Potocki-Lupski syndrome: a microduplication syndrome associated with oropharyngeal dysphagia and failure to thrive

Dental findings and intravenous sedation in a patient with Potocki-Lupski syndrome: A case report

AIMS

Potocki-Lupski syndrome (PTLS), which is caused by the partial duplication of the short arm of autosome 17, is characterized by feeding difficulties associated with muscle hypotonia and dysphagia in infancy, followed by growth retardation and low body weight in later stages. Speech and motor developmental disorders are observed in childhood, accompanied by autism spectrum disorders in several cases. Other disorders include dental and skeletal abnormalities, and associated sleep apnea. Herein, we describe the first case of dental evaluation and treatment under intravenous sedation in a patient with PTLS.

METHODS

A 13-year-old boy with PTLS and intellectual disability was referred for the treatment of dental caries. Routine intraoral examination and dental treatment were not feasible. As the patient had no muscle hypotonia, dysphagia, or severe growth delay, intraoral examination and dental treatment were successfully performed under intravenous sedation. No incidence of intraoral airway obstruction or aspiration was reported. The patient was followed-up post-operatively.

CONCLUSION

PTLS, a newly identified syndrome, is associated with cardiovascular abnormalities, dysphagia, failure to thrive, and sleep apnea, which are potential risk factors for sedation. This case report highlights the importance of facial and oral findings in determining the risks of difficulties in airway management.

Anesthesia in a Patient with Potocki-Lupski Syndrome

Introduction

Potocki–Lupski syndrome (PTLS) is a rare disease caused by the duplication of a small segment of chromosome 17 (17p11.2). The clinical presentation of this syndrome is quite variable and includes hypotonia, failure to thrive, oropharyngeal dysphagia, developmental delay, and behavioral abnormalities. In addition, congenital heart disease, sleep apnea, and mildly dysmorphic features are common and should be considered during anesthetic management. However, because of the rarity and newness of the syndrome, there are few reports on the anesthetic care of patients with PTLS. Case Report. We report a case of a 4-year-old girl diagnosed with this syndrome who underwent general anesthesia for exotropia surgery. The patient exhibited micrognathia; a mild decrease in muscle tone; and a developmental delay in motor, speech, and cognition. She had a history of swallowing incoordination and gastroesophageal reflux. No abnormalities were found on a preoperative echocardiography. A videolaryngoscope was used for tracheal intubation, and the state of neuromuscular blockade was monitored in addition to standard monitoring. Anesthesia was maintained with sevoflurane and remifentanil. The patient recovered without any adverse events.

Conclusion

As PTLS patients may have several malformations, preanesthetic evaluation is important. Preoperative echocardiography and cardiologic consultations are required. It is desirable to prepare for the risk of difficult airway and pulmonary aspiration. Postoperatively, close monitoring is needed to prevent airway compromise.

Potocki-Lupski Syndrome Dup17p11.2 in a Girl with Hypotonia and Early Behavioural Disturbances

Potocki-Lupski syndrome (PTLS) is a contiguous gene syndrome caused by duplication of chromosome 17p11.2. PTLS is characterized by hypotonia, failure to thrive, congenital anomalies (particularly of the cardiovascular system), intellectual disability, and behavioural disturbances. The patient was a full-term baby girl, 2,750 grams at birth, delivered via an uncomplicated vaginal delivery with pronounced hypotonia at birth. Nevertheless, there was failure to thrive (weight 7.6 kg; 2.8 SD). Micrognathia, epicanthal skin folds, and megalocornea were noticeable. There was a harsh continuous systolic murmur, and the ultrasound of the heart revealed a persistent arteriosus duct which was surgically closed. At the age of 18 months, the girl could not sit without support, and she could not utter simple words. The girl is often moody, angry, and aggressive. She is hyperactive and unable to establish contacts with family members. A 17p12-p11.2 microduplication was identified via MLPA. Muscle hypotonia, congenital heart malformation, failure to thrive, developmental delay, behavioural disturbances (or autism spectrum disorder), and intellectual disability are early signs of PTLS. The presence of PTLS was proven by an MLPA analysis.

Case report: Spinal anesthesia for cesarean section in a parturient with Potocki-Lupski syndrome

Background

Potocki -Lupski syndrome is an uncommon disorder caused by a micro-duplication in chromosome 17p11.2. Variable clinical manifestations bring troubles to the general and neuraxial anesthesia, including mental retardation, facial dysmorphisms, structural cardiovascular anomalies, scoliosis, and malignant hyperthermia. Until now, the anesthesia management for cesarean section in these patients has not been reported yet.

