Faculty of Medicine and Health Sciences, University of Brest, EFS, UMR1078, GGB, Brest, France.
Department of Medical Genetics and Reproductive Biology, Brest University Regional Hospital, Brest, France.
Cytogenet Genome Res. 2022;162(1-2):34-39. doi: 10.1159/000523916. Epub 2022 Apr 7.
Small supernumerary marker chromosomes (sSMCs) are defined as structurally abnormal chromosomes that are difficult to identify by conventional cytogenetic techniques. sSMCs are 3.75 times more common in infertile men than in the general population. This study aimed at characterizing a supernumerary marker chromosome in a nonconsanguineous infertile couple and analyzing its meiotic segregation in sperm by multicolor FISH. The male partner's karyotype was mos 47,XY,+idic(15)(pter→q11.1::q11.1→pter)[6]/46,XY[24].ish idic(15)(NOR+,D15Z3+,SNRPN-,D15Z3+,NOR+). In triple FISH using CEP 15, BAC 15, and BAC 21 probes, 4,227 spermatozoa of the patient were analyzed, and the sSMC was detected in only 0.66% of spermatozoa. In triple FISH employing CEP X, CEP Y, and BAC 18 probes, 2,008 spermatozoa of the patient were analyzed. The frequency of disomic and diploid sperm was not significantly different from control donors. To our knowledge, segregation of an sSMC 15 has been reported in only 9 males with non-mosaic karyotypes. These studies described rates of spermatozoa with sSMC 15 ranging from 6.23% to more than 50%. In this work, we report the first meiotic segregation analysis of a chromosome 15-derived sSMC in spermatozoa of a patient with a mosaic karyotype. The low rate of spermatozoa with sSMC detected is concordant with the low proportion of abnormal cells in our patient's lymphocytes. Moreover, the risk of interference of this sSMC with other chromosomes seems minimal. Genetic counseling was recommended given that the risk of chromosomal imbalance in the fetus linked to paternal sSMC was very low. Finally, a healthy boy was born after a natural pregnancy.
小的额外标记染色体（sSMCs）被定义为结构异常的染色体，这些染色体很难通过常规细胞遗传学技术来识别。在不育男性中，sSMCs 比一般人群常见 3.75 倍。本研究旨在对一对非近亲不育夫妇中的额外标记染色体进行特征描述，并通过多色荧光原位杂交（FISH）分析其在精子中的减数分裂分离。男方的核型为 mos 47,XY,+idic(15)(pter→q11.1::q11.1→pter)[6]/46,XY[24]。ish idic(15)(NOR+,D15Z3+,SNRPN-,D15Z3+,NOR+)。在使用 CEP 15、BAC 15 和 BAC 21 探针的三重 FISH 中，分析了患者的 4227 个精子，仅在 0.66%的精子中检测到 sSMC。在使用 CEP X、CEP Y 和 BAC 18 探针的三重 FISH 中，分析了患者的 2008 个精子。与对照组供体相比，二倍体和双倍体精子的频率没有显著差异。据我们所知，仅有 9 名非嵌合体核型的男性报告了 sSMC 15 的分离。这些研究描述了精子中 sSMC 15 的频率范围从 6.23%到 50%以上。在这项工作中，我们报告了首例染色体 15 衍生 sSMC 在患者嵌合体核型精子减数分裂分离的分析。检测到的 sSMC 精子的低发生率与我们患者淋巴细胞中异常细胞的低比例一致。此外，这种 sSMC 与其他染色体相互干扰的风险似乎很小。鉴于与父系 sSMC 相关的胎儿染色体不平衡风险非常低，因此建议进行遗传咨询。最后，在一次自然妊娠后，一名健康男孩出生。
