Molecular characterization of 39 de novo sSMC: contribution to prognosis and genetic counselling, a prospective study.

Small supernumerary marker chromosomes (sSMCs) are structurally abnormal chromosomes that cannot be characterized by karyotype. In many prenatal cases of de novo sSMC, the outcome of pregnancy is difficult to predict because the euchromatin content is unclear. This study aimed to determine the presence or absence of euchromatin material of 39 de novo prenatally ascertained sSMC by array-comparative genomic hybridization (array-CGH) or single nucleotide polymorphism (SNP) array. Cases were prospectively ascertained from the study of 65,000 prenatal samples [0.060%; 95% confidence interval (CI), 0.042-0.082]. Array-CGH showed that 22 markers were derived from non-acrocentric markers (56.4%) and 7 from acrocentic markers (18%). The 10 additional cases remained unidentified (25.6%), but 7 of 10 could be further identified using fluorescence in situ hybridization; 69% of de novo sSMC contained euchromatin material, 95.4% of which for non-acrocentric markers. Some sSMC containing euchromatin had a normal phenotype (31% for non-acrocentric and 75% for acrocentric markers). Statistical differences between normal and abnormal phenotypes were shown for the size of the euchromatin material (more or less than 1 Mb, p = 0.0006) and number of genes (more or less than 10, p = 0.0009). This study is the largest to date and shows the utility of array-CGH or SNP array in the detection and characterization of de novo sSMC in a prenatal context.

A case of trisomy 12 mosaicism with pituitary malformation and polycystic ovary syndrome.

We report the case of a patient (followed from birth to 15 years) presenting with trisomy 12 mosaicism, and focus on the endocrine phenotype associating a pituitary malformation and ovarian abnormalities. We describe the dysmorphic features and their evolution, the growth retardation and ovarian symptoms. Complete growth hormone deficiency was confirmed on auxological data, stimulation test and was related to pituitary stalk interruption, diagnosed by magnetic resonance imaging. Effect of growth hormone treatment was satisfactory resulting in a normal adult height. She also presented premature thelarche associated with right ovarian hypertrophy (4 to 5 fold the volume of the left ovary) which remained constant until 15 years of age. Diagnosis of trisomy 12 mosaicism was made on skin and ovarian karyotypes. The possible relation between these endocine findings and some genes located on chromosome 12 involved in pituitary and ovarian development is discussed.

Association of the Philadelphia chromosome and 5q- in secondary blood disorder.

A patient developed a secondary blood disorder 7 years after radiotherapy for a gastric lymphoma. The initial myelodysplastic syndrome evolved to a myeloproliferative phase with transient polycythemia, progressive thrombocythemia, and hyperleukocytosis. Chromosome analysis performed in the terminal phase showed del(5)(q13q31),t(9;22)(q34;q11), and a complex rearrangement involving chromosomes #2 and #3. A correlation between chromosomal abnormalities and hematologic findings could be established. In this case, we have assumed that the Philadelphia translocation is a late event, due to prior mutagen exposure, and its association with a common secondary abnormality (5q-), followed by a progressively developing myeloproliferative phase. Furthermore, the association of Ph and 5q- in a single clone seems to indicate that the same stem cell is affected by these two abnormalities.

t(9;11)(p22;q23) translocation in blastic phase of chronic myeloid leukemia.

A patient with chronic myeloid leukemia showed clonal karyotypic evolution, with the appearance of an i(17q) and t(9;11)(p22;q23). This case sheds light upon leukemogenic events related to t(9;11)(p22;q23). The presence of t(9;22) and t(9;11) in the same clone showed that t(9;11) may affect a pluripotent stem cell, thus accounting for t(9;11) in both lymphoid and monocytic leukemias. In this patient, t(9;11) could not be related to a prior cytotoxic exposure and was instead the result of natural evolution of chronic myeloid leukemia. Furthermore, this led us to assume that the phenotype of blast cells may be determined by a chromosome abnormality. A phenotypic conversion from myeloblastic to undifferentiated morphologic aspect was observed when t(9;11) was detected, suggesting that t(9;11) may have induced a loss in differentiation of blast cells affected by this change. This assumption is in agreement with the putative presence of genes activated in pluripotent progenitors by 11q23 rearrangements.

Prognostic significance of karyotype in a twelve-year follow-up in childhood acute lymphoblastic leukemia.

