ALV9

ALV9/IMC7 (TG_260540) is an alveolin domain-containing component of the Toxoplasma gondii inner membrane complex cytoskeleton whose defining feature is its temporal and stage-specific behavior during the parasite life cycle (PMID:29062899). Unlike IMC proteins that are incorporated into nascent daughter buds during endodyogeny, IMC7 is recruited to the mother's cytoskeleton in the G1 phase, outside of cytokinesis, marking it as a distinct temporal class of IMC protein (PMID:29062899). Its expression is stage-restricted across development: present in dividing asexual tachyzoites, lost in early microgametocytes, retained in macrogametocytes until late development, and absent from sporozoites (PMID:29062899). Functionally, IMC7 is required for the structural integrity and stress resistance of extracellular tachyzoites, as knockout parasites lose structural integrity outside the host cell (PMID:29062899). Beyond this localization and loss-of-function phenotype, no molecular partners, biochemical activity, or mechanism of recruitment have been characterized in the available corpus.

1. 2017 Medium

   Establishing when and where IMC7 is deposited addressed whether all IMC cytoskeletal proteins share a single assembly program; IMC7 was found to be recruited to the mother cytoskeleton in G1, outside cytokinesis, defining a temporal class distinct from daughter-bud IMC proteins.

   Evidence Cell-cycle stage-resolved immunofluorescence/imaging of tachyzoites

   PMID:29062899

   Open questions at the time

   • No molecular mechanism for G1-specific recruitment identified
   • Partners mediating incorporation into the mother cytoskeleton unknown
   • No structural or biochemical characterization of the alveolin domain interaction
2. 2017 Medium

   Mapping IMC7 across the life cycle addressed whether its role is constitutive or stage-specialized, revealing stage-restricted dynamics: retained in macrogametocytes but lost in early microgametocytes and absent from sporozoites.

   Evidence Spatiotemporal localization analysis across life cycle stages by live imaging/immunofluorescence

   PMID:29062899

   Open questions at the time

   • Functional significance of stage-specific retention/loss not tested
   • Regulation driving stage-specific expression unknown
   • No functional data in gametocyte or sporozoite stages
3. 2017 Medium

   Whether IMC7 contributes materially to parasite fitness was addressed by knockout, which showed loss of structural integrity of extracellular tachyzoites, establishing IMC7 as critical for stress resistance outside the host cell.

   Evidence Genetic knockout with structural/stress-resistance phenotypic readout in tachyzoites

   PMID:29062899

   Open questions at the time

   • Mechanism linking IMC7 to structural integrity not resolved
   • Whether the defect reflects cytoskeletal instability versus another pathway untested
   • Single lab, single study; no complementation/rescue reported

• The molecular partners, recruitment machinery, and biochemical basis by which IMC7 confers structural integrity remain unknown.
• No interacting proteins identified
• No structural model of the alveolin domain in this protein
• Mechanism of stage-specific expression and G1 recruitment uncharacterized