Two unrelated girls with intellectual disability associated with a truncating mutation in the PPM1D penultimate exon

Jansen de Vries syndrome: Report of four new patients and review of the literature

Jansen de Vries syndrome (JDVS, OMIM: 617450) is a rare neurodevelopmental disorder associated with hypotonia, behavioral features, high threshold to pain, short stature, ophthalmological abnormalities, dysmorphism and occasionally a structural cardiac condition. It is caused by truncating variants of the last and penultimate exons of PPM1D. So far, 21 patients with JVDS have been reported in the literature. Here, we describe four novel cases of JVDS and review the current literature. Notably, our patients 1, 3 and 4 do not have intellectual disability albeit they have significant developmental difficulties. Thus, the phenotype may span from a classic intellectual disability syndrome to a milder neurodevelopmental disorder. Interestingly, two of our patients have received successful growth hormone treatment. Considering the phenotype of all the known JDVS patients, a cardiological consultation is recommended, as at least 7/25 patients showed a structural cardiac defect. Episodic fever and vomiting may associate with hypoglycemia and may even mimic a metabolic disorder. We also report the first JDVS patient with a mosaic gene defect and a mild neurodevelopmental phenotype.

Jansen-de Vries syndrome: Expansion of the PPM1D clinical and phenotypic spectrum in 34 families

Jansen-de Vries syndrome (JdVS) is a neurodevelopmental condition attributed to pathogenic variants in Exons 5 and 6 of PPM1D. As the full phenotypic spectrum and natural history remain to be defined, we describe a large cohort of children and adults with JdVS. This is a retrospective cohort study of 37 individuals from 34 families with disease-causing variants in PPM1D leading to JdVS. Clinical data were provided by treating physicians and/or families. Of the 37 individuals, 27 were male and 10 female, with median age 8.75 years (range 8 months to 62 years). Four families document autosomal dominant transmission, and 32/34 probands were diagnosed via exome sequencing. The facial gestalt, including a broad forehead and broad mouth with a thin and tented upper lip, was most recognizable between 18 and 48 months of age. Common manifestations included global developmental delay (35/36, 97%), hypotonia (25/34, 74%), short stature (14/33, 42%), constipation (22/31, 71%), and cyclic vomiting (6/35, 17%). Distinctive personality traits include a hypersocial affect (21/31, 68%) and moderate-to-severe anxiety (18/28, 64%). In conclusion, JdVS is a clinically recognizable neurodevelopmental syndrome with a characteristic personality and distinctive facial features. The association of pathogenic variants in PPM1D with cyclic vomiting bears not only medical attention but also further pathogenic and mechanistic evaluation.

Analysis of Gene-Environment Interactions Related to Developmental Disorders

Various genetic and environmental factors are associated with developmental disorders (DDs). It has been suggested that interaction between genetic and environmental factors (G × E) is involved in the etiology of DDs. There are two major approaches to analyze the interaction: genome-wide and candidate gene-based approaches. In this mini-review, we demonstrate how these approaches can be applied to reveal the G × E related to DDs focusing on zebrafish and mouse models. We also discuss novel approaches to analyze the G × E associated with DDs.

Short stature leads to a diagnosis of Jansen-de Vries syndrome in two unrelated Taiwanese girls: A case report and literature review

Short stature and intellectual disability are two of the major components of many dysmorphic syndromes. Jansen-de Vries syndrome (JDVS) is a rare syndromic disorder that was discovered recently using next-generation sequencing. It is characterized by hypotonia, developmental delay, a dysmorphic face, short stature, and high pain threshold and is caused by the variants of the protein phosphatase magnesium-dependent 1D (PPM1D) gene. Here, we report the first two cases of PPM1D mutations in Taiwan; both had de novo variants in exon 6. Both presented with short stature, developmental delay, and dysmorphic faces. In addition to the characteristics listed above, syndactyly was noted in one. Genetic studies should be considered when approaching a patient with growth retardation, intellectual disability, and other major or minor dysmorphisms.

