De novo variants in FRYL are associated with developmental delay, intellectual disability, and dysmorphic features

FRY-like transcription coactivator (FRYL) belongs to a Furry protein family that is evolutionarily conserved from yeast to humans. The functions of FRYL in mammals are largely unknown, and variants in FRYL have not previously been associated with a Mendelian disease. Here, we report fourteen individuals with heterozygous variants in FRYL who present with developmental delay, intellectual disability, dysmorphic features, and other congenital anomalies in multiple systems. The variants are confirmed de novo in all individuals except one. Human genetic data suggest that FRYL is intolerant to loss of function (LoF). We find that the fly FRYL ortholog, furry (fry), is expressed in multiple tissues, including the central nervous system where it is present in neurons but not in glia. Homozygous fry LoF mutation is lethal at various developmental stages, and loss of fry in mutant clones causes defects in wings and compound eyes. We next modeled four out of the five missense variants found in affected individuals using fry knockin alleles. One variant behaves as a severe LoF variant, whereas two others behave as partial LoF variants. One variant does not cause any observable defect in flies, and the corresponding human variant is not confirmed to be de novo, suggesting that this is a variant of uncertain significance. In summary, our findings support that fry is required for proper development in flies and that the LoF variants in FRYL cause a dominant disorder with developmental and neurological symptoms due to haploinsufficiency.

MFSD7c functions as a transporter of choline at the blood-brain barrier

Mutations in the orphan transporter MFSD7c (also known as Flvcr2), are linked to Fowler syndrome. Here, we used Mfsd7c knockout (Mfsd7c-/-) mice and cell-based assays to reveal that MFSD7c is a choline transporter at the blood-brain barrier (BBB). We performed comprehensive metabolomics analysis and detected differential changes of metabolites in the brains and livers of Mfsd7c-/-embryos. Particularly, we found that choline-related metabolites were altered in the brains but not in the livers of Mfsd7c-/- embryos. Thus, we hypothesized that MFSD7c regulates the level of choline in the brain. Indeed, expression of human MFSD7c in cells significantly increased choline uptake. Interestingly, we showed that choline uptake by MFSD7c is greatly increased by choline-metabolizing enzymes, leading us to demonstrate that MFSD7c is a facilitative transporter of choline. Furthermore, single-cell patch clamp analysis showed that the import of choline by MFSD7c is electrogenic. Choline transport function of MFSD7c was shown to be conserved in vertebrates, but not in yeasts. We demonstrated that human MFSD7c is a functional ortholog of HNM1, the yeast choline importer. We also showed that several missense mutations identified in patients exhibiting Fowler syndrome had abolished or reduced choline transport activity. Mice lacking Mfsd7c in endothelial cells of the central nervous system suppressed the import of exogenous choline from blood but unexpectedly had increased choline levels in the brain. Stable-isotope tracing study revealed that MFSD7c was required for exporting choline derived from lysophosphatidylcholine in the brain. Collectively, our work identifies MFSD7c as a choline exporter at the BBB and provides a foundation for future work to reveal the disease mechanisms of Fowler syndrome.

De novo variants in GATAD2A in individuals with a neurodevelopmental disorder: GATAD2A-related neurodevelopmental disorder

GATA zinc finger domain containing 2A (GATAD2A) is a subunit of the nucleosome remodeling and deacetylase (NuRD) complex. NuRD is known to regulate gene expression during neural development and other processes. The NuRD complex modulates chromatin status through histone deacetylation and ATP-dependent chromatin remodeling activities. Several neurodevelopmental disorders (NDDs) have been previously linked to variants in other components of NuRD's chromatin remodeling subcomplex (NuRDopathies). We identified five individuals with features of an NDD that possessed de novo autosomal dominant variants in GATAD2A. Core features in affected individuals include global developmental delay, structural brain defects, and craniofacial dysmorphology. These GATAD2A variants are predicted to affect protein dosage and/or interactions with other NuRD chromatin remodeling subunits. We provide evidence that a GATAD2A missense variant disrupts interactions of GATAD2A with CHD3, CHD4, and CHD5. Our findings expand the list of NuRDopathies and provide evidence that GATAD2A variants are the genetic basis of a previously uncharacterized developmental disorder.

