Parent perspectives on disclosing a pediatric neurofibromatosis type 1 diagnosis

Neurofibromatosis 1 (NF1) is a common genetic disorder typically diagnosed in childhood and characterized by cutaneous findings, nerve sheath tumors, skeletal abnormalities, malignancies, and developmental differences. Due to its variability, NF1 is an unpredictable condition that parents have concerns about discussing with their children. While there are publications addressing the disclosure of genetic conditions in general, no NF1-specific disclosure literature exists. To fill this gap, this mixed methods study sought to evaluate the concerns, barriers, failures, or successes parents or guardians have experienced when they have or have not chosen to tell their child(ren) about an NF1 diagnosis. Parents of children between ages 0 and 17 with a diagnosis of NF1 completed a survey and some parents were selected for an interview invitation. A total of 258 surveys were completed, and 20 parents were interviewed. Interview transcripts were categorized into disclosure and non-disclosure groups. Themes were organized into five categories based on interview questions: disclosure concerns, factors affecting disclosure/non-disclosure, approaches to disclosure, desired resources, and recommendations for disclosure. Sentiment analysis was performed on responses about the disclosure discussion itself. Results indicated that most parents (70.5%) disclosed the NF1 diagnosis to their child and overall felt it was a positive experience. Almost one-third of parents (29.5%) had not disclosed the diagnosis. A strong significance was identified between disclosure and severe presentation of NF1 (p = 0.0008). Parents in both groups shared similar concerns about discussing the diagnosis and multiple factors influenced the disclosure decision. Most parents approached disclosure as a process and emphasized the need to be honest and supportive of their child. Parents highlighted the need for more educational resources for children and guidance on how to disclose. These findings indicate that additional resources and support for parents would facilitate disclosure and the involvement of genetic counselors in the process would be beneficial.

Transition Readiness Assessment in Adolescents and Young Adults with Neurofibromatosis Type 1 (NF1)

Neurofibromatosis type 1 (NF1) conveys significant disease morbidity and lower quality of life compared to the general population. Research has shown that decreased positive health outcomes are directly correlated with inadequate development of health-related self-management skills among similar patient populations, and among these populations a healthcare transition (HCT) intervention improves provision of care and health outcomes. Thus, HCT intervention may improve care and outcomes in NF1. To design a future informed NF1 HCT intervention, baseline transition readiness must be assessed. A survey distributed by Children's Tumor Foundation (CTF) was developed to assess transition readiness and the impact of NF1 on factors of young adult life. A total of 101 participants aged 14-26 years living in the United States completed the survey with a median [IQR] age of 18 [16, 21]. The majority of participants reported that NF1 had significant or some impact on all factors of young adult life including education, career, relationships, and family planning. The median Transition Readiness Assessment Questionnaire (TRAQ) score in this study (3.50/5.00) was significantly lower than the previously published score of healthy peers (3.93/5.00) (p< .001). Higher TRAQ scores correlated with higher NF1-specific transition knowledge and skills (NF1-TRAQ) (r = 0.632). Participants self-report adequate knowledge of NF1 and comfort in talking to medical providers. They report discomfort with appointment keeping, insurance related tasks, addressing NF1 emergencies, and discussing NF1 with non-medical providers and peers. Further, TRAQ and NF1-TRAQ scores were lower in individuals who reported that their diagnosis of NF1 had some or significant impact on education, career, and relationships. Findings demonstrate that among individuals with NF1 in this study, decreased transition readiness is associated with a negative impact on young adult life. Data from this study supports the need to develop NF1-specific HCT intervention tools, with an effort to improve quality of life and standardize NF1 care.

