Case Report: A heterozygous loss-of-function variant of the ERG gene in a family with vascular pathologies

Abstract

Background: The transcription factor ERG (erythroblast transformation-specific-related gene) has been identified as a key regulator of vascular function by suppressing inflammation in endothelial cells (ECs). Dysregulation of ERG due to genetic risk variants is linked to chronic inflammation in conditions such as atherosclerosis and aortic aneurysms.

Case presentation: This research work investigates the role of the ERG gene in the development of a systemic arterial aneurysm manifestation. Given the previous implication of ERG in vascular development, we now report a loss-of-function variant (Leu212*) in the ERG gene, segregating in a family with vascular pathologies. Multiple arterial aneurysms were observed in one family member, and early onset of vascular-associated stroke in another individual carrying the familial ERG variant. Histological analysis of arterial aneurysm specimen showed comparable expression of ERG in endothelial cells of the vasa vasorum in samples from the patient and controls.

Conclusion: Our report discusses the possibility that loss-of-function variants in ERG may act as a risk factor for arterial disease.

Keywords: ERG; abdominal aortic aneurysm; haploinsufficiency; loss-of-function variant; multiple arterial aneurysms.

Figure 1

Structure of the human ERG gene and protein. Structure of the human ERG gene and protein p55, according to the nomenclature suggested by Zammarchi (9). Top: schematic representation of ERG coding exons (encoding eight isoforms), shown with their size in base pairs (bp) below each exon. Middle: genomic region of ERG isoform p55, showing position of the affected exon and the STOP codon, predicted size of the WT and mutant allele. Below: the ERG/p55 exon structure and nucleotide length (in base pairs) is aligned with the predicted protein sequence showing the amino acid position of the main protein domains. PNT (pointed domain), ETS (ETS DNA-binding domain). The phosphorylated serine residue at position 215 is indicated by an arrow.

Figure 2

Multiple aneurysms in an individual with ERG haploinsufficiency. (A) 3-dimensional reconstruction of the computed tomography angiography of the index patient revealed multiple aneurysm formation. Red arrows indicate aneurysmatic vascular segments. (B) Family pedigree including the index patient with multiple arterial aneurysms (age 52 years) and an affected son (18 years) with cervical artery dissection and the same ERG gene variant. Other family members were not available for Sanger sequencing analysis. WT/WT: wild type homozygous, WT/MUT: heterozygous variant, white coloration: investigated without phenotype, black coloration: affected individual, grey: clinically not investigated. (C) Immunohistochemically and magnification (indicated by black rectangles) stained sections comparing the abdominal aortic aneurysm (AAA) of the index patient and a healthy control aorta. Staining of sequential histological sections with antibodies for ERG, CD31, αSMA and CD45 revealed expression of ERG exclusively in individual endothelial cells (red arrows) of the vasa vasorum in a similar extent and pattern as in healthy aortas. Scale bars: 100 μm (top) and 50 μm (magnification sections). Red arrows indicate ERG-positive cells in the area of the tunica media (index patient) and in the transition zone between the tunica media and tunica adventitia (control sample).

Figure 3

Relative mRNA expression of ERG and endothelial ERG target genes in aneurysmatic and control aortic tissues. Data are shown as the mean with SD of three technical replicates. Statistical analysis was performed by ordinary one-way ANOVA with Dunnett's multiple comparison test. *: P < 0.05; ***: P < 0.001; ****: P < 0.0001. ACTB, actin beta; Aorta Co1 and Aorta Co2, control aortic specimen 1 and 2; ICAM2, intercellular adhesion molecule 2; CDH5, cadherin-5; CLDN5, claudin-5; GADPH, glyceraldehyde-3-phosphate dehydrogenase; ns, not significant; NOTCH4, neurogenic locus notch homolog 4; VE-Cad, vascular endothelial (VE)-cadherin.