Brain-derived neurotrophic factor (BDNF) plays a critical role in nervous system

Vector-based RNA interference (RNAi) has emerged as a valuable tool for analysis of gene function. We have developed new RNA polymerase II expression vectors for RNAi, designated SIBR vectors, based upon the non-coding RNA BIC. BIC contains the miR-155 microRNA (miRNA) precursor, and we find that expression of a short region of the third exon of mouse BIC is sufficient to produce miR-155 in mammalian cells. The SIBR vectors use a modified miR-155 precursor stem–loop and flanking BIC sequences to express synthetic miRNAs complementary to target RNAs. Like RNA polymerase III driven short hairpin RNA vectors, the SIBR vectors efficiently reduce target mRNA and protein expression. The synthetic miRNAs can be expressed from an intron, allowing coexpression of a marker or other protein with the miRNAs. In addition, intronic expression of a synthetic miRNA from a two intron vector enhances RNAi. A SIBR vector can express two different miRNAs from a single transcript for effective inhibition of two different target mRNAs. Furthermore, at least eight tandem copies of a synthetic miRNA can be expressed in a polycistronic transcript to increase the inhibition of a target RNA. The SIBR vectors are flexible tools for a variety of RNAi applications.

Messenger RNAs coding for glucocorticoid (GR) and mineralocorticoid (MR) receptor proteins were localized to discrete subfields of the hippocampal formation by in situ hybridization histochemistry, using cRNA probes of approximately equivalent specific activity. Both GR and MR mRNAs were present in all subfields examined; GR mRNA was of greatest abundance in CA1, while MR mRNA was most densely labeled in CA3. In all subfields examined, MR mRNA was considerably more abundant than GR mRNA. Removal of circulating glucocorticoids by adrenalectomy precipitated an up-regulation of GR mRNA in subfields CA1-2 and the dentate gyrus, which was reversed by dexamethasone replacement. High doses of dexamethasone significantly down-regulated GR mRNA in CA3. In contrast, adrenalectomy produced significant up-regulation of MR mRNA only in subfield CA1-2. The data indicate that steroid receptor mRNAs are differentially distributed in hippocampus, and that sensitivity to steroids occurs within defined structural domains of the hippocampal formation.

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Cayman ataxia is a recessive congenital ataxia restricted to one area of Grand Cayman Island. Comparative mapping suggested that the locus on 19p13.3 associated with Cayman ataxia might be homologous to the locus on mouse chromosome 10 associated with the recessive ataxic mouse mutant jittery. Screening genes in the region of overlap identified mutations in a novel predicted gene in three mouse jittery alleles, including the first mouse mutation caused by an Alu-related (B1 element) insertion. We found two mutations exclusively in all individuals with Cayman ataxia. The gene ATCAY or Atcay encodes a neuron-restricted protein called caytaxin. Caytaxin contains a CRAL-TRIO motif common to proteins that bind small lipophilic molecules. Mutations in another protein containing a CRAL-TRIO domain, alpha-tocopherol transfer protein (TTPA), cause a vitamin E-responsive ataxia. Three-dimensional protein structural modeling predicts that the caytaxin ligand is more polar than vitamin E. Identification of the caytaxin ligand may help develop a therapy for Cayman ataxia.