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A number of rare copy number variants (CNVs) have been linked to neurodevelopmental disorders. However, because CNVs encompass many genes, it is often difficult to identify the mechanisms that lead to developmental perturbations.
We used 15q13.3 microdeletion to propose and validate a novel strategy to predict the impact of CNV genes on brain development that could further guide functional studies. We analyzed single-cell transcriptomics datasets containing cortical interneurons to identify their developmental vulnerability to 15q13.3 microdeletion, which was validated in mouse models.
We found that Klf13—but not other 15q13.3 genes—is expressed by precursors and neuroblasts in the medial and caudal ganglionic eminences during development, with a peak of expression at embryonic day (E)13.5 and E18.5, respectively. In contrast, in the adult mouse brain, Klf13 expression is negligible. Using Df(h15q13.3)/+ and Klf13+/− embryos, we observed a precursor subtype-specific impairment in proliferation in the medial ganglionic eminence and caudal ganglionic eminence at E13.5 and E17.5, respectively, corresponding to vulnerability predicted by Klf13 expression patterns. Finally, Klf13+/− mice showed a layer-specific decrease in parvalbumin and somatostatin cortical interneurons accompanied by changes in locomotor and anxiety-related behavior.
We show that the impact of 15q13.3 microdeletion on precursor proliferation is grounded in a reduction in Klf13 expression. The lack of Klf13 in Df(h15q13.3)/+ cortex might be the major reason for perturbed density of cortical interneurons. Thus, the behavioral defects seen in 15q13.3 microdeletion could stem from a developmental perturbation owing to selective vulnerability of cortical interneurons during sensitive stages of their development.
). Each of these CNVs might have a specific mechanism contributing to developmental disturbance, which is difficult to discern in human context owing to limitations of in vitro approaches reproducing human brain development. One such high-risk variant, the 15q13.3 locus, is associated with wide-ranging clinical outcomes, including intellectual disability, autism spectrum disorder, attention-deficit/hyperactivity disorder, epilepsy, and schizophrenia (
). The 15q13.3 microdeletion encompasses seven protein-coding genes (CHRNA7, OTUD7A, KLF13, MTMR10, FAN1, TRPM1, and ARHGAP11B), a human-specific partial duplication of CHRNA7 (CHRFAM7A), a microRNA (miR211), and a putative pseudogene (LOC283710). The hemizygous microdeletion generally has high penetrance for neurodevelopmental disorders, with >80% of total cases diagnosed with at least one neuropsychiatric abnormality (
). However, the etiology underlying the 15q13.3 microdeletion syndrome remains elusive, and exploring mechanisms of 15q13.3 microdeletion–derived developmental impairment should provide insights into the common biology of neurodevelopmental disorders.
Existing mouse models of 15q13.3 microdeletion show high construct validity (
). However, only one of them, the Df(h15q13)/+, also shows an increased sensitivity to stress, long-term spatial memory deficits, sensorimotor gating deficits, and high susceptibility to developing myoclonic seizures (
), thus mirroring key clinical observations seen in patients with the 15q13.3 microdeletion. At the cellular level, Df(h15q13)/+ mice display aberrant brain connectivity, reduced firing of interneurons, and lower sensitivity of pyramidal cells to GABAAR (gamma-aminobutyric acid A receptor) antagonism in the prefrontal cortex (
), implying that microdeletion causes inhibitory dysfunction. Such a phenotype supports accumulating evidence that excitation-inhibition imbalance in the cortex is a common feature of neurodevelopmental disorders (
). Two main areas generating such interneuron diversity are the medial GE (MGE) and caudal GE (CGE); the MGE produces parvalbumin (PV) and somatostatin (SST) classes of interneurons, and the CGE produces a highly heterogeneous class of interneurons that express vasoactive intestinal peptide, neuropeptide Y, reelin, and several other rarer markers (
), highlighting selective neuronal vulnerability to pathological insults. Thus, genetic insults such as 15q13.3 microdeletion are likely to also preferentially affect specific neuronal subtypes while sparing others during cortical development, which might underlie behavioral abnormalities in adults.
