Catherine Turleau

Cytogenetic forms of retinoblastoma: Their incidence in a survey of 66 patients

Sixty-six retinoblastoma patients were investigated using high resolution banding techniques, sister chromatid exchange (SCE) studies, and esterase-D phenotype determination and dosage. Seven patients (in six families) were found to be carriers of a rearrangement of band 13q14 due to de novo deletions, apparently balanced de novo translocations, or parental insertions. The possible role of submicroscopic parental insertions is suggested to explain transmission of nonchromosomal forms through unaffected carriers.

6q1 monosomy: a distinctive syndrome

A female infant with a de novo del 6q14q16.2 and five other patients with del 6q1 reported in the literature allow the delineation of a characteristic syndrome, the main features of which are: severe mental retardation, a round face with full cheeks, upslanting palpebral fissures, a short neck, umbilical hernia, malpositioned feet with syndactyly II‐III, and typical dermatoglyphics with an excess of whorls and clinodactyly of the Vth finger.

Cytogenetic investigation in 413 couples with spontaneous abortions.

413 couples with one or more spontaneous miscarriages were karyotyped. Observed chromosomal rearrangements were classified as major rearrangements, i.e. Robertsonian and reciprocal translocations, pericentric and paracentric inversions, supernumerary small metacentrics, and minor rearrangements, i.e. pericentric inversions of chromosome 9, and constitutional fragility of particular chromosome sites. 2.30% of the individuals were carriers of a major rearrangement, which represents a ten-fold increase when compared to the general population. The contribution of each type of rearrangement is unequal, the most important being pericentric inversions (36 times more frequent than in the general population). Contrary to data from the literature, the probability of finding a rearrangement does not seem to increase with the number of miscarriages.

Maternal origin of a de novo balanced t(21q21q) identified by ets-2 polymorphism

SummaryMolecular investigations were done in a woman with a de novo balanced t(21q21q) discovered because of the birth of a trisomic 21 baby. Polymorphisms detected with probe ets-2 after MspI digestion showed that both chromosomes 21 involved in the rearrangement were of maternal origin. The most likely hypothesis is that of a disomic 21 oocyte fertilized by a nullisomic 21 sperm.

X-linked hypohidrotic ectodermal dysplasia and t(X;12) in a female.

A female patient with features of hypohidrotic ectodermal dysplasia (HED) was found to be a carrier of a de novo t(X;12) with a breakpoint in Xq13.1. This is the second instance of an X/autosome translocation, with apparently the same X breakpoint, reported in HED.

Retinoblastoma, deletion 13q14, and esterase D: Application of gene dosage effect to prenatal diagnosis

Esterase D (ESD) gene dosage studies were performed on amniotic cells from a fetus at risk for del 13q14. The mother was a balanced carrier of an insertion in chromosome #20: 46,XXins(20;13)(p12;q1307q14.3). She had already given birth to a monosomic child with retinoblastoma (Rb) and to a phenotypically normal child trisomic for the same 13q14 segment. Both sibs displayed the expected proportionate gene dosage effects for ESD. A 153% value of ESD activity was found in the amniotic cells indicating unambiguously that the fetus was not monosomic for segment 13q14 and therefore not at increased risk for Rb. The mother delivered a phenotypically normal child who was confirmed to be trisomic for segment 13q14 by cytogenetic analysis and by gene dosage studies for ESD in cord blood cells and in lymphoblastoid cells.

New observations on the human and chimpanzee karyotypes

SummaryFurther comparisons of the human and chimpanzee karyotypes, with more refined techniques, confirm previous results obtained by the authors. The points of breakage of pericentric inversions are defined. The type of fusion of both acrocentrics, equivalent to the human chromosome No. 2, is discussed.ZusammenfassungWeitere Vergleiche des menschlichen Karyotyps vom Schimpansen mit verfeinerter Technik bestätigen frühere Ergebnisse der Autoren. Die Bruchstellen der perizentrischen Inversionen werden definiert. Der Fusionstyp der beiden Akrozentrischen, die dem menschlichen Chromosom Nr. 2 entsprechen, wird diskutiert.

Comparative gene mapping and primate evolution

Chromosome homologies defined by banding techniques have allowed the elucidation of the primate chromosomal phylogeny (Turleau et al. 1972, Grouchy et al. 1978, Dutrillaux 1979, Yunis and Prakash 1982). The correspondance of these homologies and the homology of gene content was shown by the first comparative mappings between man and the great apes obtained by somatic cell genetics (Finaz et al. 1973–1975-1977, Pearson et al. 1977). When more distantly related species are studied, homologies are more difficult to define. Nevertheless, Dutrillaux’s group (Dutrillaux 1979, Dutrillaux et al. 1986 for review) has suggested most of the rearrangements having occurred during primate evolution. Only gene mapping in these species could confirm or infirm these homologies and demonstrate homologies not defined by chromosome banding, as for the gibbon.