ICF, An Immunodeficiency Syndrome: DNA Methyltransferase 3B Involvement, Chromosome Anomalies, and Gene Dysregulation

The immunodeficiency, centromeric region instability, and facial anomalies syndrome (ICF) is the only disease known to result from a mutated DNA methyltransferase gene, namely, DNMT3B. Characteristic of this recessive disease are decreases in serum immunoglobulins despite the presence of B cells and, in the juxtacentromeric heterochromatin of chromosomes 1 and 16, chromatin decondensation, distinctive rearrangements, and satellite DNA hypomethylation. Although DNMT3B is involved in specific associations with histone deacetylases, HP1, other DNMTs, chromatin remodelling proteins, condensin, and other nuclear proteins, it is probably the partial loss of catalytic activity that is responsible for the disease. In microarray experiments and real-time RT-PCR assays, we observed significant differences in RNA levels from ICF vs. control lymphoblasts for pro- and anti-apoptotic genes (BCL2L10, CASP1, and PTPN13); nitrous oxide, carbon monoxide, NF-κB, and TNFa signalling pathway genes (PRKCH, GUCY1A3, GUCY1B3, MAPK13; HMOX1, and MAP4K4); and transcription control genes (NR2F2 and SMARCA2). This gene dysregulation could contribute to the immunodeficiency and other symptoms of ICF and might result from the limited losses of DNA methylation although ICF-related promoter hypomethylation was not observed for six of the above examined genes. We propose that hypomethylation of satellite 2at1qh and 16qh might provoke this dysregulation gene expression by trans effects from altered sequestration of transcription factors, changes in nuclear architecture, or expression of noncoding RNAs

A new case of dup(3q) syndrome due to a pure duplication of 3qter.

Item does not contain fulltextThe characteristic clinical features of the dup(3q) syndrome include typical facial features, mental and growth retardation, and (often) congenital heart anomalies. However, pure duplication of 3qter is rare because most of the reported cases are patients who carry an unbalanced translocation and, in addition to the duplication for 3qter, have a deletion for another chromosomal segment. A new case with a pure duplication of 3q detected in a 2-month-old boy is presented here. Extensive cytogenetic analysis revealed an inverted duplication of the distal part of 3q (chromosomal band 3q26.3 up to the telomere), with no (detectable) loss of the original telomeric sequences. Clinical evaluation revealed several phenotypic hallmarks characteristic for the dup(3q) syndrome. By comparing the duplicated region of this patient with the duplicated regions of the other patients with a pure duplication of 3q, we were able to localize the critical region for the dup(3q) phenotype to band 3q26.3. Alongside this new case with a pure duplication of 3q, an overview of six previous cases is given

Distribution of the D15Z1 copy number polymorphism

Using fluorescent in situ hybridization (FISH) with the probe p15 (D15Z1), we investigated the distribution of the polymorphic 15p signal which has been reported to occur on acrocentric chromosomes in addition to chromosome 15. The short arm of chromosome 15 has a characteristic signal pattern when hybridized with the FISH probe D15Z1. However, the D15Z1 signal can occasionally be seen on the short arm of other acrocentric chromosomes. We studied the distribution of the D15Z1 probe in 1657 patients consisting both of individuals with a normal karyotype and those with a variety of chromosome abnormalities involving the acrocentric chromosomes. Our results show that one in six individuals, regardless of their patient ascertainment category or karyotypic status, had one or more additional D15Z1 signals, and that there were no significant differences in the distribution of extra signals among the patient groups