Severe Microcephaly Research Articles

Characterization of Two Novel PNKP Splice-Site Variants in a Proband With Microcephaly, Intellectual Disability, and Multiple Malformations.

Polynucleotide kinase phosphatase (PNKP), encoded by the PNKP gene, is a DNA processing enzyme involved in double-strand break and single-strand break repair pathways, which are essential for genome stability and for the correct development and maintenance of human nervous system. PNKP biallelic loss-of-function variants have been associated with a broad spectrum of neurological anomalies, ranging from congenital microcephaly with intellectual disability and seizures (MCSZ), to later onset forms of ataxia-oculomotor apraxia (AOA4) or peripheral neuropathy (CMT2B2). We report the atypical clinical manifestations of a patient with severe microcephaly, short stature, developmental delay, conductive hearing loss, and tracheoesophageal malformation, in the absence of seizures. Whole exome sequencing analysis identified two novel, compound heterozygous splice-site variants in the PNKP gene (NM_007254.4): c.1448+1G > A and c.199-8_199-5del. To demonstrate the effect of both variants on the splicing process and prove their pathogenicity, we performed a hybrid minigene assay, which successfully highlighted a deleterious impact on the transcript, particularly regarding the c.199-8_199-5del variant. The uncommon clinical features of the proband and the identification of two newly associated pathogenic variants add further evidence to the allelic and phenotypic heterogeneity of the PNKP locus.

Expression of Autophagy-Related Proteins in Microlissencephaly Associated with a Novel Variant in the WDR81 Gene

Introduction: Microlissencephaly is a subtype of congenital microcephaly characterized by extreme microcephaly with simplified gyral pattern. Other brain malformations may accompany it. WDR81 encodes a multi-domain transmembrane protein that is predominantly expressed in the brain and is thought to play a role in endolysosomal trafficking and autophagy. Methods: We reported two siblings with microlissencephaly born to consanguineous Turkish parents and reviewed all previously reported patients with WDR81 variants presenting with severe microcephaly accompanied by congenital brain malformations. Whole-exome sequencing was performed on both siblings. Sanger DNA sequencing was performed on the patients’ parents. We also examined LC3, p62, and Beclin 1 mRNA and protein expression levels from blood samples of both siblings using real-time PCR and Western blotting, respectively. Results: Whole-exome sequencing revealed a novel biallelic c.4157+5G>A splice variant in the WDR81 gene in both siblings. In our study, LC3, p62, and Beclin 1 mRNA expression levels were high, LC3 protein expression level was also high and p62 and Beclin 1 protein expression levels were low. Conclusion: High LC3 and low p62 protein expression levels supported studies concluding that WDR81 inhibits autophagy through PI3KC3 inhibition, while low Beclin 1 protein expression level supported studies concluding that autophagy is suppressed in case of loss of function variants in the WDR81 gene. We suggest that due to its role in endolysosomal trafficking, WDR81-related diseases should be included in vesicular trafficking disorders.

Loss-of-function in RBBP5 results in a syndromic neurodevelopmental disorder associated with microcephaly

PurposeEpigenetic dysregulation has been associated with many inherited disorders. RBBP5 (HGNC:9888) encodes a core member of the protein complex that methylates histone 3 lysine-4 and has not been implicated in human disease. MethodsWe identify 5 unrelated individuals with de novo heterozygous variants in RBBP5. Three nonsense/frameshift and 2 missense variants were identified in probands with neurodevelopmental symptoms, including global developmental delay, intellectual disability, microcephaly, and short stature. Here, we investigate the pathogenicity of the variants through protein structural analysis and transgenic Drosophila models. ResultsBoth missense p.(T232I) and p.(E296D) variants affect evolutionarily conserved amino acids located at the interface between RBBP5 and the nucleosome. In Drosophila, overexpression analysis identifies partial loss-of-function mechanisms when the variants are expressed using the fly Rbbp5 or human RBBP5 cDNA. Loss of Rbbp5 leads to a reduction in brain size. The human reference or variant transgenes fail to rescue this loss and expression of either missense variant in an Rbbp5 null background results in a less severe microcephaly phenotype than the human reference, indicating both missense variants are partial loss-of-function alleles. ConclusionHaploinsufficiency of RBBP5 observed through de novo null and hypomorphic loss-of-function variants is associated with a syndromic neurodevelopmental disorder.

