Embryonic developmental arrest in the annual killifish Austrolebias charrua: A proteomic approach to diapause III

Diapause is a reversible developmental arrest faced by many organisms in harsh environments. Annual killifish present this mechanism in three possible stages of development. Killifish are freshwater teleosts from Africa and America that live in ephemeral ponds, which dry up in the dry season. The juvenile and adult populations die, and the embryos remain buried in the bottom mud until the next rainy season. Thus, species survival is entirely embryo-dependent, and they are perhaps the most remarkable extremophile organisms among vertebrates. The aim of the present study was to gather information about embryonic diapauses with the use of a "shotgun" proteomics approach in diapause III and prehatching Austrolebias charrua embryos. Our results provide insight into the molecular mechanisms of diapause III. Data are available via ProteomeXchange with identifier PXD025196. We detected a diapause-dependent change in a large group of proteins involved in different functions, such as metabolic pathways and stress tolerance, as well as proteins related to DNA repair and epigenetic modifications. Furthermore, we observed a diapause-associated switch in cytoskeletal proteins. This first glance into global protein expression differences between prehatching and diapause III could provide clues regarding the induction/maintenance of this developmental arrest in A. charrua embryos. There appears to be no single mechanism underlying diapause and the present data expand our knowledge of the molecular basis of diapause regulation. This information will be useful for future comparative approaches among different diapauses in annual killifish and/or other organisms that experience developmental arrest.

Building the embryo of Developmental Biology in Uruguay

In Uruguay, a country with a small population, and hence a small scientific community, there were no classical embryologists as such in the past. However, in the decade of the 1950s, a cumulus of favorable conditions gave rise to highly active and modern research groups in the fields of cytology and physiology, which eventually contributed to developmental biology. The advent of a long dictatorship between the 1970's and 1980's caused two things: a strong lag in local research and the migration of young investigators who learned abroad new disciplines and technologies. The coming back to democracy allowed for the return of some, now as solid researchers, and together with those who stayed, built a previously inexistent postgraduate training program and a globally-integrated academy that fostered diversity of research disciplines, including developmental biology. In this paper, we highlight the key contributions of pioneer researchers and the significant role played by academic and funding national institutions in the growth and consolidation of developmental biology in our country.

A global community effort to decipher the unique biology of annual killifish

Over the past 50 years, annual killifishes arose as alternative model organisms for studies of vertebrate biology. The annual fish offers exceptional advantages for studies of genetics, genomics, developmental biology, population dynamics, ecology, biogeography, and evolution. They inhabit extremely variable freshwater environments in Africa and South America, have a short lifespan and a set of unique and fascinating developmental characteristics. Embryos survive within the dry substrate during the dry season, whereas the adult population dies. Thus, the survival of the populations is entirely dependent on the buried embryos that hatch the next rainy season. Although Old and New World species share similarities in their life cycle, they also have different adaptive responses associated with climate-related selective pressures. Therefore, contrasting different species from these areas is essential to understand unique adaptations to heterogeneous environment. A network of laboratories (United States, Czech Republic, Italy, Brazil, Chile, and Uruguay) is working and collaborating on many aspects of the biology of annual fishes. Participating researchers share projects and cross-training undergraduate and graduate students. These efforts resulted in two International Symposia (2010 and 2015) that took place in Montevideo and an international book. Herein, we summarize the progress made by this global community of scientists. Developmental Dynamics 246:807-811, 2017. © 2017 Wiley Periodicals, Inc.

Sex determination in annual fishes: Searching for the master sex-determining gene in Austrolebias charrua (Cyprinodontiformes, Rivulidae)

Evolution of sex determination and differentiation in fishes involves a broad range of sex strategies (hermaphroditism, gonochorism, unisexuality, environmental and genetic sex determination). Annual fishes inhabit temporary ponds that dry out during the dry season when adults die. The embryos exhibit an atypical developmental pattern and remain buried in the bottom mud until the next rainy season. To elucidate genomic factors involved in the sex determination in annual fish, we explored the presence of a candidate sex-specific gene related to the cascade network in Austrolebias charrua. All phylogenetic analyses showed a high posterior probability of occurrence for a clade integrated by nuclear sequences (aprox. 900 bp) from both adults (male and female), with partial cDNA fragments of A. charrua from juveniles (male) and the dsx D. melanogaster gene. The expressed fragment was detected from blastula to adulthood stages showing a sexually dimorphic expression pattern. The isolated cDNA sequence is clearly related to dsx D. melanogaster gene and might be located near the top of the sex determination cascade in this species.