Confirmation of Xp22.11 Duplication as a Germline Susceptibility Alteration in a Wilms Tumor Arising in Horseshoe Kidney

BackgroundThere is strong evidence of a genetic contribution to Wilms tumor, such as WT1 gene variation or epigenetic changes at chromosome locus 11p15. A previous genome wide association study (GWAS) of Wilms tumor identified other significant association loci including Xp22. Case report: A 4-year-old girl developed a Wilms tumor of the left isthmus of a horseshoe kidney. Chromosomal microarray analysis (CMA) of peripheral blood showed a 563 kb copy number gain at Xp22.11 that included PRDX4 and ZFX. PRDX4 has been shown to play an active role in the tumorigenesis of malignant neoplasms in various organs. Beckwith-Wiedemann methylation analysis and WT1 sequencing were negative. Whole exome sequencing of peripheral blood revealed pathogenic variant in PMS2 gene (c.765C > A), which is consistent with Lynch syndrome. Conclusion: We report a case of Wilms tumor with germline Xp22.11 duplication which further supports this locus as germline susceptibility alteration for Wilms Tumor.

Phenotypic expansion of CACNA1C-associated disorders to include isolated neurological manifestations

PURPOSE

CACNA1C encodes the alpha-1-subunit of a voltage-dependent L-type calcium channel expressed in human heart and brain. Heterozygous variants in CACNA1C have previously been reported in association with Timothy syndrome and long QT syndrome. Several case reports have suggested that CACNA1C variation may also be associated with a primarily neurological phenotype.

METHODS

We describe 25 individuals from 22 families with heterozygous variants in CACNA1C, who present with predominantly neurological manifestations.

RESULTS

Fourteen individuals have de novo, nontruncating variants and present variably with developmental delays, intellectual disability, autism, hypotonia, ataxia, and epilepsy. Functional studies of a subgroup of missense variants via patch clamp experiments demonstrated differential effects on channel function in vitro, including loss of function (p.Leu1408Val), neutral effect (p.Leu614Arg), and gain of function (p.Leu657Phe, p.Leu614Pro). The remaining 11 individuals from eight families have truncating variants in CACNA1C. The majority of these individuals have expressive language deficits, and half have autism.

CONCLUSION

We expand the phenotype associated with CACNA1C variants to include neurodevelopmental abnormalities and epilepsy, in the absence of classic features of Timothy syndrome or long QT syndrome.

Heterozygous HMGB1 loss-of-function variants are associated with developmental delay and microcephaly

13q12.3 microdeletion syndrome is a rare cause of syndromic intellectual disability. Identification and genetic characterization of patients with 13q12.3 microdeletion syndrome continues to expand the phenotypic spectrum associated with it. Previous studies identified four genes within the approximately 300 Kb minimal critical region including two candidate protein coding genes: KATNAL1 and HMGB1. To date, no patients carrying a sequence-level variant or a single gene deletion in HMGB1 or KATNAL1 have been described. Here we report six patients with loss-of-function variants involving HMGB1 and who had phenotypic features similar to the previously described 13q12.3 microdeletion syndrome cases. Common features included developmental delay, language delay, microcephaly, obesity and dysmorphic features. In silico analyses suggest that HMGB1 is likely to be intolerant to loss-of-function, and previous in vitro data are in line with the role of HMGB1 in neurodevelopment. These results strongly suggest that haploinsufficiency of the HMGB1 gene may play a critical role in the pathogenesis of the 13q12.3 microdeletion syndrome.

Placental pathology in an unsuspected case of mucolipidosis type II with secondary hyperparathyroidism in a premature infant

Mucolipidosis type II (MLII, MIM 252500) is a lysosomal storage disorders caused by defects in GNPTAB gene which encodes alpha and beta subunits of N-acetylglucosamine (GlcNAc)-1-phosphotransferase. Neonatal presentation includes coarse facial features, restricted postnatal growth, generalized hypotonia, gingival hypertrophy and multiple skeletal anomalies. Here we present a case of a 26-week gestational age preterm infant with MLII who did not exhibit the typical facial features at birth; however, the diagnosis was suggested from abnormal placental pathology showing trophoblastic lipidosis and initial skeletal abnormalities from chest radiograph revealing generalized diffuse severe bone demineralizing disease and multiple fractures. Biochemical testing revealed elevation of plasma lysosomal enzymes. Homozygous pathogenic variant, designated c.3505_3504del, was discovered from GNPTAB sequencing. Her course was complicated by respiratory distress, secondary hyperparathyroidism, abdominal distention and feeding difficulties. Urine mucopolysaccharides analysis revealed mild elevation of total and individual glycosaminoglycan species in a non-specific pattern. To our knowledge, our case is the most premature example of mucolipidosis type II that has ever been reported to date. This report highlights the importance of placental pathological studies in the diagnosis of lysosomal storage disorders.

