Diane W. Cox

Wilson disease and Menkes disease: new handles on heavy-metal transport

Little is known at the molecular level about the homeostatic control of heavy-metal concentrations in mammals. Recently, however, two human diseases that disrupt copper transport, Menkes disease and Wilson disease, were found to be caused by mutations in two closely related genes, MNK and WND, which encode proteins belonging to the P-type ATPase family of cation transporters. The MNK and WND proteins are unique in having at their amino termini six copies of a sequence that is remarkably similar to sequences previously found in bacterial heavy-metal-resistance proteins and in a P-type ATPase that appears to form part of a bacterial copper homeostatic system. These two human ATPases are the first putative heavy-metal transporters to be discovered in eukaryotes.

Liver disease associated with alpha1-antitrypsin deficiency in childhood

Liver disease in children with alpha1-antitrypsin deficiency and protease inhibitor type ZZ does not necessarily carry a bad prognosis. Fourteen of our 18 patients presented with the neonatal hepatitis syndrome and four had hepatomegaly without jaundice. Although four patients have died of cirrhosis and its complications, and three have severe liver disease, most of the 11 others, of whom four are over 13 years of age, have relatively little clinical, biochemical, or histologic evidence of liver disease. Persistent elevation of SGOT during the third year of life and renal or pulmonary problems were associated with a poor prognosis. Liver biopsy early in the course of the disease was not helpful prognostically but was useful in assessment of the severity of liver disease and demonstration of alpha1AT storage, alpha1AT deficiency was found in 29% of our patients who presented with the neonatal hepatitis syndrome. One of seven apparently healthy Pi type ZZ sibs of our patients had significant liver disease which had not been suspected previously.

Association of severe rheumatoid arthritis with heterozygosity for α‐antitrypsin deficiency

Genetic types of α1‐antitrypsin (protease inhibitor types, or Pi types) were determined in 108 patients with rheumatoid arthritis. These patients were selected for severely destructive disease and had classical rheumatoid arthritis according to ARA criteria, were seropositive, and had joint erosions shown by X‐ray. Heterozygotes for the deficiency Z allele (Pi types MZ, SZ, etc.) were found among 9.2 % of patients and 3.5 % of a control adult population. The increased frequency in patients was statistically significant. Heterozygotes were most frequent among female patients with an early onset of disease. Heterozygosity for α1‐antitrypsin deficiency may be a factor in familial recurrence of rheumatoid arthritis. Among 98 patients with juvenile rheumatoid arthritis not selected for severity, 4.1 % were Z heterozygotes compared with 1.3 % of control children, not a statistically significant difference. Reduced concentrations of α1‐antitrypsin in Z heterozygotes may be inadequate to inhibit the proteolytic enzymes released into the joints of adults with rheumatoid arthritis during phagocytosis of immune complexes. This may be a factor promoting severe joint destruction.

RHEUMATOID ARTHRITIS AND ALPHA-1-ANTITRYPSIN

The genetic types of alpha1-antitrypsin (Pi types) were studied in 55 adults with classical or definite rheumatoid arthritis and 56 children with juvenile rheumatoid arthritis. A comparison was made with control groups of 211 healthy adults and 512 schoolchildren. Pi types MZ and SZ were significantly more prevalent in adults with rheumatoid arthritis than in the control adults. There was no difference between the patients with juvenile rheumatoid arthritis and the control children. Reduced concentrations of alpha1-antitrypsin, as associated with heterozygotes for the Z allele, may be a contributory factor to the development of rheumatoid arthritis or to the tissue destruction of rheumatoid arthritis.

Localization and genetic linkage of the human immunoglobulin heavy chain genes and the creatine kinase brain (CKB) gene: identification of a hot spot for recombination.

The immunoglobulin heavy chain (IGH) gene cluster and the gene coding for the brain form of the enzyme creatine kinase (CKB) have previously been localized to chromosome 14, at 14q32.3 and 14q32, respectively. Here we report more precise regional localization of these genes by dosage studies using DNA from a child hemizygous for the region from 14q32.32 to 14qter. CKB and IGH are present in a single dose in the proband. Dosage studies in a second patient with a similar but smaller deletion due to a ring chromosome 14 show that CKB is proximal to the IGH cluster. An EcoRI restriction site polymorphism was found with probes for the CKB gene. Linkage analysis of family data indicates that CKB is closely linked to IGH. Linkage analysis also revealed unusually high recombination (beta = 3.2%) between the C delta and C gamma 3 genes of the IGH constant region, which are only 60 kb apart. This finding, in combination with a previous observation of linkage equilibrium in the region, suggests that the C delta-C gamma 3 region contains a recombination hot spot.

