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Altered neural electrophysiological properties in the anterior cingulate cortex in a mouse model of Prader-Willi syndrome.

Prader-Willi syndrome (PWS) is a neurodevelopmental genetic disease associated with multiple metabolic and behavioural abnormalities converging into a distinctive clinical phenotype characterized by insatiable appetite leading to hyperphagia and eventual morbid obesity. The PWS spectrum results from deficiencies in paternally imprinted chromosome 15q11-13 region clustering around non-coding RNA multiple-repeat gene Snord116. A PWS mouse model with paternal Snord116 deletion (Snord116del) revealed multiple expected behavioural traits but failed to reproduce obesity in experimental paradigms designed to uncover homeostatic hypothalamic mechanisms of hyperphagia, while the possibility for pathologic hedonic overdrive underlying hyperphagic behaviours was not studied. In Snord116del mice, we examined functional properties of pyramidal neurons (PyNs) in the anterior cingulate cortex (ACC), the brain area commonly associated with goal-oriented and choice-outcome processing, including the value assessment of food items. We found indications of higher dendritic complexity and stronger afferent excitatory connectivity compared to controls. A strong excitatory input into Snord116del PyNs was balanced by a more hyperpolarized resting membrane potential, rendering lower soma excitability, improved signal-to-noise discrimination and stronger low-pass filtering. The enhanced excitatory network-tuning ability originating from Snord116 deficiency may explain the previously reported better performance of Snord116del over wild-type mice in working-for-food behavioural tests, whereas in humans it might entail exaggerated reward-seeking behaviour since early childhood when food is the main attractant. Our analysis of previously published genomic databases revealed candidate genes responsible for the abnormal functional neuronal phenotype caused by Snord116 deletion, including K+ and Na+ voltage-dependent ion channels, protein kinases, phosphatases and components of the mechanistic target of rapamycin (mTOR) intracellular signalling pathway. KEY POINTS: Altered biophysical characteristics and parameters of neuronal connectivity in pyramidal neurons in the anterior cingulate cortex (ACC) in Snord116 deletion mice. Alterations include augmented afferent synaptic input, altered resting state and firing properties of ACC pyramidal neurons. Our findings uncover a possible mechanistic basis for altered ACC functionality in Prader-Willi syndrome.

Animals

Rescue of imprinted genes by epigenome editing in human cellular models of Prader-Willi syndrome.

Prader-Willi syndrome (PWS) is a genomic imprinting disorder caused by the loss of function of the paternal chromosome 15q11-13, resulting in a spectrum of symptoms associated with hypothalamic dysfunction. PWS patients lack the expression of paternally expressed genes (PEGs) in the 15q11-13 locus but possess an epigenetically silenced set of these genes in the maternal allele. Thus, activation of these silenced genes can serve as a therapeutic target for PWS. Here, we leverage CRISPR-based epigenome editing system to modulate the DNA methylation status of the PWS imprinting control region (PWS-ICR) in induced pluripotent stem cells (iPSCs) derived from PWS patients. Successful demethylation in the PWS-ICR restores the PEG expression from the maternal allele and reorganizes the methylation patterns in other PWS-associated imprinted regions beyond the PWS-ICR. Remarkably, these corrected epigenomic patterns and PEG expression are maintained following the differentiation of these cells into hypothalamic organoids. Finally, the single-cell transcriptomic analysis of epigenome-edited organoids demonstrates a partial restoration of the transcriptomic dysregulation observed in PWS. This study highlights the utility of epigenome editing technology as a therapeutic approach in addressing PWS and potentially other imprinting disorders.

Prader-Willi Syndrome

15/15 translocation in Prader-Willi syndrome.

Two further cases (one previously published as D/D translocation) of 15/15 translocation in Prader-Willi syndrome are reported, which brings the total cases of this specific chromosomal anomaly in connection with this specific syndrome up to three or possibly four. It is suggested that Prader-Willi syndrome might be caused by loss of short arm material of chromosome 15.

Child

Prader-Willi syndrome as a neurogenetic model for psychosis and obsessive-compulsive disorder: A review of clinical, behavioral, and biological insights.

