The insect brain is specified by a conserved transcriptional program distinct from the segmental CNS
Year: 2026
Type: preprint
Abstract: The brain is the central processing center that integrates information to guide animal behavior, while the posterior CNS performs less central functions. To what degree this functional distinction is reflected in divergence of the genetic regulation remains unexplored, as well as the hypothesis of a distinct evolutionary origin of brain and trunk CNS. In insects, neuroblast biology is similar across the CNS, but the presence of brain-specific neuroblast types and differences in the gene sets involved in their spatial and temporal specification indicate divergence. However, a comprehensive and unbiased comparison of the regulatory code of brain versus trunk neuroblasts has been lacking. Here, we reveal the transcription factors expressed in insect embryonic neuroblasts by a combined single-cell analysis from the fly Drosophila melanogaster and the beetle Tribolium castaneum, for which we established a Gal4 enhancer trap system to generate a line marking NBs with tGFP. From the combined dataset of nearly 70,000 neuroblasts, we identified around 23,000 brain neuroblasts, from which we identified cell populations and their transcriptional signatures. We found 188 brain-specific TFs, including seven spatially restricted transcription factors not previously associated with neuroblasts ( Hmx, CG15CSC, CG32532, dmrtSSB, fD5SA, TfAP-2 , and Fer1 ). In addition to the expected canonical Type II NBs, we found two related clusters with intriguing transcriptional divergence. The large number of brain-specific TFs supports a profound divergence between the insect brain and posterior CNS. Together with recent work in vertebrates, our data confirm an ancient divergence of the brain from the trunk. Significance statement The brain integrates information to guide animal behaviour while the rear parts of the nervous system act mainly downstream. Although function and structures of the brain are quite distinct, they start their development in a similar way. Therefore, it has remained unclear how different the genetic regulation of the brain actually is. To answer this, we revealed the genetic program of brain stem cells at single-cell resolution across two insects — a fly and a beetle. We comprehensively identified key genetic regulators active in the brain but not the posterior nervous system, including several previously unknown ones. This divergence suggests that the brain is quite fundamentally different from the trunk CNS — a finding which resonates with recent studies from vertebrates.
Institutions: University of Göttingen, Max Delbrück Center
Language: English
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W7204243680