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Introduction: Distinguishing paracentric inversions (PAIs) from chromosomal insertions has traditionally relied on fluorescent in situ hybridization (FISH) techniques, but recent advancements in high‐throughput sequencing have enabled the use of genome sequencing for such differentiation. In this study, we present a 38‐year‐old male carrier of a paracentric inversion on chromosome 2q, inv (2)(q31.2q34), whose partner experienced recurrent miscarriages. Material and Methods: FISH analysis confirmed the inversion, and genome sequencing was employed for detailed characterization. Results: Preimplantation genetic testing (PGT) revealed that all assessed embryos were balanced, consistent with the low risk of unbalanced offspring associated with PAIs. While PAI carriers traditionally exhibit low risk of producing unbalanced offspring, exceptions exist due to crossover events within the inversion loop. Although the sample size was limited, the findings align with existing sperm study data, supporting the rare occurrence of unbalanced progeny in PAI carriers. Conclusions: This study highlights the possibility of characterizing PAIs using genome sequencing to enable correct reproductive counseling and PGT decisions. Detailed characterization of a PAI is crucial for understanding potential outcomes and guiding PGT strategies, as accurate knowledge of the inversion size is essential for appropriate method selection in PGT. Given the very low risk of unbalanced offspring in PAI carriers, routine PGT may not be warranted but should be considered in specific cases with a history of unbalanced progeny or recurrent miscarriages. This study contributes to our understanding of PAI segregation and its implications for reproductive outcomes. [ABSTRACT FROM AUTHOR]

The sodium channel and clathrin linker 1 gene (SCLT1) has been involved in the pathogenesis of various ciliopathy disorders such as Bardet-Biedl syndrome, orofaciodigital syndrome type IX, and Senior-Løken syndrome. Detailed exams are warranted to outline all clinical features. Here, we present a family with a milder phenotype of SCLT1-related disease. Comprehensive eye examination including fundus images, OCT, color vision, visual fields and electroretinography were performed. Affected individuals were assessed by a pediatrician and a medical geneticist for systemic features of ciliopathy. Investigations included echocardiography, abdominal ultrasonography, blood work-up for diabetes, liver and kidney function. Genetic testing included NGS retinal dystrophy panel, segregation analysis and transcriptome sequencing. Two male children, age 10 and 8 years, were affected with attention deficit hyperactivity disorder (ADHD), obesity and mild photophobia. The ophthalmic exam revealed reduced best-corrected visual acuity (BCVA), strabismus, hyperopia, astigmatism and moderate red-green defects. Milder changes suggesting photoreceptors disease were found on retinal imaging. Electroretinogram confirmed cone photoreceptors dysfunction. Genetic testing revealed a homozygous likely pathogenic, splice-site variant in SCLT1 gene NM_144643.3: c.1439 + 1del in the proband and in the affected brother. The unaffected parents were heterozygous for the SCLT1 variant. Transcriptome sequencing showed retention of intron 16 in the proband. In this report, we highlight the importance of further extensive diagnostics in patients with unexplained reduced vision, strabismus, refractive errors and ADHD spectrum disorders. SCLT1-related retinal degeneration is very rare and isolated reduced function of cone photoreceptors has not previously been observed. [ABSTRACT FROM AUTHOR]

Molecular diagnostics is a cornerstone of modern precision medicine, broadly understood as tailoring an individual's treatment, follow‐up, and care based on molecular data. In rare diseases (RDs), molecular diagnoses reveal valuable information about the cause of symptoms, disease progression, familial risk, and in certain cases, unlock access to targeted therapies. Due to decreasing DNA sequencing costs, genome sequencing (GS) is emerging as the primary method for precision diagnostics in RDs. Several ongoing European initiatives for precision medicine have chosen GS as their method of choice. Recent research supports the role for GS as first‐line genetic investigation in individuals with suspected RD, due to its improved diagnostic yield compared to other methods. Moreover, GS can detect a broad range of genetic aberrations including those in noncoding regions, producing comprehensive data that can be periodically reanalyzed for years to come when further evidence emerges. Indeed, targeted drug development and repurposing of medicines can be accelerated as more individuals with RDs receive a molecular diagnosis. Multidisciplinary teams in which clinical specialists collaborate with geneticists, genomics education of professionals and the public, and dialogue with patient advocacy groups are essential elements for the integration of precision medicine into clinical practice worldwide. It is also paramount that large research projects share genetic data and leverage novel technologies to fully diagnose individuals with RDs. In conclusion, GS increases diagnostic yields and is a crucial step toward precision medicine for RDs. Its clinical implementation will enable better patient management, unlock targeted therapies, and guide the development of innovative treatments. [ABSTRACT FROM AUTHOR]

