Spinal muscular atrophy (SMA), a leading genetic cause of death in childhood, is caused by deletion of the SMN1 gene, located at chromosome 5q13. The molecular pathogenesis, which results in motor neuron degeneration within the anterior horn of spinal cord, is a focus of debate among scientists. The unique nature of the duplicative 5q chromosomal region provides considerable yet challenging opportunity for disease correction as well as complication in performing molecular diagnosis and understanding the molecular pathogenesis. This article reviewed recent findings in the molecular pathogenesis of SMA as well as the research advances in the molecular diagnosis and therapeutic approaches.
The incidence of HbE/beta (HbE/β) thalassaemia is increasing in Asian countries, including Malaysia. HbE/β thalassaemia is widely acknowledged to have a diverse phenotypic spectrum despite having the same primary genetic background [1,2,3]. Thus, there are HbE/β thalassaemia patients who receive unnecessary treatments which leads to side effects [4], reduced quality of life and wasting health care resources. Ideally, the treatment and management of thalassaemia patients are individually tailored in order to minimise side effects and optimise health care costs. Genetic variants have been widely acknowledged to influence the variability of human phenotypes. Presence of unique genetic modifiers are believed to cause the diversity in HbE/β thalassaemia severity. Milder disease course has been found to be highly associated with Xmn1-Gγ polymorphism (rs7482144), a SNP at HBG2 promoter [1,5,6,7]. So far, there is no association study between Xmn1-Gγ polymorphism and HbE/beta thalassaemia disease severity in Malaysia. This study aims to optimise PCR-RFLP technique for detection of Xmn1-Gγ polymorphism, to determine the frequency of Xmn1-Gγ polymorphism in HbE/β thalassaemia patients and finding its association with the severity of HbE/β thalassaemia patients. This hospital-based cross-sectional study was performed using archived genomic DNAs from 58 subjects with their respective research pro formas. Selected datas were extracted from the pro formas in order to classify patients into 3 disease severity groups using the scoring system by Sripichai et al., (2008) based on 6 parameters. The archived genomic DNAs were genotyped employing Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP) technique. The genotypes were categorised into homozygous variant, heterozygous and homozygous wild type. The genotypes detected were then validated using DNA sequencing analysis. Appropriate statistical analysis was used to determine the association of Xmn1-Gγ polymorphism with the clinical severity of HbE/β thalassaemia. This study had successfully optimised the PCR-RFLP technique for detection of Xmn1-Gγ polymorphism. Out of 58 subjects, the Xmn1-Gγ polymorphisms were detected in 40 subjects (69%) with the majority being heterozygous (CT) (n=38, 66%) and there were only 2 (3%) homozygous variant (TT) subjects. Homozygous wild type (CC) were detected in 18 (31%) subjects. There were no significant association of Xmn1-Gγ polymorphism with the severity of HbE/β thalassaemia patients with p-value of 0.65 for genotype and 0.58 for allele, respectively. In conclusion, this study showed no significant association of Xmn1-Gγ polymorphism with milder disease severity of HbE/β thalassaemia patients. This can be a true finding for the patients in North East Malaysia or due to small sample size. Thus we recommend to have a larger study in order to validate the association of Xmn1-Gγ polymorphism with HbE/β thalassaemia severity. In addition, there may be other genetic factors that interact with Xmn1-Gγ polymorphism as it was not possible to consistently predict phenotype and severity from the presence of Xmn1-Gγ polymorphism alone.
Muscular dystrophy is a group of diseases that result in progressive muscle weakness and atrophy. Duchenne Muscular Dystrophy (DMD) is classified as dystrophinopathy and is an X-linked recessive disease. It is caused by alterations in the dystrophin gene at Xp21.2 encoding 79 exons [1]. It is characterised by progressive muscle wasting that begins at 3 to 5 years, delay in motor development and eventually wheelchair confinement followed by premature death at about 30 years from cardiac or respiratory complications [2]. Genetic etiology of cases of DMD in Malaysia are still scarcely reported. Here, we report the genetic cause in the case of an 11-year-old Kelantanese Malay boy who has progressive muscle weakness since 5 years old. He has difficulty in getting up from sitting and supine position also in climbing up stairs until 1st floor. He has a strong family history of DMD and musculoskeletal problems. His younger brother was diagnosed with DMD by molecular analysis and his maternal uncle died at the age of 16 with musculoskeletal problems but was never investigated. Physical examination revealed no dysmorphic features, positive Gower sign with absent tounge fasciculation. On neurological examination, tendon reflexes and muscle tone for limbs were normal. Muscle power for bilateral upper limbs were normal, however, bilateral lower limbs showed slight reduction in muscle power with calf hypertrophy.
Complex chromosome rearrangements (CCRs) are structural aberrations or rearrangements involving three or more cytogenetics breakpoints on two or more chromosomes [1]. Balanced and unbalanced are known to have significant risk of mental retardation and phenotypic anomalies. CCRs are also associated with infertility in males and recurrent abortion in females. Here we report one case of apparently balanced CCR involving three chromosomes 3, 5 and 12 in a child with abnormal features. G banding and FISH were performed to clarify the nature of this complex abnormality.
Objectives: Chromosomal abnormalities especially aneuploidies are the most common etiology for pregnancy loss. Trisomy 13, trisomy 18 and trisomy 21 are the most common chromosome autosomal aneuploidies with trisomy 21 (Down syndrome) being the most common chromosomal abnormality among liveborn infants. In previous reports, we noted that the recurrence of these aneuploidies in some families may not occur by chance alone.
Methods: Extraction of relevant data from review of medical case notes of a young couple with two offspring with Down syndrome (DS) and Patau syndrome.
Results: A family history of DS is a predisposing factor for both DS and other types of aneuploidy. Certain instances of non-disjunction error are not random.
Conclusion: As the maternal age was not advanced in both pregnancies, there is a possibility that the recurrent aneuploidy in this family may not be accounted by chance alone. The risk of having subsequent affected pregnancy cannot be ignored in this family and prenatal diagnosis is strongly recommended in the subsequent pregnancy.
HbE/β-thalassemia is the most common severe form of thalassemia particularly in SEA region including Malaysia and globally, it comprised of a significant severe form of β-thalassemia disorder. It has various clinical manifestations ranging from very mild anemia to severe manifestation similar to beta thalassemia major. Many different syndromes are observed in HbE/β-thalassemia. Several genetic modifiers have been reported to play important role in contributing to phenotypic variability. The true reasons underlying this phenotypic variability remain unknown. The most reliable predictive factor of the disease phenotype is the nature of the beta globin gene mutation itself. However, the degree of severity is also believed to be affected by other genetic modifiers. For instance, high HbF level ameliorates the clinical severity of β thalassemia patients. Therefore, identification of these genetic modifiers is very important. The association of severe clinical manifestation and the specific β-globin gene mutation has been known. But the wide scope and other potential predictors have been only recently appreciated. This review therefore aimed to reveal the potential genetic modifiers of HbE/βthalassemia patients based on the previous reported studies. A better understanding on the mechanisms underlying the variety of phenotypes of this disease may lead to the direction for a better future management plans. This also promotes “personalized medicine” in patient care.