Spot-blot analysis of sorted chromosomes assigns a fructose intolerance disease locus to chromosome 9

Recent advances in the pathogenesis of hereditary fructose intolerance: implications for its treatment and the understanding of fructose-induced non-alcoholic fatty liver disease

Hereditary fructose intolerance (HFI) is a rare inborn disease characterized by a deficiency in aldolase B, which catalyzes the cleavage of fructose 1,6-bisphosphate and fructose 1-phosphate (Fru 1P) to triose molecules. In patients with HFI, ingestion of fructose results in accumulation of Fru 1P and depletion of ATP, which are believed to cause symptoms, such as nausea, vomiting, hypoglycemia, and liver and kidney failure. These sequelae can be prevented by a fructose-restricted diet. Recent studies in aldolase B-deficient mice and HFI patients have provided more insight into the pathogenesis of HFI, in particular the liver phenotype. Both aldolase B-deficient mice (fed a very low fructose diet) and HFI patients (treated with a fructose-restricted diet) displayed greater intrahepatic fat content when compared to controls. The liver phenotype in aldolase B-deficient mice was prevented by reduction in intrahepatic Fru 1P concentrations by crossing these mice with mice deficient for ketohexokinase, the enzyme that catalyzes the synthesis of Fru 1P. These new findings not only provide a potential novel treatment for HFI, but lend insight into the pathogenesis of fructose-induced non-alcoholic fatty liver disease (NAFLD), which has raised to epidemic proportions in Western society. This narrative review summarizes the most recent advances in the pathogenesis of HFI and discusses the implications for the understanding and treatment of fructose-induced NAFLD.

Aldolase B mutations and prevalence of hereditary fructose intolerance in a Polish population

We studied 28 Polish hereditary fructose intolerant (HFI) patients (26 unrelated) by direct sequencing of the ALDOB coding region/splice sites. Eight different mutations were found including two novel ones (each found in two unrelated individuals): c.250delC (frameshift) and c.522 C > G (p.Y174X). The most frequent mutation c.448 G > C (p.A150P, 67% of chromosomes) was screened for in a group of 1049 randomly selected unrelated individuals. Eight (1:131) carriers were found allowing to estimate the HFI prevalence in Poland as 1:31,000.

Hereditary fructose intolerance

Hereditary fructose intolerance (HFI, OMIM 22960), caused by catalytic deficiency of aldolase B (fructose-1,6-bisphosphate aldolase, EC 4.1.2.13), is a recessively inherited condition in which affected homozygotes develop hypoglycaemic and severe abdominal symptoms after taking foods containing fructose and cognate sugars. Continued ingestion of noxious sugars leads to hepatic and renal injury and growth retardation; parenteral administration of fructose or sorbitol may be fatal. Direct detection of a few mutations in the human aldolase B gene on chromosome 9q facilitates the genetic diagnosis of HFI in many symptomatic patients. The severity of the disease phenotype appears to be independent of the nature of the aldolase B gene mutations so far identified. It appears that hitherto there has been little, if any, selection against mutant aldolase B alleles in the population: in the UK, approximately 1.3% of neonates harbour one copy of the prevalent A149P disease allele. The ascendance of sugar as a major dietary nutrient, especially in western societies, may account for the increasing recognition of HFI as a nutritional disease and has shown the prevalence of mutant aldolase B genes in the general population. The severity of clinical expression correlates well with the immediate nutritional environment, age, culture, and eating habits of affected subjects. Here we review the biochemical, genetic, and molecular basis of human aldolase B deficiency in HFI, a disorder which responds to dietary therapy and in which the principal manifestations of disease are thus preventable.

