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J Chelly

Publications and source records attributed to J Chelly.

At least 109 records · Page 6Linked to original sources
PubMed1991

Illegitimate (or ectopic) transcription proceeds through the usual promoters.

Illegitimate transcription corresponds to the low level presence of specific transcripts in nonspecific cells. This phenomenon allows to analyse any tissue-specific disease transcript in any easily accessible cell. We demonstrate here that the start sites of transcription are the same in specific and non-specific cells, which indicates that illegitimate transcription is due to a low level activity of the normal promoter. In addition, it is possible to increase about 10 fold the abundance of illegitimate transcripts through the use of cycloheximide. This treatment should, therefore, facilitate detection and qualitative analysis of illegitimate transcripts.

Base Sequence↗
PubMed1991

Functional adult acetylcholine receptor develops independently of motor innervation in Sol 8 mouse muscle cell line.

We have defined culture conditions, using a feeder layer of cells from the embryonic mesenchymal cell line, 10T1/2 and a serum-free medium, which allow cells from the mouse myogenic cell line Sol 8 to form contracting myotubes for two weeks. Under these culture conditions, Sol 8 myotubes undergo a maturation process characterized by a sequential expression of two phenotypes. An early phenotype is typified by the expression of the nicotinic acetylcholine receptor (AChR) gamma-subunit transcripts and the presence of low conductance ACh-activated channels, typical of embryonic AChR. A late phenotype is characterized by the expression of AChR epsilon-subunit transcripts, the decreased accumulation of gamma-subunit transcripts and the appearance of high conductance ACh-activated channels, typical of adult AChR. These results indicate that the expression of functional adult type AChR does not require the presence of the motor nerve and therefore represents an intrinsic feature of the Sol 8 muscle cells. Chronic exposure of the cells to the voltage-sensitive Na+ channel blocking agent tetrodotoxin does not affect the appearance of the AChR epsilon-subunit transcripts but prevents the reduction of the steady-state level of the AChR gamma-subunit transcripts and yields a reduced proportion of the adult type channels. Thus, activity seems to facilitate the switch from the embryonic to the adult phenotype of the AChR protein. The Sol 8 cell system might be useful to analyse further the genetic and epigenetic regulation of muscle fibre maturation in mammals.

Animals↗
PubMed1991

Seven novel Tay-Sachs mutations detected by chemical mismatch cleavage of PCR-amplified cDNA fragments.

Total RNA was isolated from cultured fibroblasts from 12 unrelated patients with Tay-Sachs disease, an autosomal recessive disorder due to beta-hexosaminidase A deficiency. beta-Hexosaminidase mRNA was amplified by cDNA-PCR in four overlapping segments spanning the entire coding sequence. In two patients, abnormal size cDNA-PCR fragments in which exons were removed resulted from splicing mutations that were characterized at the genomic DNA level: both were G to A transitions, at the first position of intron 2 and at the fifth position of intron 4. Five other mutations have been identified by cDNA-PCR chemical mismatch analysis and direct sequencing of an amplified fragment containing the mismatch site. One missense mutation alters the codon for Ser210 to Phe in exon 6 and the other one alters the codon for Arg504 to Cys in exon 13. A 3-bp deletion results in the deletion of a phenylalanine residue in exon 8. Two nonsense mutations in exon 3 (Arg137 to stop) and in exon 11 (Arg393 to stop) are associated with a marked decrease of mRNA abundance, probably because they result in mRNA instability. Three of the six single base mutations involve the conversion of a CpG dinucleotide in the sense strand to TpG. These results demonstrate the extreme molecular heterogeneity of mutations causing Tay-Sachs disease. The procedure described in this paper allows the rapid detection of any type of mutation, except those impairing the promoter function. Applicable even to patients with splicing or nonsense mutations and very low mRNA abundance, it has therefore a potentially broad application in human genetics, for both diagnostic and fundamental purposes.

Base Sequence↗
PubMed1991

Immunolocalization and developmental expression of dystrophin related protein in skeletal muscle.

Dystrophin Related Protein is the recently identified protein product of a large autosomal transcript, showing significant similarity to dystrophin at the carboxyl terminus. Dystrophin related protein and dystrophin share a similar abundance and molecular weight, however, they differ both in their tissue distribution and expression in Duchenne/Becker muscular dystrophy. Here we define the immunolocalization of dystrophin related protein to neuromuscular and myotendinous junctions, along with peripheral nerves and vasculature of skeletal muscle. Groups of regenerating muscle fibres as well as embryonic and neonatal muscle express far greater amounts of dystrophin related protein compared with adult mdx mice. These findings may explain the paradoxical labelling seen using dystrophin antibodies in Duchenne patients and dystrophin deficient mdx mice. Finally, no abnormalities of dystrophin related protein expression were detected in three patients with Duchenne-like autosomal recessive muscular dystrophy.

