Somatic cell | EPFL Graph Search

In cellular biology, a somatic cell (), or vegetal cell, is any biological cell forming the body of a multicellular organism other than a gamete, germ cell, gametocyte or undifferentiated stem cell. Such cells compose the body of an organism and divide through the process of binary fission and mitotic division. In contrast, gametes are cells that fuse during sexual reproduction, germ cells are cells that give rise to gametes, and stem cells are cells that can divide through mitosis and differentiate into diverse specialized cell types. For example, in mammals, somatic cells make up all the internal organs, skin, bones, blood and connective tissue, while mammalian germ cells give rise to spermatozoa and ova which fuse during fertilization to produce a cell called a zygote, which divides and differentiates into the cells of an embryo. There are approximately 220 types of somatic cell in the human body. Theoretically, these cells are not germ cells (the sourc

Analysis of centriole elimination during C. elegans oogenesis

Pierre Gönczy, Graham Knott, Tamara Mikeladze-Dvali, Petr Strnad, Lukas von Tobel

Centrosomes are the principal microtubule organizing centers (MTOCs) of animal cells and comprise a pair of centrioles surrounded by pericentriolar material (PCM). Centriole number must be carefully regulated, notably to ensure bipolar spindle formation and thus faithful chromosome segregation. In the germ line of most metazoan species, centrioles are maintained during spermatogenesis, but eliminated during oogenesis. Such differential behavior ensures that the appropriate number of centrioles is present in the newly fertilized zygote. Despite being a fundamental feature of sexual reproduction in metazoans, the mechanisms governing centriole elimination during oogenesis are poorly understood. Here, we investigate this question in C. elegans. Using antibodies directed against centriolar components and serial-section electron microscopy, we establish that centrioles are eliminated during the diplotene stage of the meiotic cell cycle. Moreover, we show that centriole elimination is delayed upon depletion of the helicase CGH-1. We also find that somatic cells make a minor contribution to this process, and demonstrate that the germ cell karyotype is important for timely centriole elimination. These findings set the stage for a mechanistic dissection of centriole elimination in a metazoan organism.

2012

A single-cell-based identification and characterisation of Aregs, an inhibitory subpopulation of adipose stem and precursor cells

Magda Zachara

Adipose tissue is an essential element in energy conservation mechanisms. Its unique plasticity is driven by the ability of adipocytes to accumulate and liberate lipids as a function of the energetic status of the organism. Given the recent rise in the global incidence of obesity, there is great interest in understanding the mechanisms behind disturbed energy balance. However, the heterogeneity of adipose tissue and of the somatic stem cells giving rise to mature adipocytes, makes it extremely challenging to characterise the cellular and molecular identity of fat depots. Single-cell RNA sequencing has recently enabled ground-breaking insights into the composition of complex cell populations. Our single cell-based dissection of adipogenic precursors revealed the existence of distinct cell sub-populations within the murine subcutaneous fat depot. We demonstrated that one of these populations, characterised by a high expression of F3 gene (encoding CD142), showed a completely non-adipogenic phenotype. Moreover, it revealed to be regulatory towards other adipose stem and precursor cells by supressing their ability to form adipocytes in a paracrine manner. These adipogenic regulatory cells, which we termed Aregs, proved to maintain their inhibitory properties in vivo and were shown phenotypically conserved in humans. We next established the robustness of Aregs as a novel cell sub-type in the context of various isolation strategies, the strength of the adipogenic cue and sex-based differences. Interestingly, we observed that Aregs isolated from the bourgeoning subcutaneous depots of new-born mice had high adipogenic propensity, suggesting that the appearance of classical phenotypical and functional properties of Aregs is development-dependent. In the light of the considerable implications of Aregs in adipose tissue composition and plasticity and, subsequently metabolic health, it is critical to understand the mechanism of their inhibitory nature. Integration of transcriptomic and proteomic datasets allowed us to identify a comprehensive set of highly specific candidates, which we validated in the context of Aregsâ identity and function. Our findings revealed a few potentially involved molecular actors. These include secreted factors CD142, GDF10 and MGP, which proved to be directly capable of inhibiting adipogenesis of Areg-depleted adipose stem and precursor cells, and transcription factors PKNOX2 and MEOX2, whose inactivation in Aregs compromised their ability to inhibit adipogenesis of co-cultured differentiating pre-adipocytes. Collectively, these molecules point out to a potential functional relationship of Aregs with vasculature as well as evoke a plausible association of Aregsâ phenotype to visceral-like non-adipogenic properties. We are now integrating these findings and completing them by investigating the transcriptional regulation and signalling pathways underlying the elusive mechanism of Aregsâ activity.

EPFL2020

A single-cell-based identification and characterisation of Aregs, an inhibitory subpopulation of adipose stem and precursor cells

Magda Zachara

EPFL2020