Polymorphism M55V in gene encoding small ubiquitin-like modifier 4 (SUMO4) protein associates with susceptibility to type 1 (and type 2) diabetes

β-Cell failure in diabetes: Common susceptibility and mechanisms shared between type 1 and type 2 diabetes

Diabetes mellitus is etiologically classified into type 1, type 2 and other types of diabetes. Despite distinct etiologies and pathogenesis of these subtypes, many studies have suggested the presence of shared susceptibilities and underlying mechanisms in β-cell failure among different types of diabetes. Understanding these susceptibilities and mechanisms can help in the development of therapeutic strategies regardless of the diabetes subtype. In this review, we discuss recent evidence indicating the shared genetic susceptibilities and common molecular mechanisms between type 1, type 2 and other types of diabetes, and highlight the future prospects as well.

SUMO: From Bench to Bedside

Sentrin/small ubiquitin-like modifier (SUMO) is protein modification pathway that regulates multiple biological processes, including cell division, DNA replication/repair, signal transduction, and cellular metabolism. In this review, we will focus on recent advances in the mechanisms of disease pathogenesis, such as cancer, diabetes, seizure, and heart failure, which have been linked to the SUMO pathway. SUMO is conjugated to lysine residues in target proteins through an isopeptide linkage catalyzed by SUMO-specific activating (E1), conjugating (E2), and ligating (E3) enzymes. In steady state, the quantity of SUMO-modified substrates is usually a small fraction of unmodified substrates due to the deconjugation activity of the family Sentrin/SUMO-specific proteases (SENPs). In contrast to the complexity of the ubiquitination/deubiquitination machinery, the biochemistry of SUMOylation and de-SUMOylation is relatively modest. Specificity of the SUMO pathway is achieved through redox regulation, acetylation, phosphorylation, or other posttranslational protein modification of the SUMOylation and de-SUMOylation enzymes. There are three major SUMOs. SUMO-1 usually modifies a substrate as a monomer; however, SUMO-2/3 can form poly-SUMO chains. The monomeric SUMO-1 or poly-SUMO chains can interact with other proteins through SUMO-interactive motif (SIM). Thus SUMO modification provides a platform to enhance protein-protein interaction. The consequence of SUMOylation includes changes in cellular localization, protein activity, or protein stability. Furthermore, SUMO may join force with ubiquitin to degrade proteins through SUMO-targeted ubiquitin ligases (STUbL). After 20 yr of research, SUMO has been shown to play critical roles in most, if not all, biological pathways. Thus the SUMO enzymes could be targets for drug development to treat human diseases.

Association of donor and recipient SUMO4 rs237025 genetic variant with new-onset diabetes mellitus after liver transplantation in a Chinese population

BACKGROUNDS & AIMS

New-onset diabetes mellitus (NODM) is a common complication after liver transplantation (LT). The small ubiquitin-like modifier 4 (SUMO4) rs237025 polymorphism has been reported to be associated with type 2 diabetes mellitus (T2DM). In this study, we aimed to evaluate the association of donor and recipient SUMO4 rs237025 polymorphisms with NODM and the long-term consequences of NODM after LT.

METHODS

A total of 126 liver transplant patients were enrolled in the study. One single nucleotide polymorphism, SUMO4 rs237025, was genotyped in both donors and recipients.

RESULTS

Both donor and recipient SUMO4 rs237025 polymorphisms were found to be significantly associated with NODM after LT. In multivariate analysis, recipient age>50 years, tacrolimus trough concentrations>10ng/mL at 1month after LT, donor and recipient rs237025 genetic variant, and the combined donor and recipient rs237025 genetic variant were independent predictive factors of NODM. Area under the receiver operating characteristic curve (AUROC) analysis indicated the higher predictive ability of the model containing combined donor and recipient rs237025 polymorphisms than the clinical model (p=0.046). Furthermore, Kaplan-Meier survival analysis demonstrated that NODM was related to significantly poorer patient survival in comparison with non-NODM patients (p=0.041).

CONCLUSIONS

Both donor and recipient SUMO4 rs237025 polymorphisms contribute to the development of NODM after LT and NODM is a frequent complication that negatively affects patient survival.

Small Ubiquitin-Like Modifier 4 (SUMO4) Gene M55V Polymorphism and Type 2 Diabetes Mellitus: A Meta-analysis Including 6,823 Subjects

BACKGROUND

Many studies suggest that the small ubiquitin-like modifier 4 (SUMO4) M55V gene polymorphism (rs237025) may be associated with an increased risk of type 2 diabetes mellitus (T2DM). However, due to other conflicting results, a clear consensus is lacking in the matter.

OBJECTIVE AND METHODS

A meta-analysis consisting of 6,823 subjects from 10 studies was conducted to elucidate relationship between the SUMO4 M55V gene polymorphism and T2DM. Depending on the heterogeneity of the data, either a fixed or random-effects model would be used to assess the combined odds ratio (ORs) and their corresponding 95% confidence interval (CI).

RESULTS

SUMO4 gene M55V polymorphism was significantly associated with T2DM in the whole population under allelic (OR: 1.18, 95% CI: 1.10-1.28, P = 1.63 × 10^-5), recessive (OR: 1.59, 95% CI: 1.14-2.23, P = 0.006), dominant (OR: 0.815, 95% CI: 0.737-0.901, P = 6.89 × 10^-5), homozygous (OR: 1.415, 95% CI: 1.170-1.710, P = 0.0003), heterozygous (OR: 1.191, 95% CI: 1.072-1.323, P = 0.001), and additive genetic models (OR: 1.184, 95% CI: 1.097-1.279, P = 1.63 × 10^-5). In our subgroup analysis, a significant association was found again in the Chinese population, but not in Japanese or Iranian population.

CONCLUSION

SUMO4 gene M55V polymorphism may correlate with increased T2DM risk. Chinese carriers of the V allele of the SUMO4 gene M55V polymorphism may be predisposed to developing T2DM.

Variations in COL15A1 and COL18A1 influence age of onset of primary open angle glaucoma

Primary open angle glaucoma (POAG) is a genetically and phenotypically complex disease that is a leading cause of blindness worldwide. Previously we completed a genome-wide scan for early-onset POAG that identified a locus on 9q22 (GLC1J). To identify potential causative variants underlying GLC1J, we used targeted DNA capture followed by high throughput sequencing of individuals from four GLC1J pedigrees, followed by Sanger sequencing to screen candidate variants in additional pedigrees. A mutation likely to cause early-onset glaucoma was not identified, however COL15A1 variants were found in the youngest affected members of 7 of 15 pedigrees with variable disease onset. In addition, the most common COL15A1 variant, R163H, influenced the age of onset in adult POAG cases. RNA in situ hybridization of mouse eyes shows that Col15a1 is expressed in the multiple ocular structures including ciliary body, astrocytes of the optic nerve and cells in the ganglion cell layer. Sanger sequencing of COL18A1, a related multiplexin collagen, identified a rare variant, A1381T, in members of three additional pedigrees with early-onset disease. These results suggest genetic variation in COL15A1 and COL18A1 can modify the age of onset of both early and late onset POAG.