Clinical epigenomics: genome-wide DNA methylation analysis for the diagnosis of Mendelian disorders

Purpose

We describe the clinical implementation of genome-wide DNA methylation analysis in rare disorders across the EpiSign diagnostic laboratory network and the assessment of results and clinical impact in the first subjects tested.

Methods

We outline the logistics and data flow between an integrated network of clinical diagnostics laboratories in Europe, the United States, and Canada. We describe the clinical validation of EpiSign using 211 specimens and assess the test performance and diagnostic yield in the first 207 subjects tested involving two patient subgroups: the targeted cohort (subjects with previous ambiguous/inconclusive genetic findings including genetic variants of unknown clinical significance) and the screening cohort (subjects with clinical findings consistent with hereditary neurodevelopmental syndromes and no previous conclusive genetic findings).

Results

Among the 207 subjects tested, 57 (27.6%) were positive for a diagnostic episignature including 48/136 (35.3%) in the targeted cohort and 8/71 (11.3%) in the screening cohort, with 4/207 (1.9%) remaining inconclusive after EpiSign analysis.

Conclusion

This study describes the implementation of diagnostic clinical genomic DNA methylation testing in patients with rare disorders. It provides strong evidence of clinical utility of EpiSign analysis, including the ability to provide conclusive findings in the majority of subjects tested.

Impaired eIF5A function causes a Mendelian disorder that is partially rescued in model systems by spermidine

The structure of proline prevents it from adopting an optimal position for rapid protein synthesis. Poly-proline-tract (PPT) associated ribosomal stalling is resolved by highly conserved eIF5A, the only protein to contain the amino acid hypusine. We show that de novo heterozygous EIF5A variants cause a disorder characterized by variable combinations of developmental delay, microcephaly, micrognathia and dysmorphism. Yeast growth assays, polysome profiling, total/hypusinated eIF5A levels and PPT-reporters studies reveal that the variants impair eIF5A function, reduce eIF5A-ribosome interactions and impair the synthesis of PPT-containing proteins. Supplementation with 1 mM spermidine partially corrects the yeast growth defects, improves the polysome profiles and restores expression of PPT reporters. In zebrafish, knockdown eif5a partly recapitulates the human phenotype that can be rescued with 1 µM spermidine supplementation. In summary, we uncover the role of eIF5A in human development and disease, demonstrate the mechanistic complexity of EIF5A-related disorder and raise possibilities for its treatment.

Rare cause of xanthinuria: a pediatric case of molybdenum cofactor deficiency B

Molybdenum cofactor is essential for the activity of multiple enzymes including xanthine dehydrogenase. Molybdenum cofactor deficiencies are rare inborn errors of metabolism. Clinically, they present with intractable seizures, axial hypotonia, and hyperekplexia. They further develop cerebral atrophy, microcephaly, global developmental delay and ectopia lentis. We report a 5-year-old female with clinically, biochemically and genetically confirmed molybdenum cofactor deficiency type B due to compound heterozygous pathogenic variants in the molybdenum cofactor synthesis 2 gene found on whole exome sequencing. The xanthine stones were a key clue towards diagnosis. No mutation was detected in XDH gene. Implementation of a low-purine diet, urine alkalization and hydration lead to a near complete decrease in stone burden. The patient received pyridoxine supplementation with improvement in energy levels and attentiveness. Despite reports of high mortality at a young age, our patient was 9 years old at the time of this writing. Molybdenum cofactor deficiencies should be considered in neonates with early-onset seizures, hypotonia, and feeding difficulties. Screening with serum uric acid levels and empiric treatment may be considered while awaiting genetic results.

