Additional glomangioma families link to chromosome 1p: no evidence for genetic heterogeneity

Genetic analysis of a family with hereditary glomuvenous malformations

Glomuvenous malformations (MIM 138000) are rare vascular malformations consisting of glomus cells, and in affected individuals, lesions may appear in any number anywhere on the body. We analysed the DNA of one family with hereditary glomuvenous malformations and identified the mutation causing the disease in the glomulin gene on chromosome 1 p22. The deletion started at base pair 157: 157delAAGAA, which is a deletion of five base pairs. This mutation has been found in Europe, the USA and Australia, suggesting a founder effect with common ancestry. Thus far, no second-hit mutation for the 157delAAGAA mutation has been identified.

Mutations in a novel factor, glomulin, are responsible for glomuvenous malformations ("glomangiomas")

Glomuvenous malformations (GVMs) are cutaneous venous lesions characterized by the presence of smooth-muscle--like glomus cells in the media surrounding distended vascular lumens. We have shown that heritable GVMs link to a 4--6-cM region in chromosome 1p21-22. We also identified linkage disequilibrium that allowed a narrowing of this VMGLOM locus to 1.48 Mb. Herein, we report the identification of the mutated gene, glomulin, localized on the basis of the YAC and PAC maps. An incomplete cDNA sequence for glomulin had previously been designated "FAP48," for "FKBP-associated protein of 48 kD." The complete cDNA for glomulin contains an open reading frame of 1,785 nt encoding a predicted protein of 68 kD. The gene consists of 19 exons in which we identified 14 different germline mutations in patients with GVM. In addition, we found a somatic "second hit" mutation in affected tissue of a patient with an inherited genomic deletion. Since all but one of the mutations result in premature stop codons, and since the localized nature of the lesions could be explained by Knudson's two-hit model, GVMs are likely caused by complete loss of function of glomulin. The abnormal phenotype of vascular smooth-muscle cells (VSMCs) in GVMs suggests that glomulin plays an important role in differentiation of these cells--and, thereby, in vascular morphogenesis--especially in cutaneous veins.