Homologous sequences at human chromosome 9 bands p12 and q13-21.1 are involved in different patterns of pericentric rearrangements

Abstract

A thorough study of the heterochromatin organisation in the pericentromeric region and the proximal long (q) and short (p) arms of human chromsome 9 (HSA 9) revealed homology between 9p12 and 9q13-21.1, two regions that are usually not distinguishable by molecular cytogenetic techniques. Furthermore, the chromosomal regions 9p12 and 9q13-21.1 showed some level of homology with the short arms of the human acrocentric chromosomes. We studied five normal controls and 51 clinical cases: 48 with chromosome 9 heteromorphisms, one with an exceptionally large inversion and two with an additional derivative chromosome 9. Using fluorescence in situ hybridisation (FISH) with three differentially labelled chromosome 9-specific probes we were able to distinguish 12 heteromorphic patterns in addition to the most frequent pattern (defined as normal). In addition, we studied one inversion 9 case with the recently described multicolour banding (MCB) technique. Our results, and previously published findings, suggest several hotspots for recombination in the pericentromeric heterochromatin of HSA 9. They also demonstrate that constitutional inversions affecting the pericentromeric region of chromosome 9 carry breakpoints located preferentially in 9p12 or 9q13-21.1 and less frequently in 9q12.

Chromosome heteromorphisms: an impact on infertility

“…We believe analyses at the molecular level will reveal mechanisms in more detail as following molecular genetic studies done in chromosome variants, the heterochromatin has been regarded to have more crucial cellular roles than previously thought. Thus, chromosome variants should not be ignored by cytogeneticists and clinicians, for contributory reasons that may not have been realized yet [12,13,16].…”

Linear increase of structural and numerical chromosome 9 abnormalities in human sperm regarding age

“…4,20 These studies are coincident in that chromosome 9 has a higher number of breakpoints than expected by chance and also in that 50% of the breakpoints are located between the centromere and the 9qh þ segment. In somatic cells, Starke et al 22 proposed that the homology between 9p12 and 9q13 -q21.1 with the short arms of the acrocentric human chromosomes, made these chromosomes more prone to chromosome rearrangements and increased the risk of an interchromosomal effect among them. A significant excess of sperm bearing partial duplications of the 9q region compared with those bearing partial duplications of 9cen (P ¼ 0.017) was detected.…”

Chromosomal Heteromorphisms and Karyotype Abnormalities in Humans

“…We believe analyses at the molecular level will reveal mechanisms in more detail as following molecular genetic studies done in chromosome variants, the heterochromatin has been regarded to have more crucial cellular roles than previously thought. Thus, chromosome variants should not be ignored by cytogeneticists and clinicians, for contributory reasons that may not have been realized yet (Lissitsina et al, 2006;Madon et al, 2005;Starke et al, 2002).…”

“…The inv (9) is said to be common in the general population and it is inherited in a Mendalian fashion (Akbas et al, 2010;Rao et al, 2006). A small pericentric inversion of chromosome 9 is a most common inversion seen in human chromosomes with the incidence of 1-3% in the general population (Rao et al, 2006;Codina et al, 2006;Starke et al, 2002). Pericentric inversion 9, especially complete inv (9) (p11q13) has been reported in association with recurrent miscarriages, infertility and congenital anomalies (Sahin et al, 2008;Madon et al, 2005;Akbas et al, 2010;Jeong et al, 2010Mozdarani et al, 2007Negvenkar et al, 2005;Dubey et al, 2005;Kosyakova et al, 2013;Ganguly and Kadam, 2014).…”