7q11.23 dosage-dependent dysregulation in the human pluripotent state primes aberrant transcriptional programs in disease-relevant lineages (RNAseq)

We apply the cellular reprogramming experimental paradigm to two disorders caused by symmetrical copy number variations (CNV) of 7q11.23 and displaying a striking combination of shared as well as symmetrically opposite phenotypes: Williams Beuren syndrome (WBS) and 7q microduplication syndrome (7dupASD). Through a uniquely large and informative cohort of transgene-free patient-derived induced pluripotent stem cells (iPSC), along with their differentiated derivatives, we find that 7q11.23 CNV disrupt transcriptional circuits in disease-relevant pathways already at the pluripotent state. These alterations are then selectively amplified upon differentiation into disease-relevant lineages, thereby establishing the value of large iPSC cohorts in the elucidation of disease-relevant developmental pathways. In addition, we functionally define the quota of transcriptional dysregulation specifically caused by dosage imbalances in GTF2I (also known as TFII-I), a transcription factor in 7q11.23 thought to play a critical role in the two conditions, which we found associated to key repressive chromatin modifiers. Finally, we created an open-access web-based platform (accessible at http://bio.ieo.eu/wbs/ ) to make accessible our multi-layered datasets and integrate contributions by the entire community working on the molecular dissection of the 7q11.23 syndromes. Overall design: We reprogrammed skin fibroblasts from patients harbouring a 7q11.23 hemi-deletion (WBS, 4 patients; +1 atypical deletion, AtWBS) or microduplication (7dupASD; 2 patients), as well as from one unaffected relative and two unrelated controls, using integration-free mRNA-reprogramming, leading to the establishment of a total of 27 characterized iPSC clones. We profiled these by RNAseq (either polyA or ribo-zero). To isolate the contribution of GTF2I to the transcriptional dysregulation, we created stable lines expressing a short hairpin against GTF2I from a representative subset of these iPSC clones, and profiled by RNAseq 7 such lines along with their respective scramble controls. Finally, we also profiled by RNAseq mesenchymal stem cells (MSC) derived from a representative subset of the lines.

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Germain PL, Vitriolo A, Adamo A, Laise P, Das V, Testa G