DIGE based proteome analysis of mammary gland tissue in water buffalo (Bubalus bubalis): Lactating vis-a-vis heifer

• Identified protein evidences in lactating buffalo mammary tissue (first time)
• 29 differentially expressed proteins (DEPs) identified (21: lactating; 8: heifer)
• New DEPs: EEF1D, HSPA5, HSPD1, PRDX6, TF, GFPT1, AHCY, MFAP4 and PDCD6
• HSP27 was most upregulated (27 fold) during lactation.
• Major pathways (Ingenuity & MAS3): PPAR signaling, oxidative phosphorylation, P38 MAPK, JNK and ERK

Mammary gland is an exocrine and sebaceous gland made up of branching network of ducts that end in alveoli. Milk is synthesized in the alveoli and secreted into alveolar lumen. Mammary gland represents an ideal system for the study of organogenesis that undergoes successive cycles of pregnancy, lactation and involution. To gain insights on the molecular events that take place in pubertal and lactating mammary gland, we have identified 43 differentially expressed proteins in mammary tissue of heifer (non-lactating representing a virgin mammary gland), and lactating buffaloes (Bubalus bubalis) by 2D-difference gel electrophoresis (2D-DIGE) and mass spectrometry. Twenty one proteins were upregulated during lactation whereas 8 proteins were upregulated in heifer mammary gland significantly (p<0.05). Bioinformatics analyses of the identified proteins showed that a majority of the proteins are involved in metabolic processes. The differentially expressed proteins were validated by real-time PCR and Western blotting. We observed differential expressions of certain new proteins including EEF1D, HSPA5, HSPD1 and PRDX6 during lactation which have not been reported before. The differentially expressed proteins were mapped to available biological pathways and networks involved in lactation. This study signifies the importance of some proteins which are preferentially expressed during lactation and in heifer mammary gland.Biological significanceThis work is important because we have generated information in water buffalo (B. bubalis) for the first time which is the major milk producing animal in Indian Subcontinent. Out of a present production of 133 million tons of milk produced in India, contribution of buffalo milk is around 54%. Its physiology is somewhat different from the lactating cows. Buffalo milk composition varies from cow milk in terms of higher fat and total solid content, which confers an advantage in preparation of specialized cheese, curd and other dairy products. Being a major milk producing animal in India it is highly essential to understand the lactation associated proteins in the mammary gland of buffalo. In the present investigation our attempt has been to identify new protein evidences which are expressed in lactating buffalo mammary gland and have not been reported before. The findings reported in the present study will help in understanding the lactation biology of buffalo mammary gland in particular and the mammary gland biology in general.

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