Biology subjects

Pratt, T.

Publications and source records attributed to Pratt, T..

4 recordsLinked to original sources

bioRxiv2022

16p11.2 locus decelerates subpallial maturation and limits variability in human iPSC-derived ventral telencephalic organoids

Inhibitory interneurons regulate the activity of cortical circuitry, and their dysfunction has been implicated in Autism Spectrum Disorder (ASD). 16p11.2 microdeletions are genetically linked to 1% of ASD. However, there have been few studies of the effects of this microdeletion on interneuron development. Using ventral telencephalic organoids derived from human induced pluripotent stem cells, we investigated the effect of this microdeletion on organoid size, progenitor proliferation and organisation into neural rosettes, ganglionic eminence (GE) marker expression at early developmental timepoints and expression of the neuronal marker, NEUN at later stages. Early deletion organoids exhibited significantly greater variations in size with concomitant increases in relative neural rosette area and the expression of the ventral telencephalic marker, COUPTFII, with significantly increased variability in these properties. Cell cycle analysis revealed a significant increase in total cell cycle length caused primarily by an elongated G1-phase, the duration of which also varied significantly more than normal. Late deletion organoids increased their expression of the neuronal marker NEUN. We propose that 16p11.2 microdeletions increase developmental variability and may contribute to ASD aetiology by lengthening the cell cycle of ventral progenitors, promoting premature differentiation into interneurons. Summary StatementUsing 3D-region-specific organoids, we demonstrate that 16p11.2 deletion increases variability and prolongs the cell cycle of human subpallial progenitors by lengthening their G1 phase.

developmental biology↗

bioRxiv2021

Identifying developing interneurons as a potential target for multiple genetic autism risk factors in human and rodent forebrain.

Autism spectrum condition or autism is associated with numerous monogenic and polygenic genetic risk factors including the polygenic 16p11.2 microdeletion. A central question is what neural cells are affected. To systematically investigate we analysed single cell transcriptomes from gestational week (GW) 8-26 human foetal prefrontal cortex and identified a subset of interneurons (INs) first appearing at GW23 with enriched expression of a disproportionately large fraction of risk factor transcripts. This suggests the hypothesis that these INs are disproportionately vulnerable to mutations causing autism. We investigated this in a rat model of the 16p11.2 microdeletion. We found no change in the numbers or position of either excitatory or inhibitory neurons in the somatosensory cortex or CA1 of 16p11.2+/- rats but found that CA1 Sst INs were hyperexcitable with an enlarged axon initial segment, which was not the case for CA1 pyramidal cells. This study prompts deeper investigation of IN development as a convergent target for autism genetic risk factors.

neuroscience↗

bioRxiv2021

Pax6 regulates the morphological and electrophysiological development of mouse prethalamic neurons

Pax6 is a well-known regulator of early neuroepithelial progenitor development. Its constitutive loss has a particularly strong effect on the developing prethalamus, causing it to become extremely hypoplastic. To overcome this difficulty in studying the long-term consequences of Pax6 loss for prethalamic development, we used conditional mutagenesis to delete Pax6 at the onset of neurogenesis and studied the developmental potential of the mutant prethalamic neurons in vitro. We found that Pax6 loss affected their rates of neurite elongation, the location and length of their axon initial segments and their electrophysiological properties. Our results broaden our understanding of the long-term consequences of Pax6 deletion in the developing mouse forebrain, suggesting that it can have cell autonomous effects on the structural and functional development of some neurons. SUMMARY STATEMENTPax6 impacts neurite extension, axon initial segment properties and ability to fire normal action potentials in maturing neurons, revealing actions extending beyond those previously characterized in progenitors.

developmental biology↗

bioRxiv2019

Expression of genes in the 16p11.2 locus during human fetal cortical neurogenesis.

The 593 kbp 16p11.2 copy number variation (CNV) affects the gene dosage of 29 protein coding genes, with heterozygous 16p11.2 microduplication or microdeletion implicated in about 1% of autism spectrum disorder (ASD) cases. The 16p11.2 CNV is frequently associated with macrocephaly or microcephaly indicating early defects of neurogenesis may contribute to subsequent ASD symptoms, but it is unknown which 16p11.2 transcripts are expressed in progenitors and whose levels are likely, therefore, to influence neurogenesis. Analysis of human fetal gene expression data revealed that of all the 16p11.2 transcripts only two, ALDOA and KIF22, are significantly enriched in progenitors. To investigate the role of ALDOA and KIF22 in human cerebral cortex development we used immunohistochemical staining to describe their expression in late first and early second trimester human cerebral cortex. KIF22 protein is restricted to proliferating cells with its levels increasing during the cell cycle and peaking at mitosis. ALDOA protein is expressed in all cell types and does not vary with cell-cycle phase. Our expression analysis suggests the hypothesis that the simultaneous changes in KIF22 and ALDOA dosage in cortical progenitors causes defects in neurogenesis that may contribute to ASD in 16p11.2 CNV patients.

neuroscience↗