Genomic sequences of aldolase C (Zebrin II) direct lacZ expression exclusively in non-neuronal cells of transgenic mice

Aldolase C is regarded as the brain-specific form of fructose-1, 6-bisphosphate aldolase whereas aldolase A is regarded as muscle-specific. In situ hybridization of mouse central nervous system using isozyme-specific probes revealed that aldolase A and C are expressed in complementary cell types. With the exception of cerebellar Purkinje cells, aldolase A mRNA is found in neurons; aldolase C message is detected in astrocytes, some cells of the pia mater, and Purkinje cells. We isolated aldolase C genomic clones that span the entire protein coding region from 1.5 kb 5' to the transcription start site to 0.5 kb 3' to the end of the last exon. The bacterial gene, lacZ, was inserted in two different locations and the constructs tested in transgenic mice. When the protein coding sequences were replaced with lacZ, three of five transgenic lines expressed beta-galactosidase only in cells of the pia mater; one line also expressed in astrocyte-like cells. When lacZ was inserted into the final exon (and all structural gene sequences were retained) transgene expression was observed in astrocytes in all regions of the central nervous system as well as in pial cells. Thus, with the exception of Purkinje cell expression, the behavior of the full-length transgene mimics the endogenous aldolase C gene. The results with the shorter transgene suggest that additional enhancer elements exist within the intragenic sequences. The absence of Purkinje cell staining suggests that the cis elements required for this expression must be located outside of the sequences used in this study.

Molecular basis of hereditary fructose intolerance: mutations and polymorphisms in the human aldolase B gene

Mutations in the human aldolase B gene that result in hereditary fructose intolerance have been characterized extensively. Although the majority of subjects have been from northern Europe, subjects from other geographical regions and ethnic groups have been identified. At present 21 mutations have been reported; 15 of these are single base substitutions, resulting in nine amino acid replacements, four nonsense codons, and two putative splicing defects. Two large deletions, two four-base deletions, a single-base deletion, and a seven-base deletion/one-base insertion have been found. This last mutation leads to a defect in splicing and it is likely that one of the small deletions does as well. Regions of the enzyme where mutations have been observed recurrently are encoded by exons 5 and 9. Indeed, the three most common mutations are found in these exons. Two of these prevalent HFI mutations arose from a common ancestor and spread throughout the population by genetic drift. This finding was based on linkage to two sequence polymorphisms, which are among very few informative polymorphic markers that have been identified within the aldolase B gene. Because of the prevalence of a few HFI alleles, and the recent advances in molecular methods for identifying and screening for mutation, the diagnosis of HFI by molecular screening methods should become routine. These molecular diagnostic methods will be extremely beneficial for this often difficult to diagnose and sometimes fatal disease.

The human glutamate receptor cDNA GluR1: cloning, sequencing, expression and localization to chromosome 5

The rat glutamate receptor is a 907 amino acid transmembrane protein. Using the rat GluR1 cDNA as a probe, we have isolated cDNA clones from a human hippocampal cDNA library. Sequence of a full length cDNA clone revealed 98.2% and 89.4% identity to the rat sequence at the amino acid and nucleotide levels respectively. The human cDNA clone detected an RNA transcript in human cerebral cortex, hippocampus and cerebellum, similar to that seen in rat. In situ hybridization experiments showed that human GluR1 mRNA is present in granule and pyramidal cells in the hippocampal formation and that there is no apparent difference of distribution between control patient and patient with Alzheimer's disease. Dot blot analysis of flow-sorted human chromosomes showed that the GluR1 gene maps to chromosome 5.

Gene mapping of human bilirubin UDP-glucuronosyl transferase on 1q21-q23 by a cell sorter and in situ hybridization

The human liver bilirubin UDP-glucuronosyl transferase (bilirubin UDPGT) [EC 2.4.1.17] is responsible for the enzyme deficiency in Crigler-Najjar syndrome and/or Gilbert's syndrome. The UDPGT, former shows severe jaundice resulted from a complete absence of bilirubin while the latter has a mild manifestation due to a reduction of the enzyme activity. The gene locus of bilirubin UDPGT was mapped to chromosome 1 by spot-blot hybridization using a cell-sorter, and its regional locus was assigned to 1q21-q23 by high resolution in situ hybridization.

