Lentiviral CRISPRa/i screen for targeted activation or repression of SNRPN in SNRPN-GFP human iPSCs. In brief, cells are transduced with a gRNA library containing mCherry and PuroR genes, expanded for 9-14 days, and sorted on high/low GFP expression.

Cohesin orchestrates gene expression via three-dimensional chromosome folding. Genes encoding cohesin and cohesin loaders have been associated with Mendelian disorders, whereas genes encoding cohesin release factors, including WAPL and its binding partners PDS5A and PDS5B, have not. We explored the relevance of cohesin release factors in Mendelian disease by phenotyping individuals with heterozygous predicted damaging variants in WAPL (n = 27), PDS5A (n = 8), and PDS5B (n = 8), by modeling WAPL deficiency in human cells and mice, and by aggregating disease association statistics from consortia studies. We identified a WAPL-related disorder featuring developmental delay, intellectual disability, and risk of other developmental anomalies. Similarities between individuals with damaging WAPL variants and those with large, recurrent 10q22.3q23.2 (10q) deletions encompassing WAPL nominate WAPL as a driver gene within this genomic disorder region. While individuals with PDS5A or PDS5B variants exhibited features of developmental disorders, neither cohort-based statistics nor subject phenotyping associated these genes with specific phenotypes. We used CRISPR to generate truncating variants in WAPL and 10q deletion or duplication in human induced pluripotent stem cells (iPSCs) and induced neurons. Transcriptomics identified significant overlap between WAPL haploinsufficiency and 10q deletion differentially expressed genes. Mice with 50% Wapl expression exhibited mild deficits of growth and learning/memory, whereas those with 25% residual Wapl displayed birth defects and postnatal lethality, revealing a dosage liability threshold below the level of heterozygosity. In summary, we delineated a genetic condition caused by cohesin release factor deficiency, nominated WAPL as a driver gene within a genomic disorder region, and further illuminated dosage sensitivity of human cohesin.

This protocol describes methods for CUT&RUN for H3K4me3.

Cohesin is a fundamental genome-organizing complex that orchestrates three-dimensional chromosome folding and gene expression via DNA loop extrusion. Alterations to genes encoding cohesin subunits and cohesin loaders cause Mendelian disorders, including Cornelia de Lange syndrome (CdLS). By contrast, disruption of factors that remove cohesin from DNA, including WAPL and its binding partners PDS5A and PDS5B, have not yet been associated with human disease. Here, we explored the relevance of these cohesin release factors in Mendelian disease by establishing a rare disease cohort of deeply phenotyped individuals with heterozygous, predicted damaging variants in WAPL (n=27), PDS5A (n=8), and PDS5B (n=8), by modeling WAPL deficiency in human cell lines and mice, and by aggregating rare disease association statistics from consortia studies. We identified a WAPL-related disorder characterized by developmental delay, intellectual disability, and risk of other developmental anomalies including clubfoot. Similarities between individuals with damaging WAPL variants and those with large, recurrent 10q22.3q23.2 (10q) deletions (which encompass WAPL) nominate WAPL as a driver gene within this genomic disorder region. While carriers of PDS5A or PDS5B variants exhibited features of developmental disorders, neither cohort-based statistics nor case phenotyping associated these genes with specific phenotypes. We used CRISPR engineering to generate truncating variants in WAPL, as well the 7.8 Mb 10q deletion or duplication in human iPSCs and induced neurons. Transcriptomic analyses identified differentially expressed genes in both models, with highly significant overlap between WAPL haploinsufficiency and 10q deletion signatures. Mice with 50% residual Wapl expression exhibited mild deficits of growth and learning/memory, whereas those with 25% residual Wapl expression displayed birth defects and postnatal lethality, revealing a dosage liability threshold below the level of heterozygosity. In summary, we delineated a novel genetic condition caused by cohesin release factor deficiency, nominated WAPL as a driver gene within a genomic disorder region, and further illuminated dosage sensitivity of human cohesin.

