Prader-Willi syndrome with an unusually large 15q deletion due to an unbalanced translocation t(4;15)

Expanded Prader-Willi Syndrome due to an Unbalanced de novo Translocation t(14;15): Report and Review of the Literature

In the present study, we report a case of a female infant with a de novo unbalanced t(14;15) translocation resulting in a 14-Mb deletion of the 15q11.1q14 region. The deletion includes the 15q11.2q13 Prader-Willi syndrome (PWS) critical region, while no known deleted genes are found in the 14qter region. According to literature review, patients with similar or larger deletions in the 15q region exhibit an expanded phenotype of PWS with case-specific atypical features such as severe retardation, absence of speech, microcephaly, retrognathia, bifid uvula, ear malformations, and heart defects in addition to typical features of PWS. Our proband exhibited increased deep tendon reflexes, an atypical feature which is not reported in the reviewed literature. The severity of the phenotype is not directly associated with the size of the deletion; however, using a combination of methods, the identification of breakpoints and the deleted genes can be helpful for the prognostication in patients with atypical PWS deletions.

Atypical Prader-Willi and 15q13.3 Microdeletion Syndromes in a Patient with an Unbalanced Translocation

Prader-Willi syndrome (PWS) and recurrent 15q13.3 microdeletion syndrome can be caused by genomic rearrangements in the complex 15q11q13 chromosomal region. Here, we describe the first female child with PWS and 15q13.3 microdeletion syndrome resulting from an unusual 10.7-Mb deletion from 15pter to 15q13.3 due to an unbalanced de novo 15;19 translocation. The patient presents with hypotonia, microcephaly, developmental delay with lack of speech, intellectual disability, happy demeanor, clinodactyly of the 4th and 5th fingers, and dysmorphic facial features discordant for PWS and consistent with an atypical phenotype.

Angelman Syndrome due to familial translocation: unexpected additional results characterized by Microarray-based Comparative Genomic Hybridization

Background

The 15q11q13 region is subject to imprinting and is involved in various structural rearrangements. Less than 1% of Angelman Syndrome patients are due to translocations involving 15q11q13. These translocations can arise de novo or result from the segregation of chromosomes involved in a familial balanced translocation.

Results

A 5-year-old Mexican girl presented with developmental delay, minor dysmorphic features and history of exotropia. G-banding chromosome analysis established the diagnosis of Angelman Syndrome resulting from a familial translocation t(10;15) involving the 15q11.2 region. The available family members were studied using banding and molecular cytogenetic techniques, including Microarray-based Comparative Genomic Hybridization, which revealed additional unexpected results: a coincidental and smaller 15q deletion, asymptomatic duplications in 15q11.2 and Xp22.31 regions.

Conclusions

This report demonstrates the usefulness of array CGH for a detailed characterization of familial translocations, including the detection of submicroscopic copy number variations, which would otherwise be missed by karyotype analysis alone. Our report also expands two molecularly characterized rare patient cohorts: Angelman Syndrome patients due to familial translocations and patients with 15q11.2 duplications of paternal origin.

A case of an atypically large proximal 15q deletion as cause for Prader-Willi syndrome arising from a de novo unbalanced translocation

We describe an 11 month old female with Prader-Willi syndrome (PWS) resulting from an atypically large deletion of proximal 15q due to a de novo 3;15 unbalanced translocation. The 10.6 Mb deletion extends from the chromosome 15 short arm and is not situated in a region previously reported as a common distal breakpoint for unbalanced translocations. There was no deletion of the reciprocal chromosome 3q subtelomeric region detected by either chromosomal microarray or FISH. The patient has hypotonia, failure to thrive, and typical dysmorphic facial features for PWS. The patient also has profound global developmental delay consistent with an expanded, more severe, phenotype.

Expanded Prader-Willi syndrome due to chromosome 15q11.2-14 deletion: report and a review of literature

We report on a male infant with de novo unbalanced t(5;15) translocation resulting in a 17.23 Mb deletion within 15q11.2-q14 and a 25.12 kb deletion in 5pter. The 15q11.2-q14 deletion encompassed the 15q11.2-q13 Prader-Willi syndrome (PWS) critical region and the recently described 15q13.3 microdeletion syndrome region while the 5pter deletion contained no RefSeq genes. From our literature review, patients with similar deletions in chromosome 15q exhibit expanded phenotype of severe developmental delay, protracted feeding problem, absent speech, central visual impairment, congenital malformations and epilepsy in addition to those typical of PWS. The patient reported herein had previously unreported anomalies of mega cisterna magna, horseshoe kidney and the rare neonatal interstitial lung disease known as pulmonary interstitial glycogenosis. Precise breakpoint delineation by microarray is useful in patients with atypical PWS deletions to guide investigation and prognostication.

