Molecular mechanisms of McArdle's disease (muscle glycogen phosphorylase deficiency). RNA and DNA analysis.

Lack of muscle glycogen phosphorylase activity leads to McArdle's disease, a rare metabolic myopathy. To investigate its molecular basis at the nucleic acid level, we isolated muscle phosphorylase cDNA clones from a human cDNA library in Escherichia coli plasmid pBR 322. Subcloning of one insertion of M13 bacteriophage permitted its definite identification by sequencing. Northern blot experiments revealed one specific messenger RNA of 3.4 kilobases found uniquely in tissues expressing muscle phosphorylase. We show that McArdle's disease exhibits a molecular heterogeneity at the messenger RNA level. In eight unrelated cases of McArdle's disease in which no inactive proteins had been detected, we assayed muscle biopsies for phosphorylase mRNA by Northern blotting. In five cases, no muscle phosphorylase mRNA could be detected, while in three other cases, normal length mRNA was present in lower amounts. Moreover, Southern blot analysis of DNA isolated from white blood cells in four McArdle patients revealed no major deletion or rearrangements of the phosphorylase gene as compared with controls.

Transient transcriptional inhibition of the transferrin gene by cyclic AMP.

Transferrin mRNA content and gene transcription rate were measured in the liver of rats submitted to iron overload or depletion, castration, treatment with sexual steroid hormones, glucagon and cyclic AMP. The influence of puberty in males and females and of pregnancy was also analysed. Glucagon and cyclic AMP reduced mRNA level by about 50% at the 12th hour of treatment and transferrin gene transcription by as much as 95% at the 30th minute of drug infusion, with a secondary increase of the transcription rate for a protracted treatment. None of the other hormones tested had any detectable effect on transferrin gene expression, the same being true for iron overload or depletion.

Characterization and metabolic regulation of a liver-specific 5.4-kilobase mRNA whose synthesis is transcriptionally induced by carbohydrates and repressed by glucagon and cyclic AMP.

Four clones derived from a carbohydrate-induced rat liver cDNA library were found to hybridize with a 5.4-kilobase mRNA species encoding a 36 kDa protein. This mRNA was abundant in the liver, barely detectable in adipocytes and kidney, and absent from the other tissues tested. In the liver, the mRNA was fully induced by a carbohydrate-rich diet, but was undetectable during both starvation and feeding with a protein-rich or lipid-rich diet. Adrenalectomized, thyroidectomized and diabetic animals did not express the mRNA in their liver when re-fed with the carbohydrate-rich diet. When these animals were given the missing hormone, the amount of hybridizable RNA returned to normal values, but administration of the hormone alone failed to induce mRNA synthesis in starved animals. Both glucagon and its second messenger, cyclic AMP, abolished the induction of the mRNA in re-fed animals. Exogenous insulin, whatever the dose, did not reverse the inhibitory action of glucagon. In an isolated nuclei transcription system, no detectable RNA transcripts were found in starved animals, whereas feeding the animals with the carbohydrate-rich diet led to a maximum rate of gene transcription. Although unidentified, this mRNA proves to be a remarkable marker of dietary and hormonal control of gene expression in vivo. It will provide a useful model for further analysis of the role of cyclic AMP in regulating the transcription of eukaryotic genes.

Dietary and hormonal regulation of aldolase B gene expression.

Aldolase B is an enzyme of the glycolytic pathway whose activity and mRNA levels in the liver fluctuate according to dietary status. Both the enzyme activity and the mRNA concentration decline during fasting and increase four- to eightfold upon refeeding of a carbohydrate-rich diet. The mechanism, however, of the mRNA induction remains unknown. To elucidate the mechanisms that regulate this induction responsive to dietary stimuli, we have studied the roles of hormones and glycolytic substrates on aldolase B gene expression in three tissues that synthesize the enzyme. Using a cDNA probe complementary to rat aldolase B mRNA, we determined the amount of cytoplasmic RNAs in the liver, kidney, and small intestine of normal, adrenalectomized, thyroidectomized, diabetic, and glucagon- or cAMP-treated animals refed either a fructose-rich or a maltose-rich diet. The in vivo hormonal control of gene expression was found to be very different in the three organs tested. In the liver, cortisone and thyroid hormones were required for the induction of the specific mRNA by carbohydrates, while in the kidney none of the hormonal modifications tested altered the level of mRNA induction. In the liver, but not in the kidney, diabetes and glucagon administration abolished the induction of aldolase B mRNAs in animals refed the maltose-rich diets. In the small intestine, only diabetes and thyroidectomy affected the gene expression. Finally, no induction occurred when normal fasted rats were given any of the hormones. Thus, the in vivo hormonal control of liver aldolase B gene expression differs significantly from that of kidney and small intestine. In the liver, the mRNA induction requires the presence of dietary carbohydrates, of permissive hormones, and the cessation of glucagon release, while in the kidney, the induction of the mRNAs by fructose occurs regardless of the hormonal status of the animals. The hormonal control of aldolase B mRNA levels in the small intestine is intermediate.