The genetics of and associated clinical findings in humero‐radial synostosis

This paper compares the manifestations of sporadic, dominantly inherited and recessively inherited humero‐radial synostosis with the aim of determining ways of separating these forms on clinical grounds. The genetic forms are characterized by bilateral involvement and by lack of the distal ulnar malformations and the absence of digits that are common in the sporadic cases. The majority of patients with the dominantly inherited form have a characteristic pattern of anomalies, including brachymesophalangy, and the recessive cases have a high frequency of malformations in addition to those of the limbs. Consanguinity is frequent in the families of recessive cases. Four additional patients are presented; two of them illustrate many of the features of the phocomelic syndrome reported by Herrmann et al. (1969). A possible teratogenic cause of these cases is discussed.

Deletion/frameshift mutation in the α1 null allele, PI*QObolton

SummaryThe most common deficiency allele of the protease inhibitor (PI) α1 (α1AT) is PI*Z. Other rare deficiency alleles of α1AT are of two types: those producing low but detectable amounts of α1AT (<20% of normal serum concentrations), and null alleles producing <1% of normal α1AT and therefore not detectable by routine quantitative methods. We have previously used DNA polymorphisms and family data to determine heterozygosity in an individual producing low levels of serum α1AT (12% of normal) of PI type Mmalton. By DNA analysis we observed the typical haplotype associated with PI* Mmalton and a unique null haplotype associated with the allele PI*QObolton. The QObolton allele produces no detectable serum α1AT. We have cloned and sequenced the QObolton allele from a phage genomic library. Deletion of a single cytosine residue near the active site of α1AT in exon V results in a frameshift causing an in-frame stop codon downstream of the deletion. This stop codon leads to premature termination of protein translation at amino acid 373, resulting in a truncated protein. The truncated protein is predicted to have an altered carboxy terminus (amino acids 363-) and will lack structurally important amino acids.

DNA markers for the diagnosis of Wilson disease

Wilson disease is an autosomal recessive disorder of copper transport for which the basic defect is unknown. Laboratory diagnosis of Wilson disease is usually made by measuring serum ceruloplasmin concentration, urinary copper excretion, and liver copper concentration. However, discrimination between heterozygotes and patients is sometimes difficult. The gene for Wilson disease has been assigned to chromosome-13 at q14-q21. In this study, 10 markers from the 13q14-13q21 region were investigated in 12 families with a well-established diagnosis, to confirm reported linkage results. Markers from the same region were tested in two additional families, in which a sib of each index case had unclear results with conventional biochemical assays. The linkage results in this study are similar to those of Middle Eastern families, and support the hypothesis of a single disease locus. In the two families studied for diagnostic purposes, the status of 2 presymptomatic sibs was established as affected and 1 as unaffected. This study therefore shows that DNA markers can be used to discriminate between presymptomatic patients and non-affected individuals when biochemical results are equivocal, as long as an index case with Wilson disease of known status is available and markers are informative.

α2-Macroglobulin production by cultured human fibroblasts

Alpha2-macroglobulin (α2M), a high-molecular-weight plasma protease inhibitor has been shown, by both immunological and functional methods, to be produced by cultured adult lung fibroblasts. Cultured skin fibroblasts synthesized approximately one tenth as much α2M as lung fibroblasts. This quantitative difference in α2M production was also demonstrated in fibroblasts of isogenic origin. There was no difference in the amount of α2M produced between adult and fetal fibroblasts of the same tissue type (i.e., of lung or of skin origin). α2M was produced in culture during log-phase growth as well as at confluence. Two other plasma protease inhibitors, C1-esterase inhibitor and a substance immunologically cross-reacting with human inter-α-trypsin inhibitor, were also made by the cultured fibroblasts. Plasma protease inhibitors not detectable in culture supernatants were α1-antitrypsin, α1-antichymotrypsin, and antithrombin III.

α2-Macroglobulin in patients with obstructive lung disease, with and without α1-antitrypsin deficiency

Serum α2-macroglobulin concentrations were measured in 178 patients with emphysema and 115 control subjects of similar age and sex distribution. The study group included 59 PI type Z patients with α1-antitrypsin deficiency, five with the rare α1-antitrypsin null genotype (PI Q0 or - -), and seven with α1-antitrypsin deficiency of the rare PI types MmaltonZ or MduarteZ. Individuals with all types of -α1antitrypsin deficiency were found to have significantly increased serum concentrations of α2M (p < 0.001). These increased concentrations were associated with all types of α1-antitrypsin deficiency, not only with the PI type Z. The highest α2-macroglobulin concentrations were found in the PI Q0 patients (5 with emphysema, 2 with no lung disease), and these patients had almost no circulating α1-antitrypsin. Raised concentrations of serum α2-macroglobulin were not due to emphysema: 86 patients with emphysema, of PI type M, and the normal control subjects had similar average concentrations ofα2-macroglobulin. One control subject with an average α2-macroglobulin concentration of only 41% of normal was found.