Assignment of the structural genes for the alpha subunit of hexosaminidase A, mannosephosphate isomerase, and pyruvate kinase to the region q22-qter of human chromosome 15

Identification of a novel HEXB Mutation in an Iranian Family with suspected patient to GM2-gangliosidoses

Sandhoff disease is one of the GM2-gangliosidoses which is caused by a mutation in the HEXB preventing the breakdown of GM2-ganglioside. We report a novel HEXB variant in a family with a history of a dead girl with Sandhoff disease which was not found in controls.

Hereditary red cell enzymopathies

The hereditary red cell enzymopathies are an uncommon but important cause of chronic haemolytic anaemia. Their clinical diversity is mirrored by increasingly evident heterogeneity at the molecular level. The structure, function, and expression of the genes encoding red cell enzymes and the nature of the gene defects in the deficient state are examined.

Tay-Sachs disease screening and diagnosis: evolving technologies

Tay-Sachs disease (TSD) is an autosomal recessive, progressive, and fatal neurodegenerative disorder. Within the last 25 years, the discovery of the enzymatic basis of the disease, the deficiency of the enzyme hexosaminidase A, has made possible both enzymatic diagnosis of TSD and heterozygote identification. TSD is the first genetic condition for which a community-based heterozygote screening program was attempted with the intention of reducing the incidence of a genetic disease. In this article we review the clinical, biochemical, and molecular features of TSD as well as the development of laboratory technology that has been deployed in community genetic screening programs. We describe the assay procedures used and some of the limitations in their accuracy. We consider the impact of DNA-based technology on the process of identification of individuals carrying mutant genes associated with TSD and we discuss the social context within which genetic screening occurs.

Comparative mapping of IGHG1, IGHM, FES, and FOS in domestic cattle

The immunoglobulin genes have not been genetically characterized as thoroughly in cattle as in other mammals, particularly humans and mice. Comparative gene mapping in mammals suggests that the bovine immunoglobulin heavy chain genes, IGHG4 and IGHM might be syntenic with the FOS oncogene. Interestingly, however, when these genes were assigned to bovine syntenic groups utilizing a panel of bovine: hamster hybrid somatic cells, IGH genes were shown to be syntenic with the FES oncogene rather than FOS. In this study IGH and FES were assigned to Bos taurus chromosome 21 while FOS was assigned to chromosome 10. In addition, bovine-specific immunoglobulin-like sequences were observed in the hybrid somatic cells, and one, IGHML1, was mapped to bovine syntenic group U16. The probes used for somatic-cell mapping were also used to screen a small number of cattle of several different breeds for restriction fragment length polymorphisms. IGHG4 and IGHM were shown to be highly polymorphic, while FOS and FES were not.

Chromosomal localization of the gene for a human cytosolic thyroid hormone binding protein homologous to the subunit of pyruvate kinase, subtype M2

A cDNA for the gene that encodes a human cytosolic thyroid hormone binding protein (p58) recently has been isolated and sequenced. Analysis of the p58 sequence indicates that it is identical to the subunit of pyruvate kinase, subtype M2. By in situ hybridization, the gene for p58 was mapped to 15q24-25. This localization shows that the p58 gene is not linked to the L-type of pyruvate kinase, which is located on chromosome 1. The p58 gene was found to be activated in several forms of cancer. Current localization will permit us to assess the effect of alterations involving chromosome 15 on the structure and activity of the p58 gene in neoplasms or chromosome syndromes.

Structure and distribution of an Alu-type deletion mutation in Sandhoff disease

Sandhoff disease is a recessively inherited lysosomal storage disease resulting from a deficiency of beta-hexosaminidase activity. The enzyme occurs in two major forms, beta-hexosaminidase A, composed of an alpha- and beta-subunit and beta-hexosaminidase B, composed of two beta-subunits. Both isozyme activities are deficient in Sandhoff disease, owing to mutations of the HEXB gene encoding the common beta-subunit. We have cloned and fully characterized a deletion at the HEXB gene from fibroblasts of a patient with the infantile form of Sandhoff disease. The deletion removes approximately 16 kb of DNA including the HEXB promoter, exons 1-5 and part of intron 5. It most likely arose from recombination between two Alu sequences, with the breakpoints occurring at the midpoint between the left and right arms in each case and regenerating an intact Alu element in the deletion sequence. The deletion allele accounts for 27% of the Sandhoff mutant alleles we analyzed. Two cell lines were shown to be homozygous for the deletion and both had the infantile form of the disease. Four additional patients were compound heterozygotes with other mutations, all of whom displayed a different clinical phenotype. Finally, the mutant allele was present in different ethnic backgrounds, suggesting that it may have been subject to genetic drift.

