Efferent Projections of Prokineticin 2 Expressing Neurons in the Mouse Suprachiasmatic Nucleus

Chengkang Zhang,Qun-Yong Zhou,Kimberly K Truong,Michael N Nitabach

doi:10.1371/journal.pone.0007151

Chengkang Zhang, Qun-Yong Zhou + Show 2 more

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https://doi.org/10.1371/journal.pone.0007151

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Journal: PLoS ONE	Publication Date: Sep 28, 2009
Citations: 100	License type: CC BY 4.0

Affiliation: University of California, Irvine

Abstract

The suprachiasmatic nucleus (SCN) in the hypothalamus is the predominant circadian clock in mammals. To function as a pacemaker, the intrinsic timing signal from the SCN must be transmitted to different brain regions. Prokineticin 2 (PK2) is one of the candidate output molecules from the SCN. In this study, we investigated the efferent projections of PK2-expressing neurons in the SCN through a transgenic reporter approach. Using a bacterial artificial chromosome (BAC) transgenic mouse line, in which the enhanced green fluorescence protein (EGFP) reporter gene expression was driven by the PK2 promoter, we were able to obtain an efferent projections map from the EGFP-expressing neurons in the SCN. Our data revealed that EGFP-expressing neurons in the SCN, hence representing some of the PK2-expressing neurons, projected to many known SCN target areas, including the ventral lateral septum, medial preoptic area, subparaventricular zone, paraventricular nucleus, dorsomedial hypothalamic nucleus, lateral hypothalamic area and paraventricular thalamic nucleus. The efferent projections of PK2-expressing neurons supported the role of PK2 as an output molecule of the SCN.

Highlights

The primary mammalian circadian clock resides in the suprachiasmatic nucleus (SCN) of the hypothalamus
Previous studies have indicated that Prokineticin 2 (PK2) and its receptor prokineticin receptor 2 (PKR2) are important output components of the central circadian clock in the SCN [15,18,19,21]
We confirmed that a subset of PK2-expressing neurons in the SCN projected to many primary target areas of the SCN

Summary

Introduction

The primary mammalian circadian clock resides in the suprachiasmatic nucleus (SCN) of the hypothalamus. Dye tracing experiments have revealed that the primary efferent target areas of the SCN are quite limited and predominantly locate in the hypothalamus and the midline thalamus. The efferent projections of the mouse SCN correspond to what have been described in hamster and rat [4,6,7,8]. Both SCN subdivisions are believed to be capable of disseminating circadian information to the thalamus, hypothalamus and basal forebrain [9]

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Conclusion