Distinct neurodevelopmental and epileptic phenotypes associated with gain- and loss-of-function GABRB2 variants

Variants in GABRB2, encoding the β2 subunit of the γ-aminobutyric acid type A (GABAA) receptor, can result in a diverse range of conditions, ranging from febrile seizures to severe developmental and epileptic encephalopathies. However, the mechanisms underlying the risk of developing milder vs more severe forms of disorder remain unclear. In this study, we conducted a comprehensive genotype-phenotype correlation analysis in a cohort of individuals with GABRB2 variants. Genetic and electroclinical data of 42 individuals harbouring 26 different GABRB2 variants were collected and accompanied by electrophysiological analysis of the effects of the variants on receptor function. Electrophysiological assessments of α1β2γ2 receptors revealed that 25/26 variants caused dysfunction to core receptor properties such as GABA sensitivity. Of these, 17 resulted in gain-of-function (GOF) while eight yielded loss-of-function traits (LOF). Genotype-phenotype correlation analysis revealed that individuals harbouring GOF variants suffered from severe developmental delay/intellectual disability (DD/ID, 74%), movement disorders such as dystonia or dyskinesia (59%), microcephaly (50%) and high risk of early mortality (26%). Conversely, LOF variants were associated with milder disease manifestations. Individuals with these variants typically exhibited fever-triggered seizures (92%), milder degrees of DD/ID (85%), and maintained ambulatory function (85%). Notably, severe movement disorders or microcephaly were not reported in individuals with loss-of-function variants. The data reveals that genetic variants in GABRB2 can lead to both gain and loss-of-function, and this divergence is correlated with distinct disease manifestations. Utilising this information, we constructed a diagnostic flowchart that aids in predicting the pathogenicity of recently identified variants by considering clinical phenotypes. This work was funded by the Australian National Health & Medical Research Council, the Novo Nordisk Foundation and The Lundbeck Foundation.

STAMBP is Required for Long-Term Maintenance of Neural Progenitor Cells Derived from hESCs.

Mutations in STAMBP have been well-established to cause congenital human microcephaly-capillary malformation (MIC-CAP) syndrome, a rare genetic disorder characterized by global developmental delay, severe microcephaly, capillary malformations, etc. Previous biochemical investigations and loss-of-function studies in mice have provided insights into the mechanism of STAMBP, however, it remains controversial how STAMBP deficiency leads to malformation of those affected tissues in patients. In this study, we investigated the function and underlying mechanism of STAMBP during neural differentiation of human embryonic stem cells (hESCs). We found that STAMBP is dispensable for the pluripotency maintenance or neural differentiation of hESCs. However, neural progenitor cells (NPCs) derived from STAMBP-deficient hESCs fail to be long-term maintained/expanded in vitro. We identified the anti-apoptotic protein CFLAR is down-regulated in those affected NPCs and ectopic expression of CFLAR rescues NPC defects induced by STAMBP-deficiency. Our study not only provides novel insight into the mechanism of neural defects in STAMBP mutant patients, it also indicates that the death receptor mediated apoptosis is an obstacle for long-term maintenance/expansion of NPCs in vitro thus counteracting this cell death pathway could be beneficial to the generation of NPCs in vitro.

IGF1 Haploinsufficiency: Phenotype and Response to Growth Hormone Treatment in 9 Patients.

The clinical features of bi-allelic IGF1 defects are well established, i.e., severe growth failure and microcephaly, delayed psychomotor development, and sensorineural deafness. However, information on clinical and endocrine consequences of heterozygous IGF1 variants and treatment options is scarce. We aimed at extending the knowledge base of the clinical presentation and growth response to recombinant human growth hormone (rhGH) of patients carrying such variants. Retrospective case series of patients with pathogenic heterozygous IGF1 variants. Nine patients from six families were included, harbouring five whole or partial gene deletions and one frameshift variant resulting in a premature stop codon (three de novo, one unknown inheritance). In the other two families, variants segregated with short stature. Mean (SD) birth length was -1.9 (1.3) SDS (n = 7), height -3.8 (0.6) SDS, head circumference -2.5 (0.6) SDS, serum IGF-I -1.9 (0.7) SDS, serum IGFBP-3 1.1 (0.4) SDS (n = 7), and GH peak range 5-31 μg/L (n = 4). Five patients showed feeding problems in infancy. Average height increased after 1 and 2 years of rhGH treatment by 0.8 SDS (range 0.3-1.3 SDS) and 1.3 SDS (range 0.5-2.0 SDS), respectively. Adult height in 2 patients was -2.8 and -1.3 SDS, which was, respectively, 1.3 and 2.9 SDS taller than predicted before start of treatment. Haploinsufficiency of IGF1 causes a variable phenotype of prenatal and postnatal growth failure, microcephaly, feeding difficulties, low/low-normal serum IGF-I values in contrast to serum IGFBP-3 in the upper-normal range. Treatment with rhGH increased growth in the first 2 years of treatment, and in 2 patients adult height after treatment was higher than predicted at treatment initiation.

