Primary adhalinopathy: a common cause of autosomal recessive muscular dystrophy of variable severity.

Marked deficiency of muscle adhalin, a 50 kDa sarcolemmal dystrophin-associated glycoprotein, has been reported in severe childhood autosomal recessive muscular dystrophy (SCARMD). This is a Duchenne-like disease affecting both males and females first described in Tunisian families. Adhalin deficiency has been found in SCARMD patients from North Africa Europe, Brazil, Japan and North America (SLR & KPC, unpublished data). The disease was initially linked to an unidentified gene on chromosome 13 in families from North Africa, and to the adhalin gene itself on chromosome 17q in one French family in which missense mutations were identified. Thus there are two kinds of myopathies with adhalin deficiency: one with a primary defect of adhalin (primary adhalinopathies), and one in which absence of adhalin is secondary to a separate gene defect on chromosome 13. We have examined the importance of primary adhalinopathies among myopathies with adhalin deficiency, and describe several additional mutations (null and missense) in the adhalin gene in 10 new families from Europe and North Africa. Disease severity varies in age of onset and rate of progression, and patients with null mutations are the most severely affected.

Severe hypofibrinogenemia associated with bilateral ischemic necrosis of toes and fingers.

Severe hypofibrinogenemia was found in an Algerian woman who, since the age of 37 years, suffered three different episodes of ischemic necrosis of the toes and fingers leading to amputation of the toes and surgical removal of necrotic tissue (necretomy). No anti-fibrinogen antibody was present. The deficiency appeared to be due to severe congenital hypofibrinogenemia since the fibrinogen level remained at the same low level over a long period, without any abnormality of other coagulation proteins. The thrombotic events may be explained by the increased thrombin generation observed in the patient's plasma, due to the lack of thrombin adsorption onto a fibrin net.

Quantitative variations of red-cell cytochrome b5 reductase (NADH-methemoglobin-reductase) in the Algerian population: evidence for defective alleles.

A striking proportion of Algerian subjects was reported among patients with congenital recessive methemoglobinemia due to cytochrome b5 reductase deficiency (Kaplan et al. 1979). A population survey was carried out in red blood cells from 1000 Algerian subjects. In 16 subjects, the cytochrome b2 reductase activity was diminished by 50%. Family studies indicated the presence of a defective allele with an overall gene frequency of 0.008. Immunologically cross-reacting material was found in red cells with low cytochrome b5 reductase activity. Leukocytes exhibited normal levels of enzyme in some families and low levels in others suggesting that at least two different deficient alleles at the DIA1 locus were present in the Algerian population. A higher prevalence of the deficient allele(s) was found in subjects of Kabyle origin.

Characterization of weak alleles at the DIA1 locus (Mustapha 1, Mustapha 2, and Mustapha 3) in the Algerian population.

One percent of the Algerian population carries a weak allele at the DIA1 locus, responsible for a 50% decrease of red cell soluble cytochrome b5 reductase activity. Quantitative abnormalities of the soluble and the membrane-bound enzyme have been investigated in the red cells and in the leukocytes of seven subjects considered to be heterozygous at the DIA1 locus. Conventional electrophoretic or isoelectrophoretic studies did not show any qualitative abnormality. However, continuous titration obtained by combined IEF-electrophoresis displayed in five out of seven subjects a discrete abnormal line on the titration curve compatible with an Arg leads to His substitution. In fact, at least three types of weak alleles could be defined by combining the qualitative and quantitative results obtained with the erythrocyte (soluble and membrane-bound) and leukocyte enzyme. We call these subgroups DIA Mustapha1, DIA Mustapha2, and DIA Mustapha3.

Endogenous proteolysis of membrane-bound red cell cytochrome-b5 reductase in adults and newborns: its possible relevance to the generation of the soluble "methemoglobin reductase".

The problem of the low activity of so-called methemoglobin reductase in red cells from newborns was reinvestigated in view of our current knowledge of this enzyme, i.e., (1) its being cytochrome-b5 reductase and (2) its presence in two forms: soluble and membrane-bound. We found that red cells from cord blood and newborns exhibited a 50% decrease of soluble cytochrome-b5 reductase activity, whereas membrane-bound activity was in the adult range. Ghosts from these cells possessed diminished ability to solubilize membrane-bound cytochrome-b5 reductase in the course of in vitro auto-incubation. This autosolubilizing ability increased with age and reached adult level concomitantly with soluble cytochrome-b5 reductase activity at 6 mo. We conclude that the relative deficiency of soluble cytochrome-b5 reductase observed at birth is due to diminished post-translational processing of the membrane-bound enzyme during erythropoiesis of fetal cells. This processing is calcium-dependent related to calmodulin.