[Early prenatal diagnosis of lysosomal enzymopathies from biopsies of trophoblasts]. / Diagnostic prénatal précoce des enzymopathies lysosomiales à partir de biopsies de trophoblastes.

This study was undertaken to assess the reliability of trophoblastic biopsy for early ante-natal diagnosis (10 weeks) of lysosomal diseases, including glycogenoses, sphingolipidoses and mucopolysaccharidoses. The sensitivity and specificity were excellent. In addition, cell cultures of the trophoblastic material enable further confirmation of the diagnosis. The possibility of a diagnosis and a medical decision with regards to the outcome of pregnancy at the 10th week of gestation is a considerable advance compared to diagnostic amniocentesis between the 17th and 20th weeks. In our opinion, if a total deficit is observed, the decision to terminate the pregnancy can be taken; in partial deficits or in cases with normal activity, it is wise to confirm the diagnosis by amniocentesis.

[Study of hereditary fructose intolerance by methods of molecular biology]. / Etude de l'intolérance héréditaire au fructose par les méthodes de la biologie moléculaire.

Fructose intolerance is caused by a deficit of the liver aldolase B enzyme. Its molecular mechanisms were studied at different sites: The protein was studied by a method combining electrophoresis, transfer and immunology. It was present in the 15 cases examined. The genetic variability was demonstrated by the quantitative differences of the immunoreactive proteins. Aldolase messenger RNA was prepared and used to direct in vitro synthesis of human aldolase. Cloning complementary DNA of human aldolase was achieved by using the messenger RNA. Two clones were prepared. The aldolase B gene was then analysed using restriction enzymes in 60 control subjects and 11 patients. An abnormality of the DNA was demonstrated in one of the patients and in her father.

Immunological screening of standard cDNA libraries in pBR322 vectors: detection of human fibrinogen and prothrombin cDNA clones.

The in situ immunological detection of antigens encoded by cDNA inserted into the PstI site of pBR322 plasmids was optimized. It was found that sensitivity of the detection was dramatically increased by in situ amplification of the recombinant plasmids on chloramphenicol-containing medium followed by a brief incubation without chloramphenicol during which protein synthesis resumes. In addition, several modifications of the previously described methods which permit total suppression of background and false positives are described. These techniques allowed easy detection of cDNA clones for human B beta- and gamma-fibrinogen and -prothrombin using a human liver double-stranded cDNA recombinant plasmid library in pBR322 vectors.

DNA analysis in patients with hereditary fructose intolerance.

Restriction fragments of the aldolase B gene were studied in 11 patients with hereditary fructose intolerance and compared with the normal pattern. No major deletion of the gene was observed. One patient was found to be a compound heterozygote since one allele with normal restriction sites was inherited from the mother and the other with an abnormal Bam HI site was inherited from the father. The anomaly of the Bam HI fragment observed in this family was not found in 62 normal controls from the same origin as the patient.

Evaluation of possible first trimester prenatal diagnosis in lysosomal diseases by trophoblast biopsy.

The detection of enzymatic deficiency in cultured amniotic cells from second trimester pregnancies is presently used for prenatal diagnosis of lysosomal diseases. The possibility of obtaining and processing trophoblast tissue at 8-10 weeks of gestation would permit first trimester prenatal diagnosis. Using trophoblast tissue samples from normal fetuses before voluntary abortion and from placenta after therapeutic abortions of fetuses affected by several lysosomal diseases, we conclude that early diagnosis of lysosomal disorders would be possible.

Effects of antisera raised against native and denatured human alpha-glucosidase and beta-hexosaminidases on native enzyme activity.

Antisera were raised in rabbits against native and sodium dodecylsulfate denatured forms of human acid alpha-glucosidase and beta-hexosaminidases A and B. Anti-native enzyme antisera were able to precipitate all or nearly all enzyme activity from cell extracts, and to eliminate all stainable activity on electrophoresis. Antisera prepared against denatured enzymes precipitated only a minor part of enzyme activity. Electrophoretic analysis showed that these antisera were able to bind to the enzyme molecule. The result was a slowing down of the anodic migration but not immobilization. The use of variants with hexosaminidase deficiencies helped to clarify the action of the antisera on the various hexosaminidase isozymes.

