Introducing the brain: How human compares to primates (Introduction)

by David Turell , Friday, October 13, 2023, 19:51 (197 days ago) @ David Turell

Another review of the articles:

https://www.nature.com/articles/d41586-023-03192-2?utm_source=Live+Audience&utm_cam...

"Researchers have created the largest atlas of human brain cells so far, revealing more than 3,000 cell types — many of which are new to science.

***

"Kimberly Siletti, a neuroscientist now at the University Medical Center Utrecht in the Netherlands, and her team laid the cornerstone for the atlas by sequencing the RNA of more than 3 million individual cells from 106 locations covering the entire human brain, using tissue samples from three deceased male donors1. They also included one motor cortex dissection from a female donor that had been used in previous studies. Their analysis documented 461 broad categories of brain cell that included more than 3,000 subtypes.

***

"Neurons — cells in the brain and nervous system that send and receive signals — varied widely in different parts of the brain, suggesting different functions and developmental histories. The mix of neurons and other cell types also differed across each region; some cells were only found in specific locations. The brainstem — a relatively under-studied structure connecting the brain to the spinal cord — harboured a particularly high number of neuron types, says study co-author Sten Linnarsson, a molecular systems biologist at the Karolinska Institute in Stockholm, Sweden. “One of the big surprises here is how incredibly complex the brainstem is.”

"Other studies drilled into the mechanisms of gene regulation and expression in different cells...They analysed chemical markers that switch genes on or off in more than 500,000 individual cells. The various molecules that acted as switches enabled the team to identify nearly 200 brain cell types. Even the same gene in the same type of cell could have different characteristics across the brain. One gene was turned on with one switch at the front of the brain and with another at the back. “There are remarkable regional differences,” says study co-author Wei Tian, a computational biologist at the Salk Institute. (my bold)

***

"Ren and his colleagues used the cell-type data to predict how the genetic switches influence gene regulation and increase the risk of neurological diseases. For instance, in cells called microglia , which clear away dead or damaged cells, the presence of some genetic switches was strongly linked to risks of Alzheimer's disease. Such findings can be used to test whether particular genes or faulty switches contribute directly to the onset of disease. “This is made possible because we have — for the first time — delineated the genetic switches for hundreds of different cell types,” says Ren."

Comment: this is different view limited to just the human brain and its enormous complexity. Such complexity shows that that it is irreducibly complex and cannot have developed step-by- step as the Darwin theory proposes.