Genetic studies of Prader-Willi patients provide evidence for conservation of genomic architecture in proximal chromosome 15q

Prader-Willi syndrome (PWS) is a neurogenetic disorder associated with recurrent genomic recombination involving low copy repeats (LCRs) located in the human chromosome 15q11-q13. Previous studies of PWS patients from Asia suggested that there is a higher incidence of deletion and lower incidence of maternal uniparental disomy (mUPD) compared to that of Western populations. In this report, we present genetic etiology of 28 PWS patients from Taiwan. Consistent with the genetic etiology findings from Western populations, the type II deletion appears to be the most common deletion subtype. Furthermore, the ratio of the two most common deletion subtypes and the ratio of the maternal heterodisomy to isodisomy cases observed from this study are in agreement with previous findings from Western populations. In addition, we identified and further mapped the deletion breakpoints in two patients with atypical deletions using array CGH (comparative genomic hybridization). Despite the relatively small numbers of patients in each subgroup, our findings suggest that the genomic architecture responsible for the recurrent recombination in PWS is conserved in Taiwanese of the Han Chinese heritage and Western populations, thereby predisposing chromosome 15q11-q13 to a similar risk of rearrangements.

De novo interstitial duplication of the 15q11.2-q14 PWS/AS region of maternal origin: Clinical description, array CGH analysis, and review of the literature

The 15q11-q13 PWS/AS critical region involves genes that are characterized by genomic imprinting. Multiple repeat elements within the region mediate rearrangements, including interstitial duplications, interstitial triplications, and supernumerary isodicentric marker chromosomes, as well as the deletions that cause Prader-Willi syndrome (PWS) and Angelman syndrome (AS). Recently, duplications of maternal origin concerning the same critical region have been implicated in autism spectrum disorders (ASD). We present a 6-month-old girl carrying a de novo duplication of maternal origin of the 15q11.2-q14 PWS/AS region (17.73 Mb in size) [46,XX,dup(15)(q11.2-q14)] detected with a high-resolution microarray-based comparative genomic hybridization (array-CGH). The patient is characterized by severe hypotonia, obesity, microstomia, long eyelashes, hirsutism, microretrognathia, short nose, severe psychomotor retardation, and multiple episodes of drug-resistant epileptic seizures, while her brain magnetic resonance imaging (MRI) documented partial corpus callosum dysplasia. In our patient the duplicated region is quite large extending beyond the Prader-Willi-Angelman critical region (PWACR), containing a number of genes that have been shown to be involved in ASD, exhibiting a severe phenotype, beyond the typical PWS/AS clinical manifestations. Reporting of similar well-characterized clinical cases with clearly delineated breakpoints of the duplicated region will clarify the contribution of specific genes to the phenotype.

An interstitial 15q11-q14 deletion: expanded Prader-Willi syndrome phenotype

We present an infant girl with a de novo interstitial deletion of the chromosome 15q11-q14 region, larger than the typical deletion seen in Prader-Willi syndrome (PWS). She presented with features seen in PWS including hypotonia, a poor suck, feeding problems, and mild micrognathia. She also presented with features not typically seen in PWS such as preauricular ear tags, a high-arched palate, edematous feet, coarctation of the aorta, a PDA, and a bicuspid aortic valve. G-banded chromosome analysis showed a large de novo deletion of the proximal long arm of chromosome 15 confirmed using FISH probes (D15511 and GABRB3). Methylation testing was abnormal and consistent with the diagnosis of PWS. Because of the large appearing deletion by karyotype analysis, an array comparative genomic hybridization (aCGH) was performed. A 12.3 Mb deletion was found which involved the 15q11-q14 region containing approximately 60 protein coding genes. This rare deletion was approximately twice the size of the typical deletion seen in PWS and involved the proximal breakpoint BP1 and the distal breakpoint was located in the 15q14 band between previously recognized breakpoints BP5 and BP6. The deletion extended slightly distal to the AVEN gene including the neighboring CHRM5 gene. There is no evidence that the genes in the 15q14 band are imprinted; therefore, their potential contribution in this patient's expanded PWS phenotype must be a consequence of dosage sensitivity of the genes or due to altered expression of intact neighboring genes from a position effect.

Trisomy 9p and Prader-Willi syndromes in an infant resulting from a de-novo unbalanced t(9;15) translocation

Trisomy 9p is a well-described dysmorphic syndrome. The physical features include hypertelorism, down-slanting palpebral fissures, deep-set eyes, down-turned corners of the mouth, and mild skeletal anomalies including hypoplastic terminal phalanges. We report an infant born with some of the typical features of trisomy 9p syndrome, as well as additional features that include extreme joint hyperlaxity with subluxation of the knees and elbows, arachnodactyly, and total anomalous pulmonary venous return. The karyotype revealed an unbalanced chromosome complement. Specifically, a derivative chromosome from a de-novo unbalanced translocation of chromosomes 9 and 15 resulted in partial trisomy of 9pter to 9q13 and deletion of the long arm of chromosome 15 proximal to band q13. Fluorescence in-situ hybridization studies and methylation analysis by Southern blotting revealed deletion of the SNRPN locus on the paternally derived chromosome 15, consistent with Prader-Willi syndrome. This infant represents the first reported case of trisomy 9p syndrome with total anomalous pulmonary venous return and hypoplasia of the amygdala and hippocampus, with the additional finding of Prader-Willi syndrome resulting from a derivative chromosome arising from an unbalanced de-novo t(9;15) translocation.