Case presentation

Here we present a 23-year-old Chinese parturient with Potocki -Lupski syndrome who underwent elective cesarean section under spinal anesthesia. She was transferred to our hospital in her 40th week of gestation. She had a history of IgA nephropathy for more than three years and was diagnosed with Potocki -Lupski syndrome (17p12p11.2 segment 3.1 Mb repeat) in the 29th week of pregnancy. Amniocentesis showed the fetus had no abnormal autosomes. Preoperative multidisciplinary consultation suggested that she should terminate the pregnancy as soon as possible. She was ASA II. Her BMI was 26.43 kg/m². Her airway evaluation was normal. Her spine could bend well and her spinal interspace could be touched clearly. We did the single spinal anesthesia at L2-3 interspace and gave 0.5% bupivacaine 1.7 ml. The absolute anesthesia level reached T8. The Apgar score for the newborn infant was 10 for 1st minute, 5th minute, and 10th minute. The vital signs were steady without using any vasoactive drugs. The patient had a good prognosis, and was subsequently discharged from hospital.

Conclusion

To date, the case may be the first reported spinal anesthesia for the parturient with Potocki -Lupski syndrome. Although its manifestations are variable, the spinal anesthesia is feasible under careful and comprehensive preoperative evaluation.

Copy number variations of chromosome 17p11.2 region in children with development delay and in fetuses with abnormal imaging findings

BACKGROUND

Deletion and duplication of the 3.7 Mb region in 17p11.2 result in two syndromes, Smith-Magenis syndrome and Potocki-Lupski syndrome, which are well-known development disorders. The purpose of this study was to determine the prevalence, genetic characteristics and clinical phenotypes of 17p11.2 deletion/duplication in Chinese children with development delay and in fetuses with potential congenital defects.

METHODS

7077 children with development delay and/or intellectual disability were screened by multiplex ligation-dependent probe amplification P245 assay. 7319 fetuses with potential congenital defects were tested using next generation sequencing technique.

RESULTS

417 of 7077 pediatric patients were determined to carry chromosome imbalance. 28 (28/7077, 0.4%) cases had imbalance at chromosome 17p11.2. Among them, 12 cases (42.9%) had heterozygous deletions and 16 cases (57.1%) had heterozygous duplications. The clinical phenotypes were variable, including neurobehavioral disorders, craniofacial/skeletal anomalies, immunologic defects, ocular problems and organ malformations. 263 of 7319 fetuses were recognized to have genomic copy number variations. Only 2 of them were found to harbor 17p11.2 imbalance. The fetus with deletion presented with ventricular septal defect and the fetus with duplication had cerebral ventricle dilation.

CONCLUSION

Our study highlights the phenotypic variability associated with 17p11.2 variations in China. The results further expand the phenotypic spectrum of SMS/PTLS and increase awareness of these disruptive mutations among clinicians.

Derivation of induced pluripotent stem cells from one child suffering Potocki-Lupski syndrome

Potocki-Lupski syndrome (PTLS; MIM 610883) is a neurodevelopmental disorder associated with a 3.7 Mb copy number variant (CNV) duplication, locating in chromosome 17p11.2. (Soler-Alfonso et al., 2011). Here, a human induced pluripotent stem cell (iPSC) line was derived from the peripheral blood mononuclear cells of a 5-year-old child suffering Potocki-Lupski syndrome. The generated iPSCs were integration-free, had the 17p11.2 3.7 Mb CNV duplication with no additional genomic alterations, a stable karyotype, expressed pluripotency stem cell markers and could differentiate towards the three germ layers in vitro. Patient's derived iPSCs are a valuable resource for in vitro modeling of 17p11.2 microduplication induced Potocki-Lupski syndrome.

Case Report: Potocki-Lupski Syndrome in Five Siblings

Potocki-Lupski syndrome (PTLS) is a rare developmental disorder resulting from the partial duplication of the short arm of chromosome 17. Affected children may have hypotonia, facial dysmorphism, or neurological abnormalities. PTLS is also frequently associated with failure to thrive due to swallowing difficulties or growth hormone deficiency. We report the first Romanian family (a mother and her five children) diagnosed with PTLS (17p11.2 microduplication). Fortunately, they present a less severe form of the disease. The neurological manifestations (speech delay, mild intellectual disability) are associated with craniofacial dysmorphism (microcephaly, micrognathia, triangular face, broad forehead, long chin, prominent ears, dolichocephaly, down slanting palpebral fissures). The diagnostic was established using a multiplex ligation-dependent probe amplification technique (MLPA) test, which detected the duplication of three regions of the 17p11.2 chromosome (RAI1, DRC3-6, LLGL1-4RA). Children with PTLS have specific phenotypes (craniofacial dysmorphism or neurological manifestations), which must draw the pediatrician's attention to a possible genetic condition. However, every child with this disease is unique and may have a different clinical presentation. A multi-disciplinary team is needed for the management of these patients. The parent's counseling and genetic advice are essential for a family with children with PTLS.

