Biology subjects

Bayin, N. S.

Publications and source records attributed to Bayin, N. S..

3 recordsLinked to original sources

bioRxiv2018

Multiple modes of PRC2 inhibition elicit global chromatin alterations in H3K27M pediatric glioma

A methionine substitution at lysine 27 on histone H3 variants (H3K27M) characterizes ~80% of diffuse intrinsic pontine gliomas (DIPG) and inhibits PRC2 in a dominant negative fashion. Yet, the mechanisms for this inhibition and abnormal epigenomic landscape have not been resolved. Using quantitative proteomics, we discovered that robust PRC2 inhibition requires levels of H3K27M greatly exceeding those of PRC2, seen in DIPG. While PRC2 inhibition requires interaction with H3K27M, we found this interaction on chromatin is transient with PRC2 largely being released from H3K27M. Unexpectedly, inhibition persisted even after PRC2 dissociated from H3K27M-chromatin suggesting a lasting impact on PRC2. Furthermore, allosterically activated PRC2 is particularly sensitive to K27M leading to a failure to spread H3K27me3 at distinct foci. In turn, levels of Polycomb antagonists such as H3K36me2 are elevated suggesting a more global, downstream effect on the epigenome. Together, these findings reveal the conditions required for H3K27M-mediated PRC2 inhibition and reconcile seemingly paradoxical effects of H3K27M on PRC2 recruitment and activity.

molecular biology↗

bioRxiv2018

Cerebellar nuclei neurons dictate growth of the cortex through developmental scaling of presynaptic Purkinje cells

Efficient function of neural systems requires the production of specific cell types in the correct proportions. Here we report that reduction of the earliest born neurons of the cerebellum, excitatory cerebellar nuclei neurons (eCN), results in a subsequent reduction in growth of the cerebellar cortex due to an accompanying loss of their presynaptic target Purkinje cells. Conditional knockout of the homeobox genes En1 and En2 (En1/2) in the rhombic lip-derived eCN and granule cell precursors leads to embryonic loss of a subset of medial eCN and cell non-autonomous and location specific loss of Purkinje cells, with subsequent proportional scaling down of cortex growth. We propose that subsets of eCN dictate the survival of their specific Purkinje cell partners, and in turn sonic hedgehog secreted by Purkinje cells scales the expansion of granule cells and interneurons to produce functional local circuits and the proper folded morphology of the cerebellum.

developmental biology↗

bioRxiv2018

Age-dependent dormant resident progenitors are stimulated by injury to regenerate Purkinje neurons

Outside of the neurogenic niches of the brain, postmitotic neurons have not been found to undergo efficient regeneration. Here we demonstrate that Purkinje cells (PCs), which are born at midgestation and are crucial for both development and function of cerebellar circuits, are rapidly and fully regenerated following their ablation at birth. New PCs are produced by a previously unidentified progenitor population and support normal cerebellum development. The number of PC progenitors and their regenerative capacity, however, diminish soon after birth, and consequently PCs are poorly replenished when ablated at postnatal day 5. Nevertheless, the PC-depleted cerebella reach a normal size by increasing cell size, but scaling of neuron types is disrupted and cerebellar function is impaired. Our findings thus provide a new paradigm in the field of neuron regeneration by identifying a unipotent neural progenitor that buffers against perinatal brain injury in a stage-dependent process.\n\nOne sentence summaryInjury induces a dormant progenitor population present at birth to regenerate cerebellar neurons in a time-dependent manner.

developmental biology↗