The effect of HSP70 overexpression on the cerebral cortex development

Abstract

Heat shock proteins (HSPs) make up a large family of molecular chaperones, recognized for their role in protein maturation, refolding, and degradation. HSP70 was shown to promote cell survival during several pathological processes in the brain, such as stroke, neurodegenerative diseases, epilepsy, and trauma [1]. In addition, HSPs serve to promote the proper embryonic and postnatal development of many organ systems, such as the central nervous system [2]. Heat shock proteins demonstrate specific expression patterns throughout the development of the nervous system, notably during crucial embryonic and postnatal moments [1]. During embryonic development, neural and glial progenitors must survive within a hypoxic microenvironment while performing energetically demanding actions, such as cell migration and neurite outgrowth. HSPs can activate or inhibit development pathways in the nervous system that modulate cell differentiation, neurite outgrowth, cell migration, or angiogenesis [1]. Indeed, recent studies demonstrated that HSP70 directly regulates the development of the nervous system by modulating signaling cascades involved in cell growth and migration [3]. Additionally, research demonstrated [4] that introducing HSP70 from an external source significantly augments the populations of proliferating cells and differentiated neuroblasts within the mouse hippocampus. Nevertheless, some researchers [1] contend that overexpression of HSPs may negatively impact cell survival. Therefore, the precise role of these chaperones remains largely unexplored. In our study, we used in utero electroporation to introduce plasmids that controlled HSP70 overexpression into neuron progenitors of mouse embryos on the 14th day of gestation. Additionally, plasmid DNA encoding GFP was used to facilitate subsequent visualization of transformed cells. Brain samples were collected on the 18th day of gestation for immunohistochemical analysis of the sections. Confocal microscopy was used to compare the characteristics of neuronal migration in both control and HSP70 overexpression conditions. Cells that received plasmids inducing HSP70 were discovered to migrate at a lower pace in comparison to the control. Additionally, it is hypothesized that the induction of HSP70 expression could lead to neuronal malformations and impact the development of neurites. In the future, the study of cytoarchitectonics in the cortex will continue, examining the identification of electroporated cells in individual neuron populations using Satb2 and Ctip2 markers. Additionally, the differentiation of these cells will be assessed by counting those that have not exited the mitotic cycle, and the hypothesis of apoptosis induction in cells electroporated with HSP70 will be tested.