Anti-kinetochore staining for single laser, bivariate flow sorting of Indian muntjac chromosomes

Flow cytometric chromosome sorting typically relies upon dual-laser, bivariate analysis after staining with two different base pair-specific dyes for resolution of chromosomes with similar DNA content. The availability of FITC-conjugated antibodies offers the possibility of single-laser bivariate analysis when combined with propidium iodide (PI) DNA staining, but requires exploitable antigenic differences between chromosomes of interest. A technique was developed for indirect immunofluorescent anti-kinetochore staining of Indian muntjac chromosomes in suspension. Primary antibody binding within permeabilized whole cells minimized centrifugation-induced loss of chromosomal integrity. Subsequent FITC-conjugated second antibody binding was not affected by concurrent PI-counterstaining. Anti-kinetochore staining facilitated resolution of chromosomes No. 2 and X, which formed a doublet peak upon univariate DNA content analysis, as well as recognition of the Y2 peak which was indistinguishable from debris by univariate analysis. The technique allowed greater than 90% purification of each Indian muntjac chromosome.

Rare McArdle disease locus polymorphic site on 11q13 contains CpG sequence

When probes throughout the McArdle disease (myophosphorylase) gene region were used to search for DNA polymorphisms, only an MspI polymorphism was found in 94 enzyme-probe combinations. Along with an insertion/deletion polymorphism more 3' to the gene locus, these polymorphisms will be informative in 75% of at-risk patients. These results contrast strikingly to the six polymorphic sites detected in 15 enzyme-probe combinations in the homologous Her's disease (liver phosphorylase) gene region. This single MspI polymorphic site includes a CpG sequence of known increased mutability suggesting that DNA regions with rare polymorphisms will have most polymorphic sites at sequences with enhanced mutability. Fluorescence in situ hybridization sublocalized this gene to proximal band 11q13, establishing a point of cross-reference between the physical and genetic maps.

Somatic mosaicism at the Duchenne locus

Results of testing a family for carrier status and prenatal diagnosis for Duchenne muscular dystrophy (DMD) are best explained by somatic mosaicism in the maternal grandfather. This genetic situation was identified using segregation analysis of intragenic DNA polymorphisms, a serum creatine phosphokinase assay, and physical examination of the patients. This event at the DMD locus represents one more potential source of error in carrier testing and prenatal diagnosis.

Isolation of giant DNA fragments from flow-sorted human chromosomes

We have established a method using a conventional cell sorter equipped with a single argon laser to sort intact human chromosomes that can be used as a source for the production of giant DNA fragments. Various improvements were made to both the equipment and sorting method to enhance the sorting resolution and avoid destruction of chromosomal DNA. Using this improved method chromosomes 21 and 22 were sorted from the B-lymphoblastoid line GM00130B, digested with the rare cutting restriction endonuclease NotI, and analyzed by pulsed field gel electrophoresis followed by Southern hybridization using the Alu repetitive sequence as a probe. More than 25 discrete NotI giant DNA fragments ranging from 50 kb to longer than 2.5 Mb were separated and the size distribution pattern was unique for each chromosome, indicating successful sorting of intact chromosomes. The cumulative size of these Alu-positive NotI DNA fragments were 22.7 Mb and 25.5 Mb for chromosomes 21 and 22, respectively. These values are 47% and 49% of the estimated size of chromosomes 21 (48 Mb) and 22 (52 Mb).

Detection of mRNA in flow-sorted cells

Cells were sorted onto nitrocellulose filters which were saturated with a lysing cocktail designed to preferentially immobilize cellular mRNA. After washing, these filters were incubated with 32P-labeled specific DNA probes. We used the phorbol ester/lipopolysaccharide (PMA + LPS) co-induction of IL-1 mRNA and CD13 expression in U937 cells to demonstrate the specificity of the technique. In addition we used the abundant expression of c-fos in U937 to demonstrate linearity. IL-1 beta mRNA is readily discernable autoradiographically from as few as 5,000 PMA + LPS-induced cells sorted onto a filter. With liquid scintillation counting we demonstrate good linearity of the c-fos quantitation over the range of 1,000 cells to 60,000 cells per filter target. The technique is easily adapted to any sorting flow cytometer and should prove useful to help correlate any flow cytometric cell phenotype with specific mRNA abundance.

