Fig. 7.

Secretagogin silencing disrupts neuroblast migration in vitro. (A–A′′′) RMS explants from P5 rat pups preserve polarity with migrating cells at the rostral (A′) but not caudal (A′′) pole with secretagogin⁺ neurons retaining their positions within explants (A′′′). (A₁–A_2′′) In controls neuroblasts migrate from the rostral pole of the RMS explants into Matrigel along corridors (arrows in A_1′ and A_1′′), which are shaped by secretagogin⁺ neurons. Secretagogin silencing disrupts cell migration (dashed curves in A_2′ and A_2′′). (A₃–A₅) Although the total area in the Matrigel occupied by migratory neurons decreased only nonsignificantly upon gene silencing, both the maximal and the average distance of secretagogin⁺ cells was significantly reduced from RMS exit. (B–B_1′) In primary culture from P5 RMS plated on PDL, neuroblasts contacting secretagogin⁺ neurons (white arrowheads in B and B₁) typically expressed DCX. (The gray arrowhead in B points to a DCX⁻ neuron.) (B₂–B₂′′) On laminin-coated surfaces, secretagogin⁺ neurons (white arrowheads in B₂) formed scaffolds for DCX⁺ neuroblasts. (B₃) Secretagogin silencing decreased secretagogin mRNA levels but left DCX mRNA expression unaltered. P < 0.05, Student’s t test. (Scale bars: 500 µm in A; 70 µm in A′–A′′′; 25 µm in A₁–A_1′′; 10 µm in B; and 3 µm in B₂′′.)