KATNAL1

KATNAL1 is a katanin p60-related microtubule-severing ATPase that remodels the microtubule cytoskeleton in specialized cell types to control morphogenesis and cell motility (PMID:22654668, PMID:30448058). In the testis it is expressed in Sertoli cells, where its ATPase activity drives the microtubule dynamics required to retain and ultimately release developing spermatids; a point mutation in its conserved ATPase domain disrupts Sertoli cell microtubules, causing premature spermatid exfoliation and male infertility (PMID:22654668). KATNAL1 acts cooperatively with its paralog KATNA1 throughout spermatogenesis to regulate the meiotic spindle, cytokinesis and midbody abscission, Golgi organization, and acrosome and manchette formation, with KATNAL1 contributing specific roles in sperm flagellum development, manchette regulation, and sperm–epithelial disengagement; its testis interactome includes cytoskeletal and vesicle trafficking proteins (PMID:37882691). In the nervous system KATNAL1 is the dominant neuronal katanin and exhibits greater severing activity and intracellular stability than KATNA1, properties conferred by its amino-terminal half, and it restrains neuronal process elongation while supporting neuronal migration, motile cilia of ependymal cells, and associated behaviors (PMID:28373692, PMID:30448058).

1. 2012 High

   Established KATNAL1 as a functional microtubule-severing protein whose ATPase activity is required in Sertoli cells for spermatid retention, linking its enzymatic function to a defined reproductive phenotype.

   Evidence ENU point mutation in the ATPase domain in a mouse genetic model with histology and immunolocalization of the seminiferous epithelium

   PMID:22654668

   Open questions at the time

   • Did not directly demonstrate severing activity in vitro for the wild-type or mutant protein
   • Did not identify the binding partners mediating microtubule remodeling in Sertoli cells
2. 2017 Medium

   Extended KATNAL1 function beyond the testis, showing it is required for neuronal migration and morphology, motile ciliary function, and normal behavior, implicating it in brain development.

   Evidence Loss-of-function mouse allele with brain morphology, neuronal migration, ciliary, and behavioral assays

   PMID:28373692

   Open questions at the time

   • Single lab; molecular mechanism linking severing to migration and cilia not resolved
   • Behavioral deficits not mechanistically connected to specific cellular defects
3. 2017 Low

   Provided a structural rationale for ATP engagement by the ATPase domain, supporting the enzymatic model.

   Evidence Homology modeling, molecular dynamics simulation, and molecular docking (computational only)

   PMID:28093975

   Open questions at the time

   • Computational only with no experimental validation of ATP binding
   • No experimental structure of KATNAL1
4. 2018 Medium

   Distinguished KATNAL1 from its paralog KATNA1 by showing higher severing activity and greater stability, mapping both properties to the N-terminal half and defining KATNAL1 as the dominant neuronal severing enzyme that restrains process elongation.

   Evidence Cycloheximide chase, domain-swap chimeras, cell-based severing assays, and siRNA knockdown with process elongation readout in Neuro2a cells

   PMID:30448058

   Open questions at the time

   • Activity and stability assayed in cultured cells, not with purified protein
   • Structural basis within the N-terminal half not pinpointed
5. 2023 High

   Resolved the division of labor between KATNAL1 and KATNA1 across spermatogenesis and identified candidate physical partners, establishing cooperative and KATNAL1-specific roles in spindle, cytokinesis, organelle, and flagellar morphogenesis.

   Evidence Single and double knockout mice with comparative phenotyping plus mass spectrometry testis interactome

   PMID:37882691

   Open questions at the time

   • Interactome partners not validated as direct or functionally required
   • Which severing events are KATNAL1- versus KATNA1-dependent at the molecular level not fully separated
6. 2024 Medium

   Linked KATNAL1 to a regulatory and disease context by showing miR-548az-5p suppression of KATNAL1 disorganizes microtubules and promotes senescence in amniotic epithelial cells.

   Evidence miRNA microarray, target prediction, miR-548az-5p overexpression in hAECs with microtubule, senescence, and proliferation assays

   PMID:39638877

   Open questions at the time

   • No direct mutagenesis or rescue of KATNAL1 to confirm causality
   • Single lab; effects on microtubules inferred from miRNA overexpression rather than direct KATNAL1 manipulation

• How KATNAL1 severing activity is spatially and temporally regulated, and the identity of the direct partners that recruit it to specific microtubule populations, remains unresolved.
• No validated direct physical partner with defined functional role
• No experimental structure of the active severing complex
• Mechanism connecting severing to migration, ciliary, and behavioral phenotypes not established