(A–D) MDGA2A staining in wt and MDGA2A knockdown zebrafish at 3dpf. Lateral views of MDGA2A labeled zebrafish demonstrate that antisense morpholino injections against MDGA2A efficiently downregulates the expression of MDGA2A. Neither MDGA2A positive hair cells along the otic vesicle (oc) nor the trigeminal nerve (asterisk) are stained in MDGA2A morphants (A,B). Also staining in the mlf and PLL is clearly downregulated (C,D). (E–H) Migration and axon outgrowth pattern of branchiomotoneurons in wt and MDGA2A knockdown zebrafish at 3dpf. In wt fish branchiomotoneurons occupy characteristic locations, with the trigeminal cluster being located in r2/r3 and the facial cluster lying adjacent to the midline (E). In MDGA2A morphants, trigeminal neurons settle at ectopic locations (arrow) (F). Moreover, staining intensity in the trigeminal (asterisk) and facial (arrowhead) nerve is strongly reduced in MDGA2A knockdown larva, suggesting that fewer axons are present in these nerve bundles. Abbreviations: ov otic vesicle; mlf medial longitudinal fascicle; PLL posterior lateral line fascicle; V trigeminal motoneurons; VII facial motoneurons; X vagal motoneurons. Scale bars in A,B, and E–H equal 50µm, in C,D 25µm.
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