Schinko, J. B. | Search bioRxiv

bioRxiv2026

foxQ2 marks fast-acting brain interneurons including a subset of dopaminergic neurons innervating mushroom bodies and central complex in the beetle Tribolium castaneum

The brain is one of the most complex animal organs and the development of the many different neuron types remains enigmatic. A set of brain-specific transcription factors is involved in brain patterning but their specific contributions mostly remain to be elucidated, including foxQ2II. This transcription factor is conserved in anterior neuroectodermal patterning of most animals while it has been lost from vertebrates. The contribution of foxQ2II-positive neurons to the adult brain has remained enigmatic. Here, we use our enhancer trap, immunostainings and our newly established beetle brainbow system to categorize Tc-foxQ2II-positive neurons into nine clusters with different projection patterns. All clusters contain neurons with the fast-activating neurotransmitters acetylcholine and glutamate while no Tc-foxQ2II positive neuron is GABA-ergic or serotonin-positive. Interestingly, we found that many dopaminergic neurons were Tc-foxQ2II positive and we homologize them with dopaminergic neurons of the PPL2c, PPM1 and PPL1 cluster described in the Drosophila brain. Our results show that Tc-foxQ2II marks subsets of fast-acting interneurons contributing to the higher order brain centers mushroom bodies and central complex. Taken together, our work expands the known functional range of foxQ2 genes from sensory and neurosecretory cell specification to interneurons involved in the function of higher order brain centers.

neuroscience↗

bioRxiv2018

Clonal analysis by tunable CRISPR-mediated excision

Clonal marking techniques based on the Cre/lox and Flp/FRT systems are widely used in multicellular model organisms to mark individual cells and their progeny, in order to study their morphology, growth properties and developmental fates. The same tools can be adapted to introduce specific genetic changes in a subset of cells within the body, i.e. to perform mosaic genetic analysis. Marking and manipulating distinct cell clones requires control over the frequency of clone induction, which is sometimes difficult to achieve. Here we present Valcyrie, a new method that replaces the conventional Cre or Flp recombinase-mediated excision of a marker cassette by CRISPR-mediated excision. A major advantage of this approach is that CRISPR efficiency can be tuned in a predictable fashion by manipulating the degree of sequence complementarity between the CRISPR guide RNA and its targets. We establish the method in the beetle Tribolium castaneum. We demonstrate that clone marking frequency can be tuned to generate embryos carrying single marked clones. The Valcyrie approach can be applied to a wide range of experimental settings, for example to modulate clone frequency with existing tools in established model organisms and to introduce clonal analysis in emerging experimental models.

genetics↗