The majority of rare diseases are genetic, and regardless of advanced high-throughput genomics-based investigations, 60% of patients remain undiagnosed. A major factor limiting our ability to identify disease-causing alterations is a poor understanding of the morbid and normal human genome. A major genomic contributor of which function and distribution remain largely unstudied are the transposable elements (TE), which constitute 50% of our genome. Here we aim to resolve this knowledge gap and increase the diagnostic yield of rare disease patients investigated with clinical genome sequencing. To this end we characterized TE insertions in 1000 Swedish individuals from the SweGen dataset and 2504 individuals from the 1000 Genomes Project (1KGP), creating seven population-specific TE insertion databases. Of note, 66% of TE insertions in SweGen were present at >1% in the 1KGP databases, proving that most insertions are common across populations. Focusing on the rare TE insertions, we show that even though ~0.7% of those insertions affect protein coding genes, they rarely affect known disease casing genes (<0.1%). Finally, we applied a TE insertion identification workflow on two clinical cases where disease causing TE insertions were suspected and could verify the presence of pathogenic TE insertions in both. Altogether we demonstrate the importance of TE insertion detection and highlight possible clinical implications in rare disease diagnostics. [ABSTRACT FROM AUTHOR]

Delta-catenin (CTNND2) is an adhesive junction associated protein belonging to the family of p120 catenins. The human gene is located on the short arm of chromosome 5, the region deleted in Cri-du-chat syndrome (OMIM #123450). Heterozygous loss of CTNND2 has been linked to a wide spectrum of neurodevelopmental disorders such as autism, schizophrenia, and intellectual disability. Here we studied how heterozygous loss of ctnnd2b affects zebrafish embryonic development, and larvae and adult behavior. First, we observed a disorganization of neuronal subtypes in the developing forebrain, namely the presence of ectopic isl1-expressing cells and a local reduction of GABA-positive neurons in the optic recess region. Next, using time-lapse analysis, we found that the disorganized distribution of is1l-expressing forebrain neurons resulted from an increased specification of Isl1:GFP neurons. Finally, we studied the swimming patterns of both larval and adult heterozygous zebrafish and observed an increased activity compared to wildtype animals. Overall, this data suggests a role for ctnnd2b in the differentiation cascade of neuronal subtypes in specific regions of the vertebrate brain, with repercussions in the animal’s behavior. [ABSTRACT FROM AUTHOR]

FOXC1 is a ubiquitously expressed forkhead transcription factor that plays a critical role during early development. Germline pathogenic variants in FOXC1 are associated with anterior segment dysgenesis and Axenfeld-Rieger syndrome (ARS, #602482), an autosomal dominant condition with ophthalmologic anterior segment abnormalities, high risk for glaucoma and extraocular findings including distinctive facial features, as well as dental, skeletal, audiologic, and cardiac anomalies. De Hauwere syndrome is an ultrarare condition previously associated with 6p microdeletions and characterized by anterior segment dysgenesis, joint instability, short stature, hydrocephalus, and skeletal abnormalities. Here, we report clinical findings of two unrelated adult females with FOXC1 haploinsufficiency who have ARS and skeletal abnormalities. Final molecular diagnoses of both patients were achieved using genome sequencing. Patient 1 had a complex rearrangement involving a 4.9 kB deletion including FOXC1 coding region (Hg19; chr6:1,609,721-1,614,709), as well as a 7 MB inversion (Hg19; chr6:1,614,710-8,676,899) and a second deletion of 7.1 kb (Hg19; chr6:8,676,900-8,684,071). Patient 2 had a heterozygous single nucleotide deletion, resulting in a frameshift and a premature stop codon in FOXC1 (NM&lowbar;001453.3): c.467del, p.(Pro156Argfs*25). Both individuals had moderate short stature, skeletal abnormalities, anterior segment dysgenesis, glaucoma, joint laxity, pes planovalgus, dental anomalies, hydrocephalus, distinctive facial features, and normal intelligence. Skeletal surveys revealed dolichospondyly, epiphyseal hypoplasia of femoral and humeral heads, dolichocephaly with frontal bossin gand gracile long bones. We conclude that haploinsufficiency of FOXC1 causes ARS and a broad spectrum of symptoms with variable expressivity that at its most severe end also includes a phenotype overlapping with De Hauwere syndrome. [ABSTRACT FROM AUTHOR]