This protocol describes methods for targeted bisulfite sequencing within the PWS locus.

This protocol describes methods for generating excitatory neurons from iPSCs using transduction of virus expressing inducible neurogenin-2 (Ngn2).

Epigenome editing with DNA-targeting technologies such as CRISPR-dCas9 can be used to dissect gene regulatory mechanisms and potentially treat associated disorders. For example, Prader-Willi syndrome (PWS) results from loss of paternally expressed imprinted genes on chromosome 15q11.2-q13.3, although the maternal allele is intact but epigenetically silenced. Using CRISPR repression and activation screens in human induced pluripotent stem cells (iPSCs), we identified genomic elements that control the expression of the PWS gene SNRPN from the paternal and maternal chromosomes. We showed that either targeted transcriptional activation or DNA demethylation can activate the silenced maternal SNRPN and downstream PWS transcripts. However, these two approaches function at unique regions, preferentially activating different transcript variants and involving distinct epigenetic reprogramming mechanisms. Remarkably, transient expression of the targeted demethylase leads to stable, long-term maternal SNRPN expression in PWS iPSCs. This work uncovers targeted epigenetic manipulations to reprogram a disease-associated imprinted locus and suggests possible therapeutic interventions.

This protocols describes methods for RNA sequencing in human induced pluripotent stem cells.

New technologies and large-cohort studies have enabled novel variant discovery and association at unprecedented scale, yet functional characterization of these variants remains paramount to deciphering disease mechanisms. Approaches that facilitate parallelized genome editing of cells of interest or induced pluripotent stem cells (iPSCs) have become critical tools toward this goal. Here, we developed an approach that incorporates libraries of CRISPR-Cas9 guide RNAs (gRNAs) together with inducible Cas9 into a piggyBac (PB) transposon system to engineer dozens to hundreds of genomic variants in parallel against isogenic cellular backgrounds. This method empowers loss-of-function (LoF) studies through the introduction of insertions or deletions (indels) and copy-number variants (CNVs), though generating specific nucleotide changes is possible with prime editing. The ability to rapidly establish high-quality mutational models at scale will facilitate the development of isogenic cellular collections and catalyze comparative functional genomic studies investigating the roles of hundreds of genes and mutations in development and disease.

Recurrent copy-number variations (CNVs) at chromosome 16p11.2 are associated with neurodevelopmental diseases, skeletal system abnormalities, anemia, and genitourinary defects. Among the 40 protein-coding genes encompassed within the rearrangement, some have roles in leukocyte biology and immunodeficiency, like SPN and CORO1A . We therefore investigated leukocyte differential counts and disease in 16p11.2 CNV carriers. In our clinically-recruited cohort, we identified three deletion carriers from two families (out of 32 families assessed) with neutropenia and lymphopenia. They had no deleterious single-nucleotide or indel variant in known cytopenia genes, suggesting a possible causative role of the deletion. Noticeably, all three individuals had the lowest copy number of the human-specific BOLA2 duplicon (copy-number range: 3–8). Consistent with the lymphopenia and in contrast with the neutropenia associations, adult deletion carriers from UK biobank (n = 74) showed lower lymphocyte ( P adj = 0.04) and increased neutrophil ( P adj = 8.31e-05) counts. Mendelian randomization studies pinpointed to reduced CORO1A , KIF22 , and BOLA2-SMG1P6 expressions being causative for the lower lymphocyte counts. In conclusion, our data suggest that 16p11.2 deletion, and possibly also the lowest dosage of the BOLA2 duplicon, are associated with low lymphocyte counts. There is a trend between 16p11.2 deletion with lower copy-number of the BOLA2 duplicon and higher susceptibility to moderate neutropenia. Higher numbers of cases are warranted to confirm the association with neutropenia and to resolve the involvement of the deletion coupled with deleterious variants in other genes and/or with the structure and copy number of segments in the CNV breakpoint regions.

