Hippocampal glial alterations are associated with Lamin B1 dysregulation and abnormal nuclear morphology in a rat model of fragile X syndrome

Fragile X syndrome (FXS) is the most common inherited intellectual disability and the leading monogenic cause of autism spectrum disorders (ASD). Although the pathological mechanisms underlying this neurodevelopmental disorder are challenging, recent studies have increasingly highlighted the involvement of glial cells in the pathogenesis of both ASD and FXS. Microglia and astrocytes are critical for brain development and homeostasis; thus, understanding glial dysfunction in both the developing and adult brain in these disorders may reveal novel therapeutic targets beyond the neuro-centric perspective. In this study, we demonstrated that the loss of function of Fmrp leads to phenotypic changes in both microglia and astrocytes within the hippocampus of the recently validated Fmr1- ∆ exon 8 rat model of FXS without a significant induction of pro-inflammatory cytokines. For the first time, we also provide evidence that these non-inflammatory changes in glia are associated with dysmorphic nuclei and a reduced expression of Lamin B1, a key component of the nuclear envelope and an important modulator of brain development and aging, in the hippocampus of young adult Fmr1- ∆ exon 8 rats. Collectively, our findings strengthen existing evidence of the glial contribution to FXS and identify Lamin B1 loss and nuclear abnormalities as potential early markers of hippocampal pathology, providing a novel potential molecular target which should be furtherly considered. • Hippocampal microglia and astrocytes show morphological alterations in young adult Fmr1- ∆ exon 8 rats. • No differences in hippocampal or circulating cytokine expression are observed in Fmr1- ∆ exon 8 rats under unstimulated conditions. • Reduced expression levels of Lamin B1 are detected in the hippocampus of young adult Fmr1- ∆ exon 8 rats, particularly in glial cells, and correlate with defective nuclear morphologies.