Variants in BRSK2, encoding brain specific kinase-2, have recently been associated with an autosomal dominant neurodevelopmental disorder (NDD). We have assembled 52 cases with heterozygous BRSK2 variants and variable neurodevelopmental phenotypes with frequent neuropsychiatric and behavioral symptoms. The variant spectrum included 15 different truncating variants, seven (potential) splice variants, three structural variants, and 12 different missense variants. Of the missense variants, seven were in the kinase domain, and the others in the UBA and the KA1 domain or outside domains. Variants occurred de novo in 19 cases and were inherited in 18. We utilized Drosophila melanogaster as a model and assessed viability and performed climbing and bang sensitivity assays upon knockdown of the fly orthologue sff or upon overexpression of wildtype or mutant human BRSK2. Pan-neuronal knockdown of sff resulted in impaired locomotor behavior and seizure susceptibility. Ubiquitous or pan-neuronal overexpression of human wildtype BRSK2 in Drosophila resulted in lethality or locomotor impairment, respectively, indicating toxicity. Overexpressing mutant BRSK2 did not or incompletely affect viability and locomotor behavior for six of seven tested kinase domain missense variants and one KA1 domain variant, indicating a (partial) loss-of-function effect. Interestingly, overexpressing BRSK2 with the remaining missense variant from the kinase domain and the two most C-terminal missense variants resulted in possible gain of function. Our findings further delineate the clinical and molecular spectrum of BRSK2-associated NDD and provide further insights into the role of BRSK2/sff in nervous system function and dysfunction.

BACKGROUND:Pathogenic variants in the TRPC6 gene have been identified in families affected by adult-onset autosomal dominant focal segmental glomerulosclerosis (FSGS). Although the exact mechanisms leading to kidney disease remain unclear, growing evidence suggests a role of the TRPC6 channel not only in genetic forms of FSGS but also in acquired forms of glomerular diseases. This highlights TRPC6 as a promising target for therapeutic intervention. METHODS:This single-centre cohort study at the University Hospital in Bern, Switzerland, included patients from families with (likely) pathogenic TRPC6 variants. Patients' family history, as well as clinical and genetic data were obtained through interviews and medical records. The study aimed to analyse the renal and extra-renal disease phenotype, its evolution, and explore potential genotype-phenotype correlations. RESULTS:Nine individuals from four unrelated families were included. Most patients presented in adulthood with signs of structural nephropathy. Notably, the initial presentation involved sub-nephrotic range proteinuria rather than nephrotic syndrome, with progression to kidney failure over the course of several years. Four out of nine patients exhibited multi-organ (> 3) involvement with unclear genotype-phenotype correlation. Notably, among the four TRPC6 variants identified, we report a novel variant (p.(Trp680*)), which expands the current spectrum of TRPC6 mutations. Additionally, another variant (p.(Arg175Trp)) was associated with infantile onset of disease characterised by steroid-resistant nephrotic syndrome. CONCLUSION:This study contributes to a broader understanding of the genotype-phenotype variability in TRPC6-associated FSGS and expands the mutational spectrum by identifying a novel TRPC6 variant, underscoring the importance of genetic analysis in guiding patient prognosis and personalised management strategies.

CUL1 encodes a scaffolding protein of the SKP1-CUL1-F-box E3 ubiquitin ligase complex, which mediates substrate ubiquitination and proteasomal degradation. Despite CUL1’s essential roles, it has not been implicated in human disease. We identified ten unrelated individuals with a syndromic neurodevelopmental disorder, with or without movement abnormalities carrying de novo heterozygous CUL1 variants. Patient-derived iPSCs with p.Lys515Glu exhibited elevated cyclin E level, a CUL1 target. Co-transfection with CUL1 and ubiquitin demonstrated that truncating variants (p.Arg565* and p.Gly512Trpfs*51) impaired polyubiquitin chain formation on β-catenin, supporting a dominant-negative mechanism. In vivo , neural-specific knockdown of Cul1 in Drosophila reduced survival and motor function, while enhancing sensory dendrite regeneration. These phenotypes were differentially rescued by human CUL1 wild-type (WT), p.Leu671Val or truncating variants. WT CUL1 or p.Leu671Val failed to rescue the impaired social interaction in Cul1 knockdown flies, whereas the two truncating variants exacerbated the deficit. Overexpression of p.Arg565* and p.Gly512Trpfs*51 in WT flies recapitulated dendrite regeneration and social deficits, confirming their dominant-negative effects. Their overexpression also caused Akt overactivation, previously shown to be a Cul1 substrate and promote dendrite regeneration, implicating Akt as a downstream effector. These findings establish CUL1 as a novel neurodevelopmental disorder gene and suggest that dominant-negative mechanisms underlie its pathogenesis.

