Differential expression of utrophin and dystrophin in CNS neurons: An in situ hybridization and immunohistochemical study

The cellular distribution of utrophin, the autosomal homologue of dystrophi n, was investigated in developing and adult rat and mouse brain by in situ hybridization and immunohistochemistry. Digoxigenin-labeled cRNA probes com plementary to N-terminal, cad-domain, and C-terminal encoding sequences of utrophin were used to differentiate between full-length and short C-termina l isoforms. Largely overlapping distribution patterns were seen for the thr ee probes in neurons of cerebral cortex, accessory olfactory bulb, and seve ral sensory and motor brainstem nuclei as well as in blood vessels, pia mat er, and choroid plexus. The C-terminal probe was detected in addition in th e main olfactory bulb, striatum, thalamic reticular nucleus, and hypothalam us, suggesting a selective expression of G-utrophin in these neurons. Weste rn blot analysis with isoform-specific antisera confirmed the expression of both full-length and G-utrophin in brain. Immunohistochemically, only full -length utrophin was detected in neurons, in close association with the pla sma membrane. In addition, intense staining was seen in blood vessels, meni nges, and choroid plexus, selectively localized in the basolateral membrane of immunopositive epithelial cells. The expression pattern of utrophin was already established at early postnatal stages and did not change thereafte r. Double-labeling analysis revealed that utrophin and dystrophin are diffe rentially expressed on the cellular and subcellular levels in juvenile and adult brain. Likewise, in mice lacking full-length dystrophin isoforms (mdx mice), no change in utrophin expression and distribution could be detected in brain, although utrophin was markedly up-regulated in muscle cells. The se results suggest that utrophin and dystrophin are independently regulated and have distinct functional roles in CNS neurons. (C) 2000 Wiley-Liss, In c.