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M Khrestchatisky

Publications and source records attributed to M Khrestchatisky.

51 records · Page 3Linked to original sources
PubMed1994

Cloning and expression of the murine homologue of a putative human X-linked nuclear protein gene closely linked to PGK1 in Xq13.3.

Several human inherited diseases have been localized to the Xq13.3 region of the human X chromosome (X-linked dystonia with Parkinsonism, sideroblastic anemia, SCID, Menkes disease and X-linked mental retardation loci). Genes involved in the phenotypes have been isolated for only two of them (Menkes and SCIDX). It was therefore interesting to isolate and characterize new genes from the region. In a previous work (12 and Consalez et al, in preparation) we isolated a gene (XNP), located 350 Kb proximal to PGK1, potentially coding for a nuclear protein. We describe here the cloning and characterization of the murine homologue. The pattern of expression of the gene in the newborn mouse (especially the expression in particular regions of the brain: optical lobe, frontal cortex, hippocampus and cerebellum), as well as the expression in human tissues, suggests that this gene might be involved in neuronal differentiation. Among the different morbid phenotypes assigned to the region, X-linked mental retardation would be the best candidate to be associated with this gene.

Amino Acid Sequence↗
PubMed1994

Complete sequence of rat MAP2d, a novel MAP2 isoform.

MAP2 proteins are among the major microtubule-associated proteins in the vertebrate nervous system. The high molecular weight proteins MAP2a, MAP2b and the low molecular weight protein MAP2c are encoded by distinct mRNAs generated by alternative splicing from the same primary transcript. MAP2c is primarily found in embryonic and neonatal brain. Using primers selected in the 5' and 3' non-coding regions of the rat MAP2c sequence and reverse transcription-coupled PCR from adult rat brain RNA, we have amplified and sequenced the entire coding region of a novel MAP2 isoform containing a 93 base pair insertion. Sequence analysis reveals that the additional exon encodes a domain that is highly homologous to repeats found in the 3' end of the coding region of MAP2, MAP4 and Tau mRNA sequences. In these microtubule-associated proteins, the domains encoded by the repeats are involved in microtubule binding and bundling.

Animals↗
PubMed1993

Mossy fiber sprouting in epileptic rats is associated with a transient increased expression of alpha-tubulin.

Kainate-induced seizures lead to marked increases of alpha-tubulin mRNA and protein immunoreactivity in the rat dentate gyrus. The increase in alpha-tubulin mRNA was restricted to the granule cell bodies. alpha-Tubulin immunoreactivity was enhanced in granule cell dendrites and axons (the mossy fibers), in the molecular layer. These changes peaked 6-12 days after kainate treatment and preceded the collateral sprouting of mossy fibers which occur 12 to 30 days after seizures. The present results suggest that microtubule formation contributes to the synaptic rearrangements which take place in the hippocampus after seizures.

Amygdala↗
PubMed1993

Alterations of the GluR-B AMPA receptor subunit flip/flop expression in kainate-induced epilepsy and ischemia.

In the hippocampus, glutamatergic pathways are altered following seizure activity or transient global ischemia, both pathological conditions leading to selective neuronal degeneration. Glutamatergic receptors, and notably alpha-amino-3-hydroxy-5-methyl-4-isoxazolopropionate (AMPA) receptors, a family of glutamate receptors involved in fast synaptic transmission and in the maintenance of synaptic potentiation may play an important role in the pathological outcome. AMPA receptors are assembled from GluR-A, GluR-B, GluR-C and GluR-D polypeptides which exist in flop and flip variants, the latter allowing larger glutamate responses. Using in situ hybridization techniques, we show that kainate-induced epilepsy provokes a rapid but transient increase (50%) of GluR-B flip mRNA levels in all subregions of the hippocampus (CA1, CA3, dentate gyrus). This early phase is followed by a second, persistent GluR-B flip increase in regions in which neurons are known to be seizure-resistant (i.e. CA1 an dentate gyrus) while a 35% decrease is observed in the vulnerable CA3 area. Following global ischemia, the levels of GluR-B flip and flop variants are dramatically reduced (90-100%), well before any morphological signs of cell death, in the subiculum and CA1, two areas known to be particularly sensitive to ischemic insult. In keeping with the properties of GluR flip variants, it is suggested that altered subunit stoichiometry may lead to long-lasting enhanced efficiency of fast synaptic transmission in the epileptic hippocampus. Since GluR-B containing receptors are Ca2+ impermeable, our results also suggest altered Ca2+ permeability in the vulnerable pyramidal neurons of areas CA3 and CA1 in the epileptic and ischemic hippocampi, respectively.

