Publications by authors named "Rebecca C Spillmann"

Article Synopsis
  • - The study evaluated the efficacy of telehealth in conducting physical examinations (PE) for individuals with undiagnosed and rare disorders, comparing virtual assessments to in-person examinations.
  • - Results showed high agreement in general appearance and craniofacial features between telehealth and in-person evaluations, with varying levels of agreement for neurological examination components.
  • - Participants reported satisfaction with the telehealth experience, indicating that telehealth is a viable alternative for conducting physical examinations in cases of undiagnosed diseases.
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The heterotrimeric protein phosphatase 2A (PP2A) complex catalyzes about half of Ser/Thr dephosphorylations in eukaryotic cells. A CAG repeat expansion in the neuron-specific protein PP2A regulatory subunit PPP2R2B gene causes spinocerebellar ataxia type 12 (SCA12). We established five monoallelic missense variants in PPP2R2B (four confirmed as de novo) as a cause of intellectual disability with developmental delay (R149P, T246K, N310K, E37K, I427T).

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Developmental and epileptic encephalopathies (DEEs) feature altered brain development, developmental delay and seizures, with seizures exacerbating developmental delay. Here we identify a cohort with biallelic variants in DENND5A, encoding a membrane trafficking protein, and develop animal models with phenotypes like the human syndrome. We demonstrate that DENND5A interacts with Pals1/MUPP1, components of the Crumbs apical polarity complex required for symmetrical division of neural progenitor cells.

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Article Synopsis
  • - The study explores pre-mRNA splicing, its critical role in neurodevelopment, and how mutations in spliceosome-related genes U2AF2 and PRPF19 contribute to neurodevelopmental disorders (NDDs).
  • - Researchers found multiple pathogenic variants in U2AF2 and PRPF19 across unrelated individuals, with functional analysis showing that specific U2AF2 variants disrupted normal splicing and neuritogenesis in human neurons.
  • - Additionally, investigations in Drosophila models revealed that the loss of function in U2AF2 and PRPF19 caused severe developmental defects and social issues, pointing to a genetic network wherein splicing factors like Rbfox1 play a significant role in brain development and function. *
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Genomic medicine has been transformed by next-generation sequencing (NGS), inclusive of exome sequencing (ES) and genome sequencing (GS). Currently, ES is offered widely in clinical settings, with a less prevalent alternative model consisting of hybrid programs that incorporate research ES along with clinical patient workflows. We were among the earliest to implement a hybrid ES clinic, have provided diagnoses to 45% of probands, and have identified several novel candidate genes.

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Article Synopsis
  • DExD/H-box RNA helicases (DDX/DHX) are a large gene family linked to neurodevelopmental disorders and cancer, with DHX9 being a key member associated with various phenotypes.
  • Analysis of individuals with rare DHX9 variants revealed a range of neurodevelopmental disorder traits and the genetic basis for these phenotypes correlated with the type of variant.
  • Experimental investigations showed that DHX9 variants impact its cellular localization and function, linking them to conditions like Charcot-Marie-Tooth disease and highlighting DHX9's role in neurodevelopment and neuronal stability.
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Although genomic research offering next-generation sequencing (NGS) has increased the diagnoses of rare/ultra-rare disorders, populations experiencing health disparities infrequently participate in these studies. The factors underlying non-participation would most reliably be ascertained from individuals who have had the opportunity to participate, but decline. We thus enrolled parents of children and adult probands with undiagnosed disorders who had declined genomic research offering NGS with return of results with undiagnosed disorders (Decliners, n = 21) and compared their data to those who participated (Participants, n = 31).

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Sphingolipids are a diverse family of lipids with critical structural and signalling functions in the mammalian nervous system, where they are abundant in myelin membranes. Serine palmitoyltransferase, the enzyme that catalyses the rate-limiting reaction of sphingolipid synthesis, is composed of multiple subunits including an activating subunit, SPTSSA. Sphingolipids are both essential and cytotoxic and their synthesis must therefore be tightly regulated.

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Exome sequencing (ES) and genome sequencing (GS) have radically transformed the diagnostic approach to undiagnosed rare/ultrarare Mendelian diseases. Next-generation sequencing (NGS), the technology integral for ES, GS, and most large (100+) gene panels, has enabled previously unimaginable diagnoses, changes in medical management, new treatments, and accurate reproductive risk assessments for patients, as well as new disease gene discoveries. Yet, challenges remain, as most individuals remain undiagnosed with current NGS.

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Purpose: Next-generation sequencing (NGS) has revolutionized the diagnostic process for rare/ultrarare conditions. However, diagnosis rates differ between analytical pipelines. In the National Institutes of Health-Undiagnosed Diseases Network (UDN) study, each individual's NGS data are concurrently analyzed by the UDN sequencing core laboratory and the clinical sites.

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Au-Kline syndrome (AKS) is a neurodevelopmental disorder associated with multiple malformations and a characteristic facial gestalt. The first individuals ascertained carried de novo loss-of-function (LoF) variants in HNRNPK. Here, we report 32 individuals with AKS (26 previously unpublished), including 13 with de novo missense variants.

