Induction of an immortalized songbird cell line allows for gene characterization and knockout by CRISPR-Cas9

The zebra finch is a powerful model for several biological fields, particularly neuroscience and vocal communication. However, this species lacks a robust cell line for molecular biology research and reagent optimization. Here we describe a cell line, CFS414, generated from zebra finch embryonic fibroblasts using the SV40 large and small T antigens. This cell line demonstrates an improvement over previous songbird cell lines through continuous and density-independent growth, allowing for indefinite culture and monoclonal line derivation. Cytogenetic, genomic, and transcriptomic profiling established the provenance of this cell line and identified the expression of genes relevant to ongoing songbird research. Using this cell line, we demonstrated a stress-dependent localization response of the zebra finch song nuclei specialized gene, SAP30L, and disrupted endogenous gene sequences using S.aureus Cas9. The utility of this cell line enhances the molecular potential of the zebra finch and validates cell immortalization strategies in a songbird species.

Signature of gate-controlled magnetism and localization effects at Bi2Se3/EuS interface

Proximity of a topological insulator (TI) surface with a magnetic insulator (MI) can open an exchange gap at the Dirac point leading to exploration of surface quantum anomalous Hall effect. An important requirement to observe the above effect is to prevent the topological breakdown of the surface states (SSs) due to various interface coupling effects and to tune the Fermi level at the interface near the Dirac point. In this work, we demonstrate the growth of high-quality c-axis oriented strain-free layered films of TI, Bi2Se3, on amorphous SiO2 substrate in proximity to an MI, europium sulfide (EuS), that show stronger weak anti-localization response from the surface than previous studies with epitaxially interfaced heterostructures. Importantly, we find gate and magnetic field cooling modulated localization effects in the SSs, attributed to the position of interface Fermi level within the band gap that is also corroborated from our positron annihilation spectroscopy measurements. Furthermore, our experiments provide a direct evidence of gate-controlled enhanced interface magnetism in EuS arising from the carrier mediated Ruderman–Kittel–Kasuya–Yosida interactions across the Bi2Se3/EuS interface. These findings demonstrate the existence of complex interfacial phenomena affecting the localization response of the SSs that might be important in proximity engineering of the TI surface to observe surface quantum Hall effects.

Dissociating Sensory and Motor Components of Inhibition of Return

Two explanations for inhibition of return (IOR) have been proposed. The first is that IOR reflects inhibition of attentional processing at previously cued locations, resulting in altered sensory analysis. The second is that IOR reflects the inhibition of responses directed towards those previously cued locations. We used a variant of a double-saccade paradigm to dissociate these two proposed effects of IOR and attempted to reveal both effects within the context of a single experimental task. Subjects viewed a series of exogenous cues and then made a localization response to subsequent targets with either a target-directed saccade or a pointing response. Results were similar for both response modes. An important finding was that the pattern of IOR depended critically on how subjects reacted to the exogenous cues. Subjects either oriented to the cued locations (via saccades or pointing) prior to responding to the target (Respond), or passively viewed the cues before responding (Ignore). In the Respond condition, IOR was observed at the most recently cued position. Although this could be consistent with an altered sensory interpretation, it would also be consistent with a spatiotopic representation. In the Ignore condition, the sole inhibited location was not the most recently cued position, but the first cued position. This finding is surprising and in conflict with previous work with multiple exogenous cues. The data are discussed in relation to a number of prominent issues in the area of IOR and suggest important new constraints and boundary conditions.