Spotlight on Hemorrhagic Destruction of the Brain, Subependymal Calcification, and Congenital Cataracts (HDBSCC).

Hemorrhagic Destruction of the Brain, Subependymal Calcification, and Congenital Cataracts (HDBSCC) is a rare syndrome caused by biallelic mutations in the JAM3 gene with significant intrafamilial variability in clinical presentation and brain imaging phenotypes. The clinical presentation of HDBSCC includes severe recurrent hemorrhages involving the brain parenchyma and the ventricles beginning in utero and continuing in infancy together with dense central cataracts present at birth. This comprehensive review documents reported cases on this unique condition and describes its genetic, neuroradiologic and ophthalmic features.

Exome Sequencing and the Identification of New Genes and Shared Mechanisms in Polymicrogyria.

Importance: Polymicrogyria is the most commonly diagnosed cortical malformation and is associated with neurodevelopmental sequelae including epilepsy, motor abnormalities, and cognitive deficits. Polymicrogyria frequently co-occurs with other brain malformations or as part of syndromic diseases. Past studies of polymicrogyria have defined heterogeneous genetic and nongenetic causes but have explained only a small fraction of cases.

Integrative systems biology characterizes immune-mediated neurodevelopmental changes in murine Zika virus microcephaly.

Characterizing perturbation of molecular pathways in congenital Zika virus (ZIKV) infection is critical for improved therapeutic approaches. Leveraging integrative systems biology, proteomics, and RNA-seq, we analyzed embryonic brain tissues from an immunocompetent, wild-type congenital ZIKV infection mouse model. ZIKV induced a robust immune response accompanied by the downregulation of critical neurodevelopmental gene programs.

Bi-allelic variants in INTS11 are associated with a complex neurological disorder.

The Integrator complex is a multi-subunit protein complex that regulates the processing of nascent RNAs transcribed by RNA polymerase II (RNAPII), including small nuclear RNAs, enhancer RNAs, telomeric RNAs, viral RNAs, and protein-coding mRNAs. Integrator subunit 11 (INTS11) is the catalytic subunit that cleaves nascent RNAs, but, to date, mutations in this subunit have not been linked to human disease. Here, we describe 15 individuals from 10 unrelated families with bi-allelic variants in INTS11 who present with global developmental and language delay, intellectual disability, impaired motor development, and brain atrophy.

Biallelic loss-of-function variants in WDR11 are associated with microcephaly and intellectual disability.

Heterozygous missense variants in the WD repeat domain 11 (WDR11) gene are associated with hypogonadotropic hypogonadism in humans. In contrast, knockout of both alleles of Wdr11 in mice results in a more severe phenotype with growth and developmental delay, features of holoprosencephaly, heart defects and reproductive disorders. Similar developmental defects known to be associated with aberrant hedgehog signaling and ciliogenesis have been found in zebrafish after Wdr11 knockdown.

Regulation of human cerebral cortical development by EXOC7 and EXOC8, components of the exocyst complex, and roles in neural progenitor cell proliferation and survival.

Purpose: The exocyst complex is a conserved protein complex that mediates fusion of intracellular vesicles to the plasma membrane and is implicated in processes including cell polarity, cell migration, ciliogenesis, cytokinesis, autophagy, and fusion of secretory vesicles. The essential role of these genes in human genetic disorders, however, is unknown.

Methods: We performed homozygosity mapping and exome sequencing of consanguineous families with recessively inherited brain development disorders.

Holoprosencephaly in Kabuki syndrome.

Kabuki syndrome is a rare, multi-systemic disorder of chromatin regulation due to mutations in either KMT2D or KDM6A that encode a H3K4 methyltransferase and an H3K27 demethylase, respectively. The associated clinical phenotype is a direct result of temporal and spatial changes in gene expression in various tissues including the brain. Although mild to moderate intellectual disability is frequently recognized in individuals with Kabuki syndrome, the identification of brain anomalies, mostly involving the hippocampus and related structures remains an exception.

Clinical and neurodevelopmental features in children with cerebral palsy and probable congenital Zika.

