GM1-gangliosidosis: chromosome 3 assignment of the beta-galactosidase-A gene (beta GALA)

Native SDS-PAGE: high resolution electrophoretic separation of proteins with retention of native properties including bound metal ions

Sodium dodecyl-sulfate polyacrylamide gel electrophoresis (SDS-PAGE) is commonly used to obtain high resolution separation of complex mixtures of proteins. The method initially denatures the proteins that will undergo electrophoresis. Although covalent structural features of resolved proteins can be determined with SDS-PAGE, functional properties are destroyed, including the presence of non-covalently bound metal ions. To address this shortcoming, blue-native (BN)-PAGE has been introduced. This method retains functional properties but at the cost of protein resolving power. To address the need for a high resolution PAGE method that results in the separation of native proteins, experiments tested the impact of changing the conditions of SDS-PAGE on the quality of protein separation and retention of functional properties. Removal of SDS and EDTA from the sample buffer together with omission of a heating step had no effect on the results of PAGE. Reduction of SDS in the running buffer from 0.1% to 0.0375% together with deletion of EDTA also made little impact on the quality of the electrophoretograms of fractions of pig kidney (LLC-PK1) cell proteome in comparison with that achieved with the SDS-PAGE method. The modified conditions were called native (N)SDS-PAGE. Retention of Zn(2+) bound in proteomic samples increased from 26 to 98% upon shifting from standard to modified conditions. Moreover, seven of nine model enzymes, including four Zn(2+) proteins that were subjected to NSDS-PAGE retained activity. All nine were active in BN-PAGE, whereas all underwent denaturation during SDS-PAGE. Metal retention after electrophoresis was additionally confirmed using laser ablation-inductively coupled plasma-mass spectrometry and in-gel Zn-protein staining using the fluorophore TSQ.

Integration of active human β-galactosidase gene (100 kb) into genome using HSV/AAV amplicon vector

Vectors based on herpes simplex virus type-1 (HSV-1) permit delivery of transgenes of up to 150 kb, while the inverted terminal repeats and Rep of the adeno-associated virus (AAV) can confer site-specific integration into the AAVS1 site, which allows sustained expression of a transgene. In this study, combination of the viral elements in HSV/AAV hybrid vectors has been applied for the infectious transfer of the human lysosomal beta-galactosidase (BGAL) gene of 100 kb. Temporary expression and functional activity of beta-galactosidase (beta-gal) could be detected in human beta-gal-deficient patient and glioblastoma (Gli36) cells upon infection with the basic BGAL amplicon vector. Sustained expression of beta-gal was achieved in Gli36 cells infected with rep-plus, but not rep-minus, HSV/AAV hybrid vectors. None of five clones isolated after rep-minus hybrid vector infection showed elevated beta-gal activity or site-specific integration. In contrast, 80% of the rep-plus clones possessed beta-gal activity at least twofold greater than normal levels for up to 4 months of continuous growth, and 33% of the clones exhibited AAVS1-specific integration of the ITR-flanked transgene. One of the rep-plus clones displayed integration of the ITR cassette only at the AAVS1 site, with no sequences outside the cassette detectable and beta-gal activity fourfold above normal levels. These data demonstrate AAVS1-specific integration of an entire genomic locus and expression of the transgene from the endogenous promoter mediated by an HSV/AAV hybrid vector.

Development of lysosomal storage in mice with targeted disruption of the beta-galactosidase gene: a model of human G(M1)-gangliosidosis

A deficiency of lysosomal acid beta-galactosidase leads to G(M1)-gangliosidosis in humans, which progressively and profoundly affects the brain and other organs mainly in the early infantile period. We report the pathology of mice with targeted disruption of the beta-galactosidase gene. In the central nervous system, vacuolated neurons appeared in the spinal cord 3 days after birth. The vacuolation extended to neurons in the brainstem, cerebral cortex, hippocampus and thalamus and ballooning neurons became prominent with age. The vacuolation also appeared in Purkinje cells without a marked ballooning change. Reactive astrogliosis in the entire brain was marked at the terminal stage of the disease. Immunohistochemical study using anti-ganglioside G(M1) and G(A1) antibodies revealed extensive accumulation of G(M1) and G(A1) in the cerebral neurons. In the liver, however, accumulation of G(M1) was localized in the cytoplasm of hepatocytes, whereas that of G(A1) was localized in foamy macrophages and Kupffer cells. There were no significant abnormalities in the bone, bone marrow, or cornea at any stage. Although there are some phenotypic and biochemical differences between this knockout mouse and human GM1 gangliosidosis, the mouse will be a useful model for therapeutic trials for the human disease.