Re-analysis of whole genome sequencing ends a diagnostic odyssey: Case report of an RNU4-2 related neurodevelopmental disorder.

Despite increasing knowledge of disease-causing genes in human genetics, approximately half of the individuals affected by neurodevelopmental disorders remain genetically undiagnosed. Part of this missing heritability might be caused by genetic variants outside of protein-coding genes, which are not routinely diagnostically investigated. A recent preprint identified de novo variants in the non-coding spliceosomal snRNA gene RNU4-2 as a cause of a frequent novel syndromic neurodevelopmental disorder. Here we mined 164 whole genome sequencing (WGS) trios from individuals with neurodevelopmental or multiple congenital anomaly disorders that received diagnostic genomic investigations at our clinic. We identify a recurrent de novo RNU4-2 variant (NR_003137.2(RNU4-2):n.64_65insT) in a 5-year-old girl with severe global developmental delay, hypotonia, microcephaly, and seizures that likely explains her phenotype, given that extensive previous genetic investigations failed to identify an alternative cause. We present detailed phenotyping of the individual obtained during a 5-year follow-up. This includes photographs showing recognizable facial features for this novel disorder, which might allow prioritizing other currently unexplained affected individuals sharing similar facial features for targeted investigations of RNU4-2. This case illustrates the power of re-analysis to solve previously unexplained cases even when a diagnostic genome remains negative.

Genetic Findings in Short Turkish Children Born to Consanguineous Parents.

The diagnostic yield of genetic analysis in the evaluation of children with short stature depends on associated clinical characteristics, but the additional effect of parental consanguinity has not been well documented. This observational case series of 42 short children from 34 consanguineous families was collected by six referral centres of paediatric endocrinology (inclusion criteria: short stature and parental consanguinity). In 18 patients (12 families, group 1), the clinical features suggested a specific genetic defect in the growth hormone (GH) insulin-like growth factor I (IGF-I) axis, and a candidate gene approach was used. In others (group 2), a hypothesis-free approach was chosen (gene panels, microarray analysis, and whole exome sequencing) and further subdivided into 11 patients with severe short stature (height <-3.5 standard deviation score [SDS]) and microcephaly (head circumference <-3.0 SDS) (group 2a), 10 patients with syndromic short stature (group 2b), and 3 patients with nonspecific isolated GH deficiency (group 2c). In all 12 families from group 1, (likely) pathogenic variants were identified in GHR, IGFALS, GH1, and STAT5B. In 9/12 families from group 2a, variants were detected in PCNT, SMARCAL1, SRCAP, WDR4, and GHSR. In 5/9 families from group 2b, variants were found in TTC37, SCUBE3, NSD2, RABGAP1, and 17p13.3 microdeletions. In group 2c, no genetic cause was found. Homozygous, compound heterozygous, and heterozygous variants were found in 21, 1, and 4 patients, respectively. Genetic testing in short children from consanguineous parents has a high diagnostic yield, especially in cases of severe GH deficiency or insensitivity, microcephaly, and syndromic short stature.

Two Growth-Restricted Fetuses with Severe Microcephaly and Neurologic Abnormalities.

Two Growth-Restricted Fetuses with Severe Microcephaly and Neurologic Abnormalities.