Barriers to a successful healthcare transition for individuals with urea cycle disorders

The pediatric to adult healthcare transition (HCT) is a process for individuals with chronic health conditions to gradually shift from a pediatric to an adult-oriented care system. Autonomy and self-management skills required for an individual's HCT readiness can be evaluated through the transition readiness assessment questionnaire (TRAQ). Despite general HCT preparation guidelines, little is known about the HCT experience of individuals with a urea cycle disorder (UCD). This is the first study to report the parent or guardian perception of the HCT process in children with a UCD by investigating the stages of transition readiness and transition outcome. We identify barriers to HCT readiness and planning, along with deficiencies in transition outcome for individuals with a UCD. For children that received special education services compared to those that did not, significantly lower transition readiness scores were identified in the total TRAQ score (p = 0.03) and in the domains of tracking health issues (p = 0.02), talking with providers (p = 0.03), and managing daily activities (p = 0.01). There was a lack of HCT preparation as most subjects did not have a HCT discussion with their healthcare provider before age 26. Deficiencies in HCT outcome are demonstrated by individuals with a UCD reporting delays in needed medical care and dissatisfaction with their healthcare services. Considerations for facilitating a successful HCT for individuals with a UCD include providing individualized education, appointing a transition coordinator, allowing flexibility in HCT timing, and ensuring that the individual recognizes concerning UCD symptoms and knows when to seek medical care.

Parental perceptions of genetic testing for children with autism spectrum disorders

Children with autism spectrum disorder (ASD) routinely undergo genetic testing (GT) to identify the causative genetic etiology of their ASD. As there are questions about the impact of GT beyond clinical diagnosis, we conducted a mixed methods study to assess the perceived benefits of GT by exploring factors that lead parents to pursue these tests and the benefits experienced. Respondents were part of a pretest or posttest group. The pretest group (N = 22) expressed intent to pursue GT and the posttest group (N = 32) had undergone GT and received results at least 3 months prior to completing the survey. Responses were compared between and within groups. Free text responses were coded for themes and selection questions were analyzed using Fisher's exact tests. Our results demonstrate significant differences between the groups with participants in the pretest group more likely to choose "increased access to therapies" (p = 0.026) and "improved healthcare" (p < 0.000) as reasons to pursue testing. Benefits were also significantly different with "improved healthcare" (p = 0.009), "improved access to services" (p = 0.012), and "improved access to therapies" (p = 0.003) more frequently anticipated by the pretest group than reported by the posttest group. A relationship between GT and clinical management changes was reported by 34.4-50.0% of the posttest group. Among that group, genetic result type (positive, negative, or variant of uncertain significance) was associated with differing perceived benefits of testing. Thematic analysis revealed increased knowledge and coping as reported benefits in both groups. Our findings indicate a discrepancy between parental expectations and experiences of GT. Comprehensive pretest and posttest genetic counseling are necessary to improve information retention, address potential outcomes, and set expectations of GT for parents of children with ASD.

Germline mutation in POLR2A: a heterogeneous, multi-systemic developmental disorder characterized by transcriptional dysregulation

De novo germline variation in POLR2A was recently reported to associate with a neurodevelopmental disorder. We report twelve individuals harboring putatively pathogenic de novo or inherited variants in POLR2A, detail their phenotypes, and map all known variants to the domain structure of POLR2A and crystal structure of RNA polymerase II. Affected individuals were ascertained from a local data lake, pediatric genetics clinic, and an online community of families of affected individuals. These include six affected by de novo missense variants (including one previously reported individual), four clinical laboratory samples affected by missense variation with unknown inheritance-with yeast functional assays further supporting altered function-one affected by a de novo in-frame deletion, and one affected by a C-terminal frameshift variant inherited from a largely asymptomatic mother. Recurrently observed phenotypes include ataxia, joint hypermobility, short stature, skin abnormalities, congenital cardiac abnormalities, immune system abnormalities, hip dysplasia, and short Achilles tendons. We report a significantly higher occurrence of epilepsy (8/12, 66.7%) than previously reported (3/15, 20%) (p value = 0.014196; chi-square test) and a lower occurrence of hypotonia (8/12, 66.7%) than previously reported (14/15, 93.3%) (p value = 0.076309). POLR2A-related developmental disorders likely represent a spectrum of related, multi-systemic developmental disorders, driven by distinct mechanisms, converging at a single locus.