High levels of GM(1)-ganglioside and GM(1)-ganglioside beta-galactosidase in the parotid gland: a new model for secretory mechanisms of the parotid gland

A new model for the subcellular basis of parotid secretion is presented in this article. GM(1)-ganglioside, typically found in neural tissues, is shown to be abundant in the parotid gland. This ganglioside may play a central role in membrane turnover mechanisms underlying exocytosis/endocytosis in its role as a promoter of membrane fusion or a fusogen. The lysosome and lysosomal hydrolases also play a central role in this model in catabolism of GM(1)-ganglioside. Consequently, high levels of the lysosomal hydrolase acidic beta-galactosidase are demonstrated in the salivary gland. GM(1)-gangliosidosis of the parotid glands, as described in mice, appears to be the first single-gene heritable disease found so far in the salivary glands.

Insertion of a T next to the donor splice site of intron 1 causes aberrantly spliced mRNA in a case of infantile GM1-gangliosidosis

The lysosomal storage disorders GM1-gangliosidosis and Morquio B syndrome are caused by a complete or partial deficiency of acid beta-galactosidase. Here, we have characterized the mutation segregating in a family with two siblings affected by the severe infantile form of GM1-gangliosidosis. In total mRNA preparations derived from the patients' fibroblasts at least two aberrantly spliced beta-galactosidase transcripts (1 and 2) have been identified. Both transcripts contain a 20 nucleotide (nt) insertion derived from the 5' end of intron 1 of the beta-galactosidase gene. Furthermore, in transcript 2 sequences encoded by exon II are deleted during the splicing process. Comparison of the 20-nt insertion with wild-type intronic sequences indicated that in the genomic DNA of the patients an extra T nucleotide is present immediately downstream of the conserved GT splice donor dinucleotide of intron 1. Both patients are homozygous for the T nucleotide insertion. We propose that this single base insertion is the mutation responsible for aberrant splicing of beta-galactosidase pre-mRNA, giving rise to transcripts that cannot encode a normal protein.

Organization of the mouse acid beta-galactosidase gene

Overlapping murine genomic DNA fragments containing the entire cDNA sequence were isolated from a cosmid library prepared from the DBA/2J strain of mice. The gene is more than 80-kb long, consisting of 16 exons. All of the exon-intron boundaries have been defined. The organization of the gene is highly conserved between the murine and human genes at least for the several exons and introns for which information for the human gene is available [Morreau et al., J. Biol. Chem. 264:20655, 1989]. Primer extension and RNase protection experiments indicated the presence of three potential transcription initiation sites, which are preceded by GC-rich SP1 binding sites but without typical TATA or CAT boxes, as is often the case for genes coding for housekeeping proteins. Compared to the cDNA sequence from C57BL/6J mouse, there were five nucleotide polymorphisms in the protein-coding region, two of which resulted in altered amino acids.

Molecular cloning of mouse acid beta-galactosidase cDNA: sequence, expression of catalytic activity and comparison with the human enzyme

A full-length cDNA coding for mouse lysosomal acid beta-galactosidase has been isolated on the basis of homology with the human gene. Catalytic activity toward 4-methylumbelliferyl beta-D-galactoside in the COS-1 cell expression system provided positive proof for its authenticity. The sequence analysis showed that the degree of similarity between the human and mouse enzymes was approximately 70% in the nucleotide sequence and nearly 80% in the amino acid sequence. The deduced primary amino acid sequences of the enzymes from the two species indicated that, of the seven possible N-glycosylation sites in the human enzyme, five are conserved in the mouse enzyme. Three additional possible N-glycosylation sites, not present in the human enzyme, are found in the primary amino acid sequence of the mouse enzyme. All seven cysteine residues in the mouse enzyme are conserved in the human enzyme. Although the nucleotide sequence could be aligned to 60% identity with the E. coli beta-galactosidase, similarity in the amino acid sequence was minimal.

