Excess functional copy of allele at chromosomal region 11p15 may cause Wiedemann-Beckwith (EMG) syndrome

The effectiveness of Wilms tumor screening in Beckwith-Wiedemann spectrum

PURPOSE

It is well documented that patients with Beckwith-Wiedemann spectrum (BWS) have a significantly higher risk of developing Wilms tumor (WT) than the general population. There has been little research on the timing of WT diagnosis in BWS in regard to optimizing suggested screening protocols.

METHODS

A literature search was performed to identify all reports of patients with BWS and WT. These data were combined with unpublished data from patients in the authors' cohorts. Age at WT diagnosis was compared against data collected through the NIH Surveillance, Epidemiology, and End Results Program (SEER) registry.

RESULTS

Patients with BWS had a significantly higher incidence of WT diagnoses between age 12 and 84 months compared to patients in the SEER registry. Patients with BWS and WT diagnosed through screening had significantly lower stages at diagnosis compared to patients with BWS that were not screened.

CONCLUSIONS

Screening until age 7 years is effective in detecting close to 95% of all WT in patients with BWS.

Prader-Willi Syndrome: The Disease that Opened up Epigenomic-Based Preemptive Medicine

Prader-Willi syndrome (PWS) is a congenital neurodevelopmental disorder caused by loss of function of paternally expressed genes on chromosome 15 due to paternal deletion of 15q11–q13, maternal uniparental disomy for chromosome 15, or an imprinting mutation. We previously developed a DNA methylation-based PCR assay to identify each of these three genetic causes of PWS. The assay enables straightforward and rapid diagnosis during infancy and therefore allows early intervention such as nutritional management, physical therapy, or growth hormone treatment to prevent PWS patients from complications such as obesity and type 2 diabetes. It is known that various environmental factors induce epigenomic changes during the perinatal period, which increase the risk of adult diseases such as type 2 diabetes and intellectual disabilities. Therefore, a similar preemptive approach as used in PWS would also be applicable to acquired disorders and would make use of environmentally-introduced “epigenomic signatures” to aid development of early intervention strategies that take advantage of “epigenomic reversibility”.

Understanding the epigenetics of neurodevelopmental disorders and DOHaD

The Developmental Origins of Health and Disease (DOHaD) hypothesis refers to the concept that 'malnutrition during the fetal period induces a nature of thrift in fetuses, such that they have a higher change of developing non-communicable diseases, such as obesity and diabetes, if they grow up in the current well-fed society.' Epigenetics is a chemical change in DNA and histones that affects how genes are expressed without alterations of DNA sequences. Several lines of evidence suggest that malnutrition during the fetal period alters the epigenetic expression status of metabolic genes in the fetus and that this altered expression can persist, and possibly lead to metabolic disorders. Similarly, mental stress during the neonatal period can alter the epigenetic expression status of neuronal genes in neonates. Moreover, such environmental, stress-induced, epigenetic changes are transmitted to the next generation via an acquired epigenetic status in sperm. The advantage of epigenetic modifications over changes in genetic sequences is their potential reversibility; thus, epigenetic alterations are potentially reversed with gene expression. Therefore, we potentially establish 'preemptive medicine,' that, in combination with early detection of abnormal epigenetic status and early administration of epigenetic-restoring drugs may prevent the development of disorders associated with the DOHaD.

Role of epigenetics in Rett syndrome

Rett syndrome (RTT) is an X-linked neurodevelopmental disease caused by MECP2 mutations. The MeCP2 protein was originally thought to function as a transcription repressor by binding to methylated CpG dinucleotides, but is now also thought to be a transcription activator. Recent studies suggest that MeCP2 is not only being expressed in neurons, but also in glial cells, which suggests a new paradigm for understanding the pathogenesis of RTT. It has also been demonstrated that reintroduction of MeCP2 into behaviorally affected Mecp2-null mice after birth rescues neurological symptoms, which indicates that epigenetic failures in RTT are reversible. Therefore, RTT may well be seen as a model disease that can be potentially treated by taking advantage of the reversibility of epigenetic phenomena in various congenital neurodevelopmental diseases that were previously thought to be untreatable.

