Expansion and further delineation of the SETD5 phenotype leading to global developmental delay, variable dysmorphic features, and reduced penetrance

Diagnostic exome sequencing (DES) has aided delineation of the phenotypic spectrum of rare genetic etiologies of intellectual disability (ID). A SET domain containing 5 gene (SETD5) phenotype of ID and dysmorphic features has been previously described in relation to patients with 3p25.3 deletions and in a few individuals with de novo sequence alterations. Herein, we present additional patients with pathogenic SETD5 sequence alterations. The majority of patients in this cohort and previously reported have developmental delay, behavioral/psychiatric issues, and variable hand and skeletal abnormalities. We also present an apparently unaffected carrier mother of an affected individual and a carrier mother with normal intelligence and affected twin sons. We suggest that the phenotype of SETD5 is more complex and variable than previously presented. Therefore, many features and presentations need to be considered when evaluating a patient for SETD5 alterations through DES

Heterozygous Variants in KDM4B Lead to Global Developmental Delay and Neuroanatomical Defects

KDM4B is a lysine-specific demethylase with a preferential activity on H3K9 tri/di-methylation (H3K9me3/2)-modified histones. H3K9 tri/di-demethylation is an important epigenetic mechanism responsible for silencing of gene expression in animal development and cancer. However, the role of KDM4B on human development is still poorly characterized. Through international data sharing, we gathered a cohort of nine individuals with mono-allelic de novo or inherited variants in KDM4B. All individuals presented with dysmorphic features and global developmental delay (GDD) with language and motor skills most affected. Three individuals had a history of seizures, and four had anomalies on brain imaging ranging from agenesis of the corpus callosum with hydrocephalus to cystic formations, abnormal hippocampi, and polymicrogyria. In mice, lysine demethylase 4B is expressed during brain development with high levels in the hippocampus, a region important for learning and memory. To understand how KDM4B variants can lead to GDD in humans, we assessed the effect of KDM4B disruption on brain anatomy and behavior through an in vivo heterozygous mouse model (Kdm4b+/-), focusing on neuroanatomical changes. In mutant mice, the total brain volume was significantly reduced with decreased size of the hippocampal dentate gyrus, partial agenesis of the corpus callosum, and ventriculomegaly. This report demonstrates that variants in KDM4B are associated with GDD/ intellectual disability and neuroanatomical defects. Our findings suggest that KDM4B variation leads to a chromatinopathy, broadening the spectrum of this group of Mendelian disorders caused by alterations in epigenetic machinery

BCL11B-related disorder in two canadian children: Expanding the clinical phenotype.

The product of the BCL11B (B-Cell Leukemia 11) gene is a bi-functional transcriptional regulator that can act as either a repressor or an activator. It plays an important role in the development of the nervous, immune, and cutaneous systems, and is also involved in dental and craniofacial development. BCL11B-Related Disorder (BCL11BRD) is a novel rare neurodevelopmental disorder associated with mutations in BCL11B. A total of 17 patients have been described in the literature thus far. The main symptoms of BCL11BRD include global developmental delay, speech impairment, dental anomalies, feeding difficulties, refractive errors, dysmorphic features, and immunological abnormalities. In this report, we describe two Canadian girls, with pathogenic de novo BCL11B variants, both diagnosed via exome sequencing. One of the patients had global developmental delay, dental anomalies, dysmorphic features, dyskinesia and hypotonia; the latter two symptoms have not been previously reported in patients with BCL11BRD. She also had dysgenesis of corpus callosum and dilatation of the frontal horns of lateral ventricles, a brain anomaly that has been previously reported in only one other patient. The second patient had developmental delay, dysmorphic features, spasticity in lower limbs and dental anomalies. Our report contributes to the knowledge of the BCL11BRD, expands the clinical phenotype, and can also aid with genetic counseling of newly identified patients

Heterozygous de novo variants in <em>CSNK1G1</em> are associated with syndromic developmental delay and autism spectrum disorder.

The gamma-1 isoform of casein kinase 1, the protein encoded byCSNK1G1, is involved in the growth and morphogenesis of cells. This protein is expressed ubiquitously among many tissue types, including the brain, where it regulates the phosphorylation of N-methyl-D-aspartate receptors and plays a role in synaptic transmission. One prior individual with a de novo variant inCSNK1Gpresenting with severe developmental delay and early-onset epilepsy has been reported. Here we report an updated clinical history of this previously published case, as well as four additional individuals with de novo variants inCSNK1G1identified via microarray-based comparative genomic hybridization, exome, or genome sequencing. All individuals (n = 5) had developmental delay. At least three individuals had diagnoses of autism spectrum disorder. All participants were noted to have dysmorphic facial features, although the reported findings varied widely and therefore may not clearly be recognizable. None of the participants had additional major malformations. Taken together, our data suggest thatCSNK1G1may be a cause of syndromic developmental delay and possibly autism spectrum disorder

