RESUMO
Deletion of the long arm of chromosome 18 is one of the most common segmental aneusomies compatible with life and usually involves a deletion of the terminal chromosomal region. However, the mechanisms implicated in the stabilization of terminal deletions are not well understood. In this study, we analyzed a girl with moderate mental retardation who had a cytogenetically visible terminal 18q deletion. In order to characterize the breakpoint in the terminal 18q region, we used fluorescence In situ hybridization (FISH) with bacterial artificial chromosomes (BACs) and pan-telomeric probes and also the array technique based on comparative genomic hybridization (array-CGH). FISH with pan-telomeric probes revealed no signal in the terminal region of the deleted chromosome, indicating the absence of normal telomere repeat (TTAGGG)n sequences in 18q. We suggest that neo-telomere formation by chromosome healing was involved in the repair and stabilization of this terminal deletion.
Assuntos
Deleção Cromossômica , Cromossomos Humanos Par 18 , Hibridização Genômica Comparativa/métodos , Hibridização in Situ Fluorescente/métodos , Telômero/genética , Adolescente , Feminino , Humanos , Deficiência Intelectual/genética , Cariotipagem , Sequências Repetitivas de Ácido Nucleico/genética , Telômero/metabolismoRESUMO
The 16q21 --> qter duplication is a chromosomal abnormality rarely found in liveborn infants, with only four published cases. We report here on the 7-year follow-up of a female patient with trisomy 16q21 --> qter due to a maternal balanced translocation t(4;16)(q35.2;q21). The patient shows severe mental retardation, congenital heart malformations, nephropathy, and other congenital anomalies. The derivative chromosome was characterized by GTG banding, fluorescent in situ hybridization (FISH) with different BAC probes and the array technique, in order to map the breakpoints. The patient has a 16q21 --> qter duplication, with a 4q35 --> qter monosomy, which we assume does not contribute to the abnormal phenotype. This is the first reported case of postnatal survival to the age of 7 years, an unusually long time in this chromosomal syndrome.
Assuntos
Anormalidades Múltiplas/genética , Aberrações Cromossômicas , Cromossomos Humanos Par 16/genética , Cromossomos Humanos Par 4/genética , Cardiopatias Congênitas/genética , Deficiência Intelectual/genética , Trissomia/genética , Anormalidades Múltiplas/mortalidade , Adulto , Feminino , Seguimentos , Cardiopatias Congênitas/mortalidade , Humanos , Hibridização in Situ Fluorescente , Recém-Nascido , Deficiência Intelectual/mortalidade , Cariotipagem , Masculino , Monossomia , Taxa de Sobrevida , Translocação GenéticaRESUMO
Supernumerary marker chromosomes (sSMC) may or may not be associated with an abnormal phenotype, depending on the presence of euchromatin, on their chromosomal origin and whether they are inherited. Over 80% of sSMCs are derived from acrocentric chromosomes and half of them include the short arm of chromosome 15. Generally, they appear as bisatellited isodicentric marker chromosomes, most of them are symmetric. These chromosomes are normally originated de novo and are associated with mild to severe intellectual disability but not with physical abnormalities. We report on a patient with an SMC studied using classical and molecular cytogenetic procedures (G and C banding, NOR staining, painting and centromeric fluorescent in situ hybridization (FISH), BAC-FISH, and SKY). The MLPA technique and DNA polymorphic markers were used in order to identify its parental origin. The marker chromosome, monosatellited and monocentric, was found to be derived from a maternal chromosome 15 and was defined as 15pter-q21.2. This is the report of the largest de novo monosatellited 15q marker chromosome ever published presenting detailed cytogenetic and clinical data. It was associated with a phenotype including cardiac defect, absence of septum pellucidum, and dysplasia of the corpus callosum.
Assuntos
Anormalidades Múltiplas/genética , Cromossomos Humanos Par 15/genética , Marcadores Genéticos , Trissomia , Síndrome Acrocalosal/genética , Deficiências do Desenvolvimento/genética , Feminino , Cardiopatias Congênitas/genética , Humanos , Lactente , Fenótipo , Septo Pelúcido/anormalidades , Cariotipagem EspectralRESUMO
A family with six alive patients with partial monosomy 5p and five with partial trisomy 5p due to a t(5;15)(p13.3;p12) translocation is reported. The translocation was present in four generations with eight balanced carriers. This is the first molecular-cytogenetic and clinical study with both syndromes present in the same family. Using fluorescence in situ hybridization (FISH) with bacterial artificial chromosome (BAC) probes, the breakpoint was mapped to 5p13.3, in the interval corresponding to the BAC clone RP11-1079N14, thereof resulting a 5pter-5p13.3 deletion or duplication of approximately 32 Mb. These chromosome imbalances can be considered pure, since the other imbalance produced involving chromosome 15p has no phenotypic effect. The presence of several individuals with 5p monosomy and 5p trisomy in the same family is valuable for a better delineation of both syndromes.
