Indian hedgehog homolog (Drosophila), also known as IHH, is a protein which in humans is encoded by the IHH gene. [5] [6] [7] This cell signaling protein is in the hedgehog signaling pathway. The several mammalian variants of the Drosophila hedgehog gene (which was the first named) have been named after the various species of hedgehog; the Indian hedgehog is honored by this one. The gene is not specific to Indian hedgehogs.
The Indian hedgehog protein is one of three proteins in the mammalian hedgehog family, the others being desert hedgehog (DHH) and sonic hedgehog (SHH). [8] It is involved in chondrocyte differentiation, proliferation and maturation especially during endochondral ossification. It regulates its effects by feedback control of parathyroid hormone-related peptide (PTHrP). [9]
Indian Hedge Hog, (Ihh) is one of three signaling molecules from the Hedgehog (Hh) gene family. [10] Genes of the Hh family, Sonic Hedgehog (Shh), Desert Hedgehog (Dhh) and Ihh regulate several fetal developmental processes. [10] The Ihh homolog is involved in the formation of chondrocytes during the development of limbs. [10] The protein is released by small, non-proliferating, mature chondrocytes during endochondral ossification. [10] Recently, Ihh mutations are shown to cause brachydactyly type A1 (BDA1), the first Mendelian autosomal dominant disorder in humans to be recorded. [10] [11] There are seven known mutations to Ihh that cause BDA1. [11] Of particular interest, are mutations involving the E95 residue, which is thought to be involved with proper signaling mechanisms between Ihh and its receptors. [11] In a mouse model, mice with mutations to the E95 residue were found to have abnormalities to their digits. [12]
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. [13] Ihh is suspected to be involved in the downstream regulation of other signaling molecules that are known to play a role in murine implantation. [14] Mouse models involving Ihh null mice demonstrated failure of attachment and decidualization. [14]
Sonic hedgehog protein (SHH) is encoded for by the SHH gene. The protein is named after the video game character Sonic the Hedgehog.
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. However, it also has normal functions in bone, teeth, vascular tissues and other tissues.
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 immature chondrocyte, the term is imprecise, since the progenitor of chondrocytes can differentiate into various cell types, including osteoblasts.
Zinc finger protein GLI2 also known as GLI family zinc finger 2 is a protein that in humans is encoded by the GLI2 gene. The protein encoded by this gene is a transcription factor.
Zinc finger protein GLI3 is a protein that in humans is encoded by the GLI3 gene.
Chondrogenesis is the biological process through which cartilage tissue is formed and developed. This intricate and tightly regulated cellular differentiation pathway plays a crucial role in skeletal development, as cartilage serves as a fundamental component of the embryonic skeleton. The term "chondrogenesis" is derived from the Greek words "chondros," meaning cartilage, and "genesis," meaning origin or formation.
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 pathway also has roles in the adult. Diseases associated with the malfunction of this pathway include cancer.
Tyrosine-protein kinase transmembrane receptor ROR2, also known as neurotrophic tyrosine kinase, receptor-related 2, is a protein that in humans is encoded by the ROR2 gene located on position 9 of the long arm of chromosome 9. This protein is responsible for aspects of bone and cartilage growth. It is involved in Robinow syndrome and autosomal dominant brachydactyly type B. ROR2 is a member of the receptor tyrosine kinase-like orphan receptor (ROR) family.
Smoothened is a protein that in humans is encoded by the SMO gene. Smoothened is a Class Frizzled G protein-coupled receptor that is a component of the hedgehog signaling pathway and is conserved from flies to humans. It is the molecular target of the natural teratogen cyclopamine. It also is the target of vismodegib, the first hedgehog pathway inhibitor to be approved by the U.S. Food and Drug Administration (FDA).
Bone morphogenetic protein 6 is a protein that in humans is encoded by the BMP6 gene.
Growth/differentiation factor 5 is a protein that in humans is encoded by the GDF5 gene.
Limbin (LBN) is a protein that is part of the EvC complex that consists of EvC and EvC2 genes, the activity of which is critical in bone formation and skeletal development. The complex positively regulates ciliary Hedgehog (Hh) signaling due to the ciliary localization.
Neurogenic locus notch homolog 4(Notch 4) is a protein that in humans is encoded by the NOTCH4 gene located on chromosome 6.
Protein patched homolog 1 is a protein that is the member of the patched family and in humans is encoded by the PTCH1 gene.
Eyes absent homolog 1 is a protein that in humans is encoded by the EYA1 gene.
Homeobox protein DLX-3 is a protein that in humans is encoded by the DLX3 gene.
Suppressor of fused homolog is a protein that in humans is encoded by the SUFU gene. In molecular biology, the protein domain suppressor of fused protein (Sufu) has an important role in the cell. The Sufu is important in negatively regulating an important signalling pathway in the cell, the Hedgehog signalling pathway (HH). This particular pathway is crucial in embryonic development. There are several homologues of Sufu, found in a wide variety of organisms.
Forkhead box protein E1 is a protein that in humans is encoded by the FOXE1 gene.
Hedgehog interacting protein (HHIP) is a protein that in humans is encoded by the HHIP gene.
Ras-related protein Rab-23 is a protein that in humans is encoded by the RAB23 gene. Alternative splicing occurs at this gene locus and two transcript variants encoding the same protein have been identified.
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