Short stature and growth hormone deficiency in a subset of patients with Potocki-Lupski syndrome: Expanding the phenotype of PTLS

Potocki-Lupski Syndrome (PTLS, MIM 610883), or duplication of chromosome 17p11.2, is a clinically recognizable condition characterized by infantile hypotonia, failure to thrive, developmental delay, intellectual disability, and congenital anomalies. Short stature, classified as greater than two standard deviations below the mean, has not previously been considered a major feature of PTLS. Retrospective chart review on a cohort of 37 individuals with PTLS was performed to investigate the etiology of short stature. Relevant data included anthropometric measurements, insulin growth factor-1 (IGF-1), insulin-like growth factor binding protein 3 (IGFBP-3), growth hormone (GH) stimulation testing, blood glucose levels, brain MRI, and bone age. Approximately 25% (9/37) of individuals with PTLS had short stature. Growth hormone deficiency (GHD) was definitively identified in two individuals. These two PTLS patients with growth hormone deficiency, as well as three others with short stature and no documented GHD, received growth hormone and obtained improvement in linear growth. One individual was identified to have pituitary abnormalities on MRI and had complications of hypoglycemia due to unrecognized GHD. Individuals with PTLS can benefit from undergoing evaluation for GHD should they present with short stature or hypoglycemia. Early identification of GHD could facilitate potential therapeutic benefit for individuals with PTLS, including linear growth, musculoskeletal, and in cases of hypoglycemia, potentially cognitive development as well.

Neurological phenotype of Potocki-Lupski syndrome

Potocki-Lupski syndrome is a condition mainly characterized by infantile hypotonia, developmental delay/intellectual disability (DD/ID), and congenital anomalies, caused by duplications of the 17p11.2 region, encompassing RAI1 gene. Its clinical presentation is extremely variable, especially for what concerns the cognitive level and the behavioral phenotype. Such aspects, as well as the dysmorphic/malformative ones, have been covered by previous studies; otherwise neurological features have never been systematically described. In order to delineate the neurological phenotype of Potocki-Lupski Syndrome, we collect an 8-patients cohort. Developmental milestones are delayed and a mild to moderate cognitive impairment is present in all patients, variably associated with features of autism spectrum disorder, behavioral disturb, and sleep disturb. Hypotonia appears a less frequent finding than what previously reported, while motor clumsiness/coordination impairment is frequent. EGG registration demonstrated a common pattern with excess of diffuse rhythmic activity in sleep phases or while the patient is falling asleep. Brain MRI did not reveal common anomalies, although unspecific white matter changes may be present. We discuss such findings and compare them to literature data, offering an overview on the neurological and cognitive-behavioral presentation of the syndrome.

Genomic study via chromosomal microarray analysis in a group of Romanian patients with obesity and developmental disability/intellectual disability

Background Obesity with developmental disability/intellectual disability (DD/ID) is the most common association in syndromic obesity. Genomic analysis studies have allowed the decipherment of disease aetiology, both in cases of syndromic obesity as well as in cases of isolated or syndromic DD/ID. However, more data are needed to further elucidate the link between the two. The aim of this pangenomic study was to use single nucleotide polymorphism (SNP) array technology to determine the copy number variant (CNV) type and frequency associated with both obesity and DD/ID. Methods Thirty-six patients were recruited from the Clinical Emergency Hospital for Children, in Cluj-Napoca, Romania during the period 2015-2017. The main inclusion criterion was a diagnosis that included both obesity and DD/ID. Genomic analysis via SNP array technology was performed. Results Out of the 36 patients, 12 (33%) presented CNVs with a higher degree of pathogenicity (A group) and 24 (66%) presented benign CNVs (B group). The SNP array results for the A group were as follows: pathogenic CNVs in 8/12 patients (67%); variants of unknown significance (VOUS) in 2/12 patients (16%); and uniparental disomy (UPD) in 2/12 patients (16%). Conclusions Some of these CNVs have already been observed in patients with both obesity and DD/ID, but the others were noticed only in DD/ID patients and have not been described until now in association with obesity.