PURPOSE:Missense de novo variants in CACNA1G, which encodes the Cav3.1 T-type calcium channel, have been associated with a severe, early-onset form of cerebellar disorder with neurodevelopmental deficits (SCA42ND). We explored a large series of pediatric cases carrying heterozygous variants in CACNA1G to further characterize genotype-phenotype correlations in SCA42ND. METHODS:We describe 19 patients with congenital CACNA1G-variants, including 6 new heterozygotes of the recurrent SCA42ND variants, p.(Ala961Thr) and p.(Met1531Val), and 8 unreported variants, including 7 missense variants, mainly de novo. We carried out genetic and structural analyses of all variants. Patch-clamp recordings were performed to measure their channel activity. RESULTS:We provide a consolidated clinical description for the patients carrying p.(Ala961Thr) and p.(Met1531Val). The new variants associated with the more severe phenotypes are found in the Cav3.1 channel intracellular gate. Calcium currents of these Cav3.1 variants showed slow inactivation and deactivation kinetics and an increase in window current, supporting a gain of channel activity. On the contrary, the p.(Met197Arg) variant (IS4-S5 loop) resulted in a loss of channel activity. CONCLUSION:This detailed description of several de novo missense pathogenic variants in CACNA1G, including 13 previously reported cases, supports a clinical spectrum of congenital CACNA1G syndrome beyond spinocerebellar ataxia.

Nuclear envelopathies are rare genetic diseases that compromise the integrity of the nuclear envelope. Patients with a defect in LEM domain nuclear envelope protein 2 (LEMD2) leading to LEMD2-associated progeroid syndrome are exceedingly scarce in number, yet they exhibit shared clinical features including skeletal abnormalities and a prematurely-aged appearance. Our study broadens the understanding of LEMD2-associated progeroid syndrome by detailing its phenotypic and molecular characteristics in the first female and fourth reported case, highlighting a distinct impact on metabolic functions. The patient's history revealed growth delay, facial and skeletal abnormalities, and recurrent abdominal pain crises caused by hepatomegaly. Comparisons with the previously documented cases emphasized similarities in skeletal and facial features while showcasing unique variations, notably in cardiac and hepatic manifestations. In vitro experiments conducted on patient-derived peripheral blood and urinary epithelial cells and LEMD2-downregulated HepG2 cells confirmed abnormalities in the structure of the nuclear envelope in all three tissue-types. Overall, our work offers a comprehensive profile of a patient with LEMD2-related syndrome, emphasizing the hepatic involvement in the disease and broadening our understanding of clinical and molecular implications. This study not only contributes specific insights into LEMD2-related conditions but also underscores potential therapeutic paths for disorders affecting nuclear envelope dynamics.

Rothmund-Thomson syndrome (RTS) is a rare, heterogeneous autosomal recessive genodermatosis, with poikiloderma as its hallmark. It is classified into two types: type I, with biallelic variants in ANAPC1 and juvenile cataracts, and type II, with biallelic variants in RECQL4, increased cancer risk and no cataracts. We report on six Brazilian probands and two siblings of Swiss/Portuguese ancestry presenting with severe short stature, widespread poikiloderma and congenital ocular anomalies. Genomic and functional analysis revealed compound heterozygosis for a deep intronic splicing variant in trans with loss of function variants in DNA2, with reduction of the protein levels and impaired DNA double-strand break repair. The intronic variant is shared by all patients, as well as the Portuguese father of the European siblings, indicating a probable founder effect. Biallelic variants in DNA2 were previously associated with microcephalic osteodysplastic primordial dwarfism. Although the individuals reported here present a similar growth pattern, the presence of poikiloderma and ocular anomalies is unique. Thus, we have broadened the phenotypical spectrum of DNA2 mutations, incorporating clinical characteristics of RTS. Although a clear genotype-phenotype correlation cannot be definitively established at this moment, we speculate that the residual activity of the splicing variant allele could be responsible for the distinct manifestations of DNA2-related syndromes.

