De novo TRPM3 missense variant associated with neurodevelopmental delay and manifestations of cerebral palsy

We identified a de novo heterozygous transient receptor potential cation channel subfamily M (melastatin) member 3 (TRPM3) missense variant, p.(Asn1126Asp), in a patient with developmental delay and manifestations of cerebral palsy (CP) using phenotype-driven prioritization analysis of whole-genome sequencing data with Exomiser. The variant is localized in the functionally important ion transport domain of the TRPM3 protein and predicted to impact the protein structure. Our report adds TRPM3 to the list of Mendelian disease-associated genes that can be associated with CP and provides further evidence for the pathogenicity of the variant p.(Asn1126Asp).

ITPR1-associated spinocerebellar ataxia with craniofacial features-additional evidence for germline mosaicism

Inositol 1,4,5-triphosphate receptor type 1 (ITPR1) is an endoplasmic reticulum-bound intracellular inositol triphosphate receptor involved in the regulation of intracellular calcium. Pathogenic variants in ITPR1 are associated with spinocerebellar ataxia (SCA) types 15/16 and 29 and have recently been implicated in a facial microsomia syndrome. In this report, we present a family with three affected individuals found to have a heterozygous missense c.800C > T (predicted p.Thr267Met) who present clinically with a SCA29-like syndrome. All three individuals presented with varying degrees of ataxia, developmental delay, and apparent intellectual disability, as well as craniofacial involvement-an uncommon finding in patients with SCA29. The variant was identified using clinical exome sequencing and validated with Sanger sequencing. It is presumed to be inherited via parental germline mosaicism. We present our findings to provide additional evidence for germline mosaic inheritance of SCA29, as well as to expand the clinical phenotype of the syndrome.

SLC6A1 G443D associated with developmental delay and epilepsy

SLC6A1 is associated with an autosomal dominant early-onset seizure and epileptic encephalopathy associated with intellectual disability. We present a 2-yr-old girl with developmental delay and epilepsy, using a new computational filtering impact score to show the patient's variant ranks with other pathogenic variants. Genomic studies within the patient revealed a G443D variant of uncertain significance. Structural and evolutionary assessments establish this variant as a loss of function to the protein. Compiled metrics through our custom tools on sequence, structure, and protein dynamics combined with PolyPhen-2, PROVEAN, SIFT, and Align-GVGD reveal this variant to rank in the top functional outcome changes relative to gnomAD, TOPMed, and ClinVar variants known to date. The patient was resistant to multiple epileptic drugs, finally finding that valproic acid controls the seizures. This is consistent with additional groups studying SLC6A1 variants within patients.

VAC14 syndrome in two siblings with retinitis pigmentosa and neurodegeneration with brain iron accumulation

Whole-exome sequencing was used to identify the genetic etiology of a rapidly progressing neurological disease present in two of six siblings with early childhood onset of severe progressive spastic paraparesis and learning disabilities. A homozygous mutation (c.2005G>T, p, V669L) was found in VAC14, and the clinical phenotype is consistent with the recently described VAC14-related striatonigral degeneration, childhood-onset syndrome (SNDC) (MIM#617054). However, the phenotype includes a distinct clinical presentation of retinitis pigmentosa (RP), which has not previously been reported in association with VAC14 mutations. Brain magnetic resonance imaging (MRI) revealed abnormal magnetic susceptibility in the globus pallidus, which can be seen in neurodegeneration with brain iron accumulation (NBIA). RP is a group of inherited retinal diseases with phenotypic/genetic heterogeneity, and the pathophysiologic basis of RP is not completely understood but is thought to be due to a primary retinal photoreceptor cell degenerative process. Most cases of RP are seen in isolation (nonsyndromic); this is a report of RP in two siblings with VAC14-associated syndrome, and it is suggested that a connection between RP and VAC14-associated syndrome should be explored in future studies.

Homozygous noncanonical splice variant in LSM1 in two siblings with multiple congenital anomalies and global developmental delay

Two siblings, one male and one female, ages 6 and 13 yr old, have similar clinical features of global developmental delay, multiple congenital anomalies affecting the cardiac, genitourinary, and skeletal systems, and abnormal eye movements. Whole-genome sequencing revealed a homozygous splice variant (NM_014462.3:c.231+4A>C) in LSM1 that segregated with the phenotype in the family. LSM1 has a role in pre-mRNA splicing and degradation. Expression studies revealed absence of expression of the canonical isoform in the affected individuals. The Lsm1 knockout mice have a partially overlapping phenotype that affects the brain, heart, and eye. To our knowledge, LSM1 has not been associated with any human disorder; however, the tissue expression pattern, gene constraint, and the similarity of the phenotype in our patients and the knockout mice models suggest it has a role in the development of multiple organ systems in humans.