Continuous epileptiform discharges are associated with worse neurodevelopmental findings in a congenital Zika syndrome prospective cohort

PurposeThis study aimed to identify continuous epileptiform discharges (CEDs) on electroencephalograms (EEG) and to determine their clinical significance in children with congenital Zika syndrome (CZS). MethodsThis prospective cohort study included 75 children diagnosed with CZS born from March 2015 and followed up until September 2018 (age up to 36 months). EEG was performed to detect CEDs up to 24 months old. Data on obstetric, demographic, and clinical signs; cranial computed tomography (CT); ophthalmology examination; anti-seizure medication; growth; and motor development were collected. Fisher's exact test was used to verify the associations between categorical variables, and the T- test was used to compare the mean z-scores of anthropometric measurements between the groups with and without CED. ResultsCEDs were identified in 41 (54.67 %) children. The mean age of CEDs identification was 12.24 ± 6.86 months. Bilateral CEDs were shown in 62.89 % of EEGs. CEDs were associated with severe congenital microcephaly, defined by z-score >3 standard deviation of head circumference (HC) below the mean for sex and age (p = 0.025), and worse outcomes, including first seizure before 6 months (p = 0.004), drug-resistant epilepsy (p < 0.001), chorioretinal scarring or mottling (p = 0.002), and severe CT findings (p = 0.002). The CED group had lower mean z-scores of HC up to 24 months of age. ConclusionThis is the first description of the prevalence and significance of CEDs that also remains during wakefulness in patients with CZS. New investigations may suggest that it is more appropriate to classify the EEG not as a CED, but as a periodic pattern. Anyway, CEDs may be a marker of neurological severity in children with CSZ.

Further evidence supporting the role of GTDC1 in glycine metabolism and neurodevelopmental disorders

Copy number variants (CNVs) represent the genetic cause of about 15–20% of neurodevelopmental disorders (NDDs). We identified a ~67 kb de novo intragenic deletion on chromosome 2q22.3 in a female individual showing a developmental encephalopathy characterised by epilepsy, severe intellectual disability, speech delay, microcephaly, and thin corpus callosum with facial dysmorphisms. The microdeletion involved exons 5-6 of GTDC1, encoding a putative glycosyltransferase, whose expression is particularly enriched in the nervous system. In a previous study, a balanced de novo translocation encompassing GTDC1 was reported in a male child with global developmental delay and delayed speech and language development. Based on these premises, we explored the transcriptomic profile of our proband to evaluate the functional consequences of the novel GTDC1 de novo intragenic deletion in relation to the observed neurodevelopmental phenotype. RNA-seq on the proband’s lymphoblastoid cell line (LCL) showed expression changes of glycine/serine and cytokine/chemokine signalling pathways, which are related to neurodevelopment and epileptogenesis. Subsequent analysis by ELISA (enzyme-linked immunosorbent assay) and HPLC (high-performance liquid chromatography) revealed increased levels of glycine in the proband’s LCL and serum compared to matched controls. Given that an increased level of glycine has been observed in the plasma samples of individuals with Rett syndrome, a condition sharing epilepsy, microcephaly, and intellectual disability with our proband, we proposed that the GTDC1 downregulation is implicated in neurodevelopmental impairment by altering glycine metabolism. Furthermore, our findings expanded the phenotypic spectrum of the novel GTDC1-related condition, including microcephaly and epilepsy among relevant clinical features.

Long-Term Growth and Neurodevelopmental Outcomes of Neonates Infected with SARS-CoV-2 during the COVID-19 Pandemic at 18–24 Months Corrected Age: A Prospective Observational Study

Introduction: During the early coronavirus disease (COVID-19) pandemic in 2020, researchers cautioned about the potential neuroinvasive capability of the virus and long-term neurological consequences. Although a few preliminary studies have found delayed communication, fine motor, and problem-solving skills in infants after COVID-19 infection, there continues to be a paucity of data on long-term development of neonates diagnosed with COVID-19. Methods: We conducted a prospective study of 20 neonates who acquired severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection during the first wave of the pandemic (April–July 2020). At 18–24 months corrected age, we assessed neurodevelopment by Bayley Scales of Infant and Toddler Development, the third edition (BSID-III), along with growth, hearing, and vision evaluation. Results: The mean corrected age at assessment was 21 months 11 days ± 1 month 28 days. We found developmental delay in nearly half of the children with scores below one standard deviation in either of the BSID-III domains. Mild delay in either motor, cognitive, or language domains was found in 9 (45%) children and moderate delay in 2 (10%). Expressive language, fine motor, and receptive language were predominantly affected. None of the children had hearing impairment, blindness, or significant growth faltering including clinically severe microcephaly. The mean composite cognitive, language, and motor scores were significantly lower in those with neurodevelopmental delay (p value – 0.02, 0.000, and 0.03, respectively) without any differences in their disease characteristics. Conclusion: Neonates infected with SARS-CoV-2 have an increased risk of developmental delays in expressive language, fine motor, and receptive language skills at 18–24 months of age. The severity of delays is predominantly mild.

