Lecture 5: FGF10/Shh Importance Flashcards
Give 3 examples of the nuclei that the differentiated FGF10/Shh cells will occupy and their roles
The Suprachiasmatic nucleus (SCN) which contains neurons regulating the circadian cycle.
The Arcuate nucleus (AN) which contains neurons regulating energy metabolism.
The Tuberomammillary nucleus (TMN) which contains neurons that have a role in sleep/wake state.
What events follow the differential movement that causes the PM to move away?
An ingrowth of oral ectoderm grows underneath the developing forebrain & establishes a pouch-like structure.
FGF10+ cells above this pouch signal to it to up regulate the TF Lhx3.
Lhx3 expressing cells become Rathe’s pouch cells which develop into the anterior pituitary.
The FGF10+ cells form a ventral out pocketing called the infundibulum. These cells self-differentiate into the posterior pituitary (distal) & median eminence (proximal).
How do we know that proximity of Rathe’s pouch to the infundibulum are essential for proper growth and functioning of the hypothalamo-pituitary neuraxis?
Fu et al., 2017. Interference with shh signalling via cyclopamine.
This causes the pouch not to be close to the infundibulum nor does it express Lhx3 so hasn’t formed Rathe’s pouch.
The infundibulum doesn’t even form properly.
What is released from the posterior pituitary & what are their roles?
Vasopressin: water reabsorption regulation in the kidneys.
Oxytocin: associated with trust.
Both are released directly into the bloodstream.
What are the roles of the hypothalamic neurons & where do they project to?
Make neuro-secretory hormones.
They project to the posterior pituitary & median eminence.
What happens to the neuro-hormones sent to the ME?
They are released into the portal blood capillaries where they travel to the adjacent anterior pituitary & affect the release of the actual hormone in endocrine cells.
What are tanycytes?
FGF10+ cells that maintained into adulthood as radial glial-like cells at the proximal part of the infundibulum.
They’re involved in acute homeostasis and are believed to be a remnant of the early neuro-epithelial FGF10+ population.
How do tanycytes affect release of growth hormone?
They wrap around the end feet of the hypothalamic neurons that carry GHRH and only retract when you’re asleep allowing the GHRH to travel to the anterior pituitary & affect the release of GH.
Why is suspected that tanycytes are hypothalamic stem cells?
The body needs to adapt its biological needs at different points in life & since the hypothalamus is involved in regulating crucial elements of body homeostasis it might be useful if it could adapt to anticipate & meet changing conditions by developing new neurons at different points.
