▁ ▁The ▁mig rat ory ▁cluster ▁is ▁initi ated ▁by ▁J AK - STAT ▁path way ▁and ▁is ▁gu ided ▁by ▁the ▁growth ▁of ▁long ▁cell ular ▁extensions . ▁The ▁direction al ▁c ues ▁are ▁provided ▁by ▁re ceptor ▁ty ros ine ▁kin ases . ▁ ▁C ells ▁that ▁under go ▁such ▁a ▁change ▁in ▁fate ▁as ▁mig rat ory ▁border ▁cells ▁have ▁two ▁distinct ▁alternatives : ▁re organ ize ▁the ▁existing ▁prote ins ▁or ▁bring ▁about ▁massive ▁changes ▁in ▁gene ▁expression . ▁In ▁our ▁case , ▁the ▁latter ▁case ▁seems ▁to ▁hold ▁true . ▁The ▁trans cription ▁factor ▁sl bo ▁which ▁comm ande ers ▁the ▁trans cription ▁of ▁several ▁gen es ▁is ▁believed ▁to ▁be ▁central ▁to ▁this ▁phenomen on . ▁sl bo ▁was ▁identified ▁in ▁a ▁P - element ▁screen ▁for ▁female ▁ster ility ▁several ▁years ▁ago ▁– ▁and ▁since ▁then ▁several ▁prote ins ▁down stream ▁of ▁it ▁have ▁come ▁up . ▁The ▁sl bo ▁loc us ▁enc odes ▁the ▁D ros oph ila ▁hom olog ▁of ▁the ▁m amm al ian ▁C CA AT ▁en han cer ▁binding ▁protein ▁( C / EB P ) ▁– ▁a ▁basic ▁region - le uc ine ▁z i pper ▁trans cription ▁factor , ▁and ▁it ▁was ▁thus ▁expected ▁that ▁one ▁or ▁more ▁of ▁its ▁targets ▁would ▁be ▁essential ▁in ▁migration . ▁ ▁Import ance ▁ ▁This ▁migration ▁of ▁the ▁border ▁cells ▁appears ▁to ▁be ▁important ▁for ▁two ▁reasons ▁– ▁the ▁formation ▁of ▁a ▁structure ▁called ▁a ▁mic rop yle , ▁which ▁is ▁important