For morphogenesis, we need cell migration and guidance and during migration, cell directionality and movement will be induced by guidance molecules through a complex intracellular mechanism. Correct navigation occurs when cells exhibit these guidance molecules properly and when these signals are properly interpreted by the receiving cells. For anomal cellular growth and differentiation we need Hedgehog (Hh) signaling pathway. The Hedgehog (Hh) signaling pathway involves cell proliferation, patterning, axonal guidance, and angiogenesis in sequential manner. Hh Signaling in Tracheal Cell Migration In Drosophila, the tracheal system is a branched epithelial tubular network and its main role is delivering oxygen and this system arises from the tracheal placodes The tracheal placodes are clusters of ectodermal cells which will differentiate at each side of 10 of the embryonic segments called T2 to A8. During this process the cells of each cluster will try to invaginate and migrate into a complex array in a stereotypic pattern, so that it can form the network of multicellular tubes. During migratory process, tracheal cells will not undergo division but remain polarized along the apical-basal axis. the Fibroblast Growth Factor (FGF) homologue Branchless (Bnl) [32] are the main chemoattractant. By activating the FGF receptor (FGFR) Breathless (Btl) on tracheal tip-cells, we can achieve the Bnl chemoattraction and bnl will determine the both the earliest branching events and the later programs of tracheal gene expression and like this high numbers of tracheal cells migrates towards CNS when expression occurs. Like this excess of bnl expression will result in extra tracheal migration and branching. If the cell is a hh mutant it will have severe tracheal defect in embryonic stage and the tracheal tree is stalled and cells remain at the placode region. By shoeing direct effect in the extension of the terminal cells of the dorsal branch, the Hh will bring tracheal cell migration and the Hh signaling pathway known to regulates bnl expression via Stripe (Sr) (it’s a transcription factor with homology to the (EGR). IN the figure they showed how Hh participate in tracheal cell migration. It’s a schematic representation of one tracheal placode at stage 13; Here you can see the tip or each branch is expressing the Bnl and it is spread to the surrounding tissues and provides a chemoattractive signal. In C we can see how Hh signaling induces in the cells surrounding the tracheal tip cells,the expression of Bnl in the cells surrounding the tracheal tip cells. Solution For morphogenesis, we need cell migration and guidance and during migration, cell directionality and movement will be induced by guidance molecules through a complex intracellular mechanism. Correct navigation occurs when cells exhibit these guidance molecules properly and when these signals are properly interpreted by the receiving cells. For anomal cellular growth and differentiation we need Hedgeh.

1. For morphogenesis, we need cell migration and guidance and during migration, cell
directionality and movement will be induced by guidance molecules through a complex
intracellular mechanism.
Correct navigation occurs when cells exhibit these guidance molecules properly and when these
signals are properly interpreted by the receiving cells.
For anomal cellular growth and differentiation we need Hedgehog (Hh) signaling pathway.
The Hedgehog (Hh) signaling pathway involves cell proliferation, patterning, axonal guidance,
and angiogenesis in sequential manner.
Hh Signaling in Tracheal Cell Migration
In Drosophila, the tracheal system is a branched epithelial tubular network and its main role is
delivering oxygen and this system arises from the tracheal placodes
The tracheal placodes are clusters of ectodermal cells which will differentiate at each side of 10
of the embryonic segments called T2 to A8.
During this process the cells of each cluster will try to invaginate and migrate into a complex
array in a stereotypic pattern, so that it can form the network of multicellular tubes.
During migratory process, tracheal cells will not undergo division but remain polarized along the
apical-basal axis.
the Fibroblast Growth Factor (FGF) homologue Branchless (Bnl) [32] are the main
chemoattractant.
By activating the FGF receptor (FGFR) Breathless (Btl) on tracheal tip-cells, we can achieve the
Bnl chemoattraction and bnl will determine the both the earliest branching events and the later
programs of tracheal gene expression and like this high numbers of tracheal cells migrates
towards CNS when expression occurs. Like this excess of bnl expression will result in extra
tracheal migration and branching.
If the cell is a hh mutant it will have severe tracheal defect in embryonic stage and the tracheal
tree is stalled and cells remain at the placode region.
By shoeing direct effect in the extension of the terminal cells of the dorsal branch, the Hh will
bring tracheal cell migration and the Hh signaling pathway known to regulates bnl expression via
Stripe (Sr) (it’s a transcription factor with homology to the (EGR).
IN the figure they showed how Hh participate in tracheal cell migration.
It’s a schematic representation of one tracheal placode at stage 13;
Here you can see the tip or each branch is expressing the Bnl and it is spread to the surrounding
tissues and provides a chemoattractive signal.
In C we can see how Hh signaling induces in the cells surrounding the tracheal tip cells,the
expression of Bnl in the cells surrounding the tracheal tip cells.

2. Solution
For morphogenesis, we need cell migration and guidance and during migration, cell
directionality and movement will be induced by guidance molecules through a complex
intracellular mechanism.
Correct navigation occurs when cells exhibit these guidance molecules properly and when these
signals are properly interpreted by the receiving cells.
For anomal cellular growth and differentiation we need Hedgehog (Hh) signaling pathway.
The Hedgehog (Hh) signaling pathway involves cell proliferation, patterning, axonal guidance,
and angiogenesis in sequential manner.
Hh Signaling in Tracheal Cell Migration
In Drosophila, the tracheal system is a branched epithelial tubular network and its main role is
delivering oxygen and this system arises from the tracheal placodes
The tracheal placodes are clusters of ectodermal cells which will differentiate at each side of 10
of the embryonic segments called T2 to A8.
During this process the cells of each cluster will try to invaginate and migrate into a complex
array in a stereotypic pattern, so that it can form the network of multicellular tubes.
During migratory process, tracheal cells will not undergo division but remain polarized along the
apical-basal axis.
the Fibroblast Growth Factor (FGF) homologue Branchless (Bnl) [32] are the main
chemoattractant.
By activating the FGF receptor (FGFR) Breathless (Btl) on tracheal tip-cells, we can achieve the
Bnl chemoattraction and bnl will determine the both the earliest branching events and the later
programs of tracheal gene expression and like this high numbers of tracheal cells migrates
towards CNS when expression occurs. Like this excess of bnl expression will result in extra
tracheal migration and branching.
If the cell is a hh mutant it will have severe tracheal defect in embryonic stage and the tracheal
tree is stalled and cells remain at the placode region.
By shoeing direct effect in the extension of the terminal cells of the dorsal branch, the Hh will
bring tracheal cell migration and the Hh signaling pathway known to regulates bnl expression via
Stripe (Sr) (it’s a transcription factor with homology to the (EGR).
IN the figure they showed how Hh participate in tracheal cell migration.
It’s a schematic representation of one tracheal placode at stage 13;
Here you can see the tip or each branch is expressing the Bnl and it is spread to the surrounding
tissues and provides a chemoattractive signal.

3. In C we can see how Hh signaling induces in the cells surrounding the tracheal tip cells,the
expression of Bnl in the cells surrounding the tracheal tip cells.