Vasa expression in spermatogenic cells during the reproductive-cycle phases ofPodarcis sicula(Reptilia, Lacertidae)

Could Exposure to Glyphosate Pose a Risk to the Survival of Wild Animals? A Case Study on the Field Lizard Podarcis siculus

Soil contaminants (herbicides, pesticides, and heavy metals) are among the main causes of change in terrestrial ecosystems. These substances lead to a general loss of biodiversity, both of flora and fauna and being able to biomagnify and pass through the food chain, they can endanger the survival of terrestrial vertebrates at the top of this chain. This review analyzes the risks associated with exposure to glyphosate, the active principle of many herbicide products, for the reproductive health of the field lizard (Podarcis siculus) potentially exposed to the substance in its natural habitat; therefore, introducing it as a possible model organism. Data demonstrate that glyphosate is toxic for this animal, affecting the health of the reproductive organs, both in males and females, and of the liver, the main detoxifying organ and closely involved in the female reproductive process. Sharing structural and functional characteristics of these organs with many other vertebrates, the information obtained with this reptile represents a wake-up call to consider when analyzing the cost/benefit ratio of glyphosate-based substances. The data clearly demonstrate that the P. siculus lizard can be considered a good target organism to study the reproductive risk assessment and hazards of exposure to soil contaminants on wild terrestrial vertebrates.

The Italian Wall Lizard Podarcis siculus as a Biological Model for Research in Male Reproductive Toxicology

Spermatogenesis is a genetically driven differentiation process that occurs in the testis and leads to the formation of spermatozoa. This process is extensively studied in several experimental models, particularly in vertebrates that share the morphological structure and functionality of the mammalian testis. Although reptiles are not generally considered biological models, the lizard Podarcis siculus has represented a suitable organism for the study of spermatogenesis over the years. In this lizard, the process of spermatogenesis is regulated by the interaction between systemic factors such as gonadotropins and local factors, i.e., molecules produced by the somatic and germinal cells of the testis. Many exogenous substances are able to alter the production of these regulative factors, thus altering the course of spermatogenesis, and P. siculus has proven to be an excellent model for studying the effects of various endogenous or exogenous substances on mechanisms underlying spermatogenesis. This review summarizes the available data on the effects of different substances on the control of spermatogenesis, highlighting the induced morphological and molecular alterations. Overall, the data show that sex hormone levels as well as the final stages of spermatogenesis are most affected by an imbalance of endogenous compounds or contamination by environmental pollutants. This is helpful for the male individual, since the damage, not affecting the spermatogonial stem cells, can be considered transient and not irreversible.

Immunolocalization of Vasa, PIWI, and TDRKH proteins in male germ cells during spermatogenesis of the teleost fish Poecilia reticulata

Vasa, PIWI and TDRKH are conserved components of germ granules that in metazoans are involved in germline specification and differentiation, as documented by mutational experiments in some model animals. So far, investigations on PIWI during spermatogenesis of fish has been limited to a few species, and no information is available for TDRKH, another protein involved in the piRNA pathway. In this study, the immunolocalization of these three germline determinants was analyzed in male gonads of the teleost fish Poecilia reticulata to document their localization pattern in the different stages of germ cell differentiation. To analyze their distribution pattern during the different stages of spermatogenesis we performed immunohistochemistry (IHC) and immunofluorescence (IF) assays using primary polyclonal antibodies after testing their specificity with Western Blot. Moreover, sections of testis stained with haematoxylin and eosin clarified the structural organization of P. reticulata testis, while the use of the confocal microscope and the nuclear staining clarified the different stages of germ cell differentiation during spermatogenesis. The results showed that Vasa, PIWI and TDRKH were specifically immunolocalized in the germ cells of P. reticulata, with no specific signal detected in Sertoli cells and in other somatic cells of the gonad. These markers were detected in all stages of differentiation from early spermatogonia to advanced spermatids. Vasa staining was the strongest in spermatogonia, and then decreases throughout differentiation. Instead, both PIWI and TDRKH staining increases during differentiation, and their distribution pattern, similar to what observed in the mouse, suggests their concerted participation in the piRNA pathway also in this fish.

