Spliceosome malfunction causes neurodevelopmental disorders with overlapping features

Pre-mRNA splicing is a highly coordinated process. While its dysregulation has been linked to neurological deficits, our understanding of the underlying molecular and cellular mechanisms remains limited. We implicated pathogenic variants in U2AF2 and PRPF19, encoding spliceosome subunits in neurodevelopmental disorders (NDDs), by identifying 46 unrelated individuals with 23 de novo U2AF2 missense variants (including 7 recurrent variants in 30 individuals) and 6 individuals with de novo PRPF19 variants. Eight U2AF2 variants dysregulated splicing of a model substrate. Neuritogenesis was reduced in human neurons differentiated from human pluripotent stem cells carrying two U2AF2 hyper-recurrent variants. Neural loss of function (LoF) of the Drosophila orthologs U2af50 and Prp19 led to lethality, abnormal mushroom body (MB) patterning, and social deficits, which were differentially rescued by wild-type and mutant U2AF2 or PRPF19. Transcriptome profiling revealed splicing substrates or effectors (including Rbfox1, a third splicing factor), which rescued MB defects in U2af50-deficient flies. Upon reanalysis of negative clinical exomes followed by data sharing, we further identified 6 patients with NDD who carried RBFOX1 missense variants which, by in vitro testing, showed LoF. Our study implicates 3 splicing factors as NDD-causative genes and establishes a genetic network with hierarchy underlying human brain development and function.

Gelation Dynamics upon Pressure-Induced Liquid-Liquid Phase Separation in a Water-Lysozyme Solution

Employing X-ray photon correlation spectroscopy, we measure the kinetics and dynamics of a pressure-induced liquid-liquid phase separation (LLPS) in a water-lysozyme solution. Scattering invariants and kinetic information provide evidence that the system reaches the phase boundary upon pressure-induced LLPS with no sign of arrest. The coarsening slows down with increasing quench depths. The g₂ functions display a two-step decay with a gradually increasing nonergodicity parameter typical for gelation. We observe fast superdiffusive (γ ≥ 3/2) and slow subdiffusive (γ < 0.6) motion associated with fast viscoelastic fluctuations of the network and a slow viscous coarsening process, respectively. The dynamics age linearly with time τ ∝ t_w, and we observe the onset of viscoelastic relaxation for deeper quenches. Our results suggest that the protein solution gels upon reaching the phase boundary.

High Incidence of Noonan Syndrome Features Including Short Stature and Pulmonic Stenosis in Patients carrying NF1 Missense Mutations Affecting p.Arg1809: Genotype-Phenotype Correlation

Neurofibromatosis type 1 (NF1) is one of the most frequent genetic disorders, affecting 1:3,000 worldwide. Identification of genotype–phenotype correlations is challenging because of the wide range clinical variability, the progressive nature of the disorder, and extreme diversity of the mutational spectrum. We report 136 individuals with a distinct phenotype carrying one of five different NF1 missense mutations affecting p.Arg1809. Patients presented with multiple café‐au‐lait macules (CALM) with or without freckling and Lisch nodules, but no externally visible plexiform neurofibromas or clear cutaneous neurofibromas were found. About 25% of the individuals had Noonan‐like features. Pulmonic stenosis and short stature were significantly more prevalent compared with classic cohorts (P < 0.0001). Developmental delays and/or learning disabilities were reported in over 50% of patients. Melanocytes cultured from a CALM in a segmental NF1‐patient showed two different somatic NF1 mutations, p.Arg1809Cys and a multi‐exon deletion, providing genetic evidence that p.Arg1809Cys is a loss‐of‐function mutation in the melanocytes and causes a pigmentary phenotype. Constitutional missense mutations at p.Arg1809 affect 1.23% of unrelated NF1 probands in the UAB cohort, therefore this specific NF1 genotype–phenotype correlation will affect counseling and management of a significant number of patients.

Absent aortic valve associated with double outlet right ventricle and aortopulmonary window: physiologic implications of a rare malformation in both the fetus and neonate

Absence of the aortic valve is a rare congenital heart defect that is detectable in the prenatal period. In this condition, functional aortic valve leaflets are absent; in their place are rudimentary, immobile noncoapting plate-like structures at the level of the annulus resulting in severe aortic regurgitation. We report the fetal diagnosis and subsequent postnatal course of an infant with the novel association of absent aortic valve, double outlet right ventricle, and aortopulmonary window. This unique combination of defects resulted in an unusual pattern of circular shunting that produced evidence of fetal heart failure. Shortly after birth, the abnormal physiology led to compromised systemic perfusion, intestinal perforation and subsequent rapid demise of the patient. Abrupt postnatal deterioration typifies the vast majority of the absent aortic valve cases found in the literature. Our patient is unique in that it is the first female reported with absent aortic valve and the first reported with an aortopulmonary window. This report demonstrates that absent aortic valve is a condition that can be diagnosed prenatally by fetal echocardiogram; the highly abnormal physiology places these patients at risk for fetal heart failure. Given the potential for clinical instability and rapid deterioration after birth, such patients should undergo rapid postnatal assessment and immediate surgical intervention when deemed appropriate.

