Transmitters and Pathways Mediating Inhibition of Spinal Itch-Signaling Neurons by Scratching and Other Counterstimuli

Scratching relieves itch, but the underlying neural mechanisms are poorly understood. We presently investigated a role for the inhibitory neurotransmitters GABA and glycine in scratch-evoked inhibition of spinal itch-signaling neurons in a mouse model of chronic dry skin itch. Superficial dorsal horn neurons ipsilateral to hindpaw dry skin treatment exhibited a high level of spontaneous firing that was significantly attenuated by cutaneous scratching, pinch and noxious heat. Scratch-evoked inhibition was nearly abolished by spinal delivery of the glycine antagonist, strychnine, and was markedly attenuated by respective GABAA and GABAB antagonists bicuculline and saclofen. Scratch-evoked inhibition was also significantly attenuated (but not abolished) by interruption of the upper cervical spinal cord, indicating the involvement of both segmental and suprasegmental circuits that engage glycine- and GABA-mediated inhibition of spinal itch-signaling neurons by noxious counterstimuli

ROTUNDIFOLIA4 Regulates Cell Proliferation Along the Body Axis in Arabidopsis Shoot

Molecular genetics has been successful in identifying leaf- size regulators such as transcription factors, phytohormones, and signal molecules. Among them, a ROTUNDIFOLIA4-LIKE/DEVIL (RTFL/DVL) family of Arabidopsis, genes encoding peptides with no secretion-signal sequence, is unique in that their overexpressors have a reduced number of leaf cells specifically along the proximodistal axis. However, because the RTFL/DVL lack any obvious homology with functionally identified domains, and because of genetic redundancy among RTFL/DVL, their molecular and developmental roles are unclear. In this study we focused on one member in the family, ROTUNDIFOLIA4 (ROT4), and identified the core functional region within it and we found no proteolytic processing in planta. Developmental analysis of leaf primordia revealed that ROT4 overexpression reduces the meristematic zone size within the leaf blade. Moreover, induced local overexpression demonstrated that ROT4 acts as a regulator of the leaf shape via a change in positional cue along the longitudinal axis. Similarly, ROT4 overexpression results in a protrusion of the main inflorescence stem, again indicating a change in positional cue along the longitudinal axis. These results suggest that ROT4 affects the positional cue and cell proliferation along the body axis

The DSIF Subunits Spt4 and Spt5 Have Distinct Roles at Various Phases of Immunoglobulin Class Switch Recombination

Class-switch recombination (CSR), induced by activation-induced cytidine deaminase (AID), can be divided into two phases: DNA cleavage of the switch (S) regions and the joining of the cleaved ends of the different S regions. Here, we show that the DSIF complex (Spt4 and Spt5), a transcription elongation factor, is required for CSR in a switch-proficient B cell line CH12F3-2A cells, and Spt4 and Spt5 carry out independent functions in CSR. While neither Spt4 nor Spt5 is required for transcription of S regions and AID, expression array analysis suggests that Spt4 and Spt5 regulate a distinct subset of transcripts in CH12F3-2A cells. Curiously, Spt4 is critically important in suppressing cryptic transcription initiating from the intronic Sμ region. Depletion of Spt5 reduced the H3K4me3 level and DNA cleavage at the Sα region, whereas Spt4 knockdown did not perturb the H3K4me3 status and S region cleavage. H3K4me3 modification level thus correlated well with the DNA breakage efficiency. Therefore we conclude that Spt5 plays a role similar to the histone chaperone FACT complex that regulates H3K4me3 modification and DNA cleavage in CSR. Since Spt4 is not involved in the DNA cleavage step, we suspected that Spt4 might be required for DNA repair in CSR. We examined whether Spt4 or Spt5 is essential in non-homologous end joining (NHEJ) and homologous recombination (HR) as CSR utilizes general repair pathways. Both Spt4 and Spt5 are required for NHEJ and HR as determined by assay systems using synthetic repair substrates that are actively transcribed even in the absence of Spt4 and Spt5. Taken together, Spt4 and Spt5 can function independently in multiple transcription-coupled steps of CSR