PURPOSE: HOXD13 is an important regulator of limb development. Pathogenic variants in HOXD13 cause synpolydactyly type 1 (SPD1). How different types and positions of HOXD13 variants contribute to genotype-phenotype correlations, penetrance, and expressivity of SPD1 remains elusive. Here, we present a novel cohort and a literature review to elucidate HOXD13 phenotype-genotype correlations. METHODS: Patients with limb anomalies suggestive of SPD1 were selected for analysis of HOXD13 by Sanger sequencing, repeat length analysis, and next-generation sequencing. Literature was reviewed for HOXD13 heterozygotes. Variants were annotated for phenotypic data. Severity was calculated, and cluster and decision-tree analyses were performed. RESULTS: We identified 98 affected members of 38 families featuring 11 different (likely) causative variants and 4 variants of uncertain significance. The most frequent (25/38) were alanine repeat expansions. Phenotypes ranged from unaffected heterozygotes to severe osseous synpolydactyly, with intra- and inter-familial heterogeneity and asymmetry. A literature review provided 160 evaluable affected members of 49 families with SPD1. Computer-aided analysis only corroborated a positive correlation between alanine repeat length and phenotype severity. CONCLUSION: Our findings support that HOXD13-protein condensation in addition to haploinsufficiency is the molecular pathomechanism of SPD1. Our data may, also, facilitate the interpretation of synpolydactyly radiographs by future automated tools.

PURPOSE: To describe variation in genomic medicine services across level IV neonatal intensive care units (NICUs) in the United States and Canada. METHODS: We developed and distributed a novel survey to the 43 level IV NICUs belonging to the Children's Hospitals Neonatal Consortium, requesting a single response per site from a clinician with knowledge of the provision of genomic medicine services. RESULTS: Overall response rate was 74% (32/43). Although chromosomal microarray and exome or genome sequencing (ES or GS) were universally available, access was restricted for 22% (7/32) and 81% (26/32) of centers, respectively. The most common restriction on ES or GS was requiring approval by a specialist (41%, 13/32). Rapid ES/GS was available in 69% of NICUs (22/32). Availability of same-day genetics consultative services was limited (41%, 13/32 sites), and pre- and post-test counseling practices varied widely. CONCLUSION: We observed large inter-center variation in genomic medicine services across level IV NICUs: most notably, access to rapid, comprehensive genetic testing in time frames relevant to critical care decision making was limited at many level IV Children's Hospitals Neonatal Consortium NICUs despite a significant burden of genetic disease. Further efforts are needed to improve access to neonatal genomic medicine services.

PURPOSE: To date, there is no systematic method to quantify the medical burden of individuals with 22q11.2 deletion syndrome (22q11.2DS). This study aimed to design a Medical Burden Scale for 22q11.2DS to evaluate the effect of medical symptoms severity on quality of life (QoL) and functioning in individuals with this syndrome. METHODS: Individuals with 22q11.2DS (n = 76) were included in the study. A multidisciplinary group of physicians determined the severity of symptoms (on a scale of 0 to 4) of 8 major medical systems affected in 22q11.2DS, as well as the level of cognitive deficits and psychiatric morbidity. Regression models were used to evaluate the impact of medical, cognitive, and psychiatric symptoms' severity on global assessment of functioning (GAF) and QoL. RESULTS: The total Medical Burden Scale score was significantly associated with both QoL and GAF scores, beyond the effect of the psychiatric and cognitive deficits. We also found that QoL and GAF scores were associated with the severity scores of specific medical systems, particularly neurological symptoms, but also cardiovascular, ear-nose-throat, endocrinology, and orthopedics. CONCLUSION: Quantifying the medical burden of 22q11.2DS individuals is feasible and indicates the overall and specific contribution of medical symptoms to QoL and functioning of 22q11.2DS individuals.

PURPOSE: Variants of uncertain significance (VUS) are a common result of diagnostic genetic testing and can be difficult to manage with potential misinterpretation and downstream costs, including time investment by clinicians. We investigated the rate of VUS reported on diagnostic testing via multi-gene panels (MGPs) and exome and genome sequencing (ES/GS) to measure the magnitude of uncertain results and explore ways to reduce their potentially detrimental impact. METHODS: Rates of inconclusive results due to VUS were collected from over 1.5 million sequencing test results from 19 clinical laboratories in North America from 2020 - 2021. RESULTS: We found a lower rate of inconclusive test results due to VUSs from ES/GS (22.5%) compared to MGPs (32.6%; p<0.0001). For MGPs, the rate of inconclusive results correlated with panel size. The use of trios reduced inconclusive rates (18.9% vs 27.6%; p<0.001) whereas the use of GS compared to ES had no impact (22.2% vs 22.6%; p=ns). CONCLUSION: The high rate of VUS observed in diagnostic MGP testing warrants examining current variant reporting practices. We propose several approaches to reduce reported VUS rates, while directing clinician resources towards important VUS follow-up.