Objective measures of sleep disturbances in children with Potocki-Lupski syndrome

Potocki-Lupski syndrome (PTLS; MIM 610883) is a neurodevelopmental disorder caused by a microduplication, a 3.7 Mb copy number variant, mapping within chromosome 17p11.2, encompassing the dosage-sensitive RAI1 gene. Whereas RAI1 triplosensitivity causes PTLS, haploinsufficiency of RAI1 due to 17p11.2 microdeletion causes the clinically distinct Smith-Magenis syndrome (SMS; MIM 182290). Most individuals with SMS have an inversion of the melatonin cycle. Subjects with PTLS have mild sleep disturbances such as sleep apnea with no melatonin abnormalities described. Sleep patterns and potential disturbances in subjects with PTLS have not been objectively characterized. We delineated sleep characteristics in 23 subjects with PTLS who underwent a polysomnogram at Texas Children's Hospital. Eleven of these subjects (58%) completed the Child's Sleep Habits Questionnaire (CSHQ). Urinary melatonin was measured in one patient and published previously. While the circadian rhythm of melatonin in PTLS appears not to be disrupted, we identified significant differences in sleep efficiency, percentage of rapid eye movement sleep, oxygen nadir, obstructive apnea hypopnea index, and periodic limb movements between prepubertal subjects with PTLS and previously published normative data. Data from the CSHQ indicate that 64% (7/11) of parents do not identify a sleep disturbance in their children. Our data indicate that younger individuals, <10 years, with PTLS have statistically significant abnormalities in five components of sleep despite lack of recognition of substantial sleep disturbances by parents. Our data support the contention that patients with PTLS should undergo clinical evaluations for sleep disordered breathing and periodic limb movement disorder, both of which are treatable conditions.

De novo and inherited TCF20 pathogenic variants are associated with intellectual disability, dysmorphic features, hypotonia, and neurological impairments with similarities to Smith-Magenis syndrome

BACKGROUND

Neurodevelopmental disorders are genetically and phenotypically heterogeneous encompassing developmental delay (DD), intellectual disability (ID), autism spectrum disorders (ASDs), structural brain abnormalities, and neurological manifestations with variants in a large number of genes (hundreds) associated. To date, a few de novo mutations potentially disrupting TCF20 function in patients with ID, ASD, and hypotonia have been reported. TCF20 encodes a transcriptional co-regulator structurally related to RAI1, the dosage-sensitive gene responsible for Smith-Magenis syndrome (deletion/haploinsufficiency) and Potocki-Lupski syndrome (duplication/triplosensitivity).

METHODS

Genome-wide analyses by exome sequencing (ES) and chromosomal microarray analysis (CMA) identified individuals with heterozygous, likely damaging, loss-of-function alleles in TCF20. We implemented further molecular and clinical analyses to determine the inheritance of the pathogenic variant alleles and studied the spectrum of phenotypes.

RESULTS

We report 25 unique inactivating single nucleotide variants/indels (1 missense, 1 canonical splice-site variant, 18 frameshift, and 5 nonsense) and 4 deletions of TCF20. The pathogenic variants were detected in 32 patients and 4 affected parents from 31 unrelated families. Among cases with available parental samples, the variants were de novo in 20 instances and inherited from 4 symptomatic parents in 5, including in one set of monozygotic twins. Two pathogenic loss-of-function variants were recurrent in unrelated families. Patients presented with a phenotype characterized by developmental delay, intellectual disability, hypotonia, variable dysmorphic features, movement disorders, and sleep disturbances.

CONCLUSIONS

TCF20 pathogenic variants are associated with a novel syndrome manifesting clinical characteristics similar to those observed in Smith-Magenis syndrome. Together with previously described cases, the clinical entity of TCF20-associated neurodevelopmental disorders (TAND) emerges from a genotype-driven perspective.

The behavioural phenotype of Potocki-Lupski syndrome: a cross-syndrome comparison

Background

Potocki-Lupski syndrome (PTLS) and Smith-Magenis syndrome (SMS) are related genomic disorders, as duplication 17p11.2 (associated with PTLS) is the reciprocal recombination product of the SMS microdeletion. While SMS has a relatively well-delineated behavioural phenotype, the behavioural profile in PTLS is less well defined, despite purported associations with autism spectrum disorder (ASD) and the suggestion that some behaviours may be diametric to those seen in SMS.

Methods

Caregivers of individuals with PTLS (N = 34; M age = 12.43, SD = 6.78) completed online behavioural questionnaires, including the Challenging Behaviour Questionnaire (CBQ), the Activity Questionnaire (TAQ), the Repetitive Behaviour Questionnaire (RBQ), the Mood, Interest and Pleasure Questionnaire-Short Form (MIPQ-S) and the Social Communication Questionnaire (SCQ), which assesses behaviours associated with ASD. Individuals with PTLS were matched on age and adaptive functioning to individuals with SMS (N = 31; M age = 13.61, SD = 6.85) and individuals with idiopathic ASD (N = 33; M age = 12.04, SD = 5.85) from an existing dataset.

