Signalling and morphogenesis

Our team is interested in renal development. We aim to understand the mechanisms underlying nephron formation. 

The nephron is the functional and structural unit of the kidney, it is responsible for the filtration and elimination of wastes, and blood homeostasis, processes commonly affected in renal pathologies.

We study the mechanisms of nephrogenesis using the Xenopus tadpole’s pronephros as a model. The pronephros constitutes a single enormous nephron on each side of the embryo. Unlike mammal nephrogenesis that relies on pre-existing renal structures, the Xenopus pronephros develops directly from pluripotent cells of the dorso-lateral mesoderm. Thereby, the model offers the possibility to study the mechanisms controlling renal lineage specification.

Despite their differences during development, the nephron organization is remarkably conserved between Xenopus and mammals, especially the regionalization of the nephron tubule into functional domains controlling ions and nutrient reabsorption, and urine formation.

Our research is focused on three main aspects of pronephros development:

  • The commitment of a population of mesodermal cells towards a renal fate. What are the signals and genes responsible for renal precursor specification within the pronephric field?
  • The formation of the epithelial tube that will give rise to the nephron tubule. How are cell shape, cell re-organization and cell polarity orchestrated during this process?
  • The differentiation of the tubule, its regionalization and its morphogenesis. How are certain transcription factors regulating these processes?


  • The first aspect mainly concerns retinoic acid (RA) signals, pax8 transcription factor, and pax8 target genes controlling renal fate of pronephric field cells. We have demonstrated the crucial role of RA in this process (Cartry et al, 06, Le Bouffant et al. 12; Futel et al., 15), as well as that of pax8 (Buisson et al, 15). We are now trying to understand the mechanisms controlling pax8 expression and the role of pax8 downstream target genes during renal specification.
  • The second aspect, regarding the formation of the epithelial tube that will give rise to the tubule, is focused on the identification of cytoskeleton, cell adhesion and extracellular matrix components participating in this process (Bello et al., 08). We also study how upstream pax8-dependent renal specification mechanisms can regulate the key players of morphogenesis.
  • The third aspect concerns tubule differentiation. We are studying the role of pou3f family genes and hnf1b (Heliot et al, 13) during regionalization and morphogenesis of the proximal/intermediate region of the tubule. In human kidney, this region of the nephron possesses the unique capacity to promote tubular epithelium survival and nephron repair upon acute kidney injury, as frequently initiated by ischemia reperfusion injury in transplants.


Using loss of function approaches, we have studied the roles of pax8 and pax2 respectively during pronephros development. Although both gene products may have redundant functions, we have been able to show their requirement during distinct steps of pronephric development. Pax8 is essential during the early steps of pronephros development. Its absence causes a total loss of the tubule. Pax2 is required at later stages, for the differentiation of the tubule primordium. We have been able to establish that pax8 controls hnf1b expression in the pronephric field. Pax8 is also involved in the control of renal precursor proliferation. It may exert this function through the Wnt/ß-catenin pathway, by regulating dvl1 and sfrp3 gene expression (Buisson et al., 2015).

Intracellular calcium signaling is very active in the pronephric field (Leclerc et al., 2008), although its role was poorly understood. Through an active collaboration with C. Leclerc and M. Moreau (CBD Toulouse), we have shown that the TRPP2 channel, which is encoded by the pkd2 gene, is playing a central role in the generation of these calcium transients. The absence of TRPP2 causes the inhibition of pax8 expression, without affecting other pronephric field gene expression (lhx1, osr1, 2). We could further establish that disruption of retinoic acid signaling results in a massive reduction of calcium transients and TRPP2 trafficking to the plasma membrane of pronephric field cells (Futel et al., 2015).