PURPOSE: Although preconception reproductive genetic carrier screening (RGCS) is preferred to screening during pregnancy, population-wide preconception screening is not routinely performed in the United States. We explored the multilevel barriers to the widespread adoption of preconception RGCS in the United States via key informant interviews. METHODS: Semi-structured virtual video interviews were conducted with 29 informants with a breadth of professional expertise between May and October 2022. Data collection and qualitative analyses were guided by the Consolidated Framework for Implementation Research and socioecological model. Analysis focused on identifying barriers to delivering preconception RGCS at and across different levels of health care and exploring potential facilitators of preconception RGCS delivery. RESULTS: Barriers to preconception RGCS were identified at the levels of test characteristics, patients and couples, clinicians and care teams, and the external health care and policy environments. Across the different levels of care delivery, 3 themes of barriers emerged: (1) fragmentation and inconsistencies hinder care delivery, (2) gaps in knowledge, misconceptions, and uncertainties about RGCS are pervasive, and (3) expanding preconception RGCS in the diverse US population presents unique implementation challenges. Potential solutions were detailed by informants. CONCLUSION: Identifying individual and thematic barriers to preconception RGCS delivery may help to define strategies to alleviate obstacles.

PURPOSE: Following disclosure of pathogenic or likely pathogenic variants in hereditary cancer genes, patients face cancer risk management decisions. Through this mixed-methods study, we investigated cancer risk management decisions among females with pathogenic or likely pathogenic variants in PALB2, CHEK2, and ATM to understand why some patients follow National Comprehensive Cancer Network guidelines, whereas others do not. METHODS: Survey and interview data were cross-analyzed using a 3-stage approach. Identified factors were used to conduct coincidence analysis and differentiate between combinations of factors that result in following or not following guidelines. RESULTS: Of the 13 participants who underwent guideline inconsistent prophylactic surgery, 12 fit 1 of 3 unique patterns: (1) cancer-related anxiety in the absence of trust in care, (2) provider recommending surgery inconsistent with National Comprehensive Cancer Network guidelines, or (3) surgery occurring before genetic testing. Two unique patterns were found among 18 of 20 participants who followed guidelines: (1) anxiety along with trust in care or (2) lack of anxiety and no prophylactic surgery before testing. CONCLUSION: Health care provider recommendations and trust in care may influence whether individuals receive care that is congruent with risk levels conferred by specific genes. Interventions are needed to improve provider knowledge, patient trust in non-surgical care, and patient anxiety.

PURPOSE: Zellweger spectrum disorders (ZSDs) are known as autosomal recessive disorders caused by defective peroxisome biogenesis due to bi-allelic pathogenic variants in any of at least 13 different PEX genes. Here, we report 2 unrelated patients who present with an autosomal dominant ZSD. METHODS: We performed biochemical and genetic studies in blood and skin fibroblasts of the patients and demonstrated the pathogenicity of the identified PEX14 variants by functional cell studies. RESULTS: We identified 2 different single heterozygous de novo variants in the PEX14 genes of 2 patients diagnosed with ZSD. Both variants cause messenger RNA mis-splicing, leading to stable expression of similar C-terminally truncated PEX14 proteins. Functional studies indicated that the truncated PEX14 proteins lost their function in peroxisomal matrix protein import and cause increased degradation of peroxisomes, ie, pexophagy, thus exerting a dominant-negative effect on peroxisome functioning. Inhibition of pexophagy by different autophagy inhibitors or genetic knockdown of the peroxisomal autophagy receptor NBR1 resulted in restoration of peroxisomal functions in the patients' fibroblasts. CONCLUSION: Our finding of an autosomal dominant ZSD expands the genetic repertoire of ZSDs. Our study underscores that single heterozygous variants should not be ignored as possible genetic cause of diseases with an established autosomal recessive mode of inheritance.

