Selenoproteins contain the essential trace element selenium whose deficiency 
leads to major disorders including cancer, male reproductive system failure, or 
autoimmune thyroid disease. Up to now, 25 selenoprotein-encoding genes were 
identified in mammals, but the spatiotemporal distribution, regulation, and 
function of some of these selenium-containing proteins remain poorly documented. 
Here, we found that selenoprotein T (SelT), a new thioredoxin-like protein, is 
regulated by the trophic neuropeptide pituitary adenylate cyclase-activating 
polypeptide (PACAP) in differentiating but not mature adrenomedullary cells. In 
fact, our analysis revealed that, in rat, SelT is highly expressed in most 
embryonic structures, and then its levels decreased progressively as these 
organs develop, to vanish in most adult tissues. In the brain, SelT was 
abundantly expressed in neural progenitors in various regions such as the cortex 
and cerebellum but was undetectable in adult nervous cells except rostral 
migratory-stream astrocytes and Bergmann cells. In contrast, SelT expression was 
maintained in several adult endocrine tissues such as pituitary, thyroid, or 
testis. In the pituitary gland, SelT was found in secretory cells of the 
anterior lobe, whereas in the testis, the selenoprotein was present only in 
spermatogenic and Leydig cells. Finally, we found that SelT expression is 
strongly stimulated in liver cells during the regenerative process that occurs 
after partial hepatectomy. Taken together, these data show that SelT induction 
is associated with ontogenesis, tissue maturation, and regenerative mechanisms, 
indicating that this PACAP-regulated selenoprotein may play a crucial role in 
cell growth and activity in nervous, endocrine, and metabolic tissues.