PURPOSE:Congenital hypogonadotropic hypogonadism (CHH) is a rare disorder resulting in absent puberty and infertility. The genetic architecture is complex with multiple loci involved, variable expressivity, and incomplete penetrance. The majority of cases are sporadic, consistent with a disease affecting fertility. The current study aims to investigate mosaicism as a genetic mechanism for CHH, focusing on de novo rare variants in CHH genes.METHODS:We evaluated 60 trios for de novo rare sequencing variants (RSV) in known CHH genes using exome sequencing. Potential mosaicism was suspected among RSVs with altered allelic ratios and confirmed using customized ultradeep sequencing (UDS) in multiple tissues.RESULTS:Among the 60 trios, 10 probands harbored de novo pathogenic variants in CHH genes. Custom UDS demonstrated that three of these de novo variants were in fact postzygotic mosaicism-two in FGFR1 (p.Leu630Pro and p.Gly348Arg), and one in CHD7 (p.Arg2428*). Statistically significant variation across multiple tissues (DNA from blood, buccal, hair follicle, urine) confirmed their mosaic nature.CONCLUSIONS:We identified a significant number of de novo pathogenic variants in CHH of which a notable number (3/10) exhibited mosaicism. This report of postzygotic mosaicism in CHH patients provides valuable information for accurate genetic counseling.

Sudden arrhythmic death syndrome (SADS) in young individuals is a devastating and tragic event often caused by an undiagnosed inherited cardiac disease. Although post-mortem genetic testing represents a promising tool to elucidate potential disease-causing mechanisms in such autopsy-negative death cases, a variant interpretation is still challenging, and functional consequences of identified sequence alterations often remain unclear. Recently, we have identified a novel heterozygous missense variant (N1774H) in the Na v 1.5 channel-encoding gene SCN5A in a 19-year-old female SADS victim. The aim of this study was to perform a co-segregation analysis in family members of the index case and to evaluate the functional consequences of this SCN5A variant. Functional characterization of the SCN5A N1774H variant was performed using patch-clamp techniques in TsA-201 cell line transiently expressing either wild-type or variant Na v 1.5 channels. Electrophysiological analyses revealed that variant Na v 1.5 channels show a loss-of-function in the peak current densities, but an increased late current compared to the wild-type channels, which could lead to both, loss- and gain-of-function respectively. Furthermore, clinical assessment and genetic testing of the relatives of the index case showed that all N1774H mutation carriers have prolonged QT intervals. The identification of several genotype and phenotype positive family members and the functional implication of the SCN5A N1774H variant support the evidence of the in silico predicted pathogenicity of the here reported sequence alteration.

Acrocallosal syndrome (ACLS) is an autosomal recessive neurodevelopmental disorder caused by KIF7 defects and belongs to the heterogeneous group of ciliopathies related to Joubert syndrome (JBTS). While ACLS is characterized by macrocephaly, prominent forehead, depressed nasal bridge, and hypertelorism, facial dysmorphism has not been emphasized in JBTS cohorts with molecular diagnosis. To evaluate the specificity and etiology of ACLS craniofacial features, we performed whole exome or targeted Sanger sequencing in patients with the aforementioned overlapping craniofacial appearance but variable additional ciliopathy features followed by functional studies. We found (likely) pathogenic variants of KIF7 in 5 out of 9 families, including the original ACLS patients, and delineated 1000 to 4000-year-old Swiss founder alleles. Three of the remaining families had (likely) pathogenic variants in the JBTS gene C5orf42, and one patient had a novel de novo frameshift variant in SHH known to cause autosomal dominant holoprosencephaly. In accordance with the patients' craniofacial anomalies, we showed facial midline widening after silencing of C5orf42 in chicken embryos. We further supported the link between KIF7, SHH, and C5orf42 by demonstrating abnormal primary cilia and diminished response to a SHH agonist in fibroblasts of C5orf42-mutated patients, as well as axonal pathfinding errors in C5orf42-silenced chicken embryos similar to those observed after perturbation of Shh signaling. Our findings, therefore, suggest that beside the neurodevelopmental features, macrocephaly and facial widening are likely more general signs of disturbed SHH signaling. Nevertheless, long-term follow-up revealed that C5orf42-mutated patients showed catch-up development and fainting of facial features contrary to KIF7-mutated patients.

