Almundher Al-Maawali

Mutations in PYCR2, Encoding Pyrroline-5-Carboxylate Reductase 2, Cause Microcephaly and Hypomyelination

Despite recent advances in understanding the genetic bases of microcephaly, a large number of cases of microcephaly remain unexplained, suggesting that many microcephaly syndromes and associated genes have yet to be identified. Here, we report mutations in PYCR2, which encodes an enzyme in the proline biosynthesis pathway, as the cause of a unique syndrome characterized by postnatal microcephaly, hypomyelination, and reduced cerebral white-matter volume. Linkage mapping and whole-exome sequencing identified homozygous mutations (c.355C>T [p.Arg119Cys] and c.751C>T [p.Arg251Cys]) in PYCR2 in the affected individuals of two consanguineous families. A lymphoblastoid cell line from one affected individual showed a strong reduction in the amount of PYCR2. When mutant cDNAs were transfected into HEK293FT cells, both variant proteins retained normal mitochondrial localization but had lower amounts than the wild-type protein, suggesting that the variant proteins were less stable. A PYCR2-deficient HEK293FT cell line generated by genome editing with the clustered regularly interspaced short palindromic repeat (CRISPR)-Cas9 system showed that PYCR2 loss of function led to decreased mitochondrial membrane potential and increased susceptibility to apoptosis under oxidative stress. Morpholino-based knockdown of a zebrafish PYCR2 ortholog, pycr1b, recapitulated the human microcephaly phenotype, which was rescued by wild-type human PYCR2 mRNA, but not by mutant mRNAs, further supporting the pathogenicity of the identified variants. Hypomyelination and the absence of lax, wrinkly skin distinguishes this condition from that caused by previously reported mutations in the gene encoding PYCR2s isozyme, PYCR1, suggesting a unique and indispensable role for PYCR2 in the human CNS during development.

Prenatal growth restriction, retinal dystrophy, diabetes insipidus and white matter disease: expanding the spectrum of PRPS1-related disorders

PRPS1 codes for the enzyme phosphoribosyl pyrophosphate synthetase-1 (PRS-1). The spectrum of PRPS1-related disorders associated with reduced activity includes Arts syndrome, Charcot–Marie–Tooth disease-5 (CMTX5) and X-linked non-syndromic sensorineural deafness (DFN2). We describe a novel phenotype associated with decreased PRS-1 function in two affected male siblings. Using whole exome and Sanger sequencing techniques, we identified a novel missense mutation in PRPS1. The clinical phenotype in our patients is characterized by high prenatal maternal α-fetoprotein, intrauterine growth restriction, dysmorphic facial features, severe intellectual disability and spastic quadraparesis. Additional phenotypic features include macular coloboma-like lesions with retinal dystrophy, severe short stature and diabetes insipidus. Exome sequencing of the two affected male siblings identified a shared putative pathogenic mutation c.586C>T p.(Arg196Trp) in the PRPS1 gene that was maternally inherited. Follow-up testing showed normal levels of hypoxanthine in urine samples and uric acid levels in blood serum. The PRS activity was significantly reduced in erythrocytes of the two patients. Nucleotide analysis in erythrocytes revealed abnormally low guanosine triphosphate and guanosine diphosphate. This presentation is the most severe form of PRPS1-deficiency syndrome described to date and expands the spectrum of PRPS1-related disorders.

Spectrum of paediatric lysosomal storage disorders in oman.

OBJECTIVES The aim of this study was to look at the spectrum of paediatric lysosomal disorders in Oman. Lysosomal storage disorders (LSDs) are a heterogeneous group of inherited metabolic diseases. Few studies on the birth prevalence and prevalence of LSDs have been reported from the Arabian Peninsula. METHODS We studied 86 children with LSDs diagnosed over a period of nine years, from June 1998 to May 2007. Detailed clinical data, including age of onset, sex, age and mode of first presentation, and presence of consanguinity were collected. RESULTS Our data showed the combined birth prevalence for all LSDs in Oman to be around 1 in 4,700 live births. Sphingolipidoses was the most common group of disorder encountered (47.7%), followed by neuronal ceroid lipofuscinoses (NCL) (23.2%) and mucopolysaccharidoses (MPS) (23.2%). The proportion of consanguineous marriages in our series was found to be 87.5%. CONCLUSION Our data represent the birth prevalence and clinical spectrum of such disorders in Oman, one of the highly consanguineous societies in the Middle East.

