E2F1 copy number variations contribute to spermatogenic impairment and cryptorchidism by increasing susceptibility to heat stress

SERBP1 Promotes Stress Granule Clearance by Regulating 26S Proteasome Activity and G3BP1 Ubiquitination and Protects Male Germ Cells from Thermostimuli Damage

Stress granules (SGs) are membraneless cytoplasmic condensates that dynamically assemble in response to various stressors and reversibly disassemble after stimulus removal; however, the mechanisms underlying SG dynamics and their physiological roles in germ cell development are elusive. Here, we show that SERBP1 (SERPINE1 mRNA binding protein 1) is a universal SG component and conserved regulator of SG clearance in somatic and male germ cells. SERBP1 interacts with the SG core component G3BP1 and 26S proteasome proteins PSMD10 and PSMA3 and recruits them to SGs. In the absence of SERBP1, reduced 20S proteasome activity, mislocalized valosin containing protein (VCP) and Fas associated factor family member 2 (FAF2), and diminished K63-linked polyubiquitination of G3BP1 during the SG recovery period were observed. Interestingly, the depletion of SERBP1 in testicular cells in vivo causes increased germ cell apoptosis upon scrotal heat stress. Accordingly, we propose that a SERBP1-mediated mechanism regulates 26S proteasome activity and G3BP1 ubiquitination to facilitate SG clearance in both somatic and germ cell lines.

Contribution of TEX15 genetic variants to the risk of developing severe non-obstructive oligozoospermia

Background: Severe spermatogenic failure (SPGF) represents one of the most relevant causes of male infertility. This pathological condition can lead to extreme abnormalities in the seminal sperm count, such as severe oligozoospermia (SO) or non-obstructive azoospermia (NOA). Most cases of SPGF have an unknown aetiology, and it is known that this idiopathic form of male infertility represents a complex condition. In this study, we aimed to evaluate whether common genetic variation in TEX15, which encodes a key player in spermatogenesis, is involved in the susceptibility to idiopathic SPGF. Materials and Methods: We designed a genetic association study comprising a total of 727 SPGF cases (including 527 NOA and 200 SO) and 1,058 unaffected men from the Iberian Peninsula. Following a tagging strategy, three tag single-nucleotide polymorphisms (SNPs) of TEX15 (rs1362912, rs323342, and rs323346) were selected for genotyping using TaqMan probes. Case-control association tests were then performed by logistic regression models. In silico analyses were also carried out to shed light into the putative functional implications of the studied variants. Results: A significant increase in TEX15-rs1362912 minor allele frequency (MAF) was observed in the group of SO patients (MAF = 0.0842) compared to either the control cohort (MAF = 0.0468, OR = 1.90, p = 7.47E-03) or the NOA group (MAF = 0.0472, OR = 1.83, p = 1.23E-02). The genotype distribution of the SO population was also different from those of both control (p = 1.14E-02) and NOA groups (p = 4.33-02). The analysis of functional annotations of the human genome suggested that the effect of the SO-associated TEX15 variants is likely exerted by alteration of the binding affinity of crucial transcription factors for spermatogenesis. Conclusion: Our results suggest that common variation in TEX15 is involved in the genetic predisposition to SO, thus supporting the notion of idiopathic SPGF as a complex trait.

The effects and molecular mechanism of heat stress on spermatogenesis and the mitigation measures

Under normal conditions, to achieve optimal spermatogenesis, the temperature of the testes should be 2-6 °C lower than body temperature. Cryptorchidism is one of the common pathogenic factors of male infertility. The increase of testicular temperature in male cryptorchidism patients leads to the disorder of body regulation and balance, induces the oxidative stress response of germ cells, destroys the integrity of sperm DNA, yields morphologically abnormal sperm, and leads to excessive apoptosis of germ cells. These physiological changes in the body can reduce sperm fertility and lead to male infertility. This paper describes the factors causing testicular heat stress, including lifestyle and behavioral factors, occupational and environmental factors (external factors), and clinical factors caused by pathological conditions (internal factors). Studies have shown that wearing tight pants or an inappropriate posture when sitting for a long time in daily life, and an increase in ambient temperature caused by different seasons or in different areas, can cause an increase in testicular temperature, induces testicular oxidative stress response, and reduce male fertility. The occurrence of cryptorchidism causes pathological changes within the testis and sperm, such as increased germ cell apoptosis, DNA damage in sperm cells, changes in gene expression, increase in chromosome aneuploidy, and changes in Na⁺/K⁺-ATPase activity, etc. At the end of the article, we list some substances that can relieve oxidative stress in tissues, such as trigonelline, melatonin, R. apetalus, and angelica powder. These substances can protect testicular tissue and relieve the damage caused by excessive oxidative stress.

