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Loss of SLC38A5 and FTSJ1 at Xp11.23 in three brothers with non-syndromic mental retardation due to a microdeletion in an unstable genomic region

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Abstract

Using high resolution X chromosome array-CGH we identified an interstitial microdeletion at Xp11.23 in three brothers with moderate to severe mental retardation (MR) without dysmorphic features. The extent of the deletion was subsequently delineated to about 50 kb by regular PCR and included only the SLC38A5 and FTSJ1 genes. The loss of the FTSJ1 MR gene in males is expected to result in the observed phenotype but the contribution of the deletion of the solute carrier SLC38A5 gene is less clear. Their mother also carries the deletion and completely inactivates the aberrant X chromosome. Interestingly, the distal breakpoint is situated within a 200 kb SSX repeat region that appears to stimulate recombination since subtle copy number changes often occur at this location and it is frequently involved in translocations in tumours. Since this apparent SSX unstable structure is flanked proximally by FTSJ1 and PQBP1, subtle deletions or duplications at this location would be expected to cause MR, as in our family. So far, we have screened a cohort of 300 patients but did not find additional aberrations at the FTSJ1 locus indicating that the frequency is likely to be low.

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Acknowledgments

We would like to thank the family for their long time cooperation and gratefully acknowledge the support of the NSW Department of Health and Michael Partington’s editorial assistance. We are grateful to Karen Hollanders for excellent technical assistance. This work was supported by a European Union grant QLG3-CT-2002-01810 (EuroMRX Consortium). M.B. is supported by the IWT (Instituut voor Innovatie door Technologie en Wetenschap), Flanders, Belgium.

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Correspondence to Guy Froyen.

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Froyen, G., Bauters, M., Boyle, J. et al. Loss of SLC38A5 and FTSJ1 at Xp11.23 in three brothers with non-syndromic mental retardation due to a microdeletion in an unstable genomic region. Hum Genet 121, 539–547 (2007). https://doi.org/10.1007/s00439-007-0343-1

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