TY  - GEN
CY  - Heidelberg
ID  - heidok36323
Y1  - 2025///
N2  - Cellular behaviors involved in stem cell regulation, growth, differentiation, and development are
crucial progresses in the development and maintenance of lineages. Cells coordinate such
behavior through communications by various mechanisms, including direct cell-cell interactions
and diffusible signaling molecules, to synchronize their actions and maintain the health and
complexity of the entire organism. This perceived signaling subsequently directs molecular
programs consisting of specific sets of genes, which are activated by genomic cis regulatory
elements (CREs) in response to various signals, and encode proteins that guide and execute
critical processes such as cell differentiation, growth, and adaptation to environmental changes.
Therefore, understanding how these programs are encoded and regulated provides insight into
the fundamental mechanisms of cellular behavior.
The Drosophila testis provides an excellent model for this; two stem cells at the niche compete
for self-renewal signals, germline stem cell and somatic cyst stem cell, while maintaining a fine
balance. The germline will differentiate and progress through dramatic transcriptional and
genomic changes, all necessary for the formation of compacted and motile sperm. In the process,
the somatic cyst lineage supports spermatogenesis, a tightly controlled process that is
coordinated by extensive signaling between the two lineages.
Therefore, to understand the regulatory logic behind cellular decision making, I simultaneously
profiled the transcriptomes and chromatin accessibility profiles within 10,335 individual nuclei.
In doing so, I identify over 90% of the Drosophila protein-coding genome being transcribed in the
testis, with dynamics equal to published testis transcriptomes. Furthermore, I identified 46,619
accessible regions across all cell stages, with 14,577 of those regions showing differential
accessibility. Leveraging both modalities, I constructed the first testis-specific enhancer-driven
gene regulatory network (eGRN), revealing 103 activating and 44 repressing TF eRegulons in the
testis, with cell specificity. Validation of the testis eGRN by means of in vivo eRegulon TF
perturbations are consistent with their putative functions, or can be rationalized within the scope
of spermatogenesis.
Furthermore, cooperative regulation between eRegulons is characterized by the joint binding to
common regulatory regions to induce the expression of sets of differential targets throughout
spermatogenesis. Moreover, lineage specific CRISPR-mediated mutagenesis of either cooperating
ovo or klu TFs resulted in the downregulation of their common target stg, a mitotic inducer. This
reveals that eGRN prediction can facilitate the elucidation of novel roles for uncharacterized TFs
in the testis.
Lastly, by expanding on cell-cell communication, the previously not well characterized Wnt
pathway was predicted to be active in the testis, as well as its downstream effector pan/TCF. In
vivo characterization indicates that Wnt components are involved in the modulation of stem cell
numbers, in particular the GSCs.
A1  - van Nierop y Sanchez, Patrick
AV  - restricted
TI  - Building and exploring enhancer-gene regulatory networks governing Drosophila spermatogenesis
UR  - https://archiv.ub.uni-heidelberg.de/volltextserver/36323/
ER  -