The fenestrae-associated protein Plvap regulates the rate of blood-borne protein passage into the hypophysis

• Published in: Development (Cambridge) Vol. 146; no. 23
• Main Authors: Gordon, Ludmila, Blechman, Janna, Shimoni, Eyal, Gur, Dvir, Anand-Apte, Bela, Levkowitz, Gil
• Format: Journal Article
• Language: English
• Published: England The Company of Biologists Ltd 02-12-2019
• Subjects: Fenestrae; Blood-brain barrier; Neuroendocrine; Pituitary; Circumventricular organs; Homeostasis; Zebrafish; PV1; Hypothalamus; Vascular permeability; Neurohypophysis; PV-1
• ISSN: 0950-1991; 1477-9129
• DOI: 10.1242/dev.177790

To maintain body homeostasis, endocrine systems must detect and integrate blood-borne peripheral signals. This is mediated by fenestrae, specialized permeable pores in the endothelial membrane. Plasmalemma vesicle-associated protein (Plvap) is located in the fenestral diaphragm and is thought to play a role in the passage of proteins through the fenestrae. However, this suggested function has yet to be demonstrated directly. We studied the development of fenestrated capillaries in the hypophysis, a major neuroendocrine interface between the blood and brain. Using a transgenic biosensor to visualize the vascular excretion of the genetically tagged plasma protein DBP-EGFP, we show that the developmental acquisition of vascular permeability coincides with differential expression of zebrafish
orthologs in the hypophysis versus brain. Ultrastructural analysis revealed that
mutants display deficiencies in fenestral diaphragms and increased density of hypophyseal fenestrae. Measurements of DBP-EGFP extravasation in
mutants provided direct proof that Plvap limits the rate of blood-borne protein passage through fenestrated endothelia. We present the regulatory role of Plvap in the development of blood-borne protein detection machinery at a neuroendocrine interface through which hormones are released to the general circulation.