Differential gene expression reveals mitochondrial dysfunction in an imprinting center deletion mouse model of Prader-Willi syndrome

Characterization of Circulating Protein Profiles in Individuals with Prader-Willi Syndrome and Individuals with Non-Syndromic Obesity

Background: Prader-Willi syndrome (PWS) is a rare genetic disorder characterized by distinctive physical, cognitive, and behavioral manifestations, coupled with profound alterations in appetite regulation, leading to severe obesity and metabolic dysregulation. These clinical features arise from disruptions in neurodevelopment and neuroendocrine regulation, yet the molecular intricacies of PWS remain incompletely understood. Methods: This study aimed to comprehensively profile circulating neuromodulatory factors in the serum of 53 subjects with PWS and 34 patients with non-syndromic obesity, utilizing a proximity extension assay with the Olink Target 96 neuro-exploratory and neurology panels. The ANOVA p-values were adjusted for multiple testing using the Benjamani-Hochberg method. Protein-protein interaction networks were generated in STRING V.12. Corrplots were calculated with R4.2.2 by using the Hmisc, Performance Analytics, and Corrplot packages Results: Our investigation explored the potential genetic underpinnings of the circulating protein signature observed in PWS, revealing intricate connections between genes in the PWS critical region and the identified circulating proteins associated with impaired oxytocin, NAD metabolism, and sex-related neuromuscular impairment involving, CD38, KYNU, NPM1, NMNAT1, WFIKKN1, and GDF-8/MSTN. The downregulation of CD38 in individuals with PWS (p < 0.01) indicates dysregulation of oxytocin release, implicating pathways associated with NAD metabolism in which KYNU and NMNAT1 are involved and significantly downregulated in PWS (p < 0.01 and p < 0.05, respectively). Sex-related differences in the circulatory levels of WFIKKN1 and GDF-8/MSTN (p < 0.05) were also observed. Conclusions: This study highlights potential circulating protein biomarkers associated with impaired oxytocin, NAD metabolism, and sex-related neuromuscular impairment in PWS individuals with potential clinical implications.

Similar metabolic pathways are affected in both Congenital Myasthenic Syndrome-22 and Prader-Willi Syndrome

Loss of prolyl endopeptidase-like (PREPL) encoding a serine hydrolase with (thio)esterase activity leads to the recessive metabolic disorder Congenital Myasthenic Syndrome-22 (CMS22). It is characterized by severe neonatal hypotonia, feeding problems, growth retardation, and hyperphagia leading to rapid weight gain later in childhood. The phenotypic similarities with Prader-Willi syndrome (PWS) are striking, suggesting that similar pathways are affected. The aim of this study was to identify changes in the hypothalamic-pituitary axis in mouse models for both disorders and to examine mitochondrial function in skin fibroblasts of patients and knockout cell lines. We have demonstrated that Prepl is downregulated in the brains of neonatal PWS-IC-p/+m mice. In addition, the hypothalamic-pituitary axis is similarly affected in both Prepl-/- and PWS-IC-p/+m mice resulting in defective orexigenic signaling and growth retardation. Furthermore, we demonstrated that mitochondrial function is altered in PREPL knockout HEK293T cells and can be rescued with the supplementation of coenzyme Q10. Finally, PREPL-deficient and PWS patient skin fibroblasts display defective mitochondrial bioenergetics. The mitochondrial dysfunction in PWS fibroblasts can be rescued by overexpression of PREPL. In conclusion, we provide the first molecular parallels between CMS22 and PWS, raising the possibility that PREPL substrates might become therapeutic targets for treating both disorders.

