Annexin A10: A New Genetic Defect in Wagyu Cattle

Introduction

Genetic defects or disorders, are inherited conditions where mutations in genes or regulatory regions of DNA impact the normal function or development of the body.

In Wagyu, we have tests available for 6 prior known disorders and these tests are used to manage the potential impact of the disorders by minimising their impact through structured breeding programs.

Importantly, additional undescribed genetic defects exist in the breeding population and these result in production losses from your system. Identifying these genetic defects and being able to test for and manage them in your herd, allows breeders to increase their productivity and reduce losses in animal performance, fertility and survival.

Developing the Annexin A10 genetic test

In 2026, a new genetic test will be available to AWA members that could significantly improve calving rates and increase the performance of high-value embryo programs. Testing for the Annexin A10 genetic defect, has the potential to affect the way Wagyu breeders select animals for breeding and manage their embryo programs.

Professor John Beever at the University of Tennessee Genomics Centre for the Advancement of Agriculture, has been working with around 230 DNA samples from Wagyu calves as part of the AWA Dead Calf Project. These samples have been provided by AWA members from all around the world to help us identify genetic defects that are causing loss of calves from the production system.

Professor Beever identified the occurrence of a known mutation in Annexin A10 (Sasaki et al., 2016) in a cohort of these samples and established a validation panel of positive and negative samples for DNA testing laboratories to use to prove their testing conditions for the AWA.

Annexin A10 mutations in other species can be associated with a range of problems, from immune system dysfunctions to fertility and specifically, embryonic mortality.

Preliminary estimates of the frequency of Annexin A10 mutation in the AWA recorded Wagyu population are around 6% (ie, 6% of animals are carriers or heterozygous for the mutation) This is consistent with the results of Sasaki from his 2016 paper which showed an estimated frequency of around 4-5% in the Japanese Black cattle population.

In this disorder, being a female carrier impacts on embryonic mortality. It appears that having 2 copies of the mutation is lethal, with no homozygous progeny surviving.

Discussion with Wagyu breeders over many years has indicated that levels of embryonic mortality and pregnancy loss in Wagyu are higher than they should be. Testing for the Annexin A10 mutation in Wagyu may significantly improve calving rate and profitability, particularly for high value embryo programs.

What is Annexin A10?

Annexins are a family of proteins that play critical roles in cellular processes such as inflammation, immune response, cellular growth, and cell death. Annexin A10 is an essential component of this family, and it is involved in regulating the function and stability of immune cells and tissues. Mutations or defects in the Annexin A10 gene can result in disruptions of these necessary cellular processes.

The 2016 study by Sasaki et al. identified a link between Annexin A10 mutations and embryonic mortality in cattle, particularly affecting early-stage pregnancies. This study suggested that Annexin A10 is a maternal genetic factor for embryonic mortality resulting in a higher rate of embryonic death, ultimately reducing reproductive efficiency in affected herds.

Impact on Wagyu Cattle Health and Productivity

The Annexin A10 mutation in Wagyu cattle may impact animal health, reproductive success, and overall productivity:

– Embryonic Mortality and Reproductive Challenges: As noted in Sasaki’s 2016 study, the Annexin A10 mutation is linked to embryonic mortality, which could manifest as early-stage pregnancy loss or reduced embryo viability. This would significantly impact calving rates and, ultimately, the genetic progress of breeding programs.
– Immune System Weakness: With Annexins having primary roles in immune system functioning, Wagyu cattle with this defect may have an impaired immune system, making them more susceptible to diseases, particularly during times of stress. This is unproven in Wagyu cattle.
– No effect on economically important carcase traits: Sasaki’s results suggested no effects on economically important carcase traits in Japanese black cattle.

Implications for Wagyu Breeding Programs

For Wagyu breeders, the arrival of genetic testing for the Annexin A10 mutation in 2026 is a major step toward managing and improving fertility and calving rate. With the ability to screen for this mutation, breeders can:

– Make Informed Breeding Decisions: By testing for this mutation, breeders can avoid passing on the genetic defect to future generations, helping maintain the health and productivity of their herds.
– Managing the Risk: For commercial breeders looking to source bulls to join with their cows, selecting those that are free from carrying the Annexin A10 mutation, will minimize the risks associated with the mutation in their herds.

Availability of the Genetic Test in 2026

The new genetic test for the Annexin A10 defect will be available to AWA members early in 2026. This test will allow Wagyu producers to screen individual animals for the mutation before making critical breeding decisions. This new test will be available only as a standalone test or as an add-on to other genotyping due to the nature of the test.

Given the dominant maternal effect of this mutation, we recommend breeders test their youngest and highest value females, particularly those intended for use in embryo programs where multiple progeny are expected. Likewise, bulls being used in high-value embryo programs should be screened so that they do not pass on the mutation to female progeny.

Seeding the database

AWA will be conducting a project to accumulate Annexin A10 results for high use, current and foundation sires, to assist with imputing the likelihood of carrier status across the population. We ask that you be prepared to provide additional DNA samples for key animals to allow testing of Annexin A10 if this is requested from you.

Read the full article in the latest edition of the Wagyu Quarterly Magazine, Summer 2025-2026

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WBVs are derived using genetic evaluation technology developed for the AWA, using the information contained within the AWA database. 
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