Missense variants in CTNNB1 can be associated with vitreoretinopathy-Seven new cases of CTNNB1-associated neurodevelopmental disorder including a previously unreported retinal phenotype

BACKGROUND

CTNNB1 (MIM 116806) encodes beta-catenin, an adherens junction protein that supports the integrity between layers of epithelial tissue and mediates intercellular signaling. Recently, various heterozygous germline variants in CTNNB1 have been associated with human disease, including neurodevelopmental disorder with spastic diplegia and visual defects (MIM 615075) as well as isolated familial exudative vitreoretinopathy without developmental delays or other organ system involvement (MIM 617572). From over 40 previously reported patients with CTNNB1-related neurodevelopmental disorder, many have had ocular anomalies including strabismus, hyperopia, and astigmatism. More recently, multiple reports indicate that these abnormalities are associated with the presence of vitreoretinopathy.

METHODS

We gathered a cohort of three patients with CTNNB1-related neurodevelopmental disorder, recruited from both our own clinic and referred from outside providers. We then searched for a clinical database comprised of over 12,000 exome sequencing studies to identify and recruit four additional patients.

RESULTS

Here, we report seven new cases of CTNNB1-related neurodevelopmental disorder, all harboring de novo variants, six of which were previously unreported. All patients but one presented with a spectrum of ocular abnormalities and one patient, who was found to carry a missense variant in CTNNB1, had notable vitreoretinopathy.

CONCLUSIONS

Our findings suggest ophthalmologic screening should be performed in all patients with CTNNB1 variants.

Retrospective Diagnosis of Ataxia-Telangiectasia in an Adolescent Patient With a Remote History of T-Cell Leukemia

Ataxia-telangiectasia (A-T) is a rare autosomal recessive disorder characterized by progressive cerebellar degeneration that is typically diagnosed in early childhood. A-T is associated with a predisposition to malignancies, particularly lymphoid tumors in childhood and early adulthood. An adolescent girl with minimal neurologic symptoms was diagnosed with A-T 8 years after completing therapy for T-cell acute lymphoblastic leukemia, following a diagnosis of ATM-mutated breast cancer in her mother. We highlight the importance of recognizing ATM mutations in T-cell acute lymphoblastic leukemia, appreciating the phenotypic heterogeneity of A-T, and defining optimal cancer screening in A-T patients.

Intraperitoneal bladder rupture in a young child with vascular Ehlers-Danlos syndrome

In this report, we present the case of a 3-year-old child with vascular Ehlers-Danlos syndrome (vEDS) previously known as Ehlers-Danlos syndrome type IV. After experiencing a minor traumatic injury to the abdomen, consisting of falling over a bathroom stool on the way to the restroom with a full bladder, the child developed acute abdominal pain. He was found to have an intraperitoneal bladder rupture that was successfully repaired with management techniques tailored to his known diagnosis of vEDS. While tissue fragility and internal organ rupture occurring with minor trauma are known complications of vEDS, this is the first case in the literature of a bladder rupture in a child with vEDS with a confirmed variant in the COL3A1 gene, to our knowledge. This case broadens the clinical presentation of vEDS, demonstrates that children can have life-threatening organ rupture at a young age, and may alert providers to consider this diagnosis when a child presents with bladder rupture.

Evaluation and classification of severity for 176 genes on an expanded carrier screening panel

Background

Disease severity is important when considering genes for inclusion on reproductive expanded carrier screening (ECS) panels. We applied a validated and previously published algorithm that classifies diseases into four severity categories (mild, moderate, severe, and profound) to 176 genes screened by ECS. Disease traits defining severity categories in the algorithm were then mapped to four severity‐related ECS panel design criteria cited by the American College of Obstetricians and Gynecologists (ACOG).

Methods

Eight genetic counselors (GCs) and four medical geneticists (MDs) applied the severity algorithm to subsets of 176 genes. MDs and GCs then determined by group consensus how each of these disease traits mapped to ACOG severity criteria, enabling determination of the number of ACOG severity criteria met by each gene.