Isolation, characterization, and mapping of a human acid beta-galactosidase cDNA

A lambda gt11 human testicular cDNA library was screened with degenerate oligonucleotide probe mixtures based on amino acid sequence data generated from cyanogen bromide fragments and tryptic fragments of purified human beta-galactosidase. Six positive clones were identified after screening 2 x 10(6) plaques. The sequences of these six clones were determined and found to be derived from two different cDNAs. The sequence of the longest of these cDNAs is nearly identical to that recently determined by Oshima et al. (1988). It codes for a 76-kD protein and all 11 peptides that were generated from the purified enzyme. The second clone is shorter by 393 bp in the central portion of the coding region. Analysis by Northern blotting revealed the presence of a single mRNA species of 2.45 kb in lymphoblasts and testicular tissue. It is deduced from the amino acid sequence data that proteolytic processing of the precursor form of beta-galactosidase must occur by cleavage in the carboxy-terminal portion of the polypeptide perhaps around amino acid 530 at a uniquely hydrophilic sequence. Using a probe generated from the 3' region of the cDNA, we have mapped the locus coding for human beta-galactosidase to chromosome 3p21-3pter.

A chromosomal segment conserved since divergence of lineages leading to man and mouse: the gene order of aminoacylase-1, transferrin, and beta-galactosidase on mouse chromosome 9

Linkage crosses were used to determine the gene order of aminoacylase-1, beta-galactosidase, and transferrin on mouse Chromosome 9. The most likely gene order, which was more than 107times more likely than the next most likely order, was transferrin, aminoacylase-1, beta-galactosidase. These results demonstrate that aminoacylase-1 and beta-galactosidase mark a chromosomal segment that has been conserved since divergence of lineages leading to man and mouse. The length of this segment is about 11 cM and the estimate of the true length of the conserved segment marked by these two genes is 33 cM. A second aminoacylase allozyme, which requires MgCl2, is described.

Chromosomal assignments of human genes for serine proteases trypsin, chymotrypsin B, and elastase

The genes for the serine proteases trypsin, chymotrypsin B, and elastase were chromosomally assigned in man using cDNA probes that have been isolated from a rat pancreatic cDNA library. DNA from human X rodent somatic cell hybrids was cleaved with BamHI or EcoRI and analyzed by Southern filter hybridization methods for the segregation of the genes for trypsin-1 (TRY1), chymotrypsin B (CTRB), and elastase-1 (ELA1). TRY1 was assigned to human chromosome 7q22----qter, CTRB to chromosome 16, and ELA1 to chromosome 12. Although the three genes are members of the same gene family, they are dispersed over different chromosomes.

Interleukin 2 (IL2) is assigned to human chromosome 4

The human gene for interleukin 2 (IL2) was assigned to chromosome 4 using human-mouse somatic cell hybrids and Southern filter hybridization of cell hybrid DNA. To identify IL2, a recombinant DNA probe ( pIL2 - 50A ) was used which contained a human interleukin 2 cDNA insert which hybridized to a 3.5-kb fragment in human DNA when cleaved with the restriction enzyme EcoRI.

Molecular cloning and sequence analysis of cDNA for human transferrin

A cDNA clone for human transferrin was identified from a human liver cDNA library by pre-screening with different ss-cDNA probes against length-fractionated liver mRNAs, positive hybridization-selection and nucleotide sequence analysis. The insert was of 1 kb, encoding human transferrin from aminoacid 403 through the COOH terminus, with a 3' non coding region of 166 nucleotides. This insert hybridized with a single major mRNA species of about 2.4 kb and several genomic DNA restriction fragments. Hybridization of the Southern blots with different parts of the transferrin insert and at different stringences suggest that the various bands observed correspond to splice sites inside one gene rather than to hybridization to several related genes. Finally, a single or a low number of transferrin gene copies seem to exist in the human genome.

