Abstracts - Society for Developmental Biology

71
cranial neural crest cells, as they differentiate readily in culture to form clusters of collagen I-positive cells. Other types of
neural crest derivates (neurons, melanocytes) are not observed. These data support our hypothesis that the plastron of the
turtle is formed by a late emerging population of neural crest cells that collect dorsally in the carapace, migrate ventrally to
the plastron, and undergo intramembranous ossification.
Program/Abstract # 216
Raising the shield: the origin and loss of periodic patterning in the turtle shell
Moustakas, Jacqueline, University of Helsinki, Helsinki, Finland; Cebra-Thomas, Judith (Millersville University,
Millersville, United States); Mitchell, Katherine (Swarthmore College, Swarthmore, United States); Jernvall, Jukka
(University of Helsinki, Helsinki, Finland); Gilbert, Scott F. (Swarthmore College, Swarthmore, United States)
The developmental mechanisms responsible for the formation of the turtle shell remain one of the great mysteries in
evolutionary biology. The keratinous scutes of the turtle shell are novel epidermal structures, the patterns of which are
diagnostic of different taxa. Looking at paracrine factors and their inhibitors, we show that scutes develop from placodal
signaling centers that originate in a manner significantly distinct from those of other reptilian and avian ectodermal
appendages. Inhibiting Shh and BMP signaling experimentally results in the loss of these signaling centers and scutes.
Furthermore, we show that the scuteless soft-shelled turtle lacks these placodal signaling centers. We propose that these
signaling centers represent a novel mechanism to develop ectodermal appendages and that the regulation of these centers
have allowed for the diversification of turtle shell function.
Program/Abstract # 217
Determining the role of maternal IRF6 in extra-embryonic development
Smith, Arianna; Klavanian, Jeannie; Siegersma, Kendra; Schutte, Brian, Michigan State University, East Lansing, United
States
Defects in trophectoderm differentiation and placental development are associated with a number of common pregnancy
complications, including spontaneous abortion, preterm birth and preeclampsia. In mammals, the cell types that compose
the placenta are derived from the trophectoderm. Interferon regulatory factor 6 (Irf6), a member of the interferon
regulatory factor family of transcription factors, is maternally expressed in zebrafish and Xenopus. Genetic studies in
zebrafish and Xenopus suggest a conserved role for maternal Irf6 in development of primary superficial epithelium (PSE).
Inhibition of maternal Irf6 using a putative dominant negative Irf6-DNA binding domain results in embryonic lethality due
to improper differentiation of the PSE. The PSE can be likened to the trophectoderm as they are both simple, monolayer
epithelium that encompass the developing embryo. We hypothesize that maternal Irf6 is expressed in murine oocytes, and
that it is necessary for proper differentiation of the trophectoderm in mice. To determine the presence of maternal Irf6 in
oocytes, cross-sections of ovaries collected from wildtype female mice were immuno-stained with an antibody against Irf6.
To determine the function of maternal Irf6 in trophectoderm differentiation, conditional gene knock-out was used.
Specifically, a conditional Irf6 allele along with an oocyte-specific Cre recombinase was used to delete Irf6 in oocytes.
Ovaries collected from females with oocyte-specific deletion of Irf6 were sectioned and stained with hematoxylin and
eosin to assess morphological abnormalities in oocyte development. We observed that Irf6 was highly expressed in murine
oocytes. Irf6 expression could be detected in the ooplasm of developing oocytes. Irf6 was also expressed in the granulosa
cells surrounding the oocyte. Female mice with oocyte specific deletion of Irf6 are born at Mendelian ratios. Preliminary
experiments show no morphological abnormalities in oocytes from mice with oocyte-specific deletion of Irf6 suggesting
that maternal Irf6 is not required for oocyte development. The role of Irf6 of trophectoderm has yet to be determined. The
expression data and conserved role for maternal Irf6 in zebrafish and Xenopus suggest that maternal Irf6 has a role in the
differentiation of trophectoderm. The findings of this research will provide a novel role for Irf6 in development of extraembryonic
tissue. This is research has clinical relevance because 30% of the population carries a DNA variant that alters
IRF6 expression.
Program/Abstract # 218
Is TMED2 essential in the chorion for normal interaction between the allantois and the chorion in mice?
Hou, Wenyang (Dominic), McGill University Human Genetics, Montreal, United States; Sarikaya, Didem (Cambridge,
MA, United States)
During vesicular transport between the endoplasmic reticulum and the Golgi, members of the transmembrane emp24
domain (TMED) protein family form hetero-oligomeric complexes that facilitate protein cargo transportation and
secretion. In our laboratory, we are studying the function of one member of the TMED protein family, TMED2, in mouse
placental labyrinth development. Formation of the mouse labyrinth layer requires proper interactions between two
extraembryonic tissues, the allantois and the chorion; and is essential for nutrition, waste, as well as hormone exchange