Retinoblastoma-E2F Transcription Factor Interplay Is Essential for Testicular Development and Male Fertility

The retinoblastoma (RB) protein family members (pRB, p107 and p130) are key regulators of cell cycle progression, but also play crucial roles in apoptosis, and stem cell self-renewal and differentiation. RB proteins exert their effects through binding to E2F transcription factors, which are essential developmental and physiological regulators of tissue and organ homeostasis. According to the canonical view, phosphorylation of RB results in release of E2Fs and induction of genes needed for progress of the cell cycle. However, there are eight members in the E2F transcription factor family with both activator (E2F1-3a) and repressor (E2F3b-E2F8) roles, highlighting the functional diversity of RB-E2F pathway. In this review article we summarize the data showing that RB-E2F interaction is a key cell-autonomous mechanism responsible for establishment and maintenance of lifelong male fertility. We also review the expression pattern of RB proteins and E2F transcription factors in the testis and male germ cells. The available evidence supports that RB and E2F family members are widely and dynamically expressed in the testis, and they are known to have versatile roles during spermatogenesis. Knowledge of the function and significance of RB-E2F interplay for testicular development and spermatogenesis comes primarily from gene knock-out (KO) studies. Several studies conducted in Sertoli cell-specific pRB-KO mice have demonstrated that pRB-mediated inhibition of E2F3 is essential for Sertoli cell functional maturation and cell cycle exit, highlighting that RB-E2F interaction in Sertoli cells is paramount to male fertility. Similarly, ablation of either pRB or E2F1 in the germline results in progressive testicular atrophy due to germline stem cell (GSC) depletion, emphasizing the importance of proper RB-E2F interplay for germline maintenance and lifelong sperm production. In summary, while balanced RB-E2F interplay is essential for cell-autonomous maintenance of GSCs and, the pRB-E2F3 system in Sertoli cells is critical for providing GSC niche thus laying the basis for spermatogenesis.

Current updates and future perspectives in the evaluation of azoospermia: A systematic review

Objectives: To provide a summary of the current evaluation of azoospermia and insights into future perspectives in the evaluation and counselling of men with azoospermia. Methods: A search of PubMed, Cochrane Reviews and Web of Science databases was performed for full-text English-language articles published between 1943 and 2020 focussing on 'future perspectives', 'azoospermia' and 'evaluation'. Results: Azoospermia represents a severe form of male infertility characterised by sperm production so impaired that there are no sperm present in the ejaculate. The current evaluation of azoospermia focusses on patient history and physical examination with selected adjunctive laboratory investigations including serum hormones, a karyotype and screening for Y chromosome microdeletions. Future diagnostics are focussed on identifying the underlying genetic aetiologies for azoospermia, as well as a greater emphasis on screening for systemic illness that men with severe infertility may be predisposed to develop. Conclusion: Azoospermia represents an extreme form of male infertility, and evaluation relies heavily on history and physical examination, as genetic evaluations for these individuals remain limited. Future evaluation will focus on next-generation sequencing and more rigorous evaluation for possible co-existing and future risk of systemic disease. ABBREVIATIONS: ADGRG2, adhesion G protein-coupled receptor G2; ASRM: American Society of Reproductive Medicine; AZF: azoospermia factor; CBAVD: congenital bilateral absence of the vas deferens; CFTR: cystic fibrosis transmembrane conductance regulator; CRKL: CRK-like proto-oncogene; E2F1: E2F transcription factor 1; HAUS7: HAUS augmin-like complex subunit 7; HR: hazard ratio; KS: Klinefelter syndrome; MAZ, MYC-associated zinc finger protein; NGS: next-generation sequencing; NOA: non-obstructive azoospermia; OA: obstructive azoospermia; RHOX: reproductive homeobox on the X chromosome; SH2: SRC homology 2; TAF7L: TATA-box binding protein associated factor 7-like; TEX11: testis-expressed 11; WES: whole-exome sequencing.

Response to stress in biological disorders: Implications of stress granule assembly and function

It is indispensable for cells to adapt and respond to environmental stresses, in order for organisms to survive. Stress granules (SGs) are condensed membrane‐less organelles dynamically formed in the cytoplasm of eukaryotes cells to cope with diverse intracellular or extracellular stress factors, with features of liquid‐liquid phase separation. They are composed of multiple constituents, including translationally stalled mRNAs, translation initiation factors, RNA‐binding proteins and also non‐RNA‐binding proteins. SG formation is triggered by stress stimuli, viral infection and signal transduction, while aberrant assembly of SGs may contribute to tissue degenerative diseases. Recently, a growing body of evidence has emerged on SG response mechanisms for cells facing high temperatures, oxidative stress and osmotic stress. In this review, we aim to summarize factors affecting SGs assembly, present the impact of SGs on germ cell development and other biological processes. We particularly emphasize the significance of recently reported RNA modifications in SG stress responses. In parallel, we also review all current perspectives on the roles of SGs in male germ cells, with a particular focus on the dynamics of SG assembly.

