Cellular taxonomy and spatial organization of the murine ventral posterior hypothalamus

Abstract

The ventral posterior hypothalamus (VPH) is an anatomically complex brain region implicated in arousal, reproduction, energy balance, and memory processing. However, neuronal cell type diversity within the VPH is poorly understood, an impediment to deconstructing the roles of distinct VPH circuits in physiology and behavior. To address this question, we employed a droplet-based single-cell RNA sequencing (scRNA-seq) approach to systematically classify molecularly distinct cell populations in the mouse VPH. Analysis of >16,000 single cells revealed 20 neuronal and 18 non-neuronal cell populations, defined by suites of discriminatory markers. We validated differentially expressed genes in selected neuronal populations through fluorescence in situ hybridization (FISH). Focusing on the mammillary bodies (MB), we discovered transcriptionally-distinct clusters that exhibit neuroanatomical parcellation within MB subdivisions and topographic projections to the thalamus. This single-cell transcriptomic atlas of VPH cell types provides a resource for interrogating the circuit-level mechanisms underlying the diverse functions of VPH circuits.

Tangential Intrahypothalamic Migration of the Mouse Ventral Premamillary Nucleus and Fgf8 Signaling

“…Some of our data suggest that the RM also contributes Nr4a2-positive migrating elements (but not Foxa1 expressing cells) to the dorsal premamillary nucleus, which forms within the perimamillary area (Puelles et al, 2012). We identified a primary multiplicity of cell types within the VPM population (at least Foxa1-positive, Nr4a2positive, and Foxa1/Nr4a2 double positive cells, plus other cells negative for both markers), consistently with a recent single cells transcriptomic analysis of the basal hypothalamus, which identified a diversity of molecular types within the adult VPM (Mickelsen et al, 2020). Finally, we investigated possible signaling mechanisms affecting the VPM migration, and identified an apparent collateral trophic role of FGF8 signal diffusing caudalwards out of the local median acroterminal domain.…”

“…In our descriptive results we combined data of several VPM markers and obtained the impression that there exist 3 or 4 migrating cell types (or more). The notion of diverse molecular types of VPM neurons has been corroborated recently by single-cell transcriptomic analysis of the adult basal hypothalamus, including the VPM (Mickelsen et al, 2020). Most of the VPM markers identified in the Mickelsen et al (2020) report only start to be expressed after the migration has finished, according to data at the Allen Developing Mouse Brain Atlas (see Supplementary Table 2 1 ).…”

“…The notion of diverse molecular types of VPM neurons has been corroborated recently by single-cell transcriptomic analysis of the adult basal hypothalamus, including the VPM (Mickelsen et al, 2020). Most of the VPM markers identified in the Mickelsen et al (2020) report only start to be expressed after the migration has finished, according to data at the Allen Developing Mouse Brain Atlas (see Supplementary Table 2 1 ). Because of their emphasis on late developmental gene markers, these authors did notice the postulated VPM migration (Puelles et al, 2012;Nouri and Awatramani, 2017), nor compared VPM markers with those of the RM area.…”

“…Its rostral infundibular relationship abuts the acroterminal hypothalamic domain (rostral end of the hypothalamus in the prosomeric model; Puelles et al, 2012 ; Puelles and Rubenstein, 2015 ; Diaz and Puelles, 2020 ). The VPM contains excitatory glutamatergic neurons, which display a diversity of molecular profiles, possibly related to its different projections ( Ziegler et al, 2002 ; Mickelsen et al, 2020 ). A field rich in inhibitory neurons surrounds the VPM, which corresponds to the tuberal terminal part of the dorsomedial hypothalamic nucleus (DM-T; Figure 1C ; Puelles et al, 2012 ).…”

“…In contrast, a number of embryonic markers label selectively VPM (including Foxa1 , Nr4a2 , Irx1 , Irx5 , Enc1 , Lmx1b , Nos1 , Pknox2 , absent otherwise at the ventral tuberal and intermediate tuberal areas), and, surprisingly, these are also present at the retromamillary hypothalamic basal microzone, which is the ventralmost basal component of the peduncular hypothalamus, and the neuromeric neighbor immediately caudal to the mamillary body (RM; green background in Figure 1C ; Shimogori et al, 2010 ; Puelles et al, 2012 ); see also Supplementary Table 2 . A differential molecular profile of various postnatal VPM cell types was described recently ( Mickelsen et al, 2020 ). These authors studied markers that start to be expressed at late embryonic or postnatal stages (according to the Allen Developing Mouse Brain Atlas; www.developingmouse.brain-map.org ).…”