Biomedical subjects

Gabriela Nica

Publications and source records attributed to Gabriela Nica.

6 recordsLinked to original sources

PubMed2006

Pituitary-interrenal interaction in zebrafish interrenal organ development.

To further elucidate pituitary adrenal interactions during development, we studied the organogenesis of the interrenal organ, the teleost homolog of the mammalian adrenal gland, in zebrafish. To this end we compared wild-type zebrafish interrenal development with that of mutants lacking pituitary cell types including corticotrophs. In addition, we studied the effects of ACTH receptor (Mc2r) knockdown and dexamethasone (dex) on interrenal development and pituitary feedback. Until 2 d post fertilization (2 dpf) interrenal development assessed by transcripts of key steroidogenic genes (cyp11a1, mc2r, star) is independent of proopiomelanocortin (Pomc) as demonstrated in aal/eya1and lia/fgf3 mutants. However, at 5 dpf lack of pituitary cells leads to reduced expression of steroidogenic genes at both the transcriptional and the protein level. Pituitary control of interrenal development resides in corticotrophs, because pit1 mutants lacking pituitary cells except corticotrophs have a phenotype similar to that of wild-type controls. Furthermore, development in mc2r knockdown morphants does not differ from aal/eya1 and lia/fgf3 mutants. Inhibition of steroidogenesis by mc2r knockdown induces up-regulation of pomc expression in the anterior domain of pituitary corticotrophs. Accordingly, dex suppresses pomc in the anterior domain only, leading to impaired expression of steroidogenic genes commencing at 3 dpf and interrenal hypoplasia via reduced interrenal proliferation. In contrast, negative feedback on pituitary corticotrophs by dex is evident at 2 dpf and precedes effects of Pomc on the interrenal primordium. These data demonstrate a gradual transition from early pituitary-independent interrenal organogenesis to developmental control by the anterior domain of pituitary corticotrophs acting via Mc2 receptors.

Animals↗

PubMed2006

Eya1 is required for lineage-specific differentiation, but not for cell survival in the zebrafish adenohypophysis.

The homeodomain transcription factor Six1 and its modulator, the protein phosphatase Eya1, cooperate to promote cell differentiation and survival during mouse organ development. Here, we studied the effects caused by loss of eya1 and six1 function on pituitary development in zebrafish. eya1 and six1 are co-expressed in all adenohypophyseal cells. Nevertheless, eya1 (aal, dog) mutants show lineage-specific defects, defining corticotropes, melanotropes, and gonadotropes as an Eya1-dependent lineage, which is complementary to the Pit1 lineage. Furthermore, eya1 is required for maintenance of pit1 expression, leading to subsequent loss of cognate hormone gene expression in thyrotropes and somatotropes of mutant embryos, whereas prolactin expression in lactotropes persists. In contrast to other organs, adenohypophyseal cells of eya1 mutants do not become apoptotic, and the adenohypophysis remains at rather normal size. Also, cells do not trans-differentiate, as in the case of pit1 mutants, but display morphological features characteristic for nonsecretory cells. Some of the adenohypophyseal defects of eya1 mutants are moderately enhanced in combination with antisense-mediated loss of Six1 function, which per se does not affect pituitary cell differentiation. In conclusion, this is the first report of an essential role of Eya1 during pituitary development in vertebrates. Eya1 is required for lineage-specific differentiation of adenohypophyseal cells, but not for their survival, thereby uncoupling the differentiation-promoting and anti-apoptotic effects of Eya proteins seen in other tissues.

Amino Acid Sequence↗

PubMed2005

Expression of the somatolactin beta gene during zebrafish embryonic development.

Somatolactin (Sl) is a pituitary hormone closely related to prolactin (Prl) and growth hormone that was until now only found in various fish species. We isolated the cDNA coding for zebrafish Slbeta and we identified the gene encoding this hormone. We also obtained a 1kb genomic fragment corresponding to the slbeta upstream promoter region. Furthermore, the slbeta expression pattern was examined during zebrafish embryogenesis using whole-mount in situ hybridization. Slbeta mRNA is first detected in a single cell at the anterior border of the neural plate starting at 23h post fertilization (hpf). Slbeta-expressing cells also express the transcription factor pit1 and are located close to prl-expressing cells. Using combined fluorescent in situ hybridization, we show that slbeta- and prl-expressing cells are clearly distinct at 29 hpf. Starting at 30 hpf, the number of slbeta positive cells increases and their location becomes more clearly distinct from lactotrope cells, in a more posterior position. At later stages (48 hpf), slbeta expression was observed posterior to growth hormone expression, again in a distinct cell type. We show that zebrafish mutants aal, as well as mutants in the pit1 gene, are deficient in slbeta expression. In conclusion, slbeta expression defines a new, additional cell type in zebrafish pituitary that depends on pit1 and aal for its differentiation.

