Basic defect in the expression of adenosine deaminase in ADA- SCID disease investigated through the cells of an obligate heterozygote

Prospects and challenges of reprogrammed cells in hematology and oncology

Induced pluripotent stem cells (iPSCs) have emerged as a promising basis for modeling pediatric genetic disorders, allowing the derivation, study, and genetic correction of disease and patient-specific cell lines in vitro. Similar to embryonic stem cells (ESCs), iPSCs are capable of unlimited in vitro expansion and derivation of many cell types, including hematopoietic stem cells (HSCs). These may not only allow large scale screenings to develop therapeutic compounds, but also help to overcome cross-species barriers of genetically engineered animal models, which do not adequately recapitulate the associated human phenotype. Here, we review the current state and emerging developments of iPSC research, which can be exploited as a tool in modeling pediatric hematopoietic disorders and could lead to new clinical applications in gene and cell therapies.

Adenosine deaminase gene expression is regulated posttranscriptionally in the nucleus

The housekeeping enzyme adenosine deaminase (ADA) shows a large variation in tissue-specific expression ranging from 1 Iu in red blood cells to 880 Iu in thymocytes. We investigated the acute lymphocytic leukemic cell line Molt-4 (660 Iu ADA/g protein) and the promyelocytic cell line HL-60 (38 Iu ADA/g protein) as a model system to determine the levels at which the tissue-specific expression of ADA is regulated. From our results it can be concluded that the almost 20-fold difference in ADA expression between Molt-4 and HL-60 is the result of differences in the post-transcriptional processing and/or stability of ADA pre-mRNA within the nucleus.

Severe combined immune deficiency due to a homozygous 3.2-kb deletion spanning the promoter and first exon of the adenosine deaminase gene

We have investigated the structural gene for adenosine deaminase (ADA) in a female infant with ADA deficiency associated severe combined immune deficiency (ADA-SCID) disease and her family by DNA restriction-fragment-length analysis. In this family a new ADA-specific restriction-fragment-length variant was detected, which involves a 3.2-kb deletion spanning the ADA promoter as well as the first exon. It was found that the patient, who was born to a consanguineous couple, was homozygous and both her parents and her brother were heterozygous for the deletion. No ADA-specific mRNA could be detected by hybridization in fibroblasts derived from this patient. Thus the patient was established to be homozygous for a true null ADA allele. In the light of the apparently normal development of most tissues except the lymphoid tissue the above finding directly questions the classification of ADA as a 'housekeeping' enzyme.

Adenosine deaminase mRNA expression is regulated posttranscriptionally during differentiation of HL-60 cells

The expression of the enzyme adenosine deaminase (ADA) decreases in the course of the differentiation of the human promyelocytic leukemic cell line HL-60, dependent on the pathway chosen. Differentiation to monocytes as induced by the phorbol ester TPA leads to a 50% reduction of enzyme activity. Induction to myeloid cells as induced by DMSO has a slower and less extensive (75% remaining activity) effect. The reduction in ADA enzymatic activity is preceded by a 5-10 fold reduction in ADA-specific mRNA which is also more rapid during TPA-induced differentiation. In contrast, c-myc mRNA expression is both in TPA- and DMSO-induced differentiation reduced to less then 5% of its initial level within 4h. Nuclear run-on analysis revealed that the reduction of c-myc-mRNA expression during both TPA- and DMSO-induced differentiation could be ascribed to the abolition of transcription of the third exon, whereas no change in the transcription of the first exon could be observed. No change could be detected in the rate of transcription of either the 5' and 3' parts of the ADA gene during TPA- and DMSO-induced differentiation, indicating that the expression of the ADA gene in HL-60 is controlled at a posttranscriptional level.

Assignment of the human tissue-type plasminogen activator gene (PLAT) to chromosome 8

Using 1.2kb 3'-terminal Pst-I fragment of a full length tissue-type plasminogen activator (t-PA) cDNA clone (ptPA-8FL) and a set of rodent human somatic cell hybrids, the corresponding human gene PLAT was localized on chromosome 8.

Complete structure of the alpha B-crystallin gene: conservation of the exon-intron distribution in the two nonlinked alpha-crystallin genes

We isolated bovine complementary DNA clones for the alpha A- and alpha B-crystallin subunits. The alpha B cDNA clone was used to isolate an alpha B-crystallin gene. This gene, derived from hamster, occurs as a single copy in the genome and is 3.2 kilobases long. The coding sequences are spread on three exons with a total length of 709 nucleotides. The exon-intron distribution of the hamster alpha B-crystallin gene is similar to that of the alpha A-crystallin gene except for the 69 nucleotides that specify the 23 "insert" residues of the alpha AIns chain by means of differential splicing. The 3' noncoding region of the alpha B mRNA (140 bases), which is short compared with the alpha A mRNA (520 bases), shows a remarkable homology between calf and hamster. Both alpha-crystallin cDNA clones have been used to assign the chromosomal location of the corresponding human genes with the aid of somatic cell hybrids. It is shown that the single-copy alpha A- and alpha B-crystallin genes are located on different chromosomes.

