The chick optic tectum consists of 16 laminae. Here, we report contribution of En2 to laminar formation in chick optic tecta. En2 is specifically expressed in laminae g-j of stratum griseum et fibrosum superficiale (SGFS). Misexpression of En2 resulted in disappearance of En2-expressing cells from the superficial layers (laminae a-f of SGFS), where endogenous En2 is not expressed. Misexpression of En2 before postmitotic cells had left the ventricular layer indicated that En2-misexpressing cells stopped at the laminae of endogenous En2 expression and that they did not migrate into the superficial layers. Induction of En2 misexpression using a tetracycline-inducible system after the postmitotic cells had reached superficial layers also resulted in disappearance of En2-expressing cells from the superficial layers. Time-lapse analysis showed that En2-misexpressing cells migrated back from the superficial layers towards the middle layers, where En2 is strongly expressed endogenously. Our results suggest a potential role of En2 in regulating cell migration and positioning in the tectal laminar formation.
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