MYO5B Pathogenic Variants Found to Cause Intestinal Symptoms Without Microvillus Inclusion Disease in a Child Who Previously Underwent Liver Transplantation for PFIC-like Cholestasis

Myosin 5B (MYO5B ) pathogenic variants are associated with microvillus inclusion disease (MVID), a congenital disorder of the enterocyte characterized by intractable diarrhea (5 ). A subset of MVID patients also have cholestatic liver disease. Conversely, some patients may have isolated cholestasis without gastrointestinal symptoms (2 ). Such patients have been described to have a progressive familial intrahepatic cholestasis (PFIC)-like phenotype with normal serum gamma-glutamyl transferase. We report a novel case in which MYO5B pathogenic variants were discovered by whole exome sequencing in a post-liver transplant patient who originally presented with PFIC-like cholestasis and chronic intermittent diarrhea without ultrastructural evidence of microvillus inclusion disease.

Discovery of a novel CHD7 CHARGE syndrome variant by integrated omics analyses

Chromodomain helicase DNA-binding protein 7 (CHD7) pathogenic variants are identified in more than 90% of infants and children with CHARGE (Coloboma of the iris, retina, and/or optic disk; congenital Heart defects, choanal Atresia, Retardation of growth and development, Genital hypoplasia, and characteristic outer and inner Ear anomalies and deafness) syndrome. Approximately, 10% of cases have no known genetic cause identified. We report a male child with clinical features of CHARGE syndrome and nondiagnostic genetic testing that included chromosomal microarray, CHD7 sequencing and deletion/duplication analysis, SEMA3E sequencing, and trio exome and whole-genome sequencing (WGS). We used a comprehensive clinical assessment, genome-wide methylation analysis (GMA), reanalysis of WGS data, and CHD7 RNA studies to discover a novel variant that causes CHD7 haploinsufficiency. The 7-year-old Hispanic male proband has typical phenotypic features of CHARGE syndrome. GMA revealed a CHD7-associated epigenetic signature. Reanalysis of the WGS data with focused bioinformatic analysis of CHD7 detected a novel, de novo 15 base pair deletion in Intron 4 of CHD7 (c.2239-20_2239-6delGTCTTGGGTTTTTGT [NM_017780.3]). Using proband RNA, we confirmed that this novel deletion causes CHD7 haploinsufficiency by disrupting the canonical 3' splice site and introducing a premature stop codon. Integrated genomic, epigenomic, and transcriptome analyses discovered a novel CHD7 variant that causes CHARGE syndrome.

Variable cardiovascular phenotypes associated with SMAD2 pathogenic variants

SMAD2 is a downstream effector in the TGF-β signaling pathway, which is important for pattern formation and tissue differentiation. Pathogenic variants in SMAD2 have been reported in association with arterial aneurysms and dissections and in large cohorts of subjects with complex congenital heart disease (CHD). We used whole exome sequencing (WES) to investigate the molecular cause of CHD and other congenital anomalies in three probands and of an arterial aneurysm in an additional patient. Patients 1 and 2 presented with complex CHD, developmental delay, seizures, dysmorphic features, short stature, and poor weight gain. Patient 3 was a fetus with complex CHD and heterotaxy. The fourth patient is an adult female with aortic root aneurysm and physical features suggestive of a connective tissue disorder. WES identified pathogenic truncating variants, a splice variant, and a predicted deleterious missense variant in SMAD2. We compare the phenotypes and genotypes in our patients with previously reported cases. Our data suggest two distinct phenotypes associated with pathogenic variants in SMAD2: complex CHD with or without laterality defects and other congenital anomalies, and a late-onset vascular phenotype characterized by arterial aneurysms with connective tissue abnormalities.

Early Onset and Severe Clinical Course Associated with the m.5540G>A Mutation in MT-TW

We report a patient harboring a de novo m.5540G>A mutation affecting the MT-TW gene coding for the mitochondrial tryptophan-transfer RNA. This patient presented with atonic-myoclonic epilepsy, bilateral sensorineural hearing loss, ataxia, motor regression, ptosis, and pigmentary retinopathy. Our proband had an earlier onset and more severe phenotype than the first reported patient harboring the same mutation. We discuss her clinical presentation and compare it with the only previously published case.