Multiple restricted origin of oligodendrocytes - PubMed (original) (raw)

Fig. 1.

Structure and distribution of the plp-sh ble-lacZ transgene. A, Schematic diagram of the_plp-sh ble-lacZ_ construct. The transgene, consisting of_sh ble_ (372 bp) fused in frame to the_lacZ_ gene (3 kb), is under control of the promoter (2.4 kb), exon 1, intron 1 (8.5 kb), and the first 37 bp of exon 2 of the mouse plp gene, and the SV40 polyadenylation site. See Materials and Methods for details. B–K, Expression of transgene and plp/dm-20 message during embryonic development of plp-sh ble-lacZ mice. Enzymatic β-gal activity was detected in whole-mount embryos at E8.5 (B, C) and E9.5 (D) and on brain and spinal cord at E12.5 (F–I), E14.5 (J), and E17.5 (K), using either the X-gal or Bluo-gal (H) substrate. Expression of endogenous_plp was detected by ISH with a DIG-labeled_plp antisense cRNA on E9.5 sagittal cryosections (E). B, C, At E8.5, β-gal activity is detected in neural crest cells arising from the mesencephalon and the rostral rhombencephalon (B). Caudally, β-gal activity is expressed in the notocord facing the unsegmented plate (arrow), as seen on a transversal cryosection counterstained with fuschin (C). D, E, At E9.5, the transgene is first expressed (Figure legend continues)in the CNS in the caudal hypothalamus (cH), the basal plate of diencephalon (bpD), the dorsal metencephalon (dMt), and the rhombic lip (RL). This pattern of β-gal expression in the embryonic brain is superimposable on the distribution of plp/dm-20 transcripts detected by ISH (E). Note, in D, that β-gal expression is maintained in cells derived from the neural crest localized in the mesectoderm of the mandibular branchial arch (md), the cranial and spinal nerves and ganglia (small arrows), as well as in the nerves and ganglia of the autonomous nervous system (arrowhead).F–I, In the CNS of E12.5 embryos from line numbers 1 (F), 14 (G, I), and 34 (H), the patterns of transgene expression are superimposable. In addition to the rostral pattern observed at E9.5, there is expression in the olfactory bulb (Ob), the entopeduncular area (asterisk), the zona limitans intrathalamica (ZL) (limit between the p2–p3 prosomeres), the posterior commissure (arrowhead), and dorsally in the diencephalomesencephalic junction (DMj). In the cervical spinal cord (SC), β-gal activity is detected both dorsally and ventrally. In the spinal cord, the dorsal territory of expression of the transgene (illustrated on a dorsal view in I) stops at the cervicothoracic junction. Note the absence of detectable transgene-expressing cells in the mesencephalic basal plate and rhombomeres r3–r5. J, K, Overview of a mediosagittal section of the brain at E14.5 (J) and E17.5 (K). At E14.5 (J) the diencephalic basal plate is homogeneously β-gal positive from the mammillary region to the mesencephalic/diencephalic limit. Rostrocaudally, four positive areas are observed in the diencephalic alar plate, corresponding to axonal tracts: the stria medullaris (SM) at the level of the eminentia thalami, the zona limitans intrathalamica (ZL), the retroflexus tract (Rt), and the posterior commissure (PC). The cerebellar midline is also positive (Cb). At E17.5 (K) β-gal positive domains in the diencephalic basal plate correspond to the area of the mammillotegmental tract (Mt) and the rostral pole of the medial longitudinal fascicle (MLF). Dorsally the limit between p4 and p3, the zona limitans (ZL), the posterior commissure (PC), and the cerebellar midline (Cb) are also β-gal positive. Other positive domains correspond to the optic chiasm (oc) and the optic nerve (on), the anterior dorsal midline of the mesencephalon (M), the epithalamus (EP), the pontine nuclei fibers (PN), and the tegmental metencephalic decussation (Td). M, Mesencephalon;Mm, mammillary region; NP, neural plate;OV, otic vesicle; Rh, rhombencephalon;S, somite; T, telencephalon. Scale bar (shown in B): B, 480 μm;C, 65 μm; D, F, G, 600 μm;E, 200 μm; H, 700 μm;I, 800 μm; J, 500 μm.