Desert hedgehog, also Desert hedgehog homolog or DHh, is a protein encoded by the DHH gene, and is a member of the

hedgehog signaling pathway The Hedgehog signaling pathway is a signaling pathway that transmits information to embryonic cells required for proper cell differentiation. Different parts of the embryo have different concentrations of hedgehog signaling proteins. The pathwa ...

. The human homolog (DHH) is on

chromosome A chromosome is a package of DNA containing part or all of the genetic material of an organism. In most chromosomes, the very long thin DNA fibers are coated with nucleosome-forming packaging proteins; in eukaryotic cells, the most import ...

band 12q13.1. The protein encoded by this gene is involved in

cell signaling In biology, cell signaling (cell signalling in British English) is the Biological process, process by which a Cell (biology), cell interacts with itself, other cells, and the environment. Cell signaling is a fundamental property of all Cell (biol ...

. The several mammalian variants of the ''

Drosophila ''Drosophila'' (), from Ancient Greek δρόσος (''drósos''), meaning "dew", and φίλος (''phílos''), meaning "loving", is a genus of fly, belonging to the family Drosophilidae, whose members are often called "small fruit flies" or p ...

'' hedgehog gene ( which was the first named) have been named after the various species of

hedgehog A hedgehog is a spiny mammal of the subfamily Erinaceinae, in the eulipotyphlan family Erinaceidae. There are 17 species of hedgehog in five genera found throughout parts of Europe, Asia, and Africa, and in New Zealand by introduction. The ...

; the desert hedgehog is honored by this one. The gene is not specific to desert hedgehogs. The Desert Hedgehog gene has been identified in both humans and mouse models.

Function

This gene encodes a member of the hedgehog family. The hedgehog gene family encodes signaling molecules that play an important role in regulating

morphogenesis Morphogenesis (from the Greek ''morphê'' shape and ''genesis'' creation, literally "the generation of form") is the biological process that causes a cell, tissue or organism to develop its shape. It is one of three fundamental aspects of deve ...

. This protein is predicted to be made as a precursor that is autocatalytically cleaved; the

N-terminal The N-terminus (also known as the amino-terminus, NH2-terminus, N-terminal end or amine-terminus) is the start of a protein or polypeptide, referring to the free amine group (-NH2) located at the end of a polypeptide. Within a peptide, the amin ...

portion is soluble and contains the signalling activity while the

C-terminal The C-terminus (also known as the carboxyl-terminus, carboxy-terminus, C-terminal tail, carboxy tail, C-terminal end, or COOH-terminus) is the end of an amino acid chain (protein or polypeptide), terminated by a free carboxyl group (-COOH). When t ...

portion is involved in precursor processing. More importantly, the C-terminal product

covalently A covalent bond is a chemical bond that involves the sharing of electrons to form electron pairs between atoms. These electron pairs are known as shared pairs or bonding pairs. The stable balance of attractive and repulsive forces between atoms ...

attaches a

cholesterol Cholesterol is the principal sterol of all higher animals, distributed in body Tissue (biology), tissues, especially the brain and spinal cord, and in Animal fat, animal fats and oils. Cholesterol is biosynthesis, biosynthesized by all anima ...

moiety to the N-terminal product, restricting the N-terminal product to the cell surface and preventing it from freely

diffusing Molecular diffusion is the motion of atoms, molecules, or other particles of a gas or liquid at temperatures above absolute zero. The rate of this movement is a function of temperature, viscosity of the fluid, size and density (or their product, ...

throughout the organism. The hedgehog signaling pathway allows for signal transmission between cell membranes and the nucleus. While Dhh is mostly inactive in adults, this gene plays an important role in embryonic development. While ''

,'' the species this gene was discovered in, has only been shown to have one Hedgehog gene, three different genes in the Hedgehog family have been identified in

vertebrates Vertebrates () are animals with a vertebral column (backbone or spine), and a cranium, or skull. The vertebral column surrounds and protects the spinal cord, while the cranium protects the brain. The vertebrates make up the subphylum Vertebra ...

. These genes are '' Sonic Hedgehog (SHh), Indian Hedgehog (IHh), and Desert Hedgehog (DHh).'' The expression of DHh is mostly limited to the gonadal cells. More specifically, this gene is commonly identified within the

sertoli cells Sertoli cells are a type of sustentacular "nurse" cell found in human testes which contribute to the process of spermatogenesis (the production of sperm) as a structural component of the seminiferous tubules. They are activated by follicle-sti ...

of the

testes A testicle or testis ( testes) is the gonad in all male bilaterians, including humans, and is homologous to the ovary in females. Its primary functions are the production of sperm and the secretion of androgens, primarily testosterone. The ...

. This gene plays a large role in the cell differentiation within these germ cells.

Clinical significance

Defects in this protein have been associated with partial gonadal dysgenesis (PGD) accompanied by minifascicular

polyneuropathy Polyneuropathy () is damage or disease affecting peripheral nerves (peripheral neuropathy) in roughly the same areas on both sides of the body, featuring weakness, numbness, and burning pain. It usually begins in the hands and feet and may prog ...

. This protein may be involved in both male

gonad A gonad, sex gland, or reproductive gland is a Heterocrine gland, mixed gland and sex organ that produces the gametes and sex hormones of an organism. Female reproductive cells are egg cells, and male reproductive cells are sperm. The male gon ...

al differentiation and perineurial development. The presence of DHh in sertoli cells allows for proper testicular development and differentiation of the germ cells within the testes. Blocking the DHh signaling throughout testes development results in disrupted spermatogenesis along with infertility. Mutations in DHh expression result in infertility, likely due to the blockage of the cell differentiation process.

Animal Models

Mouse models show very serious effects are a result of both a repression and an overexpression of DHh. Mutant mice with a DHh expression deficiency show malformations and growth restriction in the

Central Nervous System The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain, spinal cord and retina. The CNS is so named because the brain integrates the received information and coordinates and influences the activity o ...

, skeletal, limb, and craniofacial structural development. Additionally, persistent high levels of DHh expression have been connected with tumor development in organ tissues of postnatal mice.

References

External links

* {{gene-12-stub