Laboratoire de Physiomedecine moléculaire (LP2M) - CNRS-UMR 7370,
Université de Nice-Sophia antipolis, Faculté de Médecine, 28 Av Valombrose,
Tour Pasteur06108 Nice, France.
We are looking for excellent applicants for a PhD position for three years, starting between
September and December 2015. The fellowship is granted by the ICST Labex andbe awarded
for one of the 3 thesis topics described below. Applicants must imperatively choose one of the
three topics. They have to send a detailed CV (with ranks and marks for the Master's degree
or equivalent) to Jacques.Barhanin@unice.fr before July 15 at 12pm, accompanied by a letter
explaining their motivation for a PhD and for the chosen subject. Following a pre-selection
based on the sent documents, an external panel of scientists will conduct an audition of the
selected candidates. The date of the audition will be between July 20 and 29th in NICE at the
laboratory.
PROJECT 1
Name of the thesis director (with HDR) :Saïd BENDAHHOU.
Title: Role of the Kir2.1 potassium channels in excitable and non-excitable tissues.
PROJECT 2
Name of the thesis director (with HDR) : Laurent COUNILLON.
Title: The Na+/H+ exchangers expressed in the intracellular compartments. From their
biochemical function to their implication in Autism spectrum disorders.
PROJECT 3
Name of the thesis director (with HDR) : Christophe DURANTON/ Isabelle RUBERA.
Title: Roles and functions of the newly identified Cl- channels LRRC8 familyin
kidney physiology and differentiation of immune cells.
PROJECT 1
PhD Student Request Form
Host team:
Name of the thesis director (with HDR) :…………………..Saïd BENDAHHOU
Starting date : September 1st 2015
Thesis project
Role of the Kir2.1 potassium channels in excitable and non-excitable tissues.
Andersen’s syndrome (AS) is complex disorder unique with patient phenotypes
mixing periodic paralyses, cardiac arrhythmia, bone malformation, and cognitive
abnormalities. We have made progress understanding how mutations in the KCNJ2,
the only gene associated with AS, can lead to electrical dysfunctions in both skeletal
and cardiac muscles. The involvement of Kir2.1 channels in AS has emphasized the
physiological importance of sarcolemmal inward rectifiers in regulating cellular
excitability. However, our understanding of the fundamental molecular and
biophysical mechanisms responsible for Kir2.1 dysfunction and an explanation for
dominant negative mutant channel behavior in this disorder are incomplete.
Moreover, the contribution of Kir2.1 to muscle excitability and bone development
remains to be elucidated. The actual project will focus on determining the role of the
Kir2.1 channel in excitability and bone morphogenesis in vitro and in vivo, using
biopsies from AS patients and animal models. We have used AS muscle biopsies to
understand the role of the potassium channels in both skeletal muscle excitability and
bone morphogenesis. If muscle biopsies may be appropriate in addressing skeletal
muscle issues, this may have some limitations in other tissues. Reprogramming of
human somatic cells into induced pluripotent stem cells (iPSCs) and differentiating
them into the 3 germ layers is a new powerful technology that offer an attractive tool
to model human developmental pathways1. Furthermore, disease-specific iPSCs
allow an unprecedented experimental plateform for basic research as well as
highthroughput screening 2. This may be particularly relevant for developmental
disorders in which the effects on cells during the early life are not accessible. We will
take advantage of the availability of three AS muscle biopsies (along with biopsies
from controls) to generate human AS-specific iPSCs. These human AS-specific
iPSCs will be differentiated in vitro into skeletal muscle, cardiac muscle, or
osteoblasts according to known protocols and mimickingthe corresponding
developmental pathways.First, a thorough functional characterization will be carried
out on the undifferentiated as well as differentiated cells using conventional patch
clamp techniques. A combination of transcriptomics and proteomic analyses,
immunohistochemistry, microscopy imaging, and 2-photon Ca2+ imaging will be used
to determine the role of the Kir2.1 potassium channel in cell excitability as well as
during the different key steps of bone morphogenesis. In parallel, mouse embryos will
be injected with either WT or AS mutant constructs to generate mouse model
allowing the identification of the critical steps involving Kir2.1 channel during
embryonic stages and especially during palate formation. In mouse development, the
prospective palatal mesenchymal cells begin to be specified in the maxillary
processes at embryonic day 11.5 (E11.5) 3. The developing palate shelves first grow
down vertically along the two sides of the tongue between E12.5 and E13.5. From
E14.5, however, the two palatal shelves elevate above the level of the dorsal tongue.
It has been recently shown that kcnj2 is expressed at lower levels during early
developmental stages (at day E10.5) in fetal heart4. We will monitor the transcript
and protein expression level in mouse tissues of the kcnj2 as well as that of
osteogenic genes. Using a combination of immunohistochemistry, microarray, and
biochemical techniques, we will identify the molecular determinants that have been
affected by the lack of the Ik1 current expression, and may likely be involved in kir2.1
signaling during osteogenesis. This combination of both in vitro (human cells) and in
vivo (on mouse) studies will allow to obtain converging data on the role of Kir2.1 in
muscle excitability and during mammalian development. This project fits well in the
TASK 2 of the Labex scientific themes (molecular and cellular physiology of ion
channels). The scheduled experiments will involve the inward rectifier Kir2.1
potassium channels in human ex vivo models that are carried out within many teams
of the Labex. Making human induced pluripotent stem cells (iPSCs) from diseased
tissues, which is part of the thesis project, may turn out to be very useful for other
Labex teams. The generation of a conditional kcnj2 knockout mouse (funding
requested to Fondation Maladies rares) may be beneficial also to other teams of the
ICST labex.
