Sex differences in neuronal differentiation of human stem cells

Sammanfattning: Sexual dimorphism has been long noted in human neurobiology, apparent most notably in sex-biased distribution of multiple neurological disorders or diseases, from autism spectrum disorder to Parkinson's disease. With the advances in molecular biology, genetics and epigenetics have come into focus as key players in sexually dimorphic neural development; and yet, many studies in the field of neuroscience overlook the importance of sex for the human brain. For this project, human embryonic and neural stem cells were chosen for three main reasons. Firstly, they provide an easily obtainable, scalable and physiologically native model for the early stages of development. Secondly, neural stem cells populations are retained within the adult human brain, and are implicated to play a role in cognition and mental illness, and as such are of interest in themselves. Thirdly, stem cell lines are widely used in research, including clinical trials of transplantation treatments, and for this reason should be meticulously examined and characterized. Here, the morphology, behaviour, and expression of selected genes in four stem cell lines, two of female and two of male origin, was examined in side-by-side comparisons prior to and during neuronal differentiation using a variety of methods including light microscopy, time-lapse two-photon microscopy, quantitative real-time PCR and immunocytochemistry. The obtained results have shown previously uncharacterised differences between those cell lines, such as a higher rate of proliferation but a slower rate of neuronal differentiation in male cell cultures compared to female cells cultivated in the same conditions, and a sex-biased expression of several markers of neuronal maturation at late stages of differentiation, as well as diverse patterns of expression of X- and Y-linked genes involved in stem cell proliferation and neural development.