Background: Nicotinamide (NAM) is an important antioxidant, which is closely related to female fertility, but its role has not been clearly elucidated. The purpose of the present study was to investigate the effects of NAM on follicular development at different stages and the quality of oocytes.Methods: The concentration of NAM in follicular fluid (FF) of 236 women undergoing in vitro fertilization (IVF) was ascertained by enzyme-linked immunosorbent assay (ELISA), and the correlation between NAM and clinical indexes was analyzed. During the in vitro maturation (IVM) of mice cumulus-oocyte complexes (COCs), different concentrations of NAM were added to check the maturation rate and fertilization rate. The reactive oxygen species (ROS) levels in the oocytes treated with different hydrogen peroxide (H₂O₂) and NAM were assessed. Immunofluorescence staining was performed to measure the proportion of abnormal spindles.Results: The level of NAM in large follicles was significantly higher than that in small follicles. In mature FF, the NAM concentration was positively correlated with the rates of oocyte maturation and fertilization. Five mM NAM treatment during IVM increased maturation rate and fertilization rate in the oxidative stress model, and significantly reduced the increase of ROS levels induced by H₂O₂in mice oocytes.Conclusions: Higher levels of NAM in FF are associated with larger follicle development. The supplement of 5 mM NAM during IVM may improve mice oocyte quality, reducing damage caused by oxidative stress.

Delayed childbearing leads to increased assisted reproductive technology use by women of advanced maternal age (AMA). It is unclear whether fresh or frozen embryo transfer (FET) is the better option. We aimed to assess maternal and neonatal outcomes in patients having their first FET after a freeze-all cycle versus those having their first fresh embryo transfer (ET). We reviewed 720 women of AMA undergoing a first fresh ET (n = 375) or FET (n = 345) between January 2016 and April 2021. No significant difference in the live birth rate was found between FET and fresh ET (19.7% vs. 24.3%, p = 0.141). The clinical pregnancy rate was significantly lower in the FET group than in the fresh ET group (26.4 % (91/345) vs. 33.6% (126/375), p = 0.035), but FET resulted in higher birthweights (3217.16 ± 734.44 vs. 3003.37 ± 635.00, p = 0.037) and was associated with a lower incidence of preterm births (2.6% vs. 5.6%, p = 0.046). The risks of other maternal and neonatal outcomes did not differ significantly between the groups. Among women of AMA, the transfer of frozen embryos did not result in significantly higher rates of live birth than fresh embryos did; however, a freeze-all strategy may not be beneficial for the women of AMA.

Background: Numerous pathogenic variants causing human oocyte maturation arrest have been reported on the primate‐specific TUBB8 gene. The main etiology is the dramatic reduction of tubulin α/β dimer, but still large numbers of variants remain unexplained.Methods: Using microinjection mRNA and genome engineering to reintroduce the conserved pathogenic missense variants into oocytes or in generating TUBB8 variant knock‐in mouse models, we investigated that the human deleterious variants alter microtubule nucleation and spindle assembly during meiosis. Live‐cell imaging and immunofluorescence were utilised to track the dynamic expression of microtubule plus end‐tracking proteins in vivo and analysed microtubule nucleation or spindle assembly in vitro, respectively. Immunoprecipitation‐mass spectrometry and ultramicro‐quantitative proteomics were performed to identify the differential abundance proteins and affected interactome of TUBB8 protein.Results: First, we observed a significant depletion of the EB1 signal upon microinjection of mutated TUBB8 mRNA (including R262Q, M300I, and D417N missense variants), indicating disruption of microtubule nucleation caused by these introduced TUBB8 missense variants. Mechanically, we demonstrated that the in vivo TUBB8‐D417N missense variant diminished the affinity of EB1 and microtubules. It also harmed the interaction between microtubules and CKAP5/TACC3, which are crucial for initiating microtubule nucleation. Attenuated Ran‐GTP pathway was also found in TUBB8‐D417N oocytes, leading to disrupted spindle assembly. Stable microtubule was largely abolished on the spindle of TUBB8‐D417N oocytes, reflected by reduced tubulin acetylation and accumulated HDAC6. More importantly, selective inhibition of HDAC6 by culturing TUBB8‐D417N oocytes with Tubacin or Tubastatin A showed morphologically normal spindle and drastically recovered polar‐body extrusion rate. These rescue results shed light on the strategy to treat meiotic defects in a certain group of TUBB8 mutated patients.Conclusion: Our study provides a comprehensive mechanism elucidating how TUBB8 missense variants cause oocyte maturation arrest and offers new therapeutic avenues for treating female infertility in the clinic.

Genetic screening is an important approach for etiology determination and helps to optimize administration protocols in reproductive centers. After the first pathogenic gene of female infertility was reported in 2016, more and more new pathogenic genes were discovered, and we sought to develop an efficient and cost-effective method for genetic screening in patients. In this study, we designed a target-sequencing panel with 22 female infertility-related genes, namely, TUBB8, PATL2, WEE2, and PANX1 and sequenced 68 primary infertility (PI) and recurrent pregnancy loss (RPL) patients. We sequenced 68 samples reaching an average depth of 1559× and detected 3,134 variants. Among them, 62.2% were synonymous single-nucleotide variants (SNVs) and 36.3% were non-synonymous SNVs. The remaining 1.5% are indels (insertions and deletions) and stop-gains. DNAH11 and TUBB8 are the two genes that mutated most frequently. We also found a novel TUBB8 variant (c.898_900del; p.300_300del), proved its loss-of-function mechanism, and profiled the interactome of the wild-type (WT) and mutant TUBB8 proteins. Overall, this target-sequencing method provides an efficient and cost-effective approach for screening in IVF clinics and will support researchers for the discovery of new pathogenic variants.

Alternative splicing (AS) as one of the important post-transcriptional regulatory mechanisms has been poorly studied during embryogenesis. In this study, we comprehensively collected and analyzed the transcriptome data of early embryos from human and mouse. We found that AS plays an important role in this process and predicted candidate RNA binding protein (RBP) regulators that are associated with reproductive development. The predicted RBPs such as EIF4A3, MAK16, SRSF2, and UTP23 were found to be associated with reproductive disorders. By Smart-seq2 sequencing analysis, we identified 5445 aberrant alternative splicing events in Eif4a3-knockdown embryos. These events were preferentially associated with RNA processing. In conclusion, our work on the landscape and potential function of alternative splicing events will boost further investigation of detailed mechanisms and key factors regulating mammalian early embryo development and promote the inspiration of pharmaceutical approaches for disorders in this crucial biology process.