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Expression patterns of Shh, Ptc2, Raldh3, Pitx2, Isl1, Lim3 and Pax6 in the developing chick hypophyseal placode and
1Umeå Center for Molecular Medicine, Building 6M, 4th Floor, Umeå University, S-901 87 Umeå, Sweden.
Insights
This study maps key gene expression patterns during early adenohypophysis development in chick embryos. It reveals the spatial and temporal roles of Sonic hedgehog (Shh) signaling and transcription factors in Rathke's pouch formation.
Area of Science:
- Developmental Biology
- Molecular Biology
- Neuroscience
Background:
- The adenohypophysis originates from Rathke's pouch, an invagination of the hypophyseal placode.
- Hedgehog (Hh) and retinoic acid (RA) signaling, along with transcription factors, are implicated in adenohypophysis development.
Purpose of the Study:
- To investigate the expression patterns of Shh, Ptc2, Raldh3, Pitx2, Isl1, Lim3, and Pax6 during early chick adenohypophysis development.
- To elucidate the roles of these genes in Rathke's pouch formation and differentiation.
Main Methods:
- Analysis of gene expression in chick embryos from the head fold stage to embryonic day 4.5.
- Utilized techniques to visualize the expression patterns of specific genes (Shh, Ptc2, Raldh3, Pitx2, Isl1, Lim3, Pax6).
Main Results:
- Ptc2 expression was observed in prospective hypophyseal placodal cells early on, with Shh expressed in the underlying mesoderm.
- Shh and Ptc2 maintained expression in tissues surrounding and within the developing adenohypophysis.
- Differential expression of transcription factors (Pitx2, Isl1, Lim3, Pax6) and Raldh3 was detailed within the Rathke's pouch, indicating distinct roles in anterior/posterior development.
Conclusions:
- Sonic hedgehog signaling and specific transcription factors are dynamically expressed during adenohypophysis development.
- The findings provide a detailed spatiotemporal map of gene expression crucial for understanding pituitary gland formation.
- This expression map serves as a foundation for further research into the genetic regulation of adenohypophysis development.
Abstract:
The adenohypophysis is derived from a structure called the Rathke's pouch, which is an invagination of the hypophyseal placode. Hedgehog (Hh) and retinoic acid (RA) signals as well as several transcription factors have been suggested to play a role in the development of the adenohypophysis. We have therefore examined the expression pattern of Sonic hedgehog (Shh), the hedgehog receptor Patched2 (Ptc2), the retinoic acid producing enzyme Retinaldehyde dehydrogenase3 (Raldh3) and four transcription factors, Pitx2, Isl1, Lim3 and Pax6 in chick embryos from head fold stage to embryonic day (E) 4.5. We show that already at the head fold stage, Ptc2 is expressed in prospective hypophyseal placodal cells and that Shh is expressed in the underlying mesoderm. Moreover, Shh continues to be expressed in tissues surrounding the prospective adenohypophysis, and Ptc2 is expressed in prospective hypophyseal cells. Lim3 and Pax6 are expressed from stage 10 in the prospective hypophyseal placode, whereas Pitx2 starts to be expressed before stage 10. Pitx2 is together with Pax6 expressed in the entire domain of the Rathke's pouch. Raldh3 is detected at the 20 somite stage and is together with Lim3 expressed in the anterior part of the Rathke's pouch. Isl1 is expressed in the most posterior part of the hypophyseal ectoderm in a complementary pattern to Raldh3 and Lim3.
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