Nirlipta Swain

Thermosensitive ion channel TRPV1 is endogenously expressed in the sperm of a fresh water teleost fish (Labeo rohita) and regulates sperm motility

Sperm cells exhibit extremely high sensitivity in response to slight changes in temperature, osmotic pressure and/or presence of various chemical stimuli. In most cases throughout the evolution, these physico-chemical stimuli trigger Ca2+-signaling and subsequently alter structure, cellular function, motility and survival of the sperm cells. Few reports have recently demonstrated the presence of Transient Receptor Potential (TRP) channels in the sperm cells from higher eukaryotes, mainly from higher mammals. In this work, we have explored if the sperm cells from lower vertebrates can also have thermo-sensitive TRP channels. In this paper, we demonstrate the endogenous presence of one specific thermo-sensitive ion channel, namely Transient Receptor Potential Vanilloid family member sub type 1 (TRPV1) in the sperm cells collected from fresh water teleost fish, Labeo rohita. By using western blot analysis, fluorescence assisted cell sorting (FACS) and confocal microscopy; we confirm the presence of this non-selective cation channel. Activation of TRPV1 by an endogenous activator NADA significantly increases the quality as well as the duration of fish sperm movement. The sperm cell specific expression of TRPV1 matches well with our in silico sequence analysis. The results demonstrate that TRPV1 gene is conserved in various fishes, ranging from 1–3 in copy number, and it originated by fish-specific duplication events within the last 320 million years (MY). To the best of our knowledge, this is the first report demonstrating the presence of any thermo-sensitive TRP channels in the sperm cells of early vertebrates as well as of aquatic animals, which undergo external fertilization in fresh water. This observation may have implications in the aquaculture, breeding of several fresh water and marine fish species and cryopreservation of fish sperms.

Post-Translational Modifications in sperm Proteome: The Chemistry of Proteome diversifications in the Pathophysiology of male factor infertility

BACKGROUND The spermatozoa undergo a series of changes in the epididymis to mature after their release from the testis and subsequently in the female reproductive tract after ejaculation to get capacitated and achieve fertilization potential. Despite having a silenced protein synthesis machinery, the dynamic change in protein profile of the spermatozoa is attributed either to acquisition of new proteins via vescicular transport or to several post-translational modifications (PTMs) occurring on the already expressed protein complement. SCOPE OF REVIEW In this review emphasis is given on the PTMs already reported on the human sperm proteins under normal and pathologic conditions with particular reference to sperm function such as motility and fertilization. An attempt has been made to summarize different protocols and methods used for analysis of PTMs on sperm proteins and the newer trends those were emerging. MAJOR CONCLUSIONS Deciphering the differential occurrence of PTM on protein at ultrastructural level would give us a better insight of structure-function relationship of the particular protein. Protein with multiple PTMs could be used to generate the complex interaction network involved in a physiological function of a sperm. It can be speculated that crosstalk between different PTMs occurring either on same/ other proteins actually regulate the protein stability and activity both in physiological and pathological states. GENERAL SIGNIFICANCE The analytical prospective of various PTMs reported in human spermatozoa and their relevance to sperm function particularly in various pathophysiological states, would pave way for development of biomarkers for diagnosis, prognosis and therapeutic intervention of male infertility.

TRPV4 is endogenously expressed in vertebrate spermatozoa and regulates intracellular calcium in human sperm

Transient Receptor Potential Vanilloid sub-type 4 (TRPV4) is a non-selective cationic channel involved in regulation of temperature, osmolality and different ligand-dependent Ca(2+)-influx. Recently, we have demonstrated that TRPV4 is conserved in all vertebrates. Now we demonstrate that TRPV4 is endogenously expressed in all vertebrate sperm cells ranging from fish to mammals. In human sperm, TRPV4 is present as N-glycosylated protein and its activation induces Ca(2+)-influx. Its expression and localization differs in swim-up and swim-down cells suggesting that TRPV4 is an important determining factor for sperm motility. We demonstrate that pharmacological activation or inhibition of TRPV4 regulates Ca(2+)-wave propagation from head to tail. Such findings may have wide application in male fertility-infertility, contraception and conservation of endangered species as well.

Regulation of TRP channels by steroids: Implications in physiology and diseases

While effects of different steroids on the gene expression and regulation are well established, it is proven that steroids can also exert rapid non-genomic actions in several tissues and cells. In most cases, these non-genomic rapid effects of steroids are actually due to intracellular mobilization of Ca(2+)- and other ions suggesting that Ca(2+) channels are involved in such effects. Transient Receptor Potential (TRP) ion channels or TRPs are the largest group of non-selective and polymodal ion channels which cause Ca(2+)-influx in response to different physical and chemical stimuli. While non-genomic actions of different steroids on different ion channels have been established to some extent, involvement of TRPs in such functions is largely unexplored. In this review, we critically analyze the literature and summarize how different steroids as well as their metabolic precursors and derivatives can exert non-genomic effects by acting on different TRPs qualitatively and/or quantitatively. Such effects have physiological repercussion on systems such as in sperm cells, immune cells, bone cells, neuronal cells and many others. Different TRPs are also endogenously expressed in diverse steroid-producing tissues and thus may have importance in steroid synthesis as well, a process which is tightly controlled by the intracellular Ca(2+) concentrations. Tissue and cell-specific expression of TRP channels are also regulated by different steroids. Understanding of the crosstalk between TRP channels and different steroids may have strong significance in physiological, endocrinological and pharmacological context and in future these compounds can also be used as potential biomedicine.

