Lack of association between polymorphisms of the DNA base excision repair genes MUTYH and hOGG1 and keratoconus in a Polish subpopulation

MUTYH: Not just polyposis

MUTYH is a base excision repair enzyme, it plays a crucial role in the correction of DNA errors from guanine oxidation and may be considered a cell protective factor. In humans it is an adenine DNA glycosylase that removes adenine misincorporated in 7,8-dihydro-8-oxoguanine (8-oxoG) pairs, inducing G:C to T:A transversions. MUTYH functionally cooperates with OGG1 that eliminates 8-oxodG derived from excessive reactive oxygen species production. MUTYH mutations have been linked to MUTYH associated polyposis syndrome (MAP), an autosomal recessive disorder characterized by multiple colorectal adenomas. MAP patients show a greatly increased lifetime risk for gastrointestinal cancers. The cancer risk in mono-allelic carriers associated with one MUTYH mutant allele is controversial and it remains to be clarified whether the altered functions of this protein may have a pathophysiological involvement in other diseases besides familial gastrointestinal diseases. This review evaluates the role of MUTYH, focusing on current studies of human neoplastic and non-neoplastic diseases different to colon polyposis and colorectal cancer. This will provide novel insights into the understanding of the molecular basis underlying MUTYH-related pathogenesis. Furthermore, we describe the association between MUTYH single nucleotide polymorphisms (SNPs) and different cancer and non-cancer diseases. We address the utility to increase our knowledge regarding MUTYH in the light of recent advances in the literature with the aim of a better understanding of the potential for identifying new therapeutic targets. Considering the multiple functions and interactions of MUTYH protein, its involvement in pathologies based on oxidative stress damage could be hypothesized. Although the development of extraintestinal cancer in MUTYH heterozygotes is not completely defined, the risk for malignancies of the duodenum, ovary, and bladder is also increased as well as the onset of benign and malignant endocrine tumors. The presence of MUTYH pathogenic variants is an independent predictor of poor prognosis in sporadic gastric cancer and in salivary gland secretory carcinoma, while its inhibition has been shown to reduce the survival of pancreatic ductal adenocarcinoma cells. Furthermore, some MUTYH SNPs have been associated with lung, hepatocellular and cervical cancer risk. An additional role of MUTYH seems to contribute to the prevention of numerous other disorders with an inflammatory/degenerative basis, including neurological and ocular diseases. Finally, it is interesting to note that MUTYH could be a new therapeutic target and future studies will shed light on its specific functions in the prevention of diseases and in the improvement of the chemo-sensitivity of cancer cells.

Genetic Aspects of Keratoconus: A Literature Review Exploring Potential Genetic Contributions and Possible Genetic Relationships with Comorbidities

INTRODUCTION

Keratoconus (KC) is a complex, genetically heterogeneous, multifactorial degenerative disorder that is accompanied by corneal ectasia which usually progresses asymmetrically. With an incidence of approximately 1 per 2000 and 2 cases per 100,000 population presenting annually, KC follows an autosomal recessive or dominant pattern of inheritance and is, apparently, associated with genes that interact with environmental, genetic, and/or other factors. This is an important consideration in refractive surgery in the case of familial KC, given the association of KC with other genetic disorders and the imbalance between dizygotic twins. The present review attempts to identify the genetic loci contributing to the different KC clinical presentations and relate them to the common genetically determined comorbidities associated with KC.

METHODS

The PubMed, MEDLINE, Google Scholar, and GeneCards databases were screened for KC-related articles published in English between January 2006 and November 2017. Keyword combinations of "keratoconus," "risk factor(s)," "genetics," "genes," "genetic association(s)," and "cornea" were used. In total, 217 articles were retrieved and analyzed, with greater weight placed on the more recent literature. Further bibliographic research based on the 217 articles revealed another 124 relevant articles that were included in this review. Using the reviewed literature, an attempt was made to correlate genes and genetic risk factors with KC characteristics and genetically related comorbidities associated with KC based on genome-wide association studies, family-based linkage analysis, and candidate-gene approaches.

RESULTS

An association matrix between known KC-related genes and KC symptoms and/or clinical signs together with an association matrix between identified KC genes and genetically related KC comorbidities/syndromes were constructed.

CONCLUSION

Twenty-four genes were identified as potential contributors to KC and 49 KC-related comorbidities/syndromes were found. More than 85% of the known KC-related genes are involved in glaucoma, Down syndrome, connective tissue disorders, endothelial dystrophy, posterior polymorphous corneal dystrophy, and cataract.

Relationship between urine lipid peroxidation, anthropometric parameters and parameters associated with goitre formation in school-age children

INTRODUCTION

Oxidative stress has been implicated in the normal ageing process and the pathogenesis of several diseases, including goitre. The aim of the study was to evaluate the relationship between urine lipid peroxidation (LPO) and anthropometric parameters as well as the parameters associated with goitre formation in children.

