Multinucleate Blastomere (MNB, MNE)

Definition - What does Multinucleate Blastomere (MNB, MNE) mean?

Multinucleate Blastomere (MNB) is an abnormality of the cleavage-stage embryo in which embryonic cells have three or more nuclei. The formation of multinucleate blastomere is known as multinucleation. Nuclear defects due to multinucleation have been related to low implantation and pregnancy rates, chromosomal abnormalities, and arrested embryo development. Multinucleate blastomere are also called multinucleated embryos

Although multinucleated embryos (MNE) do have the potential to implant, most specialists performing assisted reproduction fertilization methods would not choose to transfer these embryos due to their low implantation and subsequent pregnancy rates as compared to non-multinucleated embryos. In some cases, where no other embryos are available, the fate of good quality MNE having no chromosomal anomalies may be decided otherwise.

FertilitySmarts explains Multinucleate Blastomere (MNB, MNE)

Embryonic cells called the blastomeres, continue to divide through mitosis after fertilization. Mitosis results in the division of a cell into two daughter cells, each having one nucleus. The resulting daughter cells have the same type and number of chromosomes as the parent cell. An error in this process could result in blastomeres having more than one nucleus. Blastomeres with two nuclei are called binucleate blastomeres, whereas those with three or more nuclei are called as multinucleate blastomeres.

Multinucleation could result even if the fertilization process is apparently normal. The specific cause of multinucleate blastomeres remains unclear, but the following factors are thought to contribute to this phenomena:
• Imperfect mitosis
• Damaged DNA
• Dysfunction of the mitotic spindle
• Alterations of nuclear membrane

A nuclear membrane surrounds the nucleus of the cell and protects the DNA from the cytoplasm, which is present outside the nucleus. A modification in this nuclear membrane results in altered chromosomal distribution.

Other than these factors, an absence of cytokinesis (a division of cytoplasm at the end of mitosis or meiosis) after the occurrence of normal karyokinesis (a division of nucleus during mitosis) is also linked to multinucleate blastomere formation.

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