TY  - GEN
UR  - https://archiv.ub.uni-heidelberg.de/volltextserver/33049/
Y1  - 2023///
ID  - heidok33049
AV  - public
TI  - Development and Evolution of the Mammalian Cerebellum at Single Cell Resolution
CY  - Heidelberg
A1  - Leiß, Kevin
N2  - Originally thought to only take part in motor control, the cerebellum emerged over the last decades
as an important organ in various higher cognitive functions, such as learning and speech. Besides this, the cerebellum is associated to various diseases, such as spinocerebellar ataxia, autism spectrum disorder, and medulloblastoma. The basic structure and connective properties of it
are well understood, but single-cell-technologies made it possible to study the cerebellum at higher
resolution. Many questions about molecular details of its development and evolution are still not
answered. Cerebella are present in all jawed vertebrates, though structural diversity is macroscopic
and microscopic detectable, such as the number of deep nuclei, the presence of the vermis, or the
mode of production of one of the most important cell types in the cerebellum - granule cells.
Using single-nucleus RNA-sequencing (snRNA-seq) and bioinformatic approaches, I studied cerebellum data of human, mouse (Mus musculus) and opossum (Monodelphis domestica). The dataset
contained samples spanning the organs development at high temporal resolution. It was possible
to track the differentiation of the major cerebellar neuronal and glial cell types, as well as identify
states and subtypes. This generated a comprehensive map of cellular complexity through eutherian
(human and mouse) and marsupial (opossum) development. Leveraging the evolutionary distance
of approximately 160 million years between the eutherian and marsupial lineage, conserved and
diverged cell type marker genes could be identified which might be promising candidates for understanding the basic blueprint of cerebellar cell type identity.
Stage correspondence mapping aligned the vastly different developmental time frames of the
three studied species and allowed the identification of a two-fold increase in Purkinje cell progenitors
in the human lineage, which might be connected to a recently identified human-specific secondary
ventricular zone progenitor pool.
It was possible to model the differentiation path of granule and Purkinje cells from early progenitors to mature neurons. Conserved and diverged gene expression trajectories were discovered.
Using in vitro and in vivo intollerance scores, I could show that genes which are dynamically
expressed during differentiation show higher functional constraint as non-dynamic genes, fitting to
previous bulk-RNA-seq studies, showing similar results across the development of the full organ.
Some orthologs with diverging patterns were disease-associated genes, which could have implications
on clinical research on conditions like autism spectrum disorders and medulloblastoma.
Furthermore, fundamental changes of gene expressions, established as gain or loss of expression
within a cell type and species, were detected. Affected genes showed decreased functional constraint,
verifying evolutionary principles on single cell scale.
Taken together, this study shows the strength of state of the art methodology combined with
high resolution developmental sampling in an evolution biological context to discover fundamental
principles of organ development at single-cell scale.
ER  -