# TSC-associated microglial hyperactivity: enhanced calcium signaling, metabolism, and phagocytosis

## TL;DR

This study shows that microglia in Tuberous Sclerosis Complex (TSC) display abnormal calcium signaling, metabolism, and phagocytosis, contributing to the disease's neurological symptoms.

## Contribution

The study reveals novel microglial dysfunction in TSC, including altered calcium signaling and metabolism, previously underexplored in this condition.

## Key findings

- TSC microglia show impaired store-operated calcium entry and increased mitochondrial calcium uptake.
- TSC microglia exhibit elevated mitochondrial respiratory activity and increased phagocytic activity.
- Transcriptomic analysis shows upregulation of genes related to lipid metabolism and immune activation in TSC brain tissue.

## Abstract

Tuberous sclerosis complex (TSC) is a multisystem genetic disorder with prominent neurological manifestations, most notably epilepsy, and is frequently accompanied by a wide range of neuropsychiatric comorbidities. Hyperactivation of the mechanistic target of rapamycin (mTOR) pathway plays a central role in TSC pathology, disrupting both general brain development and specific molecular processes such as metabolism. While much attention has focused on neurons and astrocytes in these TSC-related alterations, the contribution of microglia remains relatively underexplored. In this study, we first analysed the transcriptomic profiles from resected TSC brain tissue and identified evidence of calcium (Ca2+) dysregulation in TSC microglia. In order to investigate the functional consequences, we then examined induced pluripotent stem cell (iPSC) derived microglia-like (iMGL) cells from TSC patients. Our findings reveal that these iMGL cells displayed markedly altered Ca2⁺ signalling, characterized by impaired store-operated calcium entry (SOCE) and an increase in mitochondrial Ca2⁺ uptake. These changes are accompanied by elevated mitochondrial respiratory activity, suggesting a shift in metabolic state. In addition, TSC iMGL cells displayed increased phagocytic activity and an altered inflammatory responsiveness, consistent with a dysregulated microglial activation state. Supporting these functional alterations in iMGL cells, transcriptomic analysis of TSC brain tissue revealed upregulation of several genes associated with lipid metabolism, phagocytosis, and innate immune activation, with partial overlap with stage 2 disease-associated microglia (DAM)-like programs. Together these findings suggest that microglial dysfunction may represent a relevant component of TSC pathophysiology.

The online version contains supplementary material available at 10.1007/s00401-026-02986-8.