Autism spectrum disorder (ASD) is a heritable neurodevelopmental disorder characterized by deficits in social interactions and communication. Protein-altering variants in many genes have been shown to contribute to ASD; however, understanding the convergence across many genes remains a challenge. We demonstrate that coexpression patterns from 993 human postmortem brains are significantly correlated with the transcrip-tional consequences of CRISPR perturbations in human neurons. Across 71 ASD risk genes, there was signif-icant tissue-specific convergence implicating synaptic pathways. Tissue-specific convergence was further demonstrated across schizophrenia and atrial fibrillation risk genes. The degree of ASD convergence was significantly correlated with ASD association from rare variation and differential expression in ASD brains. Positively convergent genes showed intolerance to functional mutations and had shorter coding lengths than known risk genes even after removing association with ASD. These results indicate that convergent co -expression can identify potentially novel genes that are unlikely to be discovered by sequencing studies.

Chromosome 16p11.2 reciprocal genomic disorder, resulting from recurrent copy-number variants (CNVs), involves intellectual disability, autism spectrum disorder (ASD), and schizophrenia, but the responsible mechanisms are not known. To systemically dissect molecular effects, we performed transcriptome profiling of 350 libraries from six tissues (cortex, cerebellum, striatum, liver, brown fat, and white fat) in mouse models harboring CNVs of the syntenic 7qF3 region, as well as cellular, transcriptional, and single-cell analyses in 54 isogenic neural stem cell, induced neuron, and cerebral organoid models of CRISPR-engineered 16p11.2 CNVs. Transcriptome-wide differentially expressed genes were largely tissue-, cell-type-, and dosage-specific, although more effects were shared between deletion and duplication and across tissue than expected by chance. The broadest effects were observed in the cerebellum (2,163 differentially expressed genes), and the greatest enrichments were associated with synaptic pathways in mouse cerebellum and human induced neurons. Pathway and co-expression analyses identified energy and RNA metabolism as shared processes and enrichment for ASD-associated, loss-of-function constraint, and fragile X messenger ribonucleoprotein target gene sets. Intriguingly, reciprocal 16p11.2 dosage changes resulted in consistent decrements in neurite and electrophysiological features, and single-cell profiling of organoids showed reciprocal alterations to the proportions of excitatory and inhibitory GABAergic neurons. Changes both in neuronal ratios and in gene expression in our organoid analyses point most directly to calretinin GABAergic inhibitory neurons and the excitatory/inhibitory balance as targets of disruption that might contribute to changes in neurodevelopmental and cognitive function in 16p11.2 carriers. Collectively, our data indicate the genomic disorder involves disruption of multiple contributing biological processes and that this disruption has relative impacts that are context specific.

Rare copy-number variants (rCNVs) include deletions and duplications that occur infrequently in the global human population and can confer substantial risk for disease. In this study, we aimed to quantify the properties of haploinsufficiency (i.e., deletion intolerance) and triplosensitivity (i.e., duplication intolerance) throughout the human genome. We harmonized and meta-analyzed rCNVs from nearly one million individuals to construct a genome-wide catalog of dosage sensitivity across 54 disorders, which defined 163 dosage sensitive segments associated with at least one disorder. These segments were typically gene dense and often harbored dominant dosage sensitive driver genes, which we were able to prioritize using statistical fine-mapping. Finally, we designed an ensemble machine-learning model to predict probabilities of dosage sensitivity (pHaplo & pTriplo) for all autosomal genes, which identified 2,987 haploinsufficient and 1,559 triplosensitive genes, including 648 that were uniquely triplosensitive. This dosage sensitivity resource will provide broad utility for human disease research and clinical genetics.