Hereditary spastic paraplegia associated with axonal neuropathy: a novel mutation of SPG3A in a large family.

Spastic paraplegia Type 3A is an autosomal-dominant pure or uncomplicated hereditary spastic paraplegia. It is caused by mutations in SPG3A, the only gene associated with this condition. We identified a novel mutation, c.1040T>C (p. M347T), in a family with axonal neuropathy in addition to spastic paraplegia. This expands the spectrum of neurologic complications associated with SPG3A and highlights the importance of long-term follow-up and neurological surveillance in this patient population.

A novel CASR mutation associated with neonatal severe hyperparathyroidism transmitted as an autosomal recessive disorder

Abstract Background: Neonatal severe primary hyperparathyroidism (NSHPT, MIM 239200) is most often an isolated disorder that is due to biallelic inactivating mutations in the CASR, the gene encoding the calcium sensing receptor; NSHPT is inherited from parents with familial hypocalciuric hypercalcemia, each of whom has one mutated CASR allele. Objectives: To report clinical and genetic findings in a brother and sister with NSHPT due to a novel mutation in the CASR transmitted as an autosomal recessive trait and to examine the functional effect of the mutation. Subjects and methods: A brother and sister with marked hypercalcemia due to NSHPT were identified; the boy also had craniosynostosis requiring surgical repair. The genotyping of the CASR in both children and their parents who were eucalcemic and normophosphatemic was undertaken. In order to examine the significance of the variant CASR identified, the CASR variant was expressed in vitro and examined by three computer computational programs [PolyPhen2, MutationTaster, Sorting Intolerant From Tolerant (SIFT)] designed to evaluate the effect of a nucleotide variant on the structure and likely functional consequence upon the protein product. Results: A sequence variant in the CASR was identified [G>T point mutation at nucleotide c.2303 in exon 7 (c.2303G>T) resulting in the replacement of glycine by valine at codon 768 (p.Gly768Val)]. Two copies of this CASR variant were present in the genome of the siblings while a single copy of the CASR variant was present in both of the clinically and biochemically normal parents, a pattern of transmission consistent with autosomal recessive inheritance of NSHPT in this family. When expressed in HEK293 cells in vitro, the novel Gly768Val variant did not interfere with protein generation or migration to the cell membrane in vitro. The analysis of the functional effect of the Gly768Val CASR variant by the PolyPhen2, MutationTaster, and Sorting Intolerant From Tolerant computer programs revealed that this mutation was very likely to be deleterious. Conclusion: The NSHPT associated with biallelic Gly768Val mutations of the CASR in two siblings with severe hypercalcemia and hyperparathyroidism and their clinically and biochemically normal heterozygous parents was transmitted as an autosomal recessive disorder in this family.

Biomedical Publications Profile and Trends in Gulf Cooperation Council Countries

OBJECTIVES There is a dearth of studies examining the relationship between research output and other socio-demographic indicators in the Gulf Cooperation Council (GCC) countries (Bahrain, Kuwait, Oman, Qatar, Saudi Arabia, and the United Arab Emirates). The three interrelated aims of this study were, first, to ascertain the number of biomedical publications in the GCC from 1970 to 2010; second, to establish the rate of publication according population size during the same period and, third, to gauge the relationship between the number of publications and specific socio-economic parameters. METHODS The Medline database was searched in October 2010 by affiliation, year and publication type from 1970 to 2010. Data obtained were normalised to the number of publications per million of the population, gross domestic product, and the number of physicians in each country. RESULTS The number of articles from the GCC region published over this 40 year period was 25,561. Saudi Arabia had the highest number followed by Kuwait, UAE, and then Oman. Kuwait had the highest profile of publication when normalised to population size, followed by Qatar. Oman is the lowest in this ranking. Overall, the six countries showed a rising trend in publication numbers with Oman having a significant increase from 1990 to 2005. There was a significant relationship between the number of physicians and the number of publications. CONCLUSION The research productivity from GGC has experienced complex and fluctuating growth in the past 40 years. Future prospects for increasing research productivity are discussed with particular reference to the situation in Oman.