McArdle's disease: biochemical and molecular genetic studies

We have analyzed muscle biopsy specimens from 48 patients with biochemically proven phosphorylase deficiency (McArdle's disease) by sodium dodecylsulphate polyacrylamide gel electrophoresis (SDS-PAGE), immunoblotting, and immunotitration (enzyme-linked immunosorbent assay [ELISA]). Thirty-five of the 42 patients studied by SDS-PAGE and immunoblot, and 41 of the 48 patients studied by ELISA had no detectable enzyme protein. Six patients had markedly decreased phosphorylase protein by all three assays, and only 1 patient had a normal amount of protein. No apparent correlation existed between the presence or absence of enzyme protein and the clinical presentation or muscle glycogen concentration. Northern analysis was performed on muscle RNA in 4 patients: messenger RNA was normal in 2, abnormally short in 1, and absent in the fourth, indicating heterogeneity of the molecular lesion in McArdle's disease.

Assignment of human gene encoding testis-specific lactate dehydrogenase C to chromosome 11, region p14.3-p15.5

The human gene coding for lactate dehydrogenase C (LDHC), a testis-specific isozyme, has been assigned to a refined region of chromosome 11, p14.3-p15.5, in which the lactate dehydrogenase A gene (LDHA) also resides, by using somatic cell hybrids and in situ chromosome hybridization. This assignment clearly indicates the close physical proximity of the LDHC and LDHA genes and supports the evolutionary closeness of these two isozymes.

Identification of a human gene (HCK) that encodes a protein-tyrosine kinase and is expressed in hemopoietic cells

We have isolated cDNAs representing a previously unrecognized human gene that apparently encodes a protein-tyrosine kinase. We have designated the gene as HCK (hemopoietic cell kinase) because its expression is prominent in the lymphoid and myeloid lineages of hemopoiesis. Expression in granulocytic and monocytic leukemia cells increases after the cells have been induced to differentiate. The 57-kilodalton protein encoded by HCK resembles the product of the proto-oncogene c-src and is therefore likely to be a peripheral membrane protein. HCK is located on human chromosome 20 at bands q11-12, a region that is affected by interstitial deletions in some acute myeloid leukemias and myeloproliferative disorders. Our findings add to the diversity of protein-tyrosine kinases that may serve specialized functions in hemopoietic cells, and they raise the possibility that damage to HCK may contribute to the pathogenesis of some human leukemias.

Identification of a human gene (HCK) that encodes a protein-tyrosine kinase and is expressed in hemopoietic cells

We have isolated cDNAs representing a previously unrecognized human gene that apparently encodes a protein-tyrosine kinase. We have designated the gene as HCK (hemopoietic cell kinase) because its expression is prominent in the lymphoid and myeloid lineages of hemopoiesis. Expression in granulocytic and monocytic leukemia cells increases after the cells have been induced to differentiate. The 57-kilodalton protein encoded by HCK resembles the product of the proto-oncogene c-src and is therefore likely to be a peripheral membrane protein. HCK is located on human chromosome 20 at bands q11-12, a region that is affected by interstitial deletions in some acute myeloid leukemias and myeloproliferative disorders. Our findings add to the diversity of protein-tyrosine kinases that may serve specialized functions in hemopoietic cells, and they raise the possibility that damage to HCK may contribute to the pathogenesis of some human leukemias.

The gene for human chromogranin A (CgA) is located on chromosome 14

Chromogranin A (CgA) is a protein that is present in most neuroendocrine tissues and is co-secreted with their resident hormones. We have assigned the CgA gene to human chromosome 14 by hybridization of a CgA cDNA probe cloned from a cDNA library of human medullary thyroid carcinoma cells to spots of individual human chromosomes flow-sorted onto nitrocellulose filters. Southern analysis of human genomic DNA with the same probe revealed only 1-3 restriction bands. These studies indicate that the CgA gene is probably single copy and not a member of a dispersed, multigene family. The CgA gene is not co-localized with the genes of any of the CgA-associated hormones.

