Identification of a novel epigenetic marker for typical and mosaic presentations of Fragile X syndrome.

BACKGROUND: Fragile X syndrome (FXS) is primarily due to CGG repeat expansions in the FMR1 gene. FMR1 alleles are classified as normal (N), intermediate (I), premutation (PM), and full mutation (FM). FXS patients often carry an FM, but size mosaicism can occur. Additionally, loss of methylation boundary upstream of repeats results in de novo methylation spreading to FMR1 promoter in FXS patients. RESEARCH DESIGN AND METHODS: This pilot study investigated the methylation boundary and adjacent regions in 66 males with typical and atypical FXS aged 1 to 30 years (10.86 ± 6.48 years). AmplideX FMR1 mPCR kit was used to discriminate allele profiles and methylation levels. CpG sites were assessed by pyrosequencing. RESULTS: 40 out of 66 FXS patients (60.6%) showed an exclusive FM (n = 40), whereas the remaining (n = 26) exhibited size mosaicism [10 PM_FM (15.15%); 10 N_FM (15.15%); 2 N_PM_FM (3%)]. Four patients (6.1%) had deletions near repeats. Noteworthy, a CpG within FMR1 intron 2 displayed hypomethylation in FXS patients and hypermethylation in controls, demonstrating remarkable specificity, sensitivity, and accuracy when a methylation threshold of 69.5% was applied. CONCLUSIONS: Since intragenic methylation is pivotal in gene regulation, the intronic CpG might be a novel epigenetic biomarker for FXS diagnosis.

The implications of DNA methylation for amyotrophic lateral sclerosis.

Amyotrophic lateral sclerosis (ALS) is a complex and serious neurodegenerative disorder that develops in consequence of the progressive loss of the upper and lower motor neurons. Cases of ALS are classified as sporadic (sALS), or familial (fALS). Over 90% of cases are sALS, while roughly 10% are related to inherited genetic mutations (fALS). Approximately 70% of the genetic mutations that contribute to fALS have been identified. On the other hand, the majority of the sALS cases have an undetermined genetic contributor and few mutations have been described, despite the advanced genetic analysis methods. Also, several factors contribute to the onset and progression of ALS. Numerous lines of evidence indicate that epigenetic changes are linked to aging, as well as neurodegenerative disorders, such as ALS. In most cases, they act as the heritable regulation of transcription by DNA methylation, histone modification and expression of noncoding RNAs. Mechanisms involving aberrant DNA methylation could be relevant to human ALS pathobiology and therapeutic targeting. Despite advances in research to find factors associated with ALS and more effective treatments, this disease remains complex and has low patient survival. Here, we provide a narrative review of the role of DNA methylation for this complex neurodegenerative disorder.

Polymorphisms of CDKN1A gene and risk of retinoblastoma.

UNLABELLED: Retinoblastoma (RB) is a malignant neoplasia that occurs mostly in children under 5 years. Recently, CDKN1A gene has been shown to be up-regulated in a context of loss of function of pRb. This gene encodes the p21 protein, which is the bona fide effector of p53. We hypothesized whether two putatively functional single nucleotide polymorphisms (SNPs) of CDKN1A (rs1801270 C>A and rs1059234 C>T) may influence the risk and/or survival of RB patients. We genotyped both SNPs in 141 RB patients and 120 unrelated healthy individuals. Statistical analyses consisted of chi-square (χ(2)), odds ratio (OR) and survival curves by Kaplan-Meier method. We found that patients who carry the genotype CA for rs1801270 and CT for rs1059234 were associated to an increased risk of RB [OR = 2.5, 95% confidence interval (CI) = 1.38-4.53], whereas patients with CC for both polymorphisms were associated to a lower risk of developing RB (OR = 0.43, 95% CI = 0.25-0.74). On the other hand, Kaplan-Meier curves did not show statistically significant differences in survival among the studied polymorphisms. We conclude that the minor alleles of rs1801270 and rs1059234 polymorphisms may act as risk factors for the development of RB in our sample. SUMMARY: The minor alleles of polymorphisms rs1801270 C>A and rs1059234 C>T in CDKN1A (p21) gene may act as risk factors for the development of RB; however, they do not seem to influence overall survival.

Allele distribution of six STR/miniSTR loci (CD4, FABP2, D12S391, D14S1434, D22S1045 and D10S1248) for forensic purposes in Southeastern Brazil.

BACKGROUND: Allele frequencies for six STR/miniSTR loci were determined in a sample of unrelated individuals from Southeastern Brazil. METHODS AND RESULTS: No significant deviations from Hardy-Weinberg equilibrium proportions were observed for the loci investigated (p-values ≥ 0.2320). Statistical parameters of forensic interest such as heterozygosity (H), power of discrimination (PD) and power of exclusion (PE) were estimated. Except for marker FABP2, all STR/miniSTRs tested showed observed heterozygosities over 0.66.Combined power of discrimination and power of exclusion were 0.9999993 and 0.9925, respectively. CONCLUSIONS: Due to their ease of analysis and high informativity, these new STR multiplexes will be useful for extending current marker sets for forensic and paternity purposes.