New Study Reveals How “Selfish Genes” Regulate Insects

A new study sheds light on one of genetics' most persistent mysteries: how the workings of the so-called “selfish gene” could have controlled dangerous insect populations.

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Scientists hope that by studying the molecular foundation and operation of a selfish gene, they will be able to develop innovative techniques for controlling particular insects that are worldwide pests and disease carriers.

The study, conducted by an international team of scientists headed by the University of Sheffield, focuses on “meiotic drive,” which occurs when a selfish gene disrupts the usual inheritance pattern.

Meiosis is a form of cell division that produces gametes, or sperm and egg cells, which contain half of each parent’s genetic material. When they fuse during fertilization, they produce new offspring.

According to classical genetics, each gene's maternal and paternal variants in the gametes have an equal probability of being handed down to the offspring. However, meiotic drive overturns this process by increasing the likelihood of selfish genes successfully passing on their genetic code.

All genes are selfish, but some are more selfish than others. Meiotic drive is a powerful mechanism and, in the insect world, some selfish genes can have a major effect on the numbers of male and female offspring that are produced. Ultimately, this can cause insect populations carrying these selfish genes to go extinct. By studying how that happens at a fundamental level, scientists will be able to exploit that knowledge and put it to good use to control insect populations that are responsible for major disease outbreaks and food shortages.

Dr. Alison Wright, Principal Investigator, School of Biosciences, University of Sheffield

The Sheffield-led study looked at a selfish gene from the Malaysian stalk-eyed fly (Teleopsis dalmanni). The scientists used single-cell RNA sequencing to characterize gene expression in individual sperm cells as they formed, a novel method for studying the molecular basis of meiotic drive.

This novel approach allowed us to find several genes essential for normal sperm development whose activity are altered in the presence of the selfish gene. The selfish gene is able to damage the mobility of rival sperm that carry a Y chromosome, which results in fewer male offspring. Over time, this meiotic drive results in an extremely female-biased sex ratio where very few males are present, with severe consequences for the existence and fertility of the population.

Dr. Peter Price, Study Lead Author, School of Biosciences, University of Sheffield

The Malaysian stalk-eyed fly is not a pest but provides vital information on how meiotic drive and selfish genes work. Next, the scientists will use their novel technique to investigate the origins of this selfish gene and its long-term implications for insect populations.