Overview of non-coding mutations in chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is the most frequent leukemia type in which the genetic alterations influencing the clinico-biological course are not entirely understood. CLL has a heterogeneous course, with some patients showing an indolent course and others experiencing an aggressive course. Whole-genome sequencing and whole-exome sequencing studies identified recurrently mutated genes in CLL and profiled its clonal evolution patterns. However, more recent whole-genome sequencing studies also identified variants in non-coding sequences of the CLL genome, revealing important lesions outside the protein-coding regions. Here we describe the most representative non-coding lesion of the CLL genome, including lesions in the 3'-UTR region of NOTCH1 which result in the truncation of the NOTCH1 protein PEST domain, and non-coding mutations in an enhancer region on chromosome 9p13 which result in reduced expression of the PAX5 transcription factor. In addition, we describe the role of microRNA in CLL, in particular the miR15a/miR16-1 microRNA recurrently affected by deletions of chromosome 13q14. Together, new findings in non-coding genome genetic lesions provide a more complete portrait of the genomic landscape of CLL with clinical implications.