For example, DNMT3l, the regulator of DNMT3a and DNMT3b, was identified to have lost DNA methylation level in cervival cancer patients [25]; DNA mutations in DNMT3b are of importance in cancer progression [26], [27] and ICF syndrome (immunodeficiency, centromere instability and facial anomalies, an autosomal recessive disease) in humans [28]. Here, DNMT3B is linked to immunodeficiency disease.