Epigenetic understanding of gene-environment interactions in psychiatric disorders: a new concept of clinical genetics

Epigenetics is a mechanism that regulates gene expression independently of the underlying DNA sequence, relying instead on the chemical modification of DNA and histone proteins. Although environmental and genetic factors were thought to be independently associated with disorders, several recent lines of evidence suggest that epigenetics bridges these two factors. Epigenetic gene regulation is essential for normal development, thus defects in epigenetics cause various rare congenital diseases. Because epigenetics is a reversible system that can be affected by various environmental factors, such as drugs, nutrition, and mental stress, the epigenetic disorders also include common diseases induced by environmental factors. In this review, we discuss the nature of epigenetic disorders, particularly psychiatric disorders, on the basis of recent findings: 1) susceptibility of the conditions to environmental factors, 2) treatment by taking advantage of their reversible nature, and 3) transgenerational inheritance of epigenetic changes, that is, acquired adaptive epigenetic changes that are passed on to offspring. These recently discovered aspects of epigenetics provide a new concept of clinical genetics.

Genomic imprinting of insulin-like growth factor 2 (IGF-2) in chronic synovitis

OBJECTIVE

To search for relaxation or loss of IGF-2 imprinting (LOI) in rheumatoid arthritis (RA) synovial tissues.

DESIGN

The genotype of IGF-2 was determined in 25 freshly isolated synovial tissue samples with signs of active inflammation by polymerase chain reaction (PCR) and restriction fragment length polymorphism. Imprinting was determined in synovial tissue mononuclear cells (STMC) of five informative heterozygous patients by reverse transcriptase (RT)-PCR. Mitogen-stimulated peripheral blood mononuclear cells (PBMC) from six informative healthy donors were selected for control.

RESULTS

In vitro proliferation of CD4+ and CD8+ PB T cells, and also of CD19+ PB B cells was detectable upon mitogen stimulation. Furthermore, MHC II molecule expression on synovial B and T cells indicated in vivo cell activation. Monoallelic IGF-2 expression was seen in PBMC cultures from two healthy donors under both, resting and stimulating conditions. In two other PBMC cultures, LOI occurred exclusively after 24 h of stimulation. PBMC from two other healthy donors showed LOI under both, resting and stimulating conditions. Mitogen induced and spontaneous LOI was reversible in each one PBMC culture after 72 h. In contrast, none of the informative STMC cultures showed LOI.

CONCLUSIONS

LOI in lymphocytes may occur spontaneously or inducible. However, longstanding activation of lymphocytes in RA synovitis appears not to be related to this mechanism.

Genetics of the female reproductive ducts

Familial aggregates of the most common disorders of müllerian differentiation in females-Müllerian aplasia, incomplete Müllerian fusion-are best explained on the basis of polygenic/multifactorial inheritance. No information exists on the number and chromosomal location of responsible genes. Single mutant genes (Mendelian) are responsible for the McKusick-Kaufman syndrome (MKS) and the hand-foot-genital syndrome. The molecular basis for the latter condition involves HOXA13, but the molecular basis of MKS and other disorders of the female reproductive ducts is unknown. Vaginal atresia, Müllerian aplasia, and incomplete Müllerian fusion are not infrequently observed in malformation syndromes.

Mouse mutant embryos overexpressing IGF-II exhibit phenotypic features of the Beckwith-Wiedemann and Simpson-Golabi-Behmel syndromes

In mice, the imprinted Igf2 gene (expressed from the paternal allele), which encodes a growth-promoting factor (IGF-II), is linked closely to the reciprocally imprinted H19 locus on chromosome 7. Also imprinted (expressed from the maternal allele) is the Igf2r gene on chromsome 17 encoding the type 2 IGF receptor that is involved in degradation of excess IGF-II. Double mutant embryos carrying a deletion around the H19 region and also a targeted Igf2r allele, both inherited maternally, have extremely high levels of IGF-II (7- and 11-fold higher than normal in tissues and serum, respectively) as a result of biallelic Igf2 expression (imprint relaxation by deletion of H19-associated sequence) in combination with lack of the IGF2R-mediated IGF-II turnover. This excess of IGF-II causes somatic overgrowth, visceromegaly, placentomegaly, omphalocele, and cardiac and adrenal defects, which are also features of the Beckwith-Wiedemann syndrome (BWS), a genetically complex human disorder associated with chromosomal abnormalities in the 11p15.5 region where the IGF2 gene resides. In addition, the double mutant mouse embryos exhibit skeletal defects and cleft palate, which are manifestations observed frequently in the Simpson-Golabi-Behmel syndrome, another overgrowth disorder overlapping phenotypically, but not genetically, with BWS.

