X-chromosome inactivation patterns in females with Fabry disease examined by both ultra-deep RNA sequencing and methylation-dependent assay
Abstract Background: Fabry disease is an X-linked inherited lysosomal storage disorder related to GLA mutations, gene encoding α-galactosidase A. In general, males has severe phenotype, while females has a wide spectrum of sign and symptoms, from asymptomatic to a more classical profile including cardiac, renal, and cerebrovascular manifestations. This variability has been assumed to be derived from organ-dependent skewed X-chromosome inactivation (XCI) patterns in each female patient. Some previous studies examined this correlation using the classical methylation-dependent method; however, conflicting results were obtained. This study was established to determine the existence of skewed XCI in nine females with heterozygous pathogenic variants in the GLA gene and its relationship to the phenotypes. Methods: We present five female patients from one family and four individual female patients with Fabry disease. In all cases, heterozygous pathogenic variants in the GLA gene were detected. The X-chromosome inactivation patterns in peripheral blood leukocytes and cells of urine sediment were determined by both classical methylation-dependent HUMARA assay and ultra-deep RNA sequencing, the latter being a method that we recently developed. Results: Among all cases, skewed XCI resulting in predominant inactivation of the normal allele was observed only in one individual case with a severe phenotype. In the other eight cases, no skewing was observed, even among cases with severe phenotypes. Conclusions: We conclude that skewed XCI could explain the severity of Fabry disease in only a limited number of female cases and is not the main factor in the onset of various clinical symptoms in females with Fabry disease.