Final Report Summary - DISEASEAVATARS (Modeling Disease through Cell Reprogramming: a Translational Approach to the Pathogenesis of Syndromes Caused by Symmetrical Gene Dosage Imbalances)
Our goal
Across a wide spectrum of severity, intellectual disability and autism spectrum disorders (ASD) are aspects of the human condition that constitute an enormous burden for affected patients and families. The fundamental limitation in our understanding of such conditions lies in the lack of meaningful models to understand the mechanisms of disease in a patient-specific manner, starting form the uniqueness of each genetic background. We focused on two neurodevelopmental disorders, Williams-Beuren Syndrome (WBS) and 7dup autism-spectrum disorder (7DUP), which result from genetic changes that either half (WBS) or increase by half (7DUP) the amount of expression of a small set of genes (gene dosage) in chromosome 7. These disorders manifest physical, intellectual and behavioural features that are either directly or inversely related to their respective gene dosage and thus also represent a unique opportunity to understand, in humans, how the dosage of just a few genes underlies quintessential features of the human condition, such as cognition, language and sociality.
The advent in 2006 of the Nobel prize winning technology known as somatic cell reprogramming, constituted a game changer in our ability to convert any cell of our body into stem cells which have the potential to be differentiated into any desired tissue, also known as induced-pluripotent stem cells (iPSCs). During this project, we obtained cells (usually from skin) from individuals with these disorders and their unaffected relatives and assembled for these two disorders the largest available cohort of iPSCs, which we then differentiated in vitro into neurons and neural crest cells, two of the cell types that are particularly affected in these syndromes.
The cells that make our face and brain...... in a dish
Our characterization of the fundamental properties of patients’ iPSCs, such as the global way in which their genome is regulated, showed first of all that iPSCs are per se predictive of future physiological manifestations. To study in detail the tissues affected in these disorders, we produced in vitro neural crest stem cells (NCS, which are precursors of the cells composing the key structures of our face) and cells from the brain cortex in 2- and 3-dimensional cultures (also known as brain organoids). These models recapitulated salient morphological and functional features of human fetal development. In the course of this validation process, we confirmed that cortical brain organoids display the key cell subpopulations that originate the neuronal diversity in the developing human fetal cortex (progenitor cells) and, interestingly, discovered that the enzyme GSK3 is essential in the production and organization of such progenitors.
A remarkable connection with human evolution
Interestingly, the comparison of molecular information from our patient-derived NCS and genetic information inferred from human ancestors (Neanderthals and Denisovans), allowed us to provide the first experimental evidence to support the recently-emerging view that humans facial features and brain shape are likely the result of an evolutionary process of “self-domestication”, in which humans have become morphologically and behaviourally more “docile” over time. Specifically, the fact that certain characteristics of the syndromes we studied in this project amplify specific traits resulting from human evolution allowed us to narrow down the molecular underpinning of such self-domestication process to the levels of the gene “BAZ1B”, one of the genes affected in WBS and 7DUP, that controls the early production of NCS.
Therapeutic perspective.
Looking in detail at our in vitro brain models, we discovered that the brain cortex of patients with WBS mature at a slower rate, opposite to 7DUP in maturation is faster. We pursued this discovery all the way down to the resolution of individual cells in brain organoids derived from patients, and thereby found that one gene in particular, “GTF2I”, is central to the regulation of this maturation dynamics. We thus invested major efforts to translate these and related findings, screening vast libraries of chemical compounds on patient-derived neurons grown in the dish and succeeding in the identification of highly selective chemicals that revert the key alterations underlying the two syndromes, and which we now wish to advance towards preclinical development.
Across a wide spectrum of severity, intellectual disability and autism spectrum disorders (ASD) are aspects of the human condition that constitute an enormous burden for affected patients and families. The fundamental limitation in our understanding of such conditions lies in the lack of meaningful models to understand the mechanisms of disease in a patient-specific manner, starting form the uniqueness of each genetic background. We focused on two neurodevelopmental disorders, Williams-Beuren Syndrome (WBS) and 7dup autism-spectrum disorder (7DUP), which result from genetic changes that either half (WBS) or increase by half (7DUP) the amount of expression of a small set of genes (gene dosage) in chromosome 7. These disorders manifest physical, intellectual and behavioural features that are either directly or inversely related to their respective gene dosage and thus also represent a unique opportunity to understand, in humans, how the dosage of just a few genes underlies quintessential features of the human condition, such as cognition, language and sociality.
The advent in 2006 of the Nobel prize winning technology known as somatic cell reprogramming, constituted a game changer in our ability to convert any cell of our body into stem cells which have the potential to be differentiated into any desired tissue, also known as induced-pluripotent stem cells (iPSCs). During this project, we obtained cells (usually from skin) from individuals with these disorders and their unaffected relatives and assembled for these two disorders the largest available cohort of iPSCs, which we then differentiated in vitro into neurons and neural crest cells, two of the cell types that are particularly affected in these syndromes.
The cells that make our face and brain...... in a dish
Our characterization of the fundamental properties of patients’ iPSCs, such as the global way in which their genome is regulated, showed first of all that iPSCs are per se predictive of future physiological manifestations. To study in detail the tissues affected in these disorders, we produced in vitro neural crest stem cells (NCS, which are precursors of the cells composing the key structures of our face) and cells from the brain cortex in 2- and 3-dimensional cultures (also known as brain organoids). These models recapitulated salient morphological and functional features of human fetal development. In the course of this validation process, we confirmed that cortical brain organoids display the key cell subpopulations that originate the neuronal diversity in the developing human fetal cortex (progenitor cells) and, interestingly, discovered that the enzyme GSK3 is essential in the production and organization of such progenitors.
A remarkable connection with human evolution
Interestingly, the comparison of molecular information from our patient-derived NCS and genetic information inferred from human ancestors (Neanderthals and Denisovans), allowed us to provide the first experimental evidence to support the recently-emerging view that humans facial features and brain shape are likely the result of an evolutionary process of “self-domestication”, in which humans have become morphologically and behaviourally more “docile” over time. Specifically, the fact that certain characteristics of the syndromes we studied in this project amplify specific traits resulting from human evolution allowed us to narrow down the molecular underpinning of such self-domestication process to the levels of the gene “BAZ1B”, one of the genes affected in WBS and 7DUP, that controls the early production of NCS.
Therapeutic perspective.
Looking in detail at our in vitro brain models, we discovered that the brain cortex of patients with WBS mature at a slower rate, opposite to 7DUP in maturation is faster. We pursued this discovery all the way down to the resolution of individual cells in brain organoids derived from patients, and thereby found that one gene in particular, “GTF2I”, is central to the regulation of this maturation dynamics. We thus invested major efforts to translate these and related findings, screening vast libraries of chemical compounds on patient-derived neurons grown in the dish and succeeding in the identification of highly selective chemicals that revert the key alterations underlying the two syndromes, and which we now wish to advance towards preclinical development.