Mono-allelic KCNB2 variants lead to a neurodevelopmental syndrome caused by altered channel inactivation.

Ion channels mediate voltage fluxes or action potentials that are central to the functioning of excitable cells such as neurons. The KCNB family of voltage-gated potassium channels (Kv) consists of two members (KCNB1 and KCNB2) encoded by KCNB1 and KCNB2, respectively. These channels are major contributors to delayed rectifier potassium currents arising from the neuronal soma which modulate overall excitability of neurons. In this study, we identified several mono-allelic pathogenic missense variants in KCNB2, in individuals with a neurodevelopmental syndrome with epilepsy and autism in some individuals. Recurrent dysmorphisms included a broad forehead, synophrys, and digital anomalies. Additionally, we selected three variants where genetic transmission has not been assessed, from two epilepsy studies, for inclusion in our experiments. We characterized channel properties of these variants by expressing them in oocytes of Xenopus laevis and conducting cut-open oocyte voltage clamp electrophysiology. Our datasets indicate no significant change in absolute conductance and conductance-voltage relationships of most disease variants as compared to wild type (WT), when expressed either alone or co-expressed with WT-KCNB2. However, variants c.1141A>G (p.Thr381Ala) and c.641C>T (p.Thr214Met) show complete abrogation of currents when expressed alone with the former exhibiting a left shift in activation midpoint when expressed alone or with WT-KCNB2. The variants we studied, nevertheless, show collective features of increased inactivation shifted to hyperpolarized potentials. We suggest that the effects of the variants on channel inactivation result in hyper-excitability of neurons, which contributes to disease manifestations.

Heterozygous loss-of-function variants significantly expand the phenotypes associated with loss of GDF11.

PURPOSE: Growth differentiation factor 11 (GDF11) is a key signaling protein required for proper development of many organ systems. Only one prior study has associated an inherited GDF11 variant with a dominant human disease in a family with variable craniofacial and vertebral abnormalities. Here, we expand the phenotypic spectrum associated with GDF11 variants and document the nature of the variants. METHODS: We present a cohort of six probands with de novo and inherited nonsense/frameshift (4/6 patients) and missense (2/6) variants in GDF11. We generated gdf11 mutant zebrafish to model loss of gdf11 phenotypes and used an overexpression screen in Drosophila to test variant functionality. RESULTS: Patients with variants in GDF11 presented with craniofacial (5/6), vertebral (5/6), neurological (6/6), visual (4/6), cardiac (3/6), auditory (3/6), and connective tissue abnormalities (3/6). gdf11 mutant zebrafish show craniofacial abnormalities and body segmentation defects that match some patient phenotypes. Expression of the patients' variants in the fly showed that one nonsense variant in GDF11 is a severe loss-of-function (LOF) allele whereas the missense variants in our cohort are partial LOF variants. CONCLUSION: GDF11 is needed for human development, particularly neuronal development, and LOF GDF11 alleles can affect the development of numerous organs and tissues.

Updating the neurodevelopmental profile of Alazami syndrome: Illustrating the role of developmental assessment in rare genetic disorders.

Alazami syndrome, caused by biallelic pathogenic variants in LARP7, is a recently-described rare genetic disorder, with 17 patients currently reported in the literature. We present a case of a male infant referred for genetics evaluation at 5 months of age, found at 17 months of age to have Alazami syndrome. He was promptly referred for developmental evaluation, where he was found to be higher functioning than prior reports of individuals with this condition. This demonstrates the neurodevelopmental phenotypic variability seen in rare genetic disorders; it also demonstrates the important role of developmental programs to measure and track outcomes and provide support for infants with genetic disorders that put them at risk of developmental disabilities.

