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Despite the inclusion of inherited myeloid malignancies as a separate entity in the World Health Organization Classification, many established predisposing loci continue to lack functional characterization. While germline mutations in the DNA repair factor ERCC excision repair 6 like 2 (ERCC6L2) give rise to bone marrow failure and acute myeloid leukaemia, their consequences on normal haematopoiesis remain unclear. To functionally characterise the dual impact of germline ERCC6L2 loss on human primary haematopoietic stem/progenitor cells (HSPCs) and mesenchymal stromal cells (MSCs), we challenged ERCC6L2-silenced and patient-derived cells ex vivo. Here, we show for the first time that ERCC6L2-deficiency in HSPCs significantly impedes their clonogenic potential and leads to delayed erythroid differentiation. This observation was confirmed by CIBERSORTx RNA-sequencing deconvolution performed on ERCC6L2-silenced erythroid-committed cells, which demonstrated higher proportions of polychromatic erythroblasts and reduced orthochromatic erythroblasts versus controls. In parallel, we demonstrate that the consequences of ERCC6L2-deficiency are not limited to HSPCs, as we observe a striking phenotype in patient-derived and ERCC6L2-silenced MSCs, which exhibit enhanced osteogenesis and suppressed adipogenesis. Altogether, our study introduces a valuable surrogate model to study the impact of inherited myeloid mutations and highlights the importance of accounting for the influence of germline mutations in HSPCs and their microenvironment.

Background Little is known about the aetiology of chronic lymphocytic leukaemia (CLL). The family medical history is a "genomic tool" capturing interactions of genetic susceptibility, shared environment and common behaviours. Methods A cohort of 66 consecutives patients with CLL (probands) was studied in a medical oncology practice (W.W.) from 1981 until 2005. A German version of the NCI medical history questionnaire for cancer aetiology was used. Familial clustering analysis was done by comparing the proportion of specific tumours in the first degree relatives of the CLL practice cohort with corresponding proportions of population-based cancer registry data. Results 18 (41%) male and 5 (23%) female CLL probands had multiple malignancies, e.g. 2 meningiomas, 7 and 19 years after diagnosis of CLL. 46 (12%) first degree relatives had malignancies with an excess of CLL. Other conspicuous familial associations are CLL with malignancies of the upper GI tract (oesophagus, stomach) and of the nervous system. Conclusion 1. Chronic lymphocytic leukaemia clusters in some families like any other disease. Predisposition genes should be searched. 2. Cancer prevention and early detection should be continued in CLL patients because of their longevity and high risk for multiple malignancies. 3. The overrepresentation of upper GI malignancies in first degree relatives of CLL patients calls for targeted oesophago-gastroscopy screening studies.