Biallelic variant in cyclin B3 is associated with failure of maternal meiosis II and recurrent digynic triploidy

Cyclin B3 plays pleiotropic roles in female reproductive organogenesis and early embryogenesis in the silkworm, Bombyx mori

BACKGROUND

The reproductive system plays a crucial role in insect survival, reproduction and species specificity. Understanding the molecular mechanisms underlying reproductive organogenesis contributes to improving the efficiency of sterile insect technique marked by an eco-friendly pest management strategy. Lepidoptera is one of the largest orders of insects, most of which are major pests in agriculture and forestry. Our study aimed to screen the genes responsible for reproductive organogenesis and unravel the mechanism underlying female reproductive organ defects.

RESULTS

Morphological investigation of female reproductive organs showed a defective connection between oviductus geminus and oviductus communis on the second day of pupa (P2) in Speckled mutant silkworm. RNA_Seq identified a total of 18 049 transcripts that were expressed in the P2 female internal reproductive organs without ovary in Spc/+ compared to +Spc /+Spc . Differential expression analysis identified 312 up-regulated genes and 221 down-regulated genes in Spc/+. KEGG analysis identified 44 significantly enriched pathways. The results of qRT-PCR performed on 33 genes significantly matched the outcomes of the RNA_Seq. Dysfunction of Cyclin B3 resulted in a defective connection of the oviductus communis with the ovariole, dysfunction of oogenesis, and a petite body. Moreover, homozygous recessive lethality of Cyclin B3/Cyclin B3 occurred during early embryogenesis.

CONCLUSION

Our results suggest that Cyclin B3 is a pleiotropic functional gene that regulates early embryogenesis, oogenesis, development, and female reproductive organogenesis. These results showed that Cyclin B3 has significant effects on lepidopteran mortality, growth, and reproductive physiology, which might be considered a novel and potentially eco-friendly target for lepidopteran pest management. © 2023 Society of Chemical Industry.

Mutations in CCNB3 affect its location thus causing a multiplicity of phenotypes in human oocytes maturation by aberrant CDK1 activity and APC/C activity at different stages

BACKGROUND

Oocyte maturation arrest results in female infertility and the genetic etiology of this phenotype remains largely unknown. Previous studies have proven that cyclins play a significant role in the cell cycle both in meiosis and mitosis. Cyclin B3 (CCNB3) is one of the members of the cyclin family and its function in human oocyte maturation is poorly understood.

METHODS

118 infertile patients were recruited and WES was performed for 68 independent females that experienced oocyte maturation arrest. Four mutations in CCNB3 were found and effects of these mutations were validated by Sanger sequencing and in vitro functional analyses.

RESULTS

We found these mutations altered the location of cyclin B3 which affected the function of cyclin dependent kinase 1 (CDK1) and led to mouse oocyte arrested at germinal vesicle (GV) stage. And then, low CDK1 activity influenced the degradation of cadherin 1 (CDH1) and the accumulation of cell division cycle 20 (CDC20) which are two types of anaphase-promoting complex/cyclosome (APC/C) activators and act in different stages of the cell cycle. Finally, APC/C activity was downregulated due to insufficient CDC20 level and resulted in oocyte metaphase I (MI) arrest. Moreover, we also found that the addition of PP1 inhibitor Okadic acid and CDK1 inhibitor Roscovitine at corresponding stages during oocyte in vitro maturation (IVM) significantly improved the maturation rates in CCNB3 mutant cRNAs injected oocytes. The above experiments were performed in mouse oocytes.

CONCLUSION

Here, we report five independent patients in which mutations in CCNB3 may be the cause of oocyte maturation arrest. Our findings shed lights on the critical role of CCNB3 in human oocyte maturation.

Understanding recurrent pregnancy loss: recent advances on its etiology, clinical diagnosis, and management

Recurrent pregnancy loss (RPL) has become an important reproductive health issue worldwide. RPL affects about 2%-3% of reproductive-aged women, and makes serious threats to women's physical and mental health. However, the etiology of approximately 50% of RPL cases remains unknown (unexplained RPL), which poses a big challenge for clinical management of these patients. RPL has been widely regarded as a complex disease where its etiology has been attributed to numerous factors. Heretofore, various risk factors for RPL have been identified, such as maternal ages, genetic factors, anatomical structural abnormalities, endocrine dysfunction, prethrombotic state, immunological factors, and infection. More importantly, development and applications of next generation sequencing technology have significantly expanded opportunities to discover chromosomal aberrations and single gene variants responsible for RPL, which provides new insight into its pathogenic mechanisms. Furthermore, based upon patients' diagnostic evaluation and etiologic diagnosis, specific therapeutic recommendations have been established. This review will highlight current understanding and recent advances on RPL, with a special focus on the immunological and genetic etiologies, clinical diagnosis and therapeutic management.