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13-P130 Expression of Dscam and Sidekick proteins at the developing mouse optic chiasm
S234
MECHANISMS OF DEVELOPMENT
1 2 6 (2 0 0 9) S1 9 5–S 23 8
tions resulted in severe axis abnormalities, i.e., shortened trunk
crest migration, and neuronal differentiation. A complex network
with small or missing tail, and severely reduced head and eyes.
of factors including Krox20, Kriesler and Hox family members
This phenotype can be rescued by co-injection of the MO+ lin-
and signal molecules such as FGFs and Retinoic Acid governs
28mRNA. Lin28 MO-mediated knockdown blocks the typical elon-
the formation and A/P specification of the rhombomeres.
gation of animal cap explants treated with FGF. The expression of
The transcription factor Pax6 is a highly conserved regulator
early mesodermal markers such as brachyury and chordin is also
which plays key roles in the development of the eye, pancreas
reduced, indicating a role for lin-28 proteins in mesoderm
and nervous system. However, the knowledge regarding Pax6 role
patterning.
in the hindbrain is very limited. The aim of this study is to investigate the role of Pax6 in the early hindbrain development.
doi:10.1016/j.mod.2009.06.602
First we showed that the A/P expression pattern of Pax6 in the hindbrain is very dynamic; first expressed in r3, then in r5 and only later in the other rhombomeres. Second, we found that Pax6 expression in rhombomeres is downregulated by the inhibi-
13-P130
tion of FGF signaling suggesting the involvement of FGFs in the
Expression of Dscam and Sidekick proteins at the developing
regulation of Pax6 expression. Moreover, Krox20 negatively regu-
mouse optic chiasm
lates Pax6 expression in rhombomeres 3, 5. Third, experiments of
Freyja Bruce1, Peter Fuerst2, Robert Burgess2, Lynda Erskine1
gain-and-loss of function of Pax6 demonstrated its role in hind-
1
University of Aberdeen, Aberdeen, United Kingdom
brain patterning by the regulation of Krox20, Kriesler, EphA4
2
The Jackson Laboratory, Maine, United States
and various Hox’s gene expression, which are essential for the establishment of regional identities along the hindbrain. Taken
The optic chiasm is an important midline choice point where retinal ganglion cell (RGC) axons from each eye diverge to targets on both sides of the brain, setting up binocular vision. While several cues essential for guidance at the optic chiasm have been
together, our results show for the first time expression regulation and activity of Pax6 in rhombomeres, suggesting a central role of Pax6 in early hindbrain patterning. doi:10.1016/j.mod.2009.06.604
identified, it is clear other signals are required. We have begun to investigate the role of the highly related homophilic cell adhesion molecules, Down’s syndrome cell adhesion molecule (Dscam), Dscam Like1 (DscamL1), Sidekick1 (Sdk1) and Sidekick2 (Sdk2) in directing RGC axon guidance. Dscam is a
13-P132
key regulator of midline axon guidance in Drosophila and all 4 pro-
Sonic Hedgehog is essential in lung branching morphogenesis
teins are essential for the normal wiring of the vertebrate retina.
Gi-Hee Park, Hyuk-Jae Kwon, Han-Sung Jung, Sung-Won Cho
Using in situ hybridisation we have examined the expression
Yonsei University College of Dentistry, Seoul, Republic of Korea
patterns of these genes in E12.5–E17.5 mouse embryos, the period when the optic chiasm is developing. At all ages Dscam and Sdk1 are expressed strongly in the RGC layer of the retina whereas Sdk2 is more widely distributed throughout the retina. Dscam and Sdk2 also are expressed in the region of the developing optic chiasm. Expression of Dscam borders the optic pathway whereas Sdk2 is expressed by the glia of the optic nerve and midline. The significance of these expression patterns is being investigated in vivo and in vitro. Work with Dscam KO mice shows that there are no obvious defects in RGC axon path-finding in embryos lacking the Dscam protein, however, there is evidence suggesting it may play a role in controlling RGC number and retinal organisation. doi:10.1016/j.mod.2009.06.603
During early respiratory system development, the foregut endoderm gives rise to the tracheal and lung cell progenitors. In mice, lung primordial buds form at E9.5. From E10.5 to E17.0, the lung epithelium undergoes branching morphogenesis to form the respiratory (or bronchial) tree. Branching morphogenesis of the embryonic lung requires interaction between the epithelium and the mesenchyme. The Hedgehog signaling pathway plays a important role in the development of many organs. Shh acts as an epithelial signal, so in the lung Shh is expressed in lung epithelium with highest level in the terminal bud. FGF and BMP family genes also important roles during the lung branching morphogenesis. To investigate the role of SHH during the lung branching morphogenesis, We injected 5E1 (anti-SHH antibody) in the pregnant
13-P131 Pax6 is involved in the early hindbrain patterning in the chick embryo Galya Kayam, Dalit Sela-Donenfeld The Hebrew University, Rehovot, Israel
mice at the concentration of 500 lg/50 g and we also cultured lung at the stage of E11 in the media included with 5E1 (130 lg/ml). To analysis the cross-talk between genes, we did microarray and in situ hybridization with many target genes such as Fgf10, Fgfr2b, Ptch and Bmp4. In the 5E1-treated groups lung size was much smaller and their branching patterns are less complicated compare to the
During formation of the vertebrate central nervous system, the hindbrain is organized into segmental units, called rhombomeres. The rhombomeres are lineage-restricted compartments which underlie segmental patterns of gene expression, neural
control group. Furthermore, the expression level of many genes in FGF and BMP pathway was different between two groups. These results indicate SHH is required for lung branching morphogenesis by regulating many genes in FGF and BMP pathway.
