Banan Al-Younes

Association of a Mutation in LACC1 With a Monogenic Form of Systemic Juvenile Idiopathic Arthritis

The pathologic basis of systemic juvenile idiopathic arthritis (JIA) is a subject of some controversy, with evidence for both autoimmune and autoinflammatory etiologies. Several monogenic autoinflammatory disorders have been described, but thus far, systemic JIA has only been attributed to a mutation of MEFV in rare cases and has been weakly associated with the HLA class II locus. This study was undertaken to identify the cause of an autosomal‐recessive form of systemic JIA.

Phenotypical spectrum of cerebellar ataxia associated with a novel mutation in the CA8 gene, encoding carbonic anhydrase (CA) VIII†‡

We define the neurological characteristics of familial cases from multiple branches of a large consanguineous family with cerebellar ataxia, mental retardation (MR), and dysequilibrium syndrome type 3 caused by a mutation in the recently cloned CA8 gene. The linkage analysis revealed a high logarithm of the odds (LOD) score region on 8q that harbors the CA8 in which a novel homozygous c.484G>A (p.G162R) mutation was identified in all seven affected members. The patients had variable cerebellar ataxia and mild cognitive impairment without quadrupedal gait. The brain MRI showed variable cerebellar volume loss and ill‐defined peritrigonal white matter abnormalities. The Fluorodeoxyglucose Positron Emission Tomography (FDG PET) revealed hypometabolic cerebellar hemispheres, temporal lobes, and mesial cortex. This report expands the neurological and radiological phenotype associated with CA8 mutations. CA8 involvement should be considered in the differential diagnosis of other genetically unresolved autosomal recessive cerebellar ataxias.

Expanding the clinical, allelic, and locus heterogeneity of retinal dystrophies

Purpose:Retinal dystrophies (RD) are heterogeneous hereditary disorders of the retina that are usually progressive in nature. The aim of this study was to clinically and molecularly characterize a large cohort of RD patients.Methods:We have developed a next-generation sequencing assay that allows known RD genes to be sequenced simultaneously. We also performed mapping studies and exome sequencing on familial and on syndromic RD patients who tested negative on the panel.Results:Our panel identified the likely causal mutation in >60% of the 292 RD families tested. Mapping studies on all 162 familial RD patients who tested negative on the panel identified two novel disease loci on Chr2:25,550,180-28,794,007 and Chr16:59,225,000-72,511,000. Whole-exome sequencing revealed the likely candidate as AGBL5 and CDH16, respectively. We also performed exome sequencing on negative syndromic RD cases and identified a novel homozygous truncating mutation in GNS in a family with the novel combination of mucopolysaccharidosis and RD. Moreover, we identified a homozygous truncating mutation in DNAJC17 in a family with an apparently novel syndrome of retinitis pigmentosa and hypogammaglobulinemia.Conclusion:Our study expands the clinical and allelic spectrum of known RD genes, and reveals AGBL5, CDH16, and DNAJC17 as novel disease candidates.Genet Med 18 6, 554–562.

A Novel X-linked Disorder with Developmental Delay and Autistic Features

Genomic duplications that lead to autism and other human diseases are interesting pathological lesions since the underlying mechanism almost certainly involves dosage sensitive genes. We aim to understand a novel genomic disorder with profound phenotypic consequences, most notably global developmental delay, autism, psychosis, and anorexia nervosa.

Clinical and biochemical features associated with BCS1L mutation

Our study describes a novel phenotype in a series of nine Saudi patients with lactic acidosis, from four consanguineous families three of which are related. Detailed genetic studies including linkage, homozygosity mapping and targeted sequencing identified a causative mutation in the BCS1L gene. All affected members of the families have an identical mutation in this gene, mutations of which are recognized causes of Björnstad syndrome, GRACILE syndrome and a syndrome of neonatal tubulopathy, encephalopathy, and liver failure (MIM 606104) leading to isolated mitochondrial respiratory chain complex III deficiency. Here we report the appearance of a novel behavioral (five patients) and psychiatric (two patients) phenotype associated with a p.Gly129Arg BCS1L mutation, differing from the phenotype in a previously reported singleton patient with this mutation. The psychiatric symptoms emanated after childhood, initially as hypomania later evolving into intermittent psychosis. Neuroradiological findings included subtle white matter abnormalities, whilst muscle histopathology and respiratory chain studies confirmed respiratory chain dysfunction. The variable neuro-psychiatric manifestations and cortical visual dysfunction are most unusual and not reported associated with other BCS1L mutations. This report emphasizes the clinical heterogeneity associated with the mutation in BCS1L gene, even within the same family and we recommend that defects in this gene should be considered in the differential diagnosis of lactic acidosis with variable involvement of different organs.