Recent efforts in single-cell analysis have uncovered a staggering diversity of interneuron subtypes (
). Therefore, we implemented a strategy to first identify the expression of 15q13.3 locus genes in cortical interneurons in single-cell RNA sequencing (scRNA-seq) data during development through to adulthood (
). We then used enrichment of 15q13.3 locus genes to predict whether and when each gene is involved in development of cortical interneurons, where high expression of a gene during certain developmental period might identify vulnerable subtypes of interneurons and developmental stages. We showed that 15q13.3 locus genes were expressed in precursors of interneurons and immature interneurons, where Klf13 was the only gene with high expression level in precursor cells. Using Df(h15q13.3)/+ mice, we confirmed the impact of the microdeletion on interneuron precursor proliferation. Furthermore, by implementing Klf13 knockout mice, we demonstrated that heterozygous deletion of Klf13 alone had a similar effect on precursor proliferation as the whole 15q13.3 locus. Overall, our study proposes a new strategy to predict the impact of CNV genes on brain development and validates the prediction by gene knockout analyses.
Methods and Materials
Animal Experiments and Genotyping
All animal experimental procedures were conducted in accordance with guidelines published by the National Animal Ethic Committee of Denmark and Danish legislation. C57BL/6J (Janvier Labs), Klf13−/− (
) (Taconic Biosciences) mice used in this study were housed in individually ventilated cages with standard sawdust bedding and environmental enrichment in a 12-hour reversed light/dark cycle with ad libitum access to food and water. Only wild-type (WT) females were used for breeding to minimize the potential maternal effects of Df(h15q13.3)/+. The date of the plug was treated as embryonic day (E)0.5, and the embryos were staged accordingly. Details of genotyping and behavior are provided in the Supplement.
BrdU Labeling, Immunohistochemistry, Image Acquisition, and Statistical Analysis
Pregnant dams were injected intraperitoneally at E13.5, E15.5, and E17.5 with 50 mg/kg bromodeoxyuridine (B5002; Sigma-Aldrich), and embryos were collected 2 hours later and fixed in 4% paraformaldehyde overnight. Brains from postnatal mice were collected and processed for immunostaining as previously described (
). Further details can be found in the Supplement.
scRNA-Seq Data Analysis
scRNA-seq datasets, codes, and data analysis are detailed in the Supplement.
Expression of 15q13 Microdeletion Genes in GEs
In 15q13.3 microdeletion syndrome, the initial trigger for any developmental abnormalities should arise from reduced expression of 15q13.3 genes. Thus, to identify when during development and in what subtypes of interneurons 15q13.3 microdeletion genes are expressed, we exploited several single-cell transcriptomics datasets characterizing developing and mature interneurons (
To determine the developmental stage of expression for 15q13.3 microdeletion genes, we ordered transcriptomes of single cells at E13.5 from MGE and CGE along differentiation trajectories from neural stem cells to neuron precursors and immature postmitotic neuroblasts (NBs) using a recently developed means of scoring maturation (
) of interneurons from precursors. As expected, markers of differentiation stage and genes associated with cell proliferation and cell cycle corresponded well with maturation score (Figure 1A). To reconstruct expression trajectories of 15q13.3 microdeletion genes during development, we aligned expression with the aforementioned differentiation markers (Figure 1B, C). Among 15q13.3 microdeletion locus genes, notable expression could be observed only for Klf13, which was confirmed by comparing mean log(counts) for 15q13.3 microdeletion and developmental stage marker genes (Figure 1D, E). Expression levels for Klf13 were higher in mitotic than postmitotic cells in the GEs (Figure 1D–F), which correlated with the majority of Klf13 gene counts detected in cells expressing neural stem cell and neuron precursor markers (Figure 1B, C). Interestingly, at E13.5/E14.5, while only few postmitotic cells expressed Klf13 in the MGE, larger fractions of postmitotic cells expressed Klf13 in the CGE (Figure 1F, G).