Seckel syndrome is an ultrarare autosomal recessive genetically heterogenous condition characterized by intrauterine and postnatal growth restriction, proportionate severe short stature, severe microcephaly, intellectual disability, and distinctive facial features including a prominent nose. Up to now, 40 patients with molecularly confirmed Seckel syndrome have been reported with biallelic variants in nine genes: ATR, CENPJ, CEP63, CEP152, DNA2, NIN, NSMCE2, RBBP8, and TRAIP. Homozygosity for nonsense variant (c.129G>A, p.43*) in CEP63 was described in three cousins with microcephaly, short stature, mild to moderate intellectual disability and diagnoses of Seckel syndrome. Here, we report a second family with three siblings who are compound heterozygous for loss‐of‐function variants in CEP63, c.1125T>G, p.(Tyr375*) and c.595del, p.(Glu199Asnfs*11). All siblings present with microcephaly, prominent nose, and intellectual disability but only one has severe short stature. Two siblings have aggressive behavior, a feature previously not reported in Seckel syndrome. This report adds two novel truncating variants in CEP63 and extends the clinical knowledge on CEP63‐related conditions. [ABSTRACT FROM AUTHOR]

Background: Autoimmune Addison's disease (AAD) is the most common cause of primary adrenal insufficiency (PAI). Despite its exceptionally high heritability, tools to estimate disease susceptibility in individual patients are lacking. We hypothesized that polygenic risk score (PRS) for AAD could help investigate PAI pathogenesis in pediatric patients. Methods: We here constructed and evaluated a PRS for AAD in 1223 seropositive cases and 4097 controls. To test its clinical utility, we reevaluated 18 pediatric patients, whose whole genome we also sequenced. We next explored the individual PRS in more than 120 seronegative patients with idiopathic PAI. Results: The genetic susceptibility to AAD—quantified using PRS—was on average 1.5 standard deviations (SD) higher in patients compared with healthy controls (p < 2e − 16), and 1.2 SD higher in the young patients compared with the old (p = 3e − 4). Using the novel PRS, we searched for pediatric patients with strikingly low AAD susceptibility and identified cases of monogenic PAI, previously misdiagnosed as AAD. By stratifying seronegative adult patients by autoimmune comorbidities and disease duration we could delineate subgroups of PRS suggesting various disease etiologies. Conclusions: The PRS performed well for case‐control differentiation and susceptibility estimation in individual patients. Remarkably, a PRS for AAD holds promise as a means to detect disease etiologies other than autoimmunity. [ABSTRACT FROM AUTHOR]

Precision Medicine holds promise for helping us manage specific phenotypes of common diseases. For rare diseases such as hypospadias, DSD, and pediatric solid tumors, it can also reveal underlying risk factors and pathogenesis. Professors Ann Nordgren and Anna Lindstrand share their experiences in the development and ongoing initiatives of the Swedish national project on Precision Medicine and how it could change the care of pediatric urology patients. [ABSTRACT FROM AUTHOR]

Precision medicine has the potential to transform healthcare by moving from one-size-fits-all to personalised treatment and care. This transition has been greatly facilitated through new highthroughput sequencing technologies that can provide the unique molecular profile of each individual patient, along with the rapid development of targeted therapies directed to the Achilles heels of each disease. To implement precision medicine approaches in healthcare, many countries have adopted national strategies and initiated genomic/precision medicine initiatives to provide equal access to all citizens. In other countries, such as Sweden, this has proven more difficult due to regionally organised healthcare. Using a bottom-up approach, key stakeholders from academia, healthcare, industry and patient organisations joined forces and formed Genomic Medicine Sweden (GMS), a national infrastructure for the implementation of precision medicine across the country. To achieve this, Genomic Medicine Centres have been established to provide regionally distributed genomic services, and a national informatics infrastructure has been built to allow secure data handling and sharing. GMS has a broad scope focusing on rare diseases, cancer, pharmacogenomics, infectious diseases and complex diseases, while also providing expertise in informatics, ethical and legal issues, health economy, industry collaboration and education. In this review, we summarise our experience in building a national infrastructure for precision medicine. We also provide key examples how precision medicine already has been successfully implemented within our focus areas. Finally, we bring up challenges and opportunities associated with precision medicine implementation, the importance of international collaboration, as well as the future perspective in the field of precision medicine. [ABSTRACT FROM AUTHOR]

