Tbx19, a tissue-selective regulator of POMC gene expression

Pituitary cell types arise in a temporally and spatially specific fashion, in response to combinatorial actions of transcription factors induced by tr ansient signaling gradients. The critical transcriptional determinants of t he two pituitary cell types that express the pro-opiomelanocortin (POMC) ge ne, the anterior robe corticotropes, producing adrenocorticotropin, and the intermediate lobe melanotropes, producing melanocyte-stimulating hormone ( MSH alpha), have remained unknown. Here, we report that a member of the T-b ox gene family, Tbx19 which is expressed only in the rostral ventral dience phalon and pituitary gland, commencing on e11.5, marks pituitary cells that will subsequently express the POMC gene and is capable of altering progres sion of ventral cell types and inducing adrenocorticotropin in rostral tip cells. It is suggested that Tbx19, depending on the presence of synergizing transcription factors, can activate POMC gene expression and repress the a lpha glycoprotein subunit and thyroid-stimulating hormone beta promoters.