Studies from University of the Witwatersrand, National Health Laboratory Service reveal new findings on spinal muscular atrophy genetics
2007 NOV 5 -- Current study results from the report, 'The molecular basis of spinal muscular atrophy (SMA) in South African black patients,' have been published. According to recent research published in the journal Neuromuscular Disorders, "SMA is an autosomal recessive disorder that results in symmetrical muscle weakness and wasting due to degeneration of the anterior horns of the spinal cord. The gene for SMA, the survival motor neuron (SMN) gene is found on chromosome 5q13, in a region harbouring a 500kb duplication, resulting in two copies (a telomeric and a centromeric) of each of the genes found within the duplication." "SMN1 is homozygously deleted in approximately 95% of patients worldwide. Results of the current study show that only 51% (42/92) of South African black SMA patients have homozygous deletions of the SMN1 gene. This frequency is significantly lower than observed in the South African white patient group and in other international populations. The pattern of deletions in the South African black patients is also significantly different. In order to elucidate the molecular basis of SMA in the black population, a dosage assay enabling the detection of SMN1 deletion heterozygotes was independently developed. This assay confirmed SMN1 heterozygosity in at least 70% of black non-deletion SMA patients. However, no second disease-causing mutation or a common chromosomal background for this mutation could be identified in these patients. The frequency of SMA in both the black and white population was also determined using the SMN1 gene dosage assay. Results showed that SMA is more common than previously thought with carrier rates of 1 in 50 and 1 in 23 and a predicted birth incidence of 1 in 3574 and 1 in 1945 in the black population and the white population, respectively. Development and incorporation of the SMN1 dosage assay into the molecular diagnostic service will increase the percentage of cases in which the diagnosis of SMA can be confirmed and allow preclinical and prenatal diagnosis," wrote R. Labrum and colleagues, University of the Witwatersrand, National Health Laboratory Service. The researchers concluded: "Further gene characterisation and functional studies would need to be performed in order to further define the molecular basis of SMA in the South African black population." Labrum and colleagues published their study in Neuromuscular Disorders (The molecular basis of spinal muscular atrophy (SMA) in South African black patients. Neuromuscular Disorders, 2007;17(9-10):684-92). For additional information, contact R. Labrum, School of Pathology, Division of Human Genetics, National Health Laboratory Service and University of the Witwatersrand PO Box 1038, Johannesburg 2000, South Africa. The publisher's contact information for the journal Neuromuscular Disorders is: Pergamon-Elsevier Science Ltd., the Boulevard, Langford Lane, Kidlington, Oxford OX5 1GB, England. Keywords: South Africa, Johannesburg, Spinal Muscular Atrophy Genetics, Charcot-Marie-Tooth Disease, Neurology, Spinal Muscular Atrophy. This article was prepared by Pain & Central Nervous System Week editors from staff and other reports. Copyright 2007, Pain & Central Nervous System Week via NewsRx.com.
|
