Whole-mount in situ hybridization with trkC1 and trkC2 antisense digoxigenin-labeled RNA probes. A lateral view of the trunk of trkC1-hybridized (A) and trkC2-hybridized (B) embryos. Rostral is to the left and dorsal is up. The hybridization signal is blue and is found in the dorsal trunk for trkC1 and more ventrally for trkC2. The positions of the spinal cord (sc), floor plate (fp), notochord (n), and yolk (y) are indicated. The plane of focus required to view the trkC1- and trkC2-positive cells is different. In A the trkC1-positive cells are in the same plane of focus as the spinal cord and notochord, whereas in B the trkC2-positive cells are in the same plane of focus as the muscle. In addition, the somite boundaries can be more easily seen in B than in A. All scale bars, 50 μm.

The expression of trkC1 in Rohon?Beard cells in the spinal cord and the location of trkC2 expression in the trunk. (A) A transverse section of the trunk of a trkC1-hybridized embryo showing the position of the positive cell in the dorsal spinal cord and (B) a dorsal view of the trunk with trkC1 (blue) and the HNK-1 antibody (brown) double labeling. Rostral is to the left. The position of the dorsal longitudinal fascicle (dlf) is indicated. (C) A transverse section of a trkC2-hybridized embryo showing the position of the positive cell in the trunk, relative to the muscle (m), spinal cord (sc), and notochord (n). y, yolk. Scale bars, 50 μm (A, C); 25 μm (B).

The expression of trkC2 in the caudal hindbrain. (A) A lateral view of the hindbrain of an embryo, 27 h after fertilization, that was hybridized with an antisense trkC2 probe. The positive cells are located in the caudal hindbrain next to the first two somites. Rostral is to the left and dorsal is up. (B) A coronal section through the caudal hindbrain of a trkC2-hybridized embryo, 27 h after fertilization, showing the position of the positive cells located ventrally and laterally. Dorsal is up. hb, hindbrain; m, muscle; y, yolk, and n, notochord. All scale bars, 50 μm.

The expression of trkC1 in the cranial ganglia. (A) A lateral view of a trkC1-hybridized embryo, 22 h after fertilization with rostral to the left, and (B) a dorsal view of an embryo hybridized with trkC1 24 h after fertilization. The blue trkC1-positive cells are located in the trigeminal ganglion (tg), anterior lateral line ganglion (allg), posterior lateral line ganglion (pllg), and Rohon?Beard neurons (rb). The positions of the eye (e) and yolk (y) are indicated. (C) A lateral view of an embryo hybridized with trkC1, 22 h after fertilization with rostral to the left showing the anterior lateral line ganglion (allg) and posterior lateral line ganglion (pllg) and otic vesicle (ov) at higher magnification than in A. (D) A lateral view of an embryo hybridized with trkC1, 27 h after fertilization showing the anterior lateral line ganglion (allg) and trigeminal ganglion (tg) at higher magnification than in B. (E) An embryo double labeled with the HNK-1 antibody (brown) and trkC1 (blue), 27 h after fertilization and (F) 19 h after fertilization (F). Rostral is to the left and dorsal is up. The positions of the trigeminal ganglion (tg), anterior lateral line ganglion (allg), posterior lateral line ganglion (pllg), Rohon?Beard neurons (rb), otic vesicle (ov), and yolk (y) are indicated. All scale bars, 50 μm.

The expression of trkC1 and trkC2 in the brain, 24 h (D, J) and 27 h (C, F, I, K, and L) after fertilization. (A, B) Schematic drawings of trkC1 (A) and trkC2 (B) expression (blue) in the forebrain and midbrain shown in a lateral view. The plane of the sections in D and F is indicated. (C) A lateral view of the forebrain and midbrain of an embryo hybridized with trkC2. Rostral is to the left and dorsal is up (A?C). The sites of expression are the dorsal telencephalon (t), the nucleus of the tract of the postoptic commissure (ntpoc), anterior hypothalamus (h), and ventral midbrain (mb). (D) A frontal view of a trkC1-hybridized embryo. Dorsal is up. The positive cells labeled blue are located in the telencephalon (t) and the nucleus of the tract of the postoptic commissure (ntpoc). The positions of the eye (e) and the olfactory placode (op) are indicated. (E, F) Sections of a trkC2-hybridized embryo showing the positive cells in the nucleus of the tract of the postoptic commissure (ntpoc) (E), and ventral midbrain (mb) (F).

Expression of trkC1 and trkC2 in the hindbrain. (A) Dorsal view of an embryo hybridized with trkC1. Rostral is to the top. No hindbrain expression of trkC1 was detected but hybridization was detected in the posterior lateral line ganglion (pllg), which is situated next to the hindbrain. (B) Dorsal view of an embryo at 27 h after fertilization hybridized with trkC2. The positive cells are located in rhombomeres (r) 4, 5, and 6, next to the otic vesicle (ov). (C) A lateral view of trkC2 hybridization showing the location of the positive cells in the hindbrain. Rostral is to the left and dorsal is up. (D) A cross section through the hindbrain of a trkC2-hybridized embryo at the level of the otic vesicle with dorsal up. Neural red counterstain. (E) A dorsolateral view of an embryo double labeled with a trkC2 probe (blue) and with the HNK-1 antibody (brown). Reticulospinal neurons are single labeled (HNK-1) in rhombomere 3 but are double labeled with the HNK-1 antibody and trkC2 in rhombomeres 4, 5, and 6. The otic vesicle (ov), hindbrain (hb), posterior lateral line ganglion (pllg), and rhombomere (r) locations are indicated. All scale bars, 50 μm.