Early-onset infant epileptic encephalopathy associated with a de novo PPP3CA gene mutation

Epileptic encephalopathies are severe seizure disorders accompanied by intellectual disability. Whole-exome sequencing technology has enabled the discovery of genetic mutations responsible for a wide range of diseases, and severe epilepsy and neurodevelopmental diseases are often associated with rare de novo mutations. We identified a novel de novo frameshift mutation in the PPP3CA gene encoding calcium-dependent protein phosphatase (calcineurin) catalytic subunit A (c.1255_1256del, p.Ser419Cysfs*31) in an 11.5-mo-old female with early-onset refractory epilepsy and developmental delay. This finding expands the list of PPP3CA mutations associated with early-onset severe neurodevelopmental disease with seizures and provides further details on clinical features.

9p24 triplication in syndromic hydrocephalus with diffuse villous hyperplasia of the choroid plexus

Hydrocephalus, a disorder of impaired cerebrospinal fluid (CSF) homeostasis, often results from an imbalance between CSF production and reabsorption. Rarely, hydrocephalus is the consequence of CSF hypersecretion in the context of diffuse villous hyperplasia of the choroid plexus (DVHCP). The limited genetic information in previously reported cases suggests a high prevalence of gains of Chromosome 9p in this disease, although the critical genes involved in DVHCP pathogenesis have not been identified. Here, we report a patient with syndromic hydrocephalus with DVHCP associated with a novel 9p24.3-11.2 triplication and 15q13.2-q13.3 microdeletion. We review the clinical, radiological, and pathological features of DVHCP, as well as its surgical management. A better understanding of the genetic basis of DVHCP could spur the development of rational, targeted nonsurgical hydrocephalus treatments.

Co-occurrence of a maternally inherited DNMT3A duplication and a paternally inherited pathogenic variant in EZH2 in a child with growth retardation and severe short stature: atypical Weaver syndrome or evidence of a DNMT3A dosage effect?

Overgrowth syndromes are a clinically heterogeneous group of disorders characterized by localized or generalized tissue overgrowth and varying degrees of developmental and intellectual disability. An expanding list of genes associated with overgrowth syndromes include the histone methyltransferase genes EZH2 and NSD1, which cause Weaver and Sotos syndrome, respectively, and the DNA methyltransferase (DNMT3A) gene that results in Tatton-Brown–Rahman syndrome (TBRS). Here, we describe a 5-year-old female with a paternally inherited pathogenic mutation in EZH2 (c.2050C>T, p.Arg684Cys) and a maternally inherited 505-kb duplication of uncertain significance at 2p23.3 (encompassing five genes, including DNMT3A) who presented with intrauterine growth restriction, slow postnatal growth, short stature, hypotonia, developmental delay, and neuroblastoma diagnosed at the age of 8 mo. Her father had tall stature, dysmorphic facial features, and intellectual disability consistent with Weaver syndrome, whereas her mother had short stature, cognitive delays, and chronic nonprogressive leukocytosis. It has been previously shown that EZH2 directly controls DNA methylation through physical association with DNMTs, including DNMT3A, with concomitant H3K27 methylation and CpG promoter methylation leading to repression of EZH2 target genes. Interestingly, NSD1 is involved in H3K36 methylation, a mark associated with transcriptional activation, and exhibits exquisite dosage sensitivity leading to overgrowth when deleted and severe undergrowth when duplicated in vivo. Although there is currently no evidence of dosage effects for DNMT3A, the co-occurrence of a duplication involving this gene and a pathogenic alteration in EZH2 in a patient with severe undergrowth is suggestive of a similar paradigm and further study is warranted.

The case for early use of rapid whole-genome sequencing in management of critically ill infants: late diagnosis of Coffin-Siris syndrome in an infant with left congenital diaphragmatic hernia, congenital heart disease, and recurrent infections

Congenital diaphragmatic hernia (CDH) results from incomplete formation of the diaphragm leading to herniation of abdominal organs into the thoracic cavity. CDH is associated with pulmonary hypoplasia, congenital heart disease, and pulmonary hypertension. Genetically, it is associated with aneuploidies, chromosomal copy-number variants, and single gene mutations. CDH is the most expensive noncardiac congenital defect. Management frequently requires implementation of extracorporeal membrane oxygenation (ECMO), which increases management expenditures 2.4–3.5-fold. The cost of management of CDH has been estimated to exceed $250 million per year. Despite in-hospital survival of 80%–90%, current management is imperfect, as a great proportion of surviving children have long-term functional deficits. We report the case of a premature infant prenatally diagnosed with CDH and congenital heart disease, who had a protracted and complicated course in the intensive care unit with multiple surgical interventions, including postcardiac surgery ECMO, gastrostomy tube placement with Nissen fundoplication, tracheostomy for respiratory failure, recurrent infections, and developmental delay. Rapid whole-genome sequencing (rWGS) identified a de novo, likely pathogenic, c.3096_ 3100delCAAAG (p.Lys1033Argfs*32) variant in ARID1B, providing a diagnosis of Coffin–Siris syndrome. Her parents elected palliative care and she died later that day.