Annual fish: developmental adaptations for an extreme environment

Annual fish are freshwater teleosts found in South America and Africa that are exposed to an extremely variable environment. They develop and reproduce in seasonal ponds that dry during the summer eliminating the entire adult population. Remarkably, desiccation-resistant embryos survive in these dry ponds that hatch during the next rainy season when the ponds are recreated. Among vertebrates, they represent one of the most remarkable extremophiles. They share several features with other fish models; however, they exhibit unique traits related to their peculiar life cycle. Epiboly is temporally and spatially uncoupled from organogenesis, and the embryos can undergo reversible developmental arrests (diapauses). These attributes make them a useful model to study diverse topics in developmental biology using a comparative and evolutionary approach. In this article, different aspects related to annual fish biology, taxonomy and phylogenetic considerations, reproductive strategy, and developmental characteristics with special focus on arrests, are summarized. The current challenge is to document and determine the factors that generate such high diversity and unique adaptations of annual fish. To understand this complexity, interdisciplinary approaches are being employed taking into consideration evolutionary biology, ethology, reproductive strategies, regulation of developmental mechanisms, and senescence.

Gamete interactions in teleost fish: the egg envelope. Basic studies and perspectives as environmental biomonitor

The current knowledge about teleost fish egg envelope is summarized. The paper analyzes the organization and deposition process of the protein composition and genes involved in the synthesis of teleost fish egg envelopes and their role in gamete interaction during fertilization. Pelagic and demersal species that our research group is working with are especially considered. The vertebrate ZP family of proteins, the evolution and relationship among the different genes and their expression are taken into account. We consider fish envelope as a possible biomonitor for ecological contaminants. The biotechnological applications for aquaculture and genomic and post-genomic approaches are auspicious.

Involvement of ppGalNAc-T6, a new colon cancer marker, in the molecular basis of simple mucin-type O-glycosylated antigen expression

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Background: Abnormal O-glycosylation is one of the most common changes during colon carcinogenesis, leading to the expression of short truncated O-glycan antigens (such as Tn, sialyl-Tn, Tk, and core 6). These structures which are related with the malignant behavior are actively investigated as immunotherapeutic targets. The ppGalNAc-T family enzymes regulate the initial step of mucin O-glycosylation and could be responsible for the altered glycosylation observed in cancer. The objective of this work was to describe the abnormal expression of ppGalNAc-Ts in colon cancer comparing its relationship with incomplete O- glycosylated antigens. Methods: We studied the gene expression of ppGalNAc-Ts in colon cell lines by RT-PCR assays. Using immunohistochemistry we determined ppGalNAc-T6, Tn, sialyl-Tn, Tk, and core 6 expression in 64 colon cancer samples and in 10 normal colon tissues. Results: We found that ppGalNAc-T6 (an enzyme usually restricted to normal placenta, trachea, brain, and pancreas) is expressed by colon cancer cell lines. Using immunohistochemistry we detected ppGalNAc-T6 in 70.3% of cancer samples with no staining in normal colon tissues. Staining pattern was predominantly cytoplasmatic. Staining of Tn, STn, core 6 and Tk antigens was observed in 87,5%, 79,6%, 76,5% and 68.7% of tumors, respectively. We observed a statistically significant relationship between the enzyme expression and Tn antigen (p=0.009) and core 6 (p=0.001). No relationship was observed between the enzyme expression and sialyl-Tn (p = 0.406) and Tk (p= 0.18) antigens. Conclusions: ppGalNac-T6 is a new tumor marker for colon cancer and its expression is related with the accumulation of two O-glycosylated antigens such as Tn and core 6. This is the first evidence in human tissues suggesting that the abnormal expression of a ppGalNac transferase could be in the molecular basis of aberrant O-glycosylated antigens accumulation in cancer.

No significant financial relationships to disclose.

Seminiferous epithelium cycle of a hantavirus reservoir, the long-tailed mouse Oligoryzomys flavescens (Rodentia-Cricetidae)

Oligoryzomys flavescens, a common rodent of the temperate regions of South America, has been identified as a Hantavirus reservoir. There is still little information concerning its reproductive biology, which is essential to devise effective control measurement of natural populations. This rodent is a seasonal breeder and adult males exhibit a short period of testicular regression during winter months (June-August). In the present study we provided a histological and ultrastructural analysis of the composition of the testis of sexually mature O. flavescens during the breeding season. Over 95% of the testicular parenchyma was occupied by the seminiferous tubules and less than 5% by the interstitial tissue. The mean tubular diameter and epithelium height were 147.2 and 57.8 microm, respectively. The spermatogenic wave was characterized and eight spermatogenesis stages were identified according to the tubular morphology method. Their length, estimated as their relative frequencies, were (I-VIII) 8.8, 14.9, 4.0, 5.0, 10.4, 5.8, 27.0, and 23.9. Ultrastructural features of spermiogenesis are shown for the first time in a sigmodontine rodent.