In utero detection of retinoblastoma with fetal magnetic resonance and ultrasound: initial experience

Purpose Our aim was to evaluate and compare the ability of prenatal ultrasound (US) and fetal magnetic resonance imaging (MRI) to detect retinoblastoma lesions in utero. Methods Fetuses at risk for having bilateral retinoblastoma were enrolled in this prospective study. High-resolution US of the fetal eye was performed at 16 to 18 weeks' gestation, every 4 weeks until 32 weeks, then every 2 weeks until delivery. Fetal MRIs were performed every 8 weeks starting at 16 to 18 weeks of gestation. An exam under anesthesia (EUA) was performed postnatally, the gold standard of this study. Lesions were classified as being elevated or minimally elevated based upon their morphology. Results Of six fetuses suspected or confirmed to be at risk for developing bilateral retinoblastoma, one had tumors on her first postnatal EUA exam. A total of two minimally elevated lesions were seen by the EUA but not detected prenatally by imaging. One elevated lesion (2 mm in height) identified by postnatal EUA was initially identified by prenatal US. Fetal MRI did not detect any lesions. Conclusion Both prenatal US and fetal MRI are limited in the detection of minimally elevated retinoblastoma lesions. Prenatal US appears to be more sensitive than fetal MRI in the detection of elevated retinoblastoma lesions.

Fetal microphthalmia diagnosed by magnetic resonance imaging

We report a case of fetal microphthalmia diagnosed midtrimester by ultrasound and fetal MRI. Included is a comparison of MRI measurements of normal fetuses at similar gestational age and a review of the literature.

Aminoglycoside ototoxicity in cystic fibrosis. Evaluation by high-frequency audiometry

In this study, we sought to determine the clinical usefulness of high-frequency audiometry (8000 to 20,000 Hz) in detecting aminoglycoside-induced increases in pure-tone hearing thresholds before they are noticed in conventionally tested frequencies. We measured hearing thresholds from 250 to 20,000 Hz in 22 patients with cystic fibrosis who were treated with aminoglycosides. The audiograms were age-matched and were compared with those from 13 patients with cystic fibrosis and 38 subjects without cystic fibrosis, all of whom had never received aminoglycoside therapy. In patients with cystic fibrosis who were treated with aminoglycosides (younger than 20 years), there were statistically significant elevations only in frequencies higher than 16,000 Hz. Patients with cystic fibrosis who were treated with aminoglycosides who were 20 years and older had elevated thresholds in all frequencies tested. Patients with cystic fibrosis who were not treated with aminoglycosides did not differ statistically from controls. High-frequency audiometry may serve as a useful measure of elevation in pure-tone hearing thresholds that precede noticeable loss of auditory acuity in patients with cystic fibrosis who are receiving long-term aminoglycoside therapy.

Hermansky-Pudlak syndrome: an immunologic assessment of 15 cases

PURPOSE

The Hermansky-Pudlak syndrome is an autosomal recessive disorder consisting of the triad of oculocutaneous albinism, a storage pool platelet defect, and multisystem tissue deposition of ceroid pigment. Although the underlying metabolic defect has not been identified, secondary or associated effects on the immune system are suggested by reports of an association with disorders such as pulmonary fibrosis, granulomatous colitis, lupus, and frequent bacterial infections. We evaluated a large group of patients with the Hermansky-Pudlak syndrome to assess immune competence in this condition.

PATIENTS AND METHODS

Fifteen patients with this syndrome were studied. Control subjects included healthy volunteers in the same age range as the patients. Peripheral blood lymphocytes and neutrophils were isolated according to previously described methods. Immunofluorescent staining, flow cytometry, and cytotoxicity assays were performed. Determination of lymphocyte transformation, mixed lymphocyte response, and neutrophil function was made.

RESULTS

Immunoglobulin levels, complement, lymphocyte subsets, natural killer and lymphokine-activated cytotoxicity, mixed lymphocyte responses, and lectin-induced transformation were normal in all patients. In addition, there was no evidence for a lymphocyte proliferative response to a preparation of urinary ceroid pigment isolated from these patients. Neutrophil function, including luminol-dependent chemiluminescence, chemotaxis, and aggregation was not significantly different from control values.

CONCLUSION

The results suggest that there is no generalized defect of peripheral blood lymphocyte or neutrophil function in the Hermansky-Pudlak syndrome. We propose that future studies should examine the possibility that associated disorders arise from a defect within the monocyte-macrophage system, perhaps secondary to ceroid accumulation.

Collaborative studies program on maternal and child health in New York State, 1981-83

With the passage of the Omnibus Reconciliation Act and the establishment of the block grant system in 1981, responsibility for the direction of many public health programs shifted from Federal to State government. This shift, coupled with funding cutbacks and the constraints of the current economic status of the country, has had an impact on the ability of the service delivery network to maintain service delivery programs. In the implementation of the Maternal and Child Health (MCH) Services Block Grant, collaboration among service, research, and training programs has been emphasized as an essential component to respond to the needs of service agencies and to provide relevant field experience for public health students. A program of projects centered on joint collaboration and support is described in this paper. Two of the 13 projects implemented over a 2-year period are highlighted. In 1981, the MCH Collaborative Studies Program was established, linking Columbia University School of Public Health, the New York State Health Department, and MCH service providers in New York City in an effort to identify underserved MCH populations, assess the impact of funding cutbacks, and define new strategies for service delivery programs. Graduate research assistants are assigned to participating agencies to coordinate the activities of each project.