Results

Individuals with PTLS and SMS were less impaired than those with idiopathic ASD on the communication and reciprocal social interaction subscales of the SCQ, but neither syndrome group differed from idiopathic ASD on the restricted, repetitive and stereotyped behaviours subscale. On the repetitive behaviour measure, individuals with PTLS and idiopathic ASD scored higher than individuals with SMS on the compulsive behaviour subscale. Rates of self-injury and property destruction were significantly lower in PTLS and idiopathic ASD than in SMS. No between-syndrome differences were found in relation to overactivity or mood; however, impulsivity was greater in SMS than in PTLS.

Conclusions

Findings suggest some overlap in the behavioural phenotype of PTLS and features of ASD symptomatology; however, the overall profile of behaviours in PTLS appears to be divergent from both idiopathic ASD and SMS. Relative to idiopathic ASD, PTLS is not characterised by communication or social interaction deficits. However, restricted and repetitive behaviours were evident in PTLS, and these may be characterised specifically by compulsive behaviours. While several behavioural differences were identified between PTLS and SMS, there was little evidence of diametric behavioural phenotypes, particularly in relation to social behaviour.

A New Patient with Potocki-Lupski Syndrome: A Literature Review

Speech delay, intellectual disability, and behavioral disturbances are the main clinical manifestations of Potocki-Lupski syndrome. Other features include infantile hypotonia, the absence of major dysmorphism, sleep disorders, and congenital anomalies, particularly of the cardiovascular system. A male patient with Potocki-Lupski syndrome is reported herein. He showed speech and borderline cognitive delay, behavioral troubles with no signs suggestive of autism, in the absence of major dysmorphism. A de novo 17p12-p11.2 duplication spanning 3.6 Mb was detected, with boundaries from 15,284,052 to 18,647,233 (hg19 assembly). At the age of 5 years, the child showed a noticeable improvement of speech skills and a moderate scholastic performance was reached. Upon analysis of the clinical manifestations of the present patient and those reported in existing literature, we found that the syndrome may present in various degrees of clinical expressivity. Affected patients may manifest symptoms ranging from mild behavioral disturbances to severe degrees of autism.

Recent progress in genetics, epigenetics and metagenomics unveils the pathophysiology of human obesity

In high-, middle- and low-income countries, the rising prevalence of obesity is the underlying cause of numerous health complications and increased mortality. Being a complex and heritable disorder, obesity results from the interplay between genetic susceptibility, epigenetics, metagenomics and the environment. Attempts at understanding the genetic basis of obesity have identified numerous genes associated with syndromic monogenic, non-syndromic monogenic, oligogenic and polygenic obesity. The genetics of leanness are also considered relevant as it mirrors some of obesity's aetiologies. In this report, we summarize ten genetically elucidated obesity syndromes, some of which are involved in ciliary functioning. We comprehensively review 11 monogenic obesity genes identified to date and their role in energy maintenance as part of the leptin-melanocortin pathway. With the emergence of genome-wide association studies over the last decade, 227 genetic variants involved in different biological pathways (central nervous system, food sensing and digestion, adipocyte differentiation, insulin signalling, lipid metabolism, muscle and liver biology, gut microbiota) have been associated with polygenic obesity. Advances in obligatory and facilitated epigenetic variation, and gene-environment interaction studies have partly accounted for the missing heritability of obesity and provided additional insight into its aetiology. The role of gut microbiota in obesity pathophysiology, as well as the 12 genes associated with lipodystrophies is discussed. Furthermore, in an attempt to improve future studies and merge the gap between research and clinical practice, we provide suggestions on how high-throughput '-omic' data can be integrated in order to get closer to the new age of personalized medicine.

RAI1 Overexpression Promotes Altered Circadian Gene Expression and Dyssomnia in Potocki-Lupski Syndrome