Animals↗
PubMed1993

Transient expression of the NR2C subunit of the NMDA receptor in developing rat brain.

Pharmacologically distinct NMDA-glutamate receptor subtypes have been reported in brain. We have studied the developmental expression of the mRNA encoding the NMDA receptor NR2C subunit in the rat brain by in situ hybridization. In contrast with the adult where no hybridization signal was detected in the hippocampus, a significant signal was seen in this formation during a restricted developmental period (P7-P14). The labelling covered large parts of the hippocampus including in particular the stratum radiatum, pyramidal and oriens layers of the CA1 area. The role of the NR2C subunit in neonatal NMDA receptor properties is discussed.

Animals↗
PubMed1993

Basic fibroblast growth factor-induced increase in zif/268 and c-fos mRNA levels is Ca2+ dependent in primary cultures of hippocampal neurons.

Basic fibroblast growth factor (bFGF) is present in the developing rat brain and has been shown to provide critical trophic support for hippocampal neurons in culture. The influence of bFGF on the expression of mRNAs encoding the transcription factors zif/268 and c-fos was studied in primary cultures of hippocampal neurons (derived from rat embryos) using reverse transcription-coupled PCR. In these cultures grown for 3 days in the absence of serum, bFGF causes a dramatic and transient increase in the levels of zif/268 and c-fos, within 15 and 30 min, respectively. A similar induction of these two early genes occurs following activation of protein kinase C (PKC). The bFGF-induced activation persists after PKC desensitization but is inhibited by chelation of intracellular Ca2+. These results suggest that in primary cultures of hippocampal neurons, bFGF induces the expression of immediate early genes through a pathway that requires Ca2+ mobilization.

Animals↗
PubMed1993

Glutamate-induced neuronal death is not a programmed cell death in cerebellar culture.

Activation of programmed cell death has recently been suggested to be involved in the delayed neuronal death of CA1 hippocampal neurons after global ischemia based on protection offered by protein synthesis inhibitors. Here, we studied the effects of transcriptional (actinomycin D) and translational (cycloheximide and anisomycin) inhibitors on glutamate-induced neuronal death in cerebellar granule cell cultures. The effects of aurintricarboxylic acid, an endonuclease inhibitor, were studied as well. No protection against glutamate toxicity could be observed with any of these inhibitors. We also analyzed the genomic DNA of glutamate-treated cells on agarose gel electrophoresis. No DNA degradation could be observed after glutamate exposure. We conclude that glutamate-induced neuronal death does not exhibit the features of apoptosis in cultured granule cells.

Animals↗
PubMed1992

Isolation and cloning of a voltage-dependent anion channel-like Mr 36,000 polypeptide from mammalian brain.

A polypeptide of M(r) 36,000 (36 kDa) was isolated from detergent-solubilized membrane fractions of mammalian brain on a benzodiazepine affinity column utilized for the purification of the gamma-aminobutyric acid/benzodiazepine receptor protein, followed by preparative gel electrophoresis. Partial protein sequence for two fragments of the 36-kDa polypeptide allowed the isolation of cDNA clones from a rat hippocampal library. An open reading frame coding a sequence of 295 amino acid residues containing the two probe peptide sequences with minor differences, and a putative N-terminal signal peptide of 25 residues was found. Hydropathy index revealed no regions of alpha-helix suitable for membrane spanning, but several areas of alternating hydrophilic and hydrophobic residues consistent with beta-strands. The sequence of this brain protein was 24% identical to that of a yeast mitochondrial protein, the voltage-dependent anion channel (VDAC), and over 70% identical with the VDAC from human B lymphocytes. The gamma-aminobutyric acid type A (GABAA) receptor/36-kDa preparation purified on benzodiazepine affinity column has channel-forming activity in lipid bilayer membranes that is virtually identical to VDAC isolated from mitochondria of various sources, indicating that the 36-kDa protein is a new member of the VDAC family of proteins. An antiserum raised against the purified 36-kDa polypeptide was able to precipitate [3H]muscimol binding activity, indicating a tight association with the GABAA receptor protein in vitro and copurification on the benzodiazepine affinity column due to this association. Further studies are needed to determine whether such an association occurs in vivo.

Amino Acid Sequence↗
PubMed1991

Independent cellular and ontogenetic expression of mRNAs encoding three alpha polypeptides of the rat GABAA receptor.