Associations between Oxidant/Antioxidant Status and Circulating Adipokines in Non-Obese Children with Prader-Willi Syndrome

Oxidative stress is implicated in the pathophysiology of Prader-Willi syndrome (PWS), but there are no data on these disorders in non-obese children with PWS. Therefore, the presented study examined total oxidant capacity (TOC), total antioxidant capacity (TAC), the oxidative stress index (OSI), and adipokine levels in 22 non-obese children with PWS during dietary intervention and growth hormone treatment compared with 25 non-obese healthy children. Serum concentrations of TOC, TAC, nesfatin-1, leptin, hepcidin, ferroportin, and ferritin were determined using immunoenzymatic methods. We found that TOC concentrations were higher by 50% (p = 0.006) in patients with PWS than in healthy children, but no significant differences in TAC concentrations were observed between these groups. The OSI was higher in children with PWS than in the controls (p = 0.002). We found positive associations between TOC values and the percentage of the Estimated Energy Requirement, body mass index (BMI) Z-score, percentage of fat mass, and leptin, nesfatin-1, and hepcidin concentrations in patients with PWS. A positive association was also found between the OSI and nesfatin-1 levels. These observations suggest that higher daily energy intake and weight gain may be accompanied by an increasing prooxidant state in these patients. Adipokines such as leptin, nesfatin-1, or hepcidin may also play a role in the prooxidant state in non-obese children with PWS.

Omics-based approaches for the systematic profiling of mitochondrial biology

Mitochondria are essential for cellular functions such as metabolism and apoptosis. They dynamically adapt to the changing environmental demands by adjusting their protein, nucleic acid, metabolite, and lipid contents. In addition, the mitochondrial components are modulated on different levels in response to changes, including abundance, activity, and interaction. A wide range of omics-based approaches has been developed to be able to explore mitochondrial adaptation and how mitochondrial function is compromised in disease contexts. Here, we provide an overview of the omics methods that allow us to systematically investigate the different aspects of mitochondrial biology. In addition, we show examples of how these methods have provided new biological insights. The emerging use of these toolboxes provides a more comprehensive understanding of the processes underlying mitochondrial function.

Evidence for parent-of-origin effects in autism spectrum disorder: a narrative review

Autism spectrum disorder (ASD) is a heterogeneous group of early-onset neurodevelopmental disorders known to be highly heritable with a complex genetic architecture. Abnormal brain developmental trajectories that impact synaptic functioning, excitation-inhibition balance and brain connectivity are now understood to play a central role in ASD. Ongoing efforts to identify the genetic underpinnings still prove challenging, in part due to phenotypic and genetic heterogeneity.This review focuses on parent-of-origin effects (POEs), where the phenotypic effect of an allele depends on its parental origin. POEs include genomic imprinting, transgenerational effects, mitochondrial DNA, sex chromosomes and mutational transmission bias. The motivation for investigating these mechanisms in ASD has been driven by their known impacts on early brain development and brain functioning, in particular for the most well-documented POE, genomic imprinting. Moreover, imprinting is implicated in syndromes such as Angelman and Prader-Willi, which frequently share comorbid symptoms with ASD. In addition to other regions in the genome, this comprehensive review highlights the 15q11-q13 and 7q chromosomal regions as well as the mitochondrial DNA as harbouring the majority of currently identified POEs in ASD.

Dysregulated adipose tissue expansion and impaired adipogenesis in Prader-Willi syndrome children before obesity-onset

OBJECTIVE

Prader-Willi syndrome (PWS) is a rare genetic imprinting disorder resulting from the expression loss of genes on the paternally inherited chromosome 15q11-13. Early-onset life-thriving obesity and hyperphagia represent the clinical hallmarks of PWS. The noncoding RNA gene SNORD116 within the minimal PWS genetic lesion plays a critical role in the pathogenesis of the syndrome. Despite advancements in understanding the genetic basis for PWS, the pathophysiology of obesity development in PWS remains largely uncharacterized. Here, we aimed to investigate the signatures of adipose tissue development and expansion pathways and associated adipose biology in PWS children without obesity-onset at an early stage, mainly from the perspective of the adipogenesis process, and further elucidate the underlying molecular mechanisms.