Animals↗
PubMed1991

Illegitimate transcription. Application to the analysis of truncated transcripts of the dystrophin gene in nonmuscle cultured cells from Duchenne and Becker patients.

We have previously demonstrated that there is a low level of transcription of tissue-specific genes in every cell type. In this study, we have taken advantage of this phenomenon, called illegitimate transcription, to analyze the muscle-type dystrophin mRNA in easily accessible cells such as lymphoid cells, fibroblasts, and peripheral blood cells from Duchenne and Becker muscular dystrophies with known internal gene deletion. The results showed that, in the studied regions surrounding the deletions, processing of truncated transcripts is identical in specific (muscle tissue) and in nonspecific cells (lymphoid cells). In Becker cases with out-of-frame deletions, the already described alternatively spliced species found in muscle samples were also found in nonspecific cells. These results demonstrate that illegitimate transcripts are a bona fide version of tissue-specific mRNA, and that they represent a useful material to investigate the qualitative consequences of gene defects at the mRNA level.

Base Sequence↗
PubMed1991

Developmental patterns in the expression of Myf5, MyoD, myogenin, and MRF4 during myogenesis.

By using the polymerase chain reaction to amplify specific regions of the respective cDNAs, we have studied the expression of genes encoding the myogenic regulatory factors Myf5, MyoD, Myogenin, and MRF4 (Myf6, herculin) in cultured mouse muscle cells (inducible and permissive C2 cells and Sol8 cells). These cell lines may represent distinct stages in the progression of determined, or committed, muscle cells toward terminal differentiation. Transcripts for Myf5 were detected at the myoblast stage in all the committed muscle cells tested. Expression of the gene for MyoD appeared to be optional at the myoblast stage (MyoD is present in permissive myoblasts and absent from inducible myoblasts) but, like Myogenin, was found to accompany terminal differentiation. Furthermore, forced expression of MyoD converted inducible C2 cells into permissive cells. Expression of MRF4 was found to follow expression of the three other factors and to occur after the onset of terminal differentiation. Of particular interest was the finding that expression of MRF4 was temporally correlated with expression of the gene for the acetylcholine receptor epsilon-subunit that is characteristic of the adult receptor. In vivo, the only transcripts for myogenic regulatory factors to be detected in 8-day mouse embryos were those for Myf5, while expression of MRF4 followed expression of Myf5, MyoD, and Myogenin in developing limbs. Temporal and phenotypic differences related to the expression of Myf5, MyoD, Myogenin, and MRF4 suggest that these factors fulfil distinct roles in the control of myogenesis.

Animals↗
PubMed1990

Effect of dystrophin gene deletions on mRNA levels and processing in Duchenne and Becker muscular dystrophies.

Muscle dystrophin mRNAs from Duchenne (DMD) and Becker (BMD) patients with internal deletion of the DMD gene were quantitated and sequenced. In all cases (eight DMD and three BMD), truncated mature transcripts were found, and their amount was correlated to the clinical phenotype and to the reading frame. We focused on four cases that were apparently not in agreement with the reading frame rule. In two DMD cases, slightly reduced amounts of in-frame truncated mRNA are present but no dystrophin is detected, suggesting impaired translation and/or instability of the protein. In two BMD patients with out-of-frame deletions, the presence of minor in-frame alternatively spliced mRNA species is congruent with the observed truncated dystrophin and the mild phenotype.

Base Sequence↗
PubMed1990

A "G" to "A" mutation at position -1 of a 5' splice site in a late infantile form of Tay-Sachs disease.

Tay-Sachs disease is an autosomal recessive genetic disease caused by a deficiency in beta-hexosaminidase A. We have characterized a new mutation in a Tunisian patient displaying a late infantile form of Tay-Sachs disease. Northern blot analysis of patient's fibroblast total RNAs shows a broad, fast migrating band in the region of the normal beta-hexosaminidase alpha transcripts. The mRNA coding for beta-hexosaminidase alpha subunit was first reverse transcribed and then amplified in four overlapping segments spanning the entire coding sequence by polymerase chain reaction. We found in the products of polymerase chain reaction (PCR) that amplify the segment spanning exons 2-7, in addition to a normal fragment, two smaller size fragments, one of which is also seen in normal control fibroblasts. The analysis of the patient's specific abnormal fragment by hybridization with exon-specific oligonucleotides and then sequencing allowed us to conclude that this fragment lacked exon 5. The other smaller species lacked exons 4 and 5 in both patient and normal control. The sequence of a genomic fragment containing exon 5 and of the patient's normal cDNA fragment spanning exons 2-7, revealed a point mutation G to A at the last nucleotide of exon 5. This mutation doesn't change the sense of the affected codon. Northern blot of patient's fibroblast poly(A+) RNAs allowed us to quantify two of the forms of transcripts seen by PCR. In the patient, the normal size transcript and the exon 5-deleted transcript represent, respectively, 3 and 7% of the normal control beta-hexosaminidase alpha mRNA. We propose that this point mutation is responsible for an inefficient and abnormal processing of the mutant transcript resulting in the appearance of two low abundance spliced mRNAs. One is lacking exon 5 and most likely codes for an inactive protein; the other is similar to normal beta-hexosaminidase alpha mRNA, except for the presence of the silent G to A mutation and codes therefore for a normal enzyme accounting for the 2.5% residual beta-hexosaminidase A activity measured in patient's fibroblasts by a fluorometric assay. The third form, without exons 4 and 5, is also evidenced in normal fibroblasts by PCR so that we think that it is not related to Tay-Sachs disease.

