DYNLT2B/TCTEX1D2: evidence and transfer notes

The human reference Q8WW35 is DYNLT2B, historically TCTEX1D2. It is a non-motor light chain of cytoplasmic dynein-2; DYNLT1 and DYNLT3 are distinct partner light chains. The 2025 mouse paper explicitly identifies Tctex1d2 as Dynlt2b. PMID:39827215(https://pubmed.ncbi.nlm.nih.gov/39827215/)

Human mechanism

Biochemical composition studies establish TCTEX1D2 as a dynein-2 light chain. PMID:25205765(https://pubmed.ncbi.nlm.nih.gov/25205765/)

we identify TCTEX1D2 as a unique dynein-2 light chain

Human knockout experiments establish retrograde ciliary trafficking defects, complementing patient and Chlamydomonas evidence. The light chain supports the motor; it is not itself an ATPase or a membrane transporter. PMID:29742051(https://pubmed.ncbi.nlm.nih.gov/29742051/), PMID:26044572(https://pubmed.ncbi.nlm.nih.gov/26044572/)

The human localization study distinguishes endogenous ciliary-base/MTOC signal from tagged-protein overexpression in the axoneme. This distinction is retained in the annotation review. PMID:25830415(https://pubmed.ncbi.nlm.nih.gov/25830415/)

Structural evidence

The 2024 study determined the isolated DYNLT1–DYNLT2B heterodimer structure. PMID:38454149(https://pubmed.ncbi.nlm.nih.gov/38454149/), DOI:10.1038/s44318-024-00060-1, PDB:8RGI

The RCSB entity record maps the second polymer to Q8WW35 and includes its complete terminal sequence. Human UniProt records a beta-strand at residues 128–140 from this structure. The paired horse alignment lacks human residues 129–142, placing the deletion in an observed structured region rather than a presumed dispensable tail. This is evidence for a consequential model uncertainty, not a folding assay on the horse protein.

Mouse sperm evidence

The peer-reviewed 2025 mouse study reports sperm flagellar dysplasia and disrupted axonemal structure in Tctex1d2-null males, with preserved motile cilia in the examined tissues. It also reports testis interactions with cytoplasmic dynein-2 and inner-arm dynein proteins. This supports a tissue-dependent axonemal role in mouse and does not establish human infertility or equine localization by itself. PMID:39827215(https://pubmed.ncbi.nlm.nih.gov/39827215/), DOI:10.1038/s41598-024-83424-1

The Falcon report lists this work as a 2024 preprint; the source check above uses the published 2025 paper. Its cautious description of human retrograde-IFT evidence is supplemented by the direct 2018 knockout study, rather than adopted as a bare verdict.

Unresolved source-specific annotations

The NAS male-germ-cell-nucleus annotation cites PMID:36973253. The cached full text examines DYNLRB1/DYNLRB2 and does not establish the DYNLT2B-specific localization in the material inspected. It remains UNDECIDED; no experimental annotation is removed merely because the paper foregrounds another gene. Dynein axonemal particle residence is also distinct from ciliary-base, axoneme or dynein-complex localization and remains unresolved.