Regional assignment of the structural gene for human alpha-L-iduronidase

The structural gene encoding human alpha-L-iduronidase has been assigned to chromosome 22 by using immunologic, electrophoretic, and somatic cell hybridization techniques. Polyclonal rabbit antibodies raised against purified human low-uptake alpha-L-iduronidase were used to discriminate the human and murine isozymes by a sensitive immuno-precipitation assay. The human chromosome constitution of each clone was determined by cytogenetic and enzyme marker electrophoretic techniques. In 65 human (fibroblast)-mouse (RAG) somatic cell hybrids (from four independent fusions), the expression of human alpha-L-iduronidase was 100% concordant with the presence of human chromosome 22; the assignment was confirmed by the demonstration of the human enzyme in tertiary somatic cell hybrids containing only chromosome 22. Further verification of the gene assignment was made by detection of the human enzyme in tertiary chromosome 22 positive hybrids by Ouchterlony immunodiffusion and rocket immunoelectrophoretic experiments with polyclonal anti-human alpha-L-iduronidase antibodies that were monospecific for the human enzyme. Expression of human enzymatic activity in chromosome 22 positive hybrid lines was markedly reduced; for example, a tertiary hybrid (R-G21-J-15), which contained an average of 1.7 chromosome 22s per cell, only had about 15% of the activity detected in normal diploid fibroblasts. Immunologic studies suggested that the reduced expression was due to abnormal post-translational processing or aggregation (or both) of the human and murine isozymes in these hybrids. Regional assignment of the human structural gene to 22pter----q11 was accomplished by gene dosage studies using diploid human fibroblast lines that were partially monosomic or trisomic for chromosome 22.

Multigene family for sarcomeric myosin heavy chain in mouse and human DNA: localization on a single chromosome

Cloned myosin heavy chain DNA probes from rat and human were hybridized to restriction endonuclease digests of genomic DNA from somatic cell hybrids and their parental cells. The mouse myosin heavy chain genes detectable by this assay were located on chromosome 11, and three different human sarcomeric myosin heavy chain genes were mapped to the short arm of chromosome 17. A synteny between myosin heavy chain and two unrelated markers, thymidine kinase and galactokinase, was found to be preserved in the rodent and human genomes.

The eye and the chromosome

The first linkage of disease traits on the human X-chromosome was reported in 1937, and the first assignment of a human disease to an autosome was made 26 years later in 1963. Now, after only 19 years, there are at least 338 assignments to loci on the human chromosome map. This amazing expansion of information extends to eye diseases. In this review, basic mechanisms of mutation are discussed, and the basic methodologies used for gene assignments are explained. All of the eye-related, definite, autosomal assignments are presented. The diseases that have regional assignments on the X-chromosome are discussed, and the remaining X-linked eye diseases are listed in table form.

Assignment of the gene for human melanoma-associated antigen p97 to chromosome 3

p97 is a 97,000 molecular weight cell-surface glycoprotein, which is present in human melanomas but in only trace amounts in normal adult tissues. Amino acid sequence and iron binding studies have shown that p97 is structurally and functionally related to transferrin. Reports that the genes for the transferrin receptor (TR) and possibly transferrin are located on chromosome 3 prompted us to investigate the chromosomal localization of the p97 gene. Our strategy was to characterize interspecies somatic cell hybrids derived from human fibroblasts or lymphocytes for expression of p97 and presence of human chromosomes. Although fibroblasts and lymphocytes express only small amounts of p97, we were able to type the hybrids for p97 by using monoclonal antibodies in highly sensitive and specific immunoassays. Of 14 hybrids, 6 contained chromosome 3 and expressed p97, and 8 were negative for both. We conclude that the p97 gene, like the transferrin and TR genes, is located on chromosome 3.

