March 2021 - The Association for X and Y Chromosome Variations

Epigenetics and genomics in Klinefelter syndrome

Article Title: Epigenetics and genomics in Klinefelter syndrome

Authors: Skakkebæk, Viuff, Nielsen, and Gravholt

Date of Publication: June 2, 2020

“Since the first description of Klinefelter syndrome (KS) was published in 1942 in The Journal of Clinical Endocrinology, large inter‐individual variability in the phenotypic presentation has been demonstrated. However, our understanding of the global impact of the additional X chromosome on the genome remains an enigma. Evidence from the existing literature of KS indicates that not just one single genetic mechanism can explain the phenotype and the variable expressivity, but several mechanisms may be at play concurrently. In this review, we describe different genetic mechanisms and recent advances in the understanding of the genome, epigenome, and transcriptome of KS and the link to the phenotype and clinical heterogeneity. Future studies are needed to unite clinical data, genomic data, and basic research attempting to understand the genetics behind KS. Unraveling the genetics of KS will be of clinical relevance as it may enable the use of polygenic risk scores to predict future disease susceptibility and enable clinical risk stratification of KS patients in the future.”

Epigenetic and transcriptomic consequences of excess X-chromosome material in 47,XXX syndrome

Article Title: Epigenetic and transcriptomic consequences of excess X-chromosome material in 47,XXX syndrome—A comparison with Turner syndrome and 46,XX females

Authors: Nielsen, Trolle, Vang, Hornshøj, Skakkebaek, Hedegaard, Nordentoft, Pedersen, and Gravholt

Date of Publication: June 3, 2020

“In conclusion, our results suggest an impact of the supernumerary X chromosome in 47,XXX syndrome on the methylation status of selected genes despite an overall comparable expression profile.”

What microRNAs could tell us about the human X chromosome

Article Title: What microRNAs could tell us about the human X chromosome

Authors: Di Palo, Siniscalchi, Salerno, Russo, Gravholt and Potenza

Date of Publication: April 30, 2020

“MicroRNAs (miRNA) are small-non coding RNAs endowed with great regulatory power, thus playing key roles not only in almost all physiological pathways, but also in the pathogenesis of several diseases. Surprisingly, genomic distribution analysis revealed the highest density of miRNA sequences on the X chromosome; this evolutionary conserved mammalian feature equips females with a larger miRNA machinery than males. However, miRNAs contribution to some X-related conditions, properties or functions is still poorly explored. With the aim to support and focus research in the field, this review analyzes the literature and databases about X-linked miRNAs, trying to understand how miRNAs could contribute to emerging gender-biased functions and pathological mechanisms, such as immunity and cancer. A fine map of miRNA sequences on the X chromosome is reported, and their known functions are discussed; in addition, bioinformatics functional analyses of the whole X-linked miRNA targetome (predicted and validated) were performed. The emerging scenario points to different gaps in the knowledge that should be filled with future experimental investigations, also in terms of possible implications and pathological perspectives for X chromosome aneuploidy syndromes, such as Turner and Klinefelter syndromes.”