Results

Upon consensus GC and MD application of the severity algorithm, 68 (39%) genes were classified as profound, 71 (40%) as severe, 36 (20%) as moderate, and one (1%) as mild. After mapping of disease traits to ACOG severity criteria, 170 out of 176 genes (96.6%) were found to meet at least one of the four criteria, 129 genes (73.3%) met at least two, 73 genes (41.5%) met at least three, and 17 genes (9.7%) met all four.

Conclusion

This study classified the severity of a large set of Mendelian genes by collaborative clinical expert application of a trait‐based algorithm. Further, it operationalized difficult to interpret ACOG severity criteria via mapping of disease traits, thereby promoting consistency of ACOG criteria interpretation.

BAZ2B haploinsufficiency as a cause of developmental delay, intellectual disability, and autism spectrum disorder

The bromodomain adjacent to zinc finger 2B gene (BAZ2B) encodes a protein involved in chromatin remodeling. Loss of BAZ2B function has been postulated to cause neurodevelopmental disorders. To determine whether BAZ2B deficiency is likely to contribute to the pathogenesis of these disorders, we performed bioinformatics analyses that demonstrated a high level of functional convergence during fetal cortical development between BAZ2B and genes known to cause autism spectrum disorder (ASD) and neurodevelopmental disorder. We also found an excess of de novo BAZ2B loss-of-function variants in exome sequencing data from previously published cohorts of individuals with neurodevelopmental disorders. We subsequently identified seven additional individuals with heterozygous deletions, stop-gain, or de novo missense variants affecting BAZ2B. All of these individuals have developmental delay (DD), intellectual disability (ID), and/or ASD. Taken together, our findings suggest that haploinsufficiency of BAZ2B causes a neurodevelopmental disorder, whose cardinal features include DD, ID, and ASD.

Abstract 53: Missense Pathogenic Variants in ANO1 Predispose to Moyamoya Disease

Introduction: Moyamoya disease (MMD) is a cerebrovascular disease often causing pediatric onset strokes and characterized by progressive bilateral occlusion of the distal internal carotid arteries and formation of a compensatory network of collateral vessels. Several genes harbor variants that increase the risk for MMD, but the majority of cases of European descent does not have an identified genetic cause.

Hypothesis: MMD is associated with significant genetic heterogeneity, i.e., many genes in the human genome can be altered to predispose to this condition.

Methods: To identify novel genes for MMD, exome sequencing was performed on DNA from 145 individuals from 80 families with one or more affected members. Bioinformatics filtering included a CADD (GRCh37-v1.4) score > 20 and a minor allele frequency < 0.0001 in gnomAD (v2.1.1 controls). For a subset of ANO1 mutant alleles, we characterized the channel activities via patch recording and assessed protein localization in heterologous cell cultures.

Results: We identified 6 rare variants in ANO1 ( TMEM16A ), which encodes an evolutionarily conserved calcium-activated chloride channel. One rare heterozygous variant, p.Met658Val (CADD: 22.9, absent in gnomAD), was found in two very distantly related MMD families and segregated with disease in multiple affected members; p.Glu459Lys and p.Arg890Gln were identified in two unrelated affected probands. Through Matchmaker Exchange (MyGene2) collaboration, we identified 3 additional rare variants: homozygous p.Glu170Lys in a consanguineous MMD family, heterozygous p.Thr740Ile in a MMD case and p.Ala333Ser in a case with ischemic stroke. Functional analyses determined that p.Glu170Lys affects channel gating and calcium sensitivity, producing much smaller chloride current, but the channel itself is more sensitive to calcium, which means it is more likely to open. Ano1 knock out (KO) in mice is lethal by 1 week of age with pathology in multiple organ systems. Smooth muscle cells-specific KO is not lethal, and phenotyping of these mice is ongoing.

Conclusions: ANO1 is a novel gene predisposing to MMD and future studies will focus on defining the role of ANO1 protein to connect the altered gene to the occlusive lesions observed in MMD patients.

