December 1, 2002;
119 Suppl 1
Molecular cloning and expression analysis of dystroglycan during Xenopus laevis embryogenesis.
is a transmembrane receptor protein that provides a structural linkage between extracellular matrix
components and cytoskeletal proteins. It was originally characterized as a member of dystrophin
associated protein complex in muscle
but, unlike other proteins of this complex, mutations in the dystroglycan
gene have not been implicated as a cause of muscular dystrophies. Indeed, dystroglycan
is an essential gene, expressed early in development that, if removed in knockout mice, provokes lethal defects before the onset of myogenesis. Dystroglycan
is synthesized as a precursor propeptide that is post-translationally cleaved and glycosylated to yield alpha and beta subunits. We have cloned and characterized a cDNA clone, containing the complete coding region of the dystroglycan
precursor, from a Xenopus laevis cDNA library. We have performed a spatial and temporal analysis of its expression in X. laevis embryos, using whole-mount in situ hybridization and reverse transcription-polymerase chain reaction analysis. Early expression of dystroglycan
in a variety of tissues of different embryological derivation suggests a crucial role in morphogenetic events, especially during central nervous system
[+] show captions
Fig. 3. Expression of X-dg during Xenopus development (A). Whole-mount in situ hybridization was carried out using digoxigenin-labeled cRNA probe.
Nieuwkoop-Faber stages of embryogenesis are indicated in higher left corners. Dorsal views, anterior down (A, B, E); postero-lateral view (C); anterior views
(D, F, H); lateral views, anterior on the right (G, I). Transverse section of stage 22 (J): arrow head indicates sensorial layer of the ectoderm; parasagittal section
of stage 22 (K) shows strong expression in the eye anlage and in the diencephalon/mesencephalon regions. X-dg expression sites at stage 33 (arrow heads in I):
central nervous system (black), heart (orange), lens epithelium (turquoise), mandibular, hyoid and branchial arches (yellow and green respectively), myotomes
(purple), otic vesicle (red), pronephron (blue). Parasagittal and longitudinal sections of stage 33 showing X-dg transcripts (L) and protein localization (M) in the
myotomes. Transverse section of adult skeletal muscle reveals protein localization in the sarcolemma (N).
Fig. 4. (A) Antero-posterior transverse sections of central nervous system at stage 33. Eye expression at level of ganglion cells layer in the neural retina (G);
and in the optic stalk (H). Abbreviations: die, diencephalon; ep, epiphysis; gcl, ganglion cells layer; h, hypothalamus; mes, mesencephalon; os, optic stalk; rho,
rhombencephalon; st, stomodeum.
Fig. 5. (A) Expression of X-dg as detected in dissected brains of stage 48
embryos by whole-mount in situ hybridization. Lateral view, anterior right
(A); ventral (B); and dorsal (C) view, anterior up.