Identification of differentially expressed genes in the developing mouse inferior colliculus

Bilirubin-Induced Transcriptomic Imprinting in Neonatal Hyperbilirubinemia

Recent findings indicated aberrant epigenetic control of the central nervous system (CNS) development in hyperbilirubinemic Gunn rats as an additional cause of cerebellar hypoplasia, the landmark of bilirubin neurotoxicity in rodents. Because the symptoms in severely hyperbilirubinemic human neonates suggest other regions as privileged targets of bilirubin neurotoxicity, we expanded the study of the potential impact of bilirubin on the control of postnatal brain development to regions correlating with human symptoms. Histology, transcriptomic, gene correlation, and behavioral studies were performed. The histology revealed widespread perturbation 9 days after birth, restoring in adulthood. At the genetic level, regional differences were noticed. Bilirubin affected synaptogenesis, repair, differentiation, energy, extracellular matrix development, etc., with transient alterations in the hippocampus (memory, learning, and cognition) and inferior colliculi (auditory functions) but permanent changes in the parietal cortex. Behavioral tests confirmed the presence of a permanent motor disability. The data correlate well both with the clinic description of neonatal bilirubin-induced neurotoxicity, as well as with the neurologic syndromes reported in adults that suffered neonatal hyperbilirubinemia. The results pave the way for better deciphering the neurotoxic features of bilirubin and evaluating deeply the efficacy of new therapeutic approaches against the acute and long-lasting sequels of bilirubin neurotoxicity.

Developmental changes of the protein repertoire in the rat auditory brainstem: a comparative proteomics approach in the superior olivary complex and the inferior colliculus with DIGE and iTRAQ

Protein profiles of developing neural circuits undergo manifold changes. The aim of this proteomic analysis was to quantify postnatal changes in two auditory brainstem areas in a comparative approach. Protein samples from the inferior colliculus (IC) and the superior olivary complex (SOC) were obtained from neonatal (P4) and young adult (P60) rats. The cytosolic fractions of both areas were examined by 2-D DIGE, and the plasma membrane-enriched fraction of the IC was analyzed via iTRAQ. iTRAQ showed a regulation in 34% of the quantified proteins. DIGE revealed 12% regulated spots in both the SOC and IC and, thus, numeric congruency. Although regulation in KEGG pathways displayed a similar pattern in both areas, only 13 of 71 regulated DIGE proteins were regulated in common, implying major area-specific differences. 89% of regulated glycolysis/gluconeogenesis and citrate cycle proteins were up-regulated in the SOC or IC, suggesting a higher energy demand in adulthood. Seventeen cytoskeleton proteins were regulated, consistent with complex morphological reorganization between P4 and P60. Fourteen were uniquely regulated in the SOC, providing further evidence for area-specific differences. Altogether, we provide the first elaborate catalog of proteins involved in auditory brainstem development, several of them possibly of particular developmental relevance.

Is otospiralin inner ear specific? Evidence for its expression in mouse brain

The small protein otospiralin has initially been identified as an inner ear specific molecule. However, compelling evidence from high throughput sequencing projects suggested that otospiralin is likely expressed in the central nervous system. Here, we tested this hypothesis using a combination of molecular biology, immunological, and histological techniques, and found that otospiralin is expressed in numerous regions of the central nervous system in mouse. In situ hybridization and immunohistochemistry revealed that otospiralin is widely expressed in neuronal cell bodies and glia. Ultrastructural observations in the cerebral cortex located the small protein in close proximity to membranous organelles in perikarya, the inner face of post-synaptic neuronal membranes, and in astrocytic processes. These results are in agreement with the predicted structure of the protein which revealed a single N-terminal transmembrane helix domain followed by a C-terminus cytosolic tail. Interestingly, 2 weeks after a mechanical trauma in the cerebral cortex, otospiralin expression increased in reactive astrocytes located within the vicinity of the site of injury, but not in neurons. Collectively, our observations suggest that otospiralin is possibly involved in signaling pathways, and could play a role in repair mechanisms subsequent to an injury in the central nervous system.