Expression of the transferrin gene during development of non-hepatic tissues: high level of transferrin mRNA in fetal muscle and adult brain.

Using a cloned rat transferrin cDNA probe, we looked for transferrin mRNA in the various rat tissues during development. In all the cases the mRNA detected seemed to be the same and to be product of a single gene. The transferrin gene is early expressed at a high level during liver differentiation. In the muscle and other non-hepatic and non-nervous tissues, the gene expression is maximal just before birth (19-20th day of gestational age), then markedly decreases during the postnatal development, the mRNA level being very low in the adult tissues. In brain, by contrast, transferrin mRNA level is very low before birth, then gradually increases during the postnatal development and reaches a plateau in the adult. Maximal mRNA concentration in fetal muscle (2 days before birth) and adult brain is about 1:7 to 1:10 of that obtained in adult liver. These results are analyzed in the light of the evidence that transferrin is not only an iron-binding protein, but also a factor involved in cell proliferation and differentiation, and particularly in nerve control of muscle differentiation.

High frequency of beta-hexosaminidase deficiency in lymphoblastoid cell lines.

The activity of seven lysosomal enzymes was determined in 25 lymphoblastoid cell lines. These lines included normal controls transformed with Epstein-Barr virus, Burkitt's lymphomas and other lymphomas with or without EBV genome. Four lines were deficient in total beta-hexosaminidase activity. The deficiency was as severe as that of the variant O (Sandhoff's disease) of clinical beta-hexosaminidase deficiency. The electrophoretic pattern was also similar to that observed in Sandhoff's disease. The possible mechanisms explaining the high frequency of beta-hexosaminidase deficiency in lymphoblastoid cell lines are discussed.

Dietary control of aldolase B and L-type pyruvate kinase mRNAs in rat. Study of translational activity and hybridization with cloned cDNA probes.

Liver L-type pyruvate kinase and aldolase B mRNAs are the two species whose translational activity increases the most after feeding starved rats a high carbohydrate diet (Simon, M. P., Besmond, C., Cottreau, D., Weber, A., Chaumet-Riffaud, P., Dreyfus, J. C., Sala Trépat, J., Marie, J., and Kahn, A. (1984) J. Biol. Chem., in press). We therefore compared the pattern of this induction in three tissues synthesizing these enzymes, e.g. the liver, small intestine, and kidney. Influence of high lipid and protein diets on liver L-type pyruvate kinase and aldolase B mRNAs was also investigated. In the starved rat livers, L-type pyruvate kinase mRNA was practically undetectable. Carbohydrate diet induced an increase of both mRNA concentrations, with a maximum at the 12-18th h; at this time, mRNA concentration was increased about 4-8 times for aldolase B and 40-100 times for L-type pyruvate kinase, translational activities representing about 1% of the total mRNA activity for both enzymes. After the 24th h of carbohydrate diet, mRNA concentrations decreased slightly, then remained in plateau. In animals refed the high carbohydrate diet, starvation as well as high lipid and protein diets provoked a rapid decrease of both mRNA concentrations and translational activities. In the kidney, aldolase B mRNA synthesis was high in starved rats and was only slightly stimulated by carbohydrates (1.5-2.5 times). L-type pyruvate kinase mRNA concentration was increased 6-15-fold after feeding a high carbohydrate diet. In the small intestine, in contrast, the extent of aldolase B mRNA induction by a carbohydrate diet was similar to that in the liver, while L-type pyruvate kinase mRNA concentration was practically similar in starved and refed rats (about 1:10 of the concentration observed in refed rat liver). These results seem to indicate that the mechanisms responsible for carbohydrate induction of L-type pyruvate kinase and aldolase B are different. In addition, dietary control of each enzyme is also different in the various tissues which synthesize them.

Molecular cloning of cDNA for rat L-type pyruvate kinase and aldolase B.