MECHANISMS OF DEVELOPMENT
1 2 6 (2 0 0 9) S1 9 5–S 23 8
tions resulted in severe axis abnormalities, i.e., shortened trunk
crest migration, and neuronal differentiation. A complex network
with small or missing tail, and severely reduced head and eyes.
of factors including Krox20, Kriesler and Hox family members
This phenotype can be rescued by co-injection of the MO+ lin-
and signal molecules such as FGFs and Retinoic Acid governs
28mRNA. Lin28 MO-mediated knockdown blocks the typical elon-
the formation and A/P specification of the rhombomeres.
gation of animal cap explants treated with FGF. The expression of
The transcription factor Pax6 is a highly conserved regulator
early mesodermal markers such as brachyury and chordin is also
which plays key roles in the development of the eye, pancreas
reduced, indicating a role for lin-28 proteins in mesoderm
and nervous system. However, the knowledge regarding Pax6 role
patterning.
in the hindbrain is very limited. The aim of this study is to investigate the role of Pax6 in the early hindbrain development.
doi:10.1016/j.mod.2009.06.602
First we showed that the A/P expression pattern of Pax6 in the hindbrain is very dynamic; first expressed in r3, then in r5 and only later in the other rhombomeres. Second, we found that Pax6 expression in rhombomeres is downregulated by the inhibi-
13-P130
tion of FGF signaling suggesting the involvement of FGFs in the
Expression of Dscam and Sidekick proteins at the developing
regulation of Pax6 expression. Moreover, Krox20 negatively regu-
mouse optic chiasm
lates Pax6 expression in rhombomeres 3, 5. Third, experiments of
Freyja Bruce1, Peter Fuerst2, Robert Burgess2, Lynda Erskine1
gain-and-loss of function of Pax6 demonstrated its role in hind-
1
University of Aberdeen, Aberdeen, United Kingdom
brain patterning by the regulation of Krox20, Kriesler, EphA4
2
The Jackson Laboratory, Maine, United States
and various Hox’s gene expression, which are essential for the establishment of regional identities along the hindbrain. Taken
The optic chiasm is an important midline choice point where retinal ganglion cell (RGC) axons from each eye diverge to targets on both sides of the brain, setting up binocular vision. While several cues essential for guidance at the optic chiasm have been
together, our results show for the first time expression regulation and activity of Pax6 in rhombomeres, suggesting a central role of Pax6 in early hindbrain patterning. doi:10.1016/j.mod.2009.06.604
identified, it is clear other signals are required. We have begun to investigate the role of the highly related homophilic cell adhesion molecules, Down’s syndrome cell adhesion molecule (Dscam), Dscam Like1 (DscamL1), Sidekick1 (Sdk1) and Sidekick2 (Sdk2) in directing RGC axon guidance. Dscam is a
13-P132
key regulator of midline axon guidance in Drosophila and all 4 pro-
Sonic Hedgehog is essential in lung branching morphogenesis
teins are essential for the normal wiring of the vertebrate retina.
Gi-Hee Park, Hyuk-Jae Kwon, Han-Sung Jung, Sung-Won Cho
Using in situ hybridisation we have examined the expression
Yonsei University College of Dentistry, Seoul, Republic of Korea
patterns of these genes in E12.5–E17.5 mouse embryos, the period when the optic chiasm is developing. At all ages Dscam and Sdk1 are expressed strongly in the RGC layer of the retina whereas Sdk2 is more widely distributed throughout the retina. Dscam and Sdk2 also are expressed in the region of the developing optic chiasm. Expression of Dscam borders the optic pathway whereas Sdk2 is expressed by the glia of the optic nerve and midline. The significance of these expression patterns is being investigated in vivo and in vitro. Work with Dscam KO mice shows that there are no obvious defects in RGC axon path-finding in embryos lacking the Dscam protein, however, there is evidence suggesting it may play a role in controlling RGC number and retinal organisation. doi:10.1016/j.mod.2009.06.603
During early respiratory system development, the foregut endoderm gives rise to the tracheal and lung cell progenitors. In mice, lung primordial buds form at E9.5. From E10.5 to E17.0, the lung epithelium undergoes branching morphogenesis to form the respiratory (or bronchial) tree. Branching morphogenesis of the embryonic lung requires interaction between the epithelium and the mesenchyme. The Hedgehog signaling pathway plays a important role in the development of many organs. Shh acts as an epithelial signal, so in the lung Shh is expressed in lung epithelium with highest level in the terminal bud. FGF and BMP family genes also important roles during the lung branching morphogenesis. To investigate the role of SHH during the lung branching morphogenesis, We injected 5E1 (anti-SHH antibody) in the pregnant
13-P131 Pax6 is involved in the early hindbrain patterning in the chick embryo Galya Kayam, Dalit Sela-Donenfeld The Hebrew University, Rehovot, Israel
mice at the concentration of 500 lg/50 g and we also cultured lung at the stage of E11 in the media included with 5E1 (130 lg/ml). To analysis the cross-talk between genes, we did microarray and in situ hybridization with many target genes such as Fgf10, Fgfr2b, Ptch and Bmp4. In the 5E1-treated groups lung size was much smaller and their branching patterns are less complicated compare to the
During formation of the vertebrate central nervous system, the hindbrain is organized into segmental units, called rhombomeres. The rhombomeres are lineage-restricted compartments which underlie segmental patterns of gene expression, neural
control group. Furthermore, the expression level of many genes in FGF and BMP pathway was different between two groups. These results indicate SHH is required for lung branching morphogenesis by regulating many genes in FGF and BMP pathway.