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Within the Drosophila embryo, two related bHLH-PAS proteins, Single-minded and Trachealess, control development of the central nervous system midline and the trachea, respectively. These two proteins are bHLH-PAS transcription factors and independently form heterodimers with another bHLH-PAS protein, Tango. During early embryogenesis, expression of Single-minded is restricted to the midline and Trachealess to the trachea and salivary glands, whereas Tango is ubiquitously expressed. Both Single-minded/Tango and Trachealess/Tango heterodimers bind to the same DNA sequence, called the CNS midline element (CME) within cis-regulatory sequences of downstream target genes. While Single-minded/Tango and Trachealess/Tango activate some of the same genes in their respective tissues during embryogenesis, they also activate a number of different genes restricted to only certain tissues. The goal of this research is to understand how these two related heterodimers bind different enhancers to activate different genes, thereby regulating the development of functionally diverse tissues. Existing data indicates that Single-minded and Trachealess may bind to different co-factors restricted to various tissues, causing them to interact with the CME only within certain sequence contexts. This would lead to the activation of different target genes in different cell types. To understand how the context surrounding the CME is recognized by different bHLH-PAS heterodimers and their co-factors, we identified and analyzed novel enhancers that drive midline and/or tracheal expression and compared them to previously characterized enhancers. In addition, we tested expression of synthetic reporter genes containing the CME flanked by different sequences. Taken together, these experiments identify elements overrepresented within midline and tracheal enhancers and suggest that sequences immediately surrounding a CME help dictate whether a gene is expressed in the midline or trachea. [ABSTRACT FROM AUTHOR]

Neuronal nicotinic acetylcholine receptors (nAChRs) are involved in a variety of physiological processes, including cognition and development. Dysfunctions in nAChRs have been linked to Alzheimer’s disease (AD), a human neurological disorder that is the leading cause of dementia. AD is characterized by an increasing loss of cognitive function, nAChRs, cholinergic neurons, and choline acetyltransferase activity. A major hallmark of AD is the presence of extracellular neuritic plaques composed of the β-amyloid (Aβ1–42) peptide; however, the link between Aβ1–42 and the loss of cognitive function has not been established. Many groups have shown direct interactions between Aβ1–42 and nAChR function, however, with differing results. For example, in rat hippocampal CA1 interneurons in slices, we found that Aβ1–42 inhibits nAChR channels directly, and non-α7 receptors were more sensitive to block than α7 receptors. However, some groups have found that α7 subtypes were potently blocked by Aβ1–42, whereas other groups reported that Aβ1–42 can activate nAChRs (i.e., both α7 and non-α7 subtypes). To further investigate the link between nAChR function and Aβ1–42, we expressed various subtypes of nAChRs in Xenopus oocytes (e.g., α4β2, α2β2, α4α5β2, and α7) and found that Aβ1–42 blocked these various non-α7 nAChRs, without any effect on α7 nAChRs. Furthermore, none of these channels was activated by Aβ1–42. The relative block by Aβ1–42 was dependent on the subunit makeup and apparent stoichiometry of these receptors. These data further support our previous findings that Aβ1–42 directly and preferentially inhibits non-α7 nAChRs. [ABSTRACT FROM AUTHOR]