Abstract
Background Copy number variants at chromosome 15q13.3 contribute to liability for multiple intellectual and developmental disabilities including Autism Spectrum Disorder (ASD). Individuals with duplications of this interval, which includes the gene CHRNA7, have multiple psychiatric disorders with widely variable penetrance. However, the basis of such differential affectation remains uncharacterized.
Methods Induced pluripotent stem cell (iPSC) models were generated from two first degree relatives with the same 15q13.3 duplication, a boy with distinct features of autism and emotional dysregulation (the affected proband, AP) and his clinically unaffected mother (the UM). These models were compared to unrelated control subjects lacking this duplication (UC, male and female). iPSC-derived neural progenitors and cortical neuroids consisting of cortical excitatory and inhibitory neurons were used to model potential contributors to neuropsychiatric impairment.
Results The AP-derived model uniquely exhibited disruptions of cellular physiology and neurodevelopment not observed in either the UM or the unrelated male and female controls. These included enhanced neural progenitor proliferation but impaired neuronal differentiation, maturation, and migration, and increased endoplasmic reticulum (ER) stress. Both the AP model’s neuronal migration deficit and elevated ER stress could be selectively rescued by different pharmacologic agents. Neuronal gene expression was also specifically dysregulated in the AP, including reduced expression of genes related to behavior, psychological disorders, neuritogenesis, neuronal migration, and WNT, axonal guidance, and GABA receptor signaling. Interestingly, the UM model exhibited upregulated expression of genes in many of these same pathways, by comparison with both the AP and UC models, suggesting that cell intrinsic molecular compensation could have contributed to the lack of neurodevelopmental phenotypes in the UM model. However, by contrast with the AP-specific neurodevelopmental phenotypes, both the AP- and UM-derived neurons exhibited shared alterations of neuronal function, including increased action potential firing and elevated cholinergic activity, consistent with increased homomeric CHRNA7 channel activity.
Conclusion Together, these data define both affectation-specific phenotypes seen only in the AP, as well as abnormalities observed in both individuals with CHRNA7 duplication, the AP and UM, but not in UC-derived neurons. This is, to our knowledge, the first study to use a human stem cell-based platform to study the basis of variable affectation in cases of 15q13.3 duplication at the cellular, molecular, and functional levels. This work suggests potential approaches for suppressing abnormal neurodevelopment or physiology that may contribute to severity of affectation. Some of these AP-specific neurodevelopmental anomalies, or the functional anomalies observed in both 15q13.3 duplication carriers (the AP and UM), could also contribute to the variable phenotypic penetrance seen in other individuals with 15q13.3 duplication.
Competing Interest Statement
F. Urano received JTV-519 from the National Center for Advancing Translational Sciences for the development of small molecule-based therapies for ER stress-related disorders and shares the intellectual property right related to JTV-519 with the National Institutes of Health. F. Urano is an inventor of the patent related to ER calcium stabilizers, 10,441,574, B2 TREATMENT FOR WOLFRAM SYNDROME AND OTHER ER STRESS DISORDERS. The other authors declare that they have no competing interests.
Footnotes
meganathank{at}wustl.edu, r.prakasam{at}wustl.edu, dbaldri{at}wustl.edu, pgontarz{at}wustl.edu, bzhang29{at}wustl.edu, urano{at}wustl.edu, bonni{at}wustl.edu, jhuettner{at}wustl.edu, constantino{at}wustl.edu
Introduction and Discussion were revised to enhance clarity and impact
Abbreviations
- ASD
- Autism Spectrum Disorder
- iPSCs
- Induced Pluripotent Stem Cells
- CNVs
- Copy Number Variations
- CHRNA7
- α-7 nicotinic acetylcholine receptor subunit
- ID
- Intellectual Disability
- IDD
- Intellectual and Developmental Disability
- ADHD
- Attention Deficit and Hyperactivity Disorder
- ER
- Endoplasmic Reticulum
- GABA
- Gamma Aminobutyric Acid
- RYR
- Ryanodine Receptor
- UPR
- Unfolded Protein Response
- cExNs
- Cortical Excitatory Neurons
- cINs
- Cortical Inhibitory Neurons
- NPCs
- Neural Progenitor Cells
- UM
- Unaffected Mother
- AP
- Affected Proband
- AB
- Affected Brother
- UC-M
- Unrelated Control-Male
- UC-F
- Unrelated ControlFemale
- GTAC
- Genome Technology Access Center
- ICC
- Immunocytochemistry
- RT-qPCR
- reverse transcription and quantitative PCR
- EBs
- Embryoid Bodies
- DEG
- Differentially Expressed Gene
- IPA
- Ingenuity Pathway Analysis
- PI
- Propidium Iodide
- PCA
- Principal Component Analysis
- GO
- Gene Ontology