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.

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.

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.

Diversity and differential distribution of IS231, IS232 and IS240 among Bacillus cereus, Bacillus thuringiensis and Bacillus mycoides

Bacillus cereus, Bacillus thuringiensis and Bacillus mycoides are very closely related bacteria, generally considered as subspecies of B. cereus sensu lato. Different transposable elements have been isolated from B. thuringiensis, including IS231, IS232 and IS240 and their variants. The distribution of these three insertion sequences (IS) within the B. cereus group has been investigated in 90 strains of B. thuringiensis (representing 61 serovars), in 30 reference strains of B. cereus and in 33 strains of B. mycoides. Since these IS elements are delimited by well-conserved and specific inverted repeats, the use of primers corresponding to these ends allowed their amplification by PCR. The results showed that IS231 is the most abundant element in the three taxa, whereas IS232 is apparently exclusively associated with B. thuringiensis. Hybridization and Dral RFLP analysis of the PCR products confirmed and extended knowledge of the heterogeneity previously observed among iso-IS231 elements. Moreover, a similar diversity was observed among iso-IS240 elements. This contrasted with the relative homogeneity displayed by iso-IS232 elements. No specific association appeared to exist between any particular iso-element and a specific strain or serotype.

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.

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.

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.

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.

[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.

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.

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.

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.

[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.

A new method for automatic metaphase finding adaptable to different chromosome preparations

A FORTRAN computer program, running on a Digital PDP 11-34 minicomputer, has been developed for use in conjunction with a Cambridge Quantimet 720 image analyzer for the investigation of metaphase preparations in routine cytogenetics. During a short initiation phase the program is adapted to the type of metaphase being analyzed. The program is fast and its performance is good, even at low microscopic magnifications. It has other uses in biology for all investigations and characterizations of small distinct elements widely spread within a preparation (e.g., autoradiography, bacteriology).

[Partial monosomy due to long-arm deletion of chromosome 11 : del (11) (q23) (author's transl)]

A girl, who died at 25 days of age, was found to have a partial monosomy due to a 11q23 leads to 11qter deletion. The main clinical findings were trigonocephay, facial dysmorphia, and congenital heart disease. A review of developmental and dysmorphic features of the seventeen recognized cases is presented.

Male sterility associated with familial translocation heterozygosity: t(8;15) (q22;p11)

During the investigation of the family of a subject consulting for primary sterility, the same oligoteratospermia was found in two of his brothers. The three karyotypes of these subjects exhibited an equilibrated reciprocal autosomal translocation t(8;15) (q22;p11), which was also detected in their mother. The karyotypes of the remaining siblings, one brother and one sister, were normal. The semen analysis of the sterile subjects suggests that the block of gamete production occurs at the beginning of spermiogenesis. The chromosomal anomaly, which has no effect on the reproduction of the mother, leads to sterility of the male offspring bearing it.

An automatic system for chromosomal analysis applied to prenatal diagnosis

Computer-assisted metaphase analysis for prenatal diagnosis can be economically performed by a preexisting hardware-software system. The program can be run by technician-level (i.e. nonspecialist) personnel who can opt for the automatic operational mode for good quality metaphases or for the semimanual mode for problem metaphases (numerous superpositions, artifacts, etc.). The karyotype can be obtained in conversational mode. Hardcopy output is available for all modes.

[Measurement of the position and intensity of chromosomal denaturation bands by an automatic system]

The band density profile of a marked chromosome was obtained using a photodiode collector combined with a minicalculator, working with an ordinary photographic document. The measurement was carried out over 10 to 20 300-point lines oriented longitudinally along the chromosome. The profile obtained corresponds to the sum of the values of each of these lines. The proposed systems's originality resides in its ability to determine the position and intensity of a band over the entire thickness of the chromosome.

Association of pericentric inversion of chromosome 9 and reproductive failure in ten unrelated families

A pericentric inversion of chromosome 9 has been detected in 10 unrelated families. The break points are identical and the inversions involved the heterochromatic segment. The effects of inversion of chromosome 9 on different aspects of reproductive failure are discussed.