Parallel Independent Losses of G-Type Lysozyme Genes in Hairless Aquatic Mammals

The study examined the evolution of goose-type (g-type) lysozyme genes across over 250 mammals, revealing widespread losses of either Lyg1 or Lyg2 genes in various taxa, particularly in fully aquatic mammals like cetaceans and sirenians. These losses were confirmed through the presence of loss of function mutations. Despite these gene losses, g-type lysozymes showed stronger purifying selection compared to chicken-type lysozymes, indicating a conserved function. The evolutionary loss of g-type lysozymes in hairless aquatic mammals was suggested to be related to their lack of body hair, as Lyg2 expression has been linked to hair follicle development and hair loss.