Sequential FISH allows the determination of the segregation outcome and the presence of numerical anomalies in spermatozoa from a t(1;8;2)(q42;p21;p15) carrier

Abstract

Purpose To find out the meiotic segregation behaviour of the t(1;8;2)(q42;p21;p15), to evaluate the occurrence of interchromosomal effects, and to determine whether there is an accumulation of unbalanced products in aneuploid/diploid gametes. Methods A sequential FISH protocol based on two successive hybridization rounds over the same spermatozoa was performed to determine the segregation outcome of the rearranged chromosomes. The presence of numerical abnormalities for 13, 18, 21, X and Y was also evaluated by sperm FISH. Those aneuploid/diploid gametes were subsequently relocalized and analyzed for their segregation content through additional hybridization rounds. Results The segregation pattern observed reported a very low production of normal/balanced gametes (11.7 %). Significant increased frequencies of diploidies and disomies for chromosomes X/Y and 18 were detected (p <0.001). Aneuploid and diploid spermatozoa displayed significant increases of 5:1, 6:0 and other unexpected disjunction modes (p <0.001).Conclusions The strategy developed in this study is a reliable new approach to establish the full segregation pattern of complex chromosome rearrangements (CCR). Results corroborate the low number of normal/balanced spermatozoa produced by CCR carriers and support previous findings regarding an altered segregation pattern in gametes with numerical abnormalities. Altogether this confirms the importance of PGD as a tool to prevent the transmission of chromosomal abnormalities to the offspring in CCR patients.

Sperm FISH and chromatin integrity in spermatozoa from a t(6;10;11) carrier

“…4). This was similar to previously reported data (4:2 -38.2, 35.69, and 28.9%; adjacent 3:3 -34.14, 31.03, and 43.1% as reported by Loup et al (2010), Pellestor et al (2011b) and Godo et al (2013) respectively). This is also in accordance with data obtained from familial CCR cases that indicate that most of the observed live births have resulted from these two segregation modes (Batista et al 1994, Lespinasse et al 2003.…”

“…Our results indicated such a frequency at 2.31%, while three other cases of three-way CCR analyses found it to be 9.3% (Loup et al 2010), 3.15% (Pellestor et al 2011b) and 15.6% (Godo et al 2013). Unexpected FISH phenotypes can be the consequence of three factors: i) nondisjunction at the second meiotic division, ii) increasing difficulty in FISH result interpretation with increasing number of chromosomes involved, and iii) possible chiasma occurrence, leading to the formation of additional recombinant chromosomes (Anton et al 2007, Uroz & Templado 2012.…”

“…To date, only seven studies have examined meiotic segregants by FISH in the ejaculated spermatozoa of CCR carriers. Only three were classical three-way CCRs: t(1;19;13) (Loup et al 2010), t(5;13;14) (Pellestor et al 2011b) and t(1;8;2) (Godo et al 2013); two were exceptional CCRs: (1;2;10),inv(10) (Kirkpatrick & Ma 2012) and t(3;6),inv(8) (Ferfouri et al 2012); and two had double two-way translocations t(8;9),t(1;16) (Ferfouri et al 2013) and t(Y;15),rob(13;14) (Ferfouri et al 2014). In all the three-way studies, the percentage of unbalanced segregants ranged from 69.4 to 88.3%.…”

“…It should be noted that the ICE phenomenon remains ambiguous because of its presence in not all, but in w50% of simple and complex translocation carriers Pellestor et al 2011b, Ferfouri et al 2012, 2014, Kirkpatrick & Ma 2012, Godo et al 2013, Vozdova et al 2013. However, it cannot be excluded that CCR carriers are more prone to exhibit ICE because of the substantially high numbers of chromosomes involved in rearrangement, especially with regard to the ongoing debate on the influence of chromosomal rearrangements on the proper meiotic behaviour of other chromosomes.…”

“…In cases of CCRs, a multivalent meiotic configuration generates a minimum of 64 different types of meiotic segregants: three-way CCR, hexavalent structure and reduced recombination (Saadallah & Hulten 1985, Johannisson et al 1988, Loup et al 2010, Pellestor et al 2011b. To date, only seven reports examining meiotic segregation in ejaculated spermatozoa in CCR cases have been published (Loup et al 2010, Pellestor et al 2011b, Ferfouri et al 2012, 2014, Kirkpatrick & Ma 2012, Godo et al 2013, two of which have evaluated the genetic content of sperm complements in the human-hamster oocyte penetration assay (Burns et al 1986, Cifuentes et al 1998. The percentage of unbalanced chromosome complements has been found to range from 69.4 to 88.3%.…”