Expanded phenotypic spectrum of neurodevelopmental and neurodegenerative disorder Bryant-Li-Bhoj syndrome with 38 additional individuals.

Bryant-Li-Bhoj syndrome (BLBS), which became OMIM-classified in 2022 (OMIM: 619720, 619721), is caused by germline variants in the two genes that encode histone H3.3 (H3-3A/H3F3A and H3-3B/H3F3B) [1-4]. This syndrome is characterized by developmental delay/intellectual disability, craniofacial anomalies, hyper/hypotonia, and abnormal neuroimaging [1, 5]. BLBS was initially categorized as a progressive neurodegenerative syndrome caused by de novo heterozygous variants in either H3-3A or H3-3B [1-4]. Here, we analyze the data of the 58 previously published individuals along 38 unpublished, unrelated individuals. In this larger cohort of 96 people, we identify causative missense, synonymous, and stop-loss variants. We also expand upon the phenotypic characterization by elaborating on the neurodevelopmental component of BLBS. Notably, phenotypic heterogeneity was present even amongst individuals harboring the same variant. To explore the complex phenotypic variation in this expanded cohort, the relationships between syndromic phenotypes with three variables of interest were interrogated: sex, gene containing the causative variant, and variant location in the H3.3 protein. While specific genotype-phenotype correlations have not been conclusively delineated, the results presented here suggest that the location of the variants within the H3.3 protein and the affected gene (H3-3A or H3-3B) contribute more to the severity of distinct phenotypes than sex. Since these variables do not account for all BLBS phenotypic variability, these findings suggest that additional factors may play a role in modifying the phenotypes of affected individuals. Histones are poised at the interface of genetics and epigenetics, highlighting the potential role for gene-environment interactions and the importance of future research.

Lessons from two series by physicians and caregivers' self-reported data in DDX3X-related disorders.

INTRODUCTION AND METHODS: We report two series of individuals with DDX3X variations, one (48 individuals) from physicians and one (44 individuals) from caregivers. RESULTS: These two series include several symptoms in common, with fairly similar distribution, which suggests that caregivers' data are close to physicians' data. For example, both series identified early childhood symptoms that were not previously described: feeding difficulties, mean walking age, and age at first words. DISCUSSION: Each of the two datasets provides complementary knowledge. We confirmed that symptoms are similar to those in the literature and provides more details on feeding difficulties. Caregivers considered that the symptom attention-deficit/hyperactivity disorder were most worrisome. Both series also reported sleep disturbance. Recently, anxiety has been reported in individuals with DDX3X variants. We strongly suggest that attention-deficit/hyperactivity disorder, anxiety, and sleep disorders need to be treated.

Spliceosome malfunction causes neurodevelopmental disorders with overlapping features.

Pre-mRNA splicing is a highly coordinated process. While its dysregulation has been linked to neurological deficits, our understanding of the underlying molecular and cellular mechanisms remains limited. We implicated pathogenic variants in U2AF2 and PRPF19, encoding spliceosome subunits in neurodevelopmental disorders (NDDs), by identifying 46 unrelated individuals with 23 de novo U2AF2 missense variants (including 7 recurrent variants in 30 individuals) and 6 individuals with de novo PRPF19 variants. Eight U2AF2 variants dysregulated splicing of a model substrate. Neuritogenesis was reduced in human neurons differentiated from human pluripotent stem cells carrying two U2AF2 hyper-recurrent variants. Neural loss of function (LoF) of the Drosophila orthologs U2af50 and Prp19 led to lethality, abnormal mushroom body (MB) patterning, and social deficits, which were differentially rescued by wild-type and mutant U2AF2 or PRPF19. Transcriptome profiling revealed splicing substrates or effectors (including Rbfox1, a third splicing factor), which rescued MB defects in U2af50-deficient flies. Upon reanalysis of negative clinical exomes followed by data sharing, we further identified 6 patients with NDD who carried RBFOX1 missense variants which, by in vitro testing, showed LoF. Our study implicates 3 splicing factors as NDD-causative genes and establishes a genetic network with hierarchy underlying human brain development and function.

A new patient with congenital myasthenic syndrome type 20 due to compound heterozygous missense SLC5A7 variants suggests trends in genotype-phenotype correlation.