METHODS

We collected inguinal (subcutaneous) white adipose tissues (ingWATs) from phase 1 PWS and healthy children with normal weight aged from 6 M to 2 Y. Adipose morphology and histological characteristics were assessed. Primary adipose stromal vascular fractions (SVFs) were isolated, cultured in vitro, and used to determine the capacity and function of white and beige adipogenic differentiation. High-throughput RNA-sequencing (RNA-seq) was performed in adipose-derived mesenchymal stem cells (AdMSCs) to analyze transcriptome signatures in PWS subjects. Transient repression of SNORD116 was conducted to evaluate its functional relevance in adipogenesis. The changes in alternative pre-mRNA splicing were investigated in PWS and SNORD116 deficient cells.

RESULTS

In phase 1 PWS children, impaired white adipose tissue (WAT) development and unusual fat expansion occurred long before obesity onset, which was characterized by the massive enlargement of adipocytes accompanied by increased apoptosis. White and beige adipogenesis programs were impaired and differentiated adipocyte functions were disturbed in PWS-derived SVFs, despite increased proliferation capacity, which were consistent with the results of RNA-seq analysis of PWS AdMSCs. We also experimentally validated disrupted beige adipogenesis in adipocytes with transient SNORD116 downregulation. The transcript and protein levels of PPARγ, the adipogenesis master regulator, were significantly lower in PWS than in control AdMSCs as well as in SNORD116 deficient AdMSCs/adipocytes than in scramble (Scr) cells, resulting in the inhibited adipogenic program. Additionally, through RNA-seq, we observed aberrant transcriptome-wide alterations in alternative RNA splicing patterns in PWS cells mediated by SNORD116 loss and specifically identified a changed PRDM16 gene splicing profile in vitro.

CONCLUSIONS

Imbalance in the WAT expansion pathway and developmental disruption are primary defects in PWS displaying aberrant adipocyte hypertrophy and impaired adipogenesis process, in which SNORD116 deficiency plays a part. Our findings suggest that dysregulated adiposity specificity existing at an early phase is a potential pathological mechanism exacerbating hyperphagic obesity onset in PWS. This mechanistic evidence on adipose biology in young PWS patients expands knowledge regarding the pathogenesis of PWS obesity and may aid in developing a new therapeutic strategy targeting disturbed adipogenesis and driving AT plasticity to combat abnormal adiposity and associated metabolic disorders for PWS patients.

Paternal preconceptional diet enriched with n-3 polyunsaturated fatty acids affects offspring brain function in mice

Recent studies demonstrate that paternal nutrition prior to conception may determine offspring development and health through epigenetic modification. This study aims to investigate the effects of paternal supplementation of n-3 polyunsaturated fatty acids (n-3 PUFAs) on the brain development and function, and associated gene imprinting in the offspring. Three to four-week-old male C57BL/6J mice (founder) were fed with an n-3 PUFA-deficient diet (n-3 D), and two n-3 PUFA supplementation diets – a normal n-3 PUFA content diet (n-3 N) and a high n-3 PUFA content diet (n-3 H) for 12 weeks. Then they were mated to 10-week-old virgin female C57BL/6J mice to generate the offspring. The results showed that paternal n-3 PUFA supplementation in preconception reduced the anxiety- and depressive-like behavior, and improved sociability, learning and memory in the offspring, along with increased synaptic number, upregulated expressions of neuron specific enolase, myelin basic protein, glial fibrillary acidic protein, brain-derived neurotrophic factor in the hippocampus and cerebral cortex, and altered expressions of genes associated with mitochondria biogenesis, fusion, fission and autophagy. Furthermore, with paternal n-3 PUFA supplementation, the expression of imprinted gene Snrpn was downregulated both in testes of the founder mice and their offspring, but upregulated in the cerebral cortex and hippocampus, with altered DNA methylation in its differentially methylated region. The data suggest that higher paternal intake of n-3 PUFAs in preconception may help to maintain optimal brain development and function in the offspring, and further raise the possibility of paternal nutritional intervention for mental health issues in subsequent generations.