Vasa expression is associated with sex differentiation in the Asian yellow pond turtle, Mauremys mutica

Vasa, one of the best-studied germ cell markers plays a critical role in germ cell development and differentiation in animals. Vasa deficiency would lead to male-specific sterility in most vertebrates, but female sterility in the fly. However, the role of the vasa gene involved in germ cell differentiation is largely elusive. Here, we first characterized the expression profile of vasa products in the Asian yellow pond turtle by quantitative reverse-transcription polymerase chain reaction and fluorescence immunostaining. The results showed that vasa messenger RNA (mRNA) is initially detected in embryos at stage 16, and then dramatically increased in embryos at stage 19. In particular, like the sex-related genes, vasa mRNA exhibited differential expression in embryos between the male-producing temperature (MPT, 25°C) and the female-producing temperature (FPT, 33°C), whereas there was no difference in methylation levels of vasa promoter detected between FPT and MPT. In contrast, in the adult Asian yellow pond, the level of vasa mRNA was much higher in the testis than ovary. Moreover, the immunostaining on testicular sections and cells showed that Vasa protein was exclusively expressed in germ cells: Weak but detectable in spermatogonia, highest in spermatocytes, moderate and concentrated in chromatid bodies in spermatids and spermatozoa, and bare in somatic cells. The expression profile of Vasa protein is similar in turtle species studied so far but distinct from those in fish species in this study. The findings of this study would provide new insights into our understanding of the conservation and divergence of the vasa gene, even other germ cell genes across phyla.

Evaluation of the Pharmacophoric Role of the O-O Bond in Synthetic Antileishmanial Compounds: Comparison between 1,2-Dioxanes and Tetrahydropyrans

Leishmaniases are neglected diseases that can be treated with a limited drug arsenal; the development of new molecules is therefore a priority. Recent evidence indicates that endoperoxides, including artemisinin and its derivatives, possess antileishmanial activity. Here, 1,2-dioxanes were synthesized with their corresponding tetrahydropyrans lacking the peroxide bridge, to ascertain if this group is a key pharmacophoric requirement for the antileishmanial bioactivity. Newly synthesized compounds were examined in vitro, and their mechanism of action was preliminarily investigated. Three endoperoxides and their corresponding tetrahydropyrans effectively inhibited the growth of Leishmania donovani promastigotes and amastigotes, and iron did not play a significant role in their activation. Further, reactive oxygen species were produced in both endoperoxide- and tetrahydropyran-treated promastigotes. In conclusion, the peroxide group proved not to be crucial for the antileishmanial bioactivity of endoperoxides, under the tested conditions. Our findings reveal the potential of both 1,2-dioxanes and tetrahydropyrans as lead compounds for novel therapies against Leishmania.

Spermatogenesis and regulatory factors in the wall lizard Podarcis sicula

Spermatogenesis is an extraordinarily complex process, regulated by several factors, which leads to the differentiation of spermatogonia into spermatozoa. Among vertebrates, several reports have been focused on the lizard Podarcis sicula, a seasonal breeder and a good model for the study of reproductive processes. The goal of this review is to resume all the available data about systemic and above all local control factors involved in the control of P. sicula testicular activity. During the seasonal reproductive cycle, the variation of the expression levels of these factors determines significant variations that induce the activation or blocking of spermatogenesis. The data supplied in this review, in addition to analyze the current literature regarding the main actors of Podarcis sicula spermatogenesis, will hopefully provide a basic model that can be used for further studies on the intratesticular interaction between molecular factors that control spermatogenesis.

Insights into Germline Development and Differentiation in Molluscs and Reptiles: The Use of Molecular Markers in the Study of Non-model Animals

When shifting research focus from model to non-model species, many differences in the working approach should be taken into account and usually methodological modifications are required because of the lack of genetics/genomics and developmental information for the vast majority of organisms. This lack of data accounts for the largely incomplete understanding of how the two components-genes and developmental programs-are intermingled in the process of evolution. A deeper level of knowledge was reached for a few model animals, making it possible to understand some of the processes that guide developmental changes during evolutionary time. However, it is often difficult to transfer the obtained information to other, even closely related, animals. In this chapter, we present and discuss some examples, such as the choice of molecular markers to be used to characterize differentiation and developmental processes. The chosen examples pertain to the study of germline in molluscs, reptiles, and other non-model animals.

