All dogs great and small

ODDs AND eNDs

All dogs great and small

A recent article in Current Biology (https://tinyurl.com/2p87pfzh also see commentary from Nature: https://tinyurl.com/3u3twua6) has shed light on how dogs came to be both so big and so small. the 40-fold variation in size from the largest Great Dane to the smallest Chihuahua is greater than any other mammal species on Earth. As the ancestors of dogs, ancient wolves differ in size to only a small degree, until recently it was presumed that the mutations that led to these extremes developed during the intensive period of dog breeding over the last 200 years. However, study by a large consortium of researchers from across the globe, has suggested as least some of these mutations are much more ancient. Plaissais et al. (2021) analysed the genomes of more than 1,400 canids, including ancient dogs, wolves, coyotes and 230 modern dog breeds. they identified a sequence variation associated with variation in body size in a DNA region involved in controlling levels of the IGF1 protein. IGF1 acts as a growth hormone and has long been known to be play a role in determining body size. the newly identified DNA variant comes in two alleles. Dogs with two copies of the large-bodied allele tend to weigh >25 kgs and have greater serum concentrations of IGF1. Furthermore, this relationship also holds true for other canids: wolves, foxes, jackals, indicating an ancient origin for the variant. this is not the entire story of how dog size is determined however. Future work includes determining the mechanism by which the variant regulates concentrations of IGF1 protein and identifying additional genetic determinants of dog size. IGF1 only accounts for about 15% of the variation between breeds – that is, it is only one of many mutations that have a small but additive effect on body size. together these variants determine whether a dog is small enough to fit into a handbag or large enough to pull a cart. the article has been published open access and can be downloaded for free:

Photo credit: Karolina VW for Unsplash

J Plassais et al. Natural and human-driven selection of a single noncoding body size variant in ancient and modern canids. Current

Biology, https://doi.org/10.1016/j.cub.2021.12.036, 2022

WINNER Article of 2021

Miranda Tong

"transarterial closure of a patent ductus arteriosus in a Corgi puppy"

December 2021 | Volume 32(4) | Page 39

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