Viral infections in pregnancy and impact on offspring neurodevelopment: mechanisms and lessons learned.

Pregnant individuals with viral illness may experience significant morbidity and have higher rates of pregnancy and neonatal complications. With the growing number of viral infections and new viral pandemics, it is important to examine the effects of infection during pregnancy on both the gestational parent and the offspring. Febrile illness and inflammation during pregnancy are correlated with risk for autism, attention deficit/hyperactivity disorder, and developmental delay in the offspring in human and animal models. Historical viral epidemics had limited follow-up of the offspring of affected pregnancies. Infants exposed to seasonal influenza and the 2009 H1N1 influenza virus experienced increased risks of congenital malformations and neuropsychiatric conditions. Zika virus exposure in utero can lead to a spectrum of abnormalities, ranging from severe microcephaly to neurodevelopmental delays which may appear later in childhood and in the absence of Zika-related birth defects. Vertical infection with severe acute respiratory syndrome coronavirus-2 has occurred rarely, but there appears to be a risk for developmental delays in the infants with antenatal exposure. Determining how illness from infection during pregnancy and specific viral pathogens can affect pregnancy and neurodevelopmental outcomes of offspring can better prepare the community to care for these children as they grow. IMPACT: Viral infections have impacted pregnant people and their offspring throughout history. Antenatal exposure to maternal fever and inflammation may increase risk of developmental and neurobehavioral disorders in infants and children. The recent SARS-CoV-2 pandemic stresses the importance of longitudinal studies to follow pregnancies and offspring neurodevelopment.

Report of a New Pediatric Patient with the SLC1A4 Variant and a Brief Review of the Literature

AbstractSpastic tetraplegia, thin corpus callosum, and progressive microcephaly (SPATCCM) is an autosomal recessive disorder characterized by the onset of those features and severely impaired global development in early infancy, and caused by biallelic deleterious SLC1A4 variants. SLC1A4 encodes for the neutral amino acid transporter, ASCT1, which is necessary for L-serine and D-serine cellular transport to neurons. The objective of this study was to contribute to the genotype–phenotype correlation of SLC1A4 variants. We evaluated a Turkish patient presenting with SPATCCM without seizures and reviewed all previously reported cases of the SLC1A4 mutation. Whole exome sequencing revealed a missense biallelic p.R457W variant in SLC1A4 in a child of Palestinian origin. We suggest that the SLC1A4 should be considered in the diagnosis of unexplained severe early-onset neurodevelopmental impairment, progressive microcephaly, and spastic tetraparesis with or without epilepsy, regardless of ethnicity and encourage the analysis of SLC1A4 variants via molecular genetic testing. The presence or absence of epilepsy should not distract from the diagnosis.

Nucleotide metabolism, leukodystrophies, and CNS pathology.

The balance between a protective and a destructive immune response can be precarious, as exemplified by inborn errors in nucleotide metabolism. This class of inherited disorders, which mimics infection, can result in systemic injury and severe neurologic outcomes. The most common of these disorders is Aicardi Goutières syndrome (AGS). AGS results in a phenotype similar to "TORCH" infections (Toxoplasma gondii, Other [Zika virus (ZIKV), human immunodeficiency virus (HIV)], Rubella virus, human Cytomegalovirus [HCMV], and Herpesviruses), but with sustained inflammation and ongoing potential for complications. AGS was first described in the early 1980s as familial clusters of "TORCH" infections, with severe neurology impairment, microcephaly, and basal ganglia calcifications (Aicardi & Goutières, Ann Neurol, 1984;15:49-54) and was associated with chronic cerebrospinal fluid (CSF) lymphocytosis and elevated type I interferon levels (Goutières et al., Ann Neurol, 1998;44:900-907). Since its first description, the clinical spectrum of AGS has dramatically expanded from the initial cohorts of children with severe impairment to including individuals with average intelligence and mild spastic paraparesis. This broad spectrum of potential clinical manifestations can result in a delayed diagnosis, which families cite as a major stressor. Additionally, a timely diagnosis is increasingly critical with emerging therapies targeting the interferon signaling pathway. Despite the many gains in understanding about AGS, there are still many gaps in our understanding of the cell-type drivers of pathology and characterization of modifying variables that influence clinical outcomes and achievement of timely diagnosis.

