Investigation of Postnatal Drug Intervention’s Potential in Rescuing the Symptoms of Fragile X Syndrome in Adult Mice
Background: Previous studies of the frequency of cerebral palsy in the United States have found excess prevalence in black children relative to other groups. Whether the severity of cerebral palsy differs between black and white children has not previously been investigated.
Methods: A population-based surveillance system in 4 regions of the United States identified 476 children with cerebral palsy among 142,338 8-year-old children in 2006. Motor function was rated by the Gross Motor Function Classification System and grouped into 3 categories of severity. We used multiple imputation to account for missing information on motor function and calculated the race-specific prevalence of each cerebral palsy severity level.
Results: The prevalence of cerebral palsy was 3.7 per 1000 black children and 3.2 per 1000 white children (prevalence odds ratio [OR] = 1.2 [95% confidence interval = 1.0-1.4]). When stratified by severity of functional limitation, the racial disparity was present only for severe cerebral palsy (black vs. white prevalence OR=1.7 [1.1-2.4]). The excess prevalence of severe cerebral palsy in black children was evident in term and very preterm birth strata.
Conclusion: Black children in the United States appear to have a higher prevalence of cerebral palsy overall than white children, although the excess prevalence of cerebral palsy in black children is seen only among those with the most severe limitations. Further research is needed to explore reasons for this disparity in functional limitations; potential mechanisms include racial differences in risk factors, access to interventions, and under-identification of mild cerebral palsy in black children.
Fragile X syndrome (FXS) is the most common form of inherited intellectual disability. Previous studies have implicated mGlu5 in the pathogenesis of the disease, but a crucial unanswered question is whether pharmacological mGlu5 inhibition is able to reverse an already established FXS phenotype in mammals. Here we have used the novel, potent, and selective mGlu5 inhibitor CTEP to address this issue in the Fmr1 knockout mouse. Acute CTEP treatment corrects elevated hippocampal long-term depression, protein synthesis, and audiogenic seizures. Chronic treatment that inhibits mGlu5 within a receptor occupancy range of 81% ± 4% rescues cognitive deficits, auditory hypersensitivity, aberrant dendritic spine density, overactive ERK and mTOR signaling, and partially corrects macroorchidism. This study shows that a comprehensive phenotype correction in FXS is possible with pharmacological intervention starting in young adulthood, after development of the phenotype. It is of great interest how these findings may translate into ongoing clinical research testing mGlu5 inhibitors in FXS patients.
The tet-off system has been widely used to create transgenic models of neurological disorders including Alzheimer’s, Parkinson’s, Huntington’s, and prion disease. The utility of this system lies in the assumption that the tetracycline transactivator (TTA) acts as an inert control element and does not contribute to phenotypes under study. Here we report that neuronal expression of TTA can affect hippocampal cytoarchitecture and behavior in a strain-dependent manner. While studying neurodegeneration in two tet-off Alzheimer’s disease models, we unexpectedly discovered neuronal loss within the dentate gyrus of single transgenic TTA controls. Granule neurons appeared most sensitive to TTA exposure during postnatal development, and doxycycline treatment during this period was neuroprotective. TTA-induced degeneration could be rescued by moving the transgene onto a congenic C57BL/6J background and recurred on reintroduction of either CBA or C3H/He backgrounds. Quantitative trait analysis of B6C3 F2 TTA mice identified a region on Chromosome 14 that contains a major modifier of the neurodegenerative phenotype. Although B6 mice were resistant to degeneration, they were not ideal for cognitive testing. F1 offspring of TTA C57BL/6J and 129X1/SvJ, FVB/NJ, or DBA/1J showed improved spatial learning, but TTA expression caused subtle differences in contextual fear conditioning on two of these backgrounds, indicating that strain and genotype can interact independently under different behavioral settings. All model systems have limitations that should be recognized and mitigated where possible; our findings stress the importance of mapping the effects caused by TTA alone when working with tet-off models.