The sperm flagellum is essential for male fertility. Multiple morphological abnormalities of the sperm flagella (MMAF) is a severe form of asthenoteratozoospermia. MMAF phenotypes are understood to result from pathogenic variants of genes from multiple families including AKAP, DANI, DNAH, RSPH, CCDC, CFAP, TTC, and LRRC, among others. The Leucine-rich repeat protein (LRRC) family includes two members reported to cause MMAF phenotypes: Lrrc6 and Lrrc50. Despite vigorous research towards understanding the pathogenesis of MMAF-related diseases, many genes remain unknown underlying the flagellum biogenesis. Here, we found that Leucine-rich repeat containing 46 (LRRC46) is specifically expressed in the testes of adult mice, and show that LRRC46 is essential for sperm flagellum biogenesis. Both scanning electron microscopy (SEM) and Papanicolaou staining (PS) presents that the knockout of Lrrc46 in mice resulted in typical MMAF phenotypes, including sperm with short, coiled, and irregular flagella. The male KO mice had reduced total sperm counts, impaired sperm motility, and were completely infertile. No reproductive phenotypes were detected in Lrrc46^−/− female mice. Immunofluorescence (IF) assays showed that LRRC46 was present throughout the entire flagella of control sperm, albeit with evident concentration at the mid-piece. Transmission electron microscopy (TEM) demonstrated striking flagellar defects with axonemal and mitochondrial sheath malformations. About the important part of the Materials and Methods, SEM and PS were used to observe the typical MMAF-related irregular flagella morphological phenotypes, TEM was used to further inspect the sperm flagellum defects in ultrastructure, and IF was chosen to confirm the location of protein. Our study suggests that LRRC46 is an essential protein for sperm flagellum biogenesis, and its mutations might be associated with MMAF that causes male infertility. Thus, our study provides insights for understanding developmental processes underlying sperm flagellum formation and contribute to further observe the pathogenic genes that cause male infertility.

The axoneme and accessory structures of flagella are critical for sperm motility and male fertilization. Sperm production needs precise and highly ordered gene expression to initiate and sustain the many cellular processes that result in mature spermatozoa. Here, we identified a testis enriched gene transmembrane protein 232 (Tmem232), which is essential for the structural integrity of the spermatozoa flagella axoneme. Tmem232 knockout mice were generated for in vivo analyses of its functions in spermatogenesis. Phenotypic analysis showed that deletion of Tmem232 in mice causes male-specific infertility. Transmission electron microscopy together with scanning electron microscopy were applied to analyze the spermatozoa flagella and it was observed that the lack of TMEM232 caused failure of the cytoplasm removal and the absence of the 7th outer microtubule doublet with its corresponding outer dense fiber (ODF). Co-IP assays further identified that TMEM232 interacts with ODF family protein ODF1, which is essential to maintain sperm motility. In conclusion, our findings indicate that TMEM232 is a critical protein for male fertility and sperm motility by regulating sperm cytoplasm removal and maintaining axoneme integrity.

Sperm motility and structural integrity are essential for successful fertilization in vivo, and any hindrance of the correct assembly of the axoneme and peri-axonemal structures in the sperm flagellum can lead to fertility problems. While there has been considerable advancement in studying diseases related to the flagellum, the underlying mechanisms that control sperm movement are not yet fully understood. In this study, we reveal that the tetratricopeptide repeat protein 6 (Ttc6) gene, expressed mainly in the testes, plays a crucial role in maintaining male fertility in mice. We further demonstrate that the knockout of Ttc6 in mice results in decreased sperm motility and induces an abnormal circular swimming pattern, consequently leading to male subfertility. Morphological analysis showed an atypical hairpin-like appearance of the spermatozoa, and ultrastructural studies showed unsheathed flagella at the juncture between the midpiece and principal piece. Collectively, these findings suggest that TTC6 plays an essential role in maintaining the stability of the annulus region of the sperm flagellum, thus ensuring the swift and directed motion of sperm.