Adenine↗
PubMed1990

Dystrophin gene transcribed from different promoters in neuronal and glial cells.

It has been shown that the dystrophin gene, which is defective in patients with Duchenne and Becker muscular dystrophy (reviewed in ref. 1), is transcribed in brain from a specific promoter that is different from the one used in muscle, and so the two types of transcripts differ at least in their first exon. We recently found that the dystrophin gene is expressed at a higher level in primary cultures of neuronal cells than in astro-glial cells derived from adult mouse brain. Here we investigate the use of two different promoters in each cell type. Our results demonstrate that the brain-type promoter of the dystrophin gene is highly specific to neurons, in which there is a significant increase in the amount of brain-specific messenger RNA during the course of in vitro maturation. By contrast, the muscle-type promoter is active in a wider range of cell types, including not only striated and smooth muscle, but also glial cells to a lesser extent, and probably neurons.

Animals↗
PubMed1990

Quantitative estimation of minor mRNAs by cDNA-polymerase chain reaction. Application to dystrophin mRNA in cultured myogenic and brain cells.

Amplification of the mRNA polymerase chain reaction is a very sensitive technique to detect low-abundance transcripts. We describe in this paper conditions necessary to make this technique quantitative. Quantification is performed in the exponential phase of the amplification process and the results are standardized with respect to those obtained with an exogenous mRNA which is co-reverse-transcribed and co-amplified in the same reaction as the analyzed transcripts. The primers are chosen in different exons to distinguish the amplification of mRNA fragments from the amplification of contaminating DNA. Analysis of the kinetics of amplification and parameters influencing this kinetics shows that: (a) in the exponential phase of amplification, the amount of amplified fragments is proportional to the initial amount of transcripts; (b) in a certain range of length fragment, the yield of amplification is inversely proportional to the length of the amplified fragments. Using this method we have demonstrated that the dystrophin gene is already activated at the myoblastic stage. A quantitative estimation of the transcript showed that the expression of this gene increases strongly in the course of in vitro myogenesis. In primary culture of mouse brain cells, the dystrophin gene was found to be more expressed in neuronal than in glial cells.

Animals↗
PubMed1989

Expression of MyoD1 coincides with terminal differentiation in determined but inducible muscle cells.

We have examined the expression of MyoD1, a potential determination factor of myogenic cells, in permissive and inducible C2 myoblasts. These two types of myoblasts exhibit distinct requirements to undergo terminal differentiation. Unlike permissive cells, inducible cells fail to differentiate in the presence of growth medium plus fetal calf serum and require insulin to undergo terminal differentiation. We show that while expression of MyoD1 is constitutive in permissive cells, no trace of MyoD1 transcripts is found in inducible cells at the myoblast stage. In these cells, however, expression of MyoD1 accompanies differentiation. This indicates that MyoD1 may not be required for the maintenance of the myoblast phenotype, and could act as an effector of terminal differentiation in already determined muscle cells. Our results provide new evidence that permissive and inducible cells represent two distinct stages of the progression of determined muscle cells toward terminal differentiation.

Autoradiography↗
PubMed1989

Analysis of molecular deletions with cDNA probes in patients with Duchenne and Becker muscular dystrophies.

In the course of a systematic survey of DMD and BMD patients with intronic probes and with cDNA probes covering three-fourths of the coding sequence, 45 molecular deletions within the DMD gene were investigated. Forty-two percent of the breakpoints were located in the intronic sequence containing probe P20, whereas the other deletions were widespread around the more proximal part of the gene. Most of the BMD deletions were in the P20 region. Pulsed field gel electrophoresis was used to determine the size of some deletions and allowed us to estimate the physical distance between the intronic probes JBir and P20. The reading frame was checked in 11 cases with proximal deletions and found to be disrupted in 6 of 7 DMD patients, in 1 intermediate case, and, unexpectedly, in 3 BMD patients.

