Translocaciones crípticas de cromosomas acrocéntricos en muestras de tejido de aborto aneuploide

Abstract

Chromosomal heteromorphisms are normal variants, considered without phenotypic impact, some of the most frequent are in the short arms of the acrocentric chromosomes (13, 14, 15, 21, 22). Recently it has been suggested that a type of chromosomal rearrangements considered heteromorphisms, known as cryptic translocation of acrocentric chromosomes (TCA), may be an etiological factor of numerical chromosomal abnormalities or aneuploidies, which are aborted by 90%. Objective: To determine the frequency of TCAs in a group of 62 spontaneous abortions presenting an aneuploidy of acrocentric chromosomes. Material and methods: 50 healthy individuals and 62 abortions with aneuploidy of any of the acrocentric chromosomes were included: nine trisomy 13, seven trisomy 14, eleven trisomy 15, nineteen trisomy 21 and sixteen trisomy 22. G-banded karyotype was performed to detect the aneuploidy and we used fluorescence in situ hybridization with probe D13Z1 / D21Z1, D14Z1 / D22Z1 and D15Z1 in order to study TCA, 15-20 metaphases were examined under an epifluorescence microscope. Results: 14% TCAs were observed in healthy individuals and 17.7% in abortions, without significant difference. In all cases the region D15Z1 was involved in the rearrangement, mainly translocated from short arms of chromosome 15 to the short arm of chromosome 13 or 14. Conclusions. The TCAs involving the region D15Z1 are a normal variant, with a high frequency in the sample of the Mexican population studied; this variant appears not to be involved in the etiology of acrocentric aneuploidy. Our findings suggest that this heteromorphism is a translocation or non-homologous recombination between acrocentric chromosomes involving D15Z1 region, and its frequency varies among ethnic groups.