Retinoic acid induced 1 ( RAI1 ) encodes a dosage-sensitive gene that when haploinsufficient results in Smith-Magenis syndrome (SMS) and when overexpressed results in Potocki-Lupski syndrome (PTLS). Phenotypic and molecular evidence illustrates that haploinsufficiency of RAI1 disrupts circadian rhythm through the dysregulation of the master circadian regulator, circadian locomotor output cycles kaput ( CLOCK) , and other core circadian components, contributing to prominent sleep disturbances in SMS. However, the phenotypic and molecular characterization of sleep features in PTLS has not been elucidated. Using the Pittsburgh Sleep Quality Index (PSQI), caregivers of 15 school-aged children with PTLS reported difficulties in initiating sleep. Indeed, more than 70% of individuals manifested moderate to severe sleep latency, as defined by the PSQI. Moreover, these individuals manifested difficulties in sleep maintenance, with middle of the night and early morning awakenings. When assessing daytime sleepiness through the Epworth Sleepiness Scale, approximately 21% of the individuals manifested excessive daytime somnolence. This indicates that mild dyssomnia characterizes the majority of the sleep phenotype, with occasionally problematic daytime somnolence, a phenotype different than that expressed by individuals with SMS, where daytime sleepiness is a chronic problem. Gene expression analysis of the core circadian machinery in the hypothalamus of the PTLS mouse model ( Rai1 -Tg) found significant dysregulation of the transcriptional activators, Clock and Arntl , and the transcriptional repressors, Per1-3 and Cry1/2 , during both light and dark phases. These findings suggest a partial loss of circadian entrainment typically evoked by environmental photic cues. Examination of circadian clock gene expression in the Rai1- Tg mouse heart, liver, and kidney found unchanged expression of Clock and most of its downstream targets during both light and dark phases, suggesting an asynchronized circadian rhythm. Furthermore, examination of circadian gene expression in synchronized PTLS lymphoblasts revealed reduced transcripts of the Period ( PER1-3 ) family and normal expression of CRY1/2 . The finding that central circadian gene expression was altered while many peripheral circadian components were intact suggests a tissue-specific circadian uncoupling of the circadian machinery due to Rai1 overexpression. Overall, our results demonstrate that overexpression of RAI1 results in sleep deficiencies in individuals with PTLS due to a lack of properly regulated circadian machinery gene expression and highlight the importance of evaluating sleep concerns in individuals with PTLS.

Genetic determinants of swallowing impairment, recovery and responsiveness to treatment

Purpose of review

Here we review the latest literature and evidence in the field of genetics and determinants of swallowing and its treatments—specifically, this is a very recent concept in the field of oropharyngeal dysphagia, with only now an emerging research interest in the relationship between our genetic makeup and the effect this has on swallowing function and dysfunction. As such our review will look at preclinical, clinical and hypothesis generating research covering all aspects of the genetics of swallowing, giving new importance to the genotype-phenotype influences pertaining to dysphagia and its recovery.

Recent findings

There appear to be a number of candidate gene systems that interact with swallowing or its neurophysiology, which include brain-derived neurotrophic factor, apolipoprotein E and catechol-O-methyltransferase, that have been shown to impact on either swallowing function or the brain’s ability to respond to neurostimulation and induce plasticity. In addition, a number of genetic disorders, where dysphagia is a clinical phenomenon, have given us clues as to how multiple genes or the polygenetics of dysphagia might interact with our swallowing phenotype.

Summary

There is currently limited research in the field of genetic factors that influence (human) swallowing and oropharyngeal dysphagia, but this is an emerging science and one which, in the future, may herald a new era in precision medicine and better targeting of therapies for dysphagia based on an individual’s genetic makeup.

Cytogenomic Aberrations in Congenital Cardiovascular Malformations

Congenital cardiovascular malformations are the most common birth defects, with a complex multifactorial etiology. Genetic factors play an important role, illuminated by numerous cytogenetically visible abnormalities, as well as submicroscopic genomic imbalances affecting critical genomic regions in the affected individuals. Study of rare families with Mendelian forms, as well as emerging next-generation sequencing technologies have uncovered a multitude of genes relevant for human congenital cardiac diseases. It is clear that the complex embryology of human cardiac development, with an orchestrated interplay of transcription factors, chromatin regulators, and signal transduction pathway molecules can be easily perturbed by genomic imbalances affecting dosage-sensitive regions. This review focuses on chromosomal abnormalities contributing to congenital heart diseases and underscores several genomic disorders linked to human cardiac malformations in the last few decades.

