de Malmazet, D. | Search bioRxiv

bioRxiv2023

Retinal origin of orientation but not direction selective maps in the superior colliculus

Neurons in the mouse superior colliculus ("colliculus") are arranged in ordered spatial maps. While orientationselective (OS) neurons form a concentric map aligned to the center of vision, direction-selective (DS) neurons are arranged in patches with changing preferences across the visual field. It remains unclear if these maps are a consequence of feed-forward input from the retina or local computations in the colliculus. To determine whether these maps originate in the retina, we mapped the local and global distribution of orientation- and direction-selective retinal ganglion cell boutons using in-vivo two-photon calcium imaging. We found that OS boutons formed patches that matched the distribution of OS neurons within the colliculus. DS boutons displayed less regional specializations, better reflecting the organization of DS neurons in the retina. Both eyes convey similar orientation but different DS inputs to the colliculus, as shown in recordings from retinal explants. These data demonstrate that orientation and direction maps within the colliculus are independent, implying that orientation maps are inherited from the retina, but direction maps require local circuits.

neuroscience↗

bioRxiv2020

Genomic stability of Self-inactivating Rabies

Transsynaptic viral vectors provide means to gain genetic access to neurons based on synaptic connectivity and are essential tools for the dissection of neural circuit function. Among them, the retrograde monosynaptic {Delta}G-Rabies has been widely used in neuroscience research. A recently developed engineered version of the {Delta}G-Rabies, the non-toxic self-inactivating (SiR) virus, represents the first tool for open-ended genetic manipulation of neural circuits. However, the high mutational rate of the rabies virus poses a risk that mutations targeting the key genetic regulatory element in the SiR genome could emerge and revert it to a canonical {Delta}G-Rabies. Such revertant mutations have recently been identified in a SiR batch. To address the origin, incidence and relevance of these mutations, we investigated the genomic stability of SiR in vitro and in vivo. We found that "revertant" mutations are rare and accumulate only when SiR is extensively amplified in vitro, particularly in suboptimal production cell lines that have insufficient levels of TEV protease activity. Moreover, we confirmed that SiR-CRE, unlike canonical {Delta}G-Rab-CRE or revertant-SiR-CRE, is non-toxic and that revertant mutations do not emerge in vivo during long-term experiments. HighlightsO_LIRevertant mutations are rare and do not accumulate when SiR is produced in high-TEVp expressing production cell lines C_LIO_LISiR is non-toxic in vivo C_LIO_LIRevertant SiR mutations do not accumulate during in vivo experiments C_LI

neuroscience↗