Obestatin and adropin in Prader-Willi syndrome and nonsyndromic obesity: Associations with weight, BMI-z, and HOMA-IR

The roles of obestatin and adropin in paediatric obesity are poorly understood. We compared obestatin and adropin concentrations in younger (n = 21) and older children (n = 14) with Prader-Willi syndrome (PWS) and age and BMI-z-matched controls (n = 31). Fasting plasma obestatin and adropin were higher in younger children with PWS than controls; adropin was also higher in older children with PWS. Growth hormone treatment had no effects on obestatin or adropin in PWS. The ratio of ghrelin to obestatin declined from early to late childhood but was higher in older PWS than older controls. Adropin correlated with fasting glucose in the PWS group only. Changes in the ratio of ghrelin to obestatin may suggest changes in the processing of preproghrelin to ghrelin and obestatin during development and differential processing of preproghrelin in PWS.

Prader-Willi syndrome genetic subtypes and clinical neuropsychiatric diagnoses in residential care adults

The historical diagnosis of Prader-Willi syndrome (PWS), a complex genetic disorder, in adults is often achieved by clinical presentation rather than by genetic testing and thus limited genetic subtype-specific psychometric investigations and treatment options. Genetic testing and clinical psychiatric evaluation using Diagnostic and Statistical Manual (DSM)-IV-TR criteria were undertaken on 72 adult residents (34 M; 38 F) from the Prader-Willi Homes of Oconomowoc (PWHO), a specialty PWS group home system. Methylation specific-multiplex ligation probe amplification and high-resolution microarrays were analyzed for methylation status, 15q11-q13 deletions and maternal uniparental disomy 15 (mUPD15). Seventy (33M; 37F) of 72 residents were genetically confirmed and 36 (51%) had Type I or Type II deletions; 29 (42%) with mUPD15 and 5 (7%) with imprinting defects from three separate families. Psychiatric comorbidities were classified as anxiety disorder (38%), excoriation (skin picking) (33%), intermittent explosive disorder ([30%-predominantly among males at 45% compared with females at 16% [OR = 4.3, 95%CI 1.4-13.1, P < 0.008]) and psychotic features (23%). Psychiatric diagnoses did not differ between mUPD15 vs deletion, but a greater number of psychiatric diagnoses were observed for the larger Type I (4.3) vs smaller Type II (3.6) deletions when age was controlled (F = 5.0, P < 0.04). Adults with PWS presented with uniformly higher rates of psychiatric comorbidities which differed by genetic subtype with gender-specific trends.

Examination of Global Methylation and Targeted Imprinted Genes in Prader-Willi Syndrome

CONTEXT

Methylation changes observed in Prader-Willi syndrome (PWS) may impact global methylation as well as regional methylation status of imprinted genes on chromosome 15 (in cis) or other imprinted obesity-related genes on other chromosomes (in trans) leading to differential effects on gene expression impacting obesity phenotype unique to (PWS).

OBJECTIVE

Characterize the global methylation profiles and methylation status for select imprinted genes associated with obesity phenotype in a well-characterized imprinted, obesity-related syndrome (PWS) relative to a cohort of obese and non-obese individuals.

DESIGN

Global methylation was assayed using two methodologies: 1) enriched LINE-1 repeat sequences by EpigenDx and 2) ELISA-based immunoassay method sensitive to genomic 5-methylcytosine by Epigentek. Target gene methylation patterns at selected candidate obesity gene loci were determined using methylation-specific PCR.

SETTING

Study participants were recruited as part of an ongoing research program on obesity-related genomics and Prader-Willi syndrome.

PARTICIPANTS

Individuals with non-syndromic obesity (N=26), leanness (N=26) and PWS (N=39).

RESULTS

A detailed characterization of the imprinting status of select target genes within the critical PWS 15q11-q13 genomic region showed enhanced cis but not trans methylation of imprinted genes. No significant differences in global methylation were found between non-syndromic obese, PWS or non-obese controls.

INTERVENTION

None.

MAIN OUTCOME MEASURES

Percentage methylation and the methylation index.

CONCLUSION

The methylation abnormality in PWS due to errors of genomic imprinting effects both upstream and downstream effectors in the 15q11-q13 region showing enhanced cis but not trans methylation of imprinted genes. Obesity in our subject cohorts did not appear to impact global methylation levels using the described methodology.

Prader-Willi syndrome: a review of clinical, genetic, and endocrine findings

INTRODUCTION

Prader-Willi syndrome (PWS) is a multisystemic complex genetic disorder caused by lack of expression of genes on the paternally inherited chromosome 15q11.2-q13 region. There are three main genetic subtypes in PWS: paternal 15q11-q13 deletion (65-75 % of cases), maternal uniparental disomy 15 (20-30 % of cases), and imprinting defect (1-3 %). DNA methylation analysis is the only technique that will diagnose PWS in all three molecular genetic classes and differentiate PWS from Angelman syndrome. Clinical manifestations change with age with hypotonia and a poor suck resulting in failure to thrive during infancy. As the individual ages, other features such as short stature, food seeking with excessive weight gain, developmental delay, cognitive disability and behavioral problems become evident. The phenotype is likely due to hypothalamic dysfunction, which is responsible for hyperphagia, temperature instability, high pain threshold, hypersomnia and multiple endocrine abnormalities including growth hormone and thyroid-stimulating hormone deficiencies, hypogonadism and central adrenal insufficiency. Obesity and its complications are the major causes of morbidity and mortality in PWS.

METHODS

An extensive review of the literature was performed and interpreted within the context of clinical practice and frequently asked questions from referring physicians and families to include the current status of the cause and diagnosis of the clinical, genetics and endocrine findings in PWS.

CONCLUSIONS

Updated information regarding the early diagnosis and management of individuals with Prader-Willi syndrome is important for all physicians and will be helpful in anticipating and managing or modifying complications associated with this rare obesity-related disorder.

EVALUATION OF PLASMA SUBSTANCE P AND BETA-ENDORPHIN LEVELS IN CHILDREN WITH PRADER-WILLI SYNDROME

BACKGROUND

Prader-Willi syndrome (PWS) is a rare obesity-related genetic disorder often caused by a deletion of the chromosome 15q11-q13 region inherited from the father or by maternal disomy 15. Growth hormone deficiency with short stature, hypogonadism, cognitive and behavioral problems, analgesia, decreased gastric motility and decreased ability to vomit with hyperphagia are common in PWS leading to severe obesity in early childhood, if not controlled. Substance P (SP) and beta-endorphin (BE) are neuropeptides involved with centrally and peripherally mediated pain perception, emotional regulation, and gastric motility impacting nausea, emesis and feeding patterns.

OBJECTIVE

The goal of this study was to investigate potential mechanisms for PWS symptom development for pain, emotion and gastric motility and plasma levels of substance P and beta-endorphin between PWS and unrelated unaffected children.

METHODOLOGY

Plasma samples were collected from 23 Caucasian children with PWS and 18 unrelated, unaffected siblings with an average age of 8.2 ±2.0 years and age range of 5 to 11 years following an overnight fast and neuropeptide substance p and beta-endorphin levels were assessed using Multiplex sandwich immunoassays using the Luminex magnetic-bead based platform. Linear regression analysis was carried out on log-transformed values adjusted for age, sex, and body mass index (BMI).

RESULTS

The mean plasma SP (57 ± 23 pg/ml) and BE (592 ± 200 pg/ml) levels in PWS were significantly higher than SP (35 ± 20 pg/ml, F=10.5, P<0.01) and BE (402 ± 162 pg/ml, F=10.8, P<0.01) levels found in unrelated, unaffected siblings suggesting a previously uncharacterized neuroendocrine pathophysiology in PWS.

