Dr. Sergiu Pașcă

I guess I'm a developmental neurobiologist by training and I've done a lot of circuit work in early days.

Of course, an obsession of mine was that especially for conditions as complex as autism and schizophrenia, we need to recapitulate some of the circuit properties of the brain.

So we now know that probably both for schizophrenia and for autism, it is very unlikely based on the evidence that we have so far that there are cells really missing from the brain.

We thought for a while that maybe some cells are missing or maybe other cells are in excess.

But now the studies that have been done, especially with single cell profiling of brains of patients that have already died, showed us that the composition of the brain, of the cortex in particular, it's very, very similar.

So it's unlikely that the cells are missing, but likely the way they're connected with each other is that makes a difference.

And of course, in the beginning, we were just making this clump of cells.

They're all for the cortex, but they're not connected to anything else.

So then came the idea of assembloids because most of the cells in the brain connect with cells across the nervous system.

And in fact, even more interestingly, cells do not reside in the place in which they're born in the nervous system.

We have the largest cell diversity of any other organ, almost 2000 cell types.

By the end of the first trimester, there are about 600 cell types in the human brain.

You know, think about the liver, right?

Maybe a couple of dozens.

The brain has to make, you know, hundreds of times more.

So how do you do that?

The only way is to actually make the cell types in different parts of the brain, provide local cues there,

And then once the cells have been specified, let them move and find their final position.

So the first assembly that we've actually made were of a very stereotypical canonical movement of cells in the nervous system, which has to do again with the cortex.

So the cortex, again, the outer layer of the brain has both excitatory and inhibitory neurons.