Endothelial Cells from Capillary Malformations are Enriched for Somatic GNAQ Mutations and Aberrantly Express PDGFRβ
Javier A. Couto, BS1, Lan Huang, PhD1, Matthew P. Vivero, BA1, Nolan Kamitaki, BA2, Reid A. Maclellan, MD, MMSc1, John B. Mulliken, MD1, Joyce Bischoff, PhD1, Matthew L. Warman, MD1, Arin K. Greene, MD, MMSc1.
1Boston Children's Hospital, Harvard Medical School, Boston, MA, USA, 2Harvard Medical School, Boston, MA, USA.
A somatic mutation in GNAQ (c.548G>A, p.R183Q), encoding Gαq, has been found in capillary malformation (CM) tissue. However, the specific cell type(s) containing the mutation is unknown. The purpose of this study was to determine which cells in CMs have the GNAQ mutation.
CM tissue was obtained from 12 patients during a clinically-indicated procedure. Droplet digital PCR (ddPCR) was used to quantify the frequency of GNAQ mutant cells in CM tissue. Five specimens were fractionated by fluorescence activated cell sorting (FACS) into hematopoietic, endothelial, perivascular, and stromal cells. The frequency of GNAQ mutant cells in these populations was quantified by ddPCR. CM tissues were immunostained for endothelial and perivascular cell markers and analyzed by confocal microscopy.
Seven CMs contained GNAQ p.R183Q mutant cells, 2 lesions had novel GNAQ mutations (p.R183L; p.R183G), and 3 CMs did not have a detectable GNAQ mutation. Mutant allelic frequencies ranged from 2% to 7%. Following FACS, the GNAQ mutation was enriched in the endothelial but not the perivascular cell population; mutant allelic frequencies were 3% to 42% (Figure). Endothelial cells abnormally expressed the perivascular marker PDGFRβ.
Three different mutations affecting amino acid residue p.R183 in GNAQ can cause CM. Endothelial cells in CMs are enriched for GNAQ mutations and can aberrantly express PDGFRβ. Mutant endothelial cells are likely responsible for the pathophysiology underlying CM.
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