Homozygosity for FARSB mutation leads to Phe-tRNA synthetase-related disease of growth restriction, brain calcification, and interstitial lung disease

Aminoacyl‐tRNA synthetases (ARSs) canonical function is to conjugate specific amino acids to cognate tRNA that are required for the first step of protein synthesis. Genetic mutations that cause dysfunction or absence of ARSs result in various neurodevelopmental disorders. The human phenylalanine‐tRNA synthetase (PheRS) is a tetrameric protein made of two subunits coded by FARSA gene and two subunits coded by FARSB gene. We describe eight affected individuals from an extended family with a multisystemic recessive disease manifest as a significant growth restriction, brain calcifications, and interstitial lung disease. Genome‐wide linkage analysis and whole exome sequencing identified homozygosity for a FARSB mutation (NM_005687.4:c.853G > A:p.Glu285Lys) that co‐segregate with the disease and likely cause loss‐of‐function. This study further implicates FARSB mutations in a multisystem, recessive, neurodevelopmental phenotype that share clinical features with the previously known aminoacyl‐tRNA synthetase‐related diseases.

Reanalysis of exome sequencing data of intellectual disability samples: Yields and benefits

Recently, with the advancement in next generation sequencing (NGS) along with the improvement of bioinformatics tools, whole exome sequencing (WES) has become the most efficient diagnostic test for patients with intellectual disability (ID). This study aims to estimate the yield of a reanalysis of ID negative exome cases after data reannotation.

Further delineation of Temtamy syndrome of corpus callosum and ocular abnormalities

Temtamy syndrome is a syndromic form of intellectual disability characterized by ocular involvement, epilepsy and dysgenesis of the corpus callosum. After we initially mapped the disease to C12orf57, we noted a high carrier frequency of an ancient startloss founder mutation [c.1A>G; p.M1?] in our population, and variable phenotypic expressivity in newly identified cases. This study aims to combine 33 previously published patients with 23 who are described here for the first time to further delineate the phenotype of this syndrome. In addition to the known p.M1? founder, we describe four novel homozygous variants, thus increasing the number of Temtamy syndrome‐related C12orf57 variants to seven, all but one predicted to be loss of function. While all patients presented with intellectual disability/developmental delay, the frequency of other phenotypic features was variable: 73.2% (41/56) had epilepsy, 63% (34/54) had corpus callosal abnormalities, 14.5% (8/55) had coloboma, and 16.4% (9/55) had microphthalmia. Our analysis also revealed a high frequency of less recognized features such as congenital heart disease (51.4%), and brain white matter abnormalities (38%, 19/50). We conclude that C12orf57 variants should be considered in the etiology of developmental delay/intellectual disability, even when typical syndromic features are lacking, especially in those who trace their ancestry to Saudi Arabia where a founder C12orf57 mutation is among the most common recessive causes of intellectual disability.

The Pediatric Cerebellum in Inherited Neurodegenerative Disorders: A Pattern-recognition Approach

Evaluation of imaging studies of the cerebellum in inherited neurodegenerative disorders is aided by attention to neuroimaging patterns based on anatomic determinants, including biometric analysis, hyperintense signal of structures, including the cerebellar cortex, white matter, dentate nuclei, brainstem tracts, and nuclei, the presence of cysts, brain iron, or calcifications, change over time, the use of diffusion-weighted/diffusion tensor imaging and T2*-weighted sequences, magnetic resonance spectroscopy; and, in rare occurrences, the administration of contrast material.