Mutations in DDX3X Are a Common Cause of Unexplained Intellectual Disability with Gender-Specific Effects on Wnt Signaling

Intellectual disability (ID) affects approximately 1%-3% of humans with a gender bias toward males. Previous studies have identified mutations in more than 100 genes on the X chromosome in males with ID, but there is less evidence for de novo mutations on the X chromosome causing ID in females. In this study we present 35 unique deleterious de novo mutations in DDX3X identified by whole exome sequencing in 38 females with ID and various other features including hypotonia, movement disorders, behavior problems, corpus callosum hypoplasia, and epilepsy. Based on our findings, mutations in DDX3X are one of the more common causes of ID, accounting for 1%-3% of unexplained ID in females. Although no de novo DDX3X mutations were identified in males, we present three families with segregating missense mutations in DDX3X, suggestive of an X-linked recessive inheritance pattern. In these families, all males with the DDX3X variant had ID, whereas carrier females were unaffected. To explore the pathogenic mechanisms accounting for the differences in disease transmission and phenotype between affected females and affected males with DDX3X missense variants, we used canonical Wnt defects in zebrafish as a surrogate measure of DDX3X function in vivo. We demonstrate a consistent loss-of-function effect of all tested de novo mutations on the Wnt pathway, and we further show a differential effect by gender. The differential activity possibly reflects a dose-dependent effect of DDX3X expression in the context of functional mosaic females versus one-copy males, which reflects the complex biological nature of DDX3X mutations.

De novo mutations in PLXND1 and REV3L cause Möbius syndrome

Möbius syndrome (MBS) is a neurological disorder that is characterized by paralysis of the facial nerves and variable other congenital anomalies. The aetiology of this syndrome has been enigmatic since the initial descriptions by von Graefe in 1880 and by Möbius in 1888, and it has been debated for decades whether MBS has a genetic or a non-genetic aetiology. Here, we report de novo mutations affecting two genes, PLXND1 and REV3L in MBS patients. PLXND1 and REV3L represent totally unrelated pathways involved in hindbrain development: neural migration and DNA translesion synthesis, essential for the replication of endogenously damaged DNA, respectively. Interestingly, analysis of Plxnd1 and Rev3l mutant mice shows that disruption of these separate pathways converge at the facial branchiomotor nucleus, affecting either motoneuron migration or proliferation. The finding that PLXND1 and REV3L mutations are responsible for a proportion of MBS patients suggests that de novo mutations in other genes might account for other MBS patients.

lt has been debated for decades if there is a genetic aetiology underlying Möbius syndrome, a neurological disorder characterized by facial paralysis. Here Tomas-Roca et al. use exome sequencing and identify de novo mutations in PLXND1 and REV3L, representing converging pathways in hindbrain development.

SINDROMUL SMITH-LEMLI-OPITZ. PREZENTARE DE CAZ

Sindromul Smith-Lemli-Opitz (SSLO) reprezintă o afecţiune cu transmitere autozomal-recesivă caracterizată prin multiple anomalii şi care se datorează anomaliilor în sinteza colesterolului. Autorii prezintă particularităţile diagnostice şi terapeutice la un sugar cu ambiguitate genitală.

SMITH-LEMLI-OPITZ SYNDROME. CASE REPORT

Smith-Lemli-Opitz syndrome (SLOS) is an autosomal-recessive inherited disease characterized by multiple anomalies secondary to cholesterol synthesis impairment. The authors present diagnosis peculiarities and limitation of treatment options in a 5-weeks old infant with ambiguous genitalia.

Clinical and biochemical features guiding the diagnostics in neurometabolic cutis laxa

