Volume 2 - Issue 2 - IJMD

Review articleRole of Genetics in Patterning of Faceand JawsS Kishore Kumar*, Deepak Chandrasekaran*, Faisal Tajir**, A V Vidhya Lakshmi †AbstractGenetics is at present one of the most rapidly progressing fields in biology and biomedicine. The advances of gene technologyhave led to a rapid explosion in the understanding of the molecular mechanisms regulating embryonic development. New genesand their functions are continuously being discovered in experimental studies using animal embryos and molecular geneticstudies in humans are unraveling gene mutations causing congenital defects. It is now shown in the recent year studies thatthe homeobox gene plays an important role in the patterning of human face and jaws. Members of the homeobox – containinggenes are expressed in the cranial neural crest cell and function as transcriptional regulators that control cellular proliferationand differentiation during normal embryonic development.Key words: Neural crest cell, Hox group, Msx1 and Msx2 (muscle segment), Dlx (distalless), Otx (orthodontical), Gsc(goosecoid), and Endothelin -1, Sonic hedgehog.The development of human face is a well coordinated,complicated yet planned processthat requires integration of the surfaceectoderm, neural crest cell along with the mesodermaltissue.Patterning and morphogenesis of neural crest–derivedtissues rely on a complex balance between signalsacquired by neural crest cells in the neuroepitheliumduring their formation and signals from the tissuesthat the neural crest cells contact during theirmigration. Neural crest cells migrate ventrolaterallyto the frontonasal prominence and the branchialarches and give rise to the jaws, the anterior skull baseand the anterior skull vault. Neural crest cells carryinformation that directs the axial pattern and speciesspecificmorphology of the head and face. Signalinginteractions coordinate the outgrowth of the facialprimordia from buds of undifferentiated mesenchymeinto the intricate series of bones and cartilage structuresthat, together with muscle and other tissues, form theadult face.*Professor**Associate Professor†PG StudentDept. of Orthodontics and Dentofacial OrthopedicsSree Balaji Dental College and Hospital, Chennai.Address for correspondenceDr S Kishore KumarE-mail: spkkishorekumar@yahoo.comHowever, the way in which these molecules control theepithelial-mesenchymal interactions, which mediatefacial outgrowth and morphogenesis, is unclear. Thehomeobox genes Msx1 and Msx2 are highly conservedamong various species and function as transcriptionalregulators that control cellular proliferation anddifferentiation during normal embryonic development.It is now shown that Msx1 is strongly expressedin neural crest cells and plays a critical role inregulating epithelial-mesenchymal interactions duringorganogenesis 1Homeobox genes play a important role in patterningthe embryonic development. These can also be regardedas master genes of the head and face controllingpatterning, induction, programmed cell death, andepithelial mesenchymal interaction during developmentof the craniofacial complex.Those of particular interest in craniofacial developmentinclude the Hox group, Msx1 and Msx2 (musclesegment), Dlx (distalless), Otx (orthodontical), Gsc(goosecoid), and Shh (sonic hedgehog).This article outlines the role of these genes in patterningof the face and jaws.Neural crest cellThe development of the mesoderm of the vertebratehead involves different mechanisms from that of thetrunk. These differences may be related to the presence448Indian Journal of Multidisciplinary Dentistry, Vol. 2, Issue 2, February-April 2012