CONCLUSIONS

The increased BE and SP plasma levels relative to unrelated, unaffected siblings may contribute to hyperphagia, abnormal pain sensation and adrenal insufficiency seen in PWS. Increases in SP levels may be modulated by central and/or peripheral actions of BE on opioid, GABA or POMC precursors and may reflect loss of feedback inhibitory control. Further studies are needed to confirm and elucidate the biochemical basis for observed disturbances in neuropeptide levels seen in our study and may impact on the development and persistence of symptoms commonly seen in PWS.

Over-expression of the miRNA cluster at chromosome 14q32 in the alcoholic brain correlates with suppression of predicted target mRNA required for oligodendrocyte proliferation

We examined miRNA expression from RNA isolated from the frontal cortex (Broadman area 9) of 9 alcoholics (6 males, 3 females, mean age 48 years) and 9 matched controls using both the Affymetrix GeneChip miRNA 2.0 and Human Exon 1.0 ST Arrays to further characterize genetic influences in alcoholism and the effects of alcohol consumption on predicted target mRNA expression. A total of 12 human miRNAs were significantly up-regulated in alcohol dependent subjects (fold change≥1.5, false discovery rate (FDR)≤0.3; p<0.05) compared with controls including a cluster of 4 miRNAs (e.g., miR-377, miR-379) from the maternally expressed 14q32 chromosome region. The status of the up-regulated miRNAs was supported using the high-throughput method of exon microarrays showing decreased predicted mRNA gene target expression as anticipated from the same RNA aliquot. Predicted mRNA targets were involved in cellular adhesion (e.g., THBS2), tissue differentiation (e.g., CHN2), neuronal migration (e.g., NDE1), myelination (e.g., UGT8, CNP) and oligodendrocyte proliferation (e.g., ENPP2, SEMA4D1). Our data support an association of alcoholism with up-regulation of a cluster of miRNAs located in the genomic imprinted domain on chromosome 14q32 with their predicted gene targets involved with oligodendrocyte growth, differentiation and signaling.

Effects of growth hormone treatment in adults with Prader-Willi syndrome

OBJECTIVE

Since limited data exist on adults with Prader-Willi syndrome (PWS) and growth hormone (GH) treatment, we report our experience on the effects of treatment for one year on body composition, physical activity, strength and energy expenditure, diet, general chemistry and endocrine data with quality of life measures.

DESIGN

We studied 11 adults with PWS (6F:5M; average age=32 yrs) over a 2 year period with GH treatment during the first year only. Electrolytes, IGF-I, glucose, thyroid, insulin, lipids, body composition, physical activity and strength, diet, energy expenditure and quality of life data were collected and analyzed statistically using linear modeling at baseline, at 12 months following GH therapy and at 24 months after treatment cessation for 12 months.

RESULTS

Total lean muscle mass was significantly increased (p<0.05) during GH treatment along with moderate-vigorous physical activity and plasma IGF-I and HDL levels, but returned to near baseline after treatment. Percent body fat decreased during the 12 months of GH treatment but increased after treatment.

CONCLUSIONS

Previously reported beneficial effects of GH treatment in children with PWS were found in our adults regarding body composition, physical activity and plasma HDL and IGF-I levels. Several beneficial effects diminished to near baseline after cessation of GH treatment for 12 months supporting the continuation of treatment in PWS into adulthood and possibly adults not previously treated during childhood.

Plasma cytokine levels in children with autistic disorder and unrelated siblings

BACKGROUND

The pathogenesis of autistic disorder (AD) is not clearly understood but genetic factors and the immune system have been implicated. Disturbed immunoglobulin levels and autoantibodies to neuronal elements have been reported in AD including cytokines encoded by genes involved with cell proliferation, migration and adhesion but there is a paucity of data comparing cytokine levels in children with AD and unrelated siblings without AD.

METHODS

We analyzed 39 plasma cytokines in 99 well-characterized children with AD between 5 and 10 years of age and 40 age and gender matched healthy unrelated siblings without AD under the same clinical assessments, specimen processing and laboratory conditions. Multiplex sandwich immunoassays were used with the Luminex fluorescent-bead based platform. Log-transformed values of the 29 cytokines meeting laboratory criteria for inclusion were analyzed by analysis of covariance with a general linear model adjusting for diagnosis, gender, diagnosis by gender interaction effects, age and days of specimen handling. The Tukey-Kramer post hoc test was used to control for multiple comparisons.

RESULTS

Eight of 29 cytokine levels analyzed were significantly lower in children with AD compared with unrelated siblings without the diagnosis of AD. Three of the cytokines are known to be involved with hematopoiesis and five with attraction of T-cells, natural killer cells and monocytes.

CONCLUSIONS

Plasma cytokine levels representing chemokines involved in the T-helper cell immune system and hematopoiesis were lower in the children with AD compared with unrelated siblings without AD necessitating further studies to confirm immunological disturbances influencing hematopiesis and antibody production in the children with AD. Linking genes that encode immune related proteins and cytokines are important to study for their impact on critical periods of brain development and function.

Global DNA promoter methylation in frontal cortex of alcoholics and controls

To determine if ethanol consumption and alcoholism cause global DNA methylation disturbances, we examined alcoholics and controls using methylation specific microarrays to detect all annotated gene and non-coding microRNA promoters and their CpG islands. DNA was isolated and immunoprecipitated from the frontal cortex of 10 alcoholics and 10 age and gender-matched controls then labeled prior to co-hybridization. A modified Kolmogorov-Smirnov test was used to predict differentially enriched regions (peaks) from log-ratio estimates of amplified vs input DNA. More than 180,000 targets were identified for each subject which correlated with >30,000 distinct, integrated peaks or high probability methylation loci. Peaks were mapped to regions near 17,810 separate annotated genes per subject representing hypothetical methylation targets. No global methylation differences were observed between the two subject groups with 80% genetic overlap, but extreme methylation was observed in both groups at specific loci corresponding with known methylated genes (e.g., H19) and potentially other genes of unknown methylation status. Methylation density patterns targeting CpG islands visually correlated with recognized chromosome banding. Our study provides insight into global epigenetic regulation in the human brain in relationship to controls and potentially novel targets for hypothesis generation and follow-up studies of alcoholism.

Importance of reward and prefrontal circuitry in hunger and satiety: Prader-Willi syndrome vs simple obesity

Background

The majority of research on obesity has focused primarily on clinical features (eating behavior, adiposity measures), or peripheral appetite-regulatory peptides (leptin, ghrelin). However, recent functional neuroimaging studies have demonstrated that some reward circuitry regions which are associated with appetite-regulatory hormones are also involved in the development and maintenance of obesity. Prader-Willi syndrome (PWS), characterized by hyperphagia and hyperghrelinemia reflecting multi-system dysfunction in inhibitory and satiety mechanisms, serves as an extreme model of genetic obesity. Simple (non-PWS) obesity (OB) represents an obesity control state.

Objective

This study investigated subcortical food motivation circuitry and prefrontal inhibitory circuitry functioning in response to food stimuli before and after eating in individuals with PWS compared with OB. We hypothesized that groups would differ in limbic regions (i.e., hypothalamus, amygdala) and prefrontal regions associated with cognitive control [i.e., dorsolateral prefrontal cortex (DLPFC), orbitofrontal cortex (OFC)] after eating.