Structural gene coding for multifunctional protein carrying orotate phosphoribosyltransferase and OMP decarboxylase activity is located on long arm of human chromosome 3

In humans, deficiency in the last two enzymes of UMP biosynthesis, orotate phosphoribosyltransferase (OPRT) and OMP decarboxylase results in the inborn error of metabolism hereditary orotic aciduria, type 1. In this manuscript, we present immunologic, molecular, biochemical, and genetic evidence that the gene coding for this set of enzymatic activities is located on the long arm of human chromosome 3. The evidence presented here is consistent with both these activities being carried on the same multifunctional protein in mammalian cells. These studies allow further genetic analysis of human chromosome 3, confirming that human markers ACY-1, previously assigned to 3p21, and beta-gal, previously assigned by others to the region 3(p21-q21), must be in the region 3 (cen-p21) and confirming the regional assignment of a human DNA segment, D3S1, to 3q12. The significance of these studies to genetic analysis of genes on human chromosome 3, some of which appear to play a role in some forms of malignancy, is discussed.

Chromosomal assignment of the gene for the human beta 2-adrenergic receptor

Chinese hamster fibroblasts (CHW) fail to physiologically respond to the beta-adrenergic agonist isoproterenol with an increase in cellular cAMP. This unresponsiveness is due to a lack of beta-adrenergic receptors as indicated by an absence of specific binding of 125I-labeled hydroxybenzylpindolol (125I-HYP) to CHW plasma membranes. Preparation of somatic cell hybrids between CHW and human peripheral blood leukocytes led to the selection of a panel of 15 human-Chinese hamster cell hybrid clones, some of which had beta 2-adrenergic receptors (specifically bound 125I-HYP) and responded to isoproterenol (accumulated cAMP). Biochemical analysis of independent cloned cell hybrids indicated that beta 2-adrenergic receptor density and the intensity of the associated physiological response were closely correlated (r = 0.98). Both of these parameters were concordant in all cell hybrids with the presence of human chromosome 5. All other human chromosomes could be ruled out. These results suggest that the structural gene for the beta 2-adrenergic receptor is found on human chromosome 5.

Gene for glutathione S-transferase-1 (GST1) is on human chromosome 11

The glutathione S-transferases (GST) are a group of related enzymes that can detoxify potentially carcinogenic electrophiles by conjugating them with reduced glutathione (GSH). The chromosomal location of one of the enzyme forms, GST1, reported recently to be polymorphic, was determined utilizing man-mouse somatic cell hybrids segregating human chromosomes. The expression of GST1 by hybrid clones was compared with that of 34 enzyme markers representing 23 chromosomes, and karyotypes of selected cell hybrids were analyzed. The evidence indicated that GST1 is assigned to chromosome 11 in humans. Utilizing and X/11 translocation segregating in hybrids, GST1 was localized to the p13 leads to qter region of chromosome 11.

Expression of human transferrin receptor is controlled by a gene on chromosome 3: assignment using species specificity of a monoclonal antibody

The monoclonal antibody OKT-9 has been shown to recognize the human transferrin receptor. We have exploited the species specificity of OKT-9 to map a gene controlling human transferrin receptor expression to chromosome 3, using human-mouse somatic cell hybrids. The gene for the human transferrin receptor and the gene controlling transferrin expression may be linked in humans.

Human beta-galactosidase and alpha-neuraminidase deficient mucolipidosis: genetic complementation analysis of the neuraminidase deficiency

Human beta-galactosidase and alpha-neuraminidase deficient mucolipidosis [ML(gal-neur-)] is an inherited lysosomal enzymopathy which recently was designated as a sialidosis. We analyzed the neuraminidase deficiency of this disorder with genetic complementation analyses using a heterokaryon enrichment procedure. The genetic defects of two apparent variants of this disorder complemented the defects of the neuraminidase deficiency diseases, sialidosis I and mucolipidosis I, resulting in the restoration of neuraminidase activity in heterokaryons. The neuraminidase deficiency, therefore, may not be the primary defect in ML(gal-neur-) and is not an appropriate test for determining carrier status. The clinical and biochemical characteristics of this disorder suggest that a post-translational or processing event for these enzymes may be defective. The defect, however, is different from I-cell disease and pseudo-Hurler polydystrophy, two disorders of post-translational lysosomal enzyme biosynthesis, since complementation studies demonstrated recovery of intracellular beta-galactosidase and alpha-neuraminidase levels in heterokaryons. The lack of human beta-galactosidase expression in man-mouse somatic cell hybrids formed from fibroblasts of the infantile onset type disorder suggests that the defect is not corrected by the mouse genome. The ML(gal-neur-) disorder therefore appears to be a distinct subtype of the inherited neuraminidase deficiencies in which the defect mat occur in a post-translational or regulatory step which coordinately affects the expression of lysosomal beta-galactosidase and alpha-neuraminidase.