Objective: To describe the neurological and neurodevelopmental features at 1 year of age in children with cerebral palsy (CP) related to probable congenital Zika (CZ), followed in a referral neurorehabilitation hospital.

Methods: Data on 82 children with CP associated with probable CZ, who consecutively attended the neurodevelopmental and neurological assessment around one year of age, were collected. For neurodevelopmental evaluation, Bayley-III Scales of Infant and Toddler Development was used.

Congenital brain abnormalities during a Zika virus epidemic in Salvador, Brazil, April 2015 to July 2016.

BackgroundNorth-eastern Brazil was the region most affected by the outbreak of congenital Zika syndrome that followed the 2015 Zika virus (ZIKV) epidemics, with thousands of suspected microcephaly cases reported to the health authorities, mostly between late 2015 and early 2016. To describe clinical and epidemiological aspects of the outbreak of congenital brain abnormalities (CBAs) and to evaluate the accuracy of different head circumference screening criteria in predicting CBAs.MethodBetween April 2015 and July 2016, the Centers for Information and Epidemiologic Surveillance of Salvador, Brazil investigated the reported cases suspected of microcephaly and, based on intracranial imaging studies, confirmed or excluded a diagnosis of CBA.

PSMD12 haploinsufficiency in a neurodevelopmental disorder with autistic features.

Protein homeostasis is tightly regulated by the ubiquitin proteasome pathway. Disruption of this pathway gives rise to a host of neurological disorders. Through whole exome sequencing (WES) in families with neurodevelopmental disorders, we identified mutations in PSMD12, a core component of the proteasome, underlying a neurodevelopmental disorder with intellectual disability (ID) and features of autism spectrum disorder (ASD).

The ESCRT-III Protein CHMP1A Mediates Secretion of Sonic Hedgehog on a Distinctive Subtype of Extracellular Vesicles.

Endosomal sorting complex required for transport (ESCRT) complex proteins regulate biogenesis and release of extracellular vesicles (EVs), which enable cell-to-cell communication in the nervous system essential for development and adult function. We recently showed human loss-of-function (LOF) mutations in ESCRT-III member CHMP1A cause autosomal recessive microcephaly with pontocerebellar hypoplasia, but its mechanism was unclear. Here, we show Chmp1a is required for progenitor proliferation in mouse cortex and cerebellum and progenitor maintenance in human cerebral organoids.

Integrated genome and transcriptome sequencing identifies a noncoding mutation in the genome replication factor as the cause of microcephaly-micromelia syndrome.

While next-generation sequencing has accelerated the discovery of human disease genes, progress has been largely limited to the "low hanging fruit" of mutations with obvious exonic coding or canonical splice site impact. In contrast, the lack of high-throughput, unbiased approaches for functional assessment of most noncoding variants has bottlenecked gene discovery. We report the integration of transcriptome sequencing (RNA-seq), which surveys all mRNAs to reveal functional impacts of variants at the transcription level, into the gene discovery framework for a unique human disease, microcephaly-micromelia syndrome (MMS).

Deficient activity of alanyl-tRNA synthetase underlies an autosomal recessive syndrome of progressive microcephaly, hypomyelination, and epileptic encephalopathy.

Aminoacyl-transfer RNA (tRNA) synthetases ligate amino acids to specific tRNAs and are essential for protein synthesis. Although alanyl-tRNA synthetase (AARS) is a synthetase implicated in a wide range of neurological disorders from Charcot-Marie-Tooth disease to infantile epileptic encephalopathy, there have been limited data on their pathogenesis. Here, we report loss-of-function mutations in AARS in two siblings with progressive microcephaly with hypomyelination, intractable epilepsy, and spasticity.

Microcephaly Proteins Wdr62 and Aspm Define a Mother Centriole Complex Regulating Centriole Biogenesis, Apical Complex, and Cell Fate.

Mutations in several genes encoding centrosomal proteins dramatically decrease the size of the human brain. We show that Aspm (abnormal spindle-like, microcephaly-associated) and Wdr62 (WD repeat-containing protein 62) interact genetically to control brain size, with mice lacking Wdr62, Aspm, or both showing gene dose-related centriole duplication defects that parallel the severity of the microcephaly and increased ectopic basal progenitors, suggesting premature delamination from the ventricular zone. Wdr62 and Aspm localize to the proximal end of the mother centriole and interact physically, with Wdr62 required for Aspm localization, and both proteins, as well as microcephaly protein Cep63, required to localize CENPJ/CPAP/Sas-4, a final common target.

