Effets de l'administration d'HSP90 sur la migration des cellules germinales :une étude dans les gonades de l'embryon de poulet

Introduction: Primordial Germ Cells (PGCs) differentiate into spermatozoa or oocytes. They appear early during embryonic development before migrating to the gonadal ridges. Because of their long migration, PGCs have been proposed as a valuable model to study long distance cell migration. Some species also present a vascular phase in the migration of the germline and could therefore be compared to metastatic migration. HSP90 is a heat shock protein involved in the stabilization of several client-proteins, including oncoproteins. HSP90 inhibition has been proved to decrease PGCs migration in mouse and zebrafish. Material and methods: We investigated the effect of geldanamycin on PGCs migration in a species with a vascular phase, the chicken. Geldanamycin was injected in the egg at 48 h of incubation, PGC's were detected in blood using of blood smears, and in the embryo by immunohistochemistry using anti-HSP90 antibody. Results: The effects of the treatment were similar to those observed in mouse and zebrafish. We show the presence of ectopic germs cells in the vasculature and in the dorsal mesentery, and some deformities of the gonads. Conclusion: Inhibition of HSP90 decreases the migration of PGCs and proposed the migration of PGCs in the chick embryo as an interesting model to study metastatic invasion.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Hox-A2 protein expression in mouse embryo middle ear ossicles

The origin of the mammalian middle ear ossicles from mandibular and hyoid pharyngeal arches remains controversial and discussed. Two adverse theories are proposed. The first claims that malleus and incus derive from the Meckel's cartilage of the mandibular arch, and stapes from Reichert's cartilage of the hyoid arch. The second postulates that handle of malleus and long process of the incus are derived from the second arch as well as the stapes. Contradictory analyses support alternatively each theory without any experimental evidence. In order to bring new data, we analyzed by immunohistochemistry the expression of Hox-A2 protein in ossicular anlagen in E11 to 13 mouse embryos. HOXA2 gene is known to be expressed in second arch cells and to be absent from mandibular arch derivatives. Surprisingly, Hox-A2 protein was present in all ossicular primordia, as well in Reichert's cartilage. Meckel's cartilage was free of staining. Unlabeled cells were also present in ossicular blastemata. These results suggest that ossicular condensations could arise from mixed cell populations originated in both mandibular and hyoid pharyngeal arches. However, we cannot exclude that diffuse Hox-A2 immunoreactivity could correspond to a secondary expression in craniofacial mesenchyme independently from the branchial origin of cells.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Chronologie révisée de la migration des cellules germinales primordiales chez l'embryon de poulet

Introduction: Primordial Germ Cells (PGCs) are present in all sexually reproducing animals. They differentiate into spermatozoa or oocytes and are therefore responsible for the transmission of genetic and epigenetic information across generations. In birds, PGCs are first observed in the center of the blastodisc at stage Eyal-Giladi X. With the formation of the primitive streak, germ cells are translocated anteriorly to the germinal crescent. At stage Hamburger- Hamilton 10–12, they enter the vasculature before migrating through the dorsal mesentery towards the genital ridges. Material and methods: Embryos from stages Hamburger-Hamilton (HH) 16 to 22 were collected. Blood samples were taken from the dorsal aorta and from the heart in order to perform blood smears and PAS staining. Embryos were dissected and fixed in Serra's medium. Sections were placed on slides for PAS staining. A sample of each embryo was collected for DNA extraction and PCR in order to determine the sex of the embryos. Results: PGCs were observed in blood circulation until stage HH 20 on blood smears and until stage HH 19 on histological sections. The first PGCs arrived in the genital ridges were observed from stage HH 17. A few germ cells were still migrating in the dorsal mesentery at stage HH 22. The aim of this study was to review the chronology of the migration of PGCs in chick embryos.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Vasa est-il un marqueur si spécifique des cellules germinales primordiales ?Une comparaison de l'expression des protéines VASA et HSP90 chez le jeune embryon de poulet

Introduction: Primordial germ cells (PGCs) have been studied since the 19th century with several different methods. The earliest works were based on the morphological criteria of these cells associated or not with a particular staining. Different markers have been proposed in immunohistochemistry among which we can quote the Stage-specific embryonic antigene-1 (SSEA-1), the embryonic mouse antigen-1 (EMA-1) or the heat shock protein 90. Unfortunately, none of them are germline specific. The VASA protein is considered as one of the most reliable marker for PGCs by some authors with its expression being considered to limited to the germ cells. However, other studies have reported its expression in somatic cells. Here, we described the expression of the heat shock protein, HSP90, and the VASA protein in the early chick embryo. Material and methods: Embryos from stages Hamburger-Hamilton (HH) 19, 21 and 28 were collected. Embryos were dissected and fixed in Serra's medium. Sections were placed on slides for PAS staining and for double immunohistochemistry with HSP90 and VASA. Results: VASA and HSP90 expression have been observed in germ cells but as well in other cell lineages with a spatio-temporal gradient in respect to the characteristics of development of each organ. The conclusion is that VASA expression is not limited to the germ line in chick embryo.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Geldanamycin administration reduces the amount of primordial germ cells in the mouse embryo.

