Regulation of synaptic connectivity by astrocytes is critical for development of the central
nervous system (CNS), yet little is known about how these processes differ between males and
females. The long-term goal is to identify mechanisms involved in astrocyte-mediated synaptic
development in order to inform novel therapies to prevent or correct disrupted synaptic circuitry
in neurodevelopmental diseases in patients of both sexes. The primary objective of this
application is to investigate basic fundamental differences in astrocyte-neuron synaptogenic
signaling between males and females. The central hypothesis is that thrombospondin (TSP)-
induced synaptogenesis is required for proper cortical development of males but less essential
for females, establishing sexual dimorphism in astrocyte-mediated synaptic development. The
central hypothesis will be tested in three specific aims: 1) Evaluate sex differences in astrocyte
synaptogenic signaling; 2) Elucidate the molecular mechanism underlying sex differences in
TSP-induced synaptogenesis; and 3) Investigate sex-dependent regulation of dendritic spine
and synapse development by the TSP receptor, a2d-1. In the first aim, astrocyte-conditioned
media (containing secreted factors) from either male or female rats will be evaluated for their
synaptogenic efficacy on neurons derived from either sex. The impact of astrocytic estrogen
receptors as well as neuron-secreted factors on expression and secretion of various astrocytic
synaptogenic factors will also be determined. For the second aim, estrogen signaling in TSP-
treated cortical neuron cultures will be manipulated to delineate the contributions of brain-
derived neurotrophic factor (BDNF), Rac1, and presynaptic muting on astrocyte synaptogenic
signaling. In the third aim, male and female in vivo and ex vivo models will be assessed for
dendritic spine synaptic development in a transgenic mouse line lacking the TSP synaptogenic
receptor, a2d-1, in the cortex. This research approach is innovative because it will rigorously
explore the novel possibility that astrocyte-mediated synaptic development is differentially
regulated between males and females and identify estrogen as a prominent regulatory element
in this process. The research proposed in this application is significant because it will provide
the basis for increasingly robust experimental designs intended to elucidate novel mechanisms
of synaptogenesis and astrocyte/neuronal crosstalk in both sexes. Investigating sex differences
in astrocyte signaling will expand our understanding of synaptic network formation in both males
and females in order to generate innovative strategies to identify, prevent, or correct aberrant
synaptic connectivity in developmental CNS disorders such as autism and schizophrenia.