MATERIAL AND METHODS

The subjects included 172 healthy children (93 girls and 79 boys) aged 8-15, divided into 4 age groups - group I (8-9 years), group II (10-11 years), group III (12-13 years) and group IV (14-15 years) - and into 2 groups based on the BSA: the BSA-1 group (≤ 0.55 m²) and the BSA-2 group (> 0.55 m²).

RESULTS

The value of LPO was the highest in group I but the difference between the groups was not statistically significant (p = 0.074). In the BSA-1 group, the LPO was higher than in the BSA-2 group (12.75 ±6.90 nmol/ml and 10.79 ±4.86 nmol/ml, respectively; p = 0.023). We found a weak, negative linear correlation between LPO and age (r = -0.216; p < 0.005), body mass (r = -0.153; p < 0.05), height (r = -0.152; p < 0.05) and BSA (r = -0.151; p < 0.05).

CONCLUSIONS

Anthropometric parameters of school-age children independently of age are negatively associated with oxidative damage to membrane lipids, whereas factors promoting goitrogenesis do not contribute to this process.

Genetic Investigation of Polymorphic OGG1 and MUTYH Genes Towards Increased Susceptibility in Lung Adenocarcinoma and its Impact on Overall Survival of Lung Cancer Patients Treated with Platinum Based Chemotherapy

Genes OGG1 and MUTYH are the two primary genes in Base excision repair pathway. OGG1 hydrolyzes the sugar phosphate backbone and remove the damaged base creating abasic site. MUTYH complements OGG1 as it particularly remove adenine mispaired with 8-oxo-G. Both OGG1 and MUTYH act as a check for the mis-incorporation of bases may be due to damages incurred on DNA. DNA isolation for 326 lung cancer cases and 330 controls was followed by genotyping making use of PCR-RFLP. Logistic regression was done to analyze the risk towards lung cancer. Patients were followed through telephonic conversation. Kaplan meier and Cox-regression were used for survival analysis. OGG1 presented a high risk towards lung cancer (CG: OR = 2.44, p = 0.0003; CG + GG: OR = 1.88, p = 0.0093). On the same lines adenocarcinoma for OGG1 were potent risk factors towards lung cancer (CG: OR = 4.72, p = 0.0002; CG + GG: OR = 3.63, p = 0.0018). Single allelic carriers for MUTYH gene imposed a high risk towards overall lung susceptibility and for all the three histology. Stratified analysis for chemotherapeutic drugs revealed administration of Cisplatin/Carboplatin + Pemtrexed for OGG1Ser ³²⁶ Cys showed a better survival (MST CG vs. CC: 9.1 vs. 0.56, p = <0.0001; HR =0.051, p = 0.0025). Whereas, MUTYH Gln³²⁴His showed a smaller survival for mutant genotype (CC) (MST CC vs. GG: 4.0 vs. 9.4, p = 0.05; HR = 1.75, p = 0.26). Single allelic carriers for both OGG1 and MUTYH were risk factors towards lung cancer. The risk was amplified on combining both OGG1 and MUTYH.

Genetic associations for keratoconus: a systematic review and meta-analysis

Genetic associations for keratoconus could be useful for understanding disease pathogenesis and discovering biomarkers for early detection of the disease. We conducted a systematic review and meta-analysis to summarize all reported genetic associations for the disease. We searched in the MEDLINE, Embase, Web of Science, and HuGENET databases for genetic studies of keratoconus published from 1950 to June 2016. The summary odds ratio and 95% confidence intervals of all polymorphisms were estimated using the random-effect model. Among 639 reports that were retrieved, 24 fulfilled required criteria as eligible studies for meta-analysis, involving a total of 53 polymorphisms in 28 genes/loci. Results of our meta-analysis lead to the prioritization of 8 single-nucleotide polymorphisms (SNPs) in 6 genes/loci for keratoconus in Whites. Of them 5 genes/loci were originally detected in genome-wide association studies, including FOXO1 (rs2721051, P = 5.6 × 10^-11), RXRA-COL5A1 (rs1536482, P = 2.5 × 10^-9), FNDC3B (rs4894535, P = 1.4 × 10^-8), IMMP2L (rs757219, P = 6.1 × 10^-7; rs214884, P = 2.3 × 10^-5), and BANP-ZNF469 (rs9938149, P = 1.3 × 10^-5). The gene COL4A4 (rs2229813, P = 1.3 × 10^-12; rs2228557, P = 4.5 × 10^-7) was identified in previous candidate gene studies. We also found SNPs in 10 genes/loci that had a summary P value < 0.05. Sensitivity analysis indicated that the results were robust. Replication studies and understanding the roles of these genes in keratoconus are warranted.