Switch in FGFR3 and-4 Expression Profile During Human Renal Development May Account for Transient Hypercalcemia in Patients With Sotos Syndrome due to 5q35 Microdeletions

Context: Sotos syndrome is a rare genetic disorder with a distinct phenotypic spectrum including overgrowth and learning difficulties. Here we describe a new case of Sotos syndrome with a 5q35 microdeletion, affecting the fibroblast growth factor receptor 4 (FGFR4) gene, presenting with infantile hypercalcemia. Objective: We strived to elucidate the evanescent nature of the observed hypercalcemia by studying the ontogenesis of FGFR3 and FGFR4 - which are both associated with FGF23-mediated mineral homeostasis - in the developing human kidney. Design: RT-qPCR and immunohistochemical analyses were used on archival human kidney samples to investigate expression of the FGFR signaling pathway during renal development. Results: We demonstrated that renal gene and protein expression of both FGFRs increased during fetal development between the gestational ages (GA) of 14-40 weeks. Yet, FGFR4 expression increased more rapidly as compared to FGFR3 (slope: 0.047 vs. 0.0075, p = 0.0018). Moreover, gene and protein expression of the essential FGFR co-receptor, Klotho, also increased with a significant positive correlation between FGFR and Klotho mRNA expression during renal development. Interestingly, we found that perinatal FGFR4 expression (GA 38-40 weeks) was 7-fold higher as compared to FGFR3 (p=0.0035), while in adult kidney tissues, FGFR4 gene expression level was more than 2-fold lower compared to FGFR3 (p=0.0029), thus identifying a molecular developmental switch of FGFR isoforms. Conclusion: We propose that the heterozygous FGFR4 deletion, as observed in the Sotos syndrome patient, leads to a compromised FGF23 signaling during infancy accounting for transient hypercalcemia. These findings represent a novel and intriguing view on FGF23-mediated calcium homeostasis.

Jaar van publicatie:2014

BOF-keylabel:ja

IOF-keylabel:ja

BOF-publication weight:3

CSS-citation score:1

Auteurs:International

Authors from:Higher Education

Toegankelijkheid:Closed