15q13.3 Microdeletion Has Developmental Stage–Specific Effects on MGE and CGE Precursor Proliferation
Differences in expression levels of Klf13 between GEs and mitotic/postmitotic cells might suggest a differential impact on generation of MGE and CGE interneuron subtypes and selective vulnerability of GEs to 15q13.3 microdeletion. To test this hypothesis, we used Df(h15q13)/+ mice harboring heterozygous microdeletion of 15q13.3 locus (
) and investigated the effect of 15q13.3 microdeletion on MGE and CGE precursor proliferation at different stages of development. Here, we injected WT females, time-mated with Df(h15q13)/+ males, at E13.5, 15.5, or 17.5 with the proliferation marker BrdU and analyzed neuronal precursor proliferation 2 hours thereafter (Figure 2A). By colabeling for BrdU and MGE or CGE progenitor markers, Nkx2.1, and COUP-TFII, respectively, we found that 15q13.3 microdeletion affects each GE differentially. Specifically, in the MGE, proliferation was affected only at E13.5, whereas in the CGE, proliferation was affected only at E17.5. Proliferation was not affected at E15.5 in either GE (Figure 2B–G). Furthermore, while 15q13.3 microdeletion decreased proliferation in the MGE at E13.5, the microdeletion had the opposite effect on precursor proliferation in the CGE at E17.5. (Figure 2B, G). These data support the notion that different subtypes of interneurons have selective vulnerability to the genetic insult induced by 15q13.3 microdeletion. The effect of the microdeletion on proliferation of neuronal precursors could cause abnormal development of cortical circuitry.
Klf13 Heterozygous Mice Recapitulate Developmental Impairment of 15q13.3 Microdeletion
As our findings suggested that the developmental impairment in 15q13.3 mice stemmed largely from the lack of Klf13, we sought to confirm whether the lack of Klf13 on its own affects interneuron production and reproduces the effect of 15q13.3 microdeletion on precursor cells. First, we confirmed that both MGE and CGE progenitors express KLF13 (Figure S1A, B). Then, we studied the proliferation of MGE and CGE precursors in a previously described Klf13 knockout mouse model (
). We found a reduced proliferation of MGE progenitors in Klf13 heterozygous embryos at E13.5 as evidenced by the proportion of Nkx2.1+ progenitors that were also labeled for BrdU (Figure 3A, B). In contrast, at E17.5, an increased proportion of COUPT-TFII+ CGE progenitors were labeled for BrdU in the Klf13+/− embryos (Figure 3C, D). Therefore, Klf13 heterozygous deletion shows similar effect on precursor proliferation as heterozygous 15q13.3 microdeletion.
To explore the consequences of impaired precursor proliferation on postnatal distribution of cortical interneurons, we compared the proportion of PV and SST interneurons in the anterior cingulate (ACC) and primary somatosensory (S1) cortices of WT, Klf13+/− and Klf13−/− mice. As not all PV interneurons express detectable levels of PV in the ACC at postnatal day (P)15, we used COX6A2 that we have previously shown to be specific for PV+ interneurons with earlier onset of expression (
) to identify putative PV interneurons in the ACC. The density of PV interneurons was decreased in both S1 and ACC (Figure 3E–I; Figures S2A–C and S3A–C). Similarly, SST interneurons showed a decreased density in S1 (Figure 3E–J; Figures S2A, B, D, F) and ACC (Figures S3A, B, D). Importantly, decrease in proliferation of interneuron precursors and subsequent reduction in the density of PV and SST interneurons correlated with behavioral impairment in Klf13+/− mice. Thus, in the open field test, Klf13+/− mice showed reduced locomotor activity and speed in both females and males (Figure 4A–E). In addition, male mice showed anxiety-related behavior observed as increased distance traveled in wall-near zone in the open field as compared with distance traveled in the inner zone of the open field (Figure 4F–I). This thigmotaxis behavior was less clear or absent in females (Figure 4F–I). The decrease in Klf13 expression was hence sufficient to recapitulate the developmental impairment seen in 15q13.3 microdeletion mice in this and other studies (
). Moreover, the absence of Klf13 had a behavioral imprint related to cortical impairment.
