Analysis of three Ptx2 splice variants on transcriptional activity and differential expression pattern in the brain

Three different transcripts of the homeodomain gene termed pituitary homeob ox (Ptx) 2 (Pitx2/Brx/Rieg/Solurshin/Arp) were cloned from different specie s encoding proteins belonging to the paired-like family of homeodomain prot eins. Ptx2a (324 amino acids), Ptx2b (271 amino acids), and Ptx2c (318 amin o acids) share the C terminus, including the homeodomain, and have differen t N termini. Here we report the comparative analysis of all three different Ptx2 splice variants for their transcriptional activity and their expressi on pattern in the adult rat brain. Ptx2 is able to trans-activate via diffe rent model promoters in different cell lines. A mild difference in trans-ac tivating potential is observed among the splice variants, but the underlyin g mechanism is at present unknown. It is surprising that all Ptx2 transcrip ts displayed an identical expression pattern in the brain. This markedly re stricted pattern is limited to the following brain areas: the anterior and intermediate lobes of the pituitary gland, the subthalamic nucleus, the pos terior hypothalamic nucleus, the mammillary bodies, the red nucleus, and th e deep gray layer of the superior colliculus. The data presented suggest th at all variants of Ptx2 are involved in the development and regulation of d istinct neuronal cell groups and the pituitary gland.