Skin is a highly specialized barrier organ, which serves essential barrier, immune, and sensory functions and exhibits conserved structure. In addition, each species exhibits a unique skin transcriptional profile for adapting distinct environmental conditions and physiological demands. However, these transcriptional profiles across mammals remain incompletely understood. In this study, we integrated 61 publicly available skin RNA-seq datasets from eight mammalian species: human (Homo sapiens), macaque (Macaca fascicularis), mouse (Mus musculus), sheep (Ovis aries), goat (Capra hircus), donkey (Equus asinus), rabbit (Oryctolagus cuniculus), and pig (Sus scrofa). We identified a large number (2286 to 4588) of differentially expressed genes (DEGs) based on 10,504 one-to-one orthologous genes in all pairwise species comparisons. A total of 44 conserved genes were identified by integrating tissue specificity, expression variability, and mean expression level, which were enriched in epidermal development, keratinocyte differentiation, and desmosome organization. We also identified species-specific genes and transcription factors, such as STMN1 (donkey), COL1A1 (goat), and ACTN2 (mouse), which are associated with the cell cycle, extracellular matrix, and muscle contraction pathways, respectively. WGCNA further revealed goat-associated module 2 (M2) enriched in the negative regulation of angiogenesis. Collectively, this study provides a comprehensive cross-species transcriptional profile resource for mammalian skin, providing a valuable resource for understanding the regulatory plasticity underlying skin evolution across mammals.

The mammalian stomach has conserved digestive functions but also shows major anatomical and physiological differences among species. However, broad comparative transcriptomic analyses across mammals and across ruminant stomach chambers remain limited. Here, we collected and integrated 111 bulk RNA-seq datasets from 11 mammalian species (humans, mice, monkeys, dogs, horses, donkeys, pigs, cattle, deer, goats, and sheep) and analyzed 12,048 shared one-to-one orthologous genes. We identified 56 conserved genes mainly involved in translation, ribosome biogenesis, protein homeostasis, and mitochondrial function. Pairwise comparisons revealed extensive transcriptional differences, with 2070–7110 differentially expressed genes across species pairs, together with distinct species-associated transcription-factor activity patterns. We also identified 25 ruminant-enriched genes associated with epithelial differentiation, ion transport, mucosal defense, and metabolism. Analysis of 69 samples from the rumen, reticulum, omasum, and abomasum of sheep, goats, cattle, and deer showed clear chamber-associated transcriptomic differences. The abomasum had a distinct expression program, with 235 enriched genes related to hormone regulation, secretion, transport, and digestion. Weighted gene co-expression network analysis further identified different gene programs in the forestomach and abomasum. Together, these findings reveal conserved, species-associated, and chamber-associated transcriptional features of the mammalian stomach and provide a useful framework for understanding its molecular diversity.