A supernumerary "G" like chromosome originating from a maternal 13;15 translocation in a nondysmorphic, retarded girl

Psychiatric disorder in a familial 15;18 translocation and sublocalization of myelin basic protein of 18q22.3

Two related patients with similar clinical features consisting of a few dysmorphic signs and psychiatric disturbance were reported to have a partial trisomy of chromosomes 15(pter-q13.3) and 18(q23-qter) deriving from a familial translocation t(15;18). One patient is affected by bipolar disorder and the other by schizoaffective disorder. Both cases have a predominantly affective course; nevertheless, a clear diagnosis is difficult in the first patient, who is 15 years of age, and only a longitudinal course will allow us to establish a definite diagnosis. The possibility that these two pathologies belong to a single category is discussed, and the presence of a susceptibility locus on chromosome 18 is hypothesized. Cytogenetic data, FISH, and DNA studies indicate that the myelin basic protein (MPB) gene is not involved in the translocation, and localize it centromeric to the breakpoint on chromosome 18(q22.3). Thus, it is unlikely to be involved in the disease.

De novo partial trisomy 15q (proximal type)

This report describes a retarded girl with strabismus, high arched palate, antimongoloid slant, low set ears, hearing loss, micrognathia, short neck, and an anteriorly displaced anus. She was found to have a de novo partial trisomy of the proximal part of the long arm of chromosome 15.

Marker chromosomes: cytogenetic characterization and implications for prenatal diagnosis

Satellited marker chromosomes were identified in four individuals from unrelated families; one was first encountered in cultured amniotic fluid cells obtained for prenatal diagnostic studies. We present cytogenetic characterization of these marker chromosomes and clinical findings in the individuals carrying them. Identification of a marker chromosome in amniotic fluid cell cultures presents problems in genetic counseling, as it is often difficult to determine the clinical significance of such a finding. Chromosome-banding techniques now allow the precise identification of satellited marker chromosomes originating from chromosome 15. Presence of a supernumerary bisatellited der(15) marker chromosome containing the proximal long arm of 15 has been associated with mental and developmental retardation. Application of chromosome-banding techniques was useful in characterization of the marker chromosomes and providing prenatal genetic counseling.

Chromosome 15 anomalies and the Prader-Willi syndrome: cytogenetic analysis

The behaviour of chromosome 15 is very different from that of the other acrocentric chromosomes. The cytogenetic characteristics of rearrangements associated with Prader-Willi syndrome (PWS) are analyzed as similar rearrangements irrespective of the associated phenotype (reciprocal translocations of chromosome 15, small bisatellited additional chromosomes, Robertsonian translocations, interstitial deletions, pericentric inversions). This study suggests that: (1) The proximal ( 15q ) region and PWS seem to be indissociable ; (2) chromosome 15 has an indisputable cytogenetic originality which could be related to its histochemical properties. Chromosome 15 constitutive heterochromatin usually contains much 5-methylcytosine-rich DNA and a large amount of each of the four satellite DNAs. Furthermore the existence in the proximal ( 15q ) region of one or several palindromic sequences could be postulated to explain the great lability of this region of chromosome 15.

A boy with proximal trisomy 15 and a male foetus with distal trisomy 15 due to a familial 13p;15q translocation

A familial 13p;15q translocation was ascertained through a mentally retarded boy with a proximal trisomy 15 syndrome. His mother, who was a balanced 13p;15q carrier, had in addition a legal abortion after 22 weeks of gestation because of a prenatal diagnosis of distal trisomy 15 in a male foetus. Her mother and two sisters, who were balanced carriers, all had children with either a normal karyotype or a balanced translocation or had had pregnancies resulting in an early spontaneous abortion.

Advantages of silver staining in seven rearrangements of acrocentric chromosomes, excluding Robertsonian translocations

The silver-staining technique was used to study even cases of structural anomalies involving acrocentric chromosomes, excluding Robertsonian translocations. This technique allows identification of breakpoints and furnishes some information about interphase cell dynamics not seen on conventional chromosome preparations.