Design and application of a versatile triple-laser cell and chromosome sorter

A high-resolution triple-laser sorter was designed and constructed to provide flexible switchover and high-resolution sorting of cells or chromosomes with any combination of one, two, or three lasers. These features provide a central facility instrument that currently serves multiple users and analyzes different stain combinations with minimal switchover effort between experiments. Improved optics and mounts that focus the three laser beams independently are able to resolve beads and chromosomes better than our previously reported dual-laser sorter. An improved signal collection unit with electronically controlled reference positions can be focused more quickly and precisely for any signal combination. A removable dye laser extends the range of usable fluorochrome labels. A rapid sheath switchover permits sorting of sterile cells and sterile chromosomes sequentially without additional sterilization or reservoir sheath change. Improved dual-laser chromosome resolution is at least as good, analyzing 8,000 chromosomes/s, compared to the previous dual-laser bench at 2,000/s. Stimulated and unstimulated peripheral blood lymphocytes were analyzed according to simultaneous measurements of cell surface receptors labeled with a fluoresceinated neuropeptide and a Texas red-labeled antibody as well as DNA content during the cell cycle. These results demonstrate the broad range of potential applications of this triple-laser system.

Swine chromosomes: flow sorting and spot blot hybridization

Flow cytometry analysis was applied to swine chromosomes prepared from phytohemagglutinin (PHA) stimulated peripheral blood lymphocytes. Flow karyotypes from both sexes and from t(3;7) translocation carrier females were obtained. A certain number of chromosome pairs could be assigned to various peaks. In fact, 13 peaks were observed for 18 autosomal pairs plus X and Y. Moreover, abnormalities owing to the t(3;7) translocation were readily observable. The number of base pairs for chromosomes associated with the various peaks was estimated by comparison with human flow karyotypes. The following four peaks were thus sorted: the peak assumed to represent the translocated chromosome 7 plus the normals associated with it; the corresponding peak from a normal swine; the peak assumed to contain among others the normal chromosome 7; and finally the peak corresponding to swine chromosome 1. Chromosomes of each peak were collected on Pall Biodyne membrane. Following appropriate denaturation and prehybridization, the four samples were hybridized with a human leucocyte antigen (HLA) class I 32P-labelled cDNA probe, representing most of the coding sequence of the HLA B7 gene. The results confirmed previous data from other techniques that assigned the swine MHC(SLA) to chromosome 7. Subsequently, sorted samples were hybridized with a porcine genomic Interferon alpha probe in order to confirm the mapping of this gene family on porcine chromosome 1.

Detecting abnormal human chromosome constitutions by dual laser flow cytogenetics

Our custom dual laser chromosome sorter has been used to characterize and isolate metaphase human chromosomes rapidly for gene mapping purposes. Herein, we tested how well this system could detect unknown abnormal human chromosome constitutions. These results were compared to those of conventional cytogenetic analyses by banding and photomicrography. The sorter was used to analyze each cell line stained with two different stain pairs: DIPI-chromomycin and Hoechst-chromomycin. In 20 min, two histograms representing 2 X 10(5) chromosomes each were collected for each stain pair. A blind study of 11 samples by flow analysis demonstrated excellent concordance between the abnormal chromosomes detected and the diagnoses of Giemsa-banded karyotypes. Aneuploidy was identified by changes in the number of chromosomes in each histogram peak, while rearrangements such as deletions and translocations caused shifts in the histogram peak positions. The direction and distance of histogram peak shifts are directly related to alterations in chromosome size and banding pattern. We conclude that dual-laser flow analysis may provide a rapid approach to the screening and diagnosis of chromosome abnormalities.

Human ferritin light chain gene sequences mapped to several sorted chromosomes

The iron storage ferritin light-chain gene exhibits multiple restriction enzyme fragments which have been mapped by analyzing sorted human chromosomes. A dual laser chromosome sorter was used to construct spot-blot filter panels representing 22 chromosome fractions. Hybridization of radiolabeled human ferritin-L gene probe to spot-blot panels revealed the ferritin-L gene on more than one chromosome. Miniaturized restriction enzyme analysis was used to map each of the ferritin-L restriction fragments uniquely to one of three chromosomes. This combination of sorted chromosome analyses provides a rapid method to map homologous DNA sequences located on more than one chromosome.