title: Microdeletion of Xq28 involving the AFF2 (FMR2) gene in two unrelated males with developmental delay.
abstract: Fragile X E (FRAXE) is an X-linked form of intellectual disability characterized by mild to moderate cognitive impairment, speech delay, hyperactivity, and autistic behavior. The folate-sensitive fragile site FRAXE is located in Xq28 approximately 600 kb distal to the fragile X syndrome fragile site (FRAXA) and harbors an unstable GCC (CCG) triplet repeat adjacent to a CpG island in the 5' untranslated region of the AFF2 (FMR2) gene. The disorder results from amplification and methylation of the GCC repeat and resultant silencing of AFF2. Although chromosome abnormalities that disrupt AFF2 have been reported in two individuals with mild-moderate intellectual disability, microdeletions of Xq28 that delete only AFF2 have not been described as a potential cause of FRAXE-intellectual disability. We performed clinical and molecular characterization of two males with 240 and 499 kb deletions, respectively, at Xq28, both of which encompassed only one gene, AFF2. The 240 kb deletion in Patient 1 was intragenic and lead to the loss of 5' exons 2-4 of AFF2; the 499 kb deletion in Patient 2 removed the 5' exons 1-2 of AFF2 including approximately 350 kb upstream of the gene. Both individuals had developmental and speech delay, and one had mild dysmorphism. We predict disruption of AFF2 in these two patients is likely the cause of their overlapping phenotypes.
authors: Signature Genomic Laboratories, PerkinElmer, Inc., Spokane, Washington, USA. trilochan.x.sahoo@questdiagnostics.com
authors: Trilochan
authors: T
authors: Sahoo
authors: Aaron
authors: A
authors: Theisen
authors: Michael
authors: M
authors: Marble
authors: Raymond
authors: R
authors: Tervo
authors: Jill A
authors: JA
authors: Rosenfeld
authors: Beth S
authors: BS
authors: Torchia
authors: Lisa G
authors: LG
authors: Shaffer
mesh_terms: D002675:Child, Preschool; D002872:Chromosome Deletion; D041321:Chromosomes, Human, X; D002658:Developmental Disabilities / Q000175:diagnosis / Q000235:genetics*; D056726:Genetic Association Studies; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D007223:Infant; D008297:Male; D009687:Nuclear Proteins / Q000235:genetics*; D020411:Oligonucleotide Array Sequence Analysis; D012729:Sex Chromosome Aberrations
chemical_list: C099930:AFF2 protein, human; D009687:Nuclear Proteins