Design and Participants

Fourteen individuals with PWS, 14 BMI- and age-matched individuals with OB, and 15 age-matched healthy-weight controls (HWC) viewed food and non-food images while undergoing functional MRI before (pre-meal) and after (post-meal) eating. Using SPM8, group contrasts were tested for hypothesized regions: hypothalamus, nucleus accumbens (NAc), amygdala, hippocampus, OFC, medial PFC, and DLPFC.

Results

Compared with OB and HWC, PWS demonstrated higher activity in reward/limbic regions (NAc, amygdala) and lower activity in hypothalamus and hippocampus, in response to food (vs. non-food) images pre-meal. Post-meal, PWS exhibited higher subcortical activation (hypothalamus, amygdala, hippocampus) compared to OB and HWC. OB showed significantly higher activity versus PWS and HWC in cortical regions (DLPFC, OFC) associated with inhibitory control.

Conclusion

In PWS compared with obesity per se, results suggest hyperactivations in subcortical reward circuitry and hypoactivations in cortical inhibitory regions after eating, which provides evidence of neural substrates associated with variable abnormal food motivation phenotypes in PWS and simple obesity.

Obese children show hyperactivation to food pictures in brain networks linked to motivation, reward and cognitive control

OBJECTIVE

To investigate the neural mechanisms of food motivation in children and adolescents, and examine brain activation differences between healthy weight (HW) and obese participants.

SUBJECTS

Ten HW children (ages 11-16; BMI < 85%ile) and 10 obese children (ages 10-17; BMI >95%ile) matched for age, gender and years of education.

MEASUREMENTS

Functional magnetic resonance imaging (fMRI) scans were conducted twice: when participants were hungry (pre-meal) and immediately after a standardized meal (post-meal). During the fMRI scans, the participants passively viewed blocked images of food, non-food (animals) and blurred baseline control.

RESULTS

Both groups of children showed brain activation to food images in the limbic and paralimbic regions (PFC/OFC). The obese group showed significantly greater activation to food pictures in the PFC (pre-meal) and OFC (post-meal) than the HW group. In addition, the obese group showed less post-meal reduction of activation (vs pre-meal) in the PFC, limbic and the reward-processing regions, including the nucleus accumbens.

CONCLUSION

Limbic and paralimbic activation in high food motivation states was noted in both groups of participants. However, obese children were hyper-responsive to food stimuli as compared with HW children. In addition, unlike HW children, brain activations in response to food stimuli in obese children failed to diminish significantly after eating. This study provides initial evidence that obesity, even among children, is associated with abnormalities in neural networks involved in food motivation, and that the origins of neural circuitry dysfunction associated with obesity may begin early in life.

Refining the 22q11.2 deletion breakpoints in DiGeorge syndrome by aCGH

Hemizygous deletions of the chromosome 22q11.2 region result in the 22q11.2 deletion syndrome also referred to as DiGeorge, Velocardiofacial or Shprintzen syndromes. The phenotype is variable but commonly includes conotruncal cardiac defects, palatal abnormalities, learning and behavioral problems, immune deficiency, and facial anomalies. Four distinct highly homologous blocks of low copy number repeat sequences (LCRs) flank the deletion region. Mispairing of LCRs during meiosis with unequal meiotic exchange is assumed to cause the recurrent and consistent deletions. The proximal LCR is reportedly located at 22q11.2 from 17.037 to 17.083 Mb while the distal LCR is located from 19.835 to 19.880 Mb. Although the chromosome breakpoints are thought to localize to the LCRs, the positions of the breakpoints have been investigated in only a few individuals. Therefore, we used high resolution oligonucleotide-based 244K microarray comparative genomic hybridization (aCGH) to resolve the breakpoints in a cohort of 20 subjects with known 22q11.2 deletions. We also investigated copy number variation (CNV) in the rest of the genome. The 22q11.2 breaks occurred on either side of the LCR in our subjects, although more commonly on the distal side of the reported proximal LCR. The proximal breakpoints in our subjects spanned the region from 17.036 to 17.398 Mb. This region includes the genes DGCR6 (DiGeorge syndrome critical region protein 6) and PRODH (proline dehydrogenase 1), along with three open reading frames that may encode proteins of unknown function. The distal breakpoints spanned the region from 19.788 to 20.122 Mb. This region includes the genes GGT2 (gamma-glutamyltransferase-like protein 2), HIC2 (hypermethylated in cancer 2), and multiple transcripts of unknown function. The genes in these two breakpoint regions are variably hemizygous depending on the location of the breakpoints. Our 20 subjects had 254 CNVs throughout the genome, 94 duplications and 160 deletions, ranging in size from 1 kb to 2.4 Mb. The presence or absence of genes at the breakpoints depending on the size of the deletion plus variation in the rest of the genome due to CNVs likely contribute to the variable phenotype associated with the 22q11.2 deletion or DiGeorge syndrome.

Analysis of the Prader-Willi syndrome chromosome region using quantitative microsphere hybridization (QMH) array

We previously developed a novel quantitative microsphere suspension hybridization (QMH) assay for high-throughput determination of genomic copy number by direct hybridization of unique sequence probes to genomic DNA followed by flow cytometric analysis. Herein, we describe the first clinical application of this assay examining the Prader-Willi syndrome (PWS) chromosome region at 15q11-13. We designed 30 unique sequence test probes (approximately 60 nucleotides each) spanning 11.37 Mb of chromosome 15q11.2-q13.3 and a disomic reference probe (Actin Beta, chromosome 7p22.1), conjugated to spectrally distinct polystyrene microsphere levels. All probes were hybridized to biotin-labeled genomic DNA in multiplex QMH reactions, and hybridization was detected using phycoerythrin-labeled streptavidin and analyzed by dual-laser flow cytometry. Copy number differences were distinguished by comparing mean fluorescence intensities (MFI) of the test probes to the reference probe in 20 individuals with PWS and six controls. The mean MFI ratio for deleted loci was 0.56 +/- 0.09 (n = 88) as compared to the MFI ratios for normal loci, 0.96 +/- 0.06 (n = 236), and duplicated loci, 1.44 +/- 0.10 (n = 22). A multiplex QMH assay could readily distinguish type I from type II deletions in PWS subjects, as well as small (approximately 4.3 kb) imprinting center (IC) deletions, with no overlap in MFI values compared with normal loci. Using this diagnostic QMH assay, the precise deleted genomic interval could be ascertained in all PWS subjects examined in the present study.

Comparison of X-chromosome inactivation patterns in multiple tissues from human females

BACKGROUND

X-chromosome inactivation (XCI) is the mechanism by which gene dosage uniformity is achieved between female mammals with two X chromosomes and male mammals with a single X chromosome, and is thought to occur randomly. For molecular genetic testing, accessible tissues (eg blood) are commonly studied, but the relationship with inaccessible tissues (eg brain) is poorly understood. For accessible tissues to be informative for genetic analysis, a high degree of concordance of genetic findings among tissue types is required.

OBJECTIVE

To determine the relationship among multiple tissues within females at different ages (fetus to 82 years).

METHODS

XCI patterns were analysed using the polymorphic androgen receptor (AR) gene assay. DNA was isolated from 26 different human females without history of malignancy, using 34 autopsy tissues representing the three embryonic germ layers.

RESULTS

33 of the 280 tissue samples analysed from 13 of the 26 females showed skewed XCI values (>80:20%). Average XCI value was not significantly different among the tissues, but a trend for increasing XCI variability was observed with age in blood and other tissues studied (eg the SD for all tissues studied for the 0-2 years group was 9.9% compared with 14.8% in the >60 years group). We found a significant correlation (r(s) = 0.51, p = 0.035) between XCI values for blood and/or spleen and brain tissue, and in most other tissues representing the three embryonic germ layers.

