Homeodomatn genfs in vertebrate heart development

The objective of our research is to understand the molecular and eellui ar processes under 1yi ng heart development in the vert abrate inbryo. In Drosophila, the homeodomam gene t iiunan is requi red for' development of r ho do r s a 1 vesse J , t he i nse<-t equivalent of t he hear t . We have i related and character i zed t wo Xnopiif homeodoma in sequences , XNkx - ;.' r> and Xt inl , which are ielar ed ' <- t i nman . XNkx 2. . 5 and Xt in! share s urn J.a r r : ansrr ipt i on pat t er ns in the embryo and bot h are expi essed in myorard ia J proqer.i t or r. long before <ard ] ;v di f f erent lat '. on . Recent exper iments have shown that, inject ion of either XNkx-2.5 or Xtinl synthetic- mRNA in<-o the Xenopt/p embryo results in a signif icant increase in t he vo1ume of heart musc le t issue . Inject i on of a con t roi X&nopiift homeodomain sequence , Xhox4 , has no de t ec-r.abl e ef f ect on cardiac morphogenesis . These i esul t s suggest r hat XNkx -,'. 3 and Xtinl play an important role in the early events of cardioyenesis . uur future exper irnen'. K aie des igned to determine the mechanism by wrn ch t he i nci'ease in heart s i ze is achieved and to ident i fy genes r egulated by XNkx-J. 5 and Xtinl in the heart development pathway.