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a Department of
Paediatrics, Keio University School of Medicine, 35 Shinanomachi,
Shinjuku-ku, Tokyo 160-0016, Japan, b Department of
Paediatrics, Nagasaki University School of Medicine, Nagasaki, Japan, c Department of Paediatrics,
Kyoto University Hospital, Kyoto, Japan
Correspondence to: Dr Ogata.
Received 26 March 1998;
Revised version accepted for publication 14 July 1998
We report on deletion mapping and X inactivation analysis of a
gene for X linked non-specific mental retardation (MRX) at Xp21.3-Xp22.11, on the basis of molecular studies in two families with
Xp microdeletions involving the DAX-1 gene. In family A, mental
retardation (MR) was profound in the older brother with an episode of
adrenal crisis, severe in the younger brother with no episode of
adrenal crisis, and mild to moderate in the sister and the mother with
no signs of adrenal hypoplasia. In family B, MR was absent in the male
patient with adrenal hypoplasia. Polymerase chain reaction for 16 loci
in the middle of Xp showed that the brothers of family A had a small Xp
deletion between DXS7182 and DXS1022, and that the patient of family B
had a tiny Xp deletion between DXS319 and DXS1022. Microsatellite
analysis for tetranucleotide repeats in the promoter region of the
DAX-1 gene and Southern blotting for DAX-1 and DXS28 showed that the sister and the mother of family A were heterozygous for the
interstitial deletion. X inactivation analysis for the methylation
status of the AR gene and the HPRT gene indicated that the normal X and the deleted X chromosome underwent random X inactivation in both the
sister and the mother. The results imply that an MRX gene subject to X
inactivation is present in a roughly 4 Mb region between DXS7182 and
DAX-1, and that reduced expression of the normal MRX gene caused by
random X inactivation results in MR in carrier females.
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  T. Ogata, K. Muroya, N. Matsuo, O. Shinohara, T. Yorifuji, Y. Nishi, Y. Hasegawa, R. Horikawa, and K. Tachibana Turner Syndrome and Xp Deletions: Clinical and Molecular Studies in 47 Patients J. Clin. Endocrinol. Metab., November 1, 2001; 86(11): 5498 - 5508. [Abstract] [Full Text] [PDF]
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 L. Villard, S. Briault, A.-M. Lossi, C. Paringaux, J. Belougne, L. Colleaux, D R Pincus, E Woollatt, J. Lespinasse, A. Munnich, et al. Two unrelated patients with inversions of the X chromosome and non-specific mental retardation: physical and transcriptional mapping of their common breakpoint region in Xq13.1 J. Med. Genet., October 1, 1999; 36(10): 754 - 758. [Abstract] [Full Text]
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