CONCLUSIONS

In our study, XCI data were comparable among accessible (eg blood) and inaccessible tissues (eg brain) in females at various ages, and may be useful for genetic testing. A trend was seen for greater XCI variability with increasing age, particularly in older women (>60 years).

The relationship between compulsive behaviour and academic achievement across the three genetic subtypes of Prader-Willi syndrome

BACKGROUND

Prader-Willi syndrome (PWS) is a genetic syndrome associated with several physical, cognitive and behavioural characteristics. For many individuals with this syndrome, compulsive behaviour is often noted in both food and non-food situations. The focus of this paper is on the non-food-related compulsions in individuals with PWS and comparing differences across the three genetic subtypes of the syndrome.

METHODS

Compulsive behaviours in 73 people with PWS were assessed using the Yale-Brown Obsessive Compulsive Scale and the Compulsive Behavior Checklist. Compulsive behaviour and its relation to IQ and academic achievement also were evaluated. Phenotypic differences were characterized for the three most common genetic subtypes of the disorder: 16 individuals with the long Type I (TI) 15q deletion, 26 individuals with the short Type II (TII) 15q deletion and 31 individuals with maternal disomy 15.

RESULTS

There appeared to be important differences between the two deletion subtypes. Specifically, individuals with the TI deletion had more compulsions regarding personal cleanliness (i.e. excessive bathing/grooming), and their compulsions were more difficult to interrupt and interfered with social activities more than the other subtypes. Individuals with the TII deletion were more likely to have compulsions related to specific academic areas (i.e. rereading, erasing answers and counting objects or numbers).

CONCLUSIONS

These findings may help clinicians and researchers identify possible intervention strategies and supports based on the behavioural phenotype associated with genetic subtype in individuals with PWS.

Subset of individuals with autism spectrum disorders and extreme macrocephaly associated with germline PTEN tumour suppressor gene mutations

The genetic aetiology of autism remains elusive. Occasionally, individuals with Cowden syndrome (a cancer syndrome) and other related hamartoma disorders such as Bannayan-Riley-Ruvalcaba syndrome, Proteus syndrome, and Proteus-like conditions, are characterised by germline PTEN mutations, and may have neurobehavioural features resembling autism as well as overgrowth and macrocephaly. Therefore, we undertook PTEN gene mutation analysis in 18 subjects mainly prospectively ascertained with autism spectrum disorder and macrocephaly. Of these 18 autistic subjects (13 males and five females; ages 3.1-18.4 years) with a head circumference range from 2.5 to 8.0 standard deviations above the mean, three males (17%) carried germline PTEN mutations. These three probands had previously undescribed PTEN mutations: H93R (exon 4), D252G (exon 7), and F241S (exon 7). They had the larger head circumference measurements amongst all our study subjects. The three residues altered in our patients were highly evolutionarily conserved. We suggest that PTEN gene testing be considered for patients with autistic behaviour and extreme macrocephaly. The gene findings may impact on recurrence risks as well as medical management for the patient.

Novel splice isoforms for NLGN3 and NLGN4 with possible implications in autism

OBJECTIVE

To screen cDNA for NLGN3 and NLGN4 from lymphoblastoid cells from autistic subjects.

METHODS AND RESULTS

10 young autistic females and 30 non-autistic subjects were studied for alterations in two X linked genes, NLGN3 and NLGN4. A novel NLGN4 isoform lacking exon 4, which occurred de novo on the paternal allele, was identified in one of the autistic females. Monoallelic expression of NLGN4 was seen in this subject and in 11 of 14 informative autistic and non-autistic females using a single nucleotide polymorphism found at 3' UTR. Additionally, the NLGN3 transcript was present in two isoforms (with and without exon 7) in nine of 10 autistic females and in 30 non-autistic subjects, including parents of the autistic female having only the complete transcript with exon 7, and from the whole brain of a control. The novel truncated NLGN3 product may have a regulatory role, as reported in other proteins (for example, vasopressin receptor) by attenuating the function of the full length isoform, resulting in a reduction of the mature protein. Three dimensional protein structures were characterised using comparative modelling, and significant changes were suggested in the protein cores for these two neuroligin isoforms.

CONCLUSIONS

Splice variants may lead to potentially abnormal neuroligins in the causation of autism spectrum disorders.

Brief report: non-random X chromosome inactivation in females with autism

Autism is a heterogeneous neurodevelopmental disorder with a 3-4 times higher sex ratio in males than females. X chromosome genes may contribute to this higher sex ratio through unusual skewing of X chromosome inactivation. We studied X chromosome skewness in 30 females with classical autism and 35 similarly aged unaffected female siblings as controls using the polymorphic androgen receptor (AR) gene. Significantly, increased X chromosome skewness (e.g., >80:20%) was detected in our autism group (33%) compared to unaffected females (11%). X chromosome skewness was also seen in 50% of the mothers with autistic daughters. No mutation was seen in the promoter region of the XIST gene reported to be involved in X chromosome inactivation in our subjects. X chromosome skewness has been reported in female carriers of other neurological disorders such as X-linked mental retardation, adrenoleukodystrophy and Rett syndrome.

Circulating adiponectin levels, body composition and obesity-related variables in Prader-Willi syndrome: comparison with obese subjects

BACKGROUND

People with obesity and/or the metabolic syndrome have an increased risk for developing diabetes and cardiovascular disease and may have low adiponectin levels. The obesity associated with Prader-Willi syndrome (PWS) would be expected to have similar complications. However, it was recently reported that, despite their adiposity, people with PWS have reduced visceral fat and are less likely to develop diabetes mellitus or the metabolic syndrome compared with people with simple obesity.

OBJECTIVE

To determine if plasma adiponectin levels and other variables relevant to diabetes and cardiovascular risk are different in a cohort of PWS subjects with known genetic subtypes compared with age-, sex- and weight-matched control subjects.

RESULTS

Fasting plasma glucose, C-peptide, triglycerides, leptin and cholesterol levels were similar in PWS and obese subjects. Our 20 PWS subjects (mean age = 27.7 years) had higher percent body fat (54.1 vs 48.5%) determined by DEXA measurements and lower percent lean mass (45.9 vs 51.5%) compared with 14 obese controls (mean age = 26.9 year). Plasma adiponectin levels were significantly higher in PWS (15.5 +/- 8.2 microg/ml) than in obese controls (7.5 +/- 2.7 microg/ml). A significant positive correlation was found with insulin sensitivity in PWS subjects (r = 0.75, P = 0.0003) but not in obese controls (r = 0.36, P = 0.20).

DISCUSSION

Our study confirmed an earlier observation of higher adiponectin levels in PWS subjects and less insulin resistance proportionate to their obesity status than found in subjects with simple obesity. Furthermore, no differences were seen in PWS subjects with the chromosome 15 deletion or maternal disomy 15. The reported excessive visceral adiposity in subjects with simple obesity compared with PWS may be associated with decreased production and lower circulating levels of adiponectin.

A measure of food seeking in individuals with Prader-Willi syndrome

BACKGROUND

Individuals with Prader-Willi syndrome (PWS), a chromosome 15 genetic disorder, often have a significant preoccupation with food and problem behaviour related to food seeking is often prevalent.

