Body Size

Body Size

Dogs are the most size-diverse mammal species in the world. The smallest and largest dog breeds can differ in size by up to 40 times. Body size is a complex trait and is influenced by several different genes, as well as environmental factors such as nutrition and overall health during growth. Research has shown that a large part of the size differences between dog breeds can be explained by specific genetic variations. The H292 test analyses 5 known genetic variants that are associated with body size and is relevant for all breeds.

Genetic variants

One of the most predominant factors influencing body size is Insulin-like Growth Factor 1 gene (IGF1). This gene plays a major role in growth and is estimated to explain about 15% of the size variation seen between breeds. IGF1 produces a hormone that works together with growth hormone (GH) to regulate growth and development.

Identifying functional mutations associated with IGF1 has proven difficult. However, researchers have identified genetic factors that interact with IGF1 and influence its activity. One such factor is antisense long non-coding RNA (IGF1-AS), which helps regulate IGF1, and is strongly associated with body size variations. Another related gene is insulin-like growth factor 1 receptor (IGF1R). This gene produces the receptor that allows cells to respond to the IGF1 hormone. Variants in IGF1R can affect how strongly growth signals are received.

There are also factors not directly related to IGF1 that play a role in determining body size. Growth hormone receptor (GHR) is a factor for which two variants are tested. GHR encodes a receptor that allows cells to respond to GH.

The last variant included in the H292 test is stanniocalcin 2 (STC2). STC2 encodes a secreted glycoprotein hormone and is also involved in the IGF pathway.

Inheritance

Body size is a multifactorial trait. This means that the inheritance of the trait is influenced by multiple genes (polygenic) and environmental factors. There are multiple associated variants, and each genetic variant contributes a small part to the overall size of the dog. No single gene determines whether a dog will be small or large. Instead, body size is the result of the combined effects of several genes and environmental influences.

Important to know

Body size in dogs is influenced by multiple genes. While this test analyses several well-known variants associated with size, there may be additional genetic factors that are not yet discovered or included in the test.

Environmental factors such as diet, health, and care during puppyhood also play an important role in determining the final adult size of a dog.

Relevant Tests

• H292