Genetic origins of Fido’s floppy ears explained after 140 years

The very traits that make dogs and other domestic animals endearing to us—floppy ears, curly tails, shorter muzzles—have puzzled scientists since Charles Darwin. Many distinguished scientists have posited explanations for the constellation of traits that developed after domestication, but none has convincingly proposed a genetic basis that covers all the observed changes. However, a deceptively simple explanation has now been suggested, by an interdisciplinary team in the July 2014 issue of Genetics. Wilkins and colleagues hypothesize that the cluster of phenotypic traits has its origins in neural crest cells, a class of stem cells that appear during early vertebrate embryogenesis at the dorsal crest of the neural tube and then migrate through the cranium and the trunk. They also suggest that selection for the desired trait of “tameness” has unintended effects on other body systems, producing, for example, floppy ears. The authors maintain that these traits can all be explained by subtle genetic changes that lead to reduction of neural crest cell activity. The hypothesis is based on review and evaluation of the rich literature on animal domestication, as well as on more recent experimental domestication studies involving fox and mink in Novosibirsk, Russia. Although the researchers identify several candidate genes, they readily acknowledge that “the precise genetic—and epigenetic—bases of the domestication syndrome require further elucidation,” providing geneticists with a project ripe for the picking. —Karyn Hede, News Editor

A new explanation for “Hobbit” man: Down syndrome

The discovery of diminutive skeletal remains in 2003 on the island of Flores in Indonesia created a media blitz when the humanoid was declared a new species that became extinct about 13,000 years ago. The tiny “Hobbit” man made headlines, but many scientists are skeptical that the remains represent a new species. Several alternative explanations for its characteristics have been proposed, including hormone deficiencies. A research team now reports that skeletal measurements of the most intact individual, referred to as LB1, are consistent with Down syndrome. The paper, published in the Proceedings of the National Academy of Sciences on 4 August 2014, notes that the abnormal features of LB1, including small skull, asymmetrical facial features, shortened femur, and flat feet, nicely match those reported for individuals with Down syndrome.

According to the authors, if LB1 is assumed to have had Down syndrome, then a case can be made that the skeleton falls within the expected range of height of modern people in South East Asia. The key evidence was LB1’s previously unpublished head-circumference measurements, which were compared with those of modern adults with Down syndrome. The authors also analyzed data on the facial asymmetry and tooth wear, which they say are consistent with Down syndrome, as well as on the femur length, which is short relative to the other extremities. —Karyn Hede, News Editor

Genetics in Medicine | Mission Statement

Genetics in Medicine is a monthly journal committed to the timely publication of:

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