Characterization of a human glutathione S-transferase mu cluster containing a duplicated GSTM1 gene that causes ultrarapid enzyme activity

The mu class glutathione S-transferase gene GSTM1 is polymorphic in humans, with approximately half of the Caucasian population being homozygous deleted for this gene. GSTM1 enzyme deficiency has been suggested to predispose people to lung and bladder cancer. Some people in a Saudi Arabian population, however, have been described previously with ultrarapid GSTM1 enzyme activity. Here we have evaluated the molecular genetic basis for this observation. Genomic DNA from two Saudi Arabian subjects exhibiting ultrarapid enzyme activity and from 13 Swedish subjects having null, one, or two GSTM1 genes were subjected to restriction fragment length polymorphism analysis using the restriction enzymes EcoRI, EcoRV, and HindIII and combinations thereof. Hybridization was carried out using a full-length GSTM1 cDNA or the 5' and 3' parts of the cDNA. The restriction mapping data revealed the presence of a GST mu cluster with two GSTM1 genes in tandem situated between the GSTM2 and GSTM5 genes. A quantitative multiplex polymerase chain reaction method, which simultaneously amplified a fragment of the GSTM1 gene and the beta-globin gene, was developed, and the genomic GSTM1 copy number was determined from the GSTM1/beta-globin ratio. This method clearly separated GSTM1 +/- subjects (ratios between 0.4 and 0.7) from GSTM1 +/+ subjects (ratios between 0.8 and 1.2). The two Saudi Arabians with ultrarapid GSTM1 activities had ratios of approximately 1.5, indicating that they carried three GSTM1 genes. These results demonstrate the existence of a novel mu class GST cluster containing a duplicated active GSTM1 gene causing ultrarapid enzyme activity.

Paternally inherited duplications of 11p15.5 and Beckwith-Wiedemann syndrome

We present a three generation family in which a father and son have a balanced chromosome translocation between the short arms of chromosomes 5 and 11 (karyotype 46,XY,t(5;11)(p15.3;p15.3)). Two family members have inherited the unbalanced products of this translocation and are trisomic for chromosome 11p15.3-->pter and monosomic for chromosome 5p15.3-->pter (karyotype 46,XY,der(5)t(5;11)(p15.3;p15.3)pat). Paternally derived duplications of 11p15.5 are associated with Beckwith-Wiedemann syndrome (BWS) and both family members trisomic for 11p15.5 had prenatal overgrowth (birth weights >97th centile), macroglossia, coarse facial features, and broad hands. We review the clinical features of BWS patients who have a paternally derived duplication of 11p15.5 and provide evidence for a distinct pattern of dysmorphic features in those with this chromosome duplication. Interestingly, our family is the fifth unrelated family to be reported with a balanced reciprocal translocation between the short arms of chromosomes 5 and 11. The apparently non-random nature of this particular chromosome translocation is suggestive of sequence homology between the two chromosome regions involved in the translocation.

Nonimmune fetal hydrops and placentomegaly: diagnosis of familial Wiedemann-Beckwith syndrome with trisomy 11p15 using FISH

We have studied a family in which four members of the same generation were affected with Wiedemann-Beckwith syndrome (WBS). Trisomy 11p15 was demonstrated using molecular probes in interphase nuclei of formalin-fixed paraffin-embedded placenta from a stillborn fetus and in peripheral blood lymphocytes from two liveborn female relatives. Clinical examination showed nonimmune hydrops and placentomegaly in two siblings and multiple phenotypic abnormalities consistent with WBS in the two other relatives. Paternal karyotype of the stillborn infants demonstrated a reciprocal translocation (46,XY,t(10;11) (q26;p15)) explaining the origin of the extra 11p15 material. This study illustrates the advantages of FISH for interphase analysis of chromosome aberrations otherwise not detected even by conventional cytogenetic analysis and documents that nonimmune hydrops associated with placentomegaly may be the presenting features in familial WBS.

Two pairs of male monozygotic twins discordant for Wiedemann-Beckwith syndrome

Wiedemann-Beckwith syndrome (WBS) is a congenital anomaly syndrome which classically consists of exomphalos, macroglossia, and gigantism. The syndrome is also associated with a variety of minor anomalies and affected individuals have an increased risk of developing rare embryonal cell tumors. To date, 15 monozygotic (MZ) twin pairs have been reported of which 13 are discordant for WBS. All except one pair of the discordant WBS twin pairs have been female. We report two pairs of male MZ twins, each discordant for WBS.