Abstract PPFIA3 encodes the Protein-Tyrosine Phosphatase, Receptor-Type, F Polypeptide-Interacting Protein Alpha-3 (PPFIA3), which is a member of the LAR protein-tyrosine phosphatase-interacting protein (liprin) family involved in synaptic vesicle transport and presynaptic active zone assembly. The protein structure and function are well conserved in both invertebrates and vertebrates, but human diseases related to PPFIA3 dysfunction are not yet known. Here, we report 14 individuals with rare mono-allelic PPFIA3 variants presenting with features including developmental delay, intellectual disability, hypotonia, autism, and epilepsy. To determine the pathogenicity of PPFIA3 variants in vivo , we generated transgenic fruit flies expressing either human PPFIA3 wildtype (WT) or variant protein using GAL4-UAS targeted gene expression systems. Ubiquitous expression with Actin-GAL4 showed that the PPFIA3 variants had variable penetrance of pupal lethality, eclosion defects, and anatomical leg defects. Neuronal expression with elav-GAL4 showed that the PPFIA3 variants had seizure-like behaviors, motor defects, and bouton loss at the 3 rd instar larval neuromuscular junction (NMJ). Altogether, in the fly overexpression assays, we found that the PPFIA3 variants in the N-terminal coiled coil domain exhibited stronger phenotypes compared to those in the C-terminal region. In the loss-of-function fly assay, we show that the homozygous loss of fly Liprin- α leads to embryonic lethality. This lethality is partially rescued by the expression of human PPFIA3 WT, suggesting human PPFIA3 protein function is partially conserved in the fly. However, the PPFIA3 variants failed to rescue lethality. Altogether, the human and fruit fly data reveal that the rare PPFIA3 variants are dominant negative loss-of-function alleles that perturb multiple developmental processes and synapse formation.
ABSTRACT Haploinsufficiency of SF3B2 is associated with craniofacial microsomia, characterized by mandibular hypoplasia and microtia, often with preauricular tags or pits, epibulbar dermoids, and cleft palate. In addition, extracraniofacial anomalies may be present, such as skeletal, cardiac renal, and abnormalities of the central nervous system. Variants have been either de novo or inherited, and both inter‐ and intrafamilial variability has been observed. Here we describe a patient referred for exome sequencing for a complex congenital heart defect and Hirschsprung disease found by exome sequencing to be heterozygous for a loss of function variant, c.945dup (p.Val316SerfsTer5), in SF3B 2. This variant was inherited from a parent with an isolated cardiac defect. Interestingly, neither have the defining craniofacial features or other dysmorphisms. This report further illustrates the degree of phenotypic variability seen in SF3B2‐ related disease and expands the spectrum to include Hirschsprung disease.
Abstract ATP1A3 encodes the α3 subunit of the sodium-potassium ATPase, one of two isoforms responsible for powering electrochemical gradients in neurons. Heterozygous pathogenic ATP1A3 variants produce several distinct neurological syndromes, yet the molecular basis for phenotypic variability is unclear. We report a novel recurrent variant, ATP1A3(NM_152296.5):c.2324C>T; p.(Pro775Leu), in nine individuals associated with the primary clinical features of progressive or non-progressive spasticity and developmental delay/intellectual disability. No patients fulfil diagnostic criteria for ATP1A3-associated syndromes, including alternating hemiplegia of childhood, rapid-onset dystonia-parkinsonism or cerebellar ataxia-areflexia-pes cavus-optic atrophy-sensorineural hearing loss (CAPOS), and none were suspected of having an ATP1A3-related disorder. Uniquely among known ATP1A3 variants, P775L causes leakage of sodium ions and protons into the cell, associated with impaired sodium binding/occlusion kinetics favouring states with fewer bound ions. These phenotypic and electrophysiologic studies demonstrate that ATP1A3:c.2324C>T; p.(Pro775Leu) results in mild ATP1A3-related phenotypes resembling complex hereditary spastic paraplegia or idiopathic spastic cerebral palsy. Cation leak provides a molecular explanation for this genotype-phenotype correlation, adding another mechanism to further explain phenotypic variability and highlighting the importance of biophysical properties beyond ion transport rate in ion transport diseases.
Abstract Developmental and epileptic encephalopathies (DEEs) are a heterogenous group of epilepsies in which altered brain development leads to developmental delay and seizures, with the epileptic activity further negatively impacting neurodevelopment. Identifying the underlying cause of DEEs is essential for progress toward precision therapies. Here we describe a group of individuals with biallelic variants in DENND5A and determine that variant type is correlated with disease severity. We demonstrate that DENND5A interacts with MUPP1 and PALS1, components of the Crumbs apical polarity complex, which is required for both neural progenitor cell identity and the ability of these stem cells to divide symmetrically. Induced pluripotent stem cells lacking DENND5A fail to undergo symmetric cell division during neural induction and have an inherent propensity to differentiate into neurons, and transgenic DENND5A mice, with phenotypes like the human syndrome, have an increased number of neurons in the adult subventricular zone. Disruption of symmetric cell division following loss of DENND5A results from misalignment of the mitotic spindle in apical neural progenitors. A subset of DENND5A is localized to centrosomes, which define the spindle poles during mitosis. Cells lacking DENND5A orient away from the proliferative apical domain surrounding the ventricles, biasing daughter cells towards a more fate-committed state and ultimately shortening the period of neurogenesis. This study provides a mechanism behind DENND5A -related DEE that may be generalizable to other developmental conditions and provides variant-specific clinical information for physicians and families.
The original article can be found online at https://doi.org/10.1038/s41436-021-01212-y. Correction to: Genetics in Medicine 2021; https://doi.org/10.1038/s41436-021-01212-y; published online 10 June 2021 Due to a processing error the author's Doris Škorić-Milosavljević, Najim Lahrouchi, Alex V. Postma, Connie R. Bezzina were assigned to affiliation 38. However, affiliation 38 does not exist. In addition, the affiliations of Najim Lahrouchi, Elisabeth M. Lodder, and Connie R. Bezzina should be number 1 instead of number 2. The correct affiliation is Department of Clinical and Experimental Cardiology, Amsterdam University Medical Center, Amsterdam, The Netherlands. The original article has been corrected. These authors contributed equally: Doris Škorić-Milosavljević, Najim Lahrouchi, Fernanda M. Bosada, Alex V. Postma, Connie R. Bezzina. A list of authors and their affiliations appears online. Rare variants in KDR, encoding VEGF Receptor 2, are associated with tetralogy of FallotGenetics in MedicineVol. 23Issue 10PreviewRare genetic variants in KDR, encoding the vascular endothelial growth factor receptor 2 (VEGFR2), have been reported in patients with tetralogy of Fallot (TOF). However, their role in disease causality and pathogenesis remains unclear. Full-Text PDF Open Access