METHODS

In the present study, we compared how individuals with PWS responded on a survey regarding the acceptability of food in various locations that varied according to degree of appropriateness for human consumption (e.g. food on a plate, food in a garbage can). For a subgroup of participants, we observed how they actually responded when placed in a room with food items placed in the same locations depicted in the survey. In the first part of the study, three groups (25 typically developing individuals, 7 individuals with intellectual disability (ID), and 19 individuals with PWS) responded to a visual survey to determine the degree of acceptability of food items in various locations (e.g. on a table near a hairbrush, on the floor behind a toy box, in a trash can). In the second part of the study, these food items (popcorn, jelly beans) were placed in the 12 locations described above. Nine individuals diagnosed with PWS (deletion type) and three individuals with ID were given some break time in the room for 15 min. The amount of food consumed, the time spent food seeking, and time spent interacting with materials were measured.

RESULTS

Results of the survey indicated that the PWS group differed significantly with regard to how they responded on the survey from the typically developing group, but did not differ significantly from the ID group. Results of the food seeking observations indicated that only three individuals with PWS ate a significant number of items. The three individuals did not differ from the rest of the group according to IQ or compulsivity score; however, they had significantly lower body mass index (BMI) scores and were younger than the other participants.

CONCLUSIONS

The findings from the survey indicate that individuals with PWS are able to discriminate the appropriateness of eating items in more or less contaminated areas; however, the amount of time spent seeking food and the amount of food covertly consumed appeared to depend more directly on age and BMI.

Insulin resistance and obesity-related factors in Prader-Willi syndrome: comparison with obese subjects

Prader-Willi syndrome (PWS), the most common genetic cause of marked obesity in humans, is usually due to a de novo paternally derived chromosome 15q11-q13 deletion or maternal disomy 15 [(uniparental disomy (UPD)]. Obesity is due to energy imbalance, but few studies have examined fat patterning and obesity-related factors in subjects with PWS (deletions and UPD) compared with subjects with simple obesity. We examined for differences in fatness patterning and lipid, leptin, and glucose and insulin levels in subjects with simple obesity and PWS and adjusted for gender, age, and body mass index (BMI). Fasting peripheral blood samples and cross-sectional magnetic resonance image scans at the level of the umbilicus were obtained in 55 subjects ranging in age from 10.4 to 49 years: 20 PWS deletion, 17 PWS UPD, and 18 obese controls. Subcutaneous fat area (SFA) and intra-abdominal visceral fat area (VFA) were calculated. No significant difference was seen between the PWS deletion subjects or PWS UPD subjects for fatness measurements or leptin levels. Twenty-three of 37 PWS subjects met the criteria for obesity (BMI > 95th percentile). No significant differences were observed for SFA and VFA between the PWS subjects judged to be obese and control subjects with simple obesity. There was an overall trend for decreased VFA in the PWS subjects but not significantly different. VFA was significantly positively correlated with both fasting insulin and total cholesterol in PWS deletion subjects but not in PWS UPD subjects or obese controls. Fasting insulin level was significantly lower in the obese PWS subjects compared with subjects with simple obesity, and insulin sensitivity (QUICKI) was significantly higher in PWS subjects with obesity. Homeostasis model assessment (HOMA) and QUICKI values were correlated and in opposite directions with triglycerides in the obese PWS subjects but not in the obese controls. Subjects in each group were stratified according to published criteria on the basis of their level of visceral fat (e.g. > or = 130 cm(2)) to assess the influence of VFA on metabolic abnormalities. In the obese PWS subjects, the fasting triglyceride, glucose, and insulin levels, and HOMA value were significantly elevated, while the QUICKI value was significantly lower in those with VFA > or = 130 cm(2). Such significant differences were not seen in the obese control group. Our results indicate that VFA may be regulated differently in PWS subjects compared to individuals with simple obesity. Insulin resistance is lower in PWS subjects and insulin sensitivity is higher compared with obese controls. PWS subjects with increased VFA may be at a higher risk of obesity-related complications compared to PWS subjects without increased VFA.

Microarray analysis of gene/transcript expression in Prader-Willi syndrome: deletion versus UPD

BACKGROUND

Prader-Willi syndrome (PWS), the most common genetic cause of marked obesity, is caused by genomic imprinting and loss of expression of paternal genes in the 15q11-q13 region. There is a paucity of data examining simultaneous gene expression in this syndrome.

METHODS

We generated cDNA microarrays representing 73 non-redundant genes/transcripts from the 15q11-q13 region, the majority within the PWS critical region and others distally on chromosome 15. We used our custom microarrays to compare gene expression from actively growing lymphoblastoid cell lines established from nine young adult males (six with PWS (three with deletion and three with UPD) and three controls).

RESULTS

There was no evidence of expression of genes previously identified as paternally expressed in the PWS cell lines with either deletion or UPD. We detected no difference in expression of genes with known biallelic expression located outside the 15q11-q13 region in all cell lines studied. There was no difference in expression levels of biallelically expressed genes (for example, OCA2) from within 15q11-q13 when comparing UPD cell lines with controls. However, two genes previously identified as maternally expressed (UBE3A and ATP10C) showed a significant increase in expression in UPD cell lines compared with control and PWS deletion subjects. Several genes/transcripts (for example, GABRA5, GABRB3) had increased expression in UPD cell lines compared with deletion, but less than controls indicating paternal bias.

CONCLUSIONS

Our results suggest that differences in expression of candidate genes may contribute to phenotypic differences between PWS subjects with deletion or UPD and warrant further investigations.

Five new subjects with ring chromosome 22

Ring chromosome 22, a rare cytogenetic finding, was first described by Weleber et al. in 1968. Since then approximately 50 patients have been reported in the medical literature. We describe five previously unreported subjects with ring chromosome 22 syndrome, summarize the clinical findings of reported patients from the literature and discuss the involvement of the ring chromosome and clinical outcome. Our subjects demonstrated the prominent features of this syndrome including mental retardation, hypotonia, motor delay, lack of speech, full eyebrows, and large ears. In addition, two of our subjects had central nervous system malformations and regression. The lack of consistent physical abnormalities in our subjects further supports no consistent phenotype manifestations in this cytogenetic syndrome. The variable clinical manifestations seen in ring chromosome 22 subjects may be associated with loss of chromosome 22 sequences near the telomere or attributed to the genetic background of each subject. Similarly, recessive alleles unmasked by the deletion could also contribute to the phenotype.

Clonality studies in giant cell tumor of bone

Genetic studies including chromosome analysis, telomere reduction and telomere activity, DNA microsatellites and loss of heterozygosity (LOH) studies have been performed on giant cell tumor (GCT) of bone however whether this primary skeletal neoplasm represents a monoclonal or polyclonal proliferation is unknown. Utilizing a new assay to study the polymorphic human androgen receptor locus (HUMARA), the ratio of maternal inactive X-chromosome to the paternal inactive X (Lyon hypothesis) is determined via a methylation--specific polymerase chain reaction (PCR) technique to detect X-chromosome polymorphisms. Characterization of the genetic tumorigenesis of this unpredictable neoplasm may lend insight into its biological behavior and offer improvements in therapeutic intervention, as new information emerges regarding osteoclastic bone resorption. Seventeen female patients with giant cell tumor of bone had their DNA harvested and their X-chromosome inactivation pattern and polymorphisms determined and compared to control. A polyclonal proliferation pattern was identified in all informative samples studied.

Omphalocele in three generations with autosomal dominant transmission

We report a family with nine subjects over three generations affected with an omphalocele requiring surgical intervention within the first few days of life. Because of the vertical transmission and male to male inheritance in our family, we conclude that an autosomal dominant gene caused the omphalocele in the affected family members. The paternal great grandfather of the proband was not clinically affected but produced two children with omphaloceles with different spouses.

