Biochemical controls: placental controls (Introduction)

by David Turell , Wednesday, December 11, 2024, 17:56 (6 days ago) @ David Turell

A very complex temporary organ:

https://www.the-scientist.com/ts-digest/issue/what-s-the-difference-between-a-voltage-c...

"During gestation, the placenta takes on the roles of many of the fetus’ developing organs and serves as a barrier between parent and child. Critical to this is the outermost layer of the organ, the syncytiotrophoblast (STB), a single, multinucleated cell that forms from repeated fusion events between mononucleated cytotrophoblasts (CTB). In addition to producing pregnancy hormones, the STB plays important roles in nutrient and waste exchange and metabolism. Unlike many organs, which achieve multifunctionality through specialized cell types, the STB is a single giant cell with billions of individual nuclei.

“'Despite it being one cell, there might be specialized regions that are doing different functions,” said Madeline Keenen, a biochemist at Duke University. Researchers believe that one way this massive cell possibly achieves this is through specialized gene expression. “These nuclei could actually act as independent agents,” she added. Keenen, who has studied genome compaction and regulation in mononucleated cells, wanted to explore how the STB regulates its billions of genomes. Given the cell’s syncytial structure, single-cell approaches were limited, so she turned to single-nucleus RNA sequencing (snRNA-seq).

"In a bioRxiv preprint, Keenen and her colleagues reported their findings from snRNA-seq experiments on trophoblast organoids derived from human placental tissue.1 They identified three subpopulations of nuclei present in both models: STB-1, STB-2, and STB-3. The first population exhibited an intermediate gene expression profile, indicative of a population likely transitioning from CTB to STB. STB-2 nuclei expressed genes involved in oxygen sensing while STB-3 nuclei exhibited a more differentiated gene profile characterized by more STB markers and transport molecules.

"The nuclei subtypes identified by Keenen and her team are similar to the subpopulations that were recently identified in first trimester and full-term placental tissues, demonstrating the strength of these newer organoid models."

Comment: the placenta is a nine-month organ, supplying all of the fetus's needs, oxygen and nutrients and clearing CO2. It is impossible to imagine how this could be evolved stepwise as proposed by Darwin evolutionary mechanics. Only design fits.