SUMMARY The hypothalamus integrates information required for the production of a variety of innate behaviors such as feeding, mating, aggression and predator avoidance. Despite an extensive knowledge of hypothalamic function, how embryonic genetic programs specify circuits that regulate these behaviors remains unknown. Here, we find that in the hypothalamus the developmentally regulated homeodomain-containing transcription factor Dbx1 is required for the generation of specific subclasses of neurons within the lateral hypothalamic area/zona incerta (LH) and the arcuate (Arc) nucleus. Consistent with this specific developmental role, Dbx1 hypothalamic-specific conditional-knockout mice display attenuated responses to predator odor and feeding stressors but do not display deficits in other innate behaviors such as mating or conspecific aggression. Thus, activity of a single developmentally regulated gene, Dbx1, is a shared requirement for the specification of hypothalamic nuclei governing a subset of innate behaviors.

We describe the isolation and characterization of two peptide toxins from Conus ermineus venom targeted to nicotinic acetylcholine receptors (nAChRs). The peptide structures have been confirmed by mass spectrometry and chemical synthesis. In contrast to the 12-18 residue, 4 Cys-containing ␣-conotoxins, the new toxins have 30 residues and 6 Cys residues. The toxins, named ␣A-conotoxins EIVA and EIVB, block both Torpedo and mouse ␣1-containing muscle subtype nAChRs expressed in Xenopus oocytes at low nanomolar concentrations. In contrast to ␣-bungarotoxin, ␣A-EIVA is inactive at ␣7-containing nAChRs even at micromolar concentrations. In this regard, ␣A-EIVA is similar to the previously described ␣-conotoxins (e.g. ␣-MI and ␣-GI) which also selectively target ␣1-versus ␣7-containing nAChRs. However, ␣-MI and ␣-GI discriminate between the ␣/␦ versus ␣/␥ subunit interfaces of the mouse muscle nAChR with 10,000-fold selectivity. In contrast, ␣A-conotoxin EIVA blocks both the ␣/␥ site and ␣/␦ site with equally high affinity but with distinct kinetics. The ␣A-conotoxins thus represent novel probes for the ␣/␥ as well as the ␣/␦ binding sites of the nAChR.

Objective The purpose of this study was to describe the clinical characteristics and natural history of convergence insufficiency (CI) in a population-based cohort of adults. Design Retrospectively reviewed population-based cohort. Participants Adult (≥19 years of age) residents of Olmsted County, Minnesota. Methods The medical records of all adults diagnosed with CI over a 20-year period were retrospectively reviewed. Main outcome measures Clinical characteristics and outcomes for adult-onset convergence insufficiency. Results A total of 118 adults (annual incidence of 8.44 per 100 000 patients older than 19 years) were diagnosed with CI during the 20-year period, comprising 15.7% of all forms of adult-onset strabismus observed in this population. The median age at diagnosis was 68.5 years (range 21.7 to 97.1 years) and 68 (57.6%) were female. The mean initial exodeviation at near was 14.1 PD (range 1 to 30 PD) and 1.7 PD (range 0 to 10 PD) at distance. The Kaplan-Meier rate of exotropia increasing by 7 prism diopters or more at near over time was 4.2% at 5 years, 13.5% at 10 years, and 24.4% at 20 years. Approximately 88% were managed with prisms while less than 5% underwent surgical correction. Conclusions Adult-onset convergence insufficiency comprised approximately 1 in 6 adults who were newly diagnosed with strabismus in this 20-year cohort. There was a significant increase in incidence with increasing age. Nearly one-fourth had an increase of their near exodeviation of at least 7 PD by 20 years after their diagnosis and most patients were managed conservatively.

Gap junction channels can modify their activity in response to cell signaling pathways. Here, we demonstrate that Cx50 coupling, but not Cx46, increased when co-expressed with a constitutively active p110α subunit of PI3K in Xenopus oocytes. In addition, inhibition of PI3K signaling by blocking p110α, or Akt, significantly decreased gap junctional conductance in Cx50 transfected HeLa cells, with no effect on Cx46. Alterations in coupling levels were not a result of Cx50 unitary conductance, suggesting that changes in the number of active channels were responsible. These data indicate that Cx50 is specifically regulated by the PI3K signaling pathway.

Previous approaches to mutation detection in mRNA from the neurofibromatosis 1 (NF1) locus have required the PCR amplification of five or more overlapping cDNA segments to screen the entire 8.5-kb open reading frame (ORF). Systematically, these assays do not detect deletions that span the region of overlap (usually 1-3 exons) of any two consecutive target segments. In such cases, amplification from the mutant region of the disease-causing allele fails because binding sites for the PCR primers are missing, but amplification from the normal allele proceeds, yielding only the normal product. To alleviate this problem, we have developed a protocol to reverse transcribe and amplify the entire protein-coding sequence of NF1 as a single PCR product, starting with total RNA from lymphoblast cell lines or from whole blood. The 8.7-kb RT-PCR product was prepared from nine NF1 patients with known deletions or insertions, ranging in size from a 30-bp deletion within 1 exon to a 2.4-kb deletion that removes 12 exons. Agarose gel analysis of the initial products detected deletions as small as 341 bp. Restriction endonuclease digestion with Asel and Fspl, followed by agarose gel electrophoresis, revealed the predicted abnormal bands in all nine patients. All mutant bands were identified readily by observers with no knowledge of the patients' mutations. This simple assay should detect a great variety of insertion/deletion mutations in the NF1mRNA internal to the primer binding sites, including all possible single and multiple exon dropouts and approximately 30% of all previously reported NF1 mutations.