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C Léonard

Publications and source records attributed to C Léonard.

At least 19 recordsLinked to original sources
PubMed2000

Spurious monosomy 7 in leukemia due to centromeric heteromorphism.

We report heteromorphism of the centrometric region of human chromosome 7, which was observed in the cytogenetic assessment of a complete remission of a pre-B acute lymphoblastic leukemia in the bone marrow cells of a 25-year-old woman. Classical cytogenetic study was performed, as well as metaphase and interphase fluorescence in situ hybridization (FISH) carried out with an alphoid DNA probe specific for the chromosome 7 centromere for detection of leukemic clones with monosomy 7 found at the initial diagnosis. We show an important centromeric heteromorphism of this chromosome detected by FISH and clearly visible on all metaphases and nuclei analyzed. This heteromorphism is observable as a fluorescent signal five- or sixfold larger than that on the homologue. To our knowledge, this heteromorphism of chromosome 7 has not been reported in the literature. However, with the use of FISH analysis, it could be easily mistaken for a mosaicism of monosomy 7, which can be misleading in the interpretation of the results.

Adult↗
PubMed1999

MIC231, a naturally occurring mobile insertion cassette from Bacillus cereus.

Recent dissection of numerous plasmids and transposable elements has given more credence to the modular organization of these genetic and genomic entities. Although many variations on each theme exist, the number of basic functional cassettes is thought to be relatively limited. In this paper, a novel type of mobile cassette is described. A naturally occurring assemblage consisting of two left IS231 ends flanking a D-stereospecific endopeptidase (adp) gene was found in several natural isolates of Bacillus cereus. This 1.9 kb genetic entity was shown to transpose in the presence of IS231A transposase, not only in Escherichia coli but also in Bacillus. The acronym MIC231 is proposed for this mobile insertion cassette trans-activated (teletransposed) by IS231. Using (D-Phe)4 tetrapeptide as substrate, the endopeptidase activity of the MIC231 adp gene could be demonstrated in E. coli and B. subtilis. Interestingly, this D-stereospecific endopeptidase activity was not limited to the original B. cereus isolates but was also detected in all but one of the 69 B. cereus sensu lato strains tested, indicating its important, yet dispensable, biological function. However, inactivation of the MIC231 adp gene in two B. cereus strains did not result in any detectable variation of their activity on (D-Phe)4, suggesting the presence of other distantly related adp gene(s). Thus, although the exact role of MIC231 adp remains elusive, its presence inside a mobile cassette represents the archetype of a novel insertion sequence modular organization.

Bacillus cereus↗
PubMed1998

IS231A transposition: conservative versus replicative pathway.

This paper describes a novel approach, based on suicide transposition, to addressing the question of whether IS231A can give rise to cointegrate molecules through replicative transposition, even at a very low frequency. Comparative analysis was carried out with IS 10, another member of the same IS4 family. The results indicate that transposition of both elements is exclusively conservative.

Bacillus subtilis↗
PubMed1998

Integrated physical and genetic mapping of Bacillus cereus and other gram-positive bacteria based on IS231A transposition vectors.

The genome structure of Bacillus cereus is relatively complex, its DNA being modulated between a size-varying chromosome and large plasmids. To study the genetic organization of the B. cereus type strain ATCC 14579, thermosensitive transposition vectors were designed on the basis of IS231A-derived cassettes containing uncommon restriction sites. A highly preferred insertion site for IS231A was detected in the chromosome by Southern blotting and pulsed-field gel electrophoresis (PFGE) analyses of independent insertion mutants. However, once this insertional hot spot was occupied, secondary IS231A insertions occurred randomly, as demonstrated by isolation of independent B. cereus auxotrophs at a frequency of approximately 0.6%. The hot-spot site, as well as several auxotrophic mutations, were mapped by using NotI, SfiI, and AscI PFGE restriction profiles. It was confirmed by sequencing that one of the insertions, generating an Ade- phenotype, had disrupted a gene of the purine synthesis pathway. These results showed that combined PFGE and sequencing analyses of mini-IS231A insertions enable the construction of integrated physical and genetic maps of B. cereus type strain. Moreover, the presence of the ultrarare I-SceI restriction site in the mini-IS231A allowed the isolation, in double-insertion mutants, of contiguous and nonoverlapping large chromosomal fragments, convenient for direct sequencing. The system detailed in this report is therefore a powerful tool for comparative genetic studies among members of the B. cereus group (i.e., B. cereus, B. thuringiensis, B. mycoides, and B. anthracis) and could also be applied to more distantly related gram-positive bacteria.

