Fig. 1. Domain structure and expression of ABBA. (A) ABBA is composed of an N-terminal IM domain, a serine-rich region, three proline-rich motifs and a C-terminal WH2 domain. (B) Northern blot analysis of ABBA expression in adult mouse tissues shows a single band that was predominant in brain. Each lane contains 2 µg total RNA. RNA in situ hybridisation analysis on sections from mouse embryos at E12.5 (C-F), E14.5 (G-I) and E18.5 (J) and adult cerebellum (K). Probes are indicated in the images. At E12.5 ABBA is strongly expressed in the floorplate of the spinal cord (C) and hindbrain (F), whereas weaker expression is detected in parenchyma and in the outer border of the marginal zone (arrowheads) where radial glia endplates locate. (D) MIM is expressed in spinal cord neurons and its expression is distinct from that of ABBA. (E) No specific signal was obtained with the ABBA sense probe. (G) Sagittal section from E14.5 mouse head where ABBA mRNA was detected in the pial surface surrounding the brain and in the midline glial raphe. (H) ABBA mRNA was detected in the developing cortex at E14.5 and especially in the outer border of the marginal zone (arrowhead). Cross section at E14.5 (I) and sagittal section at E18.5 (J) show ABBA expression in the brainstem raphe. (K) In the adult brain, the strongest ABBA expression is confined to the molecular layer of the cerebellum. cp, cortical plate; fp, floorplate; hb, hindbrain; mz, marginal zone; ra, glial raphe; spc, spinal cord; vz, ventricular zone. Scale bars: 0.1 mm in C-F, H-K and 0.2 mm in G.