BMP signalling facilitates transit amplification in the developing chick and human cerebellum

The external granule layer (EGL) is a transient proliferative layer that gives rise to cerebellar granule cell neurons. Extensive EGL proliferation characterises the foliated structure of amniote cerebella, but the factors that regulate EGL formation, amplification within it, and differentiation from it, are incompletely understood. Here, we characterise bone morphogenic protein (BMP) signalling during cerebellar development in chick and human and show that while in chick BMP signalling correlates with external granule layer formation, in humans BMP signalling is maintained throughout the external granule layer after the onset of foliation. We also show via Immunohistochemical labelling of phosphorylated Smad1/5/9 the comparative spatiotemporal activity of BMP signalling in chick and human. Using in-ovo electroporation in chick, we demonstrate that BMP signalling is necessary for subpial migration of granule cell precursors and hence the formation of the external granule layer (EGL) prior to transit amplification. However, altering BMP signalling does not block the formation of mature granule neurons but significantly disrupts that pattern of morphological transitions that accompany transit amplification. Our results elucidate two key, temporally distinct roles for BMP signalling in vivo in organising first the assembly of the EGL from the rhombic lip and subsequently the tempo of granule neuron production within the EGL

Supplementary Material for: A Genome-Wide Test of the Differential Susceptibility Hypothesis Reveals a Genetic Predictor of Differential Response to Psychological Treatments for Child Anxiety Disorders

Background: The differential susceptibly hypothesis suggests that certain genetic variants moderate the effects of both negative and positive environments on mental health and may therefore be important predictors of response to psychological treatments. Nevertheless, the identification of such variants has so far been limited to preselected candidate genes. In this study we extended the differential susceptibility hypothesis from a candidate gene to a genome-wide approach to test whether a polygenic score of environmental sensitivity predicted response to cognitive behavioural therapy (CBT) in children with anxiety disorders. Methods: We identified variants associated with environmental sensitivity using a novel method in which within-pair variability in emotional problems in 1,026 monozygotic twin pairs was examined as a function of the pairs' genotype. We created a polygenic score of environmental sensitivity based on the whole-genome findings and tested the score as a moderator of parenting on emotional problems in 1,406 children and response to individual, group and brief parent-led CBT in 973 children with anxiety disorders. Results: The polygenic score significantly moderated the effects of parenting on emotional problems and the effects of treatment. Individuals with a high score responded significantly better to individual CBT than group CBT or brief parent-led CBT (remission rates: 70.9, 55.5 and 41.6%, respectively). Conclusions: Pending successful replication, our results should be considered exploratory. Nevertheless, if replicated, they suggest that individuals with the greatest environmental sensitivity may be more likely to develop emotional problems in adverse environments but also benefit more from the most intensive types of treatment