Changes in Gene Expression during Pituitary Morphogenesis and Organogenesis in the Chick Embryo

Abstract

The anterior pituitary gland plays an important role in the regulation of many physiological processes. Formation of Rathke's pouch (RP), the precursor of the anterior pituitary, involves evagination of the oral ectoderm in a multi-step process regulated by cell interactions, signaling pathways, and transcription factors. Chickens are an excellent model to study development because of the availability of large sample sizes, accurate timing of development, and embryo accessibility. The aim of this study was to quantify mRNA expression patterns in the developing chicken anterior pituitary to evaluate the chicken embryo as a model for mammalian pituitary development. The expression profiles of 16 genes differentially expressed in RP and neuroectoderm were determined in this study. Among these, Pitx1, Pitx2, and Hesx1 mRNA levels were high on embryonic days (e) 2.5 to e3 in RP and decreased during development. Expression of Pit1 and Tbx19 mRNA in RP reached the highest levels by e7 and e6.5, respectively. Levels of glycoprotein subunit α mRNA increased beginning at e4. FGF8 mRNA showed the highest expression at e3 to e3.5 in neuroectoderm. BMP2 showed slight decreases in mRNA expression in both tissues during development, while Isl1 and Noggin mRNA expression increased in later development. Taken together, we present the first quantitative transcriptional profile of pituitary organogenesis. Our results will help further understanding of the functional development of this gland. Moreover, because of the high similarity in gene expression patterns observed between chicken and mouse, chickens could serve as an excellent model to study genetic and molecular mechanisms underlying pituitary development.

Direct and indirect roles of Fgf3 and Fgf10 in innervation and vascularisation of the vertebrate hypothalamic neurohypophysis

“…1D,H) (Pearson et al, 2011; Proszkowiec-Weglarz et al, 2011). Over this period, these FGF genes are not detected elsewhere in the chick diencephalon (Gimeno and Martinez, 2007; Pearson et al, 2011; Proszkowiec-Weglarz et al, 2011). …”

Development of cranial placodes: Insights from studies in chick

“…; Proszkowiec‐Weglarz et al . ). From these studies, it is clear that several signaling pathways like retinoic acid (RA), BMP, Sonic Hedgehog (Shh) and FGF might play a role in the development of the adenohypophysis.…”

“…The molecular mechanisms important for the development of the adenohypophysis have been studied more extensively in mouse and zebrafish (reviewed in Kelberman et al 2009;Pogoda & Hammerschmidt 2009) compared to chick. Nevertheless, several studies in chick have described expression patterns of various signaling molecules and transcription factors during the course of hypophyseal placode invagination and in Rathke's pouch, as well as hormone expression in the adenohypophysis (Maseki et al 2004;Ellestad et al 2006;Sjodal & Gunhaga 2008;Takagi et al 2008;Parkinson et al 2010;Proszkowiec-Weglarz et al 2011). From these studies, it is clear that several signaling pathways like retinoic acid (RA), BMP, Sonic Hedgehog (Shh) and FGF might play a role in the development of the adenohypophysis.…”

Expression Analysis of the PITX2 Gene and Associations between Its Polymorphisms and Body Size and Carcass Traits in Chickens

“…In chicken, the expression pattern of PITX2 is highly similar to that of mouse during pituitary development [18][19][20], and the PITX2 gene affects the late myogenic differentiation of the limb in the chick embryo [21]. These results suggested that the PITX2 gene is associated with the development of myocytes.…”