DNMT3B and immunodeficiency disease: The preferential role of DNMT3B at CGIs is compatible with data showing that mice or human ICF syndrome (immunodeficiency, centromeric instability, facial anomalies) patients with DNMT3B mutations have reduced methylation at CGIs on autosomes and the inactive X chromosome [43,50,51], suggesting a functional conservation of DNMT3B function between mice and humans.