Associations between prenatal exposure to perfluoroalkyl substances, hypomethylation of MEST imprinted gene and birth outcomes

Prenatal perfluoroalkyl substance (PFAS) exposure has been linked to adverse birth outcomes, but the underlying mechanism has yet to be elucidated. DNA methylation changes in mesoderm-specific transcript (MEST) imprinted gene may be a mechanism of the prenatal exposure effects of PFASs on fetal growth. The aim was to investigate the prenatal PFASs exposure effects on DNA methylation changes in MEST imprinted gene involved in fetal growth. Among 486 mother-infant pairs from the Taiwan Birth Panel Study, PFASs and DNA methylation levels at 5 CpG sites of MEST promoter region were measured in cord blood. Univariable and multivariable linear regressions were performed to estimate the associations between prenatal PFAS exposure, MEST DNA methylation levels, and child birth outcomes. Mediation analysis was performed to examine the potential pathway of MEST methylation between PFASs and birth outcomes. We found that higher prenatal perfluorooctyl sulfonate (PFOS) exposure was significantly associated with lower methylation levels at 5 CpG sites of MEST promoter region (an adjusted β range: -1.56, -2.22). Significant negative associations were also found between MEST methylation levels and child birth weight. Furthermore, the associations between PFOS and perfluorooctanoic acid (PFOA) exposure and MEST methylation levels were more profound in girls than in boys. The mediated effect of average MEST methylation level between PFOS exposure and birth weight was 18.3 (95% CI = 2.1, 40.2; p = 0.014). The direct effect of PFOS exposure to birth weight independent to average MEST methylation level was -93.2 (95% CI = -170.5, -17.8; p = 0.018). In conclusion, our results suggest that prenatal PFAS exposure, especially PFOS, is associated with lower methylation levels at MEST promoter region, which not only leverages the role of imprinted gene in ensuring the integrity of fetal growth but also provides a potential mechanism for evaluating the prenatal exposure effect.

Prader-Willi syndrome: an update on obesity and endocrine problems

Prader-Willi syndrome (PWS) is a rare complex genetic disorder that results from a lack of expression of the paternally inherited chromosome 15q11-q13. PWS is characterized by hypotonia and feeding difficulty in early infancy and development of morbid obesity aggravated by uncontrolled hyperphagia after childhood and adolescent. Dysmorphic facial features, delayed motor and language development, various degrees of cognitive impairment, and behavioral problems are common in PWS. Without early, intensive nutritional therapy along with behavioral modification, PWS patients develop severe obesity associated with type 2 diabetes, obstructive sleep apnea, right-side heart failure, and other obesity-related metabolic complications. Hypothalamic dysfunction in PWS can lead to several endocrine disorders, including short stature with growth hormone deficiency, hypothyroidism, central adrenal insufficiency, and hypogonadism. In this review, we discuss the natural history of PWS and the mechanisms of hyperphagia and obesity. We also provide an update on obesity treatments and recommendations for screening and monitoring of various endocrine problems that can occur in PWS.

Mitochondrial Dysfunction: A Common Denominator in Neurodevelopmental Disorders?

Mitochondria, the organelles classically seen as the powerhouse of the cell, are increasingly associated with a wide variety of neurodevelopmental disorders. Although individually rare, a myriad of pediatric neurogenetic disorders have been identified in the last few years, thanks to advances in clinical genetic sequencing and data analysis. As this exponential growth continues, mitochondrial dysfunction is increasingly implicated in childhood neurodevelopmental disorders, with clinical presentations ranging from syndromic autism, intellectual disability, and epileptic encephalopathies to childhood onset neurodegeneration. Here we review recent evidence demonstrating mitochondrial involvement in neurodevelopmental disorders, identify emerging mechanistic trends, and reconsider the long-standing question of the role of mitochondria in light of new evidence: causation versus mere association.

