Chimeric and molecular genetic analysis of myelin-deficient (shiverer and mld) mutant mice

cDNA cloning and developmental expression of murine carbonic anhydrase-related proteins VIII, X, and XI

To help understand the biological functions of carbonic anhydrase-related proteins (CA-RPs VIII, X, and XI), we obtained cDNA clones of murine CA-RPs X and XI and studied the tissue distribution of all three CA-RPs and their developmental expression in the murine embryonic brain. The amino acid sequences of murine CA-RPs are highly conserved with their human homologues, indicating a fundamental biological role of CA-RPs. Among a panel of vital organs, the strongest mRNA expression of all three CA-RPs was consistently observed in the brain. Immunohistochemical analysis revealed the expression of all three CA-RPs in the neural cell body and neurites. CA-RP X was also observed in the myelin sheath, as demonstrated using the shiverer demyelinated mouse. In murine embryos, CA-RP VIII and X messages first appeared in the middle of the gestation period, while the CA-RP XI message was seen at an early gestational stage and expressed to a lesser extent as gestation progressed. All CA-RPs were expressed in the neuroprogenitor cells in the subventricular area and subsequently detected in the neural cells migrating to the cortex. Although the exact function of CA-RPs is still undefined, these findings suggest an important role of CA-RPs in the CNS.

Antisense RNA: function and fate of duplex RNA in cells of higher eukaryotes

There is ample evidence that cells of higher eukaryotes express double-stranded RNA molecules (dsRNAs) either naturally or as the result of viral infection or aberrant, bidirectional transcriptional readthrough. These duplex molecules can exist in either the cytoplasmic or nuclear compartments. Cells have evolved distinct ways of responding to dsRNAs, depending on the nature and location of the duplexes. Since dsRNA molecules are not thought to exist naturally within the cytoplasm, dsRNA in this compartment is most often associated with viral infections. Cells have evolved defensive strategies against such molecules, primarily involving the interferon response pathway. Nuclear dsRNA, however, does not induce interferons and may play an important posttranscriptional regulatory role. Nuclear dsRNA appears to be the substrate for enzymes which deaminate adenosine residues to inosine residues within the polynucleotide structure, resulting in partial or full unwinding. Extensively modified RNAs are either rapidly degraded or retained within the nucleus, whereas transcripts with few modifications may be transported to the cytoplasm, where they serve to produce altered proteins. This review summarizes our current knowledge about the function and fate of dsRNA in cells of higher eukaryotes and its potential manipulation as a research and therapeutic tool.