KIT is required for hepatic function during mouse post-natal development

<p>Abstract</p> <p>Background</p> <p>The <it>Kit </it>gene encodes a receptor tyrosine kinase involved in various biological processes including melanogenesis, hematopoiesis and gametogenesis in mice and human. A large number of <it>Kit </it>mutants has been described so far showing the pleiotropic phenotypes associated with partial loss-of-function of the gene. Hypomorphic mutations can induce a light coat color phenotype while complete lack of KIT function interferes with embryogenesis. Interestingly several intermediate hypomorphic mutations induced in addition growth retardation and post-natal mortality.</p> <p>Results</p> <p>In this report we investigated the post-natal role of <it>Kit </it>by using a panel of chemically-induced hypomorphic mutations recently isolated in the mouse. We found that, in addition to the classical phenotypes, mutations of <it>Kit </it>induced juvenile steatosis, associated with the downregulation of the three genes, <it>VldlR</it>, <it>Lpin1 </it>and <it>Lpl</it>, controlling lipid metabolism in the post-natal liver. Hence, <it>Kit </it>loss-of-functions mimicked the inactivation of genes controlling the hepatic metabolism of triglycerides, the major source of energy from maternal milk, leading to growth and viability defects during neonatal development.</p> <p>Conclusion</p> <p>This is a first report involving KIT in the control of lipid metabolism in neonates and opening new perspectives for understanding juvenile steatosis. Moreover, it reinforces the role of Kit during development of the liver and underscores the caution that should be exerted in using KIT inhibitors during anti-cancer treatment.</p

Proteomic Shifts in Embryonic Stem Cells with Gene Dose Modifications Suggest the Presence of Balancer Proteins in Protein Regulatory Networks

Large numbers of protein expression changes are usually observed in mouse models for neurodegenerative diseases, even when only a single gene was mutated in each case. To study the effect of gene dose alterations on the cellular proteome, we carried out a proteomic investigation on murine embryonic stem cells that either overexpressed individual genes or displayed aneuploidy over a genomic region encompassing 14 genes. The number of variant proteins detected per cell line ranged between 70 and 110, and did not correlate with the number of modified genes. In cell lines with single gene mutations, up and down-regulated proteins were always in balance in comparison to parental cell lines regarding number as well as concentration of differentially expressed proteins. In contrast, dose alteration of 14 genes resulted in an unequal number of up and down-regulated proteins, though the balance was kept at the level of protein concentration. We propose that the observed protein changes might partially be explained by a proteomic network response. Hence, we hypothesize the existence of a class of “balancer” proteins within the proteomic network, defined as proteins that buffer or cushion a system, and thus oppose multiple system disturbances. Through database queries and resilience analysis of the protein interaction network, we found that potential balancer proteins are of high cellular abundance, possess a low number of direct interaction partners, and show great allelic variation. Moreover, balancer proteins contribute more heavily to the network entropy, and thus are of high importance in terms of system resilience. We propose that the “elasticity” of the proteomic regulatory network mediated by balancer proteins may compensate for changes that occur under diseased conditions

A new mouse model for the trisomy of the Abcg1–U2af1 region reveals the complexity of the combinatorial genetic code of down syndrome

Mental retardation in Down syndrome (DS), the most frequent trisomy in humans, varies from moderate to severe. Several studies both in human and based on mouse models identified some regions of human chromosome 21 (Hsa21) as linked to cognitive deficits. However, other intervals such as the telomeric region of Hsa21 may contribute to the DS phenotype but their role has not yet been investigated in detail. Here we show that the trisomy of the 12 genes, found in the 0.59 Mb (Abcg1–U2af1) Hsa21 sub-telomeric region, in mice (Ts1Yah) produced defects in novel object recognition, open-field and Y-maze tests, similar to other DS models, but induces an improvement of the hippocampal-dependent spatial memory in the Morris water maze along with enhanced and longer lasting long-term potentiation in vivo in the hippocampus. Overall, we demonstrate the contribution of the Abcg1–U2af1 genetic region to cognitive defect in working and short-term recognition memory in DS models. Increase in copy number of the Abcg1–U2af1 interval leads to an unexpected gain of cognitive function in spatial learning. Expression analysis pinpoints several genes, such as Ndufv3, Wdr4, Pknox1 and Cbs, as candidates whose overexpression in the hippocampus might facilitate learning and memory in Ts1Yah mice. Our work unravels the complexity of combinatorial genetic code modulating different aspect of mental retardation in DS patients. It establishes definitely the contribution of the Abcg1–U2af1 orthologous region to the DS etiology and suggests new modulatory pathways for learning and memory