Bacillus cereus↗
PubMed1997

New ultrarare restriction site-carrying transposons for bacterial genomics.

Electrophoretic separation of macrorestriction fragments containing a particular genomic interval has until recently depended on fortuitously placed native rare restriction sites. We present new IS10-based transposons carrying the yeast intron-encoded I-SceI restriction site which is absent from most prokaryotic and eukaryotic genomes. Construction of the plasmid vectors containing them is described. Analysis by conventional or Pulsed Field gel electrophoresis of the DNA fragments generated by the I-SceI digestion reveals the physical distance between genomic insertions of these transposons: use of the same approach to subdivide the chromosome of Escherichia coli K-12 into equivalently sized contiguous/nonoverlapping I-SceI fragments is demonstrated. Because coordinates for the loci delimited by their insertions can be readily determined in different isolates by either physical or genetic manipulations, these transposons allow sufficient flexibility for species-wide bacterial genomics.

Animals↗
PubMed1997

Cloning and characterization of cspL and cspP, two cold-inducible genes from Lactobacillus plantarum.

Two cold shock genes, cspL and cspP, have been cloned from two Lactobacillus plantarum strains. These genes, which are nonallelic, were present in all strains tested. The genes encode 66-amino-acid polypeptides related to each other and to the cold shock Csp family. Transcription of cspP rendered a single mRNA, while two cspL mRNAs were found with common 5' ends. The amounts of these transcripts increased moderately upon exposure of the cultures to cold.

Acclimatization↗
PubMed1996

Additional translocation (9;12)(p13;q24.1) in newly diagnosed chronic myeloid leukemia: complete cytogenetic remission after interferon therapy.

We report the case of a patient with chronic phase CML who exhibited, in the same cells, beside the Philadelphia chromosome, an additional translocation between the other chromosome 9 and one of the chromosomes 12 [t(9;12)(p13;q24.1)]. Complete cytogenetic remission with disappearance of both karyotypic abnormalities was achieved after 18 months treatment with low dose (1.4 x 10(6) U/m2/day) recombinant alpha-interferon and has been sustained with maintenance therapy for 68+ months (actual follow-up). Clonality at diagnosis and recovery of polyclonal hematopoiesis in complete cytogenetic remission were demonstrated using the polymorphism at the human androgen receptor gene (Humara) locus on chromosome X. The role of the additional translocation in the response to low dose alpha-interferon therapy remains hypothetical.

Chromosome Banding↗
PubMed1995

Monosomy 21q: two cases of del(21q) and review of the literature.

We report on two cases of partial monosomy 21 and review cases with a partial or an apparently full monosomy 21. In situ hybridization and/or molecular studies appear to be necessary tools to study imbalance in such a small chromosome and to perform further genotype-phenotype correlations. The segregation mode in cases with a translocation is adjacent 1, adjacent 2, and 3:1 in about 1/4, 1/4 and 1/2 of the cases, respectively.

Child, Preschool↗
PubMed1993

[Myelodysplastic syndromes in children].

Myelodysplastic syndromes are clonal haemopathies known to exist in elderly people where they are classified into 5 categories: refractory anaemia, acquired idiopathic sideroblastic anaemia, refractory anaemia with excess of blasts, refractory anaemia with excess of blasts undergoing acute transformation, and chronic myelomonocytic leukaemia. Transformation into acute leukaemia is frequent. These syndromes seem to be rarer in children, but they are often misdiagnosed. Some of their forms are particular to childhood. They include association with constitutional blood diseases predisposing to acute leukaemia, or with congenital or non-congenital malformative syndromes; there are hypoplastic forms, forms evolving towards stabilization of haematological abnormalities, and border forms with certain myeloproliferative syndromes. The diagnosis of myelodysplasia rests on morphological, functional, biochemical, isotopic data reflecting inefficient haematopoiesis, and on cytogenetic data. Studies of clonality and malignancy markers will in the near future enable us to distinguish between true preleukaemic states and polyclonal constitutional or virus-induced myelodysplasias, probably more frequent in children. The choice of treatment depends on the severity of the myelodysplastic syndrome, defined by the initial partial blastosis, the presence of cytogenetic anomaly and the certainty of clonality. In cases with poor prognosis, early bone marrow allograft is the only possible treatment.