Decreased bone mineral density in Prader-Willi syndrome: comparison with obese subjects

Bone density, anthropometric data, and markers of bone turnover were collected on 21 subjects diagnosed with Prader-Willi syndrome (PWS) and compared with 9 subjects with obesity of unknown cause. In addition, urinary N-telopeptide levels were obtained in all subjects. N-telopeptides are the peptide fragments of type I collagen, the major bone matrix material. During periods of active bone degradation or high bone turnover, high levels of N-telopeptides are excreted in the urine. However, no significant difference was detected in the urinary N-telopeptide levels when corrected for creatinine excretion (raw or transformed data) between our subjects with obesity or PWS and the observed effect size of the between-group difference was small. Although N-telopeptide levels were higher but not significantly different in the subjects with PWS compared with obese controls, the subjects with PWS had significantly decreased total bone and spine mineral density and total bone mineral content (all P < 0.001). No differences in N-telopeptide levels or bone mineral density were observed between subjects with PWS and chromosome 15q deletion or maternal disomy. Thus, decreased bone mineral density in subjects with PWS may relate to the lack of depositing bone mineral during growth when bones are becoming more dense (e.g., during adolescence), possibly because of decreased production of sex or growth hormones and/or long-standing hypotonia. It may not be caused by loss, or active degradation, of bone matrix measurable by the methods described in this study further supporting the possible need for hormone therapy during adolescence.

Kinetic form discrimination in Prader-Willi syndrome

Discrimination of the shape of motion-produced forms generated by random elements (i.e. second-order stimuli varying in element density and temporal correlation) was tested in four groups: (1) subjects with Prader-Willi syndrome (PWS), chromosome 15q deletion subtype; (2) subjects with PWS, uniparental maternal disomy (UPD) subtype; (3) equivalent non-PWS controls; and (4) normal controls. The performance of the normal controls exceeded that of all other groups (78% correct, P < 0.009). The PWS deletion (66%) and the equivalent control groups (59%) did not differ (P < 0.95). The UPD group performed significantly less well (38%, P < 0.04) than all the other groups. The performance of the PWS deletion and equivalent control groups is consistent with other data indicating that these populations encounter difficulty meeting the processing demands posed by second-order stimuli. The inferior performance of the UPD group may be attributed to receiving two active alleles of a maternally expressed gene influencing neural development. One candidate is the ubiquitin protein ligase gene (UBE3A), which is maternally expressed only and localized to the 15q region. Other possibilities include the requirement of a paternally expressed gene, residual mosaic trisomy 15 in the brain tissue or complex interactions including specific ratios of differentially spliced gene products.

Emergence of compulsive behavior and tantrums in children with Prader-Willi syndrome

Many adults with Prader-Willi syndrome are affected by behaviors such as tantrums, skin-picking, and compulsions. The nature and extent of these problems suggest more attention be directed to their emergence in childhood. Our purpose was to investigate behavior problems in children with this syndrome and identify the age at which these behaviors emerge. Parents of children with Prader-Willi syndrome, Down syndrome, and those developing typically completed questionnaires. Children with Prader-Willi syndrome exhibited more compulsions, skin-picking, and tantrums than did the other groups. A discriminant analysis of behavior variables derived two statistically significant functions that were interpreted as developmental milestones and problematic behavior. These functions correctly predicted membership for 79% of grouped cases.

Emergence of compulsive behavior and tantrums in children with Prader-Willi syndrome

Many adults with Prader-Willi syndrome are affected by behaviors such as tantrums, skin-picking, and compulsions. The nature and extent of these problems suggest more attention be directed to their emergence in childhood. Our purpose was to investigate behavior problems in children with this syndrome and identify the age at which these behaviors emerge. Parents of children with Prader-Willi syndrome, Down syndrome, and those developing typically completed questionnaires. Children with Prader-Willi syndrome exhibited more compulsions, skin-picking, and tantrums than did the other groups. A discriminant analysis of behavior variables derived two statistically significant functions that were interpreted as developmental milestones and problematic behavior. These functions correctly predicted membership for 79% of grouped cases.

Plasma cholecystokinin levels in Prader-Willi syndrome and obese subjects

The cardinal feature of individuals with Prader-Willi syndrome (PWS) is severe hyperphagia-mediated obesity resulting from a faulty satiety mechanism. PWS is the most common genetic cause of marked obesity. Cholecystokinin (CCK) is a 33-amino-acid peptide found in high levels in the gut and brain involved in mediating the satiety response to meals. Free fatty acids (FFA) are responsible for the stimulation of CCK release after a fatty meal, and CCK and plasma FFA levels rise in tandem in normal individuals. Fasting plasma CCK levels were measured by radio-immunoassay in 33 PWS subjects with a mean age of 22.2 years +/- 8.1 years and 24 obese control subjects without a known cause of their obesity with a mean age of 28.7 years +/- 12.9 years. Consistent with previous findings, neither fasting plasma FFA levels (617.5 versus 486.8 microm/mL) or CCK levels (21.0 versus 19.1 pg/mL) were significantly different in PWS or control subjects, respectively. However, there was a significant correlation between fasting plasma FFA and CCK levels in obese subjects (r = 0. 64, P < 0.01), this correlation was completely lacking in PWS subjects (r = -0.06, P = 0.79). This difference in correlation coefficients constitutes a large effect. There were no significant effects observed for genetic subtypes (15q11-q13 deletion or maternal disomy 15), body mass index, percentage of fat, plasma levels of insulin, C-peptide, glucagon or leptin, age, or gender on CCK levels in our PWS subjects. These results suggest that differences in the peripheral CCK response to FFA levels may be a factor contributing to the altered satiety response in PWS subjects.

Specific genetic diseases at risk for sedation/anesthesia complications

We reviewed of a number of genetic diseases known or at risk for sedation or anesthesia complications. Some of these conditions are relatively common (e.g., Down's syndrome) whereas others are rare or present with multiple congenital anomalies that have an impact on health care delivery. We listed complications, recommended presedation evaluations, and included checklist items to assist the health care provider administering sedation and anesthesia. A better recognition and awareness of risk factors associated with specific genetic diseases should lessen the likelihood of complications during these procedures.

IMPLICATIONS

This article provides a brief description of potential problematic genetic disorders and associated complications that may manifest during sedation or anesthesia. Recommendations for presedation evaluation and checklist items are given that may impact on the delivery of care for these patients.

Intercontinental karyotypic differentiation of Chironomus entis Shobanov, a Holarctic member of the C. plumosus group (Diptera, Chironomidae)

Analysis of banding sequences of polytene chromosomes in Palearctic (Russian) and Nearctic (North American) Chironomus entis shows strong karyotype divergence between populations on the two continents. Four out of seven chromosomal arms in the North American C. entis karyotype are characterized by sequences found only in the Nearctic. In total, 44 banding sequences are now known for this species across the Holarctic, including 22 exclusively Palearctic, 6 Holarctic, and 16 exclusively Nearctic sequences. The degree of cytogenetic differentiation between Palearctic and Nearctic C. entis populations is an order of magnitude greater than differentiation among populations within either continent, but is only one third as great as the cytogenetic distance between the sibling species C. entis and C. plumosus. C. entis is the only sibling species of C. plumosus uncovered during cytological identification of Chironomus species from more than 50 North American lakes, indicating that the plumosus sibling-species group is much smaller in the Nearctic than in the Palearctic, where a dozen sibling species are known. Cytogenetic distance values calculated between Nearctic and Palearctic representatives of both C. entis and its sibling species C. plumosus are similar, but result from different patterns of karyotype divergence. New World C. entis is distinguished from Old World populations by the 16 uniquely Nearctic sequences, four of which occur in the homozygous state. In contrast, North American C. plumosus has fewer uniquely Nearctic sequences, and only one that occurs as a homozygote. However, four chromosomal arms in C. plumosus that are polymorphic in the Palearctic show fixation, or near fixation, of Holarctic sequences in the Nearctic C. plumosus karyotype. Thus, both the fixation of Holarctic sequences, and the occurrence or fixation of distinctly Nearctic sequences, contribute significantly to karyotype divergence. Patterns of karyotype divergence in Palearctic and Nearctic populations of different Holarctic chironomid species are discussed relative to intercontinental cytogenetic differentiation in other dipterans.