The Effect of 15q13.3 Microdeletion on MGE and CGE Precursors Is Likely Driven by KLF13-Associated Signaling Network
As both MGE and CGE express Klf13 gene, and expression levels of other 15q13.3 microdeletion genes are very low, selective vulnerability of MGE and CGE cells at E13.5 and E17.5, respectively, is likely to be mediated by proteins that are associated with KLF13. Thus, we used STRING protein-protein interaction network analysis (string-db.org) to identify proteins that are associated with KLF13. In addition to the proteins coded by the 15q13.3 locus, STRING analysis identified 11 other proteins that either interact with KLF13, are coexpressed, or are mentioned together in research literature (Figure 5A) (
). To determine whether expression levels of Klf13-associated genes can explain the effect of 15q13.3 microdeletion on precursor proliferation at E17.5, we explored an scRNA-seq dataset generated at later stages of neurogenesis (P0) (
). We first extracted cells that are annotated to belong to the GEs and then split those cells based on the MGE and CGE markers (Figure 5B, C).
Although several Klf13-associated genes are expressed at equal levels in MGE and CGE precursors at E13.5/14.5, Ccnd1 and Gsk3b expression is higher in MGE than CGE precursors (Figure 5D). Thus, at P0, among Klf13-associated genes, Ccnd1 and Serpinh1 were preferentially expressed in the CGE in addition to being expressed in a higher percentage of cells (Figure 5E). Both CCND1 and GSK3B are crucial for the canonical Wnt signaling pathway and have been implicated in regulating neural precursor proliferation (
). Hence, differential expression of Ccnd1 and Gsk3b between the GEs at E13.5/14.5 and P0 might underlie previously identified selective vulnerability of MGE and CGE precursors at E13.5 and E17.5 (Figure 2B, G).
Klf13 Shows Dynamic Expression in Postmitotic Cortical Interneurons During Development
Cortical interneurons are a very diverse class of neurons, and both MGE and CGE produce multiple neuronal subtypes. Recent scRNA-seq analysis identified approximately 60 transcriptomic subtypes of cortical interneurons (
). However, such diversity cannot be distinguished during brain development, and only large families of subtypes are identified in single-cell transcriptomics data during embryogenesis and early postnatal maturation (
) to gain further insights into potential vulnerability of interneuron subtypes to 15q13.3 microdeletion. We extracted transcriptomes of postmitotic cells (the majority of which are NBs according to marker gene expression—Figure 1A, D, E) from the MGE and CGE at E13.5 and from cortical NBs and immature interneurons at E18.5 and P10, respectively, and analyzed the expression of 15q13.3 genes at each developmental period. We plotted normalized average gene expression counts for all postmitotic cells studied at E13.5, E18.5, and P10. Interestingly, Klf13 was again the only gene presenting notable expression levels up to P10 (Figure 6A–F). Furthermore, we show a robust detection of Klf13 counts in various subtypes of interneurons (Figure 6D–F). To predict vulnerability of different subtypes of interneurons to heterozygous deletion of Klf13, we compared Klf13 expression levels across subtypes for each developmental stage. To this end, at E13.5, Klf13 showed the highest expression in cardinal CGE-derived interneuron subtypes Vip and Id2, whereas expression in cardinal MGE-derived interneuron subtypes Pvalb and Sst was lower, particularly for Pvalb (Figure 6A). At E18.5, the trend for stronger expression of Klf13 in cardinal CGE-derived interneuron subtypes persisted (Figure 6B). However, whereas Vip interneurons continued expressing high levels of Klf13, the level of Klf13 expression in Id2 interneurons dropped, and by P10, expression of Klf13 was dramatically decreased across all CGE-derived subtypes.