Mutations in mitochondrial enzyme GPT2 cause metabolic dysfunction and neurological disease with developmental and progressive features.

Mutations that cause neurological phenotypes are highly informative with regard to mechanisms governing human brain function and disease. We report autosomal recessive mutations in the enzyme glutamate pyruvate transaminase 2 (GPT2) in large kindreds initially ascertained for intellectual and developmental disability (IDD). GPT2 [also known as alanine transaminase 2 (ALT2)] is one of two related transaminases that catalyze the reversible addition of an amino group from glutamate to pyruvate, yielding alanine and α-ketoglutarate.

Novel loss-of-function variants in DIAPH1 associated with syndromic microcephaly, blindness, and early onset seizures.

Exome sequencing identified homozygous loss-of-function variants in DIAPH1 (c.2769delT; p.F923fs and c.

Mutations in PYCR2, Encoding Pyrroline-5-Carboxylate Reductase 2, Cause Microcephaly and Hypomyelination.

Despite recent advances in understanding the genetic bases of microcephaly, a large number of cases of microcephaly remain unexplained, suggesting that many microcephaly syndromes and associated genes have yet to be identified. Here, we report mutations in PYCR2, which encodes an enzyme in the proline biosynthesis pathway, as the cause of a unique syndrome characterized by postnatal microcephaly, hypomyelination, and reduced cerebral white-matter volume. Linkage mapping and whole-exome sequencing identified homozygous mutations (c.

Loss of PCLO function underlies pontocerebellar hypoplasia type III.

Objective: To identify the genetic cause of pontocerebellar hypoplasia type III (PCH3).

Methods: We studied the original reported pedigree of PCH3 and performed genetic analysis including genome-wide single nucleotide polymorphism genotyping, linkage analysis, whole-exome sequencing, and Sanger sequencing. Human fetal brain RNA sequencing data were then analyzed for the identified candidate gene.

Katanin p80 regulates human cortical development by limiting centriole and cilia number.

Katanin is a microtubule-severing complex whose catalytic activities are well characterized, but whose in vivo functions are incompletely understood. Human mutations in KATNB1, which encodes the noncatalytic regulatory p80 subunit of katanin, cause severe microlissencephaly. Loss of Katnb1 in mice confirms essential roles in neurogenesis and cell survival, while loss of zebrafish katnb1 reveals specific roles for katnin p80 in early and late developmental stages.

Neuropsychological function in a child with 18p deletion syndrome: a case report.

We report the neuropsychological profile of a 4-year-old boy with the rare 18p deletion syndrome. We used a battery of standardized tests to assess his development in intellect, language, visuomotor integration, academic readiness, socialization, and emotional and behavioral health. The results showed borderline intellectual function except for low average nonverbal reasoning skills.

Mutations in QARS, encoding glutaminyl-tRNA synthetase, cause progressive microcephaly, cerebral-cerebellar atrophy, and intractable seizures.

Progressive microcephaly is a heterogeneous condition with causes including mutations in genes encoding regulators of neuronal survival. Here, we report the identification of mutations in QARS (encoding glutaminyl-tRNA synthetase [QARS]) as the causative variants in two unrelated families affected by progressive microcephaly, severe seizures in infancy, atrophy of the cerebral cortex and cerebellar vermis, and mild atrophy of the cerebellar hemispheres. Whole-exome sequencing of individuals from each family independently identified compound-heterozygous mutations in QARS as the only candidate causative variants.

METTL23, a transcriptional partner of GABPA, is essential for human cognition.

Whereas many genes associated with intellectual disability (ID) encode synaptic proteins, transcriptional defects leading to ID are less well understood. We studied a large, consanguineous pedigree of Arab origin with seven members affected with ID and mild dysmorphic features. Homozygosity mapping and linkage analysis identified a candidate region on chromosome 17 with a maximum multipoint logarithm of odds score of 6.