Assignment of the glyoxalase II gene (HAGH) to human chromosome 16

The human and rodent forms of glyoxalase II (Hydroxyacylglutathione hydrolase, HAGH) can readily be separated by starch gel electrophoretic procedures. Fifty-one human-rodent somatic cell hybrid clones were examined for their human HAGH and for human enzyme markers whose genes are encoded on each autosome and the X chromosome. Sixteen clones were also examined for their human karyotypes. Human glyoxalase II segregated only with chromosome 16, demonstrating that the gene is located on this chromosome.

The proopiocortin (adrenocorticotropin/beta-lipoprotein) gene is located on chromosome 2 in humans

The proopiocortin gene is located on chromosome 2 in humans. A 13-kb DNA fragment containing proopiocortin gene sequences was identified in human cells while proopiocortin-related genes sequences of 9.8 and 6.2 kb were present in mouse cells. In human-mouse cell hybrids which contained reduced numbers of human chromosomes and a complete set of mouse chromosomes, the 9.8- and 6.2-kb fragments were always present while the 13-kb fragment segregated with human chromosome 2 and the chromosome 2 enzyme markers acid phosphatase-1 (ACP1), malate dehydrogenase-1 (MDHI), and isocitrate dehydrogenase-1 (IDH1). Analysis of a single cell hybrid with a broken chromosome 2 indicates that the proopiocortin and ACP1 genes are closely linked and in the distal region of the short arm of chromosome 2.

Assignment of LIPA, associated with human acid lipase deficiency, to human chromosome 10 and comparative assignment to mouse chromosome 19

The genetics of lysosomal acid lipase (LIP) has been investigated in human-Chinese hamster and mouse-Chinese hamster somatic cell hybrids. Cellulose acetate electrophoresis of human fibroblast extracts demonstrated that LIP activity consists of three isozymes. A deficiency of LIP activity has been observed in Wolman's disease (WD), cholesterol ester storage disease (CESD), and I-cell disease (ICD); this deficiency was associated with only one LIP isozyme, LIPA. We have demonstrated concordant segregation between human LIPA and human chromosome 10 and its enzyme marker glutamate oxaloacetate transaminase-1 (GOT1) in cell hybrid clones. Previous evidence suggested the different mutations associated with WD and CESD to be in the structural gene which we assign to human chromosome 10, while a different gene, involved in the processing of LIPA, is altered in ICD. These results indicate that several types of gene products are involved in the final expression of LIPA. In mouse-Chinese hamster hybrid clones, mouse Lip-1 (homologous to human LIPA) was assigned to chromosome 19. Previously, mouse Got-1 has been assigned to chromosome 19. Thus, the LIPA-GOT1 linkage groups has remained intact during the 80 X 10(6) years of evolution that separates humans and mice.

Leukocyte and fibroblast interferon genes are located on human chromosome 9

At least eight leukocyte interferon genes (IFL) and the single fibroblast interferon gene (IFF) have been located on chromosome 9 in humans. In somatic cell hybrids of human and mouse cells containing a normal complement of mouse parental cell chromosomes but reduced numbers of human chromosomes, the human leukocyte and fibroblast interferon DNA sequences were present only when human chromosome 9 was also present.

