Aberrant GRIA3 transcripts with multi‐exon duplications in a family with X‐linked mental retardation

Investigation of chromosomal rearrangements in patients with mental retardation (MR) is particularly informative in the search for novel genes involved in MR. We report on a family with a genomic duplication at Xq25 identified by oligo array‐CGH. Further characterization showed a partial tandem duplication of GRIA3 extending from exon 1 to exon 12. This duplication is present in two brothers with MR and on one allele in their sister with normal phenotype and completely skewed X‐chromosome inactivation. The duplication is inherited from the mother, whose cognitive level is low and X‐chromosome inactivation is random. This is the second family with partial duplication of GRIA3 associated with MR. GRIA3 expression studies in our case demonstrated a new mechanism for GRIA3 dysfunction with the presence of aberrant GRIA3 transcripts carrying multi‐exon duplications leading to a frameshift. Our study gives additional support to the implication of GRIA3 in X‐linked MR. © 2009 Wiley‐Liss, Inc.

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