Genetic Deletion of the Transcriptional Repressor NFIL3 Enhances Axon Growth In Vitro but Not Axonal Repair In Vivo
PLOS ONE
Authors: van der Kallen, Loek R.; Eggers, Ruben; Ehlert, Erich M.; Verhaagen, Joost; Smit, August B.; van Kesteren, Ronald E.
Abstract
Axonal regeneration after injury requires the coordinated expression of genes in injured neurons. We previously showed that either reducing expression or blocking function of the transcriptional repressor NFIL3 activates transcription of regeneration-associated genes Arg1 and Gap43 and strongly promotes axon outgrowth in vitro. Here we tested whether genetic deletion or dominant-negative inhibition of NFIL3 could promote axon regeneration and functional recovery after peripheral nerve lesion in vivo. Contrary to our expectations, we observed no changes in the expression of regeneration-associated genes and a significant delay in functional recovery following genetic deletion of Nfil3. When NFIL3 function was inhibited specifically in dorsal root ganglia prior to sciatic nerve injury, we observed a decrease in regenerative axon growth into the distal nerve segment rather than an increase. Finally, we show that deletion of Nfil3 changes sciatic nerve lesion-induced expression in dorsal root ganglia of genes that are not typically involved in regeneration, including several olfactory receptors and developmental transcription factors. Together our findings show that removal of NFIL3 in vivo does not recapitulate the regeneration-promoting effects that were previously observed in vitro, indicating that in vivo transcriptional control of regeneration is probably more complex and more robust against perturbation than in vitro data may suggest.
Circadian Polymorphisms in Night Owls, in Bipolars, and in Non-24-Hour Sleep Cycles
PSYCHIATRY INVESTIGATION
Authors: Kripke, Daniel F.; Klimecki, Walter T.; Nievergelt, Caroline M.; Rex, Katharine M.; Murray, Sarah S.; Shekhtman, Tatyana; Tranah, Gregory J.; Loving, Richard T.; Lee, Heon-Jeong; Rhee, Min Kyu; Shadan, Farhad F.; Poceta, J. Steven; Jamil, Shazia M.; Kline, Lawrence E.; Kelsoe, John R.
Abstract
People called night owls habitually have late bedtimes and late times of arising, sometimes suffering a heritable circadian disturbance called delayed sleep phase syndrome (DSPS). Those with DSPS, those with more severe progressively-late non-24-hour sleep-wake cycles, and those with bipolar disorder may share genetic tendencies for slowed or delayed circadian cycles. We searched for polymorphisms associated with DSPS in a case-control study of DSPS research participants and a separate study of Sleep Center patients undergoing polysomnography. In 45 participants, we resequenced portions of 15 circadian genes to identify unknown polymorphism that might be associated with DSPS, non-24-hour rhythms, or bipolar comorbidities. We then genotyped single nucleotide polymorphisms (SNPs) in both larger samples, using Illumina Golden Gate assays. Associations of SNPs with the DSPS phenotype and With the morningness-eveningness parametric phenotype were computed for both samples, then combined for Meta-analyses. Delayed sleep and "eveningness" were inversely associated with loci in circadian genes NFIL3 (rs2482705) and RORC (rs3828057). A group of haplotypes Overlapping BHLHE40 was associated with non-24-hour sleep-wake cycles, and less robustly, with delayed sleep and bipolar disorder (e.g., rs34883305, rs34870629, rs74439275, and rs3750275 were associated with p=4.58E-09, Bonferronip=2.95E-06).Bright light and Melatonin can palliate circadian disorders, and genetics may clarify the underlying circadian photoperiodic Mechanisms. After farther replication and identification of the causal polymorphisms, these findings may point to future treatments for DSPS, non-24-rhour rhythms, and possibly bipolar disorder or depression.