Child↗
PubMed1993

Acute lymphoblastic leukemia with trisomy 21 constitutional mosaicism.

Acute lymphoblastic leukemia was diagnosed in an 11-year-old girl with mild signs of Down's syndrome. She was known since birth to have a constitutional mosaicism (46,XX/47,XX,+21c). At initial diagnosis of acute leukemia, additional chromosome changes were found in bone marrow blasts: hyperdiploidy > 50, with a structural abnormality. She was treated with a standard chemotherapeutic protocol, and has remained in complete remission for more than 3 years. The constitutional mosaicism evolved toward normalization year after year in the blood and under the effect of chemotherapy in the bone marrow.

Child↗
PubMed1992

Trisomy 16p in a liveborn offspring due to maternal translocation t(16;21)(q11;p11) and review of the literature.

We report on a case of dup(16p) and review previous cases. The triplicated chromosome region leading to this specific syndrome lies in 16p13.1 p13.3. Most of the cases are inherited and the mode of segregation was found to be 3:1 in half of the cases, but these observations might be due to biases. The other chromosomes involved in the translocations as well as the breakpoints in these chromosomes do not appear to be random.

Abnormalities, Multiple↗
PubMed1992

[Genetic aspects of renal tumors in adults].

The aetiopathogenesis of adult renal tumors is poorly understood. The specific chromosomal changes detected by the study of tumor karyotypes suggest a cascade of oncogene activation and tumor suppressor gene inactivation in the course of renal carcinogenesis. These cytogenetic studies have isolated two entities: non-papillary carcinomas (clear cell and/or eosinophil carcinomas) and tubulopapillary tumors (cortical adenoma, basophil papillary carcinoma). Specific changes of the short arm of chromosome 3 are observed in 70 to 85% of cases of clear cell carcinomas, while trisomy 17 is detected in 70% of cases of tubulopapillary tumors. Cytogenetics is also able to distinguish low and high grade malignant tubulopapillary carcinomas. Limited data are available at the present time concerning oncocytomas.

Adenoma↗
PubMed1989

Inactivated X chromosome fold in human leukemia and related clonal disorders.

A disturbance of the X chromosome inactivation process has been demonstrated in some human tumors. In order to study this phenomenon in leukemia, the site of unusually frequent folding in Xq13-q21 was used as a morphological marker. A total of 858 GTG-banded mitoses from 61 women with different hematological malignancies were analyzed, 35 of them with normal karyotype and 26 with chromosome aberrations. The folding patterns and the fold percentage remained unchanged in our patients. Using this marker, X-inactivation could easily be verified in leukemia and related disorders on routine preparations.

Adolescent↗
PubMed1989

Low-dose arabinosyl cytosine therapy of AML may be effective after failure of high or conventional doses.

In 3 patients with ANLL, chemotherapy including high or conventional doses of Ara-C had been ineffective. However subsequent treatment with low-dose (LD) Ara-C induced a PR or CR which were sustained with regular LD Ara-C reinduction courses. Survival of the 2 patients with PR was 24 and 8 months respectively. The patient with CR was alive 18 months after a bone marrow graft. In 2/3 cases, the cytogenetic abnormalities initially detected disappeared with treatment. These observations suggest that the cellular mechanism of action of LD Ara-C is different from that of HD Ara-C, but do not favour a differentiating action of LD Ara-C. LD Ara-C can be prescribed as a salvage therapy even after failure of high or conventional doses.

Adult↗
PubMed1986

[Genetic aspects of artificial insemination. Choice of donors].

Artificial insemination with donors has genetic repercussions which increase with its impact on demography. Genetic control of semen donors offers a possibility of preventing the main genetic handicaps. The French Federation of Human Semen Study and Preservation Centres (CECOS) is currently organizing such a control system. The reasons for this and the modalities of the system are given in this article.

Female↗