A Multi-Tissue Transcriptomic Atlas of River Buffalo with a Focus on the Genetic Underpinnings of Lactation Performance Across Four Lactation Stages in the Mammary Gland

The river buffalo is an economically important livestock species supplying milk and meat. However, a multi-tissue transcriptomic atlas for the key dairy river buffalo breeds, Murrah and Nili-Ravi, has not yet been established, and the lack of stable reference genes has hindered in-depth studies of their biological functions and the molecular mechanisms underlying key economic traits such as lactation. We established a multi-tissue gene expression atlas across 20 tissues and identified 717 housekeeping genes (HKGs), and RPL37A and EEF2 were further shown to be stable candidate reference genes under the conditions tested. We found 8368 tissue-specific genes (TSGs), predominantly enriched in the reproductive system. Exploratory analysis of mammary tissue (dry-period vs. public lactating samples, confounded by batch effects) revealed mammary-enriched hub genes including LALBA; these findings are preliminary and require validation. Dynamic analysis across lactation stages (early, peak, mid-, late) identified candidate genes including SEC14L2 and ACSM3. Phenotypic data showed strong negative correlations between milk yield and protein/fat content, and a positive correlation with lactose content. However, causal or regulatory roles were not inferred due to lack of paired individual-level data. Cross-dataset comparisons are descriptive only, and are not key conclusions. In summary, this study lays the foundation for advancing research in lactation trait genetics and functional genomics in river buffalo, with novel reference genes and lactation stage-specific transcriptional dynamics as its main contributions.