PURPOSE: To assess the relative cost-effectiveness of genomic testing compared with standard non-genomic diagnostic investigations in patients with suspected monogenic kidney disease from an Australian health care system perspective. METHODS: Diagnostic and clinical information was used from a national cohort of 349 participants. Simulation modelling captured diagnostic, health, and economic outcomes during a time horizon from clinical presentation until 3 months post-test results based on the outcome of cost per additional diagnosis and lifetime horizon based on cost per quality-adjusted life-year (QALY) gained. RESULTS: Genomic testing was Australian dollars (AU$) 1600 more costly per patient and led to an additional 27 diagnoses out of a 100 individuals tested, resulting in an incremental cost-effectiveness ratio of AU$5991 per additional diagnosis. Using a lifetime horizon, genomic testing resulted in an additional cost of AU$438 and 0.04 QALYs gained per individual compared with standard diagnostic investigations, corresponding to an incremental cost-effectiveness ratio of AU$10,823 per QALY gained. Sub-group analyses identified that the results were largely driven by the cost-effectiveness in glomerular diseases. CONCLUSION: Based on established or expected thresholds of cost-effectiveness, our evidence suggests that genomic testing is very likely to be cost saving for individuals with suspected glomerular diseases, whereas no evidence of cost-effectiveness was found for non-glomerular diseases.

PURPOSE: The limited evidence available on the cost-effectiveness (CE) of expanded carrier screening (ECS) prevents its widespread use in most countries, including Italy. Herein, we aimed to estimate the CE of 3 ECS panels (ie, American College of Medical Genetics and Genomics [ACMG] Tier 1 screening, "Focused Screening," testing 15 severe, highly penetrant conditions, and ACMG Tier 3 screening) compared with no screening, the health care model currently adopted in Italy. METHODS: The reference population consisted of Italian couples seeking pregnancy with no increased personal/familial genetic risk. The CE model was developed from the perspective of the Italian universal health care system and was based on the following assumptions: 100% sensitivity of investigated screening strategies, 77% intervention rate of at-risk couples (ARCs), and no risk to conceive an affected child by risk-averse couples opting for medical interventions. RESULTS: The incremental CE ratios generated by comparing each genetic screening panel with no screening were: -14,875 ± 1,208 €/life years gained (LYG) for ACMG1S, -106,863 ± 2,379 €/LYG for Focused Screening, and -47,277 ± 1,430 €/LYG for ACMG3S. ACMG1S and Focused Screening were dominated by ACMG3S. The parameter uncertainty did not significantly affect the outcome of the analyses. CONCLUSION: From a universal health care system perspective, all the 3 ECS panels considered in the study would be more cost-effective than no screening.

PURPOSE: Germline variants in POT1 have been implicated in predisposition to melanoma, sarcoma, and glioma in limited studies. Here, we determine the prevalence of cancer types in individuals with POT1 pathogenic variants (PVs) undergoing multigene panel testing (MGPT) for a broad variety of cancer indications. METHODS: We performed a retrospective review of data provided on clinical documents from individuals with POT1 PVs identified via MGPT over a 5-year period. Tumor prevalence in POT1 PV heterozygotes was compared with MGPT-negative wild-type (WT) controls using χ2 test. RESULTS: POT1 PVs were identified in 227 individuals. POT1 PV and WT (n = 13,315) cohorts had a similar proportion of reported tumors (69.6% and 69.2%, respectively); however, POT1 PV heterozygotes were more likely to be diagnosed with multiple tumors (18.9% vs 8.7%; P < .001). Compared with POT1 WT, we identified a significant increase in melanoma (odds ratio 7.03; 95% CI 4.7-10.5; P < .001) and sarcoma (odds ratio 6.6; 95% CI 3.1-13.9; P < .001). CONCLUSION: This analysis of the largest POT1 PV cohort to date validates the inclusion of POT1 in hereditary cancer MGPT and has the potential to impact clinical management recommendations, particularly for patients and families at risk for melanoma and sarcoma.

PURPOSE: Although the role of CHEK2 germline pathogenic variants in cancer predisposition is well known, resources for managing CHEK2 heterozygotes in clinical practice are limited. METHODS: An international workgroup developed guidance on clinical management of CHEK2 heterozygotes informed by peer-reviewed publications from PubMed. RESULTS: Although CHEK2 is considered a moderate penetrance gene, cancer risks may be considered as a continuous variable, which are influenced by family history and other modifiers. Consequently, early cancer detection and prevention for CHEK2 heterozygotes should be guided by personalized risk estimates. Such estimates may result in both downgrading lifetime breast cancer risks to those similar to the general population or upgrading lifetime risk to a level at which CHEK2 heterozygotes are offered high-risk breast surveillance according to country-specific guidelines. Risk-reducing mastectomy should be guided by personalized risk estimates and shared decision making. Colorectal and prostate cancer surveillance should be considered based on assessment of family history. For CHEK2 heterozygotes who develop cancer, no specific targeted medical treatment is recommended at this time. CONCLUSION: Systematic prospective data collection is needed to establish the spectrum of CHEK2-associated cancer risks and to determine yet-unanswered questions, such as the outcomes of surveillance, response to cancer treatment, and survival after cancer diagnosis.

