title: Evidence of a segregation ratio distortion of SMN1 alleles in spinal muscular atrophy.
abstract: Spinal muscular atrophy (SMA) is an autosomal recessive disorder characterised by degeneration and loss of the motor neurons of the anterior horn of the spinal cord. The absence of SMN1 is determinant to have SMA and parents of SMA patients are regarded as carriers of the disease. We compared the segregation ratio of the mutated allele and the wild-type allele of all the confirmed carrier parents assuming Mendelian proportions. Results of transmissions in 235 prenatal tests and in 128 unaffected siblings showed a statistically significant deviation in favour of the wild-type SMN1 allele. The number of affected foetuses and carriers were lower than that expected. No significant differences in the sex ratio or in the progenitor origin of the transmitted allele to the carriers were found. One hypothesis that has been advanced to account for the distortion observed in affected foetuses is the negative postzygote selection due to early miscarriage. However, given that the number of carriers in our series was lower than expected, prezygote events such as meiotic drive, survival of gametes or preferential fertilisation should also be considered.
authors.affiliation: Department of Genetics, Hospital de Sant Pau, Barcelona, Spain.
authors.forename: Laura
authors.initials: L
authors.lastname: Alias
authors.forename: Maria J
authors.initials: MJ
authors.lastname: Barceló
authors.forename: Ignasi
authors.initials: I
authors.lastname: Gich
authors.forename: Marta
authors.initials: M
authors.lastname: Estapé
authors.forename: Juan
authors.initials: J
authors.lastname: Parra
authors.forename: Maria
authors.initials: M
authors.lastname: Amenedo
authors.forename: Montserrat
authors.initials: M
authors.lastname: Baiget
authors.forename: Eduardo F
authors.initials: EF
authors.lastname: Tizzano
mesh_terms: D000483:Alleles; D017362:Cyclic AMP Response Element-Binding Protein / Q000235:genetics*; D005260:Female; D005787:Gene Frequency; D005808:Genes, Recessive; D006579:Heterozygote; D006720:Homozygote; D006801:Humans; D008297:Male; D009134:Muscular Atrophy, Spinal / Q000175:diagnosis / Q000235:genetics*; D009419:Nerve Tissue Proteins / Q000235:genetics*; D011247:Pregnancy; D011296:Prenatal Diagnosis; D016601:RNA-Binding Proteins / Q000235:genetics*; D055532:SMN Complex Proteins; D055533:Survival of Motor Neuron 1 Protein
chemical_list: D017362:Cyclic AMP Response Element-Binding Protein; D009419:Nerve Tissue Proteins; D016601:RNA-Binding Proteins; D055532:SMN Complex Proteins; C526471:SMN1 protein, human; D055533:Survival of Motor Neuron 1 Protein