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Expanding Genetic and Functional Diagnoses of IGF1R Haploinsufficiencies #MMPMID28395282
Horm Res Paediatr 2017[]; 87 (6): 412-22 PMID28395282show ga
Background: The growth-promoting effects of IGF-I is mediated through the IGF-I receptor (IGFIR), a widely expressed, cell-surface tyrosine kinase receptor. IGF1R copy number variants (CNV) can cause pre- and postnatal growth restriction or overgrowth. Methods: Whole exome sequence (WES), chromosomal microarray and targeted IGF1R gene analyses were performed on three unrelated children who share features of SGA, short stature, and elevated serum IGF-I, but otherwise had clinical heterogeneity. FACS (fluorescence-activated cell sorting) analysis of cell surface IGF1R was performed on live primary cells derived from the patients. Results: Two novel IGF1R CNV and a heterozygous IGF1R nonsense variant were identified in the three patients. One CNV (4.492 Mb) was successfully called from WES, utilizing eXome-Hidden Markov Model (XHMM) analysis. FACS analysis of cell surface IGFIR on live primary cells derived from the patients demonstrated ~50% reduction in IGFIR availability associated with the haploinsufficiency state. Conclusion: In addition to conventional methods, IGF1R CNVs can be identified from WES data. FACS analysis of live primary cells is a promising method for efficiently evaluating and screening for IGFIR haploinsufficiency. Further investigations are necessary to delineate how comparable IGFIR availability lead to the wide spectrum of clinical phenotypes and variable responsiveness to rhGH therapy.