Objective. During in vitro fertilization-embryo transfer (IVF-ET) treatment, the reproductive endocrine regulatory mechanisms hold pivotal importance. Specifically, the serum estradiol (E2) level during ovulation emerges as a critical factor influencing pregnancy outcomes. This retrospective study aimed to comprehensively compare two common clinical regimens based on the grouping of serum E2 levels and the number of oocytes retrieved on the trigger day. Our objective was to evaluate the pregnancy outcomes in IVF-ET patients across different ovarian response groups, exploring the efficacy of the dual-trigger and single-trigger regimens to provide valuable insights for optimizing clinical strategies in the context of IVF-ET. Methods. A retrospective analysis was conducted on the clinical data of 2778 infertile patients who underwent ART (IVF/ICSI). Subsequently, a detailed statistical analysis was performed on 1032 patients following an antagonist regimen. Participants were categorized into single-trigger and dual-trigger groups based on real-world trigger protocols, considering different ovarian responses. Comprehensive statistical assessments were conducted on baseline characteristics, ovulation induction, and pregnancy outcomes. Results. Baseline characteristics and cycle parameters among the three patient groups (high ovarian response, normal response, and poor response) exhibited no significant differences between the dual-trigger and single-trigger regimen groups. Despite the dual-trigger regimen utilizing a significantly lower HCG dose, no notable discrepancies were observed in laboratory results and pregnancy outcomes (embryo transfer rate, pregnancy rate, and live birth rate) for normal and high responders. Remarkably, E2 levels were higher in the dual-trigger group compared to the single-trigger group. In high and normal responders, the dual-trigger regimen demonstrated increased oocyte counts and oocyte acquisition rates, coupled with decreased transfer cancellation rates attributed to ovarian hyperstimulation syndrome (OHSS). Intriguingly, patients with a poor ovarian response experienced no graft cancellations due to OHSS prevention in either group. Conclusion. For patients with high and normal ovarian responses, the utilization of a dual-trigger regimen on the trigger day effectively mitigates the risk of OHSS. Our large sample study supports the substitutability of the dual-trigger regimen over the single-trigger regimen without compromising pregnancy outcomes. However, this conclusion is not applicable to patients with poor ovarian responses. The results of this study highlight the necessity of adopting a customized and individualized treatment approach that should be based on the patient's ovarian response. Additionally, recognizing the pivotal role of the endocrine environment in influencing pregnancy outcomes and the occurrence of OHSS, further exploration of the effects of different triggering regimens on endocrine parameters is warranted. Such investigations will contribute to enhancing the reproductive outcomes of IVF-ET technology.

Infertility affects about 17.5% of couples, with male factors accounting for approximately 50% of cases. Cytoskeletal remodeling is increasingly recognized as a critical component of male reproductive function, particularly in the regulation of testosterone synthesis by Leydig cells. However, the underlying molecular mechanisms remain poorly defined. Rho-associated coiled-coil-containing kinase (ROCK), a key cytoskeletal regulator, influences actin dynamics, impacting intracellular trafficking. In this study, we investigated the roles of ROCK1 and ROCK2 in Leydig cells using the TM3 cell model. Pharmacological inhibition of ROCK activity with Y-27632 impaired actin cytoskeleton organization, reduced the phosphorylation of LIMK, COFILIN, and MLC2, and disrupted the colocalization of F-actin with StAR and cholesterol, thereby decreasing testosterone production. Furthermore, RNA-seq revealed that hCG promotes transcription of steroidogenesis-related genes, while ROCK inhibition reverses this effect. Silencing of ROCK1 via siRNA mimicked the effects of ROCK-i, suppressing steroidogenic gene expression and testosterone synthesis. In contrast, ROCK2 knockdown enhanced testosterone secretion, promoted F-actin remodeling, and increased traffic of cholesterol targeting mitochondria. These opposing effects triggered distinct responses in the SCAP–SREBP2 axis, indicating a feedback mechanism regulating cholesterol homeostasis. Collectively, our findings uncover the isoform-specific roles of ROCK1 and ROCK2 in coordinating cytoskeletal dynamics and steroidogenic activity, providing new insights into the regulation of male reproductive endocrinology and identifying potential therapeutic targets for androgen deficiency and male infertility.