T. Tønnesen

Menkes Disease: An X-Linked Neurological Disorder of the Copper Metabolism

Menkes disease is an X‐linked, recessive disturbance of copper metabolism associated with a progressive clinical course and abnormal hair. The disease is dominated by neurological symptoms combined with connective tissue manifestations, most of which can be explained by the lack of important copper enzymes. Despite excessive accumulation of the metal in various tissues, a functional copper deficiency is evident, probably caused by a defective intracellular copper transport protein of unknown nature. The molecular basis of the copper disturbance has proven difficult to define and will most likely have to await cloning of the gene. The chromosomal region of interest has now been narrowed down to a sub‐band on the long arm of the chromosome (Xq13.3), and positional cloning is in progress in a number of laboratories including our own. Identification of the Menkes gene will be of importance for our understanding of the cellular handling of copper and other trace elements.

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

SummaryDuring 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 subjects 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.

First trimester prenatal diagnosis of Menkes disease by DNA analysis.

Menkes disease is an X linked recessive disorder of copper metabolism characterised by neurological symptoms and connective tissue manifestations. The defective gene in Menkes disease has recently been isolated and the gene product is predicted to be a copper transporting ATPase. The diagnosis of Menkes disease has hitherto been performed by biochemical analysis, based on intracellular accumulation of copper. Cloning the gene opened up the possibility of establishing precise and reliable carrier and prenatal diagnosis by defining the molecular defect. In this report we describe the partial deletion of the Menkes gene in a patient who had inherited the mutation from his phenotypically normal mother. This information enabled us to perform prenatal diagnosis by direct mutation analysis of the mothers sixth pregnancy and we detected the same deletion, indicating that the male fetus was affected. This first prenatal diagnosis of Menkes disease by direct mutation analysis shows some advantages of DNA analysis compared to biochemical diagnosis.

First trimester biopsies of chorionic villi for prenatal diagnosis: experience of two laboratories

First trimester prenatal diagnosis has been introduced in Europe by Simoni et al. (1983), about 10 years after the previous attempts by Hahnemann and Mohr (Hahnemann 19741, and Kullander & Sandhal (1973). The Italian group has recently reported their first 100 diagnostic cases (Simoni et al. 1984). Also in Scandinavia a growing number of diagnostic cases has been studied, many in high risk pregnancies (Table 1) or in cases where the mother already had experienced a second trimester abortion because of an affected fetus. Metabolic studies on chorionic villi, have established normal enzyme levels (Table 2) and also the amount of tissue necessary for a successful determination (Gustavii et al. 1984). Chromosome studies have been carried out with a direct preparation method or after 24 h culture, following the protocol of Simoni et al. (1983) with minor modifications. Long-time culture after trypsination of the villi have also been carried out with more or less success. The direct method as well as incubation of villi for 12-24 h demand dissociation with 60% acetic acid. Q-banding is the method of choice for karyotyping. After long-time culture, elongated chromosomes are found and better banding is achieved. Prometaphase chromosomes for the analysis of special cases, e.g. translocations, can be prepared using ethidium bromide before harvesting. The early prenatal diagnosis gives possibilities to diagnose severe genetic disease early enough for an interruption of pregnancy before the 12th week, and also to diagnose chromosome aberrations rarely seen or not at all seen in liveborns or a t the 16th week of pregnancy (Table 3).

Copper‐measurement in a muscle‐biopsy. A possible method for postmortem diagnosis of Menkes disease

A 5‐month‐old boy showed severe delay in mental and motor development. His hair was normal. He died at 18 months from bronchopneumonia. Autopsy of the brain revealed meningo‐cerebral angiodysplasia with tortuous vessels at the surface of the brain. This raised a suspicion of Menkes disease.

Paternal non-disjunction in a 46,XY/47,XXY individual with a fragile 17p12 in the mother.

In a family where the mother carried a fragile site at 17p12, RFLP‐analysis with the X‐specific probe 11.28 showed that the 46, XY/47, XXY mosaicism detected in her Klinefelter son was due to a non‐disjunctional event in paternal meiosis I, followed by a secondary loss of an X‐chromosome by a mitotic non‐disjunction. Thus, an association between the primary meiotic non‐disjunction and the presence of the fragile site could be excluded.