In general, cardinal MGE-derived subtypes of interneurons exhibited lower Klf13 expression than cardinal CGE-derived subtypes. Nevertheless, Klf13 expression was relatively high in postmitotic Sst interneurons at E13.5, soon after they become NBs, which then declined by P10. This also correlates with the decrease in MGE precursor proliferation in Df(h15q13)/+ mice at E13.5, but not later (Figure 2B, D, F). Thus, the effect of Klf13 deletion on Sst interneurons might be more pronounced in the middle than the late period of embryonic neurogenesis.
We also found restricted expression of other 15q13.3 microdeletion genes in postmitotic interneurons during development. At E13.5, barring Klf13, expression of other 15q13.3 genes was very low. However, at E18.5, Mtmr10 showed specific expression in Pvalb chandelier cells, whereas at P10, some Fan1 expression could be detected in Sst non-Martinotti cells (Figure 6B, C). In addition, we observed low expression of Chrna7, Otud7a, and Mtmr10 in the Igfbp6 subtype at P10 (Figure 6C). Nevertheless, despite the low-scale expression of Fan1 and Mtmr10 during NB maturation, misexpression of Klf13 should contribute to the majority of embryonic impairments due to CNVs in the 15q13.3 locus.
In the Mature Cortex, Expression of 15q13.3 Genes Is Strong in CGE-Derived Cortical Interneuron Subtypes
Some mental disorders, for instance, schizophrenia, have an onset around adolescence and early adulthood. By this time, cortical circuit maturation is almost complete. To investigate the expression of 15q13.3 genes at the prodromal stages of the disorder, we used single-cell transcriptomics data from P56 mouse cortex (
). Expression levels were negligible for Mtmr10, Fan1, and Trpm1 across the delineated subtypes at this stage. Interestingly, in contrast to broad expression at embryonic and neonatal stages, in the mature cortex, Klf13 expression was restricted to a few specific subtypes of CGE-derived Vip and Sncg interneurons with low to moderate expression levels (Figure 7). All MGE-derived subtypes showed very low expression of Klf13. On the other hand, Otud7a was now robustly and broadly expressed in many interneuron subtypes, being highest in Vip subtypes (especially in Vip_Ptprt_Pkp2, Vip_Rspo4_Rxfp1_Chat, and Vip_Rspo1_Itga4). Importantly, the expression of Chrna7, which was also very low at embryonic and early postnatal stages, was now expressed at high levels in specific subtypes of Lamp5 interneurons (Lamp5_Fam19a1_Pax6, Lamp5_Krt73, Lamp5_Fam19a1_Tmem182), of which Lamp5_Fam19a1_Tmem182 was predicted to correspond to single bouquet cells (
). Similar to other 15q13.3 microdeletion genes, Chrna7 expression was almost absent from Pvalb and Sst interneuron subtypes. Together, this suggests that CGE-derived Vip and Lamp5 subtypes and their associated microcircuits are vulnerable to 15q13.3 microdeletion in late adolescent stages.
Dynamic Expression of 15q13.3 Microdeletion Genes During Interneuron Development
To visualize the expression dynamics of 15q13.3 microdeletion genes across interneuron subtypes and developmental stages, we converged the high-resolution interneuron subtypes into cardinal identities (Pvalb, Sst, Vip, Id2, and Nos1) and compared the expression values of the six 15q13.3 microdeletion genes during development.
Klf13 expression in Sst and Nos1 subtypes remained nearly constant throughout the developmental stages. In contrast, Klf13 expression was higher in Vip and Id2 clusters at E13, peaking at E18 before being downregulated in both subtypes by P10 (Figure 8A). Expression in the Pvalb subtype followed a similar pattern to Sst but showed the lowest expression among all subtypes by P10. By P56, however, Klf13 expression was downregulated in all subtypes. Interestingly, Klf13 expression in basket and chandelier Pvalb cells followed reciprocal trajectories. While Klf13 expression in chandelier cells peaked at E18 followed by decline to P10, in basket cells, Klf13 expression dropped at E18 and peaked at P10 (Figure 8B). Expression of three genes—Mtmr10, Fan1, and Trpm1—was almost negligible across the developmental stages and mature interneurons, and for two other genes—Chrna7 and Otud7a—significant expression could be detected only at P56 (Figure 8C–G). Accordingly, Vip and Id2 subtypes are likely to be affected by reduced expression of Chrna7 due to hemizygous 15q13.3 microdeletion, while the decrease in Otud7a expression should have a rather broad effect on mature interneuron subtypes (Figure 8C, E).
