DOT1L-mediated H3K79me2 modification critically regulates gene expression during cardiomyocyte differentiation

Epigenetic changes on DNA and chromatin are implicated in cell differentiation and organogenesis. For the heart, distinct histone methylation profiles were recently linked to stage-specific gene expression programs during cardiac differentiation in vitro. However, the enzymes catalyzing these modifications and the genes regulated by them remain poorly defined. We therefore decided to identify the epigenetic enzymes that are potentially involved in cardiomyogenesis by analyzing the expression profile of the 85 genes encoding the epigenetic-related proteins in mouse cardiomyocytes (CMs), and then study how they affect gene expression during differentiation and maturation of this cell type. We show here with gene expression screening of epigenetic enzymes that the highly expressed H3 methyltransferase disruptor of telomeric silencing 1-like (DOT1L) drives a transitional pattern of di-methylation on H3 lysine 79 (H3K79) in CMs at different stages of differentiation in vitro and in vivo. Through a genome-wide chromatin-immunoprecipitation DNA-sequencing approach, we found H3K79me2 enriched at genes expressed during cardiac differentiation. Moreover, knockdown of Dot1L affected the expression of H3K79me2-enriched genes. Our results demonstrate that histone methylation, and in particular DOT1L-mediated H3K79me2 modification, drives cardiomyogenesis through the definition of a specific transcriptional landscape.

Anaplastic thyroid cancer: a case report of a long term survival patient and review of literature data

Anaplastic thyroid carcinoma (ATC) is a very rare disease accounting for less than 2% of all thyroid malignancies and associated to a dismal prognosis. The median survival is between 3 to 9 months with less than 10% of patients alive at 3 years after the time of diagnosis. This low cure rate is due to the late clinical presentation as a bulky unresectable tumour mass often associated with synchronous lung metastases (20-50%). A multimodality treatment consisting in a radical surgery followed by radiotherapy and chemotherapy is reported to be associated with better clinical outcomes while young age (< 65 years), tumour size (< 6.5 cm) and absence of distant metastases at time of diagnosis are recognized as strong prognostic factors of survival. We report the case of a 65 year-old man who was referred to our hospital for an ATC which extended to the external right tracheal wall and muscolar layer of esophagus. The patient underwent radical thyroidectomy with bilateral neck dissection followed by 3 cycles of adjuvant chemotherapy (Cisplatin /Epirubicin) and subsequent radiochemotherapy with Cisplatin as radiosensitizer. At more than 6 years since diagnosis the patient is still alive without evidence of local recurrence or distant metastases. Therefore, aggressive multimodality treatment after radical surgery might improve clinical outcomes and perhaps should be tested in prospective clinical trials.

Genome-wide signatures of population bottlenecks and diversifying selection in European wolves

Genomic resources developed for domesticated species provide powerful tools for studying the evolutionary history of their wild relatives. Here we use 61K single-nucleotide polymorphisms (SNPs) evenly spaced throughout the canine nuclear genome to analyse evolutionary relationships among the three largest European populations of grey wolves in comparison with other populations worldwide, and investigate genome-wide effects of demographic bottlenecks and signatures of selection. European wolves have a discontinuous range, with large and connected populations in Eastern Europe and relatively smaller, isolated populations in Italy and the Iberian Peninsula. Our results suggest a continuous decline in wolf numbers in Europe since the Late Pleistocene, and long-term isolation and bottlenecks in the Italian and Iberian populations following their divergence from the Eastern European population. The Italian and Iberian populations have low genetic variability and high linkage disequilibrium, but relatively few autozygous segments across the genome. This last characteristic clearly distinguishes them from populations that underwent recent drastic demographic declines or founder events, and implies long-term bottlenecks in these two populations. Although genetic drift due to spatial isolation and bottlenecks seems to be a major evolutionary force diversifying the European populations, we detected 35 loci that are putatively under diversifying selection. Two of these loci flank the canine platelet-derived growth factor gene, which affects bone growth and may influence differences in body size between wolf populations. This study demonstrates the power of population genomics for identifying genetic signals of demographic bottlenecks and detecting signatures of directional selection in bottlenecked populations, despite their low background variability.