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Article Synopsis
  • SPTBN1 gene encodes βII-spectrin, crucial for forming networks at plasma membranes, and its deficiency in mice leads to significant neurodevelopmental issues.
  • Heterozygous variants of SPTBN1 were identified in 29 individuals exhibiting a range of developmental challenges, including intellectual disabilities, language delays, and autistic features.
  • These variants weaken βII-spectrin stability and disrupt cellular organization, establishing SPTBN1 as a key contributor to certain neurodevelopmental syndromes.
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  • CACNA1C is a gene that encodes a crucial part of a calcium channel found in the heart and brain, and variants in it have been linked to Timothy syndrome and long QT syndrome, but this study focuses on its neurological effects.
  • The study examined 25 individuals from 22 families with heterozygous variants in CACNA1C, showing a range of neurological issues like developmental delays, autism, hypotonia, ataxia, and epilepsy.
  • Results indicate that these variants can lead to different functional changes in the calcium channel, expanding the understanding of CACNA1C's role in neurodevelopmental disorders beyond previously known syndromes.
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The Genome Empowerment Scale (GEmS), developed as a research tool, assesses perspectives of parents of children with undiagnosed disorders about to undergo exome or genome sequencing related to the process of empowerment. We defined genomic healthcare empowerment as follows: perceived ability to understand and seek new information related to the genomic sequencing, manage emotions related to the diagnostic process and outcomes, and utilize genomic sequencing information to the betterment of the individual/child and family. The GEmS consists of four scales, two are primarily emotion-focused (Meaning of a Diagnosis, and Emotional Management of the Process) and two are action-oriented (Seeking Information and Support, and Implications and Planning).

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Article Synopsis
  • Large-scale statistical analyses identify disease-gene relationships but fail to accurately represent how specific genetic variations affect observable traits and disease mechanisms.
  • The study focuses on the SATB1 gene, showing that different types of variants lead to similar yet distinct neurodevelopmental disorders, revealing notable genotype-phenotype relationships.
  • Variants causing strong chromatin binding lead to severe disorders, while those causing mild effects highlight the need for detailed studies on specific mutations to better understand the complexities of genetic diseases.
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We investigated seven children from six families to expand the phenotypic spectrum associated with an early infantile epileptic encephalopathy caused by biallelic pathogenic variants in the phosphatidylinositol glycan anchor biosynthesis class Q (PIGQ) gene. The affected children were all identified by clinical or research exome sequencing. Clinical data, including EEGs and MRIs, was comprehensively reviewed and flow cytometry and transfection experiments were performed to investigate PIGQ function.

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Pathogenic variants in KMT2D, which encodes lysine specific methyltransferase 2D, cause autosomal dominant Kabuki syndrome, associated with distinctive dysmorphic features including arched eyebrows, long palpebral fissures with eversion of the lower lid, large protuberant ears, and fetal finger pads. Most disease-causing variants identified to date are putative loss-of-function alleles, although 15-20% of cases are attributed to missense variants. We describe here four patients (including one previously published patient) with de novo KMT2D missense variants and with shared but unusual clinical findings not typically seen in Kabuki syndrome, including athelia (absent nipples), choanal atresia, hypoparathyroidism, delayed or absent pubertal development, and extreme short stature.

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Purpose: Haploinsufficiency of USP7, located at chromosome 16p13.2, has recently been reported in seven individuals with neurodevelopmental phenotypes, including developmental delay/intellectual disability (DD/ID), autism spectrum disorder (ASD), seizures, and hypogonadism. Further, USP7 was identified to critically incorporate into the MAGEL2-USP7-TRIM27 (MUST), such that pathogenic variants in USP7 lead to altered endosomal F-actin polymerization and dysregulated protein recycling.

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SMARCC2 (BAF170) is one of the invariable core subunits of the ATP-dependent chromatin remodeling BAF (BRG1-associated factor) complex and plays a crucial role in embryogenesis and corticogenesis. Pathogenic variants in genes encoding other components of the BAF complex have been associated with intellectual disability syndromes. Despite its significant biological role, variants in SMARCC2 have not been directly associated with human disease previously.

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Article Synopsis
  • - The Undiagnosed Diseases Network (UDN) evaluates patients with persistent symptoms that haven’t been diagnosed, but many applicants primarily experience subjective symptoms like pain and fatigue rather than clear objective findings.
  • - A study reviewed applications to the UDN, comparing 151 Not Accepted cases with 50 randomly selected Accepted cases, to analyze symptoms, referral sources, and demographic differences affecting the outcome of the applications.
  • - Findings revealed that Not Accepted applicants had more subjective symptoms, were typically older, had a shorter illness duration, and were primarily referred by their primary care doctors, indicating key differences that may predict acceptance for further evaluation in the UDN.
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Interferon regulatory factor 2 binding protein-like (IRF2BPL) encodes a member of the IRF2BP family of transcriptional regulators. Currently the biological function of this gene is obscure, and the gene has not been associated with a Mendelian disease. Here we describe seven individuals who carry damaging heterozygous variants in IRF2BPL and are affected with neurological symptoms.

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Recent evidence has implicated in a phenotype overlapping Shwachman-Diamond syndrome (SDS), with the functional interplay between and the previously known causative gene accounting for the similarity in clinical features. Relatively little is known about the phenotypes associated with pathogenic variants in the gene, but the initial indication was that phenotypes may be more severe, when compared with SDS. We report a pediatric patient who presented with a metaphyseal dysplasia and was found to have biallelic variants in on reanalysis of trio whole-exome sequencing data.

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