Suchergebnisse

In the inner ear, sensory versus neuronal specification is achieved through few well-defined bHLH transcription factors. However, the molecular mechanisms regulating the generation of the appropriate cell type in the correct place and at the correct time are not completely understood yet. Various studies have shown that hair cell- and neuron-specifying genes partially overlap in the otic territory, suggesting that mutual interactions among these bHLH factors could direct the generation of the two cell types from a common neurosensory progenitor. Although there is little evidence for a clonal relationship between macular hair cells and sensory neurons, the existence of a single progenitor able to give both sensory and neuronal cell types remains an open question. Here, we identified a population of common neurosensory progenitors in the zebrafish inner ear and studied the proneural requirement for cell fate decision within this population. Expression analysis reveals that proneural genes for hair cells and neurons overlap within the posteromedial otic epithelium. Combined results from single-cell lineage and functional studies on neurog1 and neuroD1 further demonstrate the following: (1) in the anterior region of the ear, neuronal and sensory lineages have already segregated at the onset of proneural gene expression and are committed to a given fate very early; (2) in contrast, the posteromedial part of the ear harbors a population of common progenitors giving both neurons and hair cells until late stages; and finally (3) neuroD1 is required within this pool of bipotent progenitors to generate the hair cell fate. ; The work was funded by Ministry of Science and Innovation Grant BFU2009-07010 (C.P.). D.S. was a recipient of a postdoctoral Juan de la Cierva contract (Ministry of Science and Innovation) and S.D. of a predoctoral FI fellowship (Agency for Management of University and Research Grants, Government of Catalonia)

Sphingolipid imbalance is the culprit in a variety of neurological diseases, some affecting the myelin sheath. We have used whole-exome sequencing in patients with undetermined leukoencephalopathies to uncover the endoplasmic reticulum lipid desaturase DEGS1 as the causative gene in 19 patients from 13 unrelated families. Shared features among the cases include severe motor arrest, early nystagmus, dystonia, spasticity, and profound failure to thrive. MRI showed hypomyelination, thinning of the corpus callosum, and progressive thalamic and cerebellar atrophy, suggesting a critical role of DEGS1 in myelin development and maintenance. This enzyme converts dihydroceramide (DhCer) into ceramide (Cer) in the final step of the de novo biosynthesis pathway. We detected a marked increase of the substrate DhCer and DhCer/Cer ratios in patients' fibroblasts and muscle. Further, we used a knockdown approach for disease modeling in Danio rerio, followed by a preclinical test with the first-line treatment for multiple sclerosis, fingolimod (FTY720, Gilenya). The enzymatic inhibition of Cer synthase by fingolimod, 1 step prior to DEGS1 in the pathway, reduced the critical DhCer/Cer imbalance and the severe locomotor disability, increasing the number of myelinating oligodendrocytes in a zebrafish model. These proof-of-concept results pave the way to clinical translation. ; This study was supported by the ISCIII (FIS PI14/00581) (cofunded by the European Regional Development Fund); 'La Marató de TV3' Foundation 345/C/2014 (to AP, C. Casasnovas, and CP); the Hesperia Foundation and CIBER on Rare Diseases (CIBERER) (ACCI14-759) and the Secretariat for Universities and Research of the Ministry of Business and Knowledge of the Government of Catalonia (2017SGR1206) to AP; the Spanish Ministry of Economy and Competitiveness (MINECO-FEDER) (BFU2015-67400-P) to CP; the Spanish Institute for Health Carlos III (Miguel Servet program CPII16/00016) to SF; CIBERER to NL and MR; and a predoctoral fellowship awarded to DP from the Government of Catalonia through L′Agència de Gestió d'Ajuts Universitaris i de Recerca (AGAUR; FI-DGR 2014). XJ acknowledges a Sara Borrell postdoctoral fellowship from Instituto de Salud Carlos III.