Adolescent↗
PubMed1989

Illegitimate transcription: transcription of any gene in any cell type.

Using in vitro amplification of cDNA by the polymerase chain reaction, we have detected spliced transcripts of various tissue-specific genes (genes for anti-Müllerian hormone, beta-globin, aldolase A, and factor VIIIc) in human nonspecific cells, such as fibroblasts, hepatoma cells, and lymphoblasts. In rats, erythroid- and liver-type pyruvate kinase transcripts were also detected in brain, lung, and muscle. The abundance of these "illegitimate" transcripts is very low; yet, their existence and the possibility of amplifying them by the cDNA polymerase chain reaction provide a powerful tool to analyze pathological transcripts of any tissue-specific gene by using any accessible cell.

Animals↗
PubMed1989

The molecular basis for Duchenne versus Becker muscular dystrophy: correlation of severity with type of deletion.

About 60% of both Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) is due to deletions of the dystrophin gene. For cases with a deletion mutation, the "reading frame" hypothesis predicts that BMD patients produce a semifunctional, internally deleted dystrophin protein, whereas DMD patients produce a severely truncated protein that would be unstable. To test the validity of this theory, we analyzed 258 independent deletions at the DMD/BMD locus. The correlation between phenotype and type of deletion mutation is in agreement with the "reading frame" theory in 92% of cases and is of diagnostic and prognostic significance. The distribution and frequency of deletions spanning the entire locus suggests that many "in-frame" deletions of the dystrophin gene are not detected because the individuals bearing them are either asymptomatic or exhibit non-DMD/non-BMD clinical features.

Adolescent↗
PubMed1988

Transcription of the dystrophin gene in human muscle and non-muscle tissue.

The gene that is defective in patients with Duchenne and Becker muscular dystrophy consists of about 60 short exons scattered along a gigantic DNA region that spans some 2 megabase pairs. The encoded protein, dystrophin, was recently characterized as a component of muscle intracellular membranes of low abundance. The dystrophin messenger RNA is difficult to study in both normal and pathological tissue specimens because it is large (14 kilobases) and scarce (0.01-0.001% of total muscle mRNA). We report here that efficient in vitro co-amplifications of the mRNAs of the dystrophin gene and of a reporter gene, aldolase A, by the polymerase chain reaction procedure enables us to obtain a quantitative estimate of the dystrophin gene transcript. A processed, transcribed segment was thus detected in 13 different human tissues. It ranged from 0.02-0.12% of total mRNA in skeletal muscle to 25,000 times less in lymphoblastoid cells.

Brain Chemistry↗
PubMed1988

Deletion proximal to DXS68 locus (L1 probe site) in a boy with Duchenne muscular dystrophy, glycerol kinase deficiency, and adrenal hypoplasia.

We report a case of a boy with Duchenne muscular dystrophy (DMD) associated with GK deficiency (GK), congenital adrenal hypoplasia (AHC), and mental retardation. Cytogenetic analysis of prometaphasic chromosomes revealed an interstitial chromosome deletion at Xp21.2 possibly extending to Xp21.1 or Xp21.3. His phenotypically normal mother was heterozygous for this deletion. DNA probe analysis on Southern blots showed that the deletion affected the following probe sites: 754, pERT 84, 21A, XJ2.3, pERT 87, JBir, and J66-H1, whereas L1, C7, and CX5.4 probes gave a normal signal. Pulse field gel electrophoresis after SfiI digestion did not show abnormal fragments with L1. These data are consistent with a deletion of about 4 megabases and indicate that the GK and AHC loci are proximal to L1 and distal to J66-H1.

Adrenal Insufficiency↗
PubMed1987

Familial deletion of Xp21.2 with glycerol kinase deficiency and congenital adrenal hypoplasia.

Congenital adrenal hypoplasia (CAH) and glycerol kinase deficiency (GKD) were diagnosed in a male during the neonatal period. On prometaphase chromosomes there was an interstitial deletion involving Xp21.2 and possibly Xp21.3 in the propositus and his mother. Duchenne muscular dystrophy (DMD) was excluded on the basis of normal serum creatine kinase and a muscle biopsy. Molecular hybridization of DNA from the propositus with 11 probes covering Xp21, including the DMD locus, was normal. In situ hybridization with the probe pERT87.15 showed a normal signal at the expected site indicating that the DMD locus was preserved and not translocated. This suggests that the DMD locus is located at the most proximal part of the sub-band Xp21.2 or in Xp21.1, and that the DXS68 (probe L1) is far from it on the distal flanking DNA.

Adrenal Insufficiency↗