Metal-dependent Ser/Thr protein phosphatase PPM family: Evolution, structures, diseases and inhibitors

Protein phosphatases and kinases control multiple cellular events including proliferation, differentiation, and stress responses through regulating reversible protein phosphorylation, the most important post-translational modification. Members of metal-dependent protein phosphatase (PPM) family, also known as PP2C phosphatases, are Ser/Thr phosphatases that bind manganese/magnesium ions (Mn²⁺/Mg²⁺) in their active center and function as single subunit enzymes. In mammals, there are 20 isoforms of PPM phosphatases: PPM1A, PPM1B, PPM1D, PPM1E, PPM1F, PPM1G, PPM1H, PPM1J, PPM1K, PPM1L, PPM1M, PPM1N, ILKAP, PDP1, PDP2, PHLPP1, PHLPP2, PP2D1, PPTC7, and TAB1, whereas there are only 8 in yeast. Phylogenetic analysis of the DNA sequences of vertebrate PPM isoforms revealed that they can be divided into 12 different classes: PPM1A/PPM1B/PPM1N, PPM1D, PPM1E/PPM1F, PPM1G, PPM1H/PPM1J/PPM1M, PPM1K, PPM1L, ILKAP, PDP1/PDP2, PP2D1/PHLPP1/PHLPP2, TAB1, and PPTC7. PPM-family members have a conserved catalytic core region, which contains the metal-chelating residues. The different isoforms also have isoform specific regions within their catalytic core domain and terminal domains, and these regions may be involved in substrate recognition and/or functional regulation of the phosphatases. The twenty mammalian PPM phosphatases are involved in regulating diverse cellular functions, such as cell cycle control, cell differentiation, immune responses, and cell metabolism. Mutation, overexpression, or deletion of the PPM phosphatase gene results in abnormal cellular responses, which lead to various human diseases. This review focuses on the structures and biological functions of the PPM-phosphatase family and their associated diseases. The development of specific inhibitors against the PPM phosphatase family as a therapeutic strategy will also be discussed.

Blended phenotype of AP4E1 deficiency and Angelman syndrome caused by paternal isodisomy of chromosome 15

Atypical phenotype of an imprinting disease can develop with a recessive homozygous variant due to uniparental isodisomy. We present a girl with severe intellectual disability, developmental delay, distinctive facial features, and other neuropsychiatric features. Trio whole exome sequencing revealed a novel homozygous frameshift variant in AP4E1 [NM_007347.5:c.2412dupT:p.(Gly805Trpfs*8)] and uniparental isodisomy of chromosome 15 [iUPD(15)]. Single nucleotide polymorphism mapping analysis of exome data showed that the homozygous AP4E1 variant was derived from her heterozygous carrier father and unmasked by paternal iUPD(15). Brain magnetic resonance imaging confirmed the brain abnormalities characteristic of AP4 deficiency including the dilated ventricles and hypointensity in the globus pallidus in susceptibility-weighted imaging. This is the first case report of a combination of AP4E1 deficiency and Angelman syndrome. Our patient indicates that whole exome sequencing could uncover an atypical phenotype caused by multiple genetic factors including the uniparental isodisomy.

Novel truncating variant of PPM1D penultimate exon in a Chinese patient with Jansen-de Vries syndrome

Background

Jansen‐de Vries syndrome is a rare autosomal dominant neurodevelopmental disorder caused by pathogenic variants in the last and penultimate exons of the PPM1D gene. It is characterized by delayed psychomotor development, intellectual disability with speech delay, behavioral abnormalities, and dysmorphic features. Up to date, only 17 affected patients have been reported worldwide (no report in Chinese).

Methods

Here, we analyzed the clinical data and genetic test results of a Chinese patient with Jansen‐de Vries syndrome admitted in our hospital in May 2019.

Results

We report a 9‐month‐old boy carrying a pathogenic variant (c.1254_1255del, p.(V419Qfs*14)) in PPM1D exon 5, which can account for his phenotype. Most of his clinical features overlap with the reported phenotype, such as growth retardation, feeding difficulties, constipation, congenital abnormalities (such as atrial septal defect, ventricular septal defect, and patent ductus arteriosus), small hands and feet with broad forehead, low‐set posteriorly rotated ears, wide mouth with thin upper lip and pointed chin; however, he also presented with additional features like hepatomegaly and left inguinal hernia.

Conclusion

This is the first published case of Jansen‐de Vries syndrome in Chinese population, which will help us to enrich the clinical spectrum of this syndrome.