The pyruvate dehydrogenase complex (PDC) is responsible for the conversion of pyruvate into acetyl-CoA, which is used for energy conversion in cells. PDC activity is regulated by phosphorylation via kinases and phosphatases (PDK/PDP). Variants in all subunits of the PDC and in PDK3 have been reported, with varying phenotypes including lactic acidosis, neurodevelopmental delay, peripheral neuropathy, or seizures. Here, we report a de novo heterozygous missense variant in PDK1 (c.1139G > A; p.G380D) in a girl with developmental delay and early onset severe epilepsy. To investigate the role of PDK1G380D in energy metabolism and neuronal development, we used a zebrafish model. In zebrafish embryos we show a reduced number of cells with mitochondria with membrane potential, reduced movements, and a delay in neuronal development. Furthermore, we observe a reduction in the phosphorylation of PDH-E1α by PDKG380D, which suggests a disruption in the regulation of PDC activity. Finally, in patient fibroblasts, a mild reduction in the ratio of phosphorylated PDH over total PDH-E1α was detected. In summary, our findings support the notion that this aberrant PDK1 activity is the cause of clinical symptoms in the patient. [ABSTRACT FROM AUTHOR]

Prader–Willi syndrome (PWS; MIM# 176270) is a neurodevelopmental disorder caused by the loss of expression of paternally imprinted genes within the PWS region located on 15q11.2. It is usually caused by either maternal uniparental disomy of chromosome 15 (UPD15) or 15q11.2 recurrent deletion(s). Here, we report a healthy carrier of a balanced X;15 translocation and her two daughters, both with the karyotype 45,X,der(X)t(X;15)(p22;q11.2),−15. Both daughters display symptoms consistent with haploinsufficiency of the SHOX gene and PWS. We explored the architecture of the derivative chromosomes and investigated effects on gene expression in patient‐derived neural cells. First, a multiplex ligation‐dependent probe amplification methylation assay was used to determine the methylation status of the PWS‐region revealing maternal UPD15 in daughter 2, explaining her clinical symptoms. Next, short read whole genome sequencing and 10X genomics linked read sequencing was used to pinpoint the exact breakpoints of the translocation. Finally, we performed transcriptome sequencing on neuroepithelial stem cells from the mother and from daughter 1 and observed biallelic expression of genes in the PWS region (including SNRPN) in daughter 1. In summary, our multi‐omics analysis highlights two different PWS mechanisms in one family and provide an example of how structural variation can affect imprinting through long‐range interactions. [ABSTRACT FROM AUTHOR]

Balanced structural variants, such as reciprocal translocations, are sometimes hard to detect with sequencing, especially when the breakpoints are located in repetitive or insufficiently mapped regions of the genome. In such cases, long-range information is required to resolve the rearrangement, identify disrupted genes and, in symptomatic carriers, pinpoint the disease-causing mechanisms. Here, we report an individual with autism, epilepsy and osteoporosis and a de novo balanced reciprocal translocation: t(17;19) (p13;p11). The genomic DNA was analyzed by short-, linked- and long-read genome sequencing, as well as optical mapping. Transcriptional consequences were assessed by transcriptome sequencing of patient-specific neuroepithelial stem cells derived from induced pluripotent stem cells (iPSC). The translocation breakpoints were only detected by long-read sequencing, the first on 17p13, located between exon 1 and exon 2 of MINK1 (Misshapen-like kinase 1), and the second in the chromosome 19 centromere. Functional validation in induced neural cells showed that MINK1 expression was reduced by >50% in the patient's cells compared to healthy control cells. Furthermore, pathway analysis revealed an enrichment of changed neural pathways in the patient's cells. Altogether, our multi-omics experiments highlight MINK1 as a candidate monogenic disease gene and show the advantages of long-read genome sequencing in capturing centromeric translocations. [ABSTRACT FROM AUTHOR]