Expression of temperature-sensitive ion channel TRPM8 in sperm cells correlates with vertebrate evolution.

Transient Receptor Potential cation channel, subfamily Melastatin, member 8 (TRPM8) is involved in detection of cold temperature, different noxious compounds and in execution of thermo- as well as chemo-sensitive responses at cellular levels. Here we explored the molecular evolution of TRPM8 by analyzing sequences from various species. We elucidate that several regions of TRPM8 had different levels of selection pressure but the 4th–5th transmembrane regions remain highly conserved. Analysis of synteny suggests that since vertebrate origin, TRPM8 gene is linked with SPP2, a bone morphogen. TRPM8, especially the N-terminal region of it, seems to be highly variable in human population. We found 16,656 TRPM8 variants in 1092 human genomes with top variations being SNPs, insertions and deletions. A total of 692 missense mutations are also mapped to human TRPM8 protein of which 509 seem to be delateroiours in nature as supported by Polyphen V2, SIFT and Grantham deviation score. Using a highly specific antibody, we demonstrate that TRPM8 is expressed endogenously in the testis of rat and sperm cells of different vertebrates ranging from fish to higher mammals. We hypothesize that TRPM8 had emerged during vertebrate evolution (ca 450 MYA). We propose that expression of TRPM8 in sperm cell and its role in regulating sperm function are important factors that have guided its molecular evolution, and that these understandings may have medical importance.

Histone retention, protein carbonylation, and lipid peroxidation in spermatozoa: Possible role in recurrent pregnancy loss

ABSTRACT Contribution from a defective paternal genome has been attributed to be an important cause for spontaneous recurrent pregnancy loss (RPL). Increased oxidative stress results in decreased detoxification and is a cause for damage to chromatin, proteins, and membrane lipids. The present study aimed to explore if there is a significant relationship between retained histones due to defective packaging of DNA in spermatozoa and oxidative stress. RPL patients (n=16) with a history of ≥2 embryo losses before the 20th week of gestation and no female factor abnormality, and fertile healthy volunteers (n=20) as controls were included in the study. A significant difference in the levels of protein carbonylation and lipid peroxidation together with an increased retention of histones in the experimental groups was noticed. Histone carrying sites for oxidative modification such as arginine and lysine might be responsible for disturbing the paternal epigenomic control during early stages of embryonic differentiation leading to abortion.

Proteomics and Male Infertility

Several plausible factors are known to be associated with a reduction of the male reproductive potential, which may be congenital or acquired. Most of the anomalies underlying male infertility include urogenital abnormalities, varicocele, genetic abnormalities, endocrine disturbances, testicular failure, immunologic problems, cancer, systemic diseases, and infections of the genital tract (Tahmasbpour et al. 2014). Additionally, an altered lifestyle and exposure to gonadotoxic factors would further influence fertility of men (Barazani et al. 2014).

Role of Proteomics in Female Infertility

Deterioration of the female fertility potential has been one of the major areas of research since decades. However, the mysteries and uncertainties still remain largely elusive. Since it contributes an equal 50 % for a successful reproductive outcome, assessment of the exact factors of female infertility might help for the accomplishment of a live birth.

Sperm Proteome: What Is on the Horizon?

As the mammalian spermatozoa transcends from the testis to the end of the epididymal tubule, the functionally incompetent spermatozoa acquires its fertilizing capability. Molecular changes in the spermatozoa at the posttesticular level concern qualitative and quantitative modifications of proteins along with their sugar moieties and membranous lipids mostly associated with motility, egg binding, and penetration processes. Proteomic studies have identified numerous sperm-specific proteins, and recent reports have provided a further understanding of their function with respect to male fertility. High-throughput techniques such as mass spectrometry have shown drastic potential for the identification and study of sperm proteins. In fact, compelling evidence has provided that proteins are critically important in cellular remodeling event and that aberrant expression is associated with pronounced defects in sperm function. This review highlights the posttesticular functional transformation in the epididymis and female reproductive tract with due emphasis on proteomics.

Sperm DNA and Pregnancy Loss After IVF and ICSI

The fertilization potential of spermatozoa is canonically assessed by their concentration, motility, and morphology in the ejaculate. Though these parameters give a general account on the quality of spermatozoa, there is no definite predictive threshold with regard to pregnancy rates. Therefore, there is continuous quest for development of new tests for predicting the chance of pregnancy. Since the primary function of spermatozoon is to deliver the paternal genetic component to the oocyte for the development of foetus, there have been attempts to propose sperm DNA fragmentation tests for male reproductive capability. As transcription and translation stop post-spermiogenesis, these cells are devoid of DNA repair systems and accumulate the damage that occurred during their transit through the epididymis and post-ejaculation. To counteract the consequences, nature has bestowed oocytes and early embryos with the ability to repair sperm DNA damage. Hence, the effect of sperm DNA fragmentation depends on the sum total of sperm chromatin integrity and the capacity of the oocyte to repair it. Various intrinsic and extrinsic factors are responsible for inducing DNA lesions in the spermatozoa which may be enhanced by iatrogenic factors during sperm preparation for IVF and ICSI. Correlation between sperm DNA fragmentation and pregnancy outcome in IVF and ICSI is debated. In this chapter the primary focus is on the role of a spermatozoon carrying DNA damage on pregnancy outcome, the predictive potential of existing DNA tests, the late paternal effect and repair capability of oocytes of damaged sperm DNA, and the possible treatment interventions for better outcome in IVF and ICSI.