#  Grad/Postdoc Projects  

 



Joseph Daniele - Graduate Student

Dme Hh axon transport is dependent on a conserved C-terminal sequence and HhN photoreceptor localization can be altered by manipulating a known Mts/Akt pathway

(A) In the late 3rd instar larval eye imaginal disc, undifferentiated photoreceptors extend axons down the optic stalk into the brain and begin secreting Hedgehog protein at both the apical (retina) end and at the basal (growth cone) end. The Hh secreted from the basal side will induce the early steps of lamina development and Hh secreted at the retina will induce photoreceptor differentiation in a stereotyped posterior to anterior wave.

(B) Eye development is dependent on this apical and basal hegehog signal. (Right) wild type eye, (left) hh1 bar eye lacking eye-specific hegehog expression.

(C) Drosophila melanogaster (Dme) Hh processing consists of two cleavage events following protein translocation into the ER where the signal sequence (SS) is clipped off. The 1st cleavage consists of an autocleavage event, with cholesterol as the nucleophile, resulting in HhN and HhC24. The 2nd cleavage consists of the growth cone targeting sequence (yellow star) being clipped off HhC24 resulting in a stable HhC16 and an unstable HhC9. After cholesterol addition to HhN a palmitic acid molecule is attached to its N terminal end.

 (D) A simple model for how HhN is sorted in PRs during development. All forms are synthesized in the apical domain yet only HhN traveling with HhC24 can move down the axon. Is it unknown how this decision is made and what the potential sorting signals are.

 (E) Immunohistochemistry of developing larval photoreceptors (PR) expressing transgenic HA tagged Hh constructs. In the full length Hh construct with HA in the N terminus(HhN::HA), we see HhN throughout the PR (left). Lsd2 and Mts are two examples of proteins identified in a screen to identify genes that control Dme Hh processing/trafficking. LSD2::GFP overexpression leads to more HhN in the growth cone (middle) while expression of a dominant negative form of Mts (DN-Mts) leads to more HhN in the photoreceptor cell body (right).

   ![slide1](/sites/g/files/omnuum7446/files/styles/hwp_1_1__360x360_scale/public/kuneslab/files/slide1.jpg?itok=-Ndx9fNg) 

 

**Rizwana Islam - Postdoctoral Fellow**