BACKGROUND: Congenital myasthenic syndromes (CMSs) are characterized by hypotonia, episodic apnea, muscle weakness, ptosis and generalized fatigability. CMS type 20 (CMS20) is a rare disorder caused by variants in SLC5A7. In contrast to most other CMSs, CMS20 is also associated with neurodevelopmental disorders (NDDs). Only 19 patients from 14 families have been reported so far. METHODS: We studied a 12-year-old boy with symptoms manifested at six weeks of age. Later, he also showed speech delay, moderate intellectual disability and autism. Analysis of CMS genes known at the time of clinical diagnosis yielded no results. Trio exome sequencing (ES) was performed. RESULTS: ES revealed compound heterozygosity for two SLC5A7 variants, p.(Asn431Lys) and p.(Ile291Thr). While the first variant was absent from all databases, the second variant has already been described in one patient. In silico analysis of known pathogenic SLC5A7 variants showed that variants with a higher predicted deleteriousness may be associated with earlier onset and increased severity of neuromuscular manifestations. CONCLUSION: Our patient confirms that CMS20 can be associated with NDDs. The study illustrates the strength of ES in deciphering the genetic basis of rare diseases, contributes to characterization of CMS20 and suggests trends in genotype-phenotype correlation in CMS20.

Missense variants in DPYSL5 cause a neurodevelopmental disorder with corpus callosum agenesis and cerebellar abnormalities.

The collapsin response mediator protein (CRMP) family proteins are intracellular mediators of neurotrophic factors regulating neurite structure/spine formation and are essential for dendrite patterning and directional axonal pathfinding during brain developmental processes. Among this family, CRMP5/DPYSL5 plays a significant role in neuronal migration, axonal guidance, dendrite outgrowth, and synapse formation by interacting with microtubules. Here, we report the identification of missense mutations in DPYSL5 in nine individuals with brain malformations, including corpus callosum agenesis and/or posterior fossa abnormalities, associated with variable degrees of intellectual disability. A recurrent de novo p.Glu41Lys variant was found in eight unrelated patients, and a p.Gly47Arg variant was identified in one individual from the first family reported with Ritscher-Schinzel syndrome. Functional analyses of the two missense mutations revealed impaired dendritic outgrowth processes in young developing hippocampal primary neuronal cultures. We further demonstrated that these mutations, both located in the same loop on the surface of DPYSL5 monomers and oligomers, reduced the interaction of DPYSL5 with neuronal cytoskeleton-associated proteins MAP2 and ßIII-tubulin. Our findings collectively indicate that the p.Glu41Lys and p.Gly47Arg variants impair DPYSL5 function on dendritic outgrowth regulation by preventing the formation of the ternary complex with MAP2 and ßIII-tubulin, ultimately leading to abnormal brain development. This study adds DPYSL5 to the list of genes implicated in brain malformation and in neurodevelopmental disorders.

Haploinsufficiency of PRR12 causes a spectrum of neurodevelopmental, eye, and multisystem abnormalities.

PURPOSE: Proline Rich 12 (PRR12) is a gene of unknown function with suspected DNA-binding activity, expressed in developing mice and human brains. Predicted loss-of-function variants in this gene are extremely rare, indicating high intolerance of haploinsufficiency. METHODS: Three individuals with intellectual disability and iris anomalies and truncating de novo PRR12 variants were described previously. We add 21 individuals with similar PRR12 variants identified via matchmaking platforms, bringing the total number to 24. RESULTS: We observed 12 frameshift, 6 nonsense, 1 splice-site, and 2 missense variants and one patient with a gross deletion involving PRR12. Three individuals had additional genetic findings, possibly confounding the phenotype. All patients had developmental impairment. Variable structural eye defects were observed in 12/24 individuals (50%) including anophthalmia, microphthalmia, colobomas, optic nerve and iris abnormalities. Additional common features included hypotonia (61%), heart defects (52%), growth failure (54%), and kidney anomalies (35%). PrediXcan analysis showed that phecodes most strongly associated with reduced predicted PRR12 expression were enriched for eye- (7/30) and kidney- (4/30) phenotypes, such as wet macular degeneration and chronic kidney disease. CONCLUSION: These findings support PRR12 haploinsufficiency as a cause for a novel disorder with a wide clinical spectrum marked chiefly by neurodevelopmental and eye abnormalities.

