The pituitary gland that synthesises and secretes pituitary hormones is an indispensable endocrine organ. Its development progresses by plural factors. Among them, neuronatin (NNAT), which was discovered in the neonatal mouse brain and is involved in neural development, was later revealed to be an abundantly expressing gene in the pituitary gland, but its role is yet elusive.
We analysed the expression profile of Nnat and its localisation in the rat pituitary. Level of Nnat-expression was high during the rat embryonic period but remarkably decreased after birth. In embryonic pituitary development, NNAT first appeared in the SOX2-positive stem/progenitor cells and disappeared at the initiation of terminal differentiation into hormone-producing cells. After birth, the number of NNAT positive cells remarkably decreased and most of them co-localized with SOX2 or PIT1, a commitment cell marker. Investigation of localisation in the organelles showed that NNAT widely localises in the mitochondria, peroxisome, lysosome and endoplasmic reticulum, but not in the Golgi.
The present study suggests that NNAT plays a role in stem/progenitor cells and supports progression of cellular differentiation existing in the subcellular organelles.