Human-specific duplications at chromosome 16p11.2 mediate recurrent pathogenic 600 kbp BP4-BP5 copy number variations, one of the most common genetic causes of autism. These copy number polymorphic duplications are under positive selection and include 3–8 copies of BOLA2 , a gene involved in the maturation of cytosolic iron-sulfur proteins. To investigate the potential advantage provided by the rapid expansion of BOLA2 , we assessed hematological traits and anemia prevalence in 379,385 controls and individuals who have lost or gained copies of BOLA2 : 89 chromosome 16p11.2 BP4-BP5 deletion and 56 reciprocal duplication carriers in the UK Biobank. We found that the 16p11.2 deletion is associated with anemia (18/89 carriers, 20%, P =4e-7, OR=5), particularly iron-deficiency anemia. We observed similar enrichments in two clinical 16p11.2 deletion cohorts, with 6/63 (10%) and 7/20 (35%) unrelated individuals with anemia, microcytosis, low serum iron, or low blood hemoglobin. Upon stratification by BOLA2 copy number, we found an association between low BOLA2 dosage and the above phenotypes (8/15 individuals with three copies, 53%, P =1e-4). In parallel, we analyzed hematological traits in mice carrying the 16p11.2 orthologous deletion or duplication, as well as Bola2 +/- and Bola2 -/- animals. The deletion and Bola2 -deficient mice showed early evidence of iron deficiency, including a mild decrease in hemoglobin, lower plasma iron, microcytosis, and an increased red blood cell zinc protoporphyrin to heme ratio. Our results indicate that BOLA2 participates in iron homeostasis in vivo and its expansion has a potential adaptive role in protecting against iron deficiency.

Genetic changes causing brain size expansion in human evolution have remained elusive. Notch signaling is essential for radial glia stem cell proliferation and is a determinant of neuronal number in the mammalian cortex. We find that three paralogs of human-specific NOTCH2NL are highly expressed in radial glia. Functional analysis reveals that different alleles of NOTCH2NL have varying potencies to enhance Notch signaling by interacting directly with NOTCH receptors. Consistent with a role in Notch signaling, NOTCH2NL ectopic expression delays differentiation of neuronal progenitors, while deletion accelerates differentiation into cortical neurons. Furthermore, NOTCH2NL genes provide the breakpoints in 1q21.1 distal deletion/duplication syndrome, where duplications are associated with macrocephaly and autism and deletions with microcephaly and schizophrenia. Thus, the emergence of human-specific NOTCH2NL genes may have contributed to the rapid evolution of the larger human neocortex, accompanied by loss of genomic stability at the 1q21.1 locus and resulting recurrent neurodevelopmental disorders.

Segmental duplications contribute to human evolution, adaptation and genomic instability but are often poorly characterized. We investigate the evolution, genetic variation and coding potential of human-specific segmental duplications (HSDs). We identify 218 HSDs based on analysis of 322 deeply sequenced archaic and contemporary hominid genomes. We sequence 550 human and nonhuman primate genomic clones to reconstruct the evolution of the largest, most complex regions with protein-coding potential (N = 80 genes from 33 gene families). We show that HSDs are non-randomly organized, associate preferentially with ancestral ape duplications termed ‘core duplicons’ and evolved primarily in an interspersed inverted orientation. In addition to Homo sapiens-specific gene expansions (such as TCAF1/TCAF2), we highlight ten gene families (for example, ARHGAP11B and SRGAP2C) where copy number never returns to the ancestral state, there is evidence of mRNA splicing and no common gene-disruptive mutations are observed in the general population. Such duplicates are candidates for the evolution of human-specific adaptive traits. Segmental duplications in the genome are regions with the potential for the evolution of phenotypic novelties, but their cataloguing has been technically difficult. Here, the evolution and function of human duplications is characterized.

16p11.2 deletions and duplications are commonly associated with autism spectrum disorder and linked to mirrored phenotypes of physical characteristics and higher penetrance for deletions. A male with a rare 16p11.2 triplication demonstrated a similar phenotypic presentation to deletion carriers with neurocognitive and adaptive skill deficits and above-average physical growth.