Clinical and molecular cross-sectional study of a cohort of adult type III spinal muscular atrophy patients: Clues from a biomarker study

Francesco Danilo Tiziano, Lorena Di Pietro, Rosa Lomastro, Stefania Fiori, Carla Angelozzi, Emanuela Abiusi, Gessica Vasco, Maria Barbara Pasanisi, Corrado Angelini, Gianni Sorarù, Alessandra Gaiani, Tiziana Mongini, Liliana Vercelli, Giuseppe Vita, Gian Luca Vita, Sonia Messina, Luisa Politano, Luigia Passamano, Grazia Di Gregorio, Cristina MontomoliChiara Orsi, Angela Campanella, Renato Mantegazza, Lucia Morandi

Research output: Contribution to journalArticle

28 Citations (Scopus)

Abstract

Proximal spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disorder caused by mutations of the SMN1 gene. Based on severity, three forms of SMA are recognized (types I-III). All patients usually have 2-4 copies of a highly homologous gene (SMN2), which produces insufficient levels of functional survival motor neuron (SMN) protein due to the alternative splicing of exon 7. The availability of potential candidates to the treatment of SMA has raised a number of issues, including the availability of biomarkers. This study was aimed at evaluating whether the quantification of SMN2 products in peripheral blood is a suitable biomarker for SMA. Forty-five adult type III patients were evaluated by Manual Muscle Testing, North Star Ambulatory Assessment scale, 6-min walk test, myometry, forced vital capacity, and dual X-ray absorptiometry. Molecular assessments included SMN2 copy number, levels of full-length SMN2 (SMN2-fl) transcripts and those lacking exon 7 and SMN protein. Clinical outcome measures strongly correlated to each other. Lean body mass correlated inversely with years from diagnosis and with several aspects of motor performance. SMN2 copy number and SMN protein levels were not associated with motor performance or transcript levels. SMN2-fl levels correlated with motor performance in ambulant patients. Our results indicate that SMN2-fl levels correlate with motor performance only in patients preserving higher levels of motor function, whereas motor performance was strongly influenced by disease duration and lean body mass. If not taken into account, the confounding effect of disease duration may impair the identification of potential SMA biomarkers.
Original languageEnglish
Pages (from-to)630-636
Number of pages7
JournalEuropean Journal of Human Genetics
Volume21
DOIs
Publication statusPublished - 2013

Keywords

  • Adolescent
  • Adult
  • Biomarkers
  • Biomechanical Phenomena
  • Body Weight
  • Cohort Studies
  • Cross-Sectional Studies
  • Female
  • Genetic Loci
  • Genetics
  • Genetics (clinical)
  • Genotype
  • Humans
  • Male
  • Middle Aged
  • Motor Activity
  • RNA, Messenger
  • Range of Motion, Articular
  • SMN
  • Spinal Muscular Atrophies of Childhood
  • Survival of Motor Neuron 2 Protein
  • Vital Capacity
  • Young Adult
  • biomarker
  • outcome measure
  • real-time PCR
  • spinal muscular atrophy

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