Mailman MD, Hemingway T, Darsey RL, Glasure CE, Huang Y, Chadwick RB, Heinz JW, Papp AC, Snyder PJ, Sedra MS, Schafer RW, Abuelo DN, Reich EW, Theil KS, Burghes AH, de la Chapelle A, Prior TW. Hybrids monosomal for human chromosome 5 reveal the presence of a spinal muscular atrophy (SMA) carrier with two SMN1 copies on one chromosome.
Hum Genet 2001;
108:109-15. [PMID:
11281448 DOI:
10.1007/s004390000446]
[Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
We have analyzed the survival motor neuron gene (SMN1) dosage in 100 parents of children with homozygous SMN1 deletions. Of these parents, 96 (96%) demonstrated the expected one-copy SMN1 carrier genotype. However, four parents (4%) were observed to have a normal two-copy SMN1 dosage. The presence of two intact SMN1 genes in the parent of an affected child indicates either the occurrence of a de novo mutation event or a situation in which one chromosome has two copies of SMN1, whereas the other is null. We have separated individual chromosomes from two of these parents with two-copy SMN1 dosage by somatic cell hybridization and have employed a modified quantitative dosage assay to provide direct evidence that one parent is a two-copy/ zero-copy SMN1 carrier, whereas the other parent had an affected child as the result of a de novo mutation. These findings are important for assessing the recurrence risk of parents of children with spinal muscular atrophy and for providing accurate family counseling.
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