Animals↗

PubMed2005

Differentiation of the vertebrate retina is coordinated by an FGF signaling center.

In vertebrates, midline-derived sonic hedgehog and nodal are crucial for the initial proximal-distal patterning of the eye. The establishment of the distal optic stalk is in turn a prerequisite to initiate retinogenesis. However, the signal that activates this process is unknown. Here, we demonstrate that in both chick and fish, the initiation of retinal differentiation is triggered by a species-specific localized Fgf signaling center that acts as mediator of the midline signals. The concerted activity of Fgf8 and Fgf3 is both necessary and sufficient to coordinate retinal differentiation independent of the connecting optic stalk.

Animals↗

PubMed2004

Zebrafish pit1 mutants lack three pituitary cell types and develop severe dwarfism.

The Pou domain transcription factor Pit-1 is required for lineage determination and cellular commitment processes during mammalian adenohypophysis development. Here we report the cloning and mutational analysis of a pit1 homolog from zebrafish. Compared with mouse, zebrafish pit1 starts to be expressed at a much earlier stage of adenohypophysis development. However, as in the mouse, expression is restricted to a subset of pituitary cell types, excluding proopiomelanocortin (pomc)-expressing cells (corticotropes, melanotropes) and possibly gonadotropes. We could identify two N-ethyl-N-nitrosourea-induced zebrafish pit1 null mutants. Most mutants die during larval stages, whereas survivors develop severe dwarfism. Mutant larvae lack lactotropes, somatotropes, and thyrotropes, although the adenohypophysis is of normal size, without any sign of increased apoptosis rates. Instead, mutant embryos initiate ectopic expression of pomc in pit1-positive cells, leading to an expansion of the Pomc lineage. Similarly, the number of gonadotropes seems increased, as indicated by the expression of gsualpha, a marker for thyrotropes and gonadotropes. In pit1 mutants, the total number of gsualpha-positive cells is normal despite the loss of gsualpha and tshbeta coexpressing cells. Together, these data suggest a transfating of the Pit1 lineage to the Pomc and possibly the gonadotroph lineages in the mutant, and a pomc- and gonadotropin-repressive role of Pit1 during normal zebrafish development. This is different from mouse, for which a repressive role of Pit-1 has only been reported for the gonadotropin Lhbeta, but not for Pomc. In sum, our data point to both conserved and class-specific aspects of Pit1 function during pituitary development in different vertebrate species.

Animals↗

PubMed2003

Calgizarrin like gene (Cal) deficient mice undergo normal spermatogenesis.

The murine calgizzarin like gene (Cal) encodes for a calcium binding protein, which belongs to the S100 family of EF-hand proteins. It is specifically expressed in Sertoli cells in the testis and its expression is down-regulated by unknown factor(s) from spermatocytes/spermatids. In this paper, we show by transfection of a fusion protein of green fluorescent protein and Cal protein into NIH3T3 cells, that the expression of Cal is restricted only in the cytoplasm of the cell. A differentially regulated cytoplasmic expression of the Cal in Sertoli cells during mouse development suggests that Cal might play an important role during spermatogenesis. In order to elucidate the function of the Cal protein in the spermatogenesis, we disrupted the Cal locus in mouse by homologous recombination. In our knockout mouse, we deleted exon 2 and exon 3 of the Cal gene and replaced them with a neomycin cassette, which resulted in a complete loss of the Cal transcript. Male and female Cal4+/- and Cal4-/- mice from genetic backgrounds C57BL/6J x 129X1/SvJ hybrid and 129X1/SvJ inbred exhibited normal phenotype and were fertile. An intensive phenotypic analysis showed no gross abnormalities in testis morphology. The lack of the Cal protein also does not affect the parameters of sperm, as they are able to fertilize the oocytes in a competent manner, which is comparable to wild-type sperm. Collectively our results demonstrate that Cal is a nonessential protein and it does not play an important role in mouse spermatogenesis or in process of fertilization.

Animals↗