[Familial thymoma and translocation t (14;20) (q24;p13)]. / Thymome familial et translocation t (14;20) (q24;p13).

A familial lympho-epithelial thymoma with constitutional chromosomal translocation t (14;20) (q24;p13) is presented: the thymoma and its particular translocation are present in the mother and the two sons of her offspring. The small number of cases do not allow establishing any relation between thymoma and this particular translocation. Concerning genetic counseling, an annual thoracic radiography is necessary for all the other family members, carriers or not of the translocation.

Cytogenetic and molecular investigations of an abnormal Y chromosome: evidence for a pseudo-dicentric (Yq) isochromosome.

A derivative Y chromosome was found in a 55-year-old man with Lambert-Eaton paraneoplasic pseudomyastheniform disease. Small testicles, azoospermia were noticed and hormonal level values were as in the Klinefelter syndrome. A 45,X/46,XYp+ mosaïcism was described on peripheral blood lymphocytes. Cytogenetic investigations with R-G-C- and Q-banding have been performed. In situ hybridization with the GMGY 10 DNA probe showed two copies of proximal Yp sequences. Southern blot analyses were performed using the Y DNA probes 27a, 47z, 64a7, 50f2 disclosing specific Yp and Yq sequences from the pseudoautosomal boundary to the Yq proximal portion. The der(Y) has been defined as a dicentric isochromosome for the long arm with one active and one apparently suppressed centromere. The breakpoint leading to the der(Y), has been located in the pairing segment of the Y short arm (i.e. Yp11.32). So the der(Y) was interpreted as a psu dic(Y) (qter-->cen-->p11.32 ::p11.32-->qter). There was thus an almost complete duplication of the Y chromosome.

BrdU related direct revelation of typical dynamic R- and G-banding with the use of monoclonal anti-BrdU antibody.

Pulse 5-bromodeoxyuridine (5-BrdU) incorporation during the last S-phase is known to produce R- or G-banded chromosomes after photolysis-plus-Giemsa (FPG) staining. The authors applied an immunological staining with monoclonal anti-BrdU antibody instead of the FPG protocol. The results offered banded chromosomes with an immunological typical R-banding (RBI) on the GBG cultivated cells (early pulse incorporation), and an immunological G-banding (GBI) on the RBG cultivated ones (late pulse incorporation). After a further FPG protocol following an immunological treatment, an inverted banding pattern became evident whereas a faint immunological staining remained. Thus the method superimposed a GBG-banding on the RBI-staining or a RBG on the GBI one. This allows a rapid and easy R and G double chromosomal identification on the same metaphase cell, using first the immunological banding then the classical FPG staining. The method allows a reproducible dynamic G-banding with an easy monitored late 5-BrdU pulse incorporation specially attractive in spontaneous dividing cells from bone marrow. This dynamic G-banding protocol should be extended to chorionic villi and malignant cells. Our data are in agreement with a connection between dynamic banding and chromosomal portions containing or not BrdU. The lack of an immunological staining after the FPG protocol has been noticed and assume the photolysis degradation-elution of the DNA in BrdU-substituted areas.

Trisomy 16q23----qter arising from a maternal t(13;16)(p12;q23): case report and evidence of the reciprocal balanced maternal rearrangement by the Ag-NOR technique.

We describe a female new-born with partial trisomy of the long arm of chromosome 16. The chromosome anomaly was the result of an unbalanced segregation of a maternal translocation t(13;16)(p12;q23). Dynamic (RBG, GBG) banding and the Ag-NOR technique ascertained the reciprocal balanced maternal translocation between the 16q23----qter and 13q12----pter segments because nucleolar organizers were present on the tip of long arms of the derivative 16 maternal chromosome. As monosomy 13p has little or no deleterious effect we consider our case as exhibiting the phenotype of trisomy 16q23----qter free from any monosomic feature. Clinical effects are of less consequence as compared with previously published cases of partial trisomy 16q.

Prenatal diagnosis of PIBIDS.

In a well-documented PIBIDS family, two investigations of DNA excision repair showed a severe defect in lymphocytes from the index case (residual repair activities were 10.6-12.1 per cent). The values for the mother, father, and sister were within the normal range when compared with a healthy control. In the pregnant mother, a prenatal diagnosis of PIBIDS was made by measuring UV-induced unscheduled DNA synthesis in cultivated amniotic fluid cells. Results ranged between 12.5 and 26.1 per cent depending on the UV doses applied and were consistent with an affected fetus. The parents opted for a termination of pregnancy. Following a therapeutic abortion, fetal skin fibroblasts were tested and showed a severe DNA excision-repair defect of 9.2-13.5 per cent of residual activity.

