Biology subjects

Alejevski, F.

Publications and source records attributed to Alejevski, F..

3 recordsLinked to original sources

bioRxiv2026

Natural genetic variation spans all predicted Rh5/Rh6 expression phenotypes in Drosophila R8 photoreceptors

Standing genetic variation is immediately available to selection, but how broad a range of phenotypes it can produce remains unknown for many traits. Here we address this question using the mutually exclusive Rhodopsin 5 (Rh5) and Rhodopsin 6 (Rh6) expression pattern in Drosophila R8 photoreceptors, a neuronal differentiation readout that permits enumeration of a finite set of predicted qualitative phenotypic changes. Wild flies and wild-derived inbred lines from the Drosophila Genome Reference Panel 2 (DGRP2) showed extensive variation in Rh5/Rh6 expression, including shifts in the relative abundance of Rh5- and Rh6-expressing R8s, Rh5/Rh6 co-expression, and loss of Rh5 or Rh6. Among 205 DGRP2 lines, we observed examples spanning all eight predicted qualitative phenotype categories. We also identified causal coding and regulatory variants, including alleles of sevenless, Rh5 and Rh6, and an intronic deletion in melted. These results show that standing natural variation can span the full predicted range of qualitative phenotypes in this system.

genetics↗

bioRxiv2025

A High-Resolution Atlas of the Brain Predicts Lineage and Birth Order Underly Neuronal Identity.

Gene expression shapes the nervous system at every biological level, from molecular and cellular processes defining neuronal identity and function to systems-level wiring and circuit dynamics underlying behaviour. Here, we generate the first high-resolution, single-cell transcriptomic atlas of the adult Drosophila melanogaster central brain by integrating multiple datasets, achieving an unprecedented tenfold coverage of every neuron in this complex tissue. We show that a neurons genetic identity overwhelmingly reflects its developmental origin, preserving a genetic address based on both lineage and birth order. We reveal foundational rules linking neurogenesis to transcriptional identity and provide a framework for systematically defining neuronal types. This atlas provides a powerful resource for mapping the cellular substrates of behaviour by integrating annotations of hemilineage, cell types/subtypes and molecular signatures of underlying physiological properties. It lays the groundwork for a long-sought bridge between developmental processes and the functional circuits that give rise to behaviour.

neuroscience↗

bioRxiv2025

A Role for Exaptation in Sculpting Sexually Dimorphic Brains from Shared Neural Lineages.

Sex differences in behaviours arise from variations in female and male nervous systems, yet the cellular and molecular bases of these differences remain poorly defined. Here, we take an unbiased, single-cell transcriptomic approach to uncover how sex shapes the adult Drosophila melanogaster brain. We show that sex differences do not result from large-scale transcriptional reprogramming but through fine-tuning of otherwise shared developmental templates via the sex-differentiating transcription factors Doublesex and Fruitless. We reveal, with unprecedented resolution, the extraordinary genetic diversity within these sexually dimorphic cell types and find birth order represents a novel axis of sexual differentiation. Neuronal identity in the adult reflects spatiotemporal patterning and sex-specific survival, with female-biased neurons arising early and male-biased neurons arising late. This pattern reframes dimorphic neurons as "paralogous" rather than "orthologous", suggesting sex leverages distinct developmental windows to build behavioural circuits and highlights a role for exaptation in diversifying the brain.

neuroscience↗