Sex chromosome evolution and Y degeneration within the Primates lineage – SEXPRIM

Développement méthodologique : enrichissement en chromosomes Y par cytofluorométrie avec mise au point à partir de lymphocytes humains (marquage à l’iodure de propidium des chromosomes en métaphase en fonction de leur taille)
- Séquençage des gènes X-Y par les nouvelles technologies de séquençage
- Recherche des phénomènes de conversion génique Y/Y et X/Y

Not yet major results during these 6 first months, but:
- new sequences from some primates for the several fonctionnal genes on both the X and Y chromosomes
- analyses to detect the genic conversion X/Y and Y/Y during the Primate evolution.

Obtaining new sequences from the Y chromosome in several Primates to better understand the evolutionary mecanisms implied in the Y degeneration

Two communications to the J. Monod Conference (22 to 23 may): «Recent advances on the evolution of sex and genetic systems«

The sex chromosomes have attracted a lot of attention from the biologists due to their very peculiar evolutionary history, their role in sex determination and sexual dimorphism, and their importance in human health and men infertility problems in particular. Most of the data on sex chromosomes come from the human XY. However, the studies on human XY have focused on comparing the fully-sequenced human X and Y among each other or with very distantly related organisms such as monotremes and birds. Only a handful of studies have focused on smaller scales and in primates, only the human and chimp Y have been compared. Several important events have occurred recently in the primate lineage, and we lack a comprehensive analysis of the primate Y. Here we want to conduct such an analysis by sequencing the Y chromosomes using Next-Generation Sequencing (NGS) techniques of 5 additional primates with already available X chromosomes in ENSEMBL. Using these plus the two already available Y from human and chimp, we want to prepare a very large dataset of X-Y homologous regions and study the evolution of the regions from the strata 4 and 5, which are primate-specific. We want to study ongoing gene loss and protein degradation for the first time in mammals and also other aspects of Y degeneration that are poorly known even in mammals such as X-Y chromosomal rearrangements and Y DNA methylation. We want to generate a very large polymorphism dataset using high throughput methods and assess the contribution of the different degenerative processes (Muller’s ratchet, background selection and selective sweep) for the first time in mammalian XY. We also want to study whether gene duplication and gene conversion have evolved for primate Y ampliconic genes to escape degeneration as recently proposed. Finally, we want to relate the patterns of Y degeneration observed in different primates to their life-history traits and effective population size. This proposal, based on a fine-scale comparative molecular approach, includes several labs with complementary experience and expertise (primate evolution, sex chromosomes, genomics and bioinformatics, population genetics, cytogenetics, molecular epigenetics) from Toulouse, Lyon and Paris with help of several technical platforms. We expect major advances in the field of the evolution of sex chromosomes and in the Y degeneration factors .