Recombinant Chromosomes Resulting From Parental Pericentric Inversions—Two New Cases and a Review of the Literature

Abstract

A balanced pericentric inversion is normally without any clinical consequences for its carrier. However, there is a well-known risk of such inversions to lead to unbalanced offspring. Inversion-loop formation is the mechanism which may lead to duplication or deletion of the entire or parts of the inverted segment in the offspring. However, also partial deletion and duplication may be an effect of a parental inversion, depending on the size of the inversion and the uneven number of crossing over events, also suggested to be due to an inversion loop. Here we describe two new cases of recombinant chromosomes and provide a review of the literature of comparable cases. Interestingly, this survey confirmed the general genetic principle that gain of copy numbers are better tolerated than losses. Furthermore, there is a non-random distribution of all human chromosomes concerning their involvement in recombinant formation, which is also discussed.

Cytogenetic Investigation of Infertile Patients in Hungary: A 10-Year Retrospective Study

“…Based on the study of Manvelyan et al, ~88% of chromosomal break-events arose in GTG-light bands, 21% co-localized with intrachromosomal telomeric-like sequences (ITS), 35.8% were at or near the Mariner transposon-like elements (MTLE), and at least 45% could have had a correlation with fragile sites (FS) [ 41 ]. The importance of fragile sites in balanced reciprocal translocation was supported by Liehr et al reporting cytogenetic co-localization of fragile sites in ~71% of the studied 529 break-events in 251 cases with balanced chromosomal rearrangements [ 36 ].…”

“…The mechanism of chromosomal abnormality affecting gametogenesis and the resulting reproductive failure can be the following: (i) numerical chromosomal abnormalities in the gametes by interchromosomal effect (ICE), (ii) the inverted chromosome region can cause synaptic and recombinational problems during meiosis depending of the length of the inversion: the larger the inversion, the more frequently recombinants are observable in the gametes. (iii) DNA fragmentation in spermatozoa and activation of apoptosis, and (iv) alteration of gene function at the breakpoints [ 34 , 35 , 36 ]. However, Young et al could not confirm the presence of increased aneuploid sperm for chromosomes that were not involved in the inversion carriers [ 37 ].…”

Inversion breakpoints and the evolution of supergenes

“…Chromosomal inversions can indeed strongly reduce recombination between the genomic segments they cover, a property leading to their discovery by Sturtevant (1921). Specifically, single crossing‐over events within the rearranged region in heterokaryotypic individuals produce nonviable or unfit gametes with unbalanced gene content (Hoffmann & Rieseberg, 2008; Kirkpatrick, 2010; Liehr et al, 2019). Recombination between chromosomal rearrangements is still possible when double crossing‐over events occur, making recombination more likely to happen at the centre of inversions than near breakpoints (Hoffmann & Rieseberg, 2008; Stump et al, 2007).…”

Pre‐ and postnatal findings in a patient with a recombinant chromosome rec(8)(qter→q21.11::p23.3→qter) due to a paternal pericentric inversion inv(8)(p23.3q21.11) and review of the literature

“…In comparison to these two cases as well as to the estimated sizes of the terminal 8p deletion (11.65 Mb) and the terminal 8q duplication (47.90 Mb) in "classic" Rec8 syndrome (San Luis Valley syndrome), our patient showed the smallest terminal 8p deletion (1.4 Mb) and the largest 8q duplication (69.8 Mb) reported so far (Vera-Carbonell et al, 2013). This corresponds to 69% of the regions of 8q, and this is just below the maximal percentage of 80% reported to be compatible with live for 8q duplications (Liehr et al, 2019). In contrast, the largest terminal 8p deletion (16.9 Mb) and the smallest 8q duplication (21.7 Mb) was reported by Stevens et al (2010).…”