K, et al. (2007) Cell 131: 861--‐72.
IH, et al. (2008) Cell 134: 877--‐86.
3 Murray JC, and Schutte BC (2004) J Clin Invest 113: 1676--‐8.
4 Liu A, et al. (2010) CellPhysiolBiochem 26: 413--‐20.
1 Takahashi
2 Park
CNRS-UMR 7370 -Laboratoire de Physiomedecine moléculaire, Université de
Nice-Sophia antipolis Faculté de Médecine, 28 Av Valombrose, Tour Pasteur
06108 Nice, France. e-mail: bendahhou@unice.fr
PROJECT 2
PhD Student Request Form
Host team:
Name of the thesis director (with HDR) :…………………..Laurent COUNILLON
Starting date : September 1st 2015
Thesis project
The Na+/H+ exchangers expressed in the intracellular compartments. From
their biochemical function to their implication in Autism spectrum disorders.
Na+/H+ Exchangers (NHEs) are expressed in all biological systems. In vertebrates,
three isoforms of NHEs are mostly restricted to intracellular compartments. Their
sequences are highly conserved and their mRNAs are detected in a number of
organs in mammals, including the central nervous system. In 2006, a deletion of the
gene encoding NHE-7 was found in mental retardation patients (5-6) and in 2008 two
studies have linked defects NHE-6 and NHE-9 to genetic syndromes associating
cognitive disorders autism or attention deficit type, epilepsy and cerebellar
degeneration (7). Despite this importance, little is known about the role of these
intracellular exchangers in the regulation of the pH of intracellular compartments.
Indeed, the study of their biochemical and pharmacological characteristics, essential
to understanding their function, has encountered the fact that they are sequestered
within the cells and are very poorly accessible for measurements. We managed to
solve this problem by selecting cell lines capable of withstanding acute cytosolic
acidification, through expression NHE-6 or 7 at the plasma membrane. We now use
an arsenal of ion transport measurement techniques developed in our team (8-9) to
study the kinetics, ion selectivity, pharmacology and regulation of these carriers in a
quasi-exhaustive manner. In parallel we are studying their localization in organs and
particularly in the brain. We work with clinical groups whose goal is to identify
mutations in patients with mental disorders like autism, mental retardation, or
attention deficit. The PhD student will use the tools available in our laboratory
(somatic genetics, fast kinetics, video microscopy and imaging etc) to study the
NHE6 and NHE9 exchangers for all that concerns their ion selectivity, regulation,
pharmacological profile, interactome and their cerebral and intracellular localization.
The gained information will be used to measure their impact on vesicular pH, on
trafficking and ultimately to understand their brain functionand role in
neurodevelopment. The PhD student will also be involved in the genotyping of
cohorts of patients and study of the impact of the mutations that will be eventually be
found. This will bring together their function and patient phenotypes.
CNRS-UMR 7370 -Laboratoire de Physiomedecine moléculaire, Université de
Nice-Sophia antipolis Faculté de Médecine, 28 Av Valombrose, Tour Pasteur
06108 Nice, France. e-mail: counillo@unice.fr
PROJECT 3
PhD Student Request Form
Host team:
Name of the thesis director (with HDR) :Christophe DURANTON/ Isabelle RUBERA
Starting date : September 1st 2015
Thesis project
Roles and functions of the newly-identified channels family LRRC8 in kidney
physiology and differentiation of immune cells.
A Chloride permeability sensitive to volume variation has been described in most of
the eukaryote cells. This ubiquitous Cl- conductance plays a major role in regulatory
volume decrease (RVD) 1 and apoptotic volume decrease (AVD) processes 2. Since
more than 30 years the molecular identity of this conductance has remained elusive.
In 2014, 2 independent studies 3, 4 have demonstrated the involvement of a new
family of membrane proteins (LRRC8A/swell) in the generation of a volume sensitive
Cl- conductance opening new perspectives of research in this field.
The aim of this original project is to establish the roles and the functions of this new
family of channels in 1/ cell division, 2/ in apoptotic progression and 3/ in different
cellular processes (epithelial mesenchymal transition and the behavior of immune
cells). Extensively, animal model will be developed to study the importance of the
LRCC8 family in kidney physiology and/or differentiation of immune cells. This project
will focus on this new family of proteins to identified new processes and innovative
targets to prevent kidney fibrosis and renalfailure5.
We are looking for strongly motivated candidates with interest in cell volume
regulation and ions transport. The candidate will be formed to various techniques
including electrophysiology (patch-clamp), fluorescence video-microscopy and/or flow
cytometry analysis. Basic techniques of biochemistry and cell biology will be also
developed during the PhD.
1.
Barriere, H. et al. Am J PhysiolRenalPhysiol 284, F796-811 (2003).
L'Hoste, S. et al. Free RadicBiol Med 46, 1017-31 (2009).
3. Voss, F. K. et al. Science 344, 634-8 (2014).
4. Qiu, Z. et al. Cell 157, 447-58 (2014).
5. Liu, Y. J Am SocNephrol 15, 1-12 (2004).
2.
CNRS-UMR 7370 -Laboratoire de Physiomedecine moléculaire, Université de
Nice-Sophia antipolis Faculté de Médecine, 28 Av Valombrose, Tour Pasteur
06108 Nice, France. e-mail: duranton@unice.fr or rubera@unice.fr