Both normal and leukemic B lymphocytes express multiple isoforms of the human Aiolos gene.

Aiolos is a chromatin remodeling transcription regulator that plays an antiproliferative role in B lymphocyte function. In contrast to the related Ikaros factors, mammalian Aiolos has not been reported to generate splice variants. In addition, although human leukemic lymphoblasts express non-DNA-binding Ikaros isoforms with potential dominant negative effect on other interacting factors,the role of Aiolos in human lymphoid disorders has remained obscure. To address the question, why Aiolos should delineate from Ikaros in such a marked way, we have here analyzed whether also human Aiolos could generate alternate isoforms. According to the results obtained, both normal and neoplastic B lineage cells were found to express at least five novel Aiolos variants. Also structurally dominant negative variants with less than three DNA-binding domains were identified. In conclusion, given the multiplicity of also human Aiolos isoforms and thereby the evidently more intricate contribution of Aiolos to the chromatin remodeling machinery, it is suggested, that not only Ikaros, but also Aiolos could participate in a more versatile manner in the regulation of B lymphocyte function.

Primary immunodeficiency mutation databases.

Primary immunodeficiencies are intrinsic defects of immune systems. Mutations in a large number of cellular functions can lead to impaired immune responses. More than 80 primary immunodeficiencies are known to date. During the last years genes for several of these disorders have been identified. Here, mutation information for 23 genes affected in 14 immunodefects is presented. The proteins produced are employed in widely diverse functions, such as signal transduction, cell surface receptors, nucleotide metabolism, gene diversification, transcription factors, and phagocytosis. Altogether, the genetic defect of 2,140 families has been determined. Diseases with X-chromosomal origin constitute about 70% of all the cases, presumably due to full penetrance and because the single affected allele causes the phenotype. All types of mutations have been identified; missense mutations are the most common mutation type, and truncation is the most common effect on the protein level. Mutational hotspots in many disorders appear in CPG dinucleotides. The mutation data for the majority of diseases are distributed on the Internet with a special database management system, MUTbase. Despite large numbers of mutations, it has not been possible to make genotype-phenotype correlations for many of the diseases.

[Ataxia-telangiectasia surveyed in Sweden]. / Ataxia-telangiectasia kartlagd i Sverige.

Ataxia-telangiectasia (AT) is a rare autosomal recessive disease with a complex phenotype involving cerebellar degeneration, immunodeficiency, cancer risk and radiosensitivity. Our aim has been to identify Swedish AT patients in order to study the possible "Swedish phenotype" of the disease. In the 19 patients identified in Sweden we found a phenotype fairly similar to what has been described internationally, with the exception of some differences including lower cancer incidence in patients and their relatives and somewhat more pronounced immunodeficiency and concomitant susceptibility to infections.

Characterization of ATM mutations in 41 Nordic families with ataxia telangiectasia.

The Ataxia Telangiectasia Mutation (ATM) gene is mutated in the rare recessive syndrome Ataxia Telangiectasia (AT), which is characterized by cerebellar degeneration, immunodeficiency, and cancer predisposition. In this study, 41 AT families from Denmark, Finland, Norway, and Sweden were screened for ATM mutations. The protein truncation test (PTT), fragment length and heteroduplex analyses of large (0.8-1.2 kb) cDNA fragments were used. In total, 67 of 82 (82%) of the disease-causing alleles were characterized. Thirty-seven unique mutations were detected of which 25 have not previously been reported. The mutations had five different consequences for the ATM transcript: mutations affecting splicing (43%); frameshift mutations (32%); nonsense mutations (16%); small in-frame deletions (5%); and one double substitution (3%). In 28 of the probands mutations were found in both alleles, in 11 of the probands only one mutated allele was detected, and no mutations were detected in two Finnish probands. One-third of the probands (13) were homozygous, whereas the majority of the probands (26) were compound heterozygote with at least one identified allele. Ten alleles were found more than once; one Norwegian founder mutation constituted 57% of the Norwegian alleles. Several sequence variants were identified, none of them likely to be disease-causing. Some of them even involved partial skipping of exons, leading to subsequent truncation of the ATM protein.