Comparison of Ndn and Snurf-Snrpn transcriptional unit expression patterns in the E13.5 mouse embryo. Comparison of Ndn (A, E, I), Snurf-Snrpn (B, F, J), MBII-85 (C, G, K) and MBII-52 (D, H, L) RNA expression on E13.5 mouse embryo adjacent sagittal sections, from lateral to more medial sections (rows I to II). Ndn as well as Snurf/Snrpn, MBII-85 and MBII-52 are almost exclusively expressed in the developing nervous system and display strikingly similar expression patterns in the developing brain and spinal chord. In the peripheral nervous system, Ndn and Snurf-Snrpn are expressed at similar levels in cranial (Ndn: A; Snurf-Snrpn: B) and dorsal root ganglia (Ndn: I; Snurf-Snrpn: J) whereas MBII-85 (C, K) and MBII-52 (D, L) are expressed at much lower levels or not at all. Note that Ndn is additionally expressed in muscle tissues such as the skeletal muscles (A) and the tongue (E), and in the adrenal primordium (I). ap, adrenal primordium; drg, dorsal root ganglia; gn, gonad; hp, hypothalamus; ht, heart; lg, lung; lv, liver; mb, midbrain; mo, medulla oblongata; mt, metanephros; ms, muscles; poa, post-optic area; pp, telencephalic epithelium preplate; ps, pons; sa, septal area; tg, tongue. Asterics indicate cranial and dorsal root ganglia in A, B, C, D.