proteins are responsible for essential functions such as glycine cleavage and the formation of lipoic acid, an essential cofactor of respiratory chain complexes. Defects in ISC biogenesis lead to multiple mitochondrial dysfunction syndromes including: ISCA2 with infantile onset leukodystrophy. Recently, a founder mutation, c.229G > A, p.Gly77Ser in ISCA2 was reported to cause Multiple Mitochondrial Dysfunction Syndrome type 4. In a retrospective review of children diagnosed with the ISCA2 defect, we were able to identify ten new patients who were not reported previously with the identical founder mutation. High CSF glycine levels and elevated glycine peaks on MR spectroscopy were demonstrated in all tested probands. All patients were between 3 and 7 months of age with a triad of neurodevelopmental regression, nystagmus and optic atrophy and leukodystrophy. MRI findings were typical in the patients with diffuse, abnormal white matter signal in the cerebrum, cerebellum, brain stem and spinal cord. The patients ended up in a vegetative state, and often premature death due to respiratory infections. We alert clinicians to consider the ISCA2 defect as a differential diagnosis of infantile onset leukodystrophies affecting the brain as well as the spinal cord, especially in the presence of elevated CSF glycine or elevated glycine peaks in MR spectroscopy.

The phenotypic and molecular spectrum of PEHO syndrome and PEHO-like disorders

1 Department of Molecular Neuroscience, Institute of Neurology, UCL Institute of Neurology, London WC1N 3BG, UK 2 Department of Molecular Medicine and Medical Biotechnologies “DMMBM”, University of Naples “Federico II”, Naples 80131, Italy 3 CEINGE Biotecnologie Avanzate, Naples 80131, Italy 4 European School of Molecular Medicine, SEMM, University of Milan, Italy 5 King Saud bin Abdulaziz University for Health Sciences, Department of Pediatrics, Division of Genetics, Riyadh 14611, Saudi Arabia 6 Genetics and Rare Diseases Research Division, Ospedale Pediatrico “Bambino Gesù”, Rome 00146, Italy

Mutation in SLC6A9 encoding a glycine transporter causes a novel form of non-ketotic hyperglycinemia in humans.

Glycine cleavage system (GCS) catalyzes the degradation of glycine and disruption of its components encoded by GLDC, AMT and GCSH are the only known causes of glycine encephalopathy, also known as non-ketotic hyperglycinemia (NKH). In this report, we describe a consanguineous family with one child who presented with NKH, but harbored no pathogenic variants in any of the three genes linked to this condition. Whole-exome sequencing revealed a novel homozygous missense variant in exon 9 of SLC6A9 NM_201649.3: c.1219 A>G (p.Ser407Gly) that segregates with the disease within the family. This variant replaces the highly conserved S407 in the ion-binding site of this glycine transporter and is predicted to disrupt its function. In murine model, knockout of Slc6a9 is associated with equivalent phenotype of NKH, namely respiratory distress and hypotonia. This is the first demonstration that mutation of the glycine transporter can be associated with NKH in humans.

Whole-genome sequencing offers additional but limited clinical utility compared with reanalysis of whole-exome sequencing

PurposeWhole-exome sequencing (WES) and whole-genome sequencing (WGS) are used to diagnose genetic and inherited disorders. However, few studies comparing the detection rates of WES and WGS in clinical settings have been performed.MethodsVariant call format files were generated and raw data analysis was performed in cases in which the final molecular results showed discrepancies. We classified the possible explanations for the discrepancies into three categories: the time interval between the two tests, the technical limitations of WES, and the impact of the sequencing system type.ResultsThis cohort comprised 108 patients with negative array comparative genomic hybridization and negative or inconclusive WES results before WGS was performed. Ten (9%) patients had positive WGS results. However, after reanalysis the WGS hit rate decreased to 7% (7 cases). In four cases the variants were identified by WES but missed for different reasons. Only 3 cases (3%) were positive by WGS but completely unidentified by WES.ConclusionIn this study, we showed that 30% of the positive cases identified by WGS could be identified by reanalyzing the WES raw data, and WGS achieved an only 7% higher detection rate. Therefore, until the cost of WGS approximates that of WES, reanalyzing WES raw data is recommended before performing WGS.

Congenital disorders of glycosylation: The Saudi experience

We retrospectively reviewed Saudi patients who had a congenital disorder of glycosylation (CDG). Twenty‐seven Saudi patients (14 males, 13 females) from 13 unrelated families were identified. Based on molecular studies, the 27 CDG patients were classified into different subtypes: ALG9‐CDG (8 patients, 29.5%), ALG3‐CDG (7 patients, 26%), COG6‐CDG (7 patients, 26%), MGAT2‐CDG (3 patients, 11%), SLC35A2‐CDG (1 patient), and PMM2‐CDG (1 patient). All the patients had homozygous gene mutations. The combined carrier frequency of CDG for the encountered founder mutations in the Saudi population is 11.5 per 10,000, which translates to a minimum disease burden of 14 patients per 1,000,000. Our study provides comprehensive epidemiologic information and prevalence figures for each of these CDG in a large cohort of congenital disorder of glycosylation patients.

Peeling skin syndrome associated with novel variant in FLG2 gene

Peeling skin syndrome is a rare genodermatosis characterized by variably pruritic superficial generalized peeling of the skin with several genes involved until now little is known about the association between FLG2 and peeling skin syndrome. We describe multiple family members from a consanguineous Saudi family with peeling skin syndrome. Next Generation Sequencing identifies a cosegregating novel variant in FLG2 c.632C>G (p.Ser211*) as a likely etiology in this family. Here, we reported on the clinical manifestation of homozygous loss of function variant in FLG2 as a disease‐causing gene for peeling skin syndrome and expand the dermatology findings.

Further Delineation of the Clinical Phenotype of Cerebellar Ataxia, Mental Retardation, and Disequilibrium Syndrome Type 4

Background: Cerebellar ataxia, mental retardation, and disequilibrium syndrome (CAMRQ) is a heterogeneous group of genetic disorders that have been grouped by shared clinical features; all of these features are transmitted via an autosomal recessive mechanism. Four variants of this syndrome have been identified so far, and each one differs in terms of both clinical and genotypical features. CAMRQ4 is a rare genetic disorder characterized by mental retardation, ataxia or an inability to walk, dysarthria and, in some patients, quadrupedal gait. Methods: We investigated three Saudi families with CAMRQ4. Blood samples were collected from the affected patients, their parents, and healthy siblings. DNA was extracted from whole blood, and whole-exome sequencing was performed. Findings were confirmed by segregation analysis, which was performed on other family members. Results: Thus far, 17 patients have been affected by CAMRQ4. Genetic analysis of all patients, including our current patients, showed a mutation in the aminophospholipid transporter, class I, type 8A, member 2 gene (ATP8A2). A series of common phenotypical features have been reported in these patients, with few exceptions. Ataxia, mental retardation, and hypotonia were present in all patients, consanguinity in 90% and abnormal movements in 50%. Moreover, 40% achieved ambulation at least once in their lifetime, 40% had microcephaly, whereas 30% were mute. Magnetic resonance imaging (MRI) of the brain was normal in 60% of patients. Conclusions: We described the largest cohort of patients with CAMRQ4 syndrome and identified three novel mutations. CAMRQ4 syndrome should be suspected in patients presenting with ataxia, intellectual disability, hypotonia, microcephaly, choreoathetoid movements, ophthalmoplegia, and global developmental delay, even if brain MRI appears normal.