X CHROMOSOME INSTABILITY IN A MOTHER OF A CHILD WITH MOSAIСISM FOR AUTOSOMAL STRUCTURAL ABNORMALITY
Chromosome instability occurs due to unequal distribution of DNA to daughter cells during mitosis, resulting in aneuploidy and other chromosome abnormalities. Mosaicism is the presence of two or more populations of cells (which have developed from a single zygote) with different genotypes. Recent reports on somatic mo¬saicism have demonstrated that mosaic structural chromosome abnormalities are as likely to underlie intellectual disability, congenital malformations and autism as low-level mosaic aneuploidy does. Here, we present a familial case of chromosome instability and mosaicism. Karyotyping of an 8 years old girl with microcephaly, mental retardation, autistic features, large upper incisors, small lower jaw, hypertrichosis and pectus excavatum revealed a mosaic deletion in chromosome 8. Array CGH allowed us to specify genomic localization, size and genes of the deleted region. Karyotyping of mother, a 38 year old woman planning another pregnancy showed the X chromosome instability affecting 20% of cells. FISH on 1000 interphase nuclei and 150 metaphase spreads revealed 10.9% and 8% of chromosome instability, respectively. These results enable us to make a suggestion about a link between the abnormalities. We propose parental chromosome instability to be a causal factor of structural rearrangements in children. The latter assumption is, however, a matter of further research. We also have to consider that mechanism underlying maternal chromosome instability is not known, and if revealed, could shed light on a correlation between two observed abnormalities.