We describe two brothers with a recurrent truncating EIF2S3 variant and MEHMO (Mental retardation, Epileptic seizures, Hypogonadism and ‐genitalism, Microcephaly, Obesity). Both had the previously described facial dysmorphic features, microcephaly, developmental impairment, hypoglycemia, hypothyreosis, diabetes mellitus, epilepsy, hypertonus, obesity, and micropenis. Additionally, we describe hypothermia and reduced umbilical blood flow. [ABSTRACT FROM AUTHOR]

The amount of data available from genomic medicine has revolutionized the approach to identify the determinants underlying many rare diseases. The task of confirming a genotype–phenotype causality for a patient affected with a rare genetic disease is often challenging. In this context, the establishment of the Matchmaker Exchange (MME) network has assumed a pivotal role in bridging heterogeneous patient information stored on different medical and research servers. MME has made it possible to solve rare disease cases by "matching" the genotypic and phenotypic characteristics of a patient of interest with patient data available at other clinical facilities participating in the network. Here, we present PatientMatcher (https://github.com/Clinical-Genomics/patientMatcher), an open‐source Python and MongoDB‐based software solution developed by Clinical Genomics facility at the Science for Life Laboratory in Stockholm. PatientMatcher is designed as a standalone MME server, but can easily communicate via REST API with external applications managing genetic analyses and patient data. The MME node is being implemented in clinical routine in collaboration with the Genomic Medicine Center Karolinska at the Karolinska University Hospital. PatientMatcher is written to implement the MME API and provides several customizable settings, including a custom‐fit similarity score algorithm and adjustable matching results notifications. [ABSTRACT FROM AUTHOR]

Background: De novo variants are a common cause to rare intellectual disability syndromes, associated with low recurrence risk. However, when such variants occur pre‐zygotically in parental germ cells, the recurrence risk might be higher. Still, the recurrence risk estimates are mainly based on empirical data and the prevalence of germline mosaicism is often unknown. Methods: To establish the prevalence of mosaicism in parents of children with intellectual disability syndromes caused by de novo variants, we performed droplet digital PCR on DNA extracted from blood (43 trios), and sperm (31 fathers). Results: We detected low‐level mosaicism in sperm‐derived DNA but not in blood in the father of a child with Kleefstra syndrome caused by an EHMT1 variant. Additionally, we found a higher level of paternal mosaicism in sperm compared to blood in the father of a child with Gillespie syndrome caused by an ITPR1 variant. Conclusion: By employing droplet digital PCR, we detected paternal germline mosaicism in two intellectual disability syndromes. In both cases, the mosaicism level was higher in sperm than blood, indicating that analysis of blood alone may underestimate germline mosaicism. Therefore, sperm analysis can be clinically useful to establish the recurrence risk for parents and improve genetic counselling. [ABSTRACT FROM AUTHOR]

Context: Rare copy number variants (CNVs) have been associated with the development of severe obesity. However, the potential disease-causing contribution of individual genes within the region of CNVs is often not known. Objective: Screening of rare variants in genes involved in CNVs in Finnish patients with severe early-onset obesity to find candidate genes linked to severe obesity. Methods: Custom-made targeted exome sequencing panel to search for rare (minor allele frequency <0.1%) variants in genes affected by previously identified CNVs in 92 subjects (median age 14 years) with early-onset severe obesity (median body mass index (BMI) Z-score + 4.0). Results: We identified thirteen rare heterozygous variants of unknown significance in eleven subjects in twelve of the CNV genes. Two rare missense variants (p.Pro405Arg and p.Tyr232Cys) were found in SORCS1 , a gene highly expressed in the brain and previously linked to diabetes risk. Four rare variants were in genes in the proximal 16p11.2 region (a frameshift variant in TAOK2 and missense variants in SEZ6L2 , ALDOA and KIF22) and three rare missense variants were in genes in the 22q11.21 region (AIFM3, ARVCF and KLHL22). Conclusion: We report several rare variants in CNV genes in subjects with childhood obesity. However, the role of the individual genes in the previously identified rare CNVs to development of obesity remains uncertain. More studies are needed to understand the potential role of the specific genes within obesity associated CNVs. [ABSTRACT FROM AUTHOR]