Role of Secreted Phosphoprotein 1 (SPP1) Gene in Bovines - A Review

Secreted phosphoprotein 1 (SPP1) popularly known as osteopontin (OPN) is a highly phosphorylated glycoprotein that is a prominent component of the mineralized extracellular matrices of bones and teeth. It is found in milk, plasma, urine and expressed in several tissues. Comparative sequence analysis of the bovine OPN cDNA in various species has revealed both conserved and non-conserved sequences. This gene is located in BTA 6 and having 7 exons. SPP1 gene has roles in bone mineralization, cancer metastasis, cell-mediated immune responses, inflammation and cell attachment. Polymorphisms in cattle and buffaloes were reported by various workers. SPP1 gene has potent roles in growth, production and reproduction of the animals. This gene is said to be associated with various traits like milk yield and milk compositions, growth and body weight, stillbirth and dystocia, mastitis and infections in bovine. OPN is reported to upregulate and promote the expression and secretion of Th1 cytokines. SPP1 variants are associated with mastitis resistance. SPP1 is involved in muscle regeneration after injury. There is increase in SPP1 expression in subclinical cows compared to control cows in Johne's disease. OPN has an important anti-apoptotic factor in many circumstances. As SPP1 gene is a good candidate gene for traits like stillbirth, dystocia, protein percentage of milk, twinning rate etc, it has great potential to be used in marker assisted selection and hence in improving genetic progress in cattle breeding.