The mammalian brain is composed of diverse cell types that contribute to behavior in different ways. Transcriptomics studies involving whole-tissue RNA-seq, while useful, are restricted in associating specific cell types with disease, and we still lack knowledge to associate complex behavioral outcomes such as schizophrenia with dysfunctions of specific neuronal subtypes. The development of single-cell transcriptomics approaches offers a novel means of studying the contribution of individual neuronal subtypes to abnormalities in neuronal circuitry underlying mental disorders. Previous efforts in this direction sought common variants from genome-wide association studies that were enriched in transcriptomes of classes of neural cells in the brain (
). Importantly, these studies identified convergent cell types that potentially underlie symptoms of psychiatric disorders. It is expected that studying genes residing in rare CNVs will have greater power in identifying neuronal subtypes contributing to psychiatric disorders because the association of CNVs to mental illnesses is stronger than for common variants. Thus, in our study, we took a further step in resolution and analyzed enrichment of 15q13.3 CNV genes in individual interneuron subtypes throughout brain development and validated our results in mouse models.
The etiology of rare variants contributing to psychiatric disorders, such as 15q13.3 microdeletion syndrome, remains elusive, and no genes driving pathogenesis have been clearly identified. CHRNA7 and OTUD7A were previously proposed as candidate driver genes for the disorder as most cases show overlapping deletions for these two genes. However, CHRNA7 exhibits haploinsufficiency in humans, and Chrna7−/− mice do not consistently replicate the phenotype of Df(h15q13.3)/+ mice (
). Here, we show that the expression of Chrna7 and Otud7a is negligible in interneurons and their precursors during embryonic period when precursor proliferation in affected by 15q13.3 microdeletion. Hence, we suggest that while important for cortical maturation, neither gene is sufficient to explain the developmental impairments seen in 15q13.3 microdeletion syndrome.
Instead, our analysis points toward a major role for Klf13, which might underlie the effect of 15q13.3 microdeletion on interneuron development. Here, Klf13 is expressed both by a subset of dividing interneuron progenitors and by postmitotic neuroblasts in the GEs. Importantly, while MGE-derived interneuron subtypes express higher levels of Klf13 at E13.5 followed by declining of Klf13 expression, high expression of Klf13 in the CGE persists to E17.5. Importantly, using tissue from Df(h15q13.3)/+ and Klf13+/− embryonic mice (
), we show that the microdeletion affects proliferation in both MGE and CGE precursors but at different developmental stages—namely, MGE precursor proliferation is affected at E13.5 and that of CGE at E17.5. This emphasizes the role of Klf13 in embryonic neurodevelopment and supports our findings that Klf13 gene explains the impairments seen in mice carrying the 15q13.3 microdeletion. Furthermore, the difference in impact on MGE and CGE precursors in both mice is likely due to the differential expression of the Klf13-associated gene network, where Wnt signaling components Ccnd1 and Gsk3b might play the main role. By studying the expression of 15q13.3 genes in mitotic and postmitotic interneuron subtypes, we propose a significant effect on CGE-derived Vip and Id2 expressing interneurons starting from embryonic stages and persisting through early adulthood. Both subtypes have been described to play a role in cortical microcircuits and to mediate complex behaviors in mouse models (
). In both maternal immune activation and Df(h15q13.3)/+ mice, we show a differential impact on interneuron progenitors that depends on the developmental stage, i.e., MGE and CGE precursors show impaired proliferation, with MGE proliferation being affected during early neurogenesis and CGE proliferation at late neurogenesis, respectively. This translates into an impact on specific interneuron subtypes in the postnatal brain, suggesting a common etiology for these distinct models replicating genetic (15q13.3) or environmental (maternal inflammation) insults. This differential impact on interneuron subtypes was also seen in Klf13 knockout mice, where a reduction in SST+ and PV+ interneurons could be observed in cingulate and somatosensory cortex. Our study hence identified Klf13 as being important for normal interneuron development. Furthermore, we show that absence of Klf13 results in marked behavioral impairment reminiscent of 15q13.3 microdeletion mice and other genetic models of neurodevelopmental disorders. Genome-wide association studies suggest KLF13 to be associated with schizophrenia and drug dose response in patients with schizophrenia (
). This calls for further studies into the cellular and molecular role of KLF13 in neurodevelopment.
