Reduced VIP Expression Affects Circadian Clock Function in VIP-IRES-CRE Mice (JAX 010908)

Abstract

<jats:p> Circadian rhythms are programmed by the suprachiasmatic nucleus (SCN), which relies on neuropeptide signaling to maintain daily timekeeping. Vasoactive intestinal polypeptide (VIP) is critical for SCN function, but the precise role of VIP neurons in SCN circuits is not fully established. To interrogate their contribution to SCN circuits, VIP neurons can be manipulated specifically using the DNA-editing enzyme Cre recombinase. Although the Cre transgene is assumed to be inert by itself, we find that VIP expression is reduced in both heterozygous and homozygous adult VIP-IRES-Cre mice (JAX 010908). Compared with wild-type mice, homozygous VIP-Cre mice display faster reentrainment and shorter free-running period but do not become arrhythmic in constant darkness. Consistent with this phenotype, homozygous VIP-Cre mice display intact SCN PER2::LUC rhythms, albeit with altered period and network organization. We present evidence that the ability to sustain molecular rhythms in the VIP-Cre SCN is not due to residual VIP signaling; rather, arginine vasopressin signaling helps to sustain SCN function at both intracellular and intercellular levels in this model. This work establishes that the VIP-IRES-Cre transgene interferes with VIP expression but that loss of VIP can be mitigated by other neuropeptide signals to help sustain SCN function. Our findings have implications for studies employing this transgenic model and provide novel insight into neuropeptide signals that sustain daily timekeeping in the master clock. </jats:p>

Dual-Color Single-Cell Imaging of the Suprachiasmatic Nucleus Reveals a Circadian Role in Network Synchrony

“…We have characterized and validated this line previously (Fan et al, 2015;Lee et al, 2015). Note that two recent studies report hypomorphic expression of VIP and/or AVP in Avp-IRES2-Cre (JAX #023530) and Vip-IRES-Cre (JAX #010908) mice (Cheng et al, 2019;Joye et al, 2020). The Vip tm1(cre)Zjh /J line (JAX #010908) originates from a C57BL/6 X 129S4/SvJae F1 hybrid background.…”

“…The AVP-Cre JAX #023530 line is also different from the AVP-Cre line used in our work (Pei et al, 2014). All Cre mouse driver lines reported here were used in the heterozygous condition, which did not affect circadian rhythm phenotypes, consistent with Cheng et al (2019) and Joye et al (2020). The mouse lines used in this work were backcrossed and maintained in a C57BL/6N background in order to maintain an isogenic background with the ES cells used for gene targeting (described below).…”

VIP interneurons regulate olfactory bulb output and contribute to odor detection and discrimination

“…Heterozygous VIP-Cre mice were used in our study. It is reported that the amount of VIP is reduced in VIP-Cre mice in the suprachiasmatic nucleus (Joye et al, 2020). To examine whether VIP expression in the OB decreased in VIP-Cre mice, we performed qRT-PCR analysis to detect VIP expression.…”

Deletion of Six3 in post-proliferative neurons produces weakened SCN circadian output, improved metabolic function, and dwarfism in male mice

“…Using conditional KO mice (Cre-LoxP system) comes with numerous potential caveats to consider in data interpretation [ 43 , [73] , [74] , [75] , [76] , [77] , [78] ]. We have recently further validated the effectiveness of the Synapsin cre -allele for inducing recombination of the Six3 flox -allele throughout the brain, including the SCN, PVN, and PeVN [ 25 ].…”