Prader-Willi Syndrome: Molecular Mechanism and Epigenetic Therapy

Prader-Willi syndrome (PWS) is an imprinted neurodevelopmental disease characterized by cognitive impairments, developmental delay, hyperphagia, obesity, and sleep abnormalities. It is caused by a lack of expression of the paternally active genes in the PWS imprinting center on chromosome 15 (15q11.2-q13). Owing to the imprinted gene regulation, the same genes in the maternal chromosome, 15q11-q13, are intact in structure but repressed at the transcriptional level because of the epigenetic mechanism. The specific molecular defect underlying PWS provides an opportunity to explore epigenetic therapy to reactivate the expression of repressed PWS genes inherited from the maternal chromosome. The purpose of this review is to summarize the main advances in the molecular study of PWS and discuss current and future perspectives on the development of CRISPR/Cas9- mediated epigenome editing in the epigenetic therapy of PWS. Twelve studies on the molecular mechanism or epigenetic therapy of PWS were included in the review. Although our understanding of the molecular basis of PWS has changed fundamentally, there has been a little progress in the epigenetic therapy of PWS that targets its underlying genetic defects.

Abnormalities of synaptic mitochondria in autism spectrum disorder and related neurodevelopmental disorders

Autism spectrum disorder (ASD) is a neurodevelopmental condition primarily characterized by an impairment of social interaction combined with the occurrence of repetitive behaviors. ASD starts in childhood and prevails across the lifespan. The variability of its clinical presentation renders early diagnosis difficult. Mutations in synaptic genes and alterations of mitochondrial functions are considered important underlying pathogenic factors, but it is obvious that we are far from a comprehensive understanding of ASD pathophysiology. At the synapse, mitochondria perform diverse functions, which are clearly not limited to their classical role as energy providers. Here, we review the current knowledge about mitochondria at the synapse and summarize the mitochondrial disturbances found in mouse models of ASD and other ASD-related neurodevelopmental disorders, like DiGeorge syndrome, Rett syndrome, Tuberous sclerosis complex, and Down syndrome.

Prader Willi syndrome: endocrine updates and new medical therapies

PURPOSE OF REVIEW

Prader Willi syndrome is characterized not only by hyperphagia frequently resulting in obesity, but also by endocrine dysfunction across a variety of axes. This article reviews the most recent literature regarding possible causes of hyperphagia and the nature of endocrinopathies seen in Prader Willi syndrome, as well as current research into possible therapies.

RECENT FINDINGS

Investigation into neurologic, metabolic and hormonal drivers of hyperphagia and obesity has revealed new insights and clarified underlying pathophysiology. Additional studies continue to elucidate the hormonal deficiencies seen in the syndrome, allowing for improvements in clinical care.

SUMMARY

The underlying causes of the hyperphagia and progressive obesity frequently seen in Prader Willi Syndrome are largely unknown and likely multifactorial. Understanding the hormonal and metabolic drivers at work in PWS, as well as the nature of other hormonal dysfunction seen in the syndrome is necessary to guide current management and future research directions.

Interaction of melatonin and Bmal1 in the regulation of PI3K/AKT pathway components and cellular survival

The circadian rhythm is driven by a master clock within the suprachiasmatic nucleus which regulates the rhythmic secretion of melatonin. Bmal1 coordinates the rhythmic expression of transcriptome and regulates biological activities, involved in cell metabolism and aging. However, the role of Bmal1 in cellular- survival, signaling, its interaction with intracellular proteins, and how melatonin regulates its expression is largely unclear. Here we observed that melatonin increases the expression of Bmal1 and both melatonin and Bmal1 increase cellular survival after oxygen glucose deprivation (OGD) while the inhibition of Bmal1 resulted in the decreased cellular survival without affecting neuroprotective effects of melatonin. By using a planar surface immunoassay for PI3K/AKT signaling pathway components, we revealed that both melatonin and Bmal1 increased phosphorylation of AKT, ERK-1/2, PDK1, mTOR, PTEN, GSK-3αβ, and p70S6K. In contrast, inhibition of Bmal1 resulted in decreased phosphorylation of these proteins, which the effect of melatonin on these signaling molecules was not affected by the absence of Bmal1. Besides, the inhibition of PI3K/AKT decreased Bmal1 expression and the effect of melatonin on Bmal1 after both OGD in vitro and focal cerebral ischemia in vivo. Our data demonstrate that melatonin controls the expression of Bmal1 via PI3K/AKT signaling, and Bmal1 plays critical roles in cellular survival via activation of survival kinases.

