TEX43, a Testis-Enriched Microtubule-Associated Gene, Exerts Minimal Impact on Spermatogenesis and Fertility in Mice and Humans

Purpose Testis-specific TEX family genes are critical for spermatogenesis, but TEX43’s function remains uncharacterized. This study aimed to delineate TEX43’s role in spermatogenesis and fertility using murine models and clinical data. Methods Tex43 expression was analyzed via quantitative reverse transcription-polymerase chain reaction (Q-PCR), immunohistochemistry (IHC), and western blotting. A Tex43 knockout (KO) mouse model was generated using CRISPR/Cas9 (targeting exons 1–3). Testicular histology (hematoxylin-eosin [H&E] staining), sperm parameters (morphology via H&E smears, density via hemocytometer, motility via computer-assisted sperm analysis [CASA]), and fertility (in vivo breeding assays, in vitro fertilization [IVF]) were evaluated. Sperm ultrastructure was assessed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Whole-exome sequencing (WES) identified TEX43 variants in 146 infertile men with asthenoteratozoospermia. Structural modeling of WT/mutant TEX43 was performed via SWISS-MODEL. Results Tex43 is testis-enriched: mRNA expression initiated at postnatal day 18 (round spermatid stage) and peaked in elongating spermatids; TEX43 localized to sperm flagellar microtubules. Tex43-KO mice showed modestly reduced sperm density (28.6 ± 3.2 vs. 41.2 ± 2.9×10⁶ sperm/ml in WT; P < 0.01) but normal testicular architecture, sperm motility, and fertility (litter size: KO 6.8 ± 0.7 vs. WT 7.2 ± 0.5 pups/litter; P > 0.05). TEM revealed increased flagellar end piece "9 + 2" microtubule disorganization in KO sperm (~ 30% vs. ~5% in WT; P < 0.01). WES identified 9 infertile men with TEX43 variants; 4 with exonic variants (e.g., p.R37Q) achieved live births via intracytoplasmic sperm injection (ICSI). Structural modeling showed p.R37Q disrupted hydrogen bonds critical for microtubule binding. Conclusions TEX43 is minimal impact on murine spermatogenesis and fertility, likely due to genetic redundancy. Human TEX43 variants may exert subtle reproductive effects, requiring validation in larger cohorts with functional studies.