Molecular characterization of vasa homologue in marbled goby, Oxyeleotris marmorata: Transcription and localization analysis during gametogenesis and embryogenesis

Identification of germ cell markers is important for investigating reproduction biology in fish. Vasa is one of the most studied germ cell markers in mammals and lower vertebrates including fish. Here, we characterized a vasa homologue from the fish marbled goby (Oxyeleotris marmorata), termed omvasa. The full length of omvasa cDNA is 2344 bp and encodes 658 amino acids, sharing high identities with Vasa homologues of other vertebrates. OmVasa protein contains 15 RG/RGG repeats at N-terminus, 2 ATPase motifs, as well as RNA unwinding and RNA binding domains at C-terminus. Phylogenetic tree showed that omVasa had the closest relationship with the Vasa homologue from the fish Boleophthalmus pectinirostris, the great blue-spotted mudskipper. qRT-PCR analysis indicated that omvasa was specifically transcribed in gonads, and the transcription level was gradually increased during oocyte development. The germ cell-specific distribution of omvasa mRNA was revealed by fluorescent in situ hybridization. In ovary, the signal of omvasa RNA displayed strong-weak-strong dynamics from oogonia over pre-vitellogenic oocytes to vitellogenic oocytes. In testis, omvasa signal was strong in spermatogonia, modest in spermatocytes but undetectable in spermatids and somatic cells. During embryogenesis, the transcription of omvasa mRNA was high at blastula stage, gradually decreased from gastrula stage and maintained at a low level in later developmental stages. Whole mount in situ hybridization indicated that omvasa mRNA was specific to primordial germ cells (PGCs). In summary, marbled goby vasa is a germ cell-specific transcript during gametogenesis, and can be used as an ideal marker for tracing PGC formation and migration, which is pivotal to germ cell manipulation in this species.

PL10 DEAD-Box Protein is Expressed during Germ Cell Differentiation in the Reptile Podarcis sicula (Family Lacertidae)

Among genes involved in the regulation of germ cell differentiation, those of DDX4/Vasa and the Ded1/DDX3 subfamilies encode for DEAD-box ATP-dependent RNA helicases, proteins involved in many mechanisms related to RNA processing. For the first time in reptiles, using specific antibodies at confocal microscopy, we analysed the localization pattern of a Ded1/DDX3 subfamily member in testis and ovary of Podarcis sicula (Ps-PL10) during the reproductive cycle. In testis, Ps-PL10 is expressed in the cytoplasm of spermatocytes and it is not detected in spermatogonia. Differently from Ps-VASA, in round spermatids, Ps-PL10 is not segregated in the chromatoid body but it accumulates in the cytoplasm of residual bodies, and mature spermatozoa are unstained. These observations suggest that in males, Ps-PL10 (1) is involved in spermatogenesis and (2) is then eliminated with residual bodies. In the ovary, Ps-PL10 is present with granules in the cytoplasm of early meiotic cells of the germinal bed (GB), while it is not present in oogonia and somatic cells of the GB stroma. In follicular cells of ovarian follicles, Ps-PL10 expression starts after their fusion with the oocyte. Numerous Ps-PL10 spots are visible in pyriform (nurse-like) cells concomitantly with the protein accumulation in the cytoplasm of differentiating oocyte. In pyriform cells, Ps-PL10 spots are present in the cytoplasm and nuclei, as observed for Ps-VASA, and in the nucleoli, suggesting for Ps-PL10 a role in rRNA processing and in the transport of molecules from the nucleus to cytoplasm and from nurse cells to the oocyte.

Localization and distribution of gonadal proteins in the oviparous lizard Sceloporus aeneus (Squamata: Phrynosomatidae)

Among vertebrates, several specific proteins are involved in the function and development of gonads. Several genes such as SOX9, FOXL2, DDX4, IFITM3, and DPPA3, are active during embryonic differentiation and maintain their expression in adult tissues, playing important roles in the function and development of the line cell, where these are produced. Among reptiles, molecular mechanisms for sex differentiation have been analyzed in turtles, crocodiles, and some lizards, while in adult stages such studies are scarce. The aim of this study was to locate and analyze the distribution of important gonadal proteins in adult and embryonic ovaries and testes of the oviparous lizard Sceloporus aeneus (Squamata: Phrynosomatidae). Adult specimens and embryos of the lizard S. aeneus were collected in Milpa Alta, a suburb located Southwest of Mexico City. Expression of gonadal proteins was analyzed using immunofluorescent staining and confocal microscopy. Our results showed that SOX9 is located in Sertoli cells of embryonic and adult testes. FOXL2 is expressed in follicular cells of adult ovaries. DDX4 and IFITM3 are located in germ line cells as well as in follicular cells of adult ovaries. DPPA3 was observed in somatic and germ line cells of adult and embryonic gonads. Our observations show that important molecules of vertebrate ovaries and testes are conserved in S. aeneus and it is suggested that these may have a similar role during gonadal development and function.