A new case of de novo 6q24.2-q25.2 deletion on paternal chromosome 6 with growth hormone deficiency: A twelve-year follow-up and literature review

BACKGROUND: Deletions on the distal portion of the long arm of chromosome 6 are relatively uncommon, and only a small number occurs in the paternal copy, causing growth abnormalities. As a result, extensive clinical descriptions are lacking. CASE PRESENTATION: We describe a male of Italian descent born at 35 weeks by elective caesarean delivery presenting hypoplastic left colon, bilateral inguinal hernia, dysplastic tricuspid and pulmonary valves, premature ventricular contractions, recurrent otitis media, poor feeding, gastro-oesophageal reflux, bilateral pseudopapilledema, and astigmatism. He also showed particular facial dysmorphisms and postnatal growth failure. Early psychomotor development was mildly delayed. At 3.75 years, he was evaluated for severe short stature (−2.98 SD) and delayed bone age. He showed an insulin-like growth factor 1 concentration (IGF-1) in the low-normal range. Growth hormone stimulation tests showed a low response to clonidine and insulin. Magnetic resonance imaging showed hypophyseal hypoplasia. Genetic evaluation by Single Nucleotide Polymorphism arrays showed a de novo 6q24.2-q25.2 deletion on paternal chromosome 6. CONCLUSION: We confirm that this is a new congenital malformation syndrome associated with a deletion of 6q24.2-q25.2 on paternal chromosome 6. We suggest evaluating the growth hormone axis in children with 6q24.2-q25.2 deletions and growth failure

The KCNQ1OT1 imprinting control region and non-coding RNA: new properties derived from the study of Beckwith–Wiedemann syndrome and Silver–Russell syndrome cases

A cluster of imprinted genes at chromosome 11p15.5 is associated with the growth disorders, Silver–Russell syndrome (SRS) and Beckwith–Wiedemann syndrome (BWS). The cluster is divided into two domains with independent imprinting control regions (ICRs). We describe two maternal 11p15.5 microduplications with contrasting phenotypes. The first is an inverted and in cis duplication of the entire 11p15.5 cluster associated with the maintenance of genomic imprinting and with the SRS phenotype. The second is a 160 kb duplication also inverted and in cis, but resulting in the imprinting alteration of the centromeric domain. It includes the centromeric ICR (ICR2) and the most 5′ 20 kb of the non-coding KCNQ1OT1 gene. Its maternal transmission is associated with ICR2 hypomethylation and the BWS phenotype. By excluding epigenetic mosaicism, cell clones analysis indicated that the two closely located ICR2 sequences resulting from the 160 kb duplication carried discordant DNA methylation on the maternal chromosome and supported the hypothesis that the ICR2 sequence is not sufficient for establishing imprinted methylation and some other property, possibly orientation-dependent, is needed. Furthermore, the 1.2 Mb duplication demonstrated that all features are present for correct imprinting at ICR2 when this is duplicated and inverted within the entire cluster. In the individuals maternally inheriting the 160 kb duplication, ICR2 hypomethylation led to the expression of a truncated KCNQ1OT1 transcript and to down-regulation of CDKN1C. We demonstrated by chromatin RNA immunopurification that the KCNQ1OT1 RNA interacts with chromatin through its most 5′ 20 kb sequence, providing a mechanism likely mediating the silencing activity of this long non-coding RNA

Distinct Methylation Changes at the IGF2-H19 Locus in Congenital Growth Disorders and Cancer

Background: Differentially methylated regions (DMRs) are associated with many imprinted genes. In mice methylation at a DMR upstream of the H19 gene known as the Imprint Control region (IC1) is acquired in the male germline and influences the methylation status of DMRs 100 kb away in the adjacent Insulin-like growth factor 2 (Igf2) gene through long-range interactions. In humans, germline-derived or post-zygotically acquired imprinting defects at IC1 are associated with aberrant activation or repression of IGF2, resulting in the congenital growth disorders Beckwith-Wiedemann (BWS) and Silver-Russell (SRS) syndromes, respectively. In Wilms tumour and colorectal cancer, biallelic expression of IGF2 has been observed in association with loss of methylation at a DMR in IGF2. This DMR, known as DMR0, has been shown to be methylated on the silent maternal IGF2 allele presumably with a role in repression. The effect of IGF2 DMR0 methylation changes in the aetiology of BWS or SRS is unknown. Methodology/Principal Findings: We analysed the methylation status of the DMR0 in BWS, SRS and Wilms tumour patients by conventional bisulphite sequencing and pyrosequencing. We show here that, contrary to previous reports, the IGF2 DMR0 is actually methylated on the active paternal allele in peripheral blood and kidney. This is similar to the IC

