Placental methylation markers in normal and trisomy 21 tissues

Alterations of epigenetic landscape in Down syndrome carrying pregnancies: A systematic review of case-control studies

OBJECTIVE

Great attention is currently paid to both the pathogenetic mechanisms and non-invasive prenatal diagnosis (NIPD) of Down syndrome (DS). It has been posited that dysregulation of epigenetic signatures including DNA methylation and microRNAs (miRNAs) crucially contribute to the pathomechanism of DS. Therefore, we aimed to perform a systematic review of case-control publications that have examined the differences in epigenetic landscape between pregnancies bearing euploid fetuses and those affected with DS to provide a focused insight into the pathophysiology of DS and also novel biomarkers for NIPD of DS.

STUDY DESIGN

Pertinent keywords were utilized to search into PubMed, Scopus, and Google Scholar. We enrolled studies that have compared the pattern of miRNAs expression profile or DNA methylation between pregnant women who carries DS fetuses and those with euploid fetuses.

RESULTS

An assessment of 599 articles resulted in, finally, 18 eligible studies (12 miRNAs and 6 DNA methylation). The most investigated miRNAs were those that are encoded by genes on chromosome 21 and more hypermethylation regions in DS fetuses than euploids with nearly evenly distribution on all chromosomes were found. Distinct mechanisms with potential therapeutic purposes have been put forward for the involvement of epigenetic perturbations in the etiopathogenesis of DS.

CONCLUSION

There is a disagreement in the recruiting of epigenetic biomarkers for NIPD of DS. This heterogeneity in results of the qualified publications emanates from confounding factors such as differences in demographic data of participants, analytical platforms, and study design. Hence, before harnessing epigenetic signatures for NIPD of DS, more experiments are required.

Down syndrome and Alzheimer's disease: common molecular traits beyond the amyloid precursor protein

Alzheimer’s disease (AD) is the most prevalent type of dementia. Down syndrome (DS) is the leading genetic risk factor for Early-Onset AD, prematurely presenting the classic pathological features of the brain with AD. Augmented gene dosage, including the APP gene, could partially cause this predisposition. Recent works have revealed that alterations in chromosome location due to the extra Chromosome 21, as well as epigenetic modifications, could promote changes in gene expression other than those from Chromosome 21. As a result, similar pathological features and cellular dysfunctions in DS and AD, including impaired autophagy, lysosomal activity, and mitochondrial dysfunction, could be controlled beyond APP overexpression. In this review, we highlight some recent data regarding the origin of the shared features between DS and AD and explore the mechanisms concerning cognitive deficiencies in DS associated with dementia, which could shed some light into the search for new therapeutic targets for AD treatment.

Application of Differentially Methylated Loci in Clinical Diagnosis of Trisomy 21 Syndrome

AIMS

To determine the diagnostic precision of using different sets of fetal-specific methylation markers with methylation-sensitive restriction enzyme-quantitative polymerase chain reaction (MSRE-qPCR) for detection of trisomy 21 (T21).

MATERIALS AND METHODS

The diagnostic value for trisomy 21 of differential methylation of HLCS, C21orf25, and RASSF1A (a fetal-specific internal control) was examined by MSRE-qPCR.

RESULTS

The combined marker set of HLCS and RASSF1A achieved accurate quantification of fetal-specific chromosome 21 and was an excellent marker for detecting the presence of three copies of chromosome 21. MSRE-qPCR correctly identified three cases of fetal T21 from 11 clinical samples, which were 100% consistent with karyotyping results. In addition, this method was able to detect fetal-specific, T21-derived, cell-free fetal DNA at concentrations as low as 0.1%.

CONCLUSIONS

Evaluation of the HLCS and RASSF1A fetal-specific methylation marker set by MSRE-qPCR could be a highly sensitive, specific, cost-effective, and noninvasive prenatal screening method for T21. This MSRE-qPCR testable marker should be considered as an alternative to next generation sequencing technology for diagnosing fetal T21.

Down Syndrome, Ageing and Epigenetics

During the past decades, life expectancy of subjects with Down syndrome (DS) has greatly improved, but age-specific mortality rates are still important and DS subjects are characterized by an acceleration of the ageing process, which affects particularly the immune and central nervous systems. In this chapter, we will first review the characteristics of the ageing phenomenon in brain and in immune system in DS and we will then discuss the biological hallmarks of ageing in this specific population. Finally, we will also consider in detail the knowledge on epigenetics in DS, particularly DNA methylation.