The Enhancer of split transcription factor Her8a is a novel dimerisation partner for Her3 that controls anterior hindbrain neurogenesis in zebrafish

International audienceBACKGROUND: Neurogenesis control and the prevention of premature differentiation in the vertebrate embryo are crucial processes, allowing the formation of late-born cell types and ensuring the correct shape and cytoarchitecture of the brain. Members of the Hairy/Enhancer of Split (Hairy/E(spl)) family of bHLH-Orange transcription factors, such as zebrafish Her3, 5, 9 and 11, are implicated in the local inhibition of neurogenesis to maintain progenitor pools within the early neural plate. To better understand how these factors exert their inhibitory function, we aimed to isolate some of their functional interactors. RESULTS: We used a yeast two-hybrid screen with Her5 as bait and recovered a novel zebrafish Hairy/E(spl) factor--Her8a. Using phylogenetic and synteny analyses, we demonstrate that her8a evolved from an ancient duplicate of Hes6 that was recently lost in the mammalian lineage. We show that her8a is expressed across the mid- and anterior hindbrain from the start of segmentation. Through knockdown and misexpression experiments, we demonstrate that Her8a is a negative regulator of neurogenesis and plays an essential role in generating progenitor pools within rhombomeres 2 and 4--a role resembling that of Her3. Her8a co-purifies with Her3, suggesting that Her8a-Her3 heterodimers may be relevant in this domain of the neural plate, where both proteins are co-expressed. Finally, we demonstrate that her8a expression is independent of Notch signaling at the early neural plate stage but that SoxB factors play a role in its expression, linking patterning information to neurogenesis control. Overall, the regulation and function of Her8a differ strikingly from those of its closest relative in other vertebrates--the Hes6-like proteins. CONCLUSIONS: Our results characterize the phylogeny, expression and functional interactions involving a new Her factor, Her8a, and highlight the complex interplay of E(spl) proteins that generates the neurogenesis pattern of the zebrafish early neural plate

Association of Intrathecal Immunoglobulin G Synthesis With Disability Worsening in Multiple Sclerosis

IMPORTANCE Reliable biomarkers associated with disability worsening in multiple sclerosis (MS) are still needed. OBJECTIVE To determine a possible association of intrathecal IgG synthesis and early disability worsening as measured by Expanded Disability Status Scale (EDSS) scoring in patients with relapsing-remitting MS or clinically isolated syndrome. DESIGN, SETTING, AND PARTICIPANTS Cerebrospinal fluid measurements and clinical data from the observational longitudinal German national multiple sclerosis cohort were analyzed. Patients were recruited between August 2010 and November 2015 from 18 centers. Data analysis was completed from August 2018 to December 2018. EXPOSURE Patients were offered standard immunotherapies per national treatment guidelines. MAIN OUTCOMES AND MEASURES A possible association between intrathecal IgG synthesis and risk of EDSS worsening 4 years after study inclusion was tested as the primary end point by multivariable binomial regression analysis. Kaplan-Meier analysis with a log-rank test was used to assess the association of intrathecal IgG synthesis with the time to EDSS worsening. Associations between intrathecal IgM or IgA synthesis and other cerebrospinal fluid parameters and EDSS worsening were analyzed as exploratory end points. Data collection began before the hypotheses were formulated. RESULTS Of all 1376 patients in the German Competence Network of Multiple Sclerosis cohort, 703 patients were excluded owing to missing cerebrospinal fluid or EDSS data. Of the 673 included patients, 459 (68.2%) were women. The mean (SD) age at baseline was 34 (10) years. Intrathecal IgG synthesis was associated with a higher risk of EDSS worsening after 4 years (odds ratio, 2.02 [95% CI, 1.15-3.58]; P=.01), independent of the occurrence of relapses and disease-modifying therapy. Additionally, intrathecal IgG synthesis was associated with earlier EDSS worsening; 4 years after study entry, worsening occurred in 28.4% (95% CI, 22.7%-34.1%) and 18.1% (95% CI, 12.4%-23.9%) of patients with and without intrathecal IgG synthesis, respectively. No association of other routine cerebrospinal fluid parameters with EDSS worsening was found. CONCLUSIONS AND RELEVANCE Patients with new diagnoses of relapsing-remitting multiple sclerosis or clinically isolated syndrome with intrathecal IgG synthesis had a higher risk of and shorter time to EDSS worsening across a 4-year period of follow-up. Intrathecal IgG synthesis is a potentially useful marker for disability worsening in patients with multiple sclerosis and may be useful for early treatment decisions