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.355C>T [p.Arg119Cys] and c.751C>T [p.Arg251Cys]) in PYCR2 in the affected individuals of two consanguineous families. A lymphoblastoid cell line from one affected individual showed a strong reduction in the amount of PYCR2. When mutant cDNAs were transfected into HEK293FT cells, both variant proteins retained normal mitochondrial localization but had lower amounts than the wild-type protein, suggesting that the variant proteins were less stable. A PYCR2-deficient HEK293FT cell line generated by genome editing with the clustered regularly interspaced short palindromic repeat (CRISPR)-Cas9 system showed that PYCR2 loss of function led to decreased mitochondrial membrane potential and increased susceptibility to apoptosis under oxidative stress. Morpholino-based knockdown of a zebrafish PYCR2 ortholog, pycr1b, recapitulated the human microcephaly phenotype, which was rescued by wild-type human PYCR2 mRNA, but not by mutant mRNAs, further supporting the pathogenicity of the identified variants. Hypomyelination and the absence of lax, wrinkly skin distinguishes this condition from that caused by previously reported mutations in the gene encoding PYCR2's isozyme, PYCR1, suggesting a unique and indispensable role for PYCR2 in the human CNS during development.

Pulmonary Vasculopathy Associated with FIGF Gene Mutation.

Vascular endothelial growth factor (VEGF)-D is capable of inducing angiogenesis and lymphangiogenesis through signaling via VEGF receptor (VEGFR)-2 and VEGFR-3, respectively. Mutations in the FIGF (c-fos-induced growth factor) gene encoding VEGF-D have not been reported previously. We describe a young male with a hemizygous mutation in the X-chromosome gene FIGF (c.352 G>A) associated with early childhood respiratory deficiency. Histologically, lungs showed ectatic pulmonary arteries and pulmonary veins. The mutation resulted in a substitution of valine to methionine at residue 118 of the VEGF-D protein. The resultant mutant protein had increased dimerization, induced elevated VEGFR-2 signaling, and caused aberrant angiogenesis in vivo. Our observations characterize a new subtype of congenital diffuse lung disease, provide a histological correlate, and support a critical role for VEGF-D in lung vascular development and homeostasis.

Utility of Genetic Testing in Fetal Alcohol Spectrum Disorder.

OBJECTIVE: To study the utility of genetic evaluation and testing in patients with suspected fetal alcohol spectrum disorder (FASD). STUDY DESIGN: We performed a retrospective chart review of all patients (n = 36) referred for evaluation for suspected FASD to the genetics clinic at Boston Children's Hospital between January 2006 and January 2013. Records of all patients were reviewed to obtain the medical history, family history, examination findings, and investigations, including genetic testing. RESULTS: Of the 36 patients, definite prenatal exposure was documented in 69%. Eight patients did not fulfill clinical criteria for FASD. Chromosomal microarray analysis (CMA) detected 19 copy number variants (CNVs) in 14 patients. Among patients who fulfilled criteria for FASD and underwent CMA, pathogenic CNVs were detected in 3 patients (2q37del, 22q11.22dup, and 4q31.21del syndromes), giving a yield of 14.3%. All 3 patients had overlapping features between FASD and the genetic syndrome. CONCLUSION: Genetic testing, especially CMA, should be considered in patients referred for evaluation of FASD, as a significant proportion have a clinically significant CNV even when they fulfill diagnostic criteria for FASD spectrum.

Genetic and phenotypic dissection of 1q43q44 microdeletion syndrome and neurodevelopmental phenotypes associated with mutations in ZBTB18 and HNRNPU.

Subtelomeric 1q43q44 microdeletions cause a syndrome associating intellectual disability, microcephaly, seizures and anomalies of the corpus callosum. Despite several previous studies assessing genotype-phenotype correlations, the contribution of genes located in this region to the specific features of this syndrome remains uncertain. Among those, three genes, AKT3, HNRNPU and ZBTB18 are highly expressed in the brain and point mutations in these genes have been recently identified in children with neurodevelopmental phenotypes. In this study, we report the clinical and molecular data from 17 patients with 1q43q44 microdeletions, four with ZBTB18 mutations and seven with HNRNPU mutations, and review additional data from 37 previously published patients with 1q43q44 microdeletions. We compare clinical data of patients with 1q43q44 microdeletions with those of patients with point mutations in HNRNPU and ZBTB18 to assess the contribution of each gene as well as the possibility of epistasis between genes. Our study demonstrates that AKT3 haploinsufficiency is the main driver for microcephaly, whereas HNRNPU alteration mostly drives epilepsy and determines the degree of intellectual disability. ZBTB18 deletions or mutations are associated with variable corpus callosum anomalies with an incomplete penetrance. ZBTB18 may also contribute to microcephaly and HNRNPU to thin corpus callosum, but with a lower penetrance. Co-deletion of contiguous genes has additive effects. Our results confirm and refine the complex genotype-phenotype correlations existing in the 1qter microdeletion syndrome and define more precisely the neurodevelopmental phenotypes associated with genetic alterations of AKT3, ZBTB18 and HNRNPU in humans.

