Biology subjects

Olivier Pourquie

Publications and source records attributed to Olivier Pourquie.

3 recordsLinked to original sources

bioRxiv2016

TAF10 is required for the integrity of TFIID and SAGA complexes but is initially dispensable for somitogenesis in the mouse embryo

Cell fate and patterning during development are controlled by gene expression. Pre-initiation complex (PIC) formation at promoters is crucial to recruit the transcriptional machinery. The PIC has mainly been studied in vitro, and little is known about its composition and function during development. TAF10 is a subunit of TFIID and of the transcriptional co-activator SAGA. Here we characterized TFIID and SAGA's composition during mouse development. Our data indicate that TAF10 is required for TFIID and SAGA assembly. To analyse TAF10-dependent gene regulation during development, we conditionally deleted Taf10 in the mesoderm. Our results provide evidence for a time window during which Taf10 loss in the presomitic mesoderm (PSM) does not prevent cyclic gene transcription or PSM patterning while lateral plate differentiation is profoundly altered. During this period, global steady state mRNA levels are not significantly affected in the PSM although the expression of a subset of specific genes is dysregulated. Together, our data demonstrate a differential sensibility of mesodermal tissues to the lack of TAF10. This supports a differential requirement for TAF10 by the general transcriptional machinery during different developmental processes.

Developmental Biology↗

bioRxiv2016

PAPC couples the Segmentation Clock to somite morphogenesis by regulating N-cadherin dependent adhesion

Vertebrate segmentation is characterized by the periodic formation of epithelial somites from the mesenchymal presomitic mesoderm (PSM). How the rhythmic signaling pulse delivered by the Segmentation Clock is translated into the periodic morphogenesis of somites remains poorly understood. Here, we focused on the role of Paraxial protocadherin (PAPC/Pcdh8) in this process. We show that in chicken and mouse embryos, PAPC expression is tightly regulated by the Clock and Wavefront system in the posterior PSM. We observed that PAPC exhibits a striking complementary pattern to N-Cadherin (CDH2), marking the interface of the future somite boundary in the anterior PSM. Gain and loss of function of PAPC in chicken embryos disrupt somite segmentation by altering the CDH2-dependent epithelialization of PSM cells. Our data suggest that clathrin-mediated endocytosis is increased in PAPC expressing cells, subsequently affecting CDH2 internalization in the anterior compartment of the future somite. This in turn generates a differential adhesion interface, allowing formation of the acellular fissure that defines the somite boundary. Thus periodic expression of PAPC downstream of the Segmentation Clock triggers rhythmic endocytosis of CDH2, allowing for segmental de-adhesion and individualization of somites.

Developmental Biology↗

bioRxiv2016

Multiscale quantification of tissue behavior during amniote embryo axis elongation

Embryonic axis extension is a complex multi-tissue morphogenetic process responsible for the formation of the posterior part of the amniote body. Cells located in the caudal part of the embryo divide and rearrange to participate in the elongation of the different embryonic tissues (e.g. neural tube, axial and paraxial mesoderm, lateral plate, ectoderm, endoderm). We previously identified the paraxial mesoderm as a crucial player of axis elongation, but how movements and growth are coordinated between the different posterior tissues to drive morphogenesis remain largely unknown. Here we use the quail embryo as a model system to quantify cell behavior and movements in the various tissues of the elongating embryo. We first quantify the tissue-specific contribution to axis elongation by using 3D volumetric techniques, then quantify tissue-specific parameters such as cell density and proliferation at different embryonic stages. To be able to study cell behavior at a multi-tissue scale we used high-resolution 4D imaging of transgenic quail embryos expressing constitutively expressed fluorescent proteins. We developed specific tracking and image analysis techniques to analyze cell motion and compute tissue deformations in 4D. This analysis reveals extensive sliding between tissues during axis extension. Further quantification of \"tissue tectonics\" showed patterns of rotations, contractions and expansions, which are coherent with the multi-tissue behavior observed previously. Our results confirm the central role of the PSM in axis extension; we propose that the PSM specific cell proliferation and migration programs control the coordination of elongation between tissues during axis extension.

Developmental Biology↗