[Turner syndrome and genetic polymorphism: a systematic review]

Maternal MTHFR 677C>T, 1298A>C gene polymorphisms and risk of offspring aneuploidy

OBJECTIVE

The objective was to investigate the association between maternal methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms, crucial for DNA methylation, and risk of offspring aneuploidy.

METHODS

MTHFR gene polymorphisms 677C>T and 1298A>C were determined by polymerase chain reaction based method, in 163 women with offspring aneuploidy and 155 women with healthy children. Five genetic models were used to assess risk, according to the type of aneuploidy and the age of women at conception.

RESULTS

MTHFR 677TT genotype and T allele were significantly more prevalent among women with offspring aneuploidy, with an increased risk of aneuploidy demonstrated under a recessive (OR 3.499), homozygote (OR 3.456) and allele contrast model (OR 1.574). The more prominent association was found with sex chromosome aneuploidies and trisomy 13/18, and also in women ≤35 years at conception. No association was observed between 1298A>C polymorphism and risk of offspring aneuploidy, although synergistic effect of two polymorphisms increase the risk of aneuploidy, primarily amplifying the 677T allele effects (p<0.001).

CONCLUSION

Maternal MTHFR 677C>T gene polymorphism, alone or in combination with another 1298A>C polymorphism, appears to be a substantial risk factor for offspring aneuploidy in Montenegro population, especially for sex chromosome aneuploidies and trisomy 13/18, and among younger women. This article is protected by copyright. All rights reserved.

Low bone mineral density and renal malformation in Mexican patients with Turner syndrome are associated with single nucleotide variants in vitamin D-metabolism genes

Turner syndrome (TS) is a common genetic disorder. TS-phenotype includes short stature, gonadal dysgenesis, cardiac and kidney malformations, low bone mineral density (low-BMD) and thyroiditis. TS-phenotype varies from patient to patient and the cause is not clear, the genomic background may be an important contributor for this variability. Our aim was to identify the association of specific single nucleotide variants in the PTPN22, VDR, KL, and CYP27B1 genes and vitamin D-metabolism, heart malformation, renal malformation, thyroiditis, and low-BMD in 61 Mexican TS-patients. DNA samples were genotyped for SNVs: rs7975232 (VDR), rs9536282 (KL), rs4646536 (CYP27B1), and rs1599971 (PTPN22) using the KASP assay. Chi-square test under a recessive model and multifactorial dimensionality reduction method were used for analysis. We found a significant association between renal malformation and the rs9536282 (KL) variant and between rs4646536 (CYP27B1) and low-BMD, these variants may have modest effects on these characteristics but contribute to the variability of the TS phenotype. In addition, we identified gene-gene interactions between variants in genes KL, CYP27B1 and VDR related to vitamin D-metabolism and low-BMD in TS-patients. Our results support the idea that the genetic background of TS-patients contributes to the clinical variability seen in them.

Prevalence of autoimmune thyroid diseases among the Turner Syndrome patients: meta-analysis of cross sectional studies

Objective

This meta-analysis was done to estimate the prevalence of autoimmune thyroid diseases (ATDs) in Turner Syndrome patients, and to determine the clinical status of thyroid autoimmune diseases that occur frequently in association with Turner Syndrome.

Results

A total of 18 studies were included in the meta-analysis. The pooled overall prevalence of autoimmune thyroid diseases in Turner Syndrome patients was 38.6% (95% CI 29.7–47.6%), with 12.7% (95% CI 9.30–16.1%) of them had clinical hypothyroidism and 2.6% (95% CI 1.5–3.8%) had hyperthyroidism. I-squared test had a high result of heterogeneity. In subgroup analyses, the prevalence of ATDs was higher in the European region than Asian region. Autoimmune thyroid diseases are commonly associated with Turner Syndrome. Early detection of thyroid diseases by optimal screening among children with Turner Syndrome is required to ensure effective management.

Electronic supplementary material

The online version of this article (10.1186/s13104-018-3950-0) contains supplementary material, which is available to authorized users.