Previous studies have shown that several distinct but related polypeptides can serve as alpha subunits of functional GABAA receptors. Furthermore, the diversity of these polypeptides at least partially accounts for the functional heterogeneity of GABAA receptors. In this paper, we report the results of in situ hybridization studies using probes derived from our recently reported cDNAs for alpha 1, alpha 2, and alpha 4 GABAA receptor polypeptides. We show that the mRNAs that encode these isoforms have distinct regional and cellular distributions and are present at widely varying levels within the rat brain. In addition, our Northern blot analyses indicate that each of these three alpha mRNAs has a distinct pattern of ontogenetic regulation. Differential regulation of alpha polypeptide isoforms may lead to changes in GABAA receptor function during ontogeny as well as to distinct cellular responses to GABA and GABA-related drugs.

Animals↗
PubMed1991

Sequence and regional distribution of the mRNA encoding the alpha 2 polypeptide of rat gamma-aminobutyric acidA receptors.

A cDNA from a rat hippocampal cDNA library encodes an isoform of the alpha polypeptide of the gamma-aminobutyric acid (GABA)/benzodiazepine (BZ) receptor. Its deduced amino acid sequence is 96% identical to that of the alpha 2 polypeptide of the bovine GABAA receptor. The polypeptide has features shared by all previously reported GABAA receptor alpha polypeptides and shares 71-76% identity with previously described rat alpha polypeptides. Most of the differences lie in the presumed extracellular and intracellular domains. On Northern blots, the alpha 2 cDNA detects two mRNAs, which are found in cortex, hippocampus, and striatum, brain regions enriched in pharmacologically defined "BZ type II" receptors. Other workers have previously shown that the alpha polypeptides of the GABAA receptor largely determine the BZ binding properties of reconstituted receptors. The distribution of alpha 2 mRNAs in rat brain suggests that the alpha 2 subunit may indeed be involved in the BZ type II receptors.

Animals↗
PubMed1989

A novel alpha subunit in rat brain GABAA receptors.

Two cDNAs (alpha 1 and alpha 4) from rat brain cDNA libraries encode isoforms of the alpha subunit of the GABA/benzodiazepine receptor, which differ at 30% of their amino acid residues. Northern blot analysis and in situ hybridization histochemistry show that alpha 1 and alpha 4 mRNAs have distinct sizes and distinct regional and cellular distributions in rat brain: both mRNAs are found in the cortex and hippocampus; however, only the alpha 1 mRNA is detected in the cerebellum. We injected RNA transcribed from alpha 1 and alpha 4 cDNAs into Xenopus oocytes, together with an RNA for a rat beta subunit. We obtained GABA-dependent inward currents that were reversibly blocked by picrotoxin. Picrotoxin alone, applied to oocytes producing the alpha and beta polypeptides, elicited an outward current. We suggest that these polypeptides together produce GABA-gated ion channels that can also open spontaneously.

Amino Acid Sequence↗
PubMed1988

Expression of muscle actin genes in early differentiation stages of tail regeneration of the urodele amphibian Pleurodeles waltlii.

Amputation of the tail of the amphibian Pleurodeles waltlii leads to the formation of a blastema composed of undifferentiated cells during the first stages of regeneration. Between the 3rd and 4th week following amputation, the first fully differentiated striated muscle cells appear, and in the 6th week myogenic differentiation extends throughout the regenerate. Myoblasts appear in cell patches where cells fuse as differentiation proceeds. Using a cloned cDNA probe to a striated muscle actin gene specifically expressed in adult skeletal muscle, we show that no corresponding mRNA remains during dedifferentiation. A new actin transcript of the same length as cardiac actin transcript appears in the 4th week after amputation. We conclude that for the myogenic cell line, differentiation in the regenerate is accompanied by an actin isoform transition similar to that seen in embryonic terminal differentiation of higher vertebrates.

Actins↗
PubMed1987

There is an alpha-actin skeletal muscle-specific gene in a salamander (Pleurodeles waltlii).

We cloned, from a cDNA library, an alpha-actin sequence from a salamander (Pleurodeles waltlii), which codes for the 125 COOH-terminal amino acid residues of a skeletal muscle actin (without any difference from the corresponding protein of warm blood vertebrates). An important conservation in the 3' untranslated region between this sequence and skeletal alpha-actin genes of chicken and man was noted. These results demonstrate, contrary to what was thought previously, that there exists in salamander a true skeletal alpha-actin gene. The results suggest that striated muscle actin genes in lower vertebrates could be a mosaic of cardiac and skeletal-specific amino acid residues, and that the divergence between these two types of genes is older than the NH2-terminal analysis of actins suggested previously.

Actins↗