Kraft, R. | Search bioRxiv

bioRxiv2024

The intracellular Ca2+ sensitivity of transmitter release from neocortical boutons

Synaptotagmin 1 (Syt1) and Syt2 are the main Ca2+ sensors triggering synchronous release in the brain. The Ca2+-sensitivity of Syt2-triggered release has been studied in detail. However, for Syt1, the dominating isoform in the neocortex, quantitative detail is lacking. We measured the Ca2+-dependency of Syt1-triggered release at layer 5 pyramidal neuron synapses by laser photolysis of caged Ca2+. Syt1-triggered release had high Ca2+ affinity and positive cooperativity (EC50, 20 M; Hill coefficient, 3.57). It was steep in a dynamic range between [~]10 and [~]30 M that was covered by action potential-evoked release. A kinetic model reveals significant differences to models of Syt2-triggered release. Our results suggest that Syt1 optimizes neocortical synapses for high reliability at moderate local Ca2+ elevations and for high plastic controllability.

neuroscience↗

bioRxiv2022

Pervasive Under-Dominance in Gene Expression as Unifying Principle of Biomass Heterosis in Arabidopsis

Complex traits, such as growth and fitness, are typically controlled by a very large number of variants, which can interact in both additive and non-additive fashion. In an attempt to gauge the relative importance of both types of genetic interactions, we have turned to hybrids, which provide a facile means for creating many novel allele combinations. We focused on the interaction between alleles of the same locus and performed a transcriptomic study involving 141 random crosses between different accessions of the plant model species Arabidopsis thaliana. Additivity is rare, consistently observed for only about 300 genes enriched for roles in stress response and cell death. Regulatory rare-allele burden affects the expression level of these genes but does not correlate with F1 rosette size. Non-additive gene expression in F1 hybrids is much more common, with the vast majority of genes (over 90%) being expressed below parental average. Unlike in the additive genes, regulatory rare-allele burden in the non-additive gene set is strongly correlated with F1 rosette size, even though it only mildly covary with the expression level of these genes. Our study underscores under-dominance as the predominant gene action associated with emergence of rosette growth trajectories in the A. thaliana hybrid model. Our work lays the foundation for understanding molecular mechanisms and evolutionary forces that lead to dominance complementation of rare regulatory alleles.

genomics↗