Analysis of congenital Zika syndrome clinicopathologic findings reported in the 8 years since the Brazilian outbreak

Aim: A Zika virus outbreak that began in Brazil, developed into an international public health emergency that extended from February 2015 until November 2016. Zika-infected pregnant women gave birth to a cohort of infants with congenital Zika syndrome (CZS) originally defined by severe microcephaly, retinal scarring, joint deformities, and hypertonia. This study examines the nature, extent, and severity of all CZS clinicopathologic findings described to date, compiled and analyzed by system. It reviews studies monitoring disease progression and proposing classification schemes for CZS stages. The teratogenic cellular and molecular mechanisms implicated in CZS pathogenesis are also discussed. Methods: A systematic review was conducted by literature search through WorldCat.org and ProQuest Central databases to identify studies on case series from the 2015–2016 CZS outbreak. Results: Twenty-six reports were included describing radiologic, ophthalmologic, audiologic, orthopedic, and laboratory test results in CZS cases including stillborns between 2016 and 2023. CZS neuropathology included prenatal and postnatal microcephaly, cerebral calcifications, quadriparesis, epilepsy, ventriculomegaly, reduced cerebral parenchyma, malformation of cortical development, and sleep electroencephalogram disturbances. Visual deficits were due to retinal and optic nerve lesions. Conductive and sensorineural hearing deficits were stable. Hypertonia, hypotonia, and spasticity with foot, hip, knee, and shoulder deformities resulted in arthrogryposis and restricted joint mobility. There was enlargement of immune organs, increased leukocyte counts, and cytokine dysregulation. Oro-craniofacial deformities affected the midface and caused dental eruption delay. Additional studies proposed that these systemic teratogenic effects could be attributable to transplacental Zika virus infection of multiple fetal progenitor cell lineages. Conclusions: The CZS-associated impairments in brain, eye, musculoskeletal, and immunologic functions caused disabilities that varied from moderate to severe, and significantly increased age-specific mortality rates. Further research is warranted to assess progression, classify stages, elucidate the precise molecular mechanisms mediating Zika teratogenicity, develop suitable therapeutic strategies, and design supportive social policies.

Impact of maternal first trimester treatment regimen on the outcome of valproate exposed pregnancies: an observational Embryotox cohort study

Effects of valproate (VPA) dose and treatment discontinuation during the first trimester of pregnancy on the risks of spontaneous abortions (SAB) and major birth defects were analyzed. Pregnancies with first trimester VPA exposure (n = 484) prospectively recorded by the German Embryotox center in 1997–2016 were compared with a randomly selected, non-exposed cohort (n = 1446). The SAB risk was not significantly increased in the VPA cohort [HRadj 1.31 (95% CI 0.85–2.02)] but major birth defects were significantly more frequent [8.7% vs. 3.4%; ORadj 2.61 (95% CI 1.51–4.50)]. Risk was even higher in pregnancies with no VPA discontinuation in first trimester [ORadj 3.66 (95% CI 2.04–6.54)]. Significant ORs were found for nervous system defects in general [ORadj 5.69 (95% CI 1.73–18.78)], severe microcephaly [ORadj 6.65 (95% CI 1.17–37.68)], hypospadias [ORadj 19.49 (95% CI 1.80–211)] and urinary system defects [ORadj 6.51 (95% CI 1.48–28.67)]. VPA dose had a stronger effect than antiepileptic poly- versus monotherapy; for VPA dose ≥ 1500 mg/day the ORadj was 5.41 (95% CI 2.32–12.66)]. A daily dose increase of 100 mg was calculated to raise the risk for major birth defects by 15% [OR 1.15 (95% CI 1.08–1.23)]. Overall, maternal first trimester treatment regimen had a relevant impact on birth defect risk.

Clinical spectrum of congenital Zika virus infection in Brazil: Update and issues for research development.