Genes for growth hormone, chorionic somatommammotropin, and growth hormones-like gene on chromosome 17 in humans

The human genes for growth hormone (GH), chorionic somatomammotropin (CSH), and a third growth hormone-like gene (GHL) have been located on chromosome 17 in humans. DNA fragments of 2.6, 2.8, and 9.5 kilobase pairs containing GH, CSH, and GHL, respectively, were identified in human genomic DNA, and a 7.5-kilobase DNA fragment related to growth hormone DNA sequences was found in mouse cells. In somatic hybrids of human and mouse cells containing reduced numbers of human chromosomes, but a normal complement of mouse chromosomes, the mouse, 7.5-kolobase DNA fragment was always present, whereas the 2.6-, 2.8-, and 9.5-kilobase human fragments were present only when human chromosome 17 was also present.

Isozyme studies on the association of the herpes simplex virus type 1 thymidine kinase gene with human chromosomes in somatic cell hybrids

To investigate chromosomal site(s) of integration of the herpes simplex virus type 1 (HSV-1) thymidine kinase (TK) gene in biochemically transformed [HeLa(BU25)/KOS 8-1] cells, these human cells which had been transformed by ultraviolet light-irradiated HSV-1 were fused with TK-negative mouse LM(TK-) cells, human-mouse somatic cell hybrid clones (LH81 clones 1-20) were isolated by HATG-ouabain selection and their chromosomes and isozymes were analyzed. Electrophoretic and serological analyses showed that all 20 clones expressed type-specific HSV-1 TK. Isozyme analyses on 29 gene-enzyme systems representing 22 human chromosomes revealed that all of the HSV-1 TK-positive clones expressed human aminoacylase-1 (ACY-1) and esterase D (ESD), which have been mapped to human chromosomes 3 and 13, respectively. Other human isozymes were detected in only one to four clones or in none of the clones. Chromosome analyses showed that: (1) the hybrid clones retained only a few human chromosomes; (2) a marker chromosome, designated M7, consisting of a chromosome 17 translocated to the short arm of chromosome 3, occurred in 36 out of the 41 metaphases examined of LH81-4 clones 1 to 4 and in 31 out of the 33 metaphases examined of LH81-12 clone 10; (3) a modified M7 chromosome, (M7/m), in which the distal 2/3 of the long arm of M7 was translocated to a small acrocentric mouse chromosome, was the only human chromosome found in metaphases of LH81-13 clone 17; and (4) an intact human chromosome 13 was not present in LH81-12 clone 10 or LH81-13 clone 17 cells. Counterselection with BrdUrd resulted in the isolation of subclones lacking HSV-1 TK, human ACY-1 and ESD, and the human marker M7 chromosomes. The experiments indicate that the HSV-1 TK gene is probably associated in HeLa (BU25)/KOS 8-1 cells with marker chromosome M7, but the possibility is not excluded that the segment of human chromosome 13 which codes for ESD is involved.

Human lysosomal genes: arylsulfatase A and beta-galactosidase

The segregation of human lysosomal arylsulfatase A (ARS-A) has been evaluated in 50 primary hybrid clones derived from four separate fusions involving WBCs from two unrelated individuals and three hamster cell lines. ARS-A was expressed in the hybrids as a dimeric molecule of very similar or identical subunits. The expression of this enzyme was concordant with that of mitochondrial aconitase (ACON-M), an isozyme assigned to chromosome 22, in all 50 clones and with chromosome 22 segregation in all but one of the 29 karyotyped hybrids. No other human chromosome cosegregated with 22 in these clones, suggesting that this enzyme is specified in hybrid cells by a locus (or loci) on a single chromosome. beta-Galactosidase (B-GAL) expression was analyzed with two different electrophoresis systems and with a number of cell extract preparation methods in 39 of the primary hybrid clones. The B-GAL isozyme expressed in these hybrid cells was concordant with the expression of glutathione peroxidase-1 (GPX-1), an isozyme assigned to chromosome 3, in all 39 clones and with the segregation of this chromosome in 97% of the 29 karyotyped hybrids. These observations substantiate the prior tentative assignments of an ARS-A locus to chromosome 22 and a B-GAL locus to chromosome 3 (Bruns et al., 1978a, b). The implications of the chromosome assignments of loci for 12 human lysosomal enzymes for the cellular assembly of these organelles are discussed.