https://www.ncbi.nlm.nih.gov/pubmed/30895322 Mol Biol Evol. 2019 Mar 20. pii: msz068. doi: 10.1093/molbev/msz068. [Epub ahead of print] Complete inactivation of sebum-producing genes parallels the loss of sebaceous glands in Cetacea. Lopes-Marques M1, Machado AM1, Alves LQ1,2, Fonseca MM1, Barbosa S1, Sinding MS3, Rasmussen MH4, Iversen MR4, Frost Bertelsen M5, Campos PF1,6, da Fonseca R6,7, Ruivo R1, Castro LFC1,2. Author information Abstract Genomes are dynamic biological units, with processes of gene duplication and loss triggering evolutionary novelty. The mammalian skin provides a remarkable case study on the occurrence of adaptive morphological innovations. Skin sebaceous glands, for instance, emerged in the ancestor of mammals serving pivotal roles, such as lubrication, waterproofing, immunity and thermoregulation, through the secretion of sebum, a complex mixture of various neutral lipids such as triacylglycerol, free fatty acids, wax esters, cholesterol and squalene. Remarkably, sebaceous glands are absent in a few mammalian lineages, including the iconic Cetacea. We investigated the evolution of the key molecular components responsible for skin sebum production: Dgat2l6, Awat1, Awat2, Elovl3, Mogat3 and Fabp9. We show that all analysed genes have been rendered non-functional in Cetacea species (toothed and baleen whales). Transcriptomic analysis, including a novel skin transcriptome from blue whale, supports gene inactivation. The conserved mutational pattern found in most analysed genes, indicates that pseudogenization events took place prior to the diversification of modern Cetacea lineages. Genome and skin transcriptome analysis of the common hippopotamus highlighted the convergent loss of a subset of sebum-producing genes, notably Awat1 and Mogat3. Partial loss profiles were also detected in non-Cetacea aquatic mammals, such as the Florida manatee, and in terrestrial mammals displaying specialized skin phenotypes such as the African elephant, white rhinoceros and pig. Our findings reveal a unique landscape of "gene vestiges" in the Cetacea sebum-producing compartment, with limited gene loss observed in other mammalian lineages: suggestive of specific adaptations or specialisations of skin lipids. And very interesting "Although adult whales have no covering of body hair, they acquire body hair temporarily as fetuses,"