Jacques J. Tremblay

Professor Jacques J. Tremblay is a researcher in the Reproduction, mother and youth health program of the CHU de Québec-Université Laval Research Center, and Full Professor in the department of obstetrics, gynecology, and reproduction of the Faculty of Medicine at Université Laval. His research focuses on the study of various facets of Leydig cells, cells of the endocrine system, with applications for differences of sexual development, hormone-dependent diseases, cell differentiation, as well as the regulation of gene expression.

Prof. Tremblay’s research program is at the jonction of the fields of developmental biology, endocrinology, and cellular and molecular biology. His team studies the molecular mechanisms of male sex differentiation. Acquisition of the male phenotype typically follows three sequential steps: formation of the bipotential gonad, male sex determination (testis differentiation), and male sexual differentiation (driven by testicular hormones). Human mutations in key male determining genes give rise to a group of atypical developmental trajectories known as differences of sex development (DSDs). Prof. Tremblay’s team is studying new genes that could explain certain cases of DSD in humans. In addition, Prof. Tremblay is interested in the differentiation and function of Leydig cells, cells within the testis that produce the steroid hormone testosterone. Inadequate levels of steroid hormones are implicated in several human pathologies including various cancers, PCOS, endometriosis, autoimmune diseases and inflammation. In addition to their importance for male reproductive health, adequate testosterone levels are also essential for men’s global health. Understanding how this system normally functions, by studying Leydig cells, will provide essential information that will ultimately allow us to better diagnose and treat these pathologies.

Although various hormones and signaling molecules have been implicated in male sexual differentiation and in Leydig cell differentiation and function, the transcription factors downstream of these pathways remain poorly understood. So far, his team has identified several transcription factors, some never reported in the gonad or in Leydig cells, that are essential regulators of cell differentiation in other tissues. Some are present exclusively in the male gonad or at specific times in Leydig cells, while others mark stem Leydig cells. A better understanding of the differentiation of stem Leydig cells residing in the adult testis could enable the development of innovative treatments for men suffering from hypogonadism. Prof. Tremblay’s work on hormone-induced signaling pathways in Leydig cells revealed the involvement of two kinases that have antagonistic roles; CAMKI stimulates while AMPK is a molecular brake that quickly stops the production of steroid hormones, which has many clinical implications. Prof. Tremblay’s work involves classical molecular and cellular biology approaches, as well as gene editing, animal models, microscopy, proteomics, genomics and bioinformatics