MyoJ

MyoJ (PF3D7_1229800) is a basal complex protein of Plasmodium that is recruited during schizogony/segmentation and occupies a distinct subcompartment of the contractile basal complex machinery (PMID:37400439, PMID:38829893). In P. falciparum, MyoJ was identified as a co-immunoprecipitating partner of the basal complex protein PfCINCH and validated by immunofluorescence against PfMORN1 to reside at the basal complex (PMID:37400439); ultrastructure expansion microscopy further resolves it to a novel 'posterior cup' subcompartment distinct from the main PfCINCH-marked ring, with MyoJ recruited midway through segmentation after PfSLACR and removed unevenly as segmentation concludes (PMID:38829893). Its role is not required for asexual blood-stage replication: deletion of the P. berghei ortholog did not impair basal complex constriction or schizogony, and the protein instead accumulates in the oocyst residual body during sporogony (PMID:31283102). Beyond this basal-complex membership, localization dynamics, and dispensability, no molecular activity or mechanistic function for MyoJ has been characterized in the available corpus.

1. 2019 Medium

   Whether MyoJ is required for the division machinery of the parasite was unknown; genetic deletion established that it is dispensable for basal complex constriction and asexual replication.

   Evidence Gene knockout with phenotypic analysis of basal complex constriction and schizogony, plus GFP tagging, in P. berghei

   PMID:31283102

   Open questions at the time

   • Does not address whether MyoJ has a non-essential or redundant contribution to basal complex function
   • GFP protein was undetectable, so localization during blood-stage replication was not established
   • No mechanistic activity assigned
2. 2019 Low

   The fate of MyoJ across the life cycle was unknown; imaging showed it accumulates in the oocyst residual body, indicating it is discarded at the end of endomitotic division during sporogony.

   Evidence Live-cell fluorescence imaging of GFP-tagged MyoJ in P. berghei

   PMID:31283102

   Open questions at the time

   • Single-method localization observation without functional follow-up
   • Functional significance of residual-body accumulation unknown
   • Does not establish a molecular role during sporogony
3. 2023 Medium

   Whether MyoJ physically associates with the basal complex was unknown; Co-IP/MS with PfCINCH plus IFA validation established it as a basal complex protein in P. falciparum.

   Evidence Co-immunoprecipitation mass spectrometry with PfCINCH and IFA of an endogenous smV5-tagged line co-stained with PfMORN1 in P. falciparum 3D7

   PMID:37400439

   Open questions at the time

   • Direct binding versus indirect complex membership not resolved
   • Molecular activity of MyoJ within the complex unknown
   • No structural or stoichiometric data
4. 2024 Medium

   The spatial and temporal organization of MyoJ within the basal complex was unknown; super-resolution imaging placed it in a distinct 'posterior cup' subcompartment recruited midway through segmentation.

   Evidence Ultrastructure expansion microscopy and live-cell imaging of endogenously tagged proteins in P. falciparum

   PMID:38829893

   Open questions at the time

   • Functional consequence of posterior-cup localization unknown
   • Mechanism of temporal recruitment after PfSLACR unresolved
   • Basis of uneven removal at segmentation end not defined

• The molecular activity of MyoJ and its specific contribution to basal complex function during segmentation remain undefined.
• No enzymatic or motor activity demonstrated for MyoJ
• No P. falciparum loss-of-function phenotype reported
• Interactions beyond PfCINCH co-IP not mapped