Preclinical Testing in Translational Animal Models of Prader-Willi Syndrome: Overview and Gap Analysis

Prader-Willi syndrome (PWS) is a rare neurodevelopmental disorder causing endocrine, musculoskeletal, and neurological dysfunction. PWS is caused by the inactivation of contiguous genes, complicating the development of targeted therapeutics. Clinical trials are now underway in PWS, with more trials to be implemented in the next few years. PWS-like endophenotypes are recapitulated in gene-targeted mice in which the function of one or more PWS genes is disrupted. These animal models can guide priorities for clinical trials or provide information about efficacy of a compound within the context of the specific disease. We now review the current status of preclinical studies that measure the effect of therapeutics on PWS-like endophenotypes. Seven categories of therapeutics (oxytocin and related compounds, K⁺-ATP channel agonists, melanocortin 4 receptor agonists, incretin mimetics and/or GLP-1 receptor agonists, cannabinoids, ghrelin agents, and Caralluma fimbriata [cactus] extract) have been tested for their effect on endophenotypes in both PWS animal models and clinical trials. Many other therapeutics have been tested in clinical trials, but not preclinical models of PWS or vice versa. Fostering dialogs among investigators performing preclinical validation of animal models and those implementing clinical studies will accelerate the discovery and translation of therapies into clinical practice in PWS.

Genotype-Phenotype Relationships and Endocrine Findings in Prader-Willi Syndrome

Prader-Willi syndrome (PWS) is a complex imprinting disorder related to genomic errors that inactivate paternally-inherited genes on chromosome 15q11-q13 with severe implications on endocrine, cognitive and neurologic systems, metabolism, and behavior. The absence of expression of one or more genes at the PWS critical region contributes to different phenotypes. There are three molecular mechanisms of occurrence: paternal deletion of the 15q11-q13 region; maternal uniparental disomy 15; or imprinting defects. Although there is a clinical diagnostic consensus criteria, DNA methylation status must be confirmed through genetic testing. The endocrine system can be the most affected in PWS, and growth hormone replacement therapy provides improvement in growth, body composition, and behavioral and physical attributes. A key feature of the syndrome is the hypothalamic dysfunction that may be the basis of several endocrine symptoms. Clinical and molecular complexity in PWS enhances the importance of genetic diagnosis in therapeutic definition and genetic counseling. So far, no single gene mutation has been described to contribute to this genetic disorder or related to any exclusive symptoms. Here we proposed to review individually disrupted genes within the PWS critical region and their reported clinical phenotypes related to the syndrome. While genes such as MKRN3, MAGEL2, NDN, or SNORD115 do not address the full spectrum of PWS symptoms and are less likely to have causal implications in PWS major clinical signs, SNORD116 has emerged as a critical, and possibly, a determinant candidate in PWS, in the recent years. Besides that, the understanding of the biology of the PWS SNORD genes is fairly low at the present. These non-coding RNAs exhibit all the hallmarks of RNA methylation guides and can be incorporated into ribonucleoprotein complexes with possible hypothalamic and endocrine functions. Also, DNA conservation between SNORD sequences across placental mammals strongly suggests that they have a functional role as RNA entities on an evolutionary basis. The broad clinical spectrum observed in PWS and the absence of a clear genotype-phenotype specific correlation imply that the numerous genes involved in the syndrome have an additive deleterious effect on different phenotypes when deficiently expressed.

