Spinal muscular atrophy carrier frequency in Saudi Arabia.

BACKGROUND: Spinal Muscular Dystrophy (SMA) is one of the leading causes of death in infants and young children from heritable diseases. Although no large-scale popultion-based studies have been done in Saudi Arabia, it is reported that the incidence of SMA is higher in the Saudi population partly because of the high degree of consanguineous marriages. METHODS: The final analysis included 4198 normal volunteers aged between 18 and 25 years old, 54.7% males, and 45.3% females. Whole blood was spotted directly from finger pricks onto IsoCode StixTM and genomic DNA was isolated using one triangle from the machine. To discern the SMN1 copy number independently from SMN2, Multiplex PCR with Dral restriction fragment analysis was completed. We used the carrier frequency and population-level data to estimate the prevalence of SMA in the population using the life-table method. RESULTS: This data analysis showed the presence of one copy of the SMN1 gene in 108 samples and two copies in 4090 samples, which resulted from a carrier frequency of 2.6%. The carrier frequency was twofold in females reaching 3.7% compared to 1.6% in males. 27% of participants were children of first-cousin marriages. We estimated the birth incidence of SMA to be 32 per 100,000 birth and the total number of people living with SMA in the Kingdom of Saudi Arabia to be 2265 of which 188 are type I, 1213 are type II, and 8,64 are type III. CONCLUSION: The SMA carrier rate of 2.6% in Saudi control subjects is slightly higher than the reported global frequency of 1.25 to 2% with links to the high degree of consanguinity.

A Comprehensive Analysis of Unique and Recurrent Copy Number Variations in Alzheimer's Disease and its Related Disorders.

BACKGROUND: Copy number variations (CNVs) play an important role in the genetic etiology of various neurological disorders, including Alzheimer's disease (AD). Type 2 diabetes mellitus (T2DM) and major depressive disorder (MDD) were shown to have share mechanisms and signaling pathways with AD. OBJECTIVE: We aimed to assess CNVs regions that may harbor genes contributing to AD, T2DM, and MDD in 67 Saudi familial and sporadic AD patients, with no alterations in the known genes of AD and genotyped previously for APOE. METHODS: DNA was analyzed using the CytoScan-HD array. Two layers of filtering criteria were applied. All the identified CNVs were checked in the Database of Genomic Variants (DGV). RESULTS: A total of 1086 CNVs (565 gains and 521 losses) were identified in our study. We found 73 CNVs harboring genes that may be associated with AD, T2DM or MDD. Nineteen CNVs were novel. Most importantly, 42 CNVs were unique in our studied cohort existing only in one patient. Two large gains on chromosomes 1 and 13 harbored genes implicated in the studied disorders. We identified CNVs in genes that encode proteins involved in the metabolism of amyloid-ß peptide (AGRN, APBA2, CR1, CR2, IGF2R, KIAA0125, MBP, RER1, RTN4R, VDR and WISPI) or Tau proteins (CACNAIC, CELF2, DUSP22, HTRA1 and SLC2A14). CONCLUSION: The present work provided information on the presence of CNVs related to AD, T2DM, and MDD in Saudi Alzheimer's patients.

Genetic Study of Alzheimer's Disease in Saudi Population.

BACKGROUND: Alzheimer's disease (AD) is a chronic neurological disorder associated with mental decline and dementia. Several studies focused on investigating the molecular basis of the disease that led to the identification of several causative genes and risk associated alleles. Replication of these studies and findings from different populations is very important. OBJECTIVE: Molecular assessment of a cohort of 117 familial and sporadic AD cases from Saudi Arabia. METHODS: Comprehensive screening for point mutations was carried out by direct sequencing of coding regions in the three known AD causative genes: PSEN1, PSEN2, APP, as well as the AD associated gene SORL1. All patients were also genotyped for APOE alleles. In silico 3D protein structure analysis was performed for two novel SORL1 variants. RESULTS: We identified a total of eight potential pathogenic missense variants in all studied genes. Five of these variants were not previously reported including four in SORL1 (p.Val297Met, p.Arg1084Cys, p.Asp1100Asn, and p.Pro1213Ser) and one in APP (p.Glu380Lys). The frequency of APOE-ɛ4 allele was 21.37% of total investigated cases. In silico 3D protein structure analysis of two SORL1 novel missense variants (p.Pro1213Ser and p.Arg1084Cys) suggested that these variants may affect the folding of the proteins and disturb their structure. CONCLUSIONS: Our comprehensive analysis of the open reading frame of the known genes have identified potential pathogenic rare variants in 18/117 cases. We found that point mutations in AD main genes (PSEN1, PSEN2, and APP) were underrepresented in our cohort of patients. Our results confirm involvement of SORL1 in familial and sporadic AD cases.

Novel presenilin 1 mutation associated with early-onset Alzheimer`s disease in a Saudi patient.