Deficient histone H3 propionylation by BRPF1-KAT6 complexes in neurodevelopmental disorders and cancer

Lysine acetyltransferase 6A (KAT6A) and its paralog KAT6B form stoichiometric complexes with bromodomain- and PHD finger-containing protein 1 (BRPF1) for acetylation of histone H3 at lysine 23 (H3K23). We report that these complexes also catalyze H3K23 propionylation in vitro and in vivo. Immunofluorescence microscopy and ATAC-See revealed the association of this modification with active chromatin. Brpf1 deletion obliterates the acylation in mouse embryos and fibroblasts. Moreover, we identify BRPF1 variants in 12 previously unidentified cases of syndromic intellectual disability and demonstrate that these cases and known BRPF1 variants impair H3K23 propionylation. Cardiac anomalies are present in a subset of the cases. H3K23 acylation is also impaired by cancer-derived somatic BRPF1 mutations. Valproate, vorinostat, propionate and butyrate promote H3K23 acylation. These results reveal the dual functionality of BRPF1-KAT6 complexes, shed light on mechanisms underlying related developmental disorders and various cancers, and suggest mutation-based therapy for medical conditions with deficient histone acylation.

Clinical spectrum of individuals with pathogenic NF1 missense variants affecting p.Met1149, p.Arg1276, and p.Lys1423: genotype-phenotype study in neurofibromatosis type 1

We report 281 individuals carrying a pathogenic recurrent NF1 missense variant at p.Met1149, p.Arg1276, or p.Lys1423, representing three nontruncating NF1 hotspots in the University of Alabama at Birmingham (UAB) cohort, together identified in 1.8% of unrelated NF1 individuals. About 25% (95% confidence interval: 20.5-31.2%) of individuals heterozygous for a pathogenic NF1 p.Met1149, p.Arg1276, or p.Lys1423 missense variant had a Noonan-like phenotype, which is significantly more compared with the "classic" NF1-affected cohorts (all p < .0001). Furthermore, p.Arg1276 and p.Lys1423 pathogenic missense variants were associated with a high prevalence of cardiovascular abnormalities, including pulmonic stenosis (all p < .0001), while p.Arg1276 variants had a high prevalence of symptomatic spinal neurofibromas (p < .0001) compared with "classic" NF1-affected cohorts. However, p.Met1149-positive individuals had a mild phenotype, characterized mainly by pigmentary manifestations without externally visible plexiform neurofibromas, symptomatic spinal neurofibromas or symptomatic optic pathway gliomas. As up to 0.4% of unrelated individuals in the UAB cohort carries a p.Met1149 missense variant, this finding will contribute to more accurate stratification of a significant number of NF1 individuals. Although clinically relevant genotype-phenotype correlations are rare in NF1, each affecting only a small percentage of individuals, together they impact counseling and management of a significant number of the NF1 population.

Novel Missense Variants in ADAT3 as a Cause of Syndromic Intellectual Disability

Autosomal recessive variants in the adenosine deaminase, tRNA specific 3 ( ADAT3 ) gene cause a syndromic form of intellectual disability due to a loss of ADAT3 function. This disorder is characterized by developmental delay, intellectual disability, speech delay, abnormal brain structure, strabismus, microcephaly, and failure to thrive. A small subset of individuals with ADAT3 deficiency have other structural birth defects including atrial septal defect, patent ductus arteriosus, hypospadias, cryptorchidism, and micropenis. Here, we report a sibling pair with novel compound heterozygous missense variants that affect a conserved amino acid in the deaminase domain of ADAT3. These siblings have many of the features characteristic of this syndrome, including, intellectual disability, hypotonia, esotropia, failure to thrive, and microcephaly. Both had gastroesophageal reflux disease (GERD), feeding problems, and aspiration requiring thickening of feeds. Although they have no words, their communication abilities progressed rapidly when they began to use augmentative and alternative communication (AAC) devices. One of these siblings was born with an anterior congenital diaphragmatic hernia, which has not been reported previously in association with ADAT3 deficiency. We conclude that individuals with ADAT3 deficiency should be monitored for GERD, feeding problems, and aspiration in infancy. They may also benefit from the use of AAC devices and individualized educational programs that take into account their capacity for nonverbal language development. Additional studies in humans or animal models will be needed to determine if ADAT3 deficiency predisposes to the development of structural birth defects.