Metacarpophalangeal pattern profile analysis in Noonan syndrome

Metacarpophalangeal pattern (MCPP) analysis is an application of an anthropometric technique that provides a quantitative assessment of the amount and direction of abnormality in the hand skeleton. MCPP analysis was undertaken on 15 individuals (9 males, 6 females) with Noonan syndrome ranging in age from 0.1 to 36 years with a mean age at 11.6 years. The overall average Z score for the MCPP variables was -2.1 and the range was -2.5 (for metacarpal two) and -1.5 (for middle phalanx 5). The average hand pattern variability index, a measure of hand bone length relationships, was abnormal. A Pearsonian correlation analysis was used to assess similarity between the mean pattern and each of the 15 individual patterns. Nine (60%) of the fifteen individuals with Noonan syndrome had significant positive correlations (P < 0.05), indicating homogeneity or similarity in the hand patterns. A stepwise discriminant analysis was performed on Z score data from the individual hand bone measurements on the 15 subjects with Noonan syndrome and 41 healthy controls (24 females, 17 males; mean age = 13.1 years with age range of 9.6 to 18 years). This analysis produced a discriminant function with two MCPP variables (metacarpal 1 and middle phalanx 3) entering into the function and producing a correct classification rate of 93%. The two MCPP variables contributed to the overall difference between individuals with Noonan syndrome and the normative sample. The hand pattern variability index was outside of the normal range, indicating an abnormal MCPP with multivariate analysis. The MCPP analysis may be useful as a tool for diagnosis in screening subjects for Noonan syndrome.

Adenovirus keratitis: a role for interleukin-8

PURPOSE

Adenovirus type 19 (Ad19) infection of the human cornea results in a chronic, multifocal, subepithelial keratitis. Existing evidence suggests that early subepithelial corneal infiltrates are composed of polymorphonuclear neutrophils. In this study, the capacity of Ad19-infected human corneal stromal fibroblasts (HCFs) to produce neutrophil chemotactants (chemokines) was tested.

METHODS

HCFs grown from human donor corneas and passaged thrice were infected with a corneal isolate of Ad19 or mock-infected with virus-free media. Bioactivity of the cell supernatants was tested by a neutrophil chemotaxis assay. Supernatants were assayed by enzyme-linked immunosorbent assay for the neutrophil chemotactants interleukin-8 (IL-8) and GRO-alpha. Corneal facsimiles were generated with HCFs and collagen type I, infected with Ad19, and assayed by immunohistochemistry.

RESULTS

Ad19 infection of HCFs increased neutrophil chemotaxis from a baseline of 0.4+/-0.7 cells/high-powered field (hpf; mock-infected) to 21.8+/-2.3 cells/hpf (Ad19-infected). Chemotaxis was reduced by the addition of neutralizing antibodies against IL-8 and GRO-alpha. Infection of HCFs induced quantities of IL-8 protein 300- and 1000-fold over mock-infected controls at 4 and 24 hours, respectively (33 versus 11,813 pg/mL at 4 hours, and 57 versus 76,376 pg/mL at 24 hours, P< or = 0.001 for both). In contrast, GRO-alpha protein levels were only sevenfold higher at 24 hours postinfection (118 pg/mL in mock-infected controls versus 880 pg/mL in Ad19-infected cell supernatants). Neither chemokine was induced by infection of an immortalized human corneal epithelial cell line. Immunohistochemistry of infected corneal facsimiles demonstrated IL-8 in the extracellular matrix within 3 days after infection.

CONCLUSIONS

Production of chemokines in infected tissues facilitates an early innate immune response to infection, and in the infected corneal stroma represents an elementary defense mechanism. Interleukin-8 may play a role in the development of subepithelial infiltrates in adenovirus keratitis.

Intellectual characteristics of Prader-Willi syndrome: comparison of genetic subtypes

Advances in genetics have led to an increased understanding of the role of the genotype on behavioural functioning. The purpose of the present study was to examine differences in intellectual functioning in individuals with Prader-Willi syndrome (PWS) with a paternal 15q11-q13 deletion versus maternal uniparental disomy (UPD) of chromosome 15. Measures of intelligence and academic achievement were administered to 38 individuals with PWS (24 with deletion and 14 with UPD). The subjects with UPD had significantly higher verbal IQ scores than those with deletion (P< 0.01). The magnitude of the difference in verbal IQ was 9.1 points (69.9 versus 60.8 for UPD and deletion PWS subjects, respectively). Only 17% of subjects with the 15q11-q13 deletion had a verbal IQ > or = 70, while 50% of those with UPD had a verbal IQ > or = 70. Performance IQ scores did not differ between the two PWS genetic subtype groups. This is the first report to document the difference between verbal and performance IQ score patterns among subjects with PWS of the deletion versus the UPD subtype.

Appetitive behavior, compulsivity, and neurochemistry in Prader-Willi syndrome

Advances in genetic research have led to an increased understanding of genotype-phenotype relationships. Excessive eating and weight gain characteristic of Prader-Willi syndrome (PWS) have been the understandable focus of much of the research. The intense preoccupation with food, lack of satiation, and incessant food seeking are among the most striking features of PWS. It has become increasingly clear that the behavioral phenotype of PWS also includes symptoms similar to obsessive compulsive disorder, which in all probability interact with the incessant hunger and lack of satiation to engender the intense preoccupation and food seeking behavior that is characteristic of this disorder. Several lines of evidence suggest that genetic material on chromosome 15 may alter synthesis, release, metabolism, binding, intrinsic activity, or reuptake of specific neurotransmitters, or alter the receptor numbers and/or distribution involved in modulating feeding. Among the likely candidates are GABAnergic, serotonergic, and neuropeptidergic mechanisms. This review summarizes what is known about the appetitive behavior and compulsivity in PWS and discusses the possible mechanisms underlying these behaviors. MRDD Research Reviews 2000;6:125-130.

A 68-year-old white female with Prader-Willi syndrome

A 68-year-old white female with Prader-Willi syndrome is described. The clinical features are described and the progression of her condition is discussed and illustrated.

Appetitive behavior, compulsivity, and neurochemistry in Prader-Willi syndrome

Advances in genetic research have led to an increased understanding of genotype-phenotype relationships. Excessive eating and weight gain characteristic of Prader-Willi syndrome (PWS) have been the understandable focus of much of the research. The intense preoccupation with food, lack of satiation, and incessant food seeking are among the most striking features of PWS. It has become increasingly clear that the behavioral phenotype of PWS also includes symptoms similar to obsessive compulsive disorder, which in all probability interact with the incessant hunger and lack of satiation to engender the intense preoccupation and food seeking behavior that is characteristic of this disorder. Several lines of evidence suggest that genetic material on chromosome 15 may alter synthesis, release, metabolism, binding, intrinsic activity, or reuptake of specific neurotransmitters, or alter the receptor numbers and/or distribution involved in modulating feeding. Among the likely candidates are GABAnergic, serotonergic, and neuropeptidergic mechanisms. This review summarizes what is known about the appetitive behavior and compulsivity in PWS and discusses the possible mechanisms underlying these behaviors. MRDD Research Reviews 2000;6:125-130.

