Person:

Lu, Jenny

Genomic integrity is compromised by DNA polymerase replication errors, which occur in a sequence-dependent manner across the genome. Accurate and complete quantification of a DNA polymerase's error spectrum is challenging because errors are rare and difficult to detect. We report a high-throughput sequencing assay to map in vitro DNA replication errors at the single-molecule level. Unlike previous methods, our assay is able to rapidly detect a large number of polymerase errors at base resolution over any template substrate without quantification bias. To overcome the high error rate of high-throughput sequencing, our assay uses a barcoding strategy in which each replication product is tagged with a unique nucleotide sequence before amplification. This allows multiple sequencing reads of the same product to be compared so that sequencing errors can be found and removed. We demonstrate the ability of our assay to characterize the average error rate, error hotspots and lesion bypass fidelity of several DNA polymerases.

We can maintain some sense of direction in the dark by keeping track of our own movements, but when visual landmarks are available, our sense of direction is more accurate and stable. Moreover, we can learn new landmarks in new environments. What mechanisms reconcile self-movement information with ever-changing landmarks to generate a coherent sense of direction? Using whole-cell recordings and calcium imaging from Drosophila heading neurons, we show that each heading neuron is inhibited by visual cues in specific horizontal positions, with different visual maps in different individuals. Inhibition arises from presynaptic axons that form an all-to-all matrix of potential connections onto heading neurons. Visual input to the heading network can reorganize over minutes when visuo-motor correlations change, causing persistent changes in the brain’s heading map. Plasticity of sensory inputs, when combined with network attractor dynamics, should allow the brain’s spatial maps to incorporate sensory cues in new environments.