Purpose: To identify the genetic cause of aggressive corneal neovascularization arising in otherwise healthy children in one family. Further, to study molecular consequences associated with the ...identified variant and implications for possible precision medicine treatment.
Methods: Sanger sequencing of the candidate gene PDGFRB was performed in affected individuals. HeLa cells were transduced with wild type PDGFRB and the identified variant. Cells were treated with tyrosine kinase inhibitors (TKIs). ELISA and immunoblot analysis were used to detect phosphorylation of PDGFRβ and downstream signalling proteins.
Results: A novel variant in PDGFRB was found in affected family members. HeLa cells transduced with this variant did not have increased baseline levels of phosphorylated PDGFRb. However, upon stimulation with ligand, excessive activation of PDGFRb was observed in these cells compared to cells transduced with the wild type variant. Inhibition with some TKIs in vitro successfully prevented upregulation of PDGFRβ and its downstream signalling.
Conclusions: A novel substitution in PDGFRB was found in family members with isolated corneal neovascular overgrowth. Cells transduced with the variant showed increased phosphorylation upon ligand stimulation. While the examined TKIs had various effects in preventing such overactivation, this introduces the concept of precision medicine in preventing childhood blindness in these patients.
PurposeThe purpose of this study was to identify the genetic cause of aggressive corneal vascularization in otherwise healthy children in one family. Further, to study molecular consequences ...associated with the identified variant and implications for possible treatment.MethodsExome sequencing was performed in affected individuals. HeLa cells were transduced with the identified c.1643C>A, p.(Ser548Tyr) variant in the platelet-derived growth factor receptor beta gene (PDGFRB) or wild-type PDGFRB. ELISA and immunoblot analysis were used to detect the phosphorylation levels of PDGFRβ and downstream signaling proteins in untreated and ligand-stimulated cells. Sensitivity to various receptor tyrosine kinase inhibitors (TKIs) was determined.ResultsA novel c.1643C>A, p.(Ser548Tyr) PDGFRB variant was found in affected family members. HeLa cells transduced with this variant did not have increased baseline levels of phosphorylated PDGFRβ. However, upon stimulation with ligand, excessive activation of PDGFRβ was observed compared to cells transduced with the wild-type variant. PDGFRβ with the p.(Ser548Tyr) amino acid substitution was successfully inhibited with tyrosine kinase inhibitors (axitinib, dasatinib, imatinib, and sunitinib) in vitro.ConclusionsA novel c.1643C>A, p.(Ser548Tyr) PDGFRB variant was found in family members with isolated corneal vascularization. Cells transduced with the newly identified variant showed increased phosphorylation of PDGFRβ upon ligand stimulation. This suggests that PDGF-PDGFRβ signaling in these patients leads to overactivation of PDGFRβ, which could lead to abnormal wound healing of the cornea. The examined TKIs prevented such overactivation, introducing the possibility for targeted treatment in these patients.
Penttinen type of premature aging syndrome is an autosomal‐dominant disorder that can be caused by the c.1994T>A pVal665Ala pathogenic variant in platelet‐derived growth factor receptor‐B (PDGFRB). ...Imatinib, a receptor tyrosine kinase (RTK) inhibitor, has been used in Penttinen syndrome (PS) patients with good results. A 21‐year‐old male presented shortly after birth with a prematurely aged appearance with distinctive facial features and cutaneous atrophy with hypertrophic scar‐like lesions. Generalized brachydactyly with acro‐osteolysis was observed. Flexion contractures limited his daily activities. Cognitive impairment was not present. Genetic testing found a heterozygous variant c.1994T>A pVal665Ala in exon 14 of PDGFRB. A diagnosis of PS was made and imatinib treatment was started with partial response. After lack of further improvement, in vitro molecular studies with imatinib and dasatinib showed that the Val665Ala variant had greater sensitivity to dasatinib than imatinib. This was seen examining levels of P‐PDGFRB directly and on downstream ligands P‐AKT and P‐STAT. Improved clinical response was observed after treatment with dasatinib. We report a new case of PS with clinical and molecular response to dasatinib after incomplete response to imatinib. Our work provides further molecular and clinical evidence of RTK inhibitors' efficacy in this rare disorder.