Visual capacity and Prader-Willi syndrome

PURPOSE

Prader-Willi syndrome (PWS) refers to a genetic disorder induced by an anomaly on chromosome 15 occurring with a frequency of one in 10,000 to 20,000. It is characterized by a unique set of features including infantile hypotonia, obesity in childhood, small hands and feet, hypogonadism, and mental retardation. Reported here are the results of ophthalmic examinations of persons with PWS, together with results from controls comparable in age, percentage of body fat, and intelligence. These data bear on the hypothesis that the ocular anomalies in PWS are unique to this syndrome.

METHOD

A comprehensive investigation of PWS brought children and adults to Vanderbilt University for extended testing, which included an ophthalmic examination. Genetic analysis determined unequivocally the PWS diagnosis and identified subgroups-deletion and maternal disomy. A group of persons without PWS but generally comparable in age, body composition, and intelligence served as controls.

RESULTS

Significant differences between the deletion and disomy subgroups were not found for the clinical ophthalmic measures. The incidence of anomalies in the combined PWS was similar to those reported in previous studies. A similar pattern was present in the control group except for myopia and stereopsis. An effect of genetic subgroup, however, was observed for random element stereopsis with the maternal disomy group having a greater degree of impairment.

CONCLUSION

The overall similarity between the PWS and control groups on all measures except myopia and stereopsis suggest that many of the anomalies in PWS found in prior studies are due to factors inherent in a general dysfunctional population, rather than reflective of an ocular signature unique to PWS.

Marshall-Smith syndrome: case report of a newborn male and review of the literature

Marshall-Smith syndrome is a rare congenital condition, characterized by advanced bone age, facial anomalies and relative failure to thrive. We report a newborn male with Marshall-Smith syndrome and summarize 21 previously reported cases. We report cerebellar hypoplasia in our patient, which has not been previously reported in subjects with this rare syndrome. This patient's findings broaden the phenotypic spectrum seen in Marshall-Smith syndrome.

Development and validation of a measurement system for assessment of energy expenditure and physical activity in Prader-Willi syndrome

OBJECTIVE

The morbid obesity associated with Prader-Willi syndrome (PWS) may result from either excessive energy intake or reduced energy expenditure (EE). In this report, we describe the development and validation of an Activity-Energy Measurement System (AEMS) to measure EE and physical activity components in an environment approximating free-living conditions.

RESEARCH METHODS AND PROCEDURES

The AEMS consists of a live-in, whole-room indirect calorimeter equipped with a novel force platform floor system to enable simultaneous measurements of EE, physical activity, and work efficiency during spontaneous activities and standardized exercises. Free-living physical activity and estimated free-living EE are measured using portable triaxial accelerometers individually calibrated in each subject during their stay in the AEMS.

RESULTS

Representative data from two PWS patients and two matched control (CTR) subjects displayed EE during their inactive lifestyles.

DISCUSSION

This combination of methods will allow the quantification of daily EE and its components, the amount and energy cost of physical activity, and the relationships between body composition and EE, in order to determine their roles in the development and maintenance of the morbid obesity in PWS.

Extensive analysis of mosaicism in a case of Turner syndrome: the experience of 287 cytogenetic laboratories. College of American Pathologists/American College of Medical Genetics Cytogenetics Resource Committee

OBJECTIVE

To assemble and interpret karyotype data provided as part of the College of American Pathologists/American College of Medical Genetics Cytogenetics Proficiency Testing Program.

DATA SOURCES, EXTRACTION, AND SYNTHESIS

The Cytogenetics Resource Committee requested data on all cells analyzed in a 1994 whole-blood specimen challenge. In that study, 287 participating laboratories analyzed a total of 14297 cells derived from a sample drawn from an adult donor with Turner syndrome. This individual had previously been found to have mosaicism, including cell lines with X structural anomalies along with monosomy X, making this an excellent challenge for a multicenter cytogenetic survey.

RESULTS AND CONCLUSIONS

Analysis of the data from this extensive study revealed mosaicism of up to 10 different sex chromosome complements involving the X chromosome with and without a small ring X or a derivative X chromosome. In the routine cytogenetic analysis performed by the participating laboratories, cell lines observed, in decreasing order of prevalence, included 45,X (n = 8357 cells), 46,X,r(X) (n = 3597), 46,X,der(X)t(X;X) (n = 2237), 46,XX (n = 93), 47,X,r(X),r(X) (n = 5), 47,X,der (X)t(X;X),der(X)t(X;X) (n = 3), 47,XX,r(X) (n = 2), and one observation each of 47,XX,der(X)t(X;X), 47,X,der(X)t (X;X),r(X), and 47,XXX. Our molecular cytogenetic data, as well as detailed analysis of G-banded chromosomes, suggest the nomenclature for these 2 abnormal X chromosomes as r(X)(p11.3q21.3) and der(X)t(X;X)(p11.3;q21.3), and we discuss models for the concomitant formation of these 2 entities. Both the degree of analysis and the extensive mosaicism that was discovered in this study are exceptional, and similar reported cases as well as possible mechanisms for the observed X chromosome instability are reviewed.

Analysis of imprinted genes in subjects with Prader-Willi syndrome and chromosome 15 abnormalities

PURPOSE

To determine gene expression of five imprinted genes or transcripts from the 15q11-q13 chromosome region using reverse transcription polymerase chain reaction (RT-PCR) in a relatively large survey of Prader-Willi syndrome (PWS) and control subjects with several different chromosome 15 abnormalities.

METHODS

RT-PCR was undertaken on mRNA isolated from tissue (e.g., mostly lymphoblasts) from 38 PWS and 10 control subjects. DNA primers were used for five imprinted genes or transcripts (ZNF127, SNRPN, PAR5, IPW, and PAR1) from 15q11-q13 and fibrillin, a control gene from 15q21.

RESULTS

One PWS subject with maternal disomy 15 showed weak but detectable expression of PAR1, whereas SNRPN expression was detected in two PWS subjects [one with the 15q11-q13 deletion and one with a t(15;15) karyotype and maternal disomy 15], and the remaining typical PWS subjects showed no expression of the imprinted genes or transcripts.

CONCLUSION

No obvious clinical differences were identified in those PWS subjects with weak expression of genes compared with those showing no expression. Although the reason(s) for weak expression is unknown, possible explanations include relaxation of imprinting caused by failure to reset the imprinted genes or transcripts in the maternal germ line or by postzygotic gene expression or undetected chromosome 15 mosaicism in the deletion PWS subjects. The timing, tissue source, and other factors relating to partial expression of genes that are thought to be imprinted may play a role in clinical variability and allow for a better understanding of molecular mechanisms in PWS and other abnormalities of proximal chromosome 15q.

Self-injurious behavior and Prader-Willi syndrome: behavioral forms and body locations

With few exceptions (e.g., Lesch-Nyhan syndrome), the specific nature of self-injury in relation to identified genetic syndromes associated with mental retardation is poorly understood. In the present study we surveyed the families of 62 persons with Prader-Willi syndrome to determine the prevalence, topographies, and specific body locations of self-injurious behavior. Self-injury was reported for 81% of the participants. Skin-picking was the most prevalent form, with the front of the legs and head being disproportionately targeted as preferred self-injury body sites. Individuals with the 15q11-q13 deletion injured significantly more body sites than did individuals with maternal disomy 15. Results are discussed in relation to previous self-injury body site findings and implications for the relevance of syndrome-specific behavioral phenotypes.