Dernière mise à jour : vendredi 11 mars 2016, par
[Effets de l’environnement précoce sur le vieillissement et la valeur sélective individuelle chez le martinet alpin (Apus melba)]
General background :
What factors determine life expectancy of organisms still remains a major unresolved question. An important candidate for the determination of life expectancy is change in the length of telomeres at the end of chromosomes. Functioning telomeres are crucial to genome integrity and, in turn, to tissue and organ functioning. Telomeres shorten with cell replication and short telomeres induce cell senescence. Because most of telomere shortening occurs during early growth, one hypothesis is that telomere dynamics produce the frequently observed link between poor early growth condition and short life expectancy. Accordingly, artificial growth reduction in the early life of captive zebra finches (ZF) accelerates the loss of telomere length, a proxy of ageing rates, and telomere length at the end of the growth period has been shown to be predictive of individual lifespan both in captivity (ZF) and in the wild (Alpine swift). Therefore, using telomere length measurements in a population of wild birds where individuals have been followed over their entire lifetime will offer a unique opportunity to investigate how telomere length actually relates to life expectancy, and the importance of early growth conditions in shaping telomere dynamics and ageing rates.
This question will be addressed using a wild population of Alpine swifts breeding in Bienne and Solothurn (Switzerland). Those two colonies have been followed since 1999, and the whole individual life trajectory of this long-lived bird (growth and reproductive patterns, lifespan and blood samples) are available for 446 individuals. Because the alpine swift forages exclusively on flying insects, chicks endure periods of prolong fasting during spells of bad weather conditions. We will use this variance to study how environmental and growth conditions affected telomere erosion in early life and at adult stage, and how this is related to individual life trajectory.
The Alpine swift is a long-lived bird that feeds its offspring exclusively with aerial insects. Hence, spells of cold and rains have profound effect on development and later survival in this bird species.
Telomere length will be measured at the IPHC-DEPE, using qPCR amplification of telomeric sequences of genomic DNA extracted from red blood cells. This methodology has already been applied on alpine swift samples by our lab, and we already improved the method by developing a multiplex methodology on this species (measuring both the telomere and the control genes in the same run, improving the accuracy of the method). In addition, telomerase activity using qPCR will be determine in fresh samples (obtained during the field seasons 2017-2019) to assess its impact in individual fitness related traits. In fact, telomerase is an important variable for telomere dynamics (i.e. by maintaining telomere length, but also via direct effect on individual ageing per se).
The long-term data acquired since 1999 on the whole population enable us to implement the analyses with the pedigree of the population, i.e. the degree of genetic relatedness among individuals. Using specific statistical approaches (Animal model), we will be able to distinguish the genetic versus the environmental influences on the telomere dynamics and life-history trajectories of individuals.
Finally, besides telomeres, we envisage to add the measurement of other ageing related variables, such as glycated hemoglobin proportion (already tested on ZF and swift samples), mitochondrial ROS production (using oximetry available in the DEPE, on mitochondria extracted from red blood cells) as well as histone methylation rates in relation to the control of telomere length. Such measurements, if planed, will be done on fresh samples collected during the summer field seasons 2017-2018.
An experimental approach of telomere length modulation by, for example, administration of the telomerase activator to growing chicks or adults, will be realized in captive ZF housed in the DEPE. A previous experiment using TA-65 has already been conducted with success in 2013, showing that telomerase could be successfully activated and telomere length modified accordingly. Such an approach will be used to test the causality of some of the significant relationships between telomere length and fitness traits that will come out from the long-term data analysis.
Research program and supervision :
the PhD student will benefit of a free and total access to the long-term data file collected since 1999 and on the blood samples (or DNA bank already extracted) stored in the partner lab or in the DEPE.
Supervision of the PhD will be shared (co-direction) by F. Criscuolo (CR1-CNRS, IPHC-DEPE) and P. Bize (Senior Lecturer, University of Aberdeen).
Both researchers work together since 2006 and have already published several papers together. Telomere analyses on swift have already been performed by the DEPE molecular laboratory ran by S Zahn, IE2-Unistra. S Zahn is specialized in qPCR methodology and is responsible of telomere measurements in the Ageing Group of F Criscuolo. She will be in charge of supervising the lab work of the PhD student and helping him/her to acquire the methodological skills. The field work will be supervised by P Bize, and realized with him and F Criscuolo during the summer. An additional Master student from Lausanne University is participating each year to the capture, ringing and measurements of birds. Laboratory (2500 euros per year) and travelling (1000 euros per year) costs (plus a labtop, 800 euros) of the student will be shared by both supervisors, based on CNRS and Aberdeen University funding.