This research article presents a comprehensive spatial transcriptomic atlas of the complement system within the mouse brain, spanning from embryonic stages to adulthood. Using MERFISH technology, the authors mapped the expression of 51 complement-related genes, discovering that most are produced locally with high cellular and regional diversity. While the classical pathway increases during maturation to facilitate synaptic pruning, the study identifies a previously unknown role for the alternative pathway in early brain development. Specifically, the researchers found that Masp3, an alternative pathway activator, is vital for brain maturation and proper cortical neuron distribution. Their findings demonstrate that a lack of Masp3 leads to spatial memory deficits and significant systemic growth issues. Overall, the study highlights how the brain maintains a unique immune environment by strictly regulating complement activity to prevent inflammatory damage.

References:

• Zhang Y, Watson B, Rattan A, et al. A spatial atlas of the complement system uncovers unique expression patterns in postnatal brain development in mice[J]. Nature Communications, 2025.