Biallelic loss-of-function P4HTM gene variants cause hypotonia, hypoventilation, intellectual disability, dysautonomia, epilepsy, and eye abnormalities (HIDEA syndrome)

PURPOSE

A new syndrome with hypotonia, intellectual disability, and eye abnormalities (HIDEA) was previously described in a large consanguineous family. Linkage analysis identified the recessive disease locus, and genome sequencing yielded three candidate genes with potentially pathogenic biallelic variants: transketolase (TKT), transmembrane prolyl 4-hydroxylase (P4HTM), and ubiquitin specific peptidase 4 (USP4). However, the causative gene remained elusive.

METHODS

International collaboration and exome sequencing were used to identify new patients with HIDEA and biallelic, potentially pathogenic, P4HTM variants. Segregation analysis was performed using Sanger sequencing. P4H-TM wild-type and variant constructs without the transmembrane region were overexpressed in insect cells and analyzed using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and western blot.

RESULTS

Five different homozygous or compound heterozygous pathogenic P4HTM gene variants were identified in six new and six previously published patients presenting with HIDEA. Hypoventilation, obstructive and central sleep apnea, and dysautonomia were identified as novel features associated with the phenotype. Characterization of three of the P4H-TM variants demonstrated yielding insoluble protein products and, thus, loss-of-function.

CONCLUSIONS

Biallelic loss-of-function P4HTM variants were shown to cause HIDEA syndrome. Our findings enable diagnosis of the condition, and highlight the importance of assessing the need for noninvasive ventilatory support in patients.

Expanding the clinical phenotype of individuals with a 3-bp in-frame deletion of the NF1 gene (c.2970_2972del): an update of genotype-phenotype correlation

PURPOSE

Neurofibromatosis type 1 (NF1) is characterized by a highly variable clinical presentation, but almost all NF1-affected adults present with cutaneous and/or subcutaneous neurofibromas. Exceptions are individuals heterozygous for the NF1 in-frame deletion, c.2970_2972del (p.Met992del), associated with a mild phenotype without any externally visible tumors.

METHODS

A total of 135 individuals from 103 unrelated families, all carrying the constitutional NF1 p.Met992del pathogenic variant and clinically assessed using the same standardized phenotypic checklist form, were included in this study.

RESULTS

None of the individuals had externally visible plexiform or histopathologically confirmed cutaneous or subcutaneous neurofibromas. We did not identify any complications, such as symptomatic optic pathway gliomas (OPGs) or symptomatic spinal neurofibromas; however, 4.8% of individuals had nonoptic brain tumors, mostly low-grade and asymptomatic, and 38.8% had cognitive impairment/learning disabilities. In an individual with the NF1 constitutional c.2970_2972del and three astrocytomas, we provided proof that all were NF1-associated tumors given loss of heterozygosity at three intragenic NF1 microsatellite markers and c.2970_2972del.

CONCLUSION

We demonstrate that individuals with the NF1 p.Met992del pathogenic variant have a mild NF1 phenotype lacking clinically suspected plexiform, cutaneous, or subcutaneous neurofibromas. However, learning difficulties are clearly part of the phenotypic presentation in these individuals and will require specialized care.

Loss-of-function mutations in Lysyl-tRNA synthetase cause various leukoencephalopathy phenotypes

OBJECTIVE

To expand the clinical spectrum of lysyl-tRNA synthetase (KARS) gene-related diseases, which so far includes Charcot-Marie-Tooth disease, congenital visual impairment and microcephaly, and nonsyndromic hearing impairment.

METHODS

Whole-exome sequencing was performed on index patients from 4 unrelated families with leukoencephalopathy. Candidate pathogenic variants and their cosegregation were confirmed by Sanger sequencing. Effects of mutations on KARS protein function were examined by aminoacylation assays and yeast complementation assays.