Nonrecurrent 17p11.2p12 Rearrangement Events that Result in Two Concomitant Genomic Disorders: The PMP22-RAI1 Contiguous Gene Duplication Syndrome

The genomic duplication associated with Potocki-Lupski syndrome (PTLS) maps in close proximity to the duplication associated with Charcot-Marie-Tooth disease type 1A (CMT1A). PTLS is characterized by hypotonia, failure to thrive, reduced body weight, intellectual disability, and autistic features. CMT1A is a common autosomal dominant distal symmetric peripheral polyneuropathy. The key dosage-sensitive genes RAI1 and PMP22 are respectively associated with PTLS and CMT1A. Recurrent duplications accounting for the majority of subjects with these conditions are mediated by nonallelic homologous recombination between distinct low-copy repeat (LCR) substrates. The LCRs flanking a contiguous genomic interval encompassing both RAI1 and PMP22 do not share extensive homology; thus, duplications encompassing both loci are rare and potentially generated by a different mutational mechanism. We characterized genomic rearrangements that simultaneously duplicate PMP22 and RAI1, including nine potential complex genomic rearrangements, in 23 subjects by high-resolution array comparative genomic hybridization and breakpoint junction sequencing. Insertions and microhomologies were found at the breakpoint junctions, suggesting potential replicative mechanisms for rearrangement formation. At the breakpoint junctions of these nonrecurrent rearrangements, enrichment of repetitive DNA sequences was observed, indicating that they might predispose to genomic instability and rearrangement. Clinical evaluation revealed blended PTLS and CMT1A phenotypes with a potential earlier onset of neuropathy. Moreover, additional clinical findings might be observed due to the extra duplicated material included in the rearrangements. Our genomic analysis suggests replicative mechanisms as a predominant mechanism underlying PMP22-RAI1 contiguous gene duplications and provides further evidence supporting the role of complex genomic architecture in genomic instability.

Neurodevelopmental Disorders Associated with Abnormal Gene Dosage: Smith-Magenis and Potocki-Lupski Syndromes

Smith-Magenis syndrome (SMS) and Potocki-Lupski syndrome (PTLS) are reciprocal contiguous gene syndromes within the well-characterized 17p11.2 region. Approximately 3.6 Mb microduplication of 17p11.2, known as PTLS, represents the mechanistically predicted homologous recombination reciprocal of the SMS microdeletion, both resulting in multiple congenital anomalies. Mouse model studies have revealed that the retinoic acid-inducible 1 gene (RAI1) within the SMS and PTLS critical genomic interval is the dosage-sensitive gene responsible for the major phenotypic features in these disorders. Even though PTLS and SMS share the same genomic region, clinical manifestations and behavioral issues are distinct and in fact some mirror traits may be on opposite ends of a given phenotypic spectrum. We describe the neurobehavioral phenotypes of SMS and PTLS patients during different life phases as well as clinical guidelines for diagnosis and a multidisciplinary approach once diagnosis is confirmed by array comparative genomic hybridization or RAI1 gene sequencing. The main goal is to increase awareness of these rare disorders because an earlier diagnosis will lead to more timely developmental intervention and medical management which will improve clinical outcome.

Potocki-Lupski syndrome in conjunction with bilateral clubfoot

Potocki-Lupski syndrome (PTLS) is a rare chromosomal microduplication syndrome resulting in multiple congenital abnormalities including developmental delays, autistic features, and certain structural anomalies, with cardiovascular being the most common. The phenotype of this contiguous gene duplication syndrome is quite variable and may include musculoskeletal abnormalities. Given the infrequency and novelty of this disorder, full phenotypic characterization of PTLS has not yet been fully elucidated. We present a case of severe bilateral clubfoot in a patient with PTLS. Diagnosis was made by array-based comparative genomic hybridization and confirmed by fluorescence in-situ hybridization. Because clubfoot was also present in an apparently unaffected brother, the presence of PTLS may have acted as a modifier of the phenotype. This report highlights the complex interaction of chromosomal and familial factors that contribute to musculoskeletal birth defects.

Of mice and men: molecular genetics of congenital heart disease

Congenital heart disease (CHD) affects nearly 1 % of the population. It is a complex disease, which may be caused by multiple genetic and environmental factors. Studies in human genetics have led to the identification of more than 50 human genes, involved in isolated CHD or genetic syndromes, where CHD is part of the phenotype. Furthermore, mapping of genomic copy number variants and exome sequencing of CHD patients have led to the identification of a large number of candidate disease genes. Experiments in animal models, particularly in mice, have been used to verify human disease genes and to gain further insight into the molecular pathology behind CHD. The picture emerging from these studies suggest that genetic lesions associated with CHD affect a broad range of cellular signaling components, from ligands and receptors, across down-stream effector molecules to transcription factors and co-factors, including chromatin modifiers.

Genetic architecture of reciprocal CNVs

Copy number variants (CNVs) represent a frequent type of lesion in human genetic disorders that typically affects numerous genes simultaneously. This has raised the challenge of understanding which genes within a CNV drive clinical phenotypes. Although CNVs can arise by multiple mechanisms, a subset is driven by local genomic architecture permissive to recombination events that can lead to both deletions and duplications. Phenotypic analyses of patients with such reciprocal CNVs have revealed instances in which the phenotype is either identical or mirrored; strikingly, molecular studies have shown that such phenotypes are often driven by reciprocal dosage defects of the same transcript. Here we explore how these observations can help the dissection of CNVs and inform the genetic architecture of CNV-induced disorders.