A linkage and physical map of chromosome 22, and some applications to gene mapping.

A genetic map of human chromosome 22 has been derived from physical assignments and multilocus linkage analysis. It consists of the loci for the immunoglobulin lambda light-chain variable (IGLV) and immunoglobulin lambda light-chain constant (IGLC) regions, myoglobin (MB), the sis proto-oncogene (SIS), and an arbitrary probe (D22S1). The first RFLPs at the loci for SIS, IGLV, and MB are described. The most likely gene order on the basis of multilocus analysis was cen-(IGLV-IGLC)-D22S1-MB-SIS. This map provides further evidence for localization of the P1 polymorphism of the P blood group to chromosome 22, close to the SIS locus. Analysis of families segregating recessive congenital methemoglobinemia (RCM), a disease in which the cytochrome b5 reductase is defective, as well as of families with cases of hereditary low levels of cytochrome b5 reductase activity, confirmed that the locus responsible for RCM is on chromosome 22. Biochemical studies had already suggested that mutation at the cytochrome b5 reductase locus (DIA1) is responsible for RCM. We found no evidence of genetic heterogeneity between the families segregating RCM and the families exhibiting cases of low cytochrome b5 reductase activity. Linkage analysis indicated that the most probable location of DIA1 lies between MB and SIS.

Prenatal diagnosis of congenital enzymopenic methaemoglobinaemia with mental retardation due to generalized cytochrome b5 reductase deficiency: first report of two cases.

Prenatal diagnosis of congential enzymopenic methaemoglobinaemia (CEM) with mental retardation was performed in two fetuses at risk for generalized NADH-cytochrome b5 reductase deficiency. In the first case the enzyme activity of cultured amniotic cells was in the heterozygous to normal range. The mother delivered a normal baby with normal enzyme activity in cord blood cells. In the second case, the amniotic cells were almost completely enzyme deficient. The pregnancy was terminated, and the diagnosis of homozygous NADH-cytochrome b5 reductase deficiency was confirmed in cord blood cells, in several different tissues and in cultured fibroblasts from the aborted fetus.

At least five polymorphic mutants account for the prevalence of glucose-6-phosphate dehydrogenase deficiency in Algeria.

The electrophoretic mobility and level of enzyme activity of glucose-6-phosphate dehydrogenase (G6PD) was established in 100 unrelated Algerian males with G6PD deficiency. DNA from these subjects was analysed for the presence of certain known G6PD mutations by the appropriate restriction enzyme digestion of fragments amplified by the polymerase chain reaction. Where the mutation could not be identified in this way, the samples were subjected to single-strand conformation polymorphism analysis and abnormal fragments were sequenced. In this way, eight different mutations have been identified, of which five are polymorphic and account for 92% of the samples. The most common variants are G6PD A- (46%) and G6PD Mediterranean (23%), both of which were associated with favism. A new polymorphic variant, G6PD Aures, has been identified during the course of this study, whereas another, G6PD Santamaria, has now been established as a polymorphic variant (11%). Thus, G6PD deficiency in Algeria is heterogeneous, suggesting that there has been significant gene flow, both from sub-Saharan Africa and from other parts of the Mediterranean.

Investigation of factor VIII:C gene restriction fragment length polymorphisms and search for deletions in hemophiliac subjects in Algeria.

The frequency of alleles for intragenic (intron 17 and intron 25) and extragenic (DXS15 and DXS52) F8C RFLPs was investigated in the Algerian population. Altogether 287 X chromosomes (97 males and 95 females) were studied. The allele frequencies found with the two intragenic F8C RFLPs were not substantially different from those reported in a Mediterranean population. At the highly polymorphic extragenic DXS52 locus the distribution in Algeria differed from that found in France. A new allele (14 kb), called 1 DZ, was found in 3.1% of the chromosomes. Fifty-one families with hemophilia A were studied with the same probes (374 subjects). Of the females, 94% were informative for at least one intra- or extragenic RFLP. Two recombinations were found between DXS52 and F8C, of which one occurred between the DXS15, DXS52 block and F8C, indicating that the two anonymous loci are on the same side of the F8C gene. Only two obvious gene deletions were observed in 73 unrelated hemophiliacs: one encompassed exons 14-22 (about 4.3 kb of cDNA and 36 kb of genomic DNA); the other removed the last exon (exon 26, representing 2 kb of cDNA).