| Evidence type | Key findings (with quantitative stats when available) | Experimental approach | Developmental stage/tissue | Interpretation for functional annotation | Primary source (author year, journal, DOI URL) |
|---|---|---|---|---|---|
| Expression/localization | `nud-1::GFP` showed diffuse expression in early embryos; sustained expression in amphid and phasmid sensory neurons and nerve ring; additional transient signal in gonadal primordium and diffuse intestinal expression in adults. Figure 3 documents embryo, larval, and adult expression patterns (pqac-00000008, pqac-00000015, pqac-00000025). | Transgenic `nud-1::GFP` reporter microscopy (pqac-00000008, pqac-00000012, pqac-00000015). | Early embryos; larval/adult sensory neurons; gonadal primordium; intestine (pqac-00000008, pqac-00000015, pqac-00000025). | Supports a broadly used cytoplasmic/neuronal developmental factor rather than a tissue-restricted enzyme; embryonic and neuronal expression fits roles in cell division, nuclear positioning, and nervous-system function (pqac-00000009, pqac-00000025). | Dawe et al. 2001, *Development Genes and Evolution*, https://doi.org/10.1007/s004270100176 |
| Embryo nuclear positioning | `nud-1(RNAi)` embryos showed defective pronuclear migration/rotation: pronuclei moved inward but failed to rotate onto the anterior-posterior axis; nuclear envelope breakdown occurred on the dorsal-ventral axis; after first division, two-cell nuclei were centrally located. In later embryos, pronuclei conjoined at variable positions instead of the normal ~70% egg length (pqac-00000010, pqac-00000011, pqac-00000024, pqac-00000025). | dsRNA injection RNAi followed by digital time-lapse video microscopy of early embryos (pqac-00000011, pqac-00000024). | One-cell and two-cell embryos during first mitosis (pqac-00000010, pqac-00000024). | Strongly supports a primary role in dynein-related nuclear positioning/pronuclear-centrosome orientation during early embryonic division, not in general spindle elongation initiation (pqac-00000009, pqac-00000010, pqac-00000024). | Dawe et al. 2001, *Development Genes and Evolution*, https://doi.org/10.1007/s004270100176 |
| Cytokinesis/midzone MT | In `nud-1` RNAi embryos, spindle elongation and pronuclear fusion occurred, but cleavage furrows stalled or regressed, producing multinucleated one-cell embryos. Midzone microtubules were absent in 26% (10/39) of one-cell embryos and weak/poorly defined in 74% (29/39); among embryos with weak midzone MTs, 15/29 showed chromatin bridges. Older embryos formed multipolar spindles and accumulated extra DNA, indicating continued cell cycling without successful cytokinesis (pqac-00000013, pqac-00000026, pqac-00000027). | RNAi feeding; time-lapse Nomarski/live imaging; anti-tubulin/DAPI staining (pqac-00000013, pqac-00000026, pqac-00000030). | One-cell embryos and older embryos during/after first cytokinesis (pqac-00000013, pqac-00000026). | Indicates that NUD-1 is required for late cytokinesis, especially stabilization of the cleavage furrow and organization of midzone microtubules; function is consistent with a microtubule-associated dynein-pathway regulator (pqac-00000000, pqac-00000013, pqac-00000026). | Aumais et al. 2003, *Journal of Cell Science*, https://doi.org/10.1242/jcs.00412 |
| Organismal phenotypes | RNAi caused high-penetrance developmental defects: 94% of injected mothers laid mutant eggs and 73% produced only dead embryos; embryos usually arrested between comma and one-fold stages. Among F1 escapers, >50% showed everted vulva, >75% were uncoordinated, all were sterile, and cuticle/hypodermal defects were observed (pqac-00000024, pqac-00000025). | dsRNA injection RNAi with phenotype scoring across progeny (pqac-00000012, pqac-00000024, pqac-00000025). | Embryos; surviving larval/adult escapers; vulva, hypodermis, locomotor system, germ line (pqac-00000008, pqac-00000025). | These pleiotropic phenotypes are consistent with an essential cellular factor for embryogenesis and postembryonic tissue morphogenesis, likely through conserved cytoskeletal/nuclear-positioning functions rather than a narrowly specialized pathway (pqac-00000009, pqac-00000025). | Dawe et al. 2001, *Development Genes and Evolution*, https://doi.org/10.1007/s004270100176 |
| Functional conservation/complementation | `nud-1` was identified as the C. elegans `nudC` ortholog on cosmid F53A2; sequence comparison showed 47% identity/67% similarity to *A. nidulans* NUDC. Full-length `nud-1`, and especially its C-terminal 173 aa, complemented the *A. nidulans nudC3* mutant, restoring hyphal growth and nuclear migration (pqac-00000009, pqac-00000012). A later review notes that C. elegans NudC homologs can complement fungal `nudC3`, supporting deep functional conservation (pqac-00000003, pqac-00000006). | Sequence comparison; heterologous expression complementation in fungal mutant; DAPI-based nuclear migration assessment (pqac-00000012). | Cross-species assay using worm gene in fungal nuclear migration system (pqac-00000012). | Provides direct evidence that `nud-1` belongs to the conserved NudC family and supports annotation as a nuclear migration/cell division factor rather than an enzyme or transporter (pqac-00000009, pqac-00000012). | Dawe et al. 2001, *Development Genes and Evolution*, https://doi.org/10.1007/s004270100176; summarized in Vassileva et al. 2023, *Plants*, https://doi.org/10.3390/plants13010119 |
| Biochemical/chaperone inference | Family-level evidence shows NudC proteins are dimeric/coiled-coil proteins with a conserved CS domain related to p23 and HSP20/sHSP proteins and can function as Hsp70/Hsp90 co-chaperones. For C. elegans specifically, NUD-1 is described as a microtubule-associated protein with in vitro chaperone activity, preventing heat-induced aggregation of citrate synthase and luciferase (pqac-00000004, pqac-00000006, pqac-00000016, pqac-00000017, pqac-00000018, pqac-00000021). Recent 2024 primary work on the paralogous family member NudCL2 shows Hsp90-dependent stabilization of RCC2 at the midbody during cytokinesis, reinforcing a conserved co-chaperone model for NudC-family proteins in cell division (pqac-00000019). | In vitro chaperone assays for NUD-1 (reviewed); family/domain analyses; recent mammalian primary study of NudCL2/Hsp90/RCC2 (pqac-00000006, pqac-00000018, pqac-00000019, pqac-00000021). | Protein/family level; inferred for worm embryonic microtubule-associated functions (pqac-00000004, pqac-00000006). | Best current mechanistic model is that worm NUD-1 acts as a conserved microtubule-associated dynein/LIS-1 pathway regulator with chaperone or co-chaperone properties that help maintain client proteins required for nuclear positioning and cytokinesis (pqac-00000004, pqac-00000016, pqac-00000019). | Vassileva et al. 2023, *Plants*, https://doi.org/10.3390/plants13010119; Lechuga et al. 2024, *Cells*, https://doi.org/10.3390/cells13050370; Xu et al. 2024, *Protein & Cell*, https://doi.org/10.1093/procel/pwae025 |


*Table: This table compiles the main experimental and inference-based annotations for C. elegans nud-1/F53A2.4, separating direct worm evidence from family-level mechanistic interpretation. It is useful for functional annotation because it links phenotypes, localization, and conserved NudC-family biology to a coherent gene-function model.*