The active state of centromeres is epigenetically defined by the presence of CENP-A interspersed with histone H3 nucleosomes. While the importance of dimethylation of H3K4 for centromeric transcription has been highlighted in various studies, the identity of the enzyme(s) depositing these marks on the centromere is still unknown. The MLL (KMT2) family plays a crucial role in RNA polymerase II (Pol II)-mediated gene regulation by methylating H3K4. Here, we report that MLL methyltransferases regulate transcription of human centromeres. CRISPR-mediated down-regulation of MLL causes loss of H3K4me2, resulting in an altered epigenetic chromatin state of the centromeres. Intriguingly, our results reveal that loss of MLL, but not SETD1A, increases co-transcriptional R-loop formation, and Pol II accumulation at the centromeres. Finally, we report that the presence of MLL and SETD1A is crucial for kinetochore maintenance. Altogether, our data reveal a novel molecular framework where both the H3K4 methylation mark and the methyltransferases regulate stability and identity of the centromere.

<b><i>Introduction:</i></b> The accurate detection of breakpoint regions of disease-associated chromosomal rearrangements helps understand the molecular mechanisms and identify the risks involved with disrupted genes. <b><i>Methods:</i></b> In this study, a girl with growth retardation is characterized using positional cloning and genome sequencing. The techniques include fluorescence in situ hybridization (FISH) with paint (WCP) and bacterial-artificial chromosomes (BAC) probes, PCR, real-time PCR, and short and long-read sequencing. <b><i>Results:</i></b> The translocation was identified by GTG banding and confirmed by WCP FISH. Microarray ruled out the involvement of other copy number variations except for 6 homozygous regions which are not disease-causing variants. Fine mapping with FISH showed split signals with BAC clone RP11-312A3. Genome sequencing of short-read with an average 30× depth and long-read sequencing technology with a 3.8× coverage identified both breakpoints, confirmed by Sanger sequencing, that showed microhomology. The breakpoint at 1p and 12p regions disrupted <i>EYA3</i> and <i>EFCAB4B</i> genes. Expression analysis of <i>EYA3</i> showed a 7-fold increase, suggesting the formation of a fusion gene with <i>EFCAB4B</i>. <i>EYA3</i> is involved in skeleton development, and <i>EFCAB4B</i> plays a role in calcium metabolism, which may be relevant for the patient’s phenotype. <b><i>Conclusion:</i></b> The systematic application of genome techniques to translocations and their advantages is discussed.