METTL23, a transcriptional partner of GABPA, is essential for human cognition

Whereas many genes associated with intellectual disability (ID) encode synaptic proteins, transcriptional defects leading to ID are less well understood. We studied a large, consanguineous pedigree of Arab origin with seven members affected with ID and mild dysmorphic features. Homozygosity mapping and linkage analysis identified a candidate region on chromosome 17 with a maximum multipoint logarithm of odds score of 6.01. Targeted high-throughput sequencing of the exons in the candidate region identified a homozygous 4-bp deletion (c.169_172delCACT) in the METTL23 (methyltransferase like 23) gene, which is predicted to result in a frameshift and premature truncation (p.His57Valfs*11). Overexpressed METTL23 protein localized to both nucleus and cytoplasm, and physically interacted with GABPA (GA-binding protein transcription factor, alpha subunit). GABP, of which GABPA is a component, is known to regulate the expression of genes such as THPO (thrombopoietin) and ATP5B (ATP synthase, H+ transporting, mitochondrial F1 complex, beta polypeptide) and is implicated in a wide variety of important cellular functions. Overexpression of METTL23 resulted in increased transcriptional activity at the THPO promoter, whereas knockdown of METTL23 with siRNA resulted in decreased expression of ATP5B, thus revealing the importance of METTL23 as a regulator of GABPA function. The METTL23 mutation highlights a new transcriptional pathway underlying human intellectual function.

Clinical and pathological heterogeneity of a congenital disorder of glycosylation manifesting as a myasthenic/myopathic syndrome.

Congenital disorders of glycosylation are often associated with muscle weakness in apparent isolation or as part of a multi-systemic disorder. We report here the clinical and pathological features resulting from a homozygous mutation of ALG2 in an extended family. Phenotypic heterogeneity is observed among the small cohort of patients reported to date and is highlighted by our study. Linkage analysis, homozygozity mapping and whole exome sequencing followed clinical and pathological characterization of patients who presented with a congenital limb girdle pattern of weakness with no ocular or bulbar involvement. Nerve stimulation studies were consistent with a congenital myasthenic syndrome. Severity and progression of disease was variable. Muscle biopsies showed myopathic features, ragged red fibers and a sub-sarcolemmal accumulation of structurally normal mitochondria. Whole exome sequencing revealed an indel mutation c.214_224delGGGGACTGGCTdelinsAGTCCCCG, p.72_75delGDWLinsSPR in exon 1 of ALG2. Mutation of ALG2 manifested as a limb girdle pattern of muscle weakness with defects at both the neuromuscular junction and sarcomere. In addition the accumulation and distribution of mitochondria in the diseased muscle and the presence of ragged red fibers were supportive of a mitochondrial myopathy. ALG2 mutation results in a heterogeneous phenotype and care should be taken in categorization and treatment of these patients.

Expanding phenotypic and allelic heterogeneity of tricho-hepato-enteric syndrome.

ABSTRACT Molecular genetics studies are of increasing importance in the diagnosis and classification of congenital diarrheal disorders. We describe the molecular genetic basis of tricho-hepato-enteric syndrome in patients from Saudi Arabia with novel mutations of SKIV2L (c.3559_3579del, p.1187_1193del) and TTC37 (C4102T, p.Q1368X). Interestingly, the congenital presence of café-au-lait spots and their distribution in the pelvis and lower limbs were a unique and consistent clinical feature of these patients and may aid differential diagnosis of congenital diarrheal disorders. This study expands allelic and phenotypic heterogeneity of syndromic diarrhea/tricho-hepato-enteric syndrome.

A novel interstitial microdeletion of 7q22.1-7q22.3 detected by array comparative genomic hybridization.

A Novel Interstitial Microdeletion of 7q22.1-7q22.3 Detected by Array Comparative Genomic Hybridization Zuhair N. Al-Hassnan, AlBandary Al-Bakheet, Nada Abu-Dheim, Banan Al-Younes, Dilek Colak, and Namik Kaya* Department of Medical Genetics, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia College of Medicine, Alfaisal University, Riyadh, Saudi Arabia Department of Genetics, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia Department of Biostatistics and Scientific Computing, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia

Novel V97G ASAH1 mutation found in Farber disease patients: Unique appearance of the disease with an intermediate severity, and marked early involvement of central and peripheral nervous system

Farber disease is a rare inherited lysosomal storage disorder caused by ceramidase deficiency that leads to accumulation of ceramide in various tissues. Mutations within ASAH1 encoding for acid ceramidase are responsible for the disease. Here we report two siblings with Farber disease who carry a novel V97G with the parents and a sister being asymptomatic carriers. The mutation site was found to be highly conserved among different species using ClustalW2 alignment. Functional prediction tools indicated the mutation to be pathogenic. Electron microscopy based ultrastructural studies using skin biopsy showed inclusion of enlarged lysosomes and presence of the zebra bodies. The T1 weighted magnetic resonance images of the brain indicated diffuse loss of the deep white matter volume predominantly along the occipital horns of the lateral ventricle with subsequent facet dilatation of the supratentorial and infratentorial ventricular system. This is the first report of a detailed clinical and molecular analysis of cases with Farber disease from Saudi Arabia.