Assessment of the key regulatory genes and their Interologs for Turner Syndrome employing network approach

Turner Syndrome (TS) is a condition where several genes are affected but the molecular mechanism remains unknown. Identifying the genes that regulate the TS network is one of the main challenges in understanding its aetiology. Here, we studied the regulatory network from manually curated genes reported in the literature and identified essential proteins involved in TS. The power-law distribution analysis showed that TS network carries scale-free hierarchical fractal attributes. This organization of the network maintained the self-ruled constitution of nodes at various levels without having centrality-lethality control systems. Out of twenty-seven genes culminating into leading hubs in the network, we identified two key regulators (KRs) i.e. KDM6A and BDNF. These KRs serve as the backbone for all the network activities. Removal of KRs does not cause its breakdown, rather a change in the topological properties was observed. Since essential proteins are evolutionarily conserved, the orthologs of selected interacting proteins in C. elegans, cat and macaque monkey (lower to higher level organisms) were identified. We deciphered three important interologs i.e. KDM6A-WDR5, KDM6A-ASH2L and WDR5-ASH2L that form a triangular motif. In conclusion, these KRs and identified interologs are expected to regulate the TS network signifying their biological importance.

Sex chromosomes drive gene expression and regulatory dimorphisms in mouse embryonic stem cells

BACKGROUND

Pre-implantation embryos exhibit sexual dimorphisms in both primates and rodents. To determine whether these differences reflected sex-biased expression patterns, we generated transcriptome profiles for six 40,XX, six 40,XY, and two 39,X mouse embryonic stem (ES) cells by RNA sequencing.

RESULTS

We found hundreds of coding and non-coding RNAs that were differentially expressed between male and female cells. Surprisingly, the majority of these were autosomal and included RNA encoding transcription and epigenetic and chromatin remodeling factors. We showed differential Prdm14-responsive enhancer activity in male and female cells, correlating with the sex-specific levels of Prdm14 expression. This is the first time sex-specific enhancer activity in ES cells has been reported. Evaluation of X-linked gene expression patterns between our XX and XY lines revealed four distinct categories: (1) genes showing 2-fold greater expression in the female cells; (2) a set of genes with expression levels well above 2-fold in female cells; (3) genes with equivalent RNA levels in male and female cells; and strikingly, (4) a small number of genes with higher expression in the XY lines. Further evaluation of autosomal gene expression revealed differential expression of imprinted loci, despite appropriate parent-of-origin patterns. The 39,X lines aligned closely with the XY cells and provided insights into potential regulation of genes associated with Turner syndrome in humans. Moreover, inclusion of the 39,X lines permitted three-way comparisons, delineating X and Y chromosome-dependent patterns.

CONCLUSIONS

Overall, our results support the role of the sex chromosomes in establishing sex-specific networks early in embryonic development and provide insights into effects of sex chromosome aneuploidies originating at those stages.

Analysis of PTPN22, ZFAT and MYO9B polymorphisms in Turner Syndrome and risk of autoimmune disease

Turner syndrome (TS) is one of the most common sexual chromosome abnormalities and is clearly associated with an increased risk of autoimmune diseases, particularly thyroid disease and coeliac disease (CD). Single-nucleotide polymorphism analyses have been shown to provide correlative evidence that specific genes are associated with autoimmune disease. Our aim was to study the functional polymorphic variants of PTPN22 and ZFAT in relation to thyroid disease and those of MYO9B in relation to CD. A cross-sectional comparative analysis was performed on Mexican mestizo patients with TS and age-matched healthy females. Our data showed that PTPN22 C1858T (considered a risk variant) is not associated with TS (X²  = 3.50, p = .61, and OR = 0.33 [95% CI = 0.10-1.10]). Also, ZFAT was not associated with TS (X²  = 1.2, p = .28, and OR = 1.22 [95% CI = 0.84-1.79]). However, for the first time, rs2305767 MYO9B was revealed to have a strong association with TS (X²  = 58.6, p = .0001, and OR = 10.44 [95% C = 5.51-19.80]), supporting a high level of predisposition to CD among TS patients. This report addresses additional data regarding the polymorphic variants associated with autoimmune disease, one of the most common complications in TS.