Sex differentiation pattern in the annual fish Austrolebias charrua (Cyprinodontiformes: Rivulidae)

Sex differentiation process, determination of sexual strategy, and gametogenesis of the annual fish Austrolebias charrua are established. Evidence of histological sex differentiation in an antero-posterior gradient was observed in pre-hatching stages. Sexual strategy corresponds to the "differentiated gonochoric" pattern. Histological analyses of adult gonads showed an asynchronous spawning mode for females and continuous spawning for males. Mature oocytes presented fluid yolk. Testis organization corresponded to a restricted spermatogonial model. Herein, we report the ultrastructural organization of the vitelline envelope and the main features of the sperm of A. charrua. Taking together these results also contribute to phylogenetic studies and provide base line data to propose A. charrua as a biomonitor of contamination in a protected area.

Temperature induces gonadal maturation and affects electrophysiological sexual maturity indicators inBrachyhypopomus pinnicaudatusfrom a temperate climate

In contrast to most of the previous studies in gymnotiform reproduction,which have been conducted in the tropical region, this study examines a gymnotid from the temperate region in both the natural habitat and the laboratory. The gonadal histology of Brachyhypopomus pinnicaudatus is described for the first time. The male had a paired, lobular testis of the unrestricted spermatogonial type, and females a paired saccular cystovary. Analysis of gonads and their annual cycle enabled us to confirm the breeding season and to conclude that this species is a multiple spawner. Water temperature and photoperiod showed the expected annual cycles for the region. High temperature and a 14 h:10 h L:D photoperiod in the natural habitat coincided with (1) mature gonadal stages, (2) electrophysiological sexual dimorphism: males present a lengthened negative phase in their electric organ discharge (EOD) and (3) decreased temperature sensitivity of the EOD: the waveform does not change when temperature increases above 20°C. Acclimation to sustained high temperature (30 days, 28°C, 12 h:12 h L:D,low conductivity) induced gonad maturation along with EOD dimorphism. Our data show that high environmental temperature is enough to trigger sexual maturity in Brachyhypopomus pinnicaudatus from a temperate climate.

Tn antigen is a pre-cancerous biomarker in breast tissue and serum in n-nitrosomethylurea-induced rat mammary carcinogenesis

The Tn determinant (GalNAcalpha-O-Ser/Thr), normally a cryptic structure in mucin-type O-glycans, is a tumor-associated marker which has attracted particular interest in cancer biology. We herein report the characterization of N-nitrosomethylurea (NMU)-induced breast cancer in rats as a new model for the study of aberrant O-glycosylation products. Tn-antigen expression is detectable not only in mammary carcinoma induced by NMU but also in carcinogen-initiated mammary epithelium, indicating that Tn could be a pre-cancerous biomarker in rats treated with NMU. Serum Tn levels were followed up longitudinally in 30 rats from the time of the first injection of NMU to the development of advanced breast cancer. Tn antigen increased in serum several weeks before tumor development, and became highly positive after 56 days of carcinogenesis (prior to breast-cancer occurrence), and the levels correlated with Tn expression in mammary tissues. However, during the follow-up after detection of mammary cancer, all animals displayed a significant decrease of serum Tn antigen, and low levels were observed in animals with advanced breast cancer. We have shown that the humoral immune response to cancer, with the production of anti-Tn antibodies, could hamper the detection of Tn antigen in animals with advanced breast cancer. These results suggest that NMU-induced rat mammary carcinogenesis is a useful experimental model to study the regulation of O-glycosylation at the cellular level during malignant transformation.

Molecular detection of cancer cells in bone marrow and peripheral blood of patients with operable breast cancer. Comparison of CK19, MUC1 and CEA using RT-PCR

We have compared three different RT-PCR procedures to measure cytokeratin 19 (CK19), carcinoembryonic antigen (CEA) and mucin MUC1 gene expression in order to determine their diagnostic value in detecting tumour cells in bone marrow aspirates of patients with operable breast cancer. In an experimental model, the best sensitivity was observed for CK19 and MUC1 RT-PCR assays, although only the CEA and CK19 assays showed good specificity. The study of 42 patients showed that a 'CK19 positive/CEA positive' RT-PCR assay in bone marrow correlated positively with a positive axillary lymph node status (N(0) versus N(1-3), P<0.05). Both assays were also positive in 17% of node negative patients. RT-PCR assays were more sensitive in bone marrow than in peripheral blood. Our results suggest that CK19 and CEA RT-PCR assays are powerful methods for detecting disseminated breast cancer cells. A larger study with long-term follow-up is required in order to clarify their clinical usefulness.

