Biomedical subjects

Regina Teo

Publications and source records attributed to Regina Teo.

3 recordsLinked to original sources

PubMed2005

An evolutionary conserved role of Wnt signaling in stem cell fate decision.

Wnt/Frizzled/ss-catenin-based signaling systems play diverse roles in metazoan development, being involved not only in the establishment of body axes in embryogenesis but also in regulating stem cell fate in mammalian post-embryonic development. We have studied the role the canonical Wnt cascade plays in stem cell fate determination in Hydractinia, a member of the ancient metazoan phylum Cnidaria, by analyzing two key molecules in this pathway, frizzled and ss-catenin, and blocking GSK-3. Generally, frizzled was expressed in cells able to divide but absent in post-mitotic, terminally differentiated cells such as nerve cells and nematocytes. Transcripts of frizzled were identified in all embryonic stages beginning with maternal transcripts in the oocyte. Following gastrulation and in the planula larva, frizzled expression concentrated in the central endodermal mass from which the first interstitial stem cells and their derivatives arise. In post-metamorphic development, high levels of frizzled transcripts were detected in interstitial stem cells. Activating downstream events of the Wnt-cascade in the post-metamorphic life phase by blocking GSK-3 with paullones induced recruitment of nematocytes and nerve cells from the pool of interstitial stem cells. Terminal differentiation was preceded by an initial burst of proliferation of frizzled-positive i-cells. In activated i-cells, ss-catenin appeared in the cytoplasm, later in the nucleus. It was subsequently again observed in the cytoplasm and eventually faded out during terminal differentiation. Our results suggest an ancient role of Wnt signaling in stem cell fate determination.

Adenine↗

PubMed2004

Totipotent migratory stem cells in a hydroid.

Hydroids, members of the most ancient eumetazoan phylum, the Cnidaria, harbor multipotent, migratory stem cells lodged in interstitial spaces of epithelial cells and are therefore referred to as interstitial cells or i-cells. According to traditional understanding, based on studies in Hydra, these i-cells give rise to several cell types such as stinging cells, nerve cells, and germ cells, but not to ectodermal and endodermal epithelial cells; these are considered to constitute separate cell lineages. We show here that, in Hydractinia, the developmental potential of these migratory stem cells is wider than previously anticipated. We eliminated the i-cells from subcloned wild-type animals and subsequently introduced i-cells from mutant clones and vice versa. The mutant donors and the wild-type recipients differed in their sex, growth pattern, and morphology. With time, the recipient underwent a complete conversion into the phenotype and genotype of the donor. Thus, under these experimental conditions the interstitial stem cells of Hydractinia exhibit totipotency.

Animals↗

PubMed2004

Patterning a multi-headed mutant in Hydractinia: enhancement of head formation and its phenotypic normalization.

In a mutant strain of Hydractinia (Cnidaria: Hydrozoa), the polyps develop ectopic supernumerary tentacles and heads (hypostomes) after an initial phase of wild-type growth. In order to elucidate the molecular mechanisms implicated in the development of aberrant phenotypes, we tried to enhance or suppress the expressivity of this hypomorphic mutation by exposing subclones to factors supposedly influencing pattern formation. Upon iterated treatment with alsterpaullone, an inhibitor of GSK-3, the formation of additional, ectopic head structures and the budding of new polyps were dramatically accelerated and enhanced. The endogenous stolon-inducing factor (SIF) had opposite effects by reducing head forming potential while increasing stolon-forming potential. SIF could be used to rescue extremely aberrant phenotypes. In these mutant colonies, long polyps with multiple heads eventually detach from stolons and lose the ability to regenerate stolons. Upon exposure to SIF, such free-floating multi-headed polyps resumed production of stolons and acquired wild-type morphology. We conclude that a canonical WNT signaling cascade is involved in patterning the body axis of polyps and in the initiation of budding, and that SIF counteracts this signaling system.

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