Preliminary observations of mitochondrial dysfunction in Prader-Willi syndrome

Prader-Willi syndrome (PWS) is a complex multisystem disorder because of errors in genomic imprinting with severe hypotonia, decreased muscle mass, poor suckling, feeding problems and failure to thrive during infancy, growth and other hormone deficiency, childhood-onset hyperphagia, and subsequent obesity. Decreased energy expenditure in PWS is thought to contribute to reduced muscle mass and physical activity but may also relate to cellular metabolism and disturbances in mitochondrial function. We established fibroblast cell lines from six children and adults with PWS and six healthy controls for mitochondrial assays. We used Agilent Seahorse XF extracellular flux technology to determine real-time measurements of several metabolic parameters including cellular substrate utilization, Adenosine Triphosphate (ATP)-linked respiration, and mitochondrial capacity in living cells. Decreased mitochondrial function was observed in the PWS patients compared to the healthy controls with significant differences in basal respiration, maximal respiratory capacity, and ATP-linked respiration. These results suggest disturbed mitochondrial bioenergetics in PWS although the low number of studied subjects will require a larger subject population before a general consensus can be reached to identify if mitochondrial dysfunction is a contributing factor in PWS.

Transcriptome Dynamics and Potential Roles of Sox6 in the Postnatal Heart

The postnatal heart undergoes highly coordinated developmental processes culminating in the complex physiologic properties of the adult heart. The molecular mechanisms of postnatal heart development remain largely unexplored despite their important clinical implications. To gain an integrated view of the dynamic changes in gene expression during postnatal heart development at the organ level, time-series transcriptome analyses of the postnatal hearts of neonatal through adult mice (P1, P7, P14, P30, and P60) were performed using a newly developed bioinformatics pipeline. We identified functional gene clusters by principal component analysis with self-organizing map clustering which revealed organized, discrete gene expression patterns corresponding to biological functions associated with the neonatal, juvenile and adult stages of postnatal heart development. Using weighted gene co-expression network analysis with bootstrap inference for each of these functional gene clusters, highly robust hub genes were identified which likely play key roles in regulating expression of co-expressed, functionally linked genes. Additionally, motivated by the role of the transcription factor Sox6 in the functional maturation of skeletal muscle, the role of Sox6 in the postnatal maturation of cardiac muscle was investigated. Differentially expressed transcriptome analyses between Sox6 knockout (KO) and control hearts uncovered significant upregulation of genes involved in cell proliferation at postnatal day 7 (P7) in the Sox6 KO heart. This result was validated by detecting mitotically active cells in the P7 Sox6 KO heart. The current report provides a framework for the complex molecular processes of postnatal heart development, thus enabling systematic dissection of the developmental regression observed in the stressed and failing adult heart.

Oxidative Stress in Cancer-Prone Genetic Diseases in Pediatric Age: The Role of Mitochondrial Dysfunction

Oxidative stress is a distinctive sign in several genetic disorders characterized by cancer predisposition, such as Ataxia-Telangiectasia, Fanconi Anemia, Down syndrome, progeroid syndromes, Beckwith-Wiedemann syndrome, and Costello syndrome. Recent literature unveiled new molecular mechanisms linking oxidative stress to the pathogenesis of these conditions, with particular regard to mitochondrial dysfunction. Since mitochondria are one of the major sites of ROS production as well as one of the major targets of their action, this dysfunction is thought to be the cause of the prooxidant status. Deeper insight of the pathogenesis of the syndromes raises the possibility to identify new possible therapeutic targets. In particular, the use of mitochondrial-targeted agents seems to be an appropriate clinical strategy in order to improve the quality of life and the life span of the patients.