Genome sequencing can generate findings beyond the initial test indication that may be relevant to a patient or research participant's health. In the decade since the American College of Medical Genetics and Genomics published its recommendations for reporting these findings, consensus regarding terminology has remained elusive and a variety of terms are in use globally. We conducted a scoping review to explore terminology choice and the justifications underlying those choices. Documents were included if they contained a justification for their choice of term(s) related to findings beyond the initial genomic test indication. From 3571 unique documents, 52 were included, just over half of which pertained to the clinical context (n = 29, 56%). We identified four inter-related concepts used to defend or oppose terms: expectedness of the finding, effective communication, relatedness to the original test indication, and how genomic information was generated. A variety of justifications were used to oppose the term "incidental," whereas "secondary" had broader support as a term to describe findings deliberately sought. Terminology choice would benefit from further work to include the views of patients. We contend that clear definitions will improve ethical debate and support communication about genomic findings beyond the initial test indication.

PURPOSE: Biallelic variants in TARS2, encoding the mitochondrial threonyl-tRNA-synthetase, have been reported in a small group of individuals displaying a neurodevelopmental phenotype but with limited neuroradiological data and insufficient evidence for causality of the variants. METHODS: Exome or genome sequencing was carried out in 15 families. Clinical and neuroradiological evaluation was performed for all affected individuals, including review of 10 previously reported individuals. The pathogenicity of TARS2 variants was evaluated using in vitro assays and a zebrafish model. RESULTS: We report 18 new individuals harboring biallelic TARS2 variants. Phenotypically, these individuals show developmental delay/intellectual disability, regression, cerebellar and cerebral atrophy, basal ganglia signal alterations, hypotonia, cerebellar signs, and increased blood lactate. In vitro studies showed that variants within the TARS2301-381 region had decreased binding to Rag GTPases, likely impairing mTORC1 activity. The zebrafish model recapitulated key features of the human phenotype and unraveled dysregulation of downstream targets of mTORC1 signaling. Functional testing of the variants confirmed the pathogenicity in a zebrafish model. CONCLUSION: We define the clinico-radiological spectrum of TARS2-related mitochondrial disease, unveil the likely involvement of the mTORC1 signaling pathway as a distinct molecular mechanism, and establish a TARS2 zebrafish model as an important tool to study variant pathogenicity.

PURPOSE: RPH3A encodes a protein involved in the stabilization of GluN2A subunit of N-methyl-D-aspartate (NMDA)-type glutamate receptors at the cell surface, forming a complex essential for synaptic plasticity and cognition. We investigated the effect of variants in RPH3A in patients with neurodevelopmental disorders. METHODS: By using trio-based exome sequencing, GeneMatcher, and screening of 100,000 Genomes Project data, we identified 6 heterozygous variants in RPH3A. In silico and in vitro models, including rat hippocampal neuronal cultures, have been used to characterize the effect of the variants. RESULTS: Four cases had a neurodevelopmental disorder with untreatable epileptic seizures [p.(Gln73His)dn; p.(Arg209Lys); p.(Thr450Ser)dn; p.(Gln508His)], and 2 cases [p.(Arg235Ser); p.(Asn618Ser)dn] showed high-functioning autism spectrum disorder. Using neuronal cultures, we demonstrated that p.(Thr450Ser) and p.(Asn618Ser) reduce the synaptic localization of GluN2A; p.(Thr450Ser) also increased the surface levels of GluN2A. Electrophysiological recordings showed increased GluN2A-dependent NMDA ionotropic glutamate receptor currents for both variants and alteration of postsynaptic calcium levels. Finally, expression of the Rph3AThr450Ser variant in neurons affected dendritic spine morphology. CONCLUSION: Overall, we provide evidence that missense gain-of-function variants in RPH3A increase GluN2A-containing NMDA ionotropic glutamate receptors at extrasynaptic sites, altering synaptic function and leading to a clinically variable neurodevelopmental presentation ranging from untreatable epilepsy to autism spectrum disorder.