Insulin-like growth factor I receptor gene is concordant with c-Fes protooncogene and mouse chromosome 7 in somatic cell hybrids

The insulin-like growth factor I (IGF-1) mediates the actions of pituitary growth hormone in a variety of tissues. Its receptor (IGF1R) displays considerable structural similarity to the insulin receptor. In humans, the IGF1R gene has been mapped near FES, the cellular counterpart of the feline sarcoma virus transforming gene v-fes, at the q25-q26 region of human chromosome 15 (HSA15). Here, we report the mapping of mouse Igf1r to mouse chromosome 7 (MMU7) by somatic cell hybrid analysis. This result, along with the prior assignment of the loci for mitochondrial isocitrate dehydrogenase and FES to human chromosome 15 and mouse chromosome 7, suggest a conserved autosomal synteny group on the distal long arm of HSA15 and in the center of MMU7.

Localization of the human type 5, tartrate-resistant acid phosphatase gene by in situ hybridization

We report the localization of the gene for the human type 5, tartrate-resistant, iron-containing acid phosphatase isoenzyme (HGM designation ACP5) to chromosome 15 (15q22-q26) using the technique of in situ hybridization to metaphase chromosomes. We have localized this gene using peripheral blood chromosomes obtained from both a normal male and an individual carrying an unbalanced translocation involving chromosome 15 [45,XY,-15,-18,+der(18)-t(15;18)(q13;p11)]. In addition, we have demonstrated the utility of employing a standard fluorescent staining technique (distamycin/DAPI) to an emulsion-coated, Wright-stained, and destained chromosome preparation.

Human M2-type pyruvate kinase: cDNA cloning, chromosomal assignment and expression in hepatoma

Two overlapping clones, covering the entire coding sequence of human M2-type pyruvate kinase (PK) cDNA, were isolated and sequenced. Nucleotide sequencing results showed that they contained the 109-bp 5'-untranslated region, the 1593-bp coding region and the 585-bp 3'-untranslated region. Nucleotide sequence homology was 90% and 69% with rat M2-type and L-type PK cDNA, respectively. In situ hybridization using the human M2-type PK cDNA probe disclosed that the gene for M2-type PK is located at band q22 on chromosome 15. Northern blot analysis with RNA from human hepatoma demonstrated that M2-type PK was predominantly expressed in hepatoma cells, whereas L-type PK was preferentially expressed in the non-tumor portion of the liver.

Interstitial deletion of chromosome 15: two cases

Two cases of interstitial deletion of chromosome 15 with similar clinical features are presented. In one case, assay of hexosaminidase A enabled us to confirm that the structural gene is located between 15q22 and 15q25 and that it is included in the deletion.

Human liver type pyruvate kinase: cDNA cloning and chromosomal assignment

Pyruvate kinase (PK) has four isozymes (L,R,M1,M2) that are encoded mainly by two different genes. We isolated a cDNA clone from a Japanese adult liver lambda gt10 cDNA library by using a rat liver(L)-type PK cDNA probe. One positively hybridizing clone, hlPK-1, which contained a 1,049-base pair cDNA insert, was subjected to DNA sequence analysis. Comparisons of the sequence data with the rat PK cDNAs indicated that the cDNA encoded information for the carboxyl terminal 105 amino acids of a human L-type PK and a 3' untranslated region of 734 nucleotides. Furthermore, the karyotype analysis of several human-mouse hybrid cells and Southern blot analysis of DNAs of the hybrids with a hlPK-1 indicated that the human L-type PK gene is located on chromosome 1.

Chromosome 15 anomalies and the Prader-Willi syndrome: cytogenetic analysis

The behaviour of chromosome 15 is very different from that of the other acrocentric chromosomes. The cytogenetic characteristics of rearrangements associated with Prader-Willi syndrome (PWS) are analyzed as similar rearrangements irrespective of the associated phenotype (reciprocal translocations of chromosome 15, small bisatellited additional chromosomes, Robertsonian translocations, interstitial deletions, pericentric inversions). This study suggests that: (1) The proximal ( 15q ) region and PWS seem to be indissociable ; (2) chromosome 15 has an indisputable cytogenetic originality which could be related to its histochemical properties. Chromosome 15 constitutive heterochromatin usually contains much 5-methylcytosine-rich DNA and a large amount of each of the four satellite DNAs. Furthermore the existence in the proximal ( 15q ) region of one or several palindromic sequences could be postulated to explain the great lability of this region of chromosome 15.

