Rare variants of the 3'-5' DNA exonuclease TREX1 in early onset small vessel stroke.

Background: Monoallelic and biallelic mutations in the exonuclease TREX1 cause monogenic small vessel diseases (SVD). Given recent evidence for genetic and pathophysiological overlap between monogenic and polygenic forms of SVD, evaluation of TREX1 in small vessel stroke is warranted. Methods: We sequenced the TREX1 gene in an exploratory cohort of patients with lacunar stroke (Edinburgh Stroke Study, n=290 lacunar stroke cases). We subsequently performed a fully blinded case-control study of early onset MRI-confirmed small vessel stroke within the UK Young Lacunar Stroke Resource (990 cases, 939 controls). Results: No patients with canonical disease-causing mutations of TREX1 were identified in cases or controls. Analysis of an exploratory cohort identified a potential association between rare variants of TREX1 and patients with lacunar stroke. However, subsequent controlled and blinded evaluation of TREX1 in a larger and MRI-confirmed patient cohort, the UK Young Lacunar Stroke Resource, identified heterozygous rare variants in 2.1% of cases and 2.3% of controls. No association was observed with stroke risk (odds ratio = 0.90; 95% confidence interval, 0.49-1.65 p=0.74). Similarly no association was seen with rare TREX1 variants with predicted deleterious effects on enzyme function (odds ratio = 1.05; 95% confidence interval, 0.43-2.61 p=0.91). Conclusions: No patients with early-onset lacunar stroke had genetic evidence of a TREX1-associated monogenic microangiopathy. These results show no evidence of association between rare variants of TREX1 and early onset lacunar stroke. This includes rare variants that significantly affect protein and enzyme function. Routine sequencing of the TREX1 gene in patients with early onset lacunar stroke is therefore unlikely to be of diagnostic utility, in the absence of syndromic features or family history.

Dominantly inherited cutaneous small-vessel lymphocytic vasculitis maps to chromosome 6q26-q27.

Outside the context of hereditary deficiencies of complement and IgA, Mendelian inherited predisposition to small vessel lymphocytic vasculitis (SVLV) has rarely been documented. Here we report a large, multigenerational family segregating symmetrical cutaneous SVLV affecting the cheeks, thighs and hands. In all affected family members the disease presented in early infancy and there was no evidence for an association with systemic disease. Skin biopsy of lesions showed a lymphocytic vasculitis with red blood cell extravasation. Complementary studies, with extensive investigation focused on dysfunction of the immunological system were negative. The pattern of inheritance of SVLV in the family was compatible with an autosomal dominantly acting disease gene with incomplete penetrance. To localize the disease causing gene in the family a genome-wide linkage search was conducted using a high-density SNP array. Haplotype construction and analysis of recombination events permitted the minimal interval defining the disease locus to be refined to a 4.7 Mb region on chromosome 6q26-q27. The genes CCR6 and GPR31, which map to the linked region represent plausible candidates for the disease on the basis of their biological function. Extensive screening of both genes by mutational analysis failed to identify a deleterious mutation in the family.