role of sonic hedgehog in development

7/29/2019 Role of Sonic Hedgehog in Development

1/4

Role of Sonic Hedgehog in Development

By

Elizabeth Hackett

Submitted To The Faculty of The University of Arkansas at Little Rock In Partial Fulfillment Of The

Requirements or Completion Of Developmental Biology 3400

December 13, 2012


2/4

Abstract

Text

The Hedgehog Family

The Hedgehog family of secreted proteins govern a wide variety of processes during embryonic development and adult

tissue homeostasis. This family of paracrine factors are one of the most important groups of signaling molecules that regulate cell

differentiation and organ formation during development, and they used by the embryo to induce particular cell types and to create

boundaries between tissues (Gilbert 90). The hedgehog (hh) gene was discovered nearly thirty years ago as a segment polarity gene

that regulate segmental polarity of the blastoderm and the specification of imaginal disc during metamorphosis in the fruit

fly,Drosophila melanogaster (Jiang and Hui 801). InDrosophila and other invertebrates, there is only one type of hedgehog gene.

On the other hand, vertebrates have a family of genes that are homologous to the hh gene. Mammals have three genes with

homology to theDrosophila hh gene, which can be categorized into the subgroups: the Desert Hedgehog (DHH), Indian Hedgehog

(IHH), and Sonic Hedgehog (SHH).

Embryogenesis is controlled by diverse signal transduction pathways. Through these signaling pathways, the same signals

can trigger different types of cell differentiation responses in different embryonic cells, thereby orchestrating cell differentiation

programs in the developing embryo.

Hedgehog family is a family of paracrine factors Proteins must become complexed with a molecule of cholesterol in order

to function.

Hedgehog pathway: proteins activated by the binding of a Hedgehog protein to the patched receptor. When Hedgehog

binds to Patched, the Patched proteins shape is altered such that is no longer inhibits Smoothened. Smoothened acts to release the

Ci protein protein from the microtubules and to prevent its being cleaved. The intact Ci protein can now enter the nucleus, where it

acts a transcriptional activator of the same genes it used to repress.

The major Hedgehog family paracrine factor is Sonic Hedgehog. SHH has distinct functions in different tissues of the

embryo

Sonic hedgehog is a morphogen, which is a molecule that diffuses to form a concentration

gradient that differentially influences the cells of a developing embryo in a concentration dependent

manner.


3/4

List of figures

Fig 1.

Hedgehog signal transduction pathway

Fig 2

A positive feedback loop coordinates vertebrate limbdevelopment.

Patched Receptor (PTC)

Smoothened (Smo)

Hedgehog binding state (Hh+/-)


4/4

Literature Cited

Gilbert, Scott F. Developmental Biology. Sunderland, MA: Sinauer Associates, 2006. Print.

Jiang, Jin, and Chi-chung Hui. "Hedgehog Signaling in Development and Cancer."Developmental Cell15.6 (2008): 801-12. ScienceDirect.

Web. Oct.-Nov. 2012.

Rangarajan, P. N. "Eukaryotic Gene Expression: Basics & Benefits." Nptel. N.p., 2008. Web.

role of sonic hedgehog in development

Documents