Efficiency of cell-type specific and generic promoters in transducing oxytocin neurons and monitoring their neural activity during lactation

Keerthi Thirtamara Rajamani,Michelle Kim,Hala Harony-Nicolas,Lara Barteczko,Amanda B Leithead,Kristi Niblo,Marie Barbier,Arthur Lefevre,Valery Grinevich,Michael Peruggia

doi:10.1038/s41598-021-01818-x

Abstract

Hypothalamic oxytocin (OXT) and arginine-vasopressin (AVP) neurons have been at the center of several physiological and behavioral studies. Advances in viral vector biology and the development of transgenic rodent models have allowed for targeted gene expression to study the functions of specific cell populations and brain circuits. In this study, we compared the efficiency of various adeno-associated viral vectors in these cell populations and demonstrated that none of the widely used promoters were, on their own, effective at driving expression of a down-stream fluorescent protein in OXT or AVP neurons. As anticipated, the OXT promoter could efficiently drive gene expression in OXT neurons and this efficiency is solely attributed to the promoter and not the viral serotype. We also report that a dual virus approach using an OXT promoter driven Cre recombinase significantly improved the efficiency of viral transduction in OXT neurons. Finally, we demonstrate the utility of the OXT promoter for conducting functional studies on OXT neurons by using an OXT specific viral system to record neural activity of OXT neurons in lactating female rats across time. We conclude that extreme caution is needed when employing non-neuron-specific viral approaches/promoters to study neural populations within the paraventricular nucleus of the hypothalamus.

Highlights

Hypothalamic oxytocin (OXT) and arginine-vasopressin (AVP) neurons have been at the center of several physiological and behavioral studies
We included an OXT neuronspecific virus; the AAV1/2-OXTp-Venus[18], in which the expression of the Venus fluorescent protein is driven by the OXT promoter
To confirm that the high transduction rate is mostly attributable to the OXT promoter and not to the AAV1/2 serotype, we examined an additional virus with the same serotype but a different promoter, the AAV1/2-synapsin promoter (SYN)-tdTomato

Summary

Introduction

Hypothalamic oxytocin (OXT) and arginine-vasopressin (AVP) neurons have been at the center of several physiological and behavioral studies. We compared the efficiency of various adenoassociated viral vectors in these cell populations and demonstrated that none of the widely used promoters were, on their own, effective at driving expression of a down-stream fluorescent protein in OXT or AVP neurons. The hypothalamus, a brain structure located in the ventral forebrain, plays an essential role in neuroendocrine, autonomic and behavioral r egulation[1] It is composed of several small nuclei, each of which is characterized by various cell types that contribute to physiological and/or behavioral functions[2]. Among these nuclei are the paraventricular nucleus (PVN) and the supraoptic nucleus (SON) Both nuclei contain neurons that produce oxytocin (OXT) or vasopressin (AVP) neuropeptide, which are released from the somatodendritic compartment and/or the axonal terminals of these neurons[3]. Rather they are thought to be complementary, with OXT being more involved in attenuating reactivity to stressful experiences, while AVP is generally associated with arousal and defense, reviewed in3,9

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Results

Conclusion