Prader-Willi syndrome (PWS) is a complex neurodevelopmental disorder classically defined by hyperphagia and obesity. However, its profound psychiatric phenotype offers a unique genetic framework for understanding major mental illnesses. This review positions PWS as a potentially informative biological model for psychosis and obsessive-compulsive disorder (OCD), bridging the gap between 15q11-q13 imprinting defects and neural circuit dysfunction. We synthesize evidence demonstrating that psychosis in PWS is not a uniform trait but is disproportionately linked to the maternal uniparental disomy (mUPD) subtype. This genotype-phenotype correlation suggests that overexpression of maternally imprinted genes and loss of paternal expression disrupt cortical excitatory-inhibitory balance, resembling the "schizophrenia-bipolar" genomic architecture. Furthermore, synthesized evidence characterizes the repetitive, ritualistic behaviors in PWS not merely as behavioral challenges, but as a developmentally arrested OCD-spectrum phenotype driven by distinct serotonergic-oxytocinergic imbalances and hypothalamic-limbic dysconnectivity. Mechanistic insights from preclinical models of MAGEL2, SNORD116, and NDN deficiency are integrated with clinical findings to highlight shared neurobiological substrates. Finally, we outline a roadmap for precision psychiatry in PWS, emphasizing the necessity of pharmacogenomics in antipsychotic management and the potential of targeted circuit-based therapeutics. By deconstructing the psychiatric comorbidities of PWS, we provide a framework for translating genomic architecture into mechanistic understanding and targeted treatment for complex neuropsychiatric disorders.

15q11-q13

Hypogonadism in Prader-Willi syndrome.

Sexual development was evaluated in 9 female and 2 male subjects with Prader-Willi syndrome. The process of sexual development and degree of genital development attained were found to be variable but abnormal in all subjects. Hypothalamic-pituitary-gonadal functions were evaluated by measurement of serum Luteinizing Hormone and plasma testosterone responses to stimulation by clomiphene citrate and plasma testosterone responses to stimulation by human chorionic gonadotrophin. The degree of vaginal estrogenization was variable. The testicular biopsies showed abnormalities mainly in the germinal epithelium. In agreement with previous studies, it was concluded that the abnormalities of sexual development in this syndrome are mainly due to a defect in the hypothalamic pituitary axis. Adrenal function was not found to be grossly abnormal. The 17 ketosteroid excretion values were low, probably explaining the rather sparse pubic and axillary hair observed in these patients. The urinary 17-hydroxycorticosteroid creatinine ratios were found to be elevated, probably due to decreased creatinine excretion, reflecting the muscular abnormalities of these subjects.

17-Hydroxycorticosteroids

Activation of the imprinted Prader-Willi syndrome locus by CRISPR-based epigenome editing.

Epigenome editing with DNA-targeting technologies such as CRISPR-dCas9 can be used to dissect gene regulatory mechanisms and potentially treat associated disorders. For example, Prader-Willi syndrome (PWS) results from loss of paternally expressed imprinted genes on chromosome 15q11.2-q13.3, although the maternal allele is intact but epigenetically silenced. Using CRISPR repression and activation screens in human induced pluripotent stem cells (iPSCs), we identified genomic elements that control the expression of the PWS gene SNRPN from the paternal and maternal chromosomes. We showed that either targeted transcriptional activation or DNA demethylation can activate the silenced maternal SNRPN and downstream PWS transcripts. However, these two approaches function at unique regions, preferentially activating different transcript variants and involving distinct epigenetic reprogramming mechanisms. Remarkably, transient expression of the targeted demethylase leads to stable, long-term maternal SNRPN expression in PWS iPSCs. This work uncovers targeted epigenetic manipulations to reprogram a disease-associated imprinted locus and suggests possible therapeutic interventions.

Prader-Willi Syndrome

[The Prader-Willi syndrome and 15-15 translocation].

The association of the Willi-Prader syndrome and a t(15q15q) is reported. This, in conjunction with an earlier report of this association, suggests that a gene related to the Willi-Prader syndrome may be present on chromosome 15.

Chromosome Aberrations

Human obesity and some of its experimental counterparts.

