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DNA methylation plays an important role in the development and etiology of type 2 diabetes; however, few epigenomic studies have been conducted on twins. Herein, a two-stage study was performed to explore the associations between DNA methylation and type 2 diabetes, fasting plasma glucose, and HbA1c. DNA methylation in 316 twin pairs from the Chinese National Twin Registry (CNTR) was measured using Illumina Infinium BeadChips. In the discovery sample, the results revealed that 63 CpG sites and 6 CpG sites were significantly associated with fasting plasma glucose and HbA1c, respectively. In the replication sample, cg19690313 in TXNIP was associated with both fasting plasma glucose (P = 1.23 × 10-17, FDR < 0.001) and HbA1c (P = 2.29 × 10-18, FDR < 0.001). Furthermore, cg04816311, cg08309687, and cg09249494 may provide new insight in the metabolic mechanism of HbA1c. Our study provides solid evidence that cg19690313 on TXNIP correlates with HbA1c and fasting plasma glucose levels.

Fabry disease (FD) was an X-linked lysosomal storage disorder resulting from a deficiency in glycosphingolipid catabolism caused by mutations in the α-galactosidase A gene GLA. Variant FD patients did not present with classical symptoms during childhood and were undiagnosed or misdiagnosed with other kidney diseases, such as chronic glomerulonephritis (CGN). In this study, we utilized exome sequencing and Sanger sequencing identified the variation p.E66Q of GLA completely co-segregated with the disease phenotype in a Chinese family, which previously been diagnosed as possible CGN. Female patients exhibited preferential X-chromosome inactivation (XCI) of the normal p.E66 allele, as indicated by XCI analysis. By measuring α-Gal A activity, we found that male patients in the pedigree had just little enzymatic activity while female patients had residual enzymatic activity. These patients were diagnosed with renal variant FD in subsequent clinical review. Our results directly implicated the GLA mutation p.E66Q as the genetic etiology of the Chinese renal variant FD pedigree.

AMPD1 is an adenosine monophosphate deaminase that catalyzes the deamination of AMP to IMP. To understand the physiological function of AMPD1, we obtained a strain of Ampd1 mutant mice from KOMP repository, which was generated by a knockout-first strategy. An elevated AMP level and almost complete lack of IMP was detected in the skeletal muscle of E18.5 Ampd1tm1a/tm1a mice. However, Ampd1tm1a/tm1a mice died in 2 days postnatally, which was contradicting to previous reports. After removal of the knockout-first cassette and critical exon, mice homozygous for the Ampd1tm1c/tm1c and Ampd1tm1d/tm1d alleles survived to adulthood. RNA-seq analysis indicated that the expression of two neighboring genes, Man1a2 and Nras, were disrupted in the Ampd1tm1a/tm1a mice, but normal in the Ampd1tm1c/tm1c and Ampd1tm1d/tm1d mice. The neonatal lethality phenotype in the Ampd1tm1a/tm1a mice was consistent with the Man1a2-deficient mice. Our results indicated the knockout-first cassette may cause off-target effect by influence the expression of neighboring genes. This study, together with other reports, strongly suggests that removal of targeting cassette by site-specific recombinases is very important for the accurate phenotypic interpretation on mice generated by target mutations.