We present a case of diaphanospondylodysostosis (DSD) which showed increased nuchal translucency at 1st trimester and missing ossification of the lower spine, short ribs with posterior gaps, and absent nasal bone in midtrimester. Autopsy revealed additionally bilateral nephroblastomatosis. Molecular genetic analysis showed a new mutation in the BMPER gene.

Vorstand der SGMG: Isabel Filgesa, Deborah Bartholdib, Sven Cichonc, Dunja Niedristd, Naomi Porrete, Anita Rauchf, Elisabeth Sallerg, Thomas von Känelh, Siv Fokstueni a PD Dr. med., Fachärztin für Medizinische Genetik, Spezialistin für medizinisch-genetische Analytik FAMH, Ärztliche Leiterin Medizinische Genetik, Institut für Medizinische Genetik und Pathologie, Universitätsspital und Universität Basel; b PD Dr.med., Fachärztin für Medizinische Genetik, Oberärztin Humangenetik, Universitätsklinik für Kinderheilkunde, Inselspital Bern; c Prof. Dr. sc. nat. Direktor Institut für Medizinische Genetik und Pathologie, Universitätsspital und Universität Basel; d Dr. med., Fachärztin für Medizinische Genetik, Institut für Medizinische Genetik, Universität Zürich; e Dr. sc. nat., Spezialistin für medizinisch-genetische Analytik FAMH, Laborleiterin Hämatologische Molekulare Diagnostik, Universitätsklinik für Hämatologie, Inselspital Bern; f Prof. Dr. med., Fachärztin für Medizinische Genetik, Spezialistin für medizinisch-genetische Analytik FAMH, Ordinaria Institut für Medizinische Genetik, Universität Zürich; g Dr. sc. nat., Spezialistin für medizinisch-genetische Analytik FAMH, Laborleiterin, Institut für medizinische & molekulare Diagnostik AG, Falkenstrasse 14, 8024 Zürich; h Dr. sc. nat., Spezialist für medizinisch-genetische Analytik FAMH, Chef du Service de Génétique Médicale, Hôpital du Valais, Sion, Co-Präsident SGMG; i PD Dr. med., Fachärztin für Medizinische Genetik, Médecin adjointe agrégée, Service de Médecine Génétique, Département de médecine génétique, de laboratoire et de pathologie, Hôpitaux Universitaires de Genève, Co-Präsidentin SGMG

Background/Purpose: Neuronal ceroid-lipofuscinoses (NCL) are a group of neurodegenerative disorders of variable clinical phenotype. We present a case of Northern Epilepsy caused by a newly described homozygous mutation in the CLN8 gene.

Searchable abstracts of presentations at key conferences in endocrinology ISSN 1470-3947 (print) | ISSN 1479-6848 (online)

Purpose Congenital hypogonadotropic hypogonadism (CHH), a rare genetic disease caused by gonadotropin-releasing hormone deficiency, can also be part of complex syndromes (e.g., CHARGE syndrome). CHD7 mutations were reported in 60% of patients with CHARGE syndrome, and in 6% of CHH patients. However, the definition of CHD7 mutations was variable, and the associated CHARGE signs in CHH were not systematically examined. Methods Rare sequencing variants (RSVs) in CHD7 were identified through exome sequencing in 116 CHH probands, and were interpreted according to American College of Medical Genetics and Genomics guidelines. Detailed phenotyping was performed in CHH probands who were positive for CHD7 RSVs, and genotype–phenotype correlations were evaluated. Results Of the CHH probands, 16% (18/116) were found to harbor heterozygous CHD7 RSVs, and detailed phenotyping was performed in 17 of them. Of CHH patients with pathogenic or likely pathogenic CHD7 variants, 80% (4/5) were found to exhibit multiple CHARGE features, and 3 of these patients were reclassified as having CHARGE syndrome. In contrast, only 8% (1/12) of CHH patients with nonpathogenic CHD7 variants exhibited multiple CHARGE features ( P = 0.01). Conclusion Pathogenic or likely pathogenic CHD7 variants rarely cause isolated CHH. Therefore a detailed clinical investigation is indicated to clarify the diagnosis (CHH versus CHARGE) and to optimize clinical management.

