Reductions in hypothalamic Gfap expression, glial cells and α-tanycytes in lean and hypermetabolic Gnasxl-deficient mice

Abstract

BackgroundNeuronal and glial differentiation in the murine hypothalamus is not complete at birth, but continues over the first two weeks postnatally. Nutritional status and Leptin deficiency can influence the maturation of neuronal projections and glial patterns, and hypothalamic gliosis occurs in mouse models of obesity. Gnasxl constitutes an alternative transcript of the genomically imprinted Gnas locus and encodes a variant of the signalling protein Gαs, termed XLαs, which is expressed in defined areas of the hypothalamus. Gnasxl-deficient mice show postnatal growth retardation and undernutrition, while surviving adults remain lean and hypermetabolic with increased sympathetic nervous system (SNS) activity. Effects of this knock-out on the hypothalamic neural network have not yet been investigated.ResultsRNAseq analysis for gene expression changes in hypothalami of Gnasxl-deficient mice indicated Glial fibrillary acid protein (Gfap) expression to be significantly down-regulated in adult samples. Histological analysis confirmed a reduction in Gfap-positive glial cell numbers specifically in the hypothalamus. This reduction was observed in adult tissue samples, whereas no difference was found in hypothalami of postnatal stages, indicating an adaptation in adult Gnasxl-deficient mice to their earlier growth phenotype and hypermetabolism. Especially noticeable was a loss of many Gfap-positive α-tanycytes and their processes, which form part of the ependymal layer that lines the medial and dorsal regions of the 3rd ventricle, while β-tanycytes along the median eminence (ME) and infundibular recesses appeared unaffected. This was accompanied by local reductions in Vimentin and Nestin expression. Hypothalamic RNA levels of glial solute transporters were unchanged, indicating a potential compensatory up-regulation in the remaining astrocytes and tanycytes.ConclusionGnasxl deficiency does not directly affect glial development in the hypothalamus, since it is expressed in neurons, and Gfap-positive astrocytes and tanycytes appear normal during early postnatal stages. The loss of Gfap-expressing cells in adult hypothalami appears to be a consequence of the postnatal undernutrition, hypoglycaemia and continued hypermetabolism and leanness of Gnasxl-deficient mice, which contrasts with gliosis observed in obese mouse models. Since α-tanycytes also function as adult neural progenitor cells, these findings might indicate further developmental abnormalities in hypothalamic formations of Gnasxl-deficient mice, potentially including neuronal composition and projections.Electronic supplementary materialThe online version of this article (doi:10.1186/s13041-016-0219-1) contains supplementary material, which is available to authorized users.

Ablating astrocyte insulin receptors leads to delayed puberty and hypogonadism in mice

“…Meanwhile, the expression levels of IR mRNA in the isolated nonastrocyte cells (tdTomato − APC − ) from IRKO GFAP mice were comparable to the IR loxp group, confirming the specificity of the deletion (Fig 1C). Previous studies have suggested that tanycytes near the third ventricle express GFAP [30]. Therefore, to further verify the purity of astrocytic FACS isolation, we measured gene expression of different markers of neuronal, tanycytic, microglia, and endothelial markers and confirmed the specific isolation of astrocytes via FACS (S3 Fig).…”

Biological roles of glial fibrillary acidic protein as a biomarker in cartilage regenerative medicine

“…However, although vimentin compensated for most cells, no phenotype was observed. Therefore, we indicated the GFAP specific phenotype for the auricular chondrocytes, although these phenotypes of GFAP are not compensated by vimentin (Holmes et al, ). Meanwhile, one of the GFAP phenotypes was multinucleation.…”

Meta-Analysis of the Alzheimer’s Disease Human Brain Transcriptome and Functional Dissection in Mouse Models

“…For example, conditional knockout of the DNA methyltransferase, DNMT1 (M54), in the mouse brain ( Narayanan et al, 2014 ) activates a set of DEGs that significantly overlapped (p adj = 1.4 × 10 −11 ) with a human module, IFGblue, enriched for unfolded protein response and DNA repair pathway genes. In another example, brain RNA-seq from a Gnasxl -deficient mouse ( Holmes et al, 2016 ) (M156) overlapped with FPbrown, a coexpression module (p adj = 5.4 × 10 −9 ) enriched for genes involved in oxidative phosphorylation and mitochondrial translation. Interestingly, Gnas , which encodes a G-protein alpha stimulatory subunit, is a complex, imprinted genomic locus implicated in hypothalamic control of energy balance.…”

“…Other manipulations generate signatures similar to AD models, including PTCH1 knockout (M183) ( Ung et al, 2018 ), nmf205 (M182) ( Ishimura et al, 2016 ), and neuroserpin mutant (M205) ( Guadagno et al, 2017 ). Modules poorly enriched for cell type signatures (asterisk, right) show selected overlaps with FTD-ALS models (M28, M43; Ibrahim et al, 2013 , and Lagier-Tourenne et al, 2013 , respectively) and other, unexpected genetic manipulations (M158, M111, M54, and M156; Vied et al, 2016 , Maze et al, 2015 , Narayanan et al, 2014 , and Holmes et al, 2016 , respectively). See Tables S5 and S6 for comprehensive results, including sample sizes for all comparisons.…”