DIFFERENTIAL EXPRESSION OF ETS-1 AND ETS-2 PROTOONCOGENES DURING MURINE EMBRYOGENESIS

ets-l and ets-2 genes have previously been identified by their sequenc e homology to the v-ets oncogene of the avian erythroblastosis virus, E26. These cellular genes have been shown to function as transcription factors important in lymphoid differentiation and activation and cell ular proliferation. In this study, we have broadly analysed the differ ential expression of ets-l and ets-2 during murine development using i n situ hybridization. Our results indicate that these transcription fa ctors are expressed in multiple tissues during critical stages of embr yo formation and organogenesis, suggesting that these genes may serve multiple functions during mouse development. The patterns of expressio n of both genes are quite different as early as day 8.0 of gestation. ets-l expression is clearly observed during a narrow developmental sta ge in the developing nervous system, including the presumptive hindbra in regions, the neural tube, as well as neural crest and the first and second branchial arches. ets-2 expression is limited to the developin g limb buds and distal tail. At later times, ets-l expression is obser ved in developing vascular structures, including the heart, arteries, capillaries and meninges, whereas ets-2 is highly expressed in develop ing bone, tooth buds, epithelial layers of the gut, nasal sinus and ut erus, and several regions of the developing brain. Both ets-l and ets- 2 are expressed in developing lung, gut and skin. High levels of expre ssion in both genes is observed in adult lymphoid tissues, but in diff erent tissue subsets. ets-l is expressed in the adult lung, gut mesenc hyme and bone marrow. ets-2 continues to be expressed at low levels in several adult tissues, except in the differentiated brain, where subs tantial levels of expression are found in particular regions of the ma ture brain. These results demonstrate that ets-l and ets-2 are differe ntially regulated, are widely expressed in many tissues during murine embryogenesis and may play important roles in cellular proliferation a nd differentiation during mouse development.