E2F1 regulates testicular descent and controls spermatogenesis by influencing WNT4 signaling

Cryptorchidism is the most common urologic birth defect in men and is a predisposing factor of male infertility and testicular cancer, yet the etiology remains largely unknown. E2F1 microdeletions and microduplications contribute to cryptorchidism, infertility and testicular tumors. Although E2f1 deletion or overexpression in mice causes spermatogenic failure, the mechanism by which E2f1 influences testicular function is unknown. This investigation revealed that E2f1-null mice develop cryptorchidism with severe gubernacular defects and progressive loss of germ cells resulting in infertility and, in rare cases, testicular tumors. It was hypothesized that germ cell depletion resulted from an increase in WNT4 levels. To test this hypothesis, the phenotype of a double-null mouse model lacking both Wnt4 and E2f1 in germ cells was analyzed. Double-null mice are fertile. This finding indicates that germ cell maintenance is dependent on E2f1 repression of Wnt4, supporting a role for Wnt4 in germ cell survival. In the future, modulation of WNT4 expression in men with cryptorchidism and spermatogenic failure due to E2F1 copy number variations may provide a novel approach to improve their spermatogenesis and perhaps their fertility potential after orchidopexy.

Male infertility and genitourinary birth defects: there is more than meets the eye

Male factor infertility is a significant problem present in up to 50% of infertile couples. The relationship between male infertility and systemic disease is of significant interest, and emerging evidence suggests a relationship between male infertility and male genitourinary (GU) birth defects (cryptorchidism, hypospadias, ambiguous genitalia, and congenital anomalies of the kidney and urinary tract). Many of these birth defects are treated in isolation by busy urologists without acknowledgment that these may be related to more global syndromic conditions. Conversely, geneticists and nonurologists who treat variable systemic phenotypes may overlook GU defects, which are indeed related conditions. Many of these defects are attributed to copy number variants dosage-sensitive genes due to chromosome microdeletions or microduplications. These variants are responsible for disease phenotypes seen in the general population. The copy number variants described in this review are syndromic in some cases and responsible for both GU birth defects as well as other systemic phenotypes. This review highlights the emerging evidence between these birth defects, male infertility, and other systemic conditions.

E2F1 germline copy number variations and melanoma susceptibility

Background

Melanoma is an aggressive type of skin cancer whose aetiology remains elusive as both environmental and genetic factors can contribute to its development. Recent studies have demonstrated the existence of multiple copies of E2F1 gene in melanoma specimens which could explain the deregulated E2F1 activity in this type of cancer. This finding suggests a key role for this transcription factor in the malignant transformation of melanocytes. Therefore, E2F1 has been considered as a potential therapeutic target for this form of skin cancer. Since germline copy number variations (CNVs) have been associated with increased susceptibility to different types of cancer, the aim of our study was to assess germline E2F1 CNV in melanoma patients. However, CNVs not necessarily lead to gene dosage imbalance, hence, further factors, in association with CNVs, could contribute to clinical manifestations. Considering that heat stress has been hypothesised as a contributing factor to skin cancer, we also investigated the effect of heat stress on E2F1 expression.

Methods

E2F1 CNV was measured in genomic DNA isolated from blood of 552 patients diagnosed with melanoma and 520 healthy subjects using TaqMan Copy Number Assays. E2F1 mRNA expression was also evaluated by RT-qPCR in the melanoma cell line, SK MEL 267, before and after exposure to heat stress.

Results

We found that patients diagnosed with melanoma (1.6%, 9/552) harboured frequently altered germline E2F1 copies compared to healthy subjects (0%, 0/520). Moreover, the difference among the two groups was statistically significant (p = 0.004). Furthermore, we found that heat exposure alone can significantly induce E2F1 expression.

Conclusions

This is the first study that shows a relation between germline E2F1 CNV and melanoma, suggesting that altered copies of this gene might be a predisposing factor to skin cancer. Our results also suggest that environmental insults, such as heat stress, could contribute to an aberrant E2F1 activity by inducing E2F1 mRNA expression. Therefore, subjects with multiple constitutive copies of E2F1 are at greater risk of developing melanoma when exposed to heat. Altogether our results corroborate with the hypothesis that susceptibility to melanoma depends on both the environment and genetic factors.

Testicular Cancer: Genes, Environment, Hormones

Testicular cancer (TC) represents one of the most peculiar clinical challenges at present. In fact, currently treatments are so effective ensuring a 5 years disease-free survival rate in nearly 95% of patients. On the other hand however, TC represents the most frequent newly diagnosed form of cancer in men between the ages of 14 and 44 years, with an incidence ranging from <1 to 9.9 affected individuals per 100,000 males across countries, while the overall incidence is also increasing worldwide. Furthermore, cancer survivors show a 2% risk of developing cancer in the contralateral testis within 15 years of initial diagnosis. This complex and multifaceted scenario requires a great deal of effort to understand the clinical base of available evidence. It is now clear that genetic, environmental and hormonal risk factors concur and mutually influence both the development of the disease and its prognosis, in terms of response to treatment and the risk of recurrence. In this paper, the most recent issues describing the relative contribution of the aforementioned risk factors in TC development are discussed. In addition, particular attention is paid to the exposure to environmental chemical substances and thermal stress, whose role in cancer development and progression has recently been investigated at the molecular level.