De novo variants in EBF3 are associated with hypotonia, developmental delay, intellectual disability, and autism

Using whole-exome sequencing, we identified seven unrelated individuals with global developmental delay, hypotonia, dysmorphic facial features, and an increased frequency of short stature, ataxia, and autism with de novo heterozygous frameshift, nonsense, splice, and missense variants in the Early B-cell Transcription Factor Family Member 3 (EBF3) gene. EBF3 is a member of the collier/olfactory-1/early B-cell factor (COE) family of proteins, which are required for central nervous system (CNS) development. COE proteins are highly evolutionarily conserved and regulate neuronal specification, migration, axon guidance, and dendritogenesis during development and are essential for maintaining neuronal identity in adult neurons. Haploinsufficiency of EBF3 may affect brain development and function, resulting in developmental delay, intellectual disability, and behavioral differences observed in individuals with a deleterious variant in EBF3.

Novel de novo variant in EBF3 is likely to impact DNA binding in a patient with a neurodevelopmental disorder and expanded phenotypes: patient report, in silico functional assessment, and review of published cases

Pathogenic variants in EBF3 were recently described in three back-to-back publications in association with a novel neurodevelopmental disorder characterized by intellectual disability, speech delay, ataxia, and facial dysmorphisms. In this report, we describe an additional patient carrying a de novo missense variant in EBF3 (c.487C>T, p.(Arg163Trp)) that falls within a conserved residue in the zinc knuckle motif of the DNA binding domain. Without a solved structure of the DNA binding domain, we generated a homology-based atomic model and performed molecular dynamics simulations for EBF3, which predicted decreased DNA affinity for p.(Arg163Trp) compared with wild-type protein and control variants. These data are in agreement with previous experimental studies of EBF1 showing the paralogous residue is essential for DNA binding. The conservation and experimental evidence existing for EBF1 and in silico modeling and dynamics simulations to validate comparable behavior of multiple variants in EBF3 demonstrates strong support for the pathogenicity of p.(Arg163Trp). We show that our patient presents with phenotypes consistent with previously reported patients harboring EBF3 variants and expands the phenotypic spectrum of this newly identified disorder with the additional feature of a bicornuate uterus.

Somatic overgrowth associated with homozygous mutations in both MAN1B1 and SEC23A

Using whole-exome sequencing, we identified homozygous mutations in two unlinked genes, SEC23A c.1200G>C (p.M400I) and MAN1B1 c.1000C>T (p.R334C), associated with congenital birth defects in two patients from a consanguineous family. Patients presented with carbohydrate-deficient transferrin, tall stature, obesity, macrocephaly, and maloccluded teeth. The parents were healthy heterozygous carriers for both mutations and an unaffected sibling with tall stature carried the heterozygous mutation in SEC23A only. Mutations in SEC23A are responsible for craniolenticosultura dysplasia (CLSD). CLSD patients are short, have late-closing fontanels, and have reduced procollagen (pro-COL1A1) secretion because of abnormal pro-COL1A1 retention in the endoplasmic reticulum (ER). The mutation we identified in MAN1B1 was previously associated with reduced MAN1B1 protein and congenital disorders of glycosylation (CDG). CDG patients are also short, are obese, and have abnormal glycan remodeling. Molecular analysis of fibroblasts from the family revealed normal levels of SEC23A in all cells and reduced levels of MAN1B1 in cells with heterozygous or homozygous mutations in SEC23A and MAN1B1. Secretion of pro-COL1A1 was increased in fibroblasts from the siblings and patients, and pro-COL1A1 was retained in Golgi of heterozygous and homozygous mutant cells, although intracellular pro-COL1A1 was increased in patient fibroblasts only. We postulate that increased pro-COL1A1 secretion is responsible for tall stature in these patients and an unaffected sibling, and not previously discovered in patients with mutations in either SEC23A or MAN1B1. The patients in this study share biochemical and cellular characteristics consistent with mutations in MAN1B1 and SEC23A, indicating a digenic disease.