The Amt2 Gene is Key for Cryptococcus neoformans Transmigration Across The Blood-Brain Barrier and Closely Linked to Its Capsule Formation

The cryptococcal Amt family of ammonium transporters have been identified from our previous studies as one of the most highly upregulated proteins during transmigration in an in vitro blood-brain barrier (BBB) model, however, the role of this gene family has never been reported. Therefore, this study aimed to investigate the role of the Amt2 gene in the transmigration of C. neoformans across the BBB, examine its association with other common virulence factors, and assess its relevance to morphological changes in C. neoformans. The results showed that the C. neoformans mutant strain lacking the Amt2 gene (amt2{Delta}) exhibited a significantly reduced ability to transmigrate across the BBB in an in vitro model. Our findings suggest that C. neoformans primarily utilizes a transcellular mechanism for invasion, as indicated by the FITC-dextran permeability assays. Additionally, the size of polysaccharide capsule was significantly smaller in the mutant strain compared to the wild-type. In conclusion, our study proposed that the Amt2 gene plays a crucial role in both the transmigration process and capsule production in C. neoformans, without affecting morphological changes. Our study provides a foundation for future research into the underlying mechanisms of the Amt2 gene in C. neoformans pathogenesis. Author summaryCryptococcus neoformans transmigrates the blood-brain barrier through various mechanisms, with transcellular migration being the major route leading to cryptococcal meningitis. In this study, we identified the Amt2 gene, a member of the Amt family of ammonium transporters, as playing a crucial role in the funguss transmigration process. Our findings indicate that the Amt2 gene promotes capsule production and facilitates the transmigration of C. neoformans, all while not causing damage to human endothelial cells.