Altered temporal sequence of transcriptional regulators in the generation of human cerebellar granule cells.

Brain development is regulated by conserved transcriptional programs across species, but little is known about the divergent mechanisms that create species-specific characteristics. Among brain regions, human cerebellar histogenesis differs in complexity compared with nonhuman primates and rodents, making it important to develop methods to generate human cerebellar neurons that closely resemble those in the developing human cerebellum. We report a rapid protocol for the derivation of the human ATOH1 lineage, the precursor of excitatory cerebellar neurons, from human pluripotent stem cells (hPSCs).

Novel genetic features of human and mouse Purkinje cell differentiation defined by comparative transcriptomics.

Comparative transcriptomics between differentiating human pluripotent stem cells (hPSCs) and developing mouse neurons offers a powerful approach to compare genetic and epigenetic pathways in human and mouse neurons. To analyze human Purkinje cell (PC) differentiation, we optimized a protocol to generate human pluripotent stem cell-derived Purkinje cells (hPSC-PCs) that formed synapses when cultured with mouse cerebellar glia and granule cells and fired large calcium currents, measured with the genetically encoded calcium indicator jRGECO1a. To directly compare global gene expression of hPSC-PCs with developing mouse PCs, we used translating ribosomal affinity purification (TRAP).

Murine astrotactins 1 and 2 have a similar membrane topology and mature via endoproteolytic cleavage catalyzed by a signal peptidase.

Astrotactin 1 (Astn1) and Astn2 are membrane proteins that function in glial-guided migration, receptor trafficking, and synaptic plasticity in the brain as well as in planar polarity pathways in the skin. Here we used glycosylation mapping and protease protection approaches to map the topologies of mouse Astn1 and Astn2 in rough microsomal membranes and found that Astn2 has a cleaved N-terminal signal peptide, an N-terminal domain located in the lumen of the rough microsomal membranes (topologically equivalent to the extracellular surface in cells), two transmembrane helices, and a large C-terminal lumenal domain. We also found that Astn1 has the same topology as Astn2, but we did not observe any evidence of signal peptide cleavage in Astn1.

N-cadherin provides a and ligand for astrotactin that functions in glial-guided neuronal migration.

Prior studies demonstrate that astrotactin (ASTN1) provides a neuronal receptor for glial-guided CNS migration. Here we report that ASTN1 binds N-cadherin (CDH2) and that the ASTN1:CDH2 interaction supports cell-cell adhesion. To test the function of ASTN1:CDH2 binding in glial-guided neuronal migration, we generated a conditional loss of in cerebellar granule cells and in glia.

ASTN2 modulates synaptic strength by trafficking and degradation of surface proteins.

Surface protein dynamics dictate synaptic connectivity and function in neuronal circuits. , a gene disrupted by copy number variations (CNVs) in neurodevelopmental disorders, including autism spectrum, was previously shown to regulate the surface expression of ASTN1 in glial-guided neuronal migration. Here, we demonstrate that ASTN2 binds to and regulates the surface expression of multiple synaptic proteins in postmigratory neurons by endocytosis, resulting in modulation of synaptic activity.

Bmi1 overexpression in the cerebellar granule cell lineage of mice affects cell proliferation and survival without initiating medulloblastoma formation.

BMI1 is a potent inducer of neural stem cell self-renewal and neural progenitor cell proliferation during development and in adult tissue homeostasis. It is overexpressed in numerous human cancers - including medulloblastomas, in which its functional role is unclear. We generated transgenic mouse lines with targeted overexpression of Bmi1 in the cerebellar granule cell lineage, a cell type that has been shown to act as a cell of origin for medulloblastomas.

Cerebellar stem cells act as medulloblastoma-initiating cells in a mouse model and a neural stem cell signature characterizes a subset of human medulloblastomas.

Cells with stem cell properties have been isolated from various areas of the postnatal mammalian brain, most recently from the postnatal mouse cerebellum. We show here that inactivation of the tumor suppressor genes Rb and p53 in these endogenous neural stem cells induced deregulated proliferation and resistance to apoptosis in vitro. Moreover, injection of these cells into mice formed medulloblastomas.

Loss of Tbx2 delays optic vesicle invagination leading to small optic cups.

Tbx2 is a T-box transcription factor gene that is dynamically expressed in the presumptive retina during optic vesicle invagination. Several findings implicate Tbx2 in cell cycle regulation, including its overexpression in tumours and regulation of proliferation during heart development. We investigated the role of Tbx2 in optic cup formation by analysing mice with a targeted homozygous mutation in Tbx2.

Cerebellar granule cells: insights into proliferation, differentiation, and role in medulloblastoma pathogenesis.

Cerebellar granule cells originate from precursors located in the dorsal region of rhombomere one within the hindbrain of developing embryos. They undergo proliferation for an extensive period well into postnatal stages of development to form the major cell type of the cerebellum, the most populous structure within the mammalian brain. Granule cell development is highly dependent upon the cerebellar environment and contact with neighbouring cells.

A novel mechanistic spectrum underlies glaucoma-associated chromosome 6p25 copy number variation.

The factors that mediate chromosomal rearrangement remain incompletely defined. Among regions prone to structural variant formation, chromosome 6p25 is one of the few in which disease-associated segmental duplications and segmental deletions have been identified, primarily through gene dosage attributable ocular phenotypes. Using array comparative genome hybridization, we studied ten 6p25 duplication and deletion pedigrees and amplified junction fragments from each.

The level of BMP4 signaling is critical for the regulation of distinct T-box gene expression domains and growth along the dorso-ventral axis of the optic cup.

Background: Polarised gene expression is thought to lead to the graded distribution of signaling molecules providing a patterning mechanism across the embryonic eye. Bone morphogenetic protein 4 (Bmp4) is expressed in the dorsal optic vesicle as it transforms into the optic cup. Bmp4 deletions in human and mouse result in failure of eye development, but little attempt has been made to investigate mammalian targets of BMP4 signaling.