The expression of Chrna7 and Otud7a in the adult but not developing neocortex points toward their role in circuit maturation rather than in the generation and migration of interneurons. Specifically, disturbed expression of these genes might impair Vip and Id2 subtypes at adult stages. In addition to the six protein-coding genes, the 15q13.3 locus also houses a microRNA, miR-211. Interestingly, a mouse model overexpressing miR-211 shows increased epileptiform activity, thereby indicating a crucial role for this microRNA (
). However, selection for polyadenylated RNA molecules in the preparation of the single-cell transcriptomics datasets precluded us from studying miR-211 expression.
Our strategy of using scRNA-seq datasets allows to predict the cell-type–specific effect of individual genes and CNVs on brain development and maturation. By implementing this strategy, we identified Klf13 as a novel regulator of interneuron development and major contributor to the developmental pathology of 15q13.3 CNV. Furthermore, our study shows that selective vulnerability of interneuron subtypes to 15q13.3 CNV during development is based on the reduction in expression of Klf13 gene, where Klf13-controlled set of genes might work as a “receiving set” for vulnerability to a genetic insult, similar to recently proposed mechanisms of environmental impact on cortical development (
). Such delineation of genes responsible for selective vulnerability is crucial for directing future efforts in studying the neurobiological basis of phenotypes observed in neurodevelopmental disorders.
Acknowledgments and Disclosures
This work was supported by the Novo Nordisk Foundation Hallas-Møller Investigator grant (Grant No. NNF16OC0019920 [to KK]), Lundbeck-NIH Brain Initiative grant (Grant No. 2017-2241 [to KK]), Lundbeck Ascending Investigator grant (Grant No. 2020-1025 [to KK]), and DFF-Forskningsprojekt1 (Grant No. 8020-00083B [to KK]). NAV is supported by a BRIDGE-Translational Excellence Programme fellowship funded by Novo Nordisk Foundation (Grant No. NNF18SA0034956). CB and OK are supported by the Novo Nordisk Foundation Laureate Program (Grant No. NNF15OC0014186) and DFF-Forskningsprojekt2. SM was supported by the SMP-Erasmus+ Traineeship Grant by the European Commission.
We thank Dr. Yasuko Antoku and the BRIC microscopy core facility for assistance with microscopy, Viktor Petukhov for generously overseeing the computation, and members of the Khodosevich lab for constructive discussions relating to this study. We are grateful to Professor Mona Nemer (University of Ottawa, Canada) for generously providing the Klf13+/− mouse model and to Megan Fortier for help with breeding and shipment. We also thank the research labs associated to the data analyzed above for making their datasets and code publicly available.
The authors report no biomedical financial interests or potential conflicts of interest.
Some rare copy number variants (CNVs) that are either a microdeletion or a duplication of a specific genomic region containing several genes are associated with neurodevelopmental disorders. Typically, a CNV can cause multiple psychiatric phenotypes via complex pleotropic effects. This suggests that the pathological mechanisms resulting from the loss or duplication of several genes may be partially shared across psychiatric diseases. Thus, CNVs constitute highly valuable entry points to investigate the mechanisms of pathogenesis associated with neurodevelopmental disorders.