We report a follow-up of 49 children with acute lymphoblastic leukemia (ALL) diagnosed between 1972 and 1978 (follow-up 12-18 years). This series allowed us to analyze the predictive value of karyotype in a long-term follow-up. Karyotypes were abnormal in 33 cases (67.3%): pseudodiploidy in 11 (22.4%), hyperdiploidy > 50 chromosomes in 8 (16.3%), hyperdiploidy 47-50 chromosomes in 11 (22.4%), and hypodiploidy in 3 cases (6.1%). Event-free survival (EFS) and survival studies showed that the outcome of patients was determined only by treatment and karyotype. Eleven patients have survived, nine in first remission (6 years 5 months to 15 years 2 months), and two are in second remission (3 years 8 months and 8 years 2 months). All ploidy groups are represented in these patients. Late relapses can occur in the hyperdiploid > 50 group, thus accounting for shorter EFS than expected, but because of the unusually long second remission of one patient, the rate of surviving patients was higher for this ploidy group than for all other ploidy groups together. Conversely, patients with only numerical abnormalities (no matter which ploidy group they belonged to), had a better outcome than did patients with structural changes or normal karyotypes and no discrepancy between EFS and survival curves was observed in this chromosomal group. Thus, our results suggest that numerical changes only should be considered an indicator of low risk factor, but our results, based on partially banded karyotypes, need to be verified by a current method and therapy.

Evaluation of two markers of cell maturation and proliferation in cultured amniotic cells of trisomic 18 fetuses at the 15th week of gestation.

Intensive studies have been conducted so far on biochemical markers available for screening of chromosome defects in obstetrical monitoring. In this paper we report further data on two protein phosphatases: alkaline phosphatase (a marker of cell maturation) and phosphotyrosine phosphatase (a marker of cell proliferation) assayed in cultured amniotic cells from fetuses with trisomy 18 at 15 weeks of gestation. Comparison with normal fetal cells showed a different behaviour for each enzyme: alkaline phosphatase was very significantly lowered while phosphotyrosine phosphatase remained a normal levels. These results provide a further enlargement of the field of biochemical markers used in the screening tests of trisomy 18.

Lower alkaline phosphatase activity and occurrence of an abnormal hybrid intestinal/tissue non-specific isoform in Down's syndrome amniotic fluids.

Quantitative and qualitative analysis of alkaline phosphatases (AP) was performed on amniotic fluid in 59 normal pregnancies and 14 Down's syndrome (DS) pregnancies at 16, 18 and 19 weeks of gestation. In DS cases, intestinal and placental isoenzyme levels were significantly reduced (P<0.001) and the AP electrophoretic pattern was seen to be modified on polyacrylamide gel electrophoresis. A unique component was detected. After extraction and purification of the abnormal isoenzyme, peptide fragments obtained after cyanogen bromide cleavage indicated a hybrid heterodimeric AP composed of intestinal and tissue non-specific subunits, as evaluated by SDS polyacrylamide gel electrophoresis.

22q11 deletion in DGS/VCFS monozygotic twins with discordant phenotypes.

22q11.2 deletion is a common genetic disorder characterised by a wide spectrum of clinical manifestations. To date no simple genotype-phenotype correlation has been established. Moreover, several reports have mentioned phenotypic discordance between monozygotic twins. No definite mechanism has been demonstrated and mosaicism, a postzygotic second hit, environmental effects and chance events have been proposed. The twinning process itself has been suspected in two cases (11, 23). We report the case of monozygous twins with a 22q11.2 deletion who are discordant for a heart defect. We found no arguments for mosaicism or twin-to-twin transfusion syndrome. The frequent discordance for heart defects in DiGeorge/Velo-cardio-facial syndromes (DGS/VCFS) does not favour the hypothesis of somatic mutations contributing to the phenotypic variation, but rather a complex interaction between genetic and environmental systems.

[Role and contribution of karyotyping in male infertility]. / Place et apports du caryotype en infertilité masculine.

In the context of the aetiological investigation of male infertility, the authors stress the place and the contribution of blood karyotype testing in the light of their personal experience based on 1,612 subjects. This examination has an important place, as about 15% of azoospermic subjects and 6 to 7% of subjects with oligospermia less than 10 million spermatozoa per ml, either alone or in combination with other abnormalities of the semen examination, present a congenital chromosomal abnormality. A remarkable constancy of the results was observed according to identical recruitment criteria. The contribution of this examination is also important: the medical and psychological value of detecting the cause of azoospermia, genetic counselling and antenatal chromosomal diagnosis for non-azoospermic subjects with an equilibrated structural abnormality, in whom treatment allows a chance of procreation, genetic counselling for the family of these subjects in order to prevent the appearance of a chromosomally abnormal infant. In conclusion, the authors argue in favour of the routine use of this test in all infertile subjects with at least isolated oligospermia less than 10 million spermatozoa per ml.