Prolactin (PRL) and prolactin receptor (PRLR) genes and their role in poultry production traits

Prolactin (PRL), secreted from the anterior pituitary, plays extensive roles in osmoregulation, corpus luteum formation, mammogenesis, lactogenesis, lactopoiesis, and production of crop milk. In birds, prolactin (PRL) is generally accepted as crucial to the onset and maintenance of broodiness. All the actions of prolactin (PRL) hormone are mediated by its receptor (PRLR), which plays an important role in the PRL signal transduction cascade. It has been well established that the PRL gene is closely associated to the onset and maintenance of broody behavior, and could be a genetic marker in breeding against broodiness in chickens. Meanwhile, the prolactin receptor (PRLR) gene is regarded as a candidate genetic marker for reproductive traits. PRLR is also an important regulator gene for cell growth and differentiation. The identified polymorphism of this gene is mainly viewed in terms of egg production traits. Due to different biological activities attributed to PRL and PRLR, they can be used as major candidate genes in molecular animal breeding programs. Characterization of PRL and PRLR genes helps to elucidate their roles in birds and provides insights into the regulatory mechanisms of PRL and PRLR expression conserved in birds and mammals.