Potocki-Lupski syndrome with teratologic dislocation of the hip: a case report

Potocki-Lupski syndrome results from the duplication of chromosome 17 band p11.2. This is the first report of a case of Potocki-Lupski syndrome with teratologic dislocation of both hips. The diagnosis was made by chromosomal analysis. The association between Potocki-Lupski syndrome and musculoskeletal disorders may help elucidate the etiology and prognosis of the syndrome.

Opposing phenotypes in mice with Smith-Magenis deletion and Potocki-Lupski duplication syndromes suggest gene dosage effects on fluid consumption behavior

A quantitative long-term fluid consumption and fluid-licking assay was performed in two mouse models with either an ∼2 Mb genomic deletion, Df(11)17, or the reciprocal duplication copy number variation (CNV), Dp(11)17, analogous to the human genomic rearrangements causing either Smith-Magenis syndrome [SMS; OMIM #182290] or Potocki-Lupski syndrome [PTLS; OMIM #610883], respectively. Both mouse strains display distinct quantitative alterations in fluid consumption compared to their wild-type littermates; several of these changes are diametrically opposing between the two chromosome engineered mouse models. Mice with duplication versus deletion showed longer versus shorter intervals between visits to the waterspout, generated more versus less licks per visit and had higher versus lower variability in the number of licks per lick-burst as compared to their respective wild-type littermates. These findings suggest that copy number variation can affect long-term fluid consumption behavior in mice. Other behavioral differences were unique for either the duplication or deletion mutants; the deletion CNV resulted in increased variability of the licking rhythm, and the duplication CNV resulted in a significant slowing of the licking rhythm. Our findings document a readily quantitated complex behavioral response that can be directly and reciprocally influenced by a gene dosage effect.

Enriched rearing improves behavioral responses of an animal model for CNV-based autistic-like traits

Potocki-Lupski syndrome (PTLS; MIM #610883), characterized by neurobehavioral abnormalities, intellectual disability and congenital anomalies, is caused by a 3.7-Mb duplication in 17p11.2. Neurobehavioral studies determined that ∼70-90% of PTLS subjects tested positive for autism or autism spectrum disorder (ASD). We previously chromosomally engineered a mouse model for PTLS (Dp(11)17/+) with a duplication of a 2-Mb genomic interval syntenic to the PTLS region and identified consistent behavioral abnormalities in this mouse model. We now report extensive phenotyping with behavioral assays established to evaluate core and associated autistic-like traits, including tests for social abnormalities, ultrasonic vocalizations, perseverative and stereotypic behaviors, anxiety, learning and memory deficits and motor defects. Alterations were identified in both core and associated ASD-like traits. Rearing this animal model in an enriched environment mitigated some, and even rescued selected, neurobehavioral abnormalities, suggesting a role for gene-environment interactions in the determination of copy number variation-mediated autism severity.

Cardiovascular findings in duplication 17p11.2 syndrome

PURPOSE

Cardiovascular abnormalities are newly recognized features of duplication 17p11.2 syndrome. In a single-center study, we evaluated subjects with duplication 17p11.2 syndrome for cardiovascular abnormalities.

METHODS

Twenty-five subjects with 17p11.2 duplication identified by chromosome analysis and/or array-based comparative genomic hybridization were enrolled in a multidisciplinary protocol. In our clinical evaluation of these subjects, we performed physical examinations, echocardiography, and electrocardiography. Three of these subjects were followed up longitudinally at our institution.

RESULTS

Cardiovascular anomalies, including structural and conduction abnormalities, were identified in 10 of 25 (40%) of subjects with duplication 17p11.2 syndrome. The most frequent abnormality was dilated aortic root (20% of total cohort). Bicommissural aortic valve (2/25), atrial (3/25) and ventricular (2/25) septal defects, and patent foramen ovale (4/25) were also observed.

CONCLUSION

Duplication 17p11.2 syndrome is associated with structural heart disease, aortopathy, and electrocardiographic abnormalities. Individuals with duplication 17p11.2 syndrome should be evaluated by electrocardiography and echocardiography at the time of diagnosis and monitored for cardiovascular disease over time. Further clinical investigation including longitudinal analysis would likely determine the age of onset and characterize the progression (if any) of vasculopathy in subjects with duplication 17p11.2 syndrome, so that specific guidelines can be established for cardiovascular management.