Reduction of DNA damage in older healthy adults by Tri E Tocotrienol supplementation

OBJECTIVE

The free radical theory of aging (FRTA) suggests that free radicals are the leading cause of deteriorating physiologic function during senescence. Free radicals attack cellular structures or molecules such as DNA resulting in various modifications to the DNA structures. Accumulation of unrepaired DNA contributes to a variety of disorders associated with the aging process.

METHODS

A randomized, double-blinded placebo-controlled study was undertaken to evaluate the effect of Tri E Tocotrienol on DNA damage. Sixty four subjects 37-78 y old completed the study. A daily dose of 160 mg of Tri E Tocotrienol was given for 6 months. Blood samples were analyzed for DNA damage using comet assay, frequency of sister chromatid exchange (SCE), and chromosome 4 aberrations.

RESULTS

Results showed a significant reduction in DNA damage as measured by comet assay after 3 mo (P < 0.01) and remained low at 6 mo (P < 0.01). The frequency of SCE was also reduced after 6 mo of supplementation (P < 0.05), albeit more markedly in the >50 y-old group (P < 0.01) whereas urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG) levels were significantly reduced (P < 0.05). A strong positive correlation was observed between SCE with age, whereas weak positive correlations were observed in DNA damage and 8-OHdG, which were reduced with supplementation. However, no translocation or a stable insertion was observed in chromosome 4.

CONCLUSION

Tri E Tocotrienol supplementation may be beneficial by reducing DNA damage as indicated by a reduction in DNA damage, SCE frequency, and urinary 8-OHdG.

Recurrent rearrangements in the proximal 15q11–q14 region: a new breakpoint cluster specific to unbalanced translocations

Unbalanced translocations, that involve the proximal chromosome 15 long arm and the telomeric region of a partner chromosome, result in a karyotype of 45 chromosomes with monosomy of the proximal 15q imprinted region. Here, we present our analysis of eight such unbalanced translocations that, depending on the parental origin of the rearranged chromosome, were associated with either Prader-Willi or Angelman syndrome. First, using FISH with specific BAC clones, we characterized the chromosome 15 breakpoint of each translocation and demonstrate that four of them are clustered in a small 460 kb interval located in the proximal 15q14 band. Second, analyzing the sequence of this region, we demonstrate the proximity of a low-copy repeat 15 (LCR15)-duplicon element that is known to facilitate recombination events at meiosis and to promote rearrangements. The presence, in this region, of both a cluster of translocation breakpoints and a LCR15-duplicon element defines a new breakpoint cluster (BP6), which, to our knowledge, is the most distal breakpoint cluster described in proximal 15q. Third, we demonstrate that the breakpoints for other rearrangements including large inv dup (15) chromosomes do not map to BP6, suggesting that it is specific to translocations. Finally, the translocation breakpoints located within BP6 result in very large proximal 15q deletions providing new informative genotype-phenotype correlations.

Characterization of a 5.3 Mb deletion in 15q14 by comparative genomic hybridization using a whole genome “tiling path” BAC array in a girl with heart defect, cleft palate, and developmental delay

High-resolution array CGH utilizing sets of overlapping BAC and PAC clones ("tiling path") covering the whole genome is a powerful novel tool for fast detection of submicroscopic chromosome deletions or duplications. We describe the successful application of a submegabase resolution whole genome "tiling path" BAC array to confirm and characterize a de novo interstitial deletion of chromosome 15. The deletion has a size of 5.3 Mb and is located within chromosome band 15q14, distal to the Prader-Willi/Angelman region. The affected girl had a heart defect, cleft palate, recurrent infections, and developmental delay. In contrast to GTG banding, array CGH determined the exact number of deleted genes and thus allowed the identification of candidate genes for cleft palate (GREM1, CX36, MEIS2), congenital heart defect (ACTC, GREM1, CX36, MEIS2), and mental retardation (ARHGAP11A, CHRNA7, CHRM5).

Impact of molecular mechanisms, including deletion size, on Prader-Willi syndrome phenotype: study of 75 patients

Prader-Willi syndrome (PWS) can result from a 15q11-q13 paternal deletion, maternal uniparental disomy (UPD), or imprinting mutations. We describe here the phenotypic variability detected in 51 patients with different types of deletions and 24 patients with UPD. Although no statistically significant differences could be demonstrated between the two main types of PWS deletion patients, it was observed that type I (BP1-BP3) patients acquired speech later than type II (BP2-BP3) patients. Comparing the clinical pictures of our patients with UPD with those with deletions, we found that UPD children presented with lower birth length and started walking earlier and deletion patients presented with a much higher incidence of seizures than UPD patients. In addition, the mean maternal age in the UPD group was higher than in the deletion group. No statistically significant differences could be demonstrated between the deletion and the UPD group with respect to any of the major features of PWS. In conclusion, our study did not detect significant phenotypic differences among type I and type II PWS deletion patients, but it did demonstrate that seizures were six times more common in patients with a deletion than in those with UPD.