Extensive cytogenetic analysis of a stable dicentric isochromosome 21, idic(21), formed by fusion of the terminal long arms

Abstract

The dicentric isochromosome 21 described in this paper was formed by fusion of the terminal parts of the long arms of two chromosomes 21. No interstitial telomeric AGGGTT repeats could be detected at the fusion point, but G-banding, comparative genomic hybridization, and fluorescence in situ hybridization with painting probes for 21qter revealed no loss of other terminal DNA sequences at the fusion point. Thus, only the telomeric repeats seem to have been lost prior to, or as a consequence of, isochromosome formation. Both short arms of the isochromosome were intact with complete NORs, and staining for α-satellite DNA showed that the DNA content of the two centromeres was the same. Antibody staining for the centromeric proteins CENP-C and CENP-E and for topoisomerase IIα and IIβ demonstrated that these proteins were localized predominantly or exclusively at the centromere in the primary constriction. A novel functional in situ assay for topoisomerase activity in vivo similarly demonstrated enzyme activity exclusively at the primary constriction centromere.

Structural changes of the brain in rheumatoid arthritis

“…In 1965, Lejeune et al 1965 suggested a tandem inverse duplication in these patients. Subsequently, a few cases have been published [Turleau et al, 1980; Pfeiffer and Loidl, 1982; Stoll et al, 1982; Pangalos et al, 1992b; Gutierrez‐Angulo et al, 1999; Barbi et al, 2000; Cortes‐Gutierrez et al, 2002; Wandall et al, 2002; Sheth et al, 2007; Egashira et al, 2008]. In this study, we report on a DS child with karyotype 46,XX,idic(21)(q22.3).…”

FISH characterization of a dicentric Yq (p11.32) isochromosome in an azoospermic male

“…This suggests that one of the centromeres may have been inactivated [Hsu, 1994]. Similar results are found in dicentrics where acrocentric chromosomes are involved [Lemyre et al, 2001;Wandall et al, 2002]. These dicentric chromosomes would then behave as monocentrics increasing their stability.…”