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News Article

Defective boar sperm linked to gene mutation


Immotile sperm, flagella with morphological abnormalities observed

Researchers at ETH Zürich have identified a gene mutation in boars responsible for the production of immotile spermatozoa with multiple morphological abnormalities of the flagella. It is hoped that this finding will help pig breeders exclude animals with this genetic defect from breeding in future.

A routine ejaculate screening of five breeding boars of the Swiss Edelschwein breed revealed the sperm they produced had shortened, crooked tails, rendering them immotile.  

Working with colleagues from the Vetsuisse Faculty at the University of Zurich, ETH researchers led by geneticist Hubert Pausch sequenced the entire genome of the five boars and compared it with that of healthy animals.

The gene affected is responsible for a protein involved in building the sperm tail. The mutation caused a defect in the production of the protein, resulting in proteins that were too short and thus not functional which in turn prevented the sperm tail from developing normally.

According to Pausch, although the mutation affects a gene sequence that is non-​coding, this sequence is a control element that is essential to correctly cut the RNA transcript of the gene and reattach the loose ends. The mutation leads to a defective transcript, which in turn means dysfunctional proteins are synthesised.

Because this mutation occurs at an unusual site, it was not immediately obvious to the researchers when they embarked on the study. According to Pausch there are only a handful of studies worldwide showing such DNA changes in livestock.

The findings however, will enable pig farmers to have their breeding boars tested for this mutation. Since the mutation is a recessive one, genetic testing will help farmers identify the boars and sows within the herd that have the recessive gene. These animals can be removed from the breeding pool to prevent the mutation from spreading further.

The genetic defect in question accumulates as a result of inbreeding, which causes recessive mutations to become phenotypically visible in a population more often. One of the objectives of breeding is to reduce this frequency. Eliminating all recessively inherited defects altogether is not feasible, according to Pausch, as genomic analyses show that there are hundreds of potentially fatal mutations in a wide variety of genes in breeding lines.

The study was conducted in collaboration with the Department of Reproductive Medicine at the Animal Hospital of the University of Zurich and Suisag, a service company for the Swiss pig industry.

Infertility due to defective sperm flagella caused by an intronic deletion in DNAH17 that perturbs splicing. Nosková A, Hiltpold M, Janett F, Echtermann T, Fang ZH, Sidler X, Selige C, Hofer A, Neuenschwander S, Pausch H. Genetics (2020) 217 (2): iyaa033, https://doi.org/10.1093/genetics/iyaa033

Article details

  • Date
  • 15 February 2021
  • Source
  • ETH Zürich
  • Subject(s)
  • Animal breeding and genetics