Silver-Russell syndrome following in vitro fertilization

[No abstract available

Silver-Russell syndrome due to paternal H19/IGF2 hypomethylation in a twin girl born after in vitro fertilization

Silver-Russell syndrome (SRS) is a clinically and genetically heterogeneous syndrome characterized by severe intrauterine and postnatal growth retardation, facial dysmorphism and body asymmetry. One of the main molecular mechanisms leading to the syndrome involves methylation abnormalities of chromosome 11p15. In the last decades, an increase of imprinting disorders have been reported in children born from assisted reproductive technology (ART); however there is currently little evidence linking SRS and ART. Only few infants with SRS born using ART, supported by molecular analysis, have been described. We report on a twin-girl conceived using intracytoplasmic sperm injection (ICSI) diagnosed with SRS. Molecular studies revealed a hypomethylation of the paternal H19/IGF2 Imprinting Control Region. Her twin sister had a normal prenatal and postnatal growth and a normal methylation pattern of the chromosome 11p15. This is the second reported case of a twin infant with SRS conceived using ART with hypomethylation of H19/IGF2; it provides additional evidence of a possible relationship between ART procedures and methylation defects observed in SRS. Given the clinical heterogeneity of SRS, and the increased risk of multiple and preterm births in the ART-conceived children, it is possible that a number of cases of SRS remains undiagnosed in this population. Future studies should investigate the possible link between ART and SRS, in order to better understand the causes of epimutations in ART pregnancies, and to help clinicians to adequately counsel parents who approach to ART and to assess the opportunity of a long-term follow-up of children conceived using ART

A splicing mutation of the HMGA2 gene is associated with Silver-Russell syndrome phenotype

Silver-Russell syndrome (SRS) is a heterogeneous disorder characterized by intrauterine and post-natal growth retardation, dysmorphic facial features and body asymmetry. About 50% of the patients carry (epi)genetic alterations involving chromosomes 7 or 11.The high proportion of patients with unidentified molecular etiology suggests the involvement of other genes. Interestingly, SRS patients share clinical features with the 12q14 microdeletion syndrome, characterized by several deletions with a 2.6 Mb region of overlap. Among the genes present in this interval, high mobility AT-hook 2 (HMGA2) appears to be the most likely cause of the growth deficiency, due to its described growth control function. To define the role of HMGA2 in SRS, we looked for 12q14 chromosome imbalances and HMGA2 mutations in a cohort of 45 patients with growth retardation and SRS-like phenotype but no 11p15 (epi)mutations or maternal uniparental disomy of chromosome 7 (matUPD7). We identified a novel 7 bp intronic deletion in HMGA2 present in heterozygosity in the proband and her mother both displaying the typical features of SRS. We demonstrated that the deletion affected normal splicing, indicating that it is a likely cause of HMGA2 deficiency. This study provides the first evidence that a loss-of-function mutation of HMGA2 can be associated with a familial form of SRS. We suggest that HMGA2 mutations leading to haploinsufficiency should be investigated in the SRS patients negative for the typical 11p15 (epi)mutations and matUPD7

A novel microdeletion in the IGF2/H19 imprinting centre region defines a recurrent mutation mechanism in familial Beckwith–Wiedemann syndrome

The overgrowth disorder Beckwith–Wiedemann syndrome (BWS) is associated with dysregulation of imprinted genes at chromosome 11p15.5. The molecular defects are heterogeneous but most of the cases are associated with defective DNA methylation at either one of two Imprinting Control Regions (IC1 and IC2) or Uniparental paternal Disomy (UPD) at 11p15.5. In rare cases, the BWS phenotype has been found associated with maternal transmission of IC1 microdeletions. We describe a family with a novel 1.8 kb deletion that is associated with hypermethylation at IC1. The mutation results from recombination between highly homologous sequences containing target sites for the zinc-finger protein CTCF (CTSs). This finding supports the hypothesis that the function of IC1 and the penetrance of the clinical phenotype depend on the spacing of the CTSs resulting from recombination in the mutant allele