Persistent Mullerian duct syndrome DNA testing for the miniature schnauzer

The miniature schnauzer is a small, plucky and very lively little dog from the Kennel Club’s utility grouping, which reflects the origins of the breed as a versatile working dog. Schnauzers can be found in three size variants, of which the miniature is the smallest one, but their small sizes are balanced out by larger-than-life personalities, and these are by no means toy dogs!

The miniature schnauzer breed as a whole is one that is robust, hardy and healthy, and the average lifespan of dogs of the breed is between 12-15 years. However, there are several hereditary health conditions that can present within miniature schnauzer breed lines, which can serve to shorten the lifespan of affected dogs, and/or have implications for their health and quality of life.

One such condition is called persistent Mullerian duct syndrome, and this is a condition that can cause problems with the reproductive organs of male dogs of the breed. Female dogs can carry and pass the condition on to their male offspring (and pass carrier status onto female offspring) but they are not affected by the condition themselves.

There is a DNA testing scheme in place for persistent Mullerian duct syndrome in miniature schnauzers, which breeders can elect to undertake on their parent stock to identify any potential problems prior to breeding. This means that breeders can use this information to make an informed choice about mating matches to produce healthy litters.

In this article we will explain in detail how persistent Mullerian duct syndrome affects dogs, how miniature schnauzers can inherit the condition, and how to get a dog tested for the markers of the condition.

Read on to learn more about persistent Mullerian duct syndrome and DNA testing for the miniature schnauzer.

What is persistent Mullerian duct syndrome?

To understand persistent Mullerian duct syndrome in miniature schnauzers, first of all you have to understand what the Mullerian ducts are, and how they should work.

The Mullerian ducts are present in both male and female dogs during their in-utero foetal development, and when the embryo’s sex characteristics form into male and female, the Mullerian ducts change.

In female dogs, their Mullerian ducts grow to form their uterus, cervix and uterine tubes. In males, hormonal production from the newly-formed testes causes the Mullerian ducts to regress and be lost during development, which is totally normal and what is meant to happen.

However, when a male dog inherits persistent Mullerian duct syndrome, the Mullerian ducts don’t regress as they should when the embryo’s gender becomes established, which means that affected male pups develop female sex organs including a uterus, cervix and oviducts.

In terms of persistent Mullerian duct syndrome’s effect on the male sex organs themselves, around half of affected male dogs will have normal reproductive development with properly descended testes and full fertility, but the other 50% may develop cryptorchidism – a failure of one or both testes to descend – which can cause both infertility, and contribute to the development of testicular tumours.

Correcting persistent Mullerian duct syndrome in miniature schnauzers is tricky, and requires a complex surgery. However, by undertaking DNA testing for the markers of the condition in miniature schnauzers, dog breeders can ensure that only healthy dogs are bred from.

How is persistent Mullerian duct syndrome inherited in the miniature schnauzer?

Persistent Mullerian duct syndrome is an inherited health condition that is transmitted by means of sex-limited autosomal recessive heredity. This means that the pattern of status of the two parent dogs in any mating match is what dictates the status of the litter, but because this is a sex-linked hereditary disorder, male and female puppies with the same parents may have different statuses as females are unaffected by the condition, even if they carry the gene markers for it and can pass it on.

Here is how the sex-linked autosomal recessive heredity of persistent Mullerian duct syndrome in miniature schnauzers works:

• If both parent dogs are clear, their litter will also be clear.
• If both parent dogs are affected, their male pups will also be affected. Their female pups will be carriers, but will not be affected themselves.
• If both parent dogs are carriers, 50% of their offspring will be carriers too. 25% will be clear, and 25% of their male pups will be affected.
• If a carrier and an affected dog are bred, their female pups will be carriers. Their male pups will have a 50% chance of being carriers, and 50% of being affected.
• If a carrier and a clear dog are bred, 50% of their offspring will be carriers, and 50% clear.
• If a clear dog and an affected dog are bred, they will have a litter of carriers.

How to get a miniature schnauzer DNA tested for persistent Mullerian duct syndrome

You can’t tell just by looking if any dog is a carrier of persistent Mullerian duct syndrome, or for males, even if they might be affected if their testes descend normally. To find out the status of any given miniature schnauzer, you need to arrange a DNA test.

If you plan to breed from your dog, the other dog in the mating match should be tested too.

All you need to do to get a miniature schnauzer tested for persistent Mullerian duct syndrome is to book an appointment with your vet to allow them to take a DNA sample from your dog, which they will then send off to an approved testing laboratory, who will return a result of the dog’s status to their owner.