Indian hedgehog homolog (Drosophila), also known as IHH, is a

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...

which in humans is encoded by the ''IHH''

gene In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...

. This

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 ...

protein is in 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 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

Indian hedgehog The Indian hedgehog (''Paraechinus micropus'') is a species of hedgehog native to India and Pakistan. It mainly lives in sandy desert areas but can be found in other environments. Description The Indian hedgehog can be compared to the long-eare ...

is honored by this one. The gene is not specific to Indian hedgehogs.

Function

The Indian hedgehog protein is one of three

s in the

mammalian A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...

family, the others being desert hedgehog (DHH) and

sonic hedgehog Sonic hedgehog protein (SHH) is a major signaling molecule of embryonic development in humans and animals, encoded by the ''SHH'' gene. This signaling molecule is key in regulating embryonic morphogenesis in all animals. SHH controls organoge ...

(SHH). It is involved in

chondrocyte Chondrocytes (, ) are the only cells found in healthy cartilage. They produce and maintain the cartilaginous matrix, which consists mainly of collagen and proteoglycans. Although the word '' chondroblast'' is commonly used to describe an immatu ...

differentiation, proliferation and maturation especially during

endochondral ossification Endochondral ossification is one of the two essential pathways by which bone tissue is produced during fetal development and bone healing, bone repair of the mammalian skeleton, skeletal system, the other pathway being intramembranous ossificatio ...

. It regulates its effects by feedback control of parathyroid hormone-related peptide (

PTHrP Parathyroid hormone-related protein (PTHrP) is a proteinaceous hormone and a member of the parathyroid hormone family secreted by mesenchymal stem cells. It is occasionally secreted by cancer cells (for example, breast cancer, certain types of ...

). Indian Hedge Hog, (Ihh) is one of three signaling molecules from the Hedgehog (Hh) gene family.Ma, G., Yu, J., Xiao, Y. et al. Indian hedgehog mutations causing brachydactyly type A1 impair Hedgehog signal transduction at multiple levels. Cell Res 21, 1343–1357 (2011). https://doi.org/10.1038/cr.2011.76 Genes of the Hh family, Sonic Hedgehog (Shh), Desert Hedgehog (Dhh) and Ihh regulate several fetal developmental processes. The Ihh homolog is involved in the formation of chondrocytes during the development of limbs. The protein is released by small, non-proliferating, mature chondrocytes during endochondral ossification. Recently, Ihh mutations are shown to cause brachydactyly type A1 (BDA1), the first Mendelian autosomal dominant disorder in humans to be recorded.Lodder EM, Hoogeboom AJM, Coert JH, de Graaff E. 2008. Deletion of 1 amino acid in Indian hedgehog leads to brachydactylyA1. Am J Med Genet Part A 146A:2152–2154. doi:10.1002/ajmg.a.32441 There are seven known mutations to Ihh that cause BDA1. Of particular interest, are mutations involving the E95 residue, which is thought to be involved with proper signaling mechanisms between Ihh and its receptors. In a mouse model, mice with mutations to the E95 residue were found to have abnormalities to their digits. Ihh may also be involved in endometrial cell differentiation and implantation. Studies have shown progesterone to upregulate Ihh expression in the murine endometrium, suggesting a role in implantation.Qingxiang Wei, Eric D. Levens, Lilja Stefansson, Lynnette K. Nieman, Indian Hedgehog and Its Targets in Human Endometrium: Menstrual Cycle Expression and Response to CDB-2914, The Journal of Clinical Endocrinology & Metabolism, Volume 95, Issue 12, 1 December 2010, Pages 5330–5337, https://doi.org/10.1210/jc.2010-0637 Ihh is suspected to be involved in the downstream regulation of other signaling molecules that are known to play a role in murine implantation.Kathryn Smith, Redab Alnifaidy, Qingxiang Wei, Lynnette K. Nieman, Endometrial Indian hedgehog expression is decreased in women with endometriosis, Fertility and Sterility, Volume 95, Issue 8, 2011, Pages 2738-2741.e3, ISSN 0015-0282, https://doi.org/10.1016/j.fertnstert.2011.05.018. Mouse models involving Ihh null mice demonstrated failure of attachment and decidualization.

Function

References

Further reading