Routine autoradiographic analysis of DNA excision-repair. Report of prenatal and postnatal diagnosis in eleven families.

DNA excision-repair of UV induced damages was investigated by unscheduled DNA synthesis and quantitative autoradiography. The method has been routinely used on lymphocytes for postnatal diagnosis of xeroderma pigmentosum and PIBIDS syndrome. Ten XP-families including 13 clinical XP patients and 9 XP-risk children, and one family with one clinical PIBIDS case and one PIBIDS-risk child were screened. Each of the 14 affected patients were biologically ascertained with a significant excision-repair defect. Among the 9 XP-risk children without clinical manifestations, the DNA excision-repair was defected in 4 cases considered as biological XP, and normal in 5 cases considered as biologically normal subjects. Likewise the PIBIDS-risk child exhibited a normal excision-repair. According to the age of the XP or PIBIDS-risk children, and the delay of appearance of clinical manifestations, the method should not present neither false positive nor false negative results and allows the infraclinical diagnosis. The protocol was extended for prenatal diagnosis on amniocytes and fetal cord blood. Excision-repair analysis on normal cultivated chorionic villi cells has been performed allowing a further first trimester prenatal diagnosis.

[Ichthyosis linked to the X chromosome. Biochemical and endocrinologic study]. / Ichtyose liée au chromosome X. Etude biochemique et endocrinienne.

The case of a 6-year-old male patient suffering from X-chromosome-linked ichthyosis is presented. There was no steroid sulfatase activity in the proband's leucocytes and cutaneous fibroblasts. The activity was decreased in the proband's mother's leucocytes and in one brother, affected by a mild ichthyosis. Basal plasma levels of dehydroepiandrosterone and its sulfate were normal for the patient's age, suggesting that sulfates do not play a significant role in the production of free steroids. After 3 intramuscular injections of 1,500 units of human chorionic gonadotropin, plasma levels of testosterone increased normally, indicating that there was no associated primary gonadal insufficiency.

RFLPs tightly linked with cystic fibrosis: value of probes at the D7S23 locus in prenatal diagnosis.

In a 1:4 risk family, the usefulness of probes at the D7S23 locus for prenatal diagnosis of cystic fibrosis is discussed by comparison with probes at the MET, D7S8, and D7S18 loci that did not allow accuracy in this family.

Interstitial deletion of chromosome 15: two cases.

Two cases of interstitial deletion of chromosome 15 with similar clinical features are presented. In one case, assay of hexosaminidase A enabled us to confirm that the structural gene is located between 15q22 and 15q25 and that it is included in the deletion.

[Ring chromosome 9. Case report and review of the literature]. / Le chromosome 9 en anneau. A propos d'un cas et revue de la littérature.

We report on a girl with ring chromosome 9, and review the 9 other cases of the literature. The main signs of this de novo chromosomal anomaly are: severe microcephaly, growth and psychomotor retardations, and heart malformations. Infectious complications occurs often. We found a decreased level of leucocyte interferon.

Usefulness of linked DNA probes for prenatal diagnosis of cystic fibrosis: report of a case in a 1:4 risk pregnancy.

Prenatal diagnosis of cystic fibrosis was performed with linked DNA probes in a couple with a 1:4 risk. The limits and the future of molecular prenatal diagnosis are discussed.

[Determination of haplotypes of DNA markers linked to the mucoviscidosis locus: detection of heterozygotes]. / Etablissement des haplotypes des marqueurs d'ADN proches du locus de la mucoviscidose: détection des hétérozygotes.

Linked DNA probes have been used in three families presenting an affected child with cystic fibrosis. The strategy used for the determination of haplotypes associated with parental normal and mutated genes is presented as well as its application to the detection of cystic fibrosis carriers among healthy children.

[Role of RNA in the inactivation of chromosomes during the metaphase]. / Rôle de l'ARN dans l'inactivation du chromosome lors de la métaphase.

Unfixed, isolated metaphase chromosomes were used as template in an in vitro RNA synthesis assay. In these conditions, no RNA synthesis was observed by autoradiography. Transcription was effective after treatment with methanol-acetic acid, HCl 0,2 N, NaCl 0,35 M or pancreatic RNase. Transcription is the most important after treatment with RNase. This result points out the problem of the role of RNA in inhibition of chromosome during mitosis.