Large-scale targeted sequencing identifies risk genes for neurodevelopmental disorders.

Most genes associated with neurodevelopmental disorders (NDDs) were identified with an excess of de novo mutations (DNMs) but the significance in case-control mutation burden analysis is unestablished. Here, we sequence 63 genes in 16,294 NDD cases and an additional 62 genes in 6,211 NDD cases. By combining these with published data, we assess a total of 125 genes in over 16,000 NDD cases and compare the mutation burden to nonpsychiatric controls from ExAC. We identify 48 genes (25 newly reported) showing significant burden of ultra-rare (MAF < 0.01%) gene-disruptive mutations (FDR 5%), six of which reach family-wise error rate (FWER) significance (p < 1.25E-06). Among these 125 targeted genes, we also reevaluate DNM excess in 17,426 NDD trios with 6,499 new autism trios. We identify 90 genes enriched for DNMs (FDR 5%; e.g., GABRG2 and UIMC1); of which, 61 reach FWER significance (p < 3.64E-07; e.g., CASZ1). In addition to doubling the number of patients for many NDD risk genes, we present phenotype-genotype correlations for seven risk genes (CTCF, HNRNPU, KCNQ3, ZBTB18, TCF12, SPEN, and LEO1) based on this large-scale targeted sequencing effort.

Author Correction: Large-scale targeted sequencing identifies risk genes for neurodevelopmental disorders.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

A novel variant of C12orf4 in a consanguineous Armenian family confirms the etiology of autosomal recessive intellectual disability type 66 with delineation of the phenotype.

BACKGROUND: Intellectual disability (ID) is a feature of many rare diseases caused by thousands of genes. This genetic heterogeneity implies that pathogenic variants in a specific gene are found only in a small number of patients, and difficulties arise in the definition of prevailing genotype and characteristic phenotype associated with that gene. One of such very rare disorders is autosomal recessive ID type 66 (OMIM #618221) caused by defects in C12orf4. Up to now, six families have been reported with mostly truncating variants. The spectrum of the clinical phenotype was not emphasized in previous reports, and detailed phenotype was not always available from previous patients, especially from large cohort studies. METHODS: Exome sequencing was performed in a consanguineous Armenian family with two affected adult brothers. RESULTS: The patients carry a novel homozygous nonsense C12orf4 variant. The integration of previous data and phenotyping of the brothers indicate that the clinical picture of C12orf4 defects involves hypotonia in infancy, rather severe ID, speech impairment, and behavioral problems such as aggressiveness, unstable mood, and autistic features. Several other symptoms are more variable and less consistent. CONCLUSION: This rather nonsyndromic and nonspecific clinical picture implies that additional patients with C12orf4 defects will likely continue to be identified using the "genotype-first" approach, rather than based on clinical assessment. The phenotype needs further delineation in future reports.

[Neurofibromatosis von Recklinghausen type 1 (NF1) - clinical picture and molecular-genetics diagnostic]. / Neurofibromatosis von Recklinghausen typ 1 (NF1) - klinický obraz a molekulárne-genetická diagnostika.

