Biology subjects

Shao, D. D.

Publications and source records attributed to Shao, D. D..

3 recordsLinked to original sources

bioRxiv2024

Perinatal Reduction of Genetically Aberrant Neurons from Human Cerebral Cortex

Human neurons are postmitotic and long-lived, requiring precise genomic regulation to maintain function over a lifetime. Normal neuronal function is highly dependent on gene dosage, with copy number variants (CNVs) and heterozygous point mutations associated with a host of neurodevelopmental and neuropsychiatric conditions [1-5]. Here, we investigated the landscape of somatic CNVs arising in fetal human brains, and how they change over development, to understand the processes that generate normal neuronal genomes. We sequenced 2,158 single neurons from human postmortem brain using two distinct single cell whole genome sequencing (scWGS) approaches. Tn5-transposase based (TbA) scWGS of 1,327 neurons from 16 individuals ranging in age from gestational week 14 to 90 years old resulted in 8,765 CNVs. Primary template amplification (PTA) was used to assess for CNV from 831 neurons from 12 individuals. Up to 46% of neurons in prenatal cortex showed aberrant genomes, characterized by widespread CNVs of multiple chromosomes, but this proportion reduces by 4-5 fold after birth across the two scWGS approaches (p=7.5x10-6, Fisher meta-analysis). We identified micronuclei in the developing cortex in situ, reflecting chromosomal material missegregated during neurodevelopment [6-8]. Neurons with widespread CNVs were eliminated in the perinatal period, while neurons with smaller CNV burden slowly declined during postnatal aging. CNVs in surviving neurons were depleted for genes that are dosage-sensitive or involved in neurodevelopmental disorders (p<0.05), suggesting selective elimination of neurons with CNVs involving these critical genes. We surveyed 44,861 nuclei with 10X Genomics scATAC/RNAseq and determined that neurons with high CNV burdens also showed abnormal expression of synaptic gene sets, suggesting that abnormal synaptic gene regulation contributes to neuronal elimination. Elimination of defective neuronal genomes during synaptogenesis may represent a critical process of genome quality control and a vulnerable target of factors that contribute to neurodevelopmental disease.

neuroscience↗

bioRxiv2024

Spatial Single-cell Analysis Decodes Cortical Layer and Area Specification

The human cerebral cortex, pivotal for advanced cognitive functions, is composed of six distinct layers and dozens of functionally specialized areas1,2. The layers and areas are distinguished both molecularly, by diverse neuronal and glial cell subtypes, and structurally, through intricate spatial organization3,4. While single-cell transcriptomics studies have advanced molecular characterization of human cortical development, a critical gap exists due to the loss of spatial context during cell dissociation5,6,7,8. Here, we utilized multiplexed error-robust fluorescence in situ hybridization (MERFISH)9, augmented with deep-learning-based cell segmentation, to examine the molecular, cellular, and cytoarchitectural development of human fetal cortex with spatially resolved single-cell resolution. Our extensive spatial atlas, encompassing 16 million single cells, spans eight cortical areas across four time points in the second and third trimesters. We uncovered an early establishment of the six-layer structure, identifiable in the laminar distribution of excitatory neuronal subtypes by mid-gestation, long before the emergence of cytoarchitectural layers. Notably, while anterior-posterior gradients of neuronal subtypes were generally observed in most cortical areas, a striking exception was the sharp molecular border between primary (V1) and secondary visual cortices (V2) at gestational week 20. Here we discovered an abrupt binary shift in neuronal subtype specification at the earliest stages, challenging the notion that continuous morphogen gradients dictate mid-gestation cortical arealization6,10. Moreover, integrating single-nuclei RNA-sequencing and in situ whole transcriptomics revealed an early upregulation of synaptogenesis in V1-specific Layer 4 neurons, suggesting a role of synaptogenesis in this discrete border formation. Collectively, our findings underscore the crucial role of spatial relationships in determining the molecular specification of cortical layers and areas. This work not only provides a valuable resource for the field, but also establishes a spatially resolved single-cell analysis paradigm that paves the way for a comprehensive developmental atlas of the human brain.

neuroscience↗

bioRxiv2024

High-resolution detection of copy number alterations in single cells with HiScanner

Improvements in single-cell whole-genome sequencing (scWGS) assays have enabled detailed characterization of somatic copy number alterations (CNAs) at the single-cell level. Yet, current computational methods are mostly designed for detecting chromosome-scale changes in cancer samples with low sequencing coverage. Here, we introduce HiScanner (High-resolution Single-Cell Allelic copy Number callER), which combines read depth, B-allele frequency, and haplotype phasing to identify CNAs with high resolution. In simulated data, HiScanner consistently outperforms state-of-the-art methods across various CNA types and sizes. When applied to high-coverage scWGS data from 65 cells across 11 neurotypical human brains, HiScanner shows a superior ability to detect smaller CNAs, uncovering distinct CNA patterns between neurons and oligodendrocytes. We also generated low-coverage scWGS data from 179 cells sampled from the same meningioma patient at two time points. For this serial dataset, integration of CNAs with point mutations revealed evolutionary trajectories of tumor cells. These findings show that HiScanner enables accurate characterization of frequency, clonality, and distribution of CNAs at the single-cell level in both non-neoplastic and neoplastic cells.

genomics↗