Detection of rare human breast cancer cells. Comparison of an immunomagnetic separation method with immunocytochemistry and RT-PCR

BACKGROUND

The detection of occult carcinoma cells in patients with breast cancer may aid determination of prognosis and the development of new therapeutic approaches. In this study, we report a new method to detect rare human breast cancer cells, which combines an immunomagnetic separation (IMS) procedure with cytokeratin 19 (CK 19) immunostaining.

MATERIALS AND METHODS

Four monoclonal antibodies (MAb) previously characterized against cell surface antigens (1BE12, ED8, 7B10 and 83D4), were evaluated for IMS optimization. Immunoseparated epithelial cells were identified using a MAb against CK 19. We compared the IMS procedure with the immunocytochemistry (ICC) and the RT-PCR for CK 19 on an "in vitro" experimental model.

RESULTS

The best results in IMS procedures were obtained using MAbs 1BE12 (directed against Lewis y antigen) and ED8 (directed against MUC 1). In reconstitution experiments, using several ratios of T47D cells mixed with peripheral-blood mononuclear (PBMN) cells, the IMS procedure reliably detects one mammary carcinoma cell in 5 x 10(5) PBMN cells, whereas the ICC detects up to one T47D cell per 10(5) PBMN cells. The best sensitivity was observed with the RT-PCR (up to one T47D cell per 10(6) PBMN cells). We found the same high specificity with the three methods evaluated.

CONCLUSIONS

The IMS procedure using MAbs 1BE12 or ED8 associated with CK 19 immunostaining is a specific, sensitive, and feasible method for the detection of rare human breast cancer cells. This method proved to be better than the ICC staining but its sensitivity was lower than that of RT-PCR for CK 19.

Analysis of a heterogeneous group of human breast carcinoma associated glycoproteins bearing the Tn determinant

The Tn determinant (GalNAc alpha-O-Ser/Thr) is expressed by about 90% of human carcinomas, but is cryptic in most normal human tissues. A murine monoclonal antibody (MAb) 83D4, developed following immunization with human breast carcinoma cells, reacts with a Tn-related epitope. In the present study we characterized the glycoprotein antigen identified by 83D4 in the human breast carcinoma cell line MCF-7. We further showed that the 83D4 antigenic determinant is masked in human milk fat globule membranes (HMFGM), and can be exposed upon mild m-periodate treatment after desialylation. Western-blot analysis resolved the 83D4 antigen from MCF-7 into two main components of 120-190 kD and > 500 kD respectively. Non equilibrium pH gradient electrophoresis/SDS PAGE revealed the acidic nature of the reactive glycoproteins (pI 4.43-4.70). 83D4 antigenic activity resolved by CsCl gradient ultracentrifugation layered on a wide range of densities (1.30-1.46 g/ml) including typical densities of mucin-like glycoproteins but also lower densities. The amino acid composition of the antigen, relatively rich in serine but poor in threonine and proline, confirmed the divergence from other mucin-like carcinoma-associated glycoproteins. Dicarboxylic amino acids were abundant, accounting in part for the acidic nature of the molecules. ELISA and Western-blot analysis of the subcellular fractions from MCF-7 cells revealed that the 83D4 antigen is mainly contained in plasma membranes (85%) from which it may be resolved into two broad bands (slow and fast migrating components). These results provide information on a group of breast carcinoma associated glycoproteins related to but different from typical mucins, and provide data on alteration of O-glycosylation in tumor cells.

[Histology of the ovary of Macrodon ancylodon (Bloch and Schneider, 1801) Teleostei: Sciaenidae). Oogenesis. Post-ovulatory follicles. Atresia]

The reproductive cycle of Teleostean fishes may be studied from different points of view. One of them is to examine the histological changes that take place in the gonad. A histological description of the gonad is to be done first. In this work we have studied the oogenesis, atresia and post-ovulatory follicles of Macrodon ancylodon. Specimens were collected from April 1982 to May 1983 on the coast of Río de la Plata (Montevideo, Uruguay). Material used was preserved in neutralized 10% formalin inbedded in paraffin and paraffin-celloidin, sectioned at 5 - 10 microns and stained with haematoxilin-eosin. Pas-haematoxilin, and specific techniques for lipid detection were used. Six oogenetic stages were recognized: oogonias, and basophilic, lipid yolk vesicles, protein yolk vesicles, matures and ripe hydrated oocytes. Theca and granulosa are negative to lipid and cholesterol histochemic reaction techniques. Post-ovulatory follicles show structural degenerative changes. Two types of atresia are described: hypertrophic and nonhypertrophic, which apparently would not have an endocrine function. It is important to recognize post-ovulatory follicles to establish the spawning pattern and also to recognize atretic follicles due to their incidence in the fecundity of a species.