We report a case of torsades de pointes arrhythmia as the first manifestation of congenital Long QT syndrome in a 77‐year‐old man with family history of sudden unexplained death. This case illustrates the importance of vigilant clinical assessment and genetic counseling in families with sudden death in order to identify properly asymptomatic relatives at risk for cardiac events. It also demonstrates that Long QT syndrome can still manifest with potentially fatal arrhythmias late in life in previously asymptomatic elderly patients.

Background: We report two novel splice region mutations in OPA1 in two unrelated families presenting with autosomal-dominant optic atrophy type 1 (ADOA1) (ADOA or Kjer type optic atrophy). Mutations in OPA1 encoding a mitochondrial inner membrane protein are a major cause of ADOA.Methods: We analyzed two unrelated families including four affected individuals clinically suspicious of ADOA. Standard ocular examinations were performed in affected individuals of both families. All coding exons, as well as exon-intron boundaries of the OPA1 gene were sequenced. In addition, multiplex ligation-dependent probe amplification (MLPA) was performed to uncover copy number variations in OPA1. mRNA processing was monitored using RT-PCR and subsequent cDNA analysis.Results: We report two novel splice region mutations in OPA1 in two unrelated individuals and their affected relatives, which were previously not described in the literature. In one family the heterozygous insertion and deletion c.[611-37_611-38insACTGGAGAATGTAAAGGGCTTT; 611-6_611-16delCATATTTATCT] was found in all investigated family members leading to the activation of an intronic cryptic splice site. In the second family sequencing of OPA1 disclosed a de novo heterozygous deletion c. 2012+4_2012+7delAGTA resulting in exon 18 and 19 skipping, which was not detected in healthy family members.Conclusion: We identified two novel intronic mutations in OPA1 affecting the correct OPA1 pre-mRNA splicing, which was confirmed by OPA1 cDNA analysis. This study shows the importance of transcript analysis to determine the consequences of unclear intronic mutations in OPA1 in proximity to the intron-exon boundaries.

Lissencephaly is a malformation of cortical development typically caused by deficient neuronal migration resulting in cortical thickening and reduced gyration. Here we describe a "thin" lissencephaly (TLIS) variant characterized by megalencephaly, frontal predominant pachygyria, intellectual disability, and seizures. Trio-based whole-exome sequencing and targeted re-sequencing identified recessive mutations of CRADD in six individuals with TLIS from four unrelated families of diverse ethnic backgrounds. CRADD (also known as RAIDD) is a death-domain-containing adaptor protein that oligomerizes with PIDD and caspase-2 to initiate apoptosis. TLIS variants cluster in the CRADD death domain, a platform for interaction with other death-domain-containing proteins including PIDD. Although caspase-2 is expressed in the developing mammalian brain, little is known about its role in cortical development. CRADD/caspase-2 signaling is implicated in neurotrophic factor withdrawal- and amyloid-beta-induced dendritic spine collapse and neuronal apoptosis, suggesting a role in cortical sculpting and plasticity. TLIS-associated CRADD variants do not disrupt interactions with caspase-2 or PIDD in co-immunoprecipitation assays, but still abolish CRADD's ability to activate caspase-2, resulting in reduced neuronal apoptosis in vitro. Homozygous Cradd knockout mice display megalencephaly and seizures without obvious defects in cortical lamination, supporting a role for CRADD/caspase-2 signaling in mammalian brain development. Megalencephaly and lissencephaly associated with defective programmed cell death from loss of CRADD function in humans implicate reduced apoptosis as an important pathophysiological mechanism of cortical malformation. Our data suggest that CRADD/caspase-2 signaling is critical for normal gyration of the developing human neocortex and for normal cognitive ability.