Key Points• Acquired pathogenic mutations in SAMHD1 are found in up to 11% of relapsed/refractory patients with CLL. • SAMHD1 is mobilized to sites of DNA damage.SAMHD1 is a deoxynucleoside triphosphate triphosphohydrolase and a nuclease that restricts HIV-1 in noncycling cells. Germ-line mutations in SAMHD1 have been described in patients with Aicardi-Goutières syndrome (AGS), a congenital autoimmune disease. In a previous longitudinal whole genome sequencing study of chronic lymphocytic leukemia (CLL), we revealed a SAMHD1 mutation as a potential founding event. Here, we describe an AGS patient carrying a pathogenic germ-line SAMHD1 mutation who developed CLL at 24 years of age. Using clinical trial samples, we show that acquired SAMHD1 mutations are associated with high variant allele frequency and reduced SAMHD1 expression and occur in 11% of relapsed/refractory CLL patients. We provide evidence that SAMHD1 regulates cell proliferation and survival and engages in specific protein interactions in response to DNA damage. We propose that SAMHD1 may have a function in DNA repair and that the presence of SAMHD1 mutations in CLL promotes leukemia development. (Blood. 2014;123(7):1021-1031)

Science videos on YouTube attract millions of viewers each month, but little is known about who the content producers are, how they work and what their motivations and qualifications are. Here, we analyze the characteristics of 622 French YouTube science channels and 70,795 science videos in French, and complement this analysis with a survey of 180 of these youtubers. We focus on three questions: who are the science communicators (sociodemographics, resources, and goals), what are the characteristics of their channels, and are there differences between institutional and non-institutional communicators. We show that French science communicators on YouTube are mostly young men, highly qualified and usually talking about their topic of expertize. Many of them do not earn enough money to make a living out of this activity and have to use personal money to run their channels. At the same time, many are not interested in making this activity their main source of income. Their main goal is to share science and stimulate curiosity, as opposed to teach and entertain. While a small number of channels account for most of the views and subscribers, together they are able to cover a lot of scientific disciplines, with individuals usually focusing on a couple of fields and institutions talking about more diverse subjects. Institutions seem to have less success on YouTube than individuals, a result visible both in the number of subscribers and engagement received in videos (likes and comments). We discuss the potential factors behind this discrepancy, such as the lack of personality of institutional channels, the high number of topics they cover or the fact that institutions usually have an additional goal compared to individuals: to present and promote the institution itself.

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