ABSTRACT
Fabry disease (FD) is a rare inherited disease characterized by a wide range of symptoms attributed to GLA mutations resulting in defective α-galactosidase A (α-Gal A) and accumulation of glycosphingolipids. The GLA locus is paired in a divergent manner with the heterogeneous nuclear ribonucleoprotein HNRNPH2 locus mapped in the RPL36A-HNRNPH2 readthrough locus. As a follow-up to our recent finding of the co-regulation of GLA and HNRNPH2 via a bidirectional promoter (BDP) in normal kidney and skin cells, the potential accumulative influence of BDP methylation and GLA mutation on the severity of FD in patients from the same family, two males and two females carrying a GLA deletion mutation, c.1033_1034delTC (p.Ser345Argfs) was addressed in the present study. The molecular analyses of the FD patients compared with the control revealed that the expression of GLA was significantly low (P<0.05), and HNRNPH2 showed a tendency of low expression (P=0.1) when BDP methylation was elevated in FD patients, compared with low BDP methylation and high GLA expression (P<0.05), and a high trend of HNRNPH2 expression in normal individuals. The accumulative effects of the mutation and BDP methylation with the severity of the disease were observed in three patients. One male FD patient, a member of the FD family diagnosed with progressive loss of kidney function, hypertension, and eventually a stroke, and the lowest level of α-Gal A enzyme activity showed the highest BDP DNA methylation level. It is concluded that the DNA methylation of GLA-HNRNPH2 BDP may serve a role in diagnosing and treating FD.
ABSTRACT
Fabry disease (FD) is a rare hereditary disorder characterized by a wide range of symptoms caused by a variety of mutations in the galactosidase α (GLA) gene. The heterogeneous nuclear ribonucleoprotein (HNRNPH2) gene is divergently paired with GLA on chromosome X and is thought to be implicated in FD. However, insufficient information is available on the regulatory mechanisms associated with the expression of HNRNPH2 and the GLA loci. Therefore, the current study performed bioinformatics analyses to assess the GLA and HNRNPH2 loci and investigate the regulatory mechanisms involved in the expression of each gene. The regulatory mechanisms underlying GLA and HNRNPH2 were revealed. The expression of each gene was associated with a bidirectional promoter (BDP) characterized by the absence of TATA box motifs and the presence of specific transcription factor binding sites (TFBSs) and a CpG Island (CGI). The nuclear run-on transcription assay confirmed the activity of BDP GLA and HNRNPH2 transcription in 293T. Methylation-specific PCR analysis demonstrated a statistically significant variation in the DNA methylation pattern of BDP in several cell lines, including human adult epidermal keratinocytes (AEKs), human renal glomerular endothelial cells, human renal epithelial cells and 293T cells. The highest observed significance was demonstrated in AEKs (P<0.05). The results of the chromatin-immunoprecipitation assay using 293T cells identified specific TFBS motifs for Yin Yang 1 and nuclear respiratory factor 1 transcription factors in BDPs. The National Center for Biotechnology Information-single nucleotide polymorphism database revealed pathogenic variants in the BDP sequence. Additionally, a previously reported variant associated with a severe heterozygous female case of GLA FD was mapped in BDP. The results of the present study suggested that the expression of the divergent paired loci, GLA and HNRNPH2, were controlled by BDP. Mutations in BDP may also serve a role in FD and may explain clinical disease diversity.