This review aimed to provide an update on the morphological and/or functional abnormalities related to congenital Zika virus (ZIKV) infection, based on primary data from studies conducted in Brazil since 2015. During the epidemic years (2015-2016), case series and pediatric cohort studies described several birth defects, including severe and/or disproportionate microcephaly, cranial bone overlap, skull collapse, congenital contractures (arthrogryposis and/or clubfoot), and visual and hearing abnormalities, as part of the spectrum of Congenital Zika Syndrome (CZS). Brain imaging abnormalities, mainly cortical atrophy, ventriculomegaly, and calcifications, serve as structural markers of CZS severity. Most case series and cohorts of microcephaly have reported the co-occurrence of epilepsy, dysphagia, orthopedic deformities, motor function impairment, cerebral palsy, and urological impairment. A previous large meta-analysis conducted in Brazil revealed that a confirmed ZIKV infection during pregnancy was associated with a 4% risk of microcephaly. Additionally, one-third of children showed at least one abnormality, predominantly identified in isolation. Studies examining antenatally ZIKV-exposed children without detectable abnormalities at birth reported conflicting neurodevelopmental results. Therefore, long-term follow-up studies involving pediatric cohorts with appropriate control groups are needed to address this knowledge gap. We recognize the crucial role of a national network of scientists collaborating with international research institutions in understanding the lifelong consequences of congenital ZIKV infection. Additionally, we highlight the need to provide sustainable resources for research and development to reduce the risk of future Zika outbreaks.

Bi-allelic variants in CEP295 cause Seckel-like syndrome presenting with primary microcephaly, developmental delay, intellectual disability, short stature, craniofacial and digital abnormalities

Pathogenic variants in the centrosome protein (CEP) family have been implicated in primary microcephaly, Seckel syndrome, and classical ciliopathies. However, most CEP genes remain unlinked to specific Mendelian genetic diseases in humans. We sought to explore the roles of CEP295 in human pathology. Whole-exome sequencing was performed to screen for pathogenic variants in patients with severe microcephaly. Patient-derived fibroblasts and CEP295-depleted U2OS and RPE1 cells were used to clarify the underlying pathomechanisms, including centriole/centrosome development, cell cycle and proliferation changes, and ciliogenesis. Complementary experiments using CEP295 mRNA were performed to determine the pathogenicity of the identified missense variant. Here, we report bi-allelic variants of CEP295 in four children from two unrelated families, characterized by severe primary microcephaly, short stature, developmental delay, intellectual disability, facial deformities, and abnormalities of fingers and toes, suggesting a Seckel-like syndrome. Mechanistically, depletion of CEP295 resulted in a decrease in the numbers of centrioles and centrosomes and triggered p53-dependent G1 cell cycle arrest. Moreover, loss of CEP295 causes extensive primary ciliary defects in both patient-derived fibroblasts and RPE1 cells. The results from complementary experiments revealed that the wild-type CEP295, but not the mutant protein, can correct the developmental defects of the centrosome/centriole and cilia in the patient-derived skin fibroblasts. This study reports CEP295 as a causative gene of the syndromic microcephaly phenotype in humans. Our study also demonstrates that defects in CEP295 result in primary ciliary defects. A full list of funding bodies that contributed to this study can be found under "Acknowledgments."

Microglial zinc finger protein 335 mediates LPS‐induced neurodegeneration and memory loss as a transcriptional factor for lymphocyte antigen‐6M

AbstractBackgroundZinc finger protein 335 (Zfp335) is a transcription factor that regulates mammalian neurogenesis and neuronal differentiation. It is a causative factor for severe microcephaly, small somatic size, and neonatal death. Here, we evaluated the effects of Zfp335 in the adult mouse brain after lipopolysaccharide (LPS) challenge.MethodWe used wild‐type (WT) and Zfp335 knock‐down (Zfp335+/−) mice with LPS administered in the intracerebral ventricle in vivo and cultured microglia treated with LPS in vitro. The impact of Zfp335 was evaluated by RT‐PCR, RNA‐sequencing, western blotting, immunocytochemistry, ELISA, and the memory behavior tests. Knockdown of Zfp335 expression ameliorated microglia activation significantly, including reduced mRNA and protein expression of Iba1, reduced numbers of microglia, reduced cell diameter, and increased branch length, in the brains of 2‐month‐old mice after LPS treatment.ResultZfp335 was expressed in microglia and neurons, but increased in microglia, not neurons, in the brain of mice after LPS administration. LPS‐induced microglia‐mediated neurodegeneration was dependent upon microglial Zfp335 controlled by nuclear factor‐kappa B. Microglial Zfp335 affected neuronal activity through transcriptional regulation of lymphocyte antigen‐6M (Ly6M).ConclusionOur data suggest that Zfp335 is a key transcription factor that exacerbates microglia‐mediated neurodegeneration through upregulation of Ly6M expression. Inhibition of microglial Zfp335 may be a new strategy for preventing brain disease induced by microglia activation.