We report a 60-year-old Saudi patient with the clinical diagnosis of Alzheimer`s disease (AD) and a novel mutation in the presenilin gene. We investigated mutations in the presenilin-1 gene in Saudi patients with AD using polymerase chain reaction and direct DNA sequencing methods. We extracted genomic DNA from the whole blood of both patients and normal control individuals. We sequenced and compared amplicons with the sequences of the respective exons of normal individuals as well as data available in GenBank. We detected a homozygous mutation (g-c) in exon 12, resulting in the missense mutation (Arg377Thr), in the DNA of a 60-year-old patient. We located this mutation in the cytoplasmic loop near the transmembrane domain 7.

Molecular analysis of the spinal muscular atrophy and neuronal apoptosis inhibitory protein genes in Saudi patients with spinal muscular atrophy.

OBJECTIVE: Spinal muscular atrophy (SMA) is a common, often fatal, autosomal recessive disease leading to progressive muscle wasting and paralysis as a result of degeneration of anterior horn cells of the spinal cord. The prevalence of SMA cases in the Kingdom of Saudi Arabia (KSA) is much higher than the European and North American population. Deletions or mutations in 2 genes, telomeric form of the survival motor neuron (SMN1) and the neuronal apoptosis inhibitory protein (NAIP), are known to be associated with SMA. The aim of this study is to examine the deletions or interruptions of the SMN1 and NAIP genes in Saudi patients. METHODS: The study included 121 Saudi SMA patients [type I (60 patients); type II (26 patients); and type III (35 patients)]. The deletions or interruptions of the SMN1 and NAIP genes were detected by using polymerase chain reaction. The study was carried out at the King Fahad National Guard Hospital, Riyadh, KSA between 2000 and 2002. RESULTS: The homozygous deletions of exons 7 and 8 of the SMN1 gene were found in 94% and 87% of the patients. Exon 5 of the NAIP gene was deleted in 70%, but its deletion was more frequent in SMA type I (93%) as compared to type II (54%) and type III (43%). Seven patients with SMA diagnosis did not show any of the above homozygous deletions. All 230 control subjects had at least one copy of both SMN1 and NAIP genes, as expected. CONCLUSION: Our results demonstrate that the deletion rate (94%) of the SMN1 gene in Saudi SMA patients is similar, irrespective of types, compared with patients of other ethnic groups. We also show that the incidence of NAIP deletion is higher in the more severe SMA cases and the dual deletion of the SMN1 and NAIP genes are more common in Saudi SMA type I patients compared with patients of other ethnic groups.

Deletion mutations in the dystrophin gene of Saudi patients with Duchenne and Becker muscular dystrophy.

OBJECTIVE: The deletion in the dystrophin gene has been reported for many ethnic groups, but until now the mutations in this gene have not been thoroughly investigated in Saudi patients with Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD). We examined the deletion pattern in the dystrophin gene of the Saudi patients applying multiplex-polymerase chain reaction (PCR). The aim of this study is to describe the outcome of our initial effort to identify mutations in the dystrophin gene in a representative group of Saudi patients with DMD and BMD. METHODS: Genomic deoxyribose nucleic acid was isolated from 41 patients with DMD and BMD (27 patients confirmed by muscle biopsy and 14 patients with clinical suspicion), 3 patients with limb girdle muscular dystrophy, 12 male relatives of the patients, and 5 healthy Saudi volunteers. A total of 25 exons around the deletion prone regions (hot spots) of the dystrophin gene were amplified. The study was carried out at the King Fahad National Guard Hospital, Riyadh, Kingdom of Saudi Arabia between 2000 and 2002. RESULTS: The deletion of one or more exons was found in 21 of 27 DMD and BMD patients confirmed by muscle biopsy. The deletion in the gene was detected in 5 of 14 patients with DMD diagnosis, but not confirmed by dystrophin staining of muscle biopsy. No deletion in the dystrophin gene was detected in control Saudi volunteers, the limb girdle dystrophy patients, and the relatives of patients, as expected. CONCLUSION: The present study suggests that intragenic dystrophin gene deletions occur with the same frequency in Saudi patients compared with other ethnic groups. The PCR-based deletion analysis provides a reasonable first step in the diagnostic care of Saudi patients who may be afflicted with DMD and BMD.

Stroke in Saudi Arabia.

In this review, the authors summarize 10 years of work on stroke in Saudi Arabia that has led to more than 25 publications. The incidence and prevalence of strokes were low when compared to those reported from Western countries, but this was mainly due to the younger age of the population. The overall distribution of stroke types was not different from that reported in other communities, with the exception of the low incidence of subarachnoid hemorrhage. However, the relatively high frequency of strokes in the young and strokes related to small artery disease, i.e. lacunar infarcts and cerebral hemorrhage, and the high prevalence of diabetes mellitus as a risk factor were quite distinctive. On the other hand, extracranial large artery disease was quite rare. Undetected and untreated hypertension and a low frequency of cigarette smoking in the stroke-prone age group could be one explanation of these findings.