Canonical Wnt signaling regulates patterning, differentiation and nucleogenesis in mouse hypothalamus and prethalamus

Abstract

The hypothalamus is a small, but anatomically and functionally complex region of the brain whose development is poorly understood. In this study, we have explored its development by studying the canonical Wnt signaling pathway, generating gain and loss of function mutations of beta-catenin (Ctnnb1) in both hypothalamic and prethalamic neuroepithelium. Deletion of Ctnnb1 resulted in an anteriorized and hypoplastic hypothalamus. Posterior structures were lost or reduced, and anterior structures were expanded. In contrast, overexpression of a constitutively active mutant form of Ctnnb1 resulted in severe hyperplasia of prethalamus and hypothalamus, and expanded expression of a subset of posterior and premamillary hypothalamic markers. Moderate defects in differentiation of Arx-positive GABAergic neural precursors were observed in both prethalamus and hypothalamus of Ctnnb1 loss of function mutants, while in gain of function mutants, their differentiation was completely suppressed, although markers of prethalamic progenitors were preserved. Multiple other region-specific markers, including several specific posterior hypothalamic structures, were also suppressed in Ctnnb1 gain of function mutations. Severe, region-specific defects in hypothalamic nucleogenesis were also observed in both gain and loss of function mutations of Ctnnb1. Finally, both gain and loss of function of Ctnnb1 also produced severe, non-cell autonomous disruptions of pituitary development. These findings demonstrate a central and multifaceted role for canonical Wnt signaling in regulating growth, patterning, differentiation and nucleogenesis in multiple diencephalic regions.

The cellular and molecular landscape of hypothalamic patterning and differentiation from embryonic to late postnatal development

“…19 and 20 ), as has been previously reported in nonneuronal cells that show high levels of canonical Wnt signaling 56 . This finding explains the previous observation that, although a massive increase in the number of NPC cells is seen in these mutants, only a modest increase is observed in EdU labeling, which labels S-phase NPC 23 . This demonstrates the power of using scRNA-seq in conjunction with the HyDD to analyze developmental phenotypes, in a manner that is far more rapid and comprehensive than conventional histological techniques.…”

“…We next sought to determine if HyDD could also be used to rapidly and comprehensively characterize mutants that regulate early stages of hypothalamic development and organization. As proof of concept, we performed scRNA-seq analysis on E12.5 Foxd1 CreGFP/+ ;Ctnnb1 ex3/+ mice, in which a constitutively active form of beta-catenin is overexpressed in Foxd1 -positive hypothalamic and prethalamic progenitors, leading to activation of canonical Wnt signaling in these cells and their descendants 23 . The same analysis was also with Foxd1 CreGFP/+ littermate controls.…”

“…The same analysis was also with Foxd1 CreGFP/+ littermate controls. These mice show broad activation of the canonical Wnt pathway effector Lef1 , a hyperplastic ventricular zone, and with the exception of a handful of posterior hypothalamic markers, show the loss of most regional markers in the hypothalamus and prethalamus 23 .…”

“…These datasets have been used as the basis for genetic studies that selectively disrupt the development of specific hypothalamic regions and/or cell types 23 – 27 , leading to the identification of novel functions for previously characterized hypothalamic regions or cell types 28 , 29 . However, these datasets have important limitations: they do not provide cellular resolution of gene expression data, and they do not efficiently measure the coexpression of multiple genes.…”

Effects of long-lasting social isolation and re-socialization on cognitive performance and brain activity: a longitudinal study in Octodon degus

“…In the nervous system, the canonical Wnt signalling pathway has been predominantly linked to embryonic development, but within the past few decades it has become clear that it also plays a major role in adult brain morphogenesis, differentiation, and synaptic activity 75 , 115 – 118 . In the hypothalamus, this pathway has been related to energy balance regulation and neurogenesis 115 , 117 . In our study, the hypothalamus analyses displayed that only β-catenin transiently increases in PI and CI, returning to CTL levels in CI-R female degus.…”