The gene mutations and subtelomeric DNA methylation in immunodeficiency, centromeric instability and facial anomalies syndrome

A novel mutation in DNMT3B gene causing ICF1 syndrome in an infant with refractory thrombocytopenia

BACKGROUND

ICF syndrome is a rare autosomal recessive condition characterized by immunodeficiency, centromeric instability, and facial abnormalities. It is a clinical condition that depends on the mutation of a few particular genes and is caused by methylation disruption in chromosomes 1, 9, and 16 to varying degrees.

CASE PRESENTATION

The 9-months old, female patient was admitted to our clinic for treatment-resistant thrombocytopenia, chronic diarrhea and sepsis. Immunological investigations revealed agammaglobulinemia. In the genetic analysis by NGS of the patient, who had dysmorphic facial findings as well as a history of parental consanguinity, it was determined that she had a novel mutation in the DNMT3B gene, which is one of the responsible genes of ICF, as homozygous. The patient, who was started on regular immunoglobulin replacement therapy and antibiotic therapy, was referred to a center with a stem cell transplant unit to continue her follow-up.

CONCLUSIONS

Although autoimmunity has not been commonly reported in previous studies in ICF syndrome, which has a varied clinical presentation, a homozygous mutation in the DNMT3B gene was discovered in a 9-month-old patient with refractory thrombocytopenia and agammaglobulinemia. Examining the literature reveals that this mutation is a novel mutation.

DNA Methyltransferases: From Evolution to Clinical Applications

DNA methylation is an epigenetic mark that living beings have used in different environments. The MTases family catalyzes DNA methylation. This process is conserved from archaea to eukaryotes, from fertilization to every stage of development, and from the early stages of cancer to metastasis. The family of DNMTs has been classified into DNMT1, DNMT2, and DNMT3. Each DNMT has been duplicated or deleted, having consequences on DNMT structure and cellular function, resulting in a conserved evolutionary reaction of DNA methylation. DNMTs are conserved in the five kingdoms of life: bacteria, protists, fungi, plants, and animals. The importance of DNMTs in whether methylate or not has a historical adaptation that in mammals has been discovered in complex regulatory mechanisms to develop another padlock to genomic insurance stability. The regulatory mechanisms that control DNMTs expression are involved in a diversity of cell phenotypes and are associated with pathologies transcription deregulation. This work focused on DNA methyltransferases, their biology, functions, and new inhibitory mechanisms reported. We also discuss different approaches to inhibit DNMTs, the use of non-coding RNAs and nucleoside chemical compounds in recent studies, and their importance in biological, clinical, and industry research.