Patients with cutis laxa (CL) have wrinkled, sagging skin with decreased elasticity. Skin symptoms are associated with variable systemic involvement. The most common, genetically highly heterogeneous form of autosomal recessive CL, ARCL2, is frequently associated with variable metabolic and neurological symptoms. Progeroid symptoms, dysmorphic features, hypotonia and psychomotor retardation are highly overlapping in the early phase of these disorders. This makes the genetic diagnosis often challenging. In search for discriminatory symptoms, we prospectively evaluated clinical, neurologic, metabolic and genetic features in our patient cohort referred for suspected ARCL. From a cohort of 26 children, we confirmed mutations in genes associated with ARCL in 16 children (14 probands), including 12 novel mutations. Abnormal glycosylation and gyration abnormalities were mostly, but not always associated with ATP6V0A2 mutations. Epilepsy was most common in ATP6V0A2 defects. Corpus callosum dysgenesis was associated with PYCR1 and ALDH18A1 mutations. Dystonic posturing was discriminatory for PYCR1 and ALDH18A1 defects. Metabolic markers of mitochondrial dysfunction were found in one patient with PYCR1 mutations. So far unreported white matter abnormalities were found associated with GORAB and RIN2 mutations. We describe a large cohort of CL patients with neurologic involvement. Migration defects and corpus callosum hypoplasia were not always diagnostic for a specific genetic defect in CL. All patients with ATP6V0A2 defects had abnormal glycosylation. To conclude, central nervous system and metabolic abnormalities were discriminatory in this genetically heterogeneous group, although not always diagnostic for a certain genetic defect in CL.

Notizen: Cross Polarization in Electron Nuclear Double Resonance by Satisfying the Hartmann-Hahn Condition

The polarization of electronic spins S is transferred to nuclear spins I by cross relaxation in an electron nuclear double resonance experiment. The cross relaxation becomes very efficient with a time constant Tcr of about 0.5 microseconds if the Hartmann-Hahn condition is satisfied for electronic spins S spin-lock ed to the microwave field B1,S in the rotating frame and for proton spins / in the static magnetic field B0.

Leopard Syndrome. Familial cases

LEOPARD syndrome is a complex disorder characterized by multiple dysmorphogenetic features. Both syndromes LEOPARD and Noonan are caused by different mutations in the same gene (PTPN11). Authors emphasize diagnosis peculiarities in two related cases with facial dysmorphism. Index case is represented by a 10 year-old boy admitted for evaluation because of cephalofacial dysmorphism associated with mental disabilities. Family history: non-consanguineous parents; the father’s case and his sister with face dysmorphism. Clinical exam: short stature, impaired nutritional status, axillary freckles, widespread café-au-lait spots, face dysmorphism, webbed neck, skeletal anomalies and mental retardation. Blood investigations and cardiac ultrasonography: no anomalies. Differential diagnosis includes Noonan syndrome, Greig syndrome, type 1 neurofibromatosis, Albright syndrome. Regarding patient genetic evaluation: normal karyotype; DNA sequencing revealed mutation in PTPN11 gene suggestive for LEOPARD syndrome. Authors also found same mutation for probant’s father. Conclusions. Authors described two cases with dysmorphic skull, skeletal anomalies, skin pigmentation, mental disabilities and short stature, justifying further genetic evaluation that revealed a very rare disorder.

Sindromul Leopard. Cazuri familiale

Sindromul LEOPARD este o afecţiune ce include multiple anomalii dismorfogenetice. Sindromul LEOPARD, ca şi sindromul Noonan, este determinat de mutaţii ale genei PTPN11. Autorii menţionează particularităţile diagnostice la 2 cazuri înrudite cu dismorfism facial. Cazul index este reprezentat de băiat de 10 ani evaluat pentru dismorfism cranio-facial asociat cu retard mental. Antecedente heredo-colaterale: fără consangvinitate; tatăl pacientului şi soră cu dismorfism facial. Examenul clinic: retard staturo-ponderal, pistrui axilari, pete café-au-lait diseminate, dismorfism facial, pterigium coli, anomalii scheletice, retard mental. Investigaţiile sangvine şi eco-cardiografia: fără modificări. Pentru diagnosticul diferenţial s-au considerat sindroamele Noonan, Greig, neurofibromatoza tip 1, sindromul Mc Cune-Albright. Evaluarea genetică: cariotip normal; secvenţierea genei PTPN11 a relevat mutaţia ce confirmă sindromul LEOPARD. Analiza genetică a relevat aceeaşi mutaţie la tatăl pacientului. Concluzii. Autorii au descris 2 cazuri familiale cu craniu dismorf, anomalii scheletice, pigmentaţia pielii, dizabilităţi mentale şi statură mică, justificând evaluarea genetică care a identificat o afecţiune genetică foarte rară.