Mosaicism for FMR1 and FMR2 deletion: a new case

DNA repair/replication transcripts are down regulated in patients with Fragile X Syndrome

“…This prevalence rate has been subsequently substantiated by other reports, thus the rate is generally regarded as the prevalence rate in a randomly mating population [3]. FXS is a spectrum disorder in which affected individuals have IQs ranging from low or moderate to high functioning [4,5]. In over 98% of patients, FXS is caused by expansion of the CGG repeats in the 5’ untranslated region of FMR1 located adjacent to exon1 on the X chromosome [6,7].…”

Familial intellectual disability and autistic behavior caused by a small FMR2 gene deletion

“…Whereas deletions within the FMR1 gene also have been recognized as causing FRAXA [Coffee et al, 2008] little is known about deletions of the FMR2 gene as potential cause of FRAXE in the absence of the trinucleotide expansion. Several reports on large deletions including the FMR1 , FMR2 , and other adjacent genes like IDS and SLITRK2 have been published [Timms et al, 1997; Moore et al, 1999; Fengler et al, 2002; Probst et al, 2007; Cavani et al, 2011]. However, reports on alterations affecting only the FMR2 gene are, to the extent of our knowledge, limited to descriptions of a balanced translocation having the breakpoint within the FMR2 gene [Honda et al, 2007] and two submicroscopic deletions which originally led to the cloning of the FMR2 gene [Gedeon et al, 1995; Gecz et al, 1996].…”

FMR1, FMR2, and SLITRK2 deletion inside a paracentric inversion involving bands Xq27.3–q28 in a male and his mother

“…Twenty‐two showed large deletions, up to 13 Mb in size, generally not associated with CGG instability, but caused by meiotic or mitotic ectopic recombination. In this latest group, 12 patients (8 females and 4 males) showed deletions encompassing both FMR1 and FMR2 (OMIM 300806) [Clarke et al, 1992; Dahl et al, 1995; Birot et al, 1996; Wolff et al, 1997; Moore et al, 1999; Fengler et al, 2002; Probst et al, 2007]. In addition to severe mental retardation, seizures were reported in some of these latest patients.…”

“…Since the only DNA sample available from the mother was extracted from a lymphoblastoid cell line and considering the recent demonstration of the probable monoclonality or near monoclonality of this kind of cell lines [Plagnol et al, 2008], methylation studies on the mother could not be taken into consideration. Actually, in the literature only one out of the eight females described with both FMR1 and FMR2 deletion had a normal phenotype [Wolff et al, 1997]; another one, daughter of the previous, presented learning difficulties [Wolff et al, 1997]; while the remaining six showed mild‐to‐severe mental retardation [Clarke et al, 1992; Dahl et al, 1995; Birot et al, 1996; Wolff et al, 1997; Moore et al, 1999; Fengler et al, 2002; Probst et al, 2007].…”