Biology subjects

Hedley, J. G.

Publications and source records attributed to Hedley, J. G..

3 recordsLinked to original sources

bioRxiv2026

GenePT Revisited: Do Better Text Embeddings Make Better Gene Embeddings?

AO_SCPLOWBSTRACTC_SCPLOWGenePT introduced a simple recipe for gene representations: embed each genes natural-language description with a general-purpose text embedding model and reuse the resulting vectors across downstream tasks. Since GenePTs release, embedding models have improved rapidly, with many strong open and commercial encoders benchmarked on suites such as the Massive Text Embedding Benchmark (MTEB). We present a controlled "leaderboard" study that keeps the GenePT pipeline fixed and varies only the embedding backbone. We benchmark contemporary encoders on four diverse gene embedding tasks: gene-gene interaction prediction, gene property classification, cell type classification, and prediction of transcriptomic responses to unseen genetic perturbations. Across these settings, newer backbones consistently outperform the original GenePT backbone (text-embedding-ada-002), achieving improvements of 1-17%, while enabling fully reproducible research by avoiding API dependencies.

genomics↗

bioRxiv2026

Recognition in Confinement: The Dynamics of Homologous Gene Pairing

How can protein-independent, side-by-side alignment of homologous double-stranded DNA (ds-DNA) arise as an early step in genome repair and genetic exchange, and what determines their kinetics under confinement? Although recombination proteins are known to facilitate this process, experiments indicate that an initial side-by-side arrangement of homologs can occur even in their absence. Helical Coherence Theory (HCT) proposes that sequence-dependent distortions of the double helix lead to commensurate charge patterns between interacting dsDNAs, favouring homologous over non-homologous alignment. However, HCT has largely been developed for straight, rigid dsDNA rods, an approximation limited to roughly one persistence length ({ell}B {approx} 50 nm), leaving the question open as to how recognition manifests in longer, fluctuating chains. Moreover, the dynamics and timescales of homolog searching under confinement, and the internal dynamics of the paired state, such as transient formation of local unpaired regions ("bubbles") and end fraying, remain unexplored. Here we extend HCT to dsDNA chains of multiple persistence lengths under confinement using coarse-grained simulations with a custom HCT-based force field, in order to come closer to understanding how homologous genes pair in vivo. We simulate two homologous chains within spherical cavities of radii 0.3-1 times their free-space gyration radius under two limiting ionic conditions. We found that confinement warrants homologous pairing; it occurs on microsecond timescales and depends non-monotonically on confinement size, with an optimal confinement that accelerates pairing while avoiding tangled states and metastable trapping in an ion-dependent manner. To resolve pairing dynamics, we develop a kinetic theory and fit it to simulation trajectories, distinguishing rates of independent pairing modes underlying bubble formation and fraying. Together, these results support a physical mechanism for homologous pairing beyond the rigid-rod limit and suggest how confinement can promote both encounter and stabilisation within the HCT framework.

biophysics↗

bioRxiv2021

Nucleosome induced homology recognition in chromatin

One of the least understood properties of chromatin is the ability of its similar regions to recognise each other through weak interactions. Theories based on electrostatic interactions between helical macromolecules suggest that the ability to recognize sequence homology is an innate property of the non-ideal helical structure of DNA. However, this theory does not account for nucleosomal packing of DNA. Can homologous DNA sequences recognize each other while wrapped up in the nucleosomes? Can structural homology arise at the level of nucleosome arrays? Here we present a theoretical investigation of the recognition-potential-well between chromatin fibers sliding against each other. This well is different to the one predicted and observed for bare DNA; the minima in energy do not correspond to literal juxtaposition, but are shifted by approximately half the nucleosome repeat length. The presence of this potential-well suggests that nucleosome positioning may induce mutual sequence recognition between chromatin fibers and facilitate formation of chromatin nanodomains. This has implications for nucleosome arrays enclosed between CTCF-cohesin boundaries, which may form stiffer stem-like structures instead of flexible entropically favourable loops. We also consider switches between chromatin states, e.g., through acetylation/deacetylation of histones, and discuss nucleosome-induced recognition as a precursory stage of genetic recombination.

biophysics↗