Abstract
ObjectiveAlthough chromosomal heteromorphisms are commonly found in the general population, some researchers have suggested a correlation with higher rates of embryo aneuploidy. This study aimed to assess the rates of embryo aneuploidy in couples who carry a chromosome heteromorphism.MethodsThe study included couples who had G-banding karyotype testing and underwent an IVF/PGT-A cycle between January 2012 and March 2018. The participants were classified by couple karyotype: Group A: ≥1 patient reported to be a heterochromatic variant carrier; Group B: both partners reported to be “normal”. We assessed the rates of aneuploidy among the groups. We ran a multivariate regression analysis to assess the relationship between heterochromatic variants and the rates of embryo aneuploidy.ResultsOf the 946 couples analyzed, 48 (5.0%) reported being a carrier of ≥1 heterochromatic variant. We had 869 IVF/PGT-A cycles included in the analysis (Group A: n=48; Group B: n=82). There were no significant differences in embryo ploidy rates among the groups. The heterochromatic chromosome variant was not associated with increased likelihoods of aneuploidy (OR=1.04, CI:95% 0.85- 1.07; p=0.46). Finally, the gender of the heterochromatic variant carrier had no association with increased likelihood of aneuploidy (OR 1.02, CI 95% 0.81-1.28, p=0.82).ConclusionsOur study showed no association between parental heterochromatic chromosome variants and subsequent embryo aneuploidy rates. Ploidy rates do not appear to be negatively associated with couples when at least one patient is reported to be a carrier of a heterochromatic variant on the karyotype.
Highlights
Heterochromatic Chromosomal Variants or Chromosomal heteromorphisms (CH) are quantitative or positional alterations in constitutive DNA heterochromatin, occurring in the centromeric region of chromosomes 1, 9, 16, Y, and short arms of acrocentric chromosomes
A total of 869 IVF/Preimplantation genetic testing (PGT)-A cycles were included in the analysis (Group A “carriers”: n=48; Group B “normal karyotypes”: n=821)
Demographic, stimulation parameters and embryological variables were comparable among cohorts (Table 1)
Summary
Heterochromatic Chromosomal Variants or Chromosomal heteromorphisms (CH) are quantitative or positional alterations in constitutive DNA heterochromatin, occurring in the centromeric region of chromosomes 1, 9, 16, Y, and short arms of acrocentric chromosomes. CH were considered to be normal familiar variants due to their frequency in the general population, after karyotyping staining techniques (Dong et al, 2013; Bhasin, 2005; Wyandt & Tonk, 2012) Today, these heterochromatic regions are known to sustain non-coding repetitive sequences of satellite DNA, which regulates and modulates gene expression under different cellular function conditions. These heterochromatic regions are known to sustain non-coding repetitive sequences of satellite DNA, which regulates and modulates gene expression under different cellular function conditions These regions contribute to proper chromosome segregation by binding sister centromeres and assembling the kinetochore during meiosis (Skaletsky et al, 2003). Centromere and kinetochore dynamics are essential for correcting or avoiding abnormal chromosome segregation during gamete and/or embryo development processes (Yakin et al, 2005)
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