Loss of inherited genomic imprints in mice leads to severe disruption in placental lipid metabolism

INTRODUCTION

Monoallelic expression of imprinted genes is necessary for placental development and normal fetal growth. Differentially methylated domains (DMDs) largely determine the parental-specific monoallelic expression of imprinted genes. Maternally derived DNA (cytosine-5-) -methyltransferase 1o (DNMT1o) maintains DMDs during the eight-cell stage of development. DNMT1o-deficient mouse placentas have a generalized disruption of genomic imprints. Previous studies have demonstrated that DNMT1o deficiency alters placental morphology and broadens the embryonic weight distribution in late gestation. Lipids are critical for fetal growth. Thus, we assessed the impact of disrupted imprinting on placental lipids.

METHODS

Lipids were quantified from DNMT1o-deficient mouse placentas and embryos at E17.5 using a modified Folch method. Expression of select genes critical for lipid metabolism was quantified with RT-qPCR. Mitochondrial morphology was assessed by TEM and mitochondrial aconitase and cytoplasmic citrate concentrations quantified. DMD methylation was determined by EpiTYPER.

RESULTS

We found that DNMT1o deficiency is associated with increased placental triacylglycerol levels. Neither fetal triacylglycerol concentrations nor expression of select genes that mediate placental lipid transport were different from wild type. Placental triacylglycerol accumulation was associated with impaired beta-oxidation and abnormal citrate metabolism with decreased mitochondrial aconitase activity and increased cytoplasmic citrate concentrations. Loss of methylation at the MEST DMD was strongly associated with placental triacylglycerol accumulation.

DISCUSSION

A generalized disruption of genomic imprints leads to triacylglycerol accumulation and abnormal mitochondrial function. This could stem directly from a loss of methylation at a given DMD, such as MEST, or represent a consequence of abnormal placental development.

Birth seasonality in Korean Prader-Willi syndrome with chromosome 15 microdeletion

PURPOSE

Prader-Willi syndrome (PWS) is a well-known genetic disorder, and microdeletion on chromosome 15 is the most common causal mechanism. Several previous studies have suggested that various environmental factors might be related to the pathogenesis of microdeletion in PWS. In this study, we investigated birth seasonality in Korean PWS.

METHODS

A total of 211 PWS patients born from 1980 to 2014 were diagnosed by methylation polymerase chain reaction at Samsung Medical Center. Of the 211 patients, 138 were born from 2000-2013. Among them, the 74 patients of a deletion group and the 22 patients of a maternal uniparental disomy (UPD) group were compared with general populations born from 2000 using the Walter and Elwood method and cosinor analysis.

RESULTS

There was no statistical significance in seasonal variation in births of the total 211 patients with PWS (χ(2)=7.2522, P=0.2982). However, a significant difference was found in the monthly variation between PWS with the deletion group and the at-risk general population (P<0.05). In the cosinor model, the peak month of birth for PWS patients in the deletion group was January, while the nadir occurred in July, with statistical significance (amplitude=0.23, phase=1.2, low point=7.2). The UPD group showed the peak birth month in spring; however, this result was not statistically significant (χ(2)=3.39, P=0.1836).

CONCLUSION

Correlation with birth seasonality was identified in a deletion group of Korean PWS patients. Further studies are required to identify the mechanism related to seasonal effects of environmental factors on microdeletion on chromosome 15.

A novel mutation in the mitochondrial DNA cytochrome b gene (MTCYB) in a patient with Prader Willi syndrome

In recent years, it has been suggested that defects in energy metabolism may accompany Prader Willi syndrome. Mutations in the mitochondrial cytochrome b gene have been commonly associated isolated mitochondrial myopathy and exercise intolerance, rarely with multisystem disorders. The authors describe a novel mutation (mt. 15209T>C) in mitochondrial cytochrome b gene in a 2-year-old girl with Prader-Willi syndrome with a clinical history of lactic acidosis attacks, renal sodium loss, hepatopathy, progressive cerebral atrophy, and sudden death. The authors suggest that atypical clinical findings in patients with Prader-Willi syndrome should direct the physician to search for a mitochondrial disease.