Genetic analysis of the 15;17 chromosome translocation associated with acute promyelocytic leukemia

Somatic cell hybrids have been constructed between a thymidine kinase-deficient mouse cell line and blood leukocytes from a patient with acute promyelocytic leukemia showing the 15q+;17q- chromosome translocation frequently associated with this disease. One hybrid contains the 15q+ translocation chromosome and very little other human material. We have shown that the c-fes oncogene, which has been mapped to chromosome 15, is not present in this hybrid and, therefore, probably is translocated to the 17q- chromosome. Analysis of the genetic markers present in this hybrid has enabled a more precise localization of the translocation breakpoints on chromosomes 15 and 17. Our experiments also have enabled an ordering and more precise mapping of several genetic markers on chromosomes 15 and 17.

A boy with ring chromosome 15 derived from a t(15q;15q) Robertsonian translocation in the mother: cytogenetic and biochemical findings

We describe a boy with a ring chromosome 15, showing the manifestations characteristic of this condition, ie, growth deficiency and unusual facial appearance with minor anomalies. The ring was derived from a t(15q;15q) chromosome of the mother, who had also had four spontaneous abortions. The respective karyotypes were 45,XX, -15,-15,+t(15q;15q) (mother) and 46,XY,-15,+r(15q;15q)mat (15q13 leads to cen leads to 15q26)(son). The ring chromosome lacked the short arms of the two translocated chromosomes 15 and was duplicated for a portion of the long arms near the centromere, probably cen leads to q13. Data from enzyme assays suggest that this duplicated region carries the alpha-mannosidase gene.

Chromosomal assignment of the human homologues of feline sarcoma virus and avian myeloblastosis virus onc genes

Retroviral transforming genes, v-onc genes, are derived from normal cellular sequences that are called cellular onc (c-onc) genes. DNA from mouse-human somatic cell hybrids that have selectively lost human chromosomes was used in Southern blots to map the chromosomal location of two human onc genes. Cloned human homologues of retroviral onc genes were used as probes. Because the human c-fes gene, which is homologous to feline sarcoma virus, segregates concordantly with human chromosome 15, and the human c-myb gene, which is homologous to avian myeloblastosis virus onc genes, segregates concordantly with human chromosome 6, we have assigned the c-fes and the c-myb genes to human chromosomes 15 and 6, respectively. Nonrandom chromosomal defects involving these human chromosomes have been observed in neoplasms. These studies should be valuable in determining whether specific rearrangements involving these chromosomes result in the abnormal expression of these onc genes in human malignancies.

Biochemistry and genetics of gangliosidoses

The gangliosidoses comprise an-ever increasing number of biochemically and phenotypically variant diseases. In most of them an autosomal recessive inherited deficiency of a lysosomal hydrolase results in the fatal accumulation of glucolipids (predominantly in the nervous tissue) and of oligosaccharides. The structure, substrate specificity, immunological properties of and genetic studies on the relevant glycosidases, ganglioside GM1 beta-galactosidase and beta-hexosaminidase isoenzymes, are reviewed in this paper. Contrary to general expectation, only a poor correlation is observed between the severity of the disease and residual activity of the defective enzyme when measured with synthetic or natural substrates in the presence of detergents. For the understanding of variant diseases and for their pre- and postnatal diagnosis, the necessity of studying the substrate specificity of normal and mutated enzymes under conditions similar to the in vivo situation, e.g., with natural substrates in the presence of appropriate activator proteins, is stressed. The possibility that detergents may have adverse affects on the substrate specificity of the enzymes is discussed for the beta-hexosaminidases. The significance of activator proteins for the proper interaction of lipid substrates and water-soluble hydrolases is illustrated by the fatal glycolipid storage resulting from an activator protein deficiency in the AB variant of GM2-gangliosidosis. Recent somatic complementation studies have revealed the existence of a presumably post-translational modification factor necessary for the expression of ganglioside GM1 beta-galactosidase activity. This factor is deficient in a group of variants of GM1-glangliosidosis. Among the possible reasons for the variability of enzyme activity levels in heterozygotes and patients, allelic mutations, formation of hybrid enzymes, and the existence of patients as compound heterozygotes are discussed. All these may result in the production of mutant enzymes with an altered specificity for a variety of natural substrates.