Authors:

NaLaya Lee

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About Paper:

Sarcocystis neurona, a protozoan responsible for a debilitating neurological disease called equine protozoal myeloencephalitis, undergoes asexual replication in the central nervous system of the horse. This replication involves two developmental stages: extracellular merozoites and intracellular schizonts. Interestingly, these stages in S. neurona lack a specialized apical secretory organelle called rhoptries, but several rhoptry proteins (ROPs), including SnROP21, were identified in the transcriptome and proteome of S. neurona. In related protozoans, rhoptry proteins typically localize to and are discharged by rhoptries to participate in host-parasite interactions. This prompted questions about rhoptry protein localization and their functional roles in S. neurona in the absence of rhoptry organelles. In this study, we have used a transgenic S. neurona line expressing a C-terminal hemagglutinin (HA)-tagged SnROP21 (SnROP21-HA) to perform immunolocalization assays. Bovine fibroblast monolayers on cover glasses were infected with S. neurona merozoites that transformed into schizonts upon invasion. Cover glasses with intracellular schizonts at four different timepoints over a 72-h period of development were collected. Merozoites on poly-L-Lysine-coated glass slides and intracellular schizonts were fixed and processed by probing with anti-HA antibodies to localize SnROP21. In extracellular merozoites, SnROP21 was localized predominantly to the apical pole. In the schizonts, SnROP21 showed temporal expression, with it being undetectable at the 48 h timepoint but showing granular cytoplasmic distribution at other timepoints. This dynamic expression of SnROP21 suggests a unique role that might be temporally regulated. Further studies on SnROP21 will enhance our understanding of its role in S. neurona biology and host-parasite interaction. Keywords: Horses; Equine Protozoal Myeloencephalitis; Sarcocystic Neurona; Rhoptries; Immunofluorescence

Source:

Purdue University / 2025

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Co-authors:

NaLaya Lee