Neurofibromatosis von Recklinghausen type 1 (NF1) is a multisystem, autosomal dominant hereditary neurocutaneous disease characterized by skin, central and peripheral nervous system , eyes , bone, endocrine, gastrointestinal and blood vessel wall involvement. It has an estimated frequency of 1 in 3000. Neurofibromatosis type 1 is caused by mutations in the large NF1 gene located on chromosome 17q11.2, encoding the cytoplasmic protein neurofibromin. It is expressed in multiple cell types but is highly expressed in Schwann cells, oligodendrocytes, neurons, astrocytes and leukocytes. Neurofibromin is known to act as a tumor suppressor via Ras-GTPase activation, which causes down-regulation of cellular signaling via the Ras/mitogen-activated protein kinase (MAPK) pathway. Failure of this function is associated with a tendency to form tumors which are histologically hamartomas as well as benign tumors. Tumors of the central nervous system include low-grade gliomas (pilocytic astrocytomas grade I), especially optic pathway gliomas. They are often clinically asymptomatic. Other intracranial tumors are in the brain stem and also elsewhere in the brain and spinal cord. Hydrocephalus may be a complication of NF1 gliomas or due to stenosis of the distal part of the aqueduct Silvii. Cutaneous and subcutaneous neurofibromas or plexiform neurofibromas are localized in the peripheral nervous system. Plexiform neurofibromas have a significant lifetime risk of malignancy. The clinical diagnosis of NF1 is defined by diagnostic criteria. The NF1 diagnosis is satisfied when at least two of the seven conditions are met. The method of direct DNA analysis of large NF1 gene (61 exons) is available. The results of studies of genotype - phenotype established few correlations. But predicting the disease by finding mutations is not currently possible. NF1 exhibits a wide range of variability of expression and complete penetrance, even within the same family. About half of cases are new mutations. The treatment of patients with neurofibromatosis is symptomatic. Central nervous system symptomatic low-grade gliomas are most often treated with chemotherapy. For plexiform neurofibromas surgical removal is currently the only treatment option.

The importance of advanced parental age in the origin of neurofibromatosis type 1.

Von Recklinghausen neurofibromatosis (NF1) is an autosomal dominant disorder with a prevalence about 1/3,000 (1/2,000-1/5,000 in various population-based studies). About 30-50% of cases are sporadic, resulting from a new mutation. NF1 is fully penetrant by mid-childhood, stigmata, and medical problems (neurological, dermatological, endocrine, ophthalmological, oncological) are highly variable. Advanced paternal age (APA) has been known to increase the risk of new germline mutations that contribute to the presence of a variety of genetic diseases in the human population. The trend in developed countries has been toward higher parental age due to various reasons. In a cross-sectional study, in two university hospital centers, data on parental age of 103 children (41 female) born between 1976 and 2005 with sporadic NF1 were analyzed. Parental age at birth was compared with the Czech general population matched to birth year. The mean NF1 sporadic case paternal age at birth was 32.0 years (95% CI 30.7-33.3 years) compared with 28.8 years (95% CI 28.6-29.1 years) in the general population (P < 0.001). The mean maternal age at birth was 27.4 years (95% CI 26.3-28.5 years) compared with 25.8 years (95% CI 25.5-26.0 years) in the general population (P < 0.05). The case-control difference in the father's age was higher than it was for the mother's age. Sporadic NF1 cases accounted for 35.6% of our entire NF1 cohort. We confirmed an association of advanced parental and particularly paternal age with the occurrence of sporadic NF1.

The TP53 gene promoter is not methylated in families suggestive of Li-Fraumeni syndrome with no germline TP53 mutations.

Germline TP53 mutations are found in only 70% of families with the Li-Fraumeni syndrome (LFS), and with an even lower frequency in families suggestive of LFS but not meeting clinical criteria of the syndrome. Despite intense efforts, to date, no other genes have been associated with the disorder in a significant number of TP53 mutation-negative families. A search for defects in TP53 other than heterozygous missense mutations showed that neither intron variants nor sequence variants in the TP53 promoter are frequent in LFS, and multiexon deletions have been found to be responsible for LFS only in several cases. Another cancer predisposition syndrome, hereditary non-polyposis colon cancer, has been associated with epigenetic silencing of one allele of the MLH1 or MSH2 genes. This prompted us to test the methylation of the TP53 gene promoter in a set of 14 families suggestive of LFS using bisulphite sequencing of three DNA fragments from the 5' region of the gene. We found no detectable methylation at any of the CG dinucleotides tested. Thus, epigenetic silencing of the TP53 promoter is not a frequent cause of the disorder in families suggestive of LFS but with no germline mutations in the coding part of the gene.

Mid-aortic syndrome with renovascular hypertension and multisystem involvement in a girl with familiar neurofibromatosis von Recklinghausen type 1.