Human obesity is a manifestation of a positive energy balance. A variety of different factors influence this balance. The varieties of human obesity may be classified as follows: 1. Childhood onset with or without an increased number of adipocytes; 2. The syndromes of neuroendocrine dysfunction including hypothalamic obesity, Cushing's disease, and hyperinsulinism; 3. Dietary obesity; 4. Obesity due to physical inactivity; and 5. Genetic forms of obesity. Among the genetic form of obesity are the Laurence-Moon-Bardet-Biedl syndrome. Alstrom's syndrome, and possibly the Prader-Willi syndrome. Studies in experimental animals have increased our understanding of two of these forms of human obesity. These are: 1. Hypothalamic obesity associated with decreased sympathetic activity, hyperphagia and an increased secretion of insulin. Subdiaphragmatic vagotomy can reverse this syndrome; 2. Genetic forms of obesity inherited as recessive or dominant traits.

Adipose Tissue

[Insufficiency of penis development (micropenis). Etiological data in a series of 25 cases].

The diagnosis of micropenis was made in 25 boys aged 1 month to 16 years. This abnormality was associated with hypothalamic-pituitary deficiency in 12 boys (hypogonadotrophic hypogonadism, hypopituitary growth failure, Prader-Willi syndrome), with testicular disorders in 5 boys (anorchia, testicular dysgenesis). In the other 8 the micropenis was an isolated finding but the testicular response to HCG and the LH response to LHRH was significantly reduced (p less than 0.005). The results suggest there may be isolated gonadotrophia deficiency. The variety of conditions that are responsible for micropenis suggest that testosterone deficiency is an important causative factor. HGH may also be important as the penis may be small in HGH deficiency and growth occurs with treatment.

Adolescent

[Male sex hormones and their derivatives. Pathophysiology and therapy].

After a short review of the chemistry, biosynthesis and physiology (regulation of production and secretion, effects) of the male sex hormones, the possible disturbances of the male sex hormones, the possible disturbances of the male sex function are pathophysiologically listed and some instructive diseases, as castration, testicular feminization, Kallmann syndrome, prolactinoma and flour-bag-drawfs, are discussed. Regarding the main topic, influence of general diseases on sex hormones, the implications of the cirrhosis of the liver and the dialysis in kidney disease are listed as examples. Indications and particularly the contraindications and dangers of testosterone and anabolic steroid therapy are discussed.

Adrenal Cortex

[A jumping translocation (5p;15q), (8q;15q), and (12q;15q) (author's transl)].

Three balanced karyotypes (5p;15q), (8q;15q), and (12q;15q) were found simultaneously in a child with the Willi-Prader syndrome. The hypothesis is presented of a "jumping# translocation by affinity of telomeric and interstitial palindromes. The relationship between the Willi-Prader syndrome and a juxtacentric anomaly of the long arm of chromosome 15 is discussed.

Child, Preschool

Pubertal development in the Prader-Labhart-Willi syndrome.

The sexual maturation in the Prader-Labhart-Willi (PLW) syndrome was investigated in 14 patients, 10 females and 4 males. A wide variability in the pattern of pubertal development was found including delayed puberty in 5 patients and normal puberty in 4 patients; sexual precocity was also observed in 5 patients, true precocious puberty in one patient and incomplete sexual precocity in the form of precocious pubarche in 4 patients. In 5 patients, 3 of them with precocious pubarche, the appearance of the pubertal signs was followed by a delay or arrest in their future development. An LH-RH stimulation test was performed in 11 patients. In the 6 patients who eventually developed normal puberty, the basal levels and the peak responses of both LH and FSH were within the range of those observed in normal controls of the same pubertal stage. In 4 patients showing marked delay or arrest of puberty, the basal levels were normal or low and the responses of LH and FSH to LH-RH were blunted. Priming with repeated LH-RH stimulation in one of the male patients led to an augmented LH response, suggesting a hypothalamic hypogonadotrophism. It is concluded that the lack of uniformity in the pattern of sexual maturation in the PLW syndrome is due to a variability in the location and extent of a hypothalamic lesion, which may comprise an active process continuing beyond the perinatal period.

Adolescent