RESULTS

Common clinical features of the patients in this study included impaired cognitive ability, seizure, hypotonia, ataxia, and abnormal brain imaging, suggesting that the CNS involvement is the main clinical presentation. Six previously unreported and 1 known KARS mutations were identified and cosegregated in these families. Two patients are compound heterozygous for missense mutations, 1 patient is homozygous for a missense mutation, and 1 patient harbored an insertion mutation and a missense mutation. Functional and structural analyses revealed that these mutations impair aminoacylation activity of lysyl-tRNA synthetase, indicating that defective KARS function is responsible for the phenotypes in these individuals.

CONCLUSIONS

Our results demonstrate that patients with loss-of-function KARS mutations can manifest CNS disorders, thus broadening the phenotypic spectrum associated with KARS-related disease.

Correction: Expanding the clinical phenotype of individuals with a 3-bp in-frame deletion of the NF1 gene (c.2970_2972del): an update of genotype-phenotype correlation

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De novo and inherited TCF20 pathogenic variants are associated with intellectual disability, dysmorphic features, hypotonia, and neurological impairments with similarities to Smith-Magenis syndrome

BACKGROUND

Neurodevelopmental disorders are genetically and phenotypically heterogeneous encompassing developmental delay (DD), intellectual disability (ID), autism spectrum disorders (ASDs), structural brain abnormalities, and neurological manifestations with variants in a large number of genes (hundreds) associated. To date, a few de novo mutations potentially disrupting TCF20 function in patients with ID, ASD, and hypotonia have been reported. TCF20 encodes a transcriptional co-regulator structurally related to RAI1, the dosage-sensitive gene responsible for Smith-Magenis syndrome (deletion/haploinsufficiency) and Potocki-Lupski syndrome (duplication/triplosensitivity).

METHODS

Genome-wide analyses by exome sequencing (ES) and chromosomal microarray analysis (CMA) identified individuals with heterozygous, likely damaging, loss-of-function alleles in TCF20. We implemented further molecular and clinical analyses to determine the inheritance of the pathogenic variant alleles and studied the spectrum of phenotypes.

RESULTS

We report 25 unique inactivating single nucleotide variants/indels (1 missense, 1 canonical splice-site variant, 18 frameshift, and 5 nonsense) and 4 deletions of TCF20. The pathogenic variants were detected in 32 patients and 4 affected parents from 31 unrelated families. Among cases with available parental samples, the variants were de novo in 20 instances and inherited from 4 symptomatic parents in 5, including in one set of monozygotic twins. Two pathogenic loss-of-function variants were recurrent in unrelated families. Patients presented with a phenotype characterized by developmental delay, intellectual disability, hypotonia, variable dysmorphic features, movement disorders, and sleep disturbances.

CONCLUSIONS

TCF20 pathogenic variants are associated with a novel syndrome manifesting clinical characteristics similar to those observed in Smith-Magenis syndrome. Together with previously described cases, the clinical entity of TCF20-associated neurodevelopmental disorders (TAND) emerges from a genotype-driven perspective.

Extending the MNREAD sentence corpus: Computer-generated sentences for measuring visual performance in reading

The MNREAD chart consists of standardized sentences printed at 19 sizes in 0.1 logMAR steps. There are 95 sentences distributed across the five English versions of the chart. However, there is a demand for a much larger number of sentences: for clinical research requiring repeated measures, and for new vision tests that use multiple trials at each print size. This paper describes a new sentence generator that has produced over nine million sentences that fit the MNREAD constraints, and demonstrates that reading performance with these new sentences is comparable to that obtained with the original MNREAD sentences. We measured reading performance with the original MNREAD sentences, two sets of our new sentences, and sentences with shuffled word order. Reading-speed versus print-size curves were obtained for each sentence set from 14 readers with normal vision at two levels of blur (intended to simulate acuity loss in low vision) and with unblurred text. We found no significant differences between the new and original sentences in reading acuity and critical print size across all levels of blur. Maximum reading speed was 7% slower with the new sentences than with the original sentences. Shuffled sentences yielded slower maximum reading speeds and larger reading acuities than the other sentences. Overall, measures of reading performance with the new sentences are similar to those obtained with the original MNREAD sentences. Our sentence generator substantially expands the reading materials for clinical research on reading vision using the MNREAD test, and opens up new possibilities for measuring how text parameters affect reading.

