MAPPING OF THE MENKES LOCUS TO XQ13.3 DISTAL TO THE X-INACTIVATION CENTER BY AN INTRACHROMOSOMAL INSERTION OF THE SEGMENT XQ13.3-Q21.2

During a systematic chromosomal survey of 167 unrelated boys with the X-linked recessive Menkes disease (MIM 309400), a unique rearrangement of the X chromosome was detected, involving an insertion of the long arm segment Xq13.3-q21.2 into the short arm at band Xp11.4, giving the karyotype 46,XY,ins(X) (p11.4q13.3q21.2). The same rearranged X chromosome was present de novo in the subject's phenotypically normal mother, where it was preferentially inactivated. The restriction fragment length polymorphism and methylation patterns at DXS255 indicated that the rearrangement originated from the maternal grandfather. Together with a previously described X; autosomal translocation in a female Menkes patient, the present finding supports the localization of the Menkes locus (MNK) to Xq13, with a suggested fine mapping to sub-band Xq13.3. This localization is compatible with linkage data in both man and mouse. The chromosomal bend associated with the X-inactivation center (XIC) was present on the proximal long arm of the rearranged X chromosome, in line with a location of XIC proximal to MNK. Combined data suggest the following order: Xcen-XIST(XIC), DXS128-DXS171, DXS56-MNK-PGK1-Xqter.