Expression of GH, TSHβ, LHβ and FSHβ genes during fetal pituitary development in the pig

Summary

The development of the anterior pituitary gland involves the proliferation and differentiation of ectodermal cells in Rathke's pouch to generate distinct cell types, each of which produces its corresponding trophic hormone. Studying pituitary development will therefore reveal novel aspects of organogenesis. In the present study, we examined by in situ hybridization the expression of genes for anterior pituitary hormones during development of the fetal pig pituitary. We found that the β-subunit gene of thyroid-stimulating hormone (TSHβ) was first expressed at E40, (E = day of embryonal/fetal life), growth hormone (GH) mRNA appeared between E40 and E50, and the gonadotropin genes (LHβ and FSHβ) were expressed at E50. The transcripts for TSHβ, LHβ and FSHβ were abundantly expressed at about E80, while GH mRNA continued to be richly expressed until after birth. The GH gene was first expressed in the mantle layer of the anterior lobe, while the TSHβ and gonadotrophin (LHβ and FSHβ) mRNAs were found in the central and the basal regions of the anterior lobe, respectively. All of these mRNAs (GH, TSHβ, LHβ, and FSHβ) remained concentrated until the end of gestation in the area where they first appeared. The distinctive pattern of developmental expression of these hormone genes in the fetal pig anterior pituitary makes this tissue an excellent system in which to study tissue-specific gene activation and regulation.

Key words

Pig pituitary - in situ hybridization - adenohypophyseal hormones - ontogenesis - development