The human desmin and vimentin genes are located on different chromosomes

We have used somatic cell hybrids of Chinese hamster X man and mouse X man to localize the genes (des and vim) encoding the intermediate filaments desmin and vimentin in the human genome. Southern blots of DNA prepared from each cell line were screened with hamster cDNA probes specific for des and vim genes, respectively. The single-copy human des gene is located on chromosome 2, and the single-copy human vim gene is assigned to chromosome 10. Partial restriction maps of the two human genomic loci are presented. A possible correlation of the des locus with several reported hereditary myopathies is discussed.

Localization of the polymorphic human calcitonin gene on chromosome 11

A molecular probe containing a 584 base pairs sequence corresponding to part of the human calcitonin mRNA was used for the chromosomal assignment of the calcitonin gene. Restriction endonuclease analysis of DNA from human-Chinese hamster and human-mouse somatic cell hybrids, including some containing a translocation of human chromosomes, placed the calcitonin gene in the p14----qter region of chromosome 11. Analysis of human DNA showed that the calcitonin gene has a polymorphic site for restriction endonuclease TaqI.

Isolation of cDNA clones for human adenosine deaminase

Clones encoding human adenosine deaminase (ADA) were isolated from a cDNA library made from the lymphoblastoid cell line MOLT-4. The isolation procedure was based on the selection of clones hybridizing with a radioactive probe complementary to an RNA preparation, which had been highly enriched in ADA-specific mRNA. The latter RNA preparation was obtained by size-fractionating MOLT-4 RNA and selecting fractions that were translatable into ADA. The assay for the presence of ADA in the in vitro translation products, was based on immunoprecipitation with a specific anti-ADA serum. The antiserum used was shown to precipitate a 42-kDal protein with the properties of ADA. Positive clones were further screened by means of hybrid-released in vitro translation assays. Two clones were obtained which were able to select mRNA that could be translated into a 42-kDal protein immunoprecipitable with the ADA-antiserum. By use of Southern blots containing DNA from somatic cell hybrids, one of these ADA cDNA clones was assigned to the human chromosome 20 known to contain the ADA gene.

Basic defect in the expression of adenosine deaminase in ADA-SCID disease. II. Deficiency of ADA-CRM detected in heterozygote human-Chinese hamster cell hybrids

A specific competitive radioimmunoassay (RIA) was employed to quantify human adenosine deaminase molecules produced in human-Chinese hamster somatic cell hybrids. Studies on a set of hybrids in which the normal and aberrant expressions of adenosine deaminase (assigned earlier to human chromosome 20) were segregating, have demonstrated that in the patient with ADA-SCID disease reported by Herbschleb-Voogt et al. (1981 a), the deficiency of ADA activity was associated with a comparable deficiency of adenosine deaminase specific immuno-crossreacting material (ADA-CRM).

Purine metabolism in relation to leukemia and lymphoid cell differentiation

A number of inborn errors of purine metabolism have been associated with immunodeficiency diseases. From studies to the possible mechanism(s) leading to the defects in the immune system, it appeared that the accumulation of deoxyATP and deoxyGTP and the subsequent inhibition of ribonucleotide reductase played an important role. The inhibition of methylation pathways through the accumulation of s-adenosylmethionine seems to be a second valid concept. The amount to which certain subtypes of lymphoid cells were affected by the enzyme deficiencies was strongly related to the enzymatic make-up of the cells. Lymphoid cells from different maturation stages could be affected in a specific way, depending on the different enzyme activities of these cells. Studies on human lymphoblastic leukemias showed that, related to the immunological subtype, the different leukemias could be characterized by a different enzymatic make-up. In this paper we discuss the possibilities for a specific enzyme directed chemotherapy, directed against specific subtypes of human lymphoblastic leukemias. Experimental evidence indicates that for example the adenosine deaminase inhibitor 2'deoxycoformycin can be used as a specific drug against acute lymphoblastic leukemia with the T cell phenotype.

Assignment of adenosine deaminase complexing protein (ADCP) gene(s) to human chromosome 2 in rodent-human somatic cell hybrids

The experiments reported in this paper indicate that the expression of human adenosine deaminase complexing protein (ADCP) in the human-rodent somatic cell hybrids is influenced by the state of confluency of the cells and the background rodent genome. Thus, the complement of the L-cell derived A9 or B82 mouse parent apparently prevents the expression of human ADCP in the interspecific somatic cell hybrids. In the a3, E36, or RAG hybrids the human ADCP expression was not prevented by the rodent genome and was found to be proportional to the degree of confluency of the cell in the culture as in the case of primary human fibroblasts. An analysis of human chromosomes, chromosome specific enzyme markers, and ADCP in a panel of rodent-human somatic cell hybrids optimally maintained and harvested at full confluency has shown that the expression of human ADCP in the mouse (RAG)-human as well as in the hamster (E36 or a3)-human hybrids is determined by a gene(s) in human chromosome 2 and that neither chromosome 6 nor any other of the chromosomes of man carry any gene(s) involved in the formation of human ADCP at least in the Chinese hamster-human hybrids. A series of rodent-human hybrid clones exhibiting a mitotic separation of IDH1 and MDH1 indicated that ADCP is most probably situated between corresponding loci in human chromosome 2.