July 18, 2014

Poor polar bodies typically go the way of that old container of Chinese take-out in your fridge and are eventually dumped. Thanks to a very clever study published in Cell, polar body transfer can prevent the transmission of inherited mitochondrial diseases. Waste not, want not.

The meiotic divisions of an oocyte result in the production of an egg in the extrusion of two very small polar bodies. These polar bodies have the same genetic material as the egg but have only a small number of organelles, including mitochondria. The DNA of mitochondria (mtDNA) can carry mutations that cause a variety of diseases. As mtDNA is maternally inherited due to the abundance of mitochondria in the oocyte, recent studies have focused on the replacement of mutant mtDNA with normal mitochondria to treat these inherited diseases. A recent paper tests the use of polar bodies as the source of donor genomes in a potential new method for mitochondrial replacement. As polar bodies have the same genome as the egg, but does not have mtDNA variants, they can successfully replace the genome in a recipient egg that already has normal mtDNA. Wang and colleagues have shown that polar body genome transfer successfully does just this, and provides a potential new therapy for preventing inherited mitochondrial diseases. The images above show the presence of mitochondria (red) in oocytes and polar bodies. Both polar bodies (PB1 and PB2) have far fewer mitochondria than the ooctyes.

Wang, T., Sha, H., Ji, D., Zhang, H., Chen, D., Cao, Y., & Zhu, J. (2014). Polar Body Genome Transfer for Preventing the Transmission of Inherited Mitochondrial Diseases Cell, 157 (7), 1591-1604 DOI: 10.1016/j.cell.2014.04.042
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