Two double-stranded cDNA recombinant pBR322 plasmid libraries were constructed starting from high carbohydrate diet rat liver poly(A)+ mRNA, either fractionated by denaturing sucrose gradient centrifugation for the cloning of L-type pyruvate kinase cDNA, or nonfractionated for aldolase B. Both libraries were screened with single-stranded cDNA probes reverse transcribed from fasted or high carbohydrate diet rat liver mRNAs. mRNAs from fasted animals were also fractionated by sucrose gradient centrifugation and mRNAs from the fed animals were, in addition, further purified by high performance liquid gel filtration chromatography. Those clones hybridizing with the "positive" probe (from animals fed the high carbohydrate diet) and not with the "negative" one (from fasted animals) were preselected and their plasmid DNA was purified and analyzed by positive hybridization-selection. Thirty of 4500 bacteria colonies transformed by recombinant plasmids were preselected by differential screening for pyruvate kinase, and 8 of 864 colonies for aldolase B. Twenty-two recombinant plasmids for pyruvate kinase and two for aldolase B were shown to contain specific cDNA inserts by positive hybridization-selection. Plasmids DNAs of some pyruvate kinase and aldolase B clones (whose inserts ranged from 700 to 1050 bases in length) were labeled by nick translation and used as probes for Northern blot hybridization. The pyruvate kinase cDNA probes recognized mainly a 3400-base RNA species which was detected in high carbohydrate diet rat liver, but not in fasted rat liver and in tissues which do not synthesize L-type pyruvate kinase. In addition, some pyruvate kinase probes hybridized with minor RNA species of about 2000 bases in length, only observed after carbohydrate diet. For aldolase B, the recombinant plasmid DNA hybridized with a single RNA species of 1750 bases. This RNA, detected in kidney, small intestine and liver, was induced by a high carbohydrate diet and increased with liver development. The rat probe cross-hybridized with human aldolase B messenger RNA.

Nucleotide sequence of a cDNA clone for human aldolase B.

Two specific clones for human aldolase B were isolated from a human liver cDNA library using a rat aldolase B cDNA probe. The clones were identified by positive hybridization-selection and one of them was sequenced. The 127 C-terminal residues of the human protein were deduced from this nucleotide sequence analysis. They showed 92% homology with the corresponding previously published amino-acid sequence of rat liver aldolase B.

Protein ADP-ribosylation in rat liver cytosol.

ADP and poly ADP-ribosylation are post-translational modifications of proteins which have been reported to occur essentially in eucaryotic nuclei. This phenomenon has been shown to interfere with a great variety of biological functions (cell differentiation, DNA repair, malignant transformation...). In this paper, we demonstrate for the first time that ADP-ribosylation occurs also in cytosol (120 000 g supernatant) and that several cytosolic proteins can be ADP-ribosylated in rat liver.

Molecular studies on galactose 1 phosphate uridylyl transferase from normal and mutant subjects. An immunological approach.

The mutant forms of uridylyl transferase of eight galactosemic patients and two 'Rennes' variants were characterized with regard to the presence and level of immunoreactive protein, the apparent subunit molecular weight and the isoelectric point. Semi-purified haemolysates were studied by various electrophoretic techniques, then proteins were electrophoretically transferred on to nitrocellulose filters. They were treated with specific anti-transferase antibodies, and then with radioiodinated protein A, followed by autoradiography. We have found that: in all cases, a cross-reacting material was detectable, with a molecular subunit size of 46 000, indistinguishable from that of controls. a biochemical heterogeneity of the mutant enzyme was found: the amount of apparent immunologically reactive protein varied from 20 to 100% of that of controls; electrophoretic experiments performed on two 'Rennes' variants showed an increased negative charge.

Induction of glycolytic enzyme synthesis in proliferating fibroblasts. Study of phosphofructokinase, glucose phosphate isomerase and pyruvate kinase.

Specific activity of phosphofructokinase is 7-8-fold higher in exponentially growing human fibroblasts than in quiescent cells, but the difference is considerably less pronounced for two other glycolytic enzymes, glucose phosphate isomerase and pyruvate kinase. The ratio of the F-type to L-type phosphofructokinase subunits is essentially the same in growing and resting cells, 4:1. F-type-phosphofructokinase-related antigen concentration is decreased in resting cells as compared with proliferating fibroblasts, but relatively less than the enzyme activity; the ratio of the enzyme activity to the antigen concentration (immunological specific activity) is therefore lower in resting than in growing fibroblasts. Synthesis of phosphofructokinase, as a percentage of the total protein synthesis, is about 30-fold greater during the proliferative phase than in quiescent cells, but this difference is only 3-4-fold for glucose phosphate isomerase and pyruvate kinase. Modulation of the synthesis of phosphofructokinase therefore seems to be responsible for the changes of its specific activity in function of cell proliferation. The appearance of some inactive cross-reacting material in quiescent cells is probably due to post-translational alteration of the pre-synthesized molecules. Compared with other glycolytic enzymes, such as glucose phosphate isomerase and pyruvate kinase, phosphofructokinase seems to be the (or one of the) preferential target of glycolytic induction in proliferating cells.