Approches génotypique et phénotypique de modèles murins de pathologies humaines

Par sa physiologie et son développement, le modèle murin constitue une avancée majeure pour l'étude de l'étiologie des pathologies humaines. Au cours de ce travail nous avons utilisé les deux grandes stratégies couramment employées afin d'étudier la fonction des gènes : l'approche de génétique inverse qui fait appel aux technologies d'ingénierie chromosomique pour modifier un ou plusieurs gènes et en observer les conséquences sur le phénotype et celle de la génétique classique basée sur l'observation de nouveaux phénotypes afin d'identifier le gène muté. Dans un premier temps, nous avons utilisé le système de recombinaison Cre/loxP pour générer de nouveaux modèles murins d'aneuploïdies d'une région du chromosome 17, homologue à la partie télomérique du chromosome 21 humain. Parallèlement, nous avons analysé les phénotypes de trois mutants allèliques du gène Kit issus d'un crible de mutagenèse chimique aléatoire par l'éthyl-nitoso-urée (ENU). Ces travaux confirment la complémentarité de ces deux stratégies pour la modélisation de pathologies humaines et pour contribuer à une meilleure compréhension fonctionnelle du génome.ORLEANS-BU Sciences (452342104) / SudocSudocFranceF

Morphometric analysis of muscle cross sections using multicolor immunofluorescence imaging

Morphometric analysis of muscle cross sections using multicolor immunofluorescence imaging . International Conference on Biomedical Engineering (ICBE 2018

Resolution and computational strategy in wideband multiphoton microscopy illustrated with muscle imaging

International audienceMultiphoton microscopy (MPM) is an approach now well established in biomedical sciences, especially thanks to its excitation spectrum in the near infrared range (NIR). The simultaneous imaging of numerous of these substances imposes the use of a wideband excitation spectrum, indispensable in the case of in vivo and in live imaging or for detecting phenomena at video rates. A unique spectral bandwidth, covering the range between 750 and 1000 nm has been recently demonstrated and has made emerging a simplification in MPM: the excitation system is now no longer an lock for generating multiphoton images of numerous fluorophores. But such a solution might be highly sensitive to chromatic distortions and diffraction limit which might result in detrimental effects on image quality and especially on resolution performance. This question is at the core of the current presentation. A point-spread function (PSF) estimation is realized with a standard computational tool. Our experimental strategy has shown two interesting points. First, the resolution is preserved in the lateral plan (xy) regardless of the excitation procedure chosen. Second, a significant deterioration of the resolution is observed in the axial direction (z), with a factor 4 between the best resolution obtained with a standard imaging procedure and the worst one obtained with the wider spectral bandwidth. Starting with this result, the role of a computational solution of image reconstruction is highlighted for reducing the gap observed in axial resolution between standard and wideband excitation solution of MPM. The illustration of the interest of a large spectral bandwidth of excitation is then shown on a mouse muscle sample presenting 3 fluorophores having a spectral bandwidth of excitation spread along 300 nm. This set of experiments illustrates the impact of chromatic distortions and diffraction limit on the deterioration of resolution. As a conclusion, a basic protocol for image reconstruction is used in order to highlight the interesting level of improvement of the visual image quality generated by a standard computational image restoration

Endogenous two- and three-photon fluorescence of a biological substance with a picosecond ultrawide band laser source

International audienc

In vivo knock-down of novel murine myogenic partners identified by a siRNA-based screen in C2C12 myoblasts

In vivo knock-down of novel murine myogenic partners identified by a siRNA-based screen in C2C12 myoblasts. JSFM, Société Française de Myologi