Familial Prader-Willi syndrome: case report and a literature review

Long-read sequencing for detection and subtyping of Prader-Willi and Angelman syndromes

Prader-Willi syndrome (PWS) and Angelman syndrome (AS) are imprinting disorders caused by genetic or epigenetic aberrations of 15q11.2-q13. Their clinical testing is often multitiered; diagnostic testing begins with methylation-specific multiplex ligation-dependent probe amplification or methylation-sensitive PCR and then proceeds to molecular subtyping to determine the mechanism and recurrence risk. Currently, correct classification of a proband's PWS/AS subtype often requires parental samples, a costly process for families and health systems. The use of nanopore sequencing for molecular diagnosis of PWS and AS has been explored by Yamada et al; however, to confirm heterodisomy parental data were still required. Here, we investigate genome-wide nanopore sequencing in a larger cohort of PWS (18) and AS (6) as a singular test to detect the molecular subtype, without parental data. We accurately subtyped these cases including uniparental heterodisomy, mixed iso-/heterodisomy, type 1 and 2 deletions, microdeletion and UBE3A indels. One PWS case with a previously unresolved diagnosis subtyped as maternal isodisomy. This work highlights the application of long-read sequencing and other imprinted regions outside of the PWS/AS critical region to resolve the molecular diagnosis and subtyping of PWS and AS without parental data. The work also outlines an approach to generically detect heterodisomy through the interrogation of distant imprinted regions.

Three siblings with Prader-Willi syndrome caused by imprinting center microdeletions and review

Prader-Willi syndrome (PWS) is a complex genetic imprinting disorder characterized by childhood obesity, short stature, hypogonadism/hypogenitalism, hypotonia, cognitive impairment, and behavioral problems. Usually PWS occurs sporadically due to the loss of paternally expressed genes on chromosome 15 with the majority of individuals having the 15q11-q13 region deleted. Examples of familial PWS have been reported but rarely. To date 13 families have been reported with more than one child with PWS and without a 15q11-q13 deletion secondary to a chromosome 15 translocation, inversion, or uniparental maternal disomy 15. Ten of those 13 families were shown to carry microdeletions in the PWS imprinting center. The microdeletions were found to be of paternal origin in nine of the ten cases in which family studies were carried out. Using a variety of techniques, the microdeletions were identified in regions within the complex SNRPN gene locus encompassing the PWS imprinting center. Here, we report the clinical and genetic findings in three adult siblings with PWS caused by a microdeletion in the chromosome 15 imprinting center inherited from an unaffected father that controls the activity of genes in the 15q11-q13 region and summarize the 13 reported cases in the literature.

Sleep and neurocognitive functioning in children with eczema

Sleep disruption in childhood is associated with clearly defined deficits in neurocognition and behaviour. Childhood eczema is also a potent cause of sleep disruption though it is unknown whether it too results in neurocognitive deficits. To test this hypothesis, neurocognitive (WISC-IV), parental-reported sleep quality (Sleep Disturbance Scale of Children (SDSC)) and overnight polysomnographic (PSG) data were collected in 21 children with eczema and 20 healthy controls (age range 6-16 years). Children with eczema had worse sleep quality on both PSG (notably increased nocturnal wakefulness, a higher number of stage shifts and a longer latency to REM onset) and parental report. In addition, they demonstrated significant neurocognitive deficits (especially verbal comprehension, perceptual reasoning and to a lesser extent working memory) with a composite Full Scale IQ 16 points lower than controls. Parental reported sleep problems but not PSG parameters were correlated with reduced neurocognitive performance. However, hierarchical regression analyses revealed that eczema status was predictive while sleep fragmentation (parental or PSG) was not predictive of neurocognitive performance. As this is the first study to systematically examine neurocognitive functioning in children with eczema and given the finding of significant deficits it merits replication especially given the prevalence of the condition. The unanswered question is whether these cognitive deficits normalise with effective eczema treatment and if this is mediated by improvements in sleep architecture.

The clinical spectrum of lymphatic disease

Lymphatic disease is quite prevalent, and often not well clinically characterized. Beyond lymphedema, there is a broad array of human disease that directly or indirectly alters lymphatic structure and function. The symptomatic and objective presentation of these patients can be quite diverse. In this review, we have attempted to provide a systematic overview of the subjective and objective spectrum of lymphatic disease, with consideration of all of the categories of disease that primarily or secondarily impair the functional integrity of the lymphatic system. Lymphedema is discussed, along with chromosomal disorders, lymphangioma, infectious diseases, lymphangioleiomyomatosis, lipedema, heritable genetic disorders, complex vascular malformations, protein-losing enteropathy, and intestinal lymphangiectasia.

Genomic imprinting and imprinting defects in humans

In placental mammals some 100-200 genes are expressed only from the paternal or the maternal allele. This peculiar expression pattern is the result of genomic imprinting, an epigenetic process by which the male and the female germ line confer a parent-of-origin specific mark (imprint) on certain chromosomal regions. The size of imprinted regions ranges from several kilobases to several megabases. The process of genomic imprinting is controlled by cis-acting imprinting centers (IC) and trans-acting factors. IC mutations affect the establishment or maintenance of genomic imprints and hence the expression of all imprinted genes controlled by this IC. Imprinting defects play a causal role in several recognizable syndromes.

GABA(A) receptor alpha5 subunit as a candidate gene for autism and bipolar disorder: a proposed endophenotype with parent-of-origin and gain-of-function features,with or without oculocutaneous albinism

Our earlier family history studies of individuals with autism found a high incidence of major affective disorder, especially bipolar disorder, and unusual talents or intellectual abilities among family members. We now describe a subgroup of such families, selected from a large clinical experience, illustrating specific features of major affective disorder, special talents or intellectual ability, and familial patterns of trait transmission, with the additional feature of oculocutaneous albinism in some cases. These observations, suggesting parent-of-origin and gain-of-function effects, considered together with recent genetic findings in the literature, suggest a genetic hypothesis possibly unifying disparate observations found in families of individuals with autism.