Contractions in the second polyA tract of ARX are rare, non-pathogenic polymorphisms

Valerio Conti, Carla Marini, Davide Mei, Melania Falchi, Anna Rita Ferrari, Renzo Guerrini

Research output: Contribution to journalArticlepeer-review


Aristaless related homeobox (ARX) is a transcription factor containing highly conserved octapeptide, homeobox, acidic, and aristaless domains, as well as four polyA tracts. The most frequent ARX mutation found to date in patients with X-linked infantile spasms, Partington syndrome or X-linked mental retardation, is a duplication of 24 bp in exon 2, resulting in the expansion of the second polyA tract. Although the pathogenic role of this expansion has been well characterized, the effect of contractions in the same polyA tract is still debated since different reports have associated contractions to either mental retardation or a normal phenotype. Here, we report two unrelated girls with epilepsy and mental retardation who inherited from their unaffected parents, of either sex, a deletion of 24 bp (c.441_464del), resulting in a contraction of eight alanines in the second polyA tract of ARX. Segregation studies revealed the c.441_464del also in two healthy relatives of one of the patients. This finding supports the hypothesis that this contraction represents a rare, benign polymorphism.

Original languageEnglish
Pages (from-to)164-167
Number of pages4
JournalAmerican Journal of Medical Genetics, Part A
Issue number1
Publication statusPublished - Jan 2011


  • ARX
  • PolyA tract contraction
  • Rare polymorphism
  • Unaffected male carrier

ASJC Scopus subject areas

  • Genetics(clinical)
  • Genetics


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