Canine Genome Plasticity

Diversity of archetypes of mammals can be explained by massive invasion of retroelements in the genomes of the ancient ancestors. Among all existing mammalian species, dogs are characterized by the highest degree of phenotypic diversity and plasticity, which is as well explained by the fact that their retroelements were less silenced through the course of evolution and are easily activated.

Diversity in domestic dog phenotypes is associated with a variety in repertoire and locations of new insertions of repetitive elements:

SINEs are a major source of canine genomic diversity, with the most common element SINE_CAN, representing 7% of dog genome

Location of SINEs genome integration varies between breeds and serves as accurate breed-specific hallmark [Kirkness EF et al, 2005]

Brachycephaly (shortening of the snout and widening of the hard palate) is explained by LINE1 insertion into SMOC2 gene [Marchant et al, 2017]

Appendicular chondrodysplasia (legs shortening) is explained by LINE-1 mediated retrotransposition of FGF4 retrogene [Parker et al, 2009]

Activity of repeated elements was associated with disease in dogs:

Swedish Vallhund dogs develop retinopathy as a result of insertion of LINE-1 element into MERTK gene [Cooper et al, 2014]
SINE insertion in an intron of the FAM161A gene that creates a reading frame shift and exon skipping which is responsible for late onset progressive retinal atrophy in Tibetan spaniels [Downs LM et al, 2014]
SINE insertion in the HCRTR2 gene is associated with Canine narcolepsy in Doberman Pinschers and Labrador Retrievers [Lin L et al, 1999]
Amount of repetitive elements in circulating DNA was associated with tumor progression and poor prognosis in dogs [Gelati et al, 2014]