Structural and molecular characterization of paraventricular thalamic glucokinase‐expressing neuronal circuits in the mouse

Abstract

The thalamic paraventricular nucleus (PVT) is a structure highly interconnected with several nuclei ranging from forebrain to hypothalamus and brainstem. Numerous rodent studies have examined afferent and efferent connections of the PVT and their contribution to behavior, revealing its important role in the integration of arousal cues.However, the majority of these studies used a region-oriented approach, without considering the neuronal subtype diversity of the nucleus. In the present study, we provide the anatomical and transcriptomic characterization of a subpopulation of PVT neurons molecularly defined by the expression of glucokinase (Gck). Combining a genetically modified mouse model with viral tracing approaches, we mapped both the anterograde and the retrograde projections of Gck-positive neurons of the anterior PVT (Gck aPVT ).Our results demonstrated that Gck aPVT neurons innervate several nuclei throughout the brain axis. The strongest connections are with forebrain areas associated with reward and stress and with hypothalamic structures involved in energy balance and feeding regulation. Furthermore, transcriptomic analysis of the Gck-expressing neurons revealed that they are enriched in receptors for hypothalamic-derived neuropeptides, adhesion molecules, and obesity and diabetes susceptibility transcription factors.Using retrograde labeling combined with immunohistochemistry and in situ hybridization, we identify that Gck aPVT neurons receive direct inputs from well-defined hypothalamic populations, including arginine-vasopressin-, melanin-concentrating hormone-, orexin-, and proopiomelanocortin-expressing neurons. This detailed anatomical and transcriptomic characterization of Gck aPVT neurons provides a basis for functional studies of the integration of homeostatic and hedonic aspects of energy homeostasis, and for deciphering the potential role of these neurons in obesity and diabetes development.

Molecular and spatial profiling of the paraventricular nucleus of the thalamus

“…We also report here that the glucokinase (Gck) gene is most highly expressed in the PVT3 AL subtype, potentially linking recent reports of the unique attributes of glucokinase-expressing aPVT neurons (aPVT Gck ) to the PVT3 subtype [27,33]. NAcprojecting aPVT Gck neurons were shown to be activated by hyperglycemic conditions and negatively modulate sucrose-seeking behavior [27].…”

“…Clusters were characterized by referencing top gene markers from each cluster with their spatial expression from Allen Brain Atlas ISH data and previous literature (Figure 1—figure supplement 2b, c, mouse.brain-map.org) [32]. From this comparison, we found that PVT neurons (4,067 nuclei; 62.0% of all neurons) expressed markers such as Gck , C1ql3 and Hcn1 , and were thus represented in neuron clusters 0, 2, 3 and 4 (Figure 1—figure supplement 2c, h) [33–35]. Neurons associated with other brain regions surrounding the PVT and represented in our sample include: MD (cluster 1; 1,003 nuclei, 15.3% of neurons), IMD (cluster 5; 500 nuclei, 7.62% of neurons), principal nucleus of the posterior bed nucleus of the stria terminalis (BSTpr; cluster 6; 496 nuclei, 7.57% of neurons), and habenula (Hb; cluster 7; 489 nuclei, 7.46% of neurons) (Figure 1—figure supplement 2d-g, h, Supp.…”

“…In conclusion, while there have been some investigations into the molecular organization of the PVT, here we have provided the first comprehensive molecular and spatial profiling of cell types across the entirety of the PVT [29, 33, 134]. The PVT is a critical integrative node linking circuits of internal and external processing with those involved in arousal signaling, as well as instrumental and Pavlovian behavioral control [2–4, 135].…”

Cerebrospinal Fluid Protein Biomarker Discovery in CLN3

“…Biomarkers with ≥ 2-fold differential expression, and per our Pubmed search not previously associated with other neurological conditions or processes include: FAM217B (family with sequence similarity 217 member B), QRICH2 (glutamine rich 2), KRT16 (keratin 16), ZNF333 (zinc finger protein 333). FAM217B has been reported to have repressed expression in ulcerative colitis and differentially expressed in glucokinase-positive neurons . QRICH2 regulates the formation of sperm flagella and when absent is associated with male infertility .…”

“…FAM217B has been reported to have repressed expression in ulcerative colitis 59 and differentially expressed in glucokinase-positive neurons. 60 QRICH2 regulates the formation of sperm flagella and when absent is associated with male infertility. 61 Variants in its homologue gene, QRICH1, are linked to a neurodevelopmental short stature syndrome.…”