In situ hybridization analysis of muskelin transcripts in the developing mouse embryo. (A) Schematic representation of muskelin. Individual protein domains are indicated. L: LisH domain; H: LisH homology domain (also known as CTLH for: C-terminal to LisH domain). The probes used for in situ hybridization are indicated with black bars. (B) Micrographs of X-ray films showing whole embryo sagittal sections from embryonic stages E12.5, E14.5 and E16.5. Data obtained with probe 1 are shown in representation for similar results with probes 2–4. The sense control displays a parallel experiment using sense RNAs as probe. (C) E12.5 coronal section through a posterior region at the midbrain level using probe 5 (a). High expression levels of muskelin mRNA were observed in the subventricular zone of the cortex, and the amygdala as well as in the neuroepithelium of the thalamus and hypothalamus. High magnification of a coronal section through the eye (b) at E12.5 showing the presence of muskelin transcripts in the lens vesicle, the neural retina and the retinal pigmented epithelium. Weak signal was detected in the optic nerve. (c) Coronal section through the spinal cord, showing muskelin mRNA expression in the ependymal and ventral mantle layers and in the DRG. Key: A, amygdala; ChP, choroid plexus; Cx, cortex; DRG, dorsal root ganglia; HTh, hypothalamus; LVS, lens vesicle; MB, midbrain; MO, medulla oblongata; NR, neural retina; ON, optic nerve; Ps, pons; RPE, retinal pigmented epithelium; SC, spinal cord; Th, thalamus. Scale bars: (B) 1 mm each, (C) (a) 1 mm, (b) and (c) 500 nm.