The prevalence and phenotypic range associated with biallelic PKDCC variants

PKDCC encodes a component of Hedgehog signalling required for normal chondrogenesis and skeletal development. Although biallelic PKDCC variants have been implicated in rhizomelic shortening of limbs with variable dysmorphic features, this association was based on just two patients. In this study, data from the 100 000 Genomes Project was used in conjunction with exome sequencing and panel-testing results accessed via international collaboration to assemble a cohort of eight individuals from seven independent families with biallelic PKDCC variants. The allelic series included six frameshifts, a previously described splice-donor site variant and a likely pathogenic missense variant observed in two families that was supported by in silico structural modelling. Database queries suggested that the prevalence of this condition is between 1 of 127 and 1 of 721 in clinical cohorts with skeletal dysplasia of unknown aetiology. Clinical assessments, combined with data from previously published cases, indicate a predominantly upper limb involvement. Micrognathia, hypertelorism and hearing loss appear to be commonly co-occurring features. In conclusion, this study strengthens the link between biallelic inactivation of PKDCC and rhizomelic limb-shortening and will enable clinical testing laboratories to better interpret variants in this gene

Pathogenic variants in SMARCA5, a chromatin remodeler, cause a range of syndromic neurodevelopmental features

Intellectual disability encompasses a wide spectrum of neurodevelopmental disorders, with many linked genetic loci. However, the underlying molecular mechanism for more than 50% of the patients remains elusive. We describe pathogenic variants in SMARCA5, encoding the ATPase motor of the ISWI chromatin remodeler, as a cause of a previously unidentified neurodevelopmental disorder, identifying 12 individuals with de novo or dominantly segregating rare heterozygous variants. Accompanying phenotypes include mild developmental delay, frequent postnatal short stature and microcephaly, and recurrent dysmorphic features. Loss of function of the SMARCA5 Drosophila ortholog Iswi led to smaller body size, reduced sensory dendrite complexity, and tiling defects in larvae. In adult flies, Iswi neural knockdown caused decreased brain size, aberrant mushroom body morphology, and abnormal locomotor function. Iswi loss of function was rescued by wild-type but not mutant SMARCA5. Our results demonstrate that SMARCA5 pathogenic variants cause a neurodevelopmental syndrome with mild facial dysmorphia. Copyright © 2021 The Authors, some rights reserved;Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Missense variants in TAF1 and developmental phenotypes: Challenges of determining pathogenicity

We recently described a new neurodevelopmental syndrome (TAF1/MRXS33 intellectual disability [ID] syndrome) (MIM# 300966) caused by pathogenic variants involving the X‐linked gene TATA‐box binding protein associated factor 1 (TAF1), which participates in RNA polymerase II transcription. The initial study reported 11 families, and the syndrome was defined as presenting early in life with hypotonia, facial dysmorphia, and developmental delay that evolved into ID and/or autism spectrum disorder. We have now identified an additional 27 families through a genotype‐first approach. Familial segregation analysis, clinical phenotyping, and bioinformatics were capitalized on to assess potential variant pathogenicity, and molecular modeling was performed for those variants falling within structurally characterized domains of TAF1. A novel phenotypic clustering approach was also applied, in which the phenotypes of affected individuals were classified using 51 standardized Human Phenotype Ontology terms. Phenotypes associated with TAF1 variants show considerable pleiotropy and clinical variability, but prominent among previously unreported effects were brain morphological abnormalities, seizures, hearing loss, and heart malformations. Our allelic series broadens the phenotypic spectrum of the TAF1/MRXS33 ID syndrome and the range of TAF1 molecular defects in humans. It also illustrates the challenges for determining the pathogenicity of inherited missense variants, particularly for a gene mapping to chromosome X

Bi-allelic variants in <em>SPATA5L1</em> lead to intellectual disability, spastic-dystonic cerebral palsy, epilepsy, and hearing loss.

Spermatogenesis-associated 5 like 1 (SPATA5L1) represents an orphan gene encoding a protein of unknown function. We report 28 bi-allelic variants in SPATA5L1 associated with sensorineural hearing loss in 47 individuals from 28 (26 unrelated) families. In addition, 25/47 affected individuals (53%) presented with microcephaly, developmental delay/intellectual disability, cerebral palsy, and/or epilepsy. Modeling indicated damaging effect of variants on the protein, largely via destabilizing effects on protein domains. Brain imaging revealed diminished cerebral volume, thin corpus callosum, and periventricular leukomalacia, and quantitative volumetry demonstrated significantly diminished white matter volumes in several individuals. Immunofluorescent imaging in rat hippocampal neurons revealed localization of Spata5l1 in neuronal and glial cell nuclei and more prominent expression in neurons. In the rodent inner ear, Spata5l1 is expressed in the neurosensory hair cells and inner ear supporting cells. Transcriptomic analysis performed with fibroblasts from affected individuals was able to distinguish affected from controls by principal components. Analysis of differentially expressed genes and networks suggested a role for SPATA5L1 in cell surface adhesion receptor function, intracellular focal adhesions, and DNA replication and mitosis. Collectively, our results indicate that bi-allelic SPATA5L1 variants lead to a human disease characterized by sensorineural hearing loss (SNHL) with or without a nonprogressive mixed neurodevelopmental phenotype