OBJECTIVES: Neurofibromatosis von Recklinghausen type 1 (NF1) is an autosomal dominant neurocutaneous disorder affecting one in 3 000-4 000 individuals. Mid-aortic syndrome (MAS) is a rare condition characterized by segmental narrowing of abdominal aorta and stenosis of its major branches - mainly renal arteries, including manifestation of renovascular hypertension. MAS can be caused by different diseases, including NF1. MAIN FINDINGS: A 9 years old girl with primary diagnosis of NF1 combined with renovascular hypertension due to MAS, suffered of bilateral optic and chiasm glioma, pubertas praecox, speech disorder, light mental retardation and scoliosis. We have found a mutation in exone 34 of the NF1 gene (17q11.2). Her father has been also diagnosed with NF1 and hypertension developed at early age. He has the same mutation in exone 34 of NF1 gene. The girl is currently treated with conservative antihypertensive medication with positive effect. Bilateral optic and chiasm glioma are asymptomatic at the time and they had been without progress over period of time. Any vascular surgery, neurosurgical and oncological therapy are not indicated at the present time. CONCLUSION: This article is a summary of clinical findings in patient with NF1 due to NF1 gene mutation in exone 34. It confirms the importance of complex multidisciplinar approach to examination and taking care of NF1 patients and their families.

Novel mutations in the NF1 gene in Czech patients with neurofibromatosis type 1.

Neurofibromatosis type 1 (NF1) is one of the most common inherited human disorders, with an estimated incidence of 1 per 3500 births. In most cases, the disease is caused either by mutation in the NF1 gene, or by a particular or complete deletion of the NF1 gene. The NF1 gene exhibits one of the highest mutation rates of any human disorder. In this experimental study of the NF1 gene, we screened the mutational spectrum of 22 unrelated patients from the Czech Republic using the denaturing high-performance liquid chromatography (DHPLC) and multiplex ligation-dependent probe amplification (MLPA) methods. We found NF1 mutations in 17 patients: 15 causal mutations were detected with the use of the DHPLC method (15/20, 75%). With the MPLA method, we also confirmed and specified two large deletions that were previously genotyped by microsatellite markers. Twelve of the above-mentioned mutations were newly found: c.1_2delATinsCC, c.1185+1G>C, c.1757_1760delCTAG, c.1642-7A>G, c.2329 T>G, c.2816delA, c.3738_3741delGTTT, c.4733 C>T, c.5220delT, c.6473_6474insGAAG, ex14_49del, ex28_49del. We present this study as a first effectual step in the routine diagnosis of the NF1 in patients from the Czech Republic.

A girl with neurofibromatosis type 1, atypical autism and mosaic ring chromosome 17.

We describe a girl with neurofibromatosis type 1 (NF1), mild dysmorphic features, growth and mental retardation, autism, and mosaicism of ring chromosome 17 and chromosome 17 monosomy. The extent of genetic material deleted from the ring chromosome was determined using a combination of classical cytogenetics, fluorescence in situ hybridization (FISH) and multiplex ligation-dependent probe amplification (MLPA) to be 0.6-2.5 Mb on 17p, and up to about 10 Mb on 17q. Based on our observations and on a review of the literature we argue that in addition to a universal "ring syndrome" which is based on ring instability and is less specific for the chromosome involved, various ring chromosomes underlie their own characteristic phenotypes. We propose that the symptoms leading to the diagnosis of NF1 in our patient could be attributed to mosaic hemizygosity for the NF1 gene in some of her somatic cells. A similar mechanism or a direct involvement of respective disease genes in the aberration could possibly influence also the development of autism and other symptoms. We raise a question if the loss of one copy of chromosome 17 from a substantial fraction of somatic cells can have specific consequences also for future risks of the patient, for example, due to the mosaic hemizygosity for the BRCA1 and TP53 genes.

Identification of five new families strengthens the link between childhood choroid plexus carcinoma and germline TP53 mutations.

We present five families of paediatric patients suffering from choroid plexus carcinoma in which we found germline TP53 mutations. Only one of the families conformed to the criteria of Li-Fraumeni syndrome and only three (including the Li-Fraumeni syndrome family) met the Chompret criteria for germline TP53 mutation testing. In the remaining two families no family history of cancer was identified and/or the parents of the patient were shown not to carry the mutation. Our results give further support to the notion that the occurrence of this rare paediatric tumour, especially in combination with a positive family history of cancer, but possibly also without any family history, may be an indicator of a germline TP53 mutation. The identification of this genetic defect has important consequences for cancer prevention and treatment in affected families.