Heat shock proteins (HSPs) are expressed or overexpressed in response to exposure to stress. They act as molecular chaperones, ensuring the correct folding of numerous client proteins. HSP90 is one of the most conserved HSPs. Its role extends beyond stress tolerance. HSP90 also contributes to development, differenciation, apoptosis and oncogenesis. Numerous tumors are associated with an overexpression of HSP90 and this expression can be used to evaluate its metastatic capacity. Primordial germ cells (PGCs) exhibit HSP90 expression under normal conditions. PGCs arise early in development and migrate by a combination of passive and active movements towards the gonads. The aim of this work was to study the impact of an inhibition of HSP90 on the migration of the PGCs. Geldanamycin, a well established HSP90 inhibitor with potent antitumor properties was used to achieve this inhibition.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Expression of Wnt and ββ ββ β-Catenin in Mouse Tooth Germs and Chick Facial Primordia: A Comparison

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Evolution and development of parrot pseudoteeth

Parrot embryos carry peculiar appendages at their developing beak that have been described as pseudoteeth. To better characterize the pattern of development responsible for the emergence of these dental appendages, we examined parrot embryos combining conventional histology and microtomography approaches. Using immunohistochemistry, we observed the epithelial and mesenchymal expression of several proteins involved in tooth development in mammals. Parrot pseudoteeth arose by epithelial and mesenchymal evagination, and their early development was similar to the ontogeny of scales and feathers. There was no enamel tissue, and the evaginations were surrounded by the rhamphotheca. In adults, the rhamphotheca covers entirely the appendages, now represented by bone evaginations, which were more numerous in the lower than in the upper beak, being similar to the osseous teeth of the fossil Pelagornithidae. These embryonic pseudoteeth resembled reptile's first-generation teeth and dental appendages of chicken talpid2mutants. Proteins involved in mammalian odontogenesis, such as SHH, BMP4, PITX2, and PAX9, were found to be generally expressed in beak epithelium and mesenchyme during parrot pseudoteeth development, with clusters of high-level expression in the pseudoteeth rudiments. This suggests that a similar, highly conserved gene expression program gives rise to the appearance of odontode derivatives in numerous species, despite their divergent developmental paths. These results provide new insights into the development and evolution of odontode-derived structures in vertebrates.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Caspase-2 immunohistochemistry in differentiating cells during mouse cephalic development

Caspases are proteases primarily involved in the process of apoptosis; however, caspases can exert non-apoptotic functions. The purpose of this work was to use immunohistochemistry to analyse the expression sites of caspase-2 during normal mouse cephalic development and in embryos exposed to irradiation. Control embryos from embryonic day 9 (E9) to E17 were analysed, and E9 and 10 irradiated embryos were removed and observed after administration of 2 Gy irradiation at embryonic day 9. Surprisingly, not only apoptotic cells expressed caspase-2. In addition, numerous cell populations in normal and experimental embryos displayed transient but intense caspase-2 immunoreactivity, with nuclear and cytoplasmic localisation. This immunoreactivity was not observed with caspase-3 and -9 antibodies. Cranial neural crest cells, premuscular blastemata, cartilage, teeth, the heart, the eye and some other structures displayed caspase-2 expression, with progressive changes during embryonic development. These changing patterns evoke progressive waves of cell differentiation in specific cell populations. Little is known regarding the nonapoptotic functions of caspase-2. Despite the difficulty in understanding the role of this protease during cell differentiation, the fact that caspase-2 is known to prevent DNA damage and to protect the cell cycle could be closely associated with our observations, which point to the need for further research, particularly in caspase-2 knockout mice.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Mise en évidence de la phosphatase alcaline par immunohistochimie chez l’embryon de souris: résultats et interprétation méthodologique

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L'administration de geldanamycine réduit le nombre de gonocytes exprimant l'HSP86 chez l'embryon de souris: premiers résultats.

5 mg of Geldanamycin, an inhibitor of stress protein HSP86 which express on mammalian germ cells, were administered to E8 pregnant mice. E17 embryos were removed, and a quantitative analysis of HSP90-immunoreactive cells in the gonad was performed, in comparison to control embryos. First, we observed that the number of germ cells is lower in male than in female embryos, as well in control and experimental embryos. External features of experimental and control embryos did not display any difference. Embryos exposed to geldanamycin exhibit a significant decrease of immunoreactive germ cells. In two embryos, we observed a group of ectopic immunoreactive cells in the pelvic area. We conclude that geldanamycin inhibits germ cells migration, and suggest that this inhibition can lead to ectopic germ cell populations, similar to teratomas.English AbstractJournal Articleinfo:eu-repo/semantics/publishe