Indian hedgehog (protein)

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]