Characterization of Astrocyte Density in the Pitt–Hopkins Syndrome Mouse Model of Autism Spectrum Disorder

Background/Objectives: Transcription factor 4 (TCF4) is a proneural basic helix–loop–helix transcription factor that plays a critical role in brain development and is associated with a variety of psychiatric disorders, including autism spectrum disorder (ASD), major depressive disorder, and schizophrenia. Autosomal dominant mutations in TCF4 result in a profound neurodevelopmental disorder called Pitt–Hopkins Syndrome (PTHS). Germline TCF4 loss-of-function (LOF) studies using human and mouse models have identified dysregulation in neural cell proliferation, genesis, and specification, which leads to disruption in neuronal, astroglial, and oligodendroglial lineages. In this study, we focused on the role of TCF4 in the genesis of the astrocyte lineage, specifically in the context of modeling PTHS. Methods: We investigated the expression of astrocyte marker genes in primary astrocyte cultures and whole-brain lysates, as well as assessed pan- and subclass-specific astrocyte markers, using immunohistochemical (IHC) analysis in a heterozygous mouse model of PTHS. Lastly, we tracked ventrally derived astrocytes using an Nkx2.1 reporter mouse to investigate misallocation of ventrally derived astrocytes into the dorsal cortex, a phenotype previously observed when both Tcf4 alleles were conditionally deleted in the Nkx2.1 lineage. Results: We show that germline heterozygous mutations in Tcf4 had no effect on the expression of astrocyte markers via qPCR or astrocyte cell density with IHC analysis. Germline heterozygous Tcf4 LOF also did not result in misallocation of ventrally derived astrocytes into the dorsal cortex. Conclusions: These data indicate that germline heterozygous TCF4 LOF, which models PTHS, does not appear to significantly affect the astrocyte lineage at the cell population level.