Ciabatti, E. | Search bioRxiv

bioRxiv2021

Relaxin/insulin-like family peptide receptor 4 (Rxfp4) expressing hypothalamic neurons modulate food intake and preference in mice

Relaxin/insulin-like-family peptide receptor-4 (RXFP4), the cognate receptor for insulin-like peptide 5 (INSL5), has been implicated in feeding behaviour as Rxfp4 knockout mice display shorter meal durations and reduced high fat diet (HFD) intake. Here, we generated transgenic Rxfp4-Cre mice to explore Rxfp4 expression and physiology. Using this model, we identified Rxfp4 expression in the central nervous system, including in the ventromedial hypothalamus (VMH). Intra-VMH infusion of INSL5 increased HFD and highly palatable liquid meal intake (HPM) of ad libitum fed wildtype mice. Single-cell RNA-sequencing of VMH Rxfp4-expressing cells (RXFP4VMH) defined a cluster of Rxfp4-labelled neurons expressing Esr1, Tac1 and Oxtr, alongside known appetite-modulating neuropeptide receptors (Mc4r, Cckar and Nmur2). Viral tracing demonstrated RXFP4VMH neural projections to the bed nucleus of the stria terminalis, paraventricular hypothalamus, paraventricular thalamus and central nucleus of the amygdala. Utilising designer receptors exclusively activated by designer drugs (DREADDs), we found that whole body chemogenetic inhibition (Di) of Rxfp4-expressing cells, mimicking native INSL5-RXFP4 signalling, increased intake of HFD and HPM, whilst activation (Dq), either at whole body level or specifically within the VMH, reduced HFD and HPM intake and altered food preference. Ablating VMH Rxfp4-expressing cells recapitulated the lower HFD intake phenotype of Rxfp4 knockout mice, resulting in reduced body weight. These findings identify a discrete Rxfp4-expressing neuronal population as a key regulator of food intake and preference and reveal hypothalamic RXFP4 signalling as a target for feeding behaviour manipulation.

physiology↗

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↗