FOLLOWING on the discovery of a genetic mutation in certain breeds of dairy cattle that links high milk production to infertility (Feedstuffs, Jan. 13), researchers in Germany reported another genetic defect linked to infertility in cattle.
To verify the small anomaly that may have "massive consequences," researchers from Technische Universitat Munchen (TUM) in Germany used the very latest gene sequencing techniques. Tests can now determine whether an animal is suitable for breeding or not.
The Fleckvieh is a breed of cattle that originated in the Alpine region. A robust animal, it is now found on every continent, with an estimated worldwide population of around 40 million, TUM said. In Germany, there are approximately 1 million Fleckvieh dairy cows.
"Their genomes can be traced back to a small number of key ancestors," Ruedi Fries, chair of animal breeding at TUM, said. "With artificial insemination, male breeding animals can produce more than 100,000 offspring."
This practice comes with risk, however. If the genetic make-up of any animal contains an unidentified defect, this characteristic will be passed on to future generations. TUM researchers have now discovered that a mutation in the TMEM95 gene on cattle chromosome 19 makes bulls effectively infertile, with a success rate for insemination of less than 2%.
"Otherwise, the animals are perfectly healthy and normal," Dr. Hubert Pausch, lead author of the study, pointed out. "The characteristic only manifests itself if bulls inherit the mutation from both the male and female side, i.e., they are homozygous for the defective gene. It is only in this case that the animals should be excluded from breeding."
Routine genetic testing for all breeding bulls has been underway since August 2012, TUM said.
As part of their study, the TUM researchers compared the genome of 40 subfertile animals with 8,000 breeding bulls of normal fertility levels. They discovered that the genetic defect can be traced back to one Fleckvieh animal born in 1966.
The TMEM95 gene encodes a protein on the surface of the sperm heads. The protein mediates the binding process between the sperm and egg cells. If it is missing, fertilization will not occur.
The discovery could have implications for species beyond cattle.
"Our findings indicate that genetic defects in TMEM95 could also cause infertility in men," Pausch said.
Scientists have been systematically studying the cattle genome since 2009. Unlike in humans, a small number of loci explain a large proportion of characteristics.
"This allows the genetic profile of breeding bulls to be mapped in detail — and individual weaknesses can be taken into account for breeding," Pausch said.
"Genetic analysis highlights the undesirable characteristics and also the diseases that animals pass on," Fries added. "With this knowledge, we can not only improve yield and quality but also improve animal health by identifying pathogenic gene variants and ensuring that they are not passed on to future animals."
The research was conducted as part of the Synbreed research cluster and was published in PLOS Genetics as "A Nonsense Mutation in TMEM95 Encoding a Nondescript Transmembrane Protein Causes Idiopathic Male Subfertility in Cattle."
TUM is one of Europe's leading research universities, with focus areas in the engineering sciences, natural sciences, life sciences and medicine, reinforced by schools of management and education. It is represented worldwide with a campus in Singapore as well as offices in Beijing, China; Brussels, Belgium; Cairo, Egypt; Mumbai, India, and Sao Paulo, Brazil.