ZMIZ1 Variants Cause a Syndromic Neurodevelopmental Disorder

ZMIZ1 is a coactivator of several transcription factors, including p53, the androgen receptor, and NOTCH1. Here, we report 19 subjects with intellectual disability and developmental delay carrying variants in ZMIZ1. The associated features include growth failure, feeding difficulties, microcephaly, facial dysmorphism, and various other congenital malformations. Of these 19, 14 unrelated subjects carried de novo heterozygous single-nucleotide variants (SNVs) or single-base insertions/deletions, 3 siblings harbored a heterozygous single-base insertion, and 2 subjects had a balanced translocation disrupting ZMIZ1 or involving a regulatory region of ZMIZ1. In total, we identified 13 point mutations that affect key protein regions, including a SUMO acceptor site, a central disordered alanine-rich motif, a proline-rich domain, and a transactivation domain. All identified variants were absent from all available exome and genome databases. In vitro, ZMIZ1 showed impaired coactivation of the androgen receptor. In vivo, overexpression of ZMIZ1 mutant alleles in developing mouse brains using in utero electroporation resulted in abnormal pyramidal neuron morphology, polarization, and positioning, underscoring the importance of ZMIZ1 in neural development and supporting mutations in ZMIZ1 as the cause of a rare neurodevelopmental syndrome.

Biallelic mutations in the ferredoxin reductase gene cause novel mitochondriopathy with optic atrophy

Iron-sulfur (Fe-S) clusters are ubiquitous cofactors essential to various cellular processes, including mitochondrial respiration, DNA repair, and iron homeostasis. A steadily increasing number of disorders are being associated with disrupted biogenesis of Fe-S clusters. Here, we conducted whole-exome sequencing of patients with optic atrophy and other neurological signs of mitochondriopathy and identified 17 individuals from 13 unrelated families with recessive mutations in FDXR, encoding the mitochondrial membrane-associated flavoprotein ferrodoxin reductase required for electron transport from NADPH to cytochrome P450. In vitro enzymatic assays in patient fibroblast cells showed deficient ferredoxin NADP reductase activity and mitochondrial dysfunction evidenced by low oxygen consumption rates (OCRs), complex activities, ATP production and increased reactive oxygen species (ROS). Such defects were rescued by overexpression of wild-type FDXR. Moreover, we found that mice carrying a spontaneous mutation allelic to the most common mutation found in patients displayed progressive gait abnormalities and vision loss, in addition to biochemical defects consistent with the major clinical features of the disease. Taken together, these data provide the first demonstration that germline, hypomorphic mutations in FDXR cause a novel mitochondriopathy and optic atrophy in humans.

Congenital hyperinsulinism as the presenting feature of Kabuki syndrome: clinical and molecular characterization of 9 affected individuals

PURPOSE

Describe the clinical and molecular findings of patients with Kabuki syndrome (KS) who present with hypoglycemia due to congenital hyperinsulinism (HI), and assess the incidence of KS in patients with HI.

METHODS

We documented the clinical features and molecular diagnoses of 9 infants with persistent HI and KS via a combination of sequencing and copy-number profiling methodologies. Subsequently, we retrospectively evaluated 100 infants with HI lacking a genetic diagnosis, for causative variants in KS genes.

RESULTS

Molecular diagnoses of KS were established by identification of pathogenic variants in KMT2D (n = 5) and KDM6A (n = 4). Among the 100 infants with HI of unknown genetic etiology, a KS diagnosis was uncovered in one patient.

CONCLUSIONS

The incidence of HI among patients with KS may be higher than previously reported, and KS may account for as much as 1% of patients diagnosed with HI. As the recognition of dysmorphic features associated with KS is challenging in the neonatal period, we propose KS should be considered in the differential diagnosis of HI. Since HI in patients with KS is well managed medically, a timely recognition of hyperinsulinemic episodes will improve outcomes, and prevent aggravation of the preexisting mild to moderate intellectual disability in KS.