Musculoskeletal Conditions in a Pediatric Population with Ehlers-Danlos Syndrome.

OBJECTIVE: To describe musculoskeletal conditions in children with Ehlers-Danlos syndrome (EDS). STUDY DESIGN: A retrospective medical record review was performed, which evaluated 205 patients with EDS (ages 6-19 years) seen in sports medicine or orthopedic clinic at a large pediatric hospital over a 5-year period. RESULTS: Female (n = 147) and male (n = 57) patients were identified (mean age 12.7 years). The most common EDS subtype (55.6%) was hypermobility type. Patients had between 1 and 69 visits (median 4), and 764 diagnoses were recorded, most commonly laxity/instability, pain, subluxation, and scoliosis/spinal asymmetry. Nearly one-half of patients (46.8%) received a general diagnosis of pain because no more specific cause was identified, in addition to 8.3% who were diagnosed with chronic pain syndrome. The most common sites of presenting issue were knee (43.4%), back (32.2%), and shoulder (31.2%). Over three-fourths (77.1%) of patients had imaging. Most (88.1%) were prescribed physical therapy and/or other conservative measures, such as rest (40.5%), orthotics (35.6%), and medication (32.2%). Surgery was recommended to 28.8% of the study population. CONCLUSIONS: Many pediatric and adolescent patients with EDS experience joint pain, instability, and scoliosis, along with other musculoskeletal issues. Despite extensive workup, the etiology of pain may not be identified. Large numbers of office visits, imaging studies, treatment prescriptions, and specialist referrals indicate considerable use of medical resources and highlight a great need for injury prevention and additional study.

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.3145C>T; p.R1049X) in four affected individuals from two unrelated consanguineous families. The affected individuals in our report were diagnosed with postnatal microcephaly, early-onset epilepsy, severe vision impairment, and pulmonary symptoms including bronchiectasis and recurrent respiratory infections. A heterozygous DIAPH1 mutation was originally reported in one family with autosomal dominant deafness. Recently, however, a homozygous nonsense DIAPH1 mutation (c.2332C4T; p.Q778X) was reported in five siblings in a single family affected by microcephaly, blindness, early onset seizures, developmental delay, and bronchiectasis. The role of DIAPH1 was supported using parametric linkage analysis, RNA and protein studies in their patients' cell lines and further studies in human neural progenitors cells and a diap1 knockout mouse. In this report, the proband was initially brought to medical attention for profound metopic synostosis. Additional concerns arose when his head circumference did not increase after surgical release at 5 months of age and he was diagnosed with microcephaly and epilepsy at 6 months of age. Clinical exome analysis identified a homozygous DIAPH1 mutation. Another homozygous DIAPH1 mutation was identified in the research exome analysis of a second family with three siblings presenting with a similar phenotype. Importantly, no hearing impairment is reported in the homozygous affected individuals or in the heterozygous carrier parents in any of the families demonstrating the autosomal recessive microcephaly phenotype. These additional families provide further evidence of the likely causal relationship between DIAPH1 mutations and a neurodevelopmental disorder.

Copy number variation plays an important role in clinical epilepsy.

OBJECTIVE: To evaluate the role of copy number abnormalities detectable using chromosomal microarray (CMA) testing in patients with epilepsy at a tertiary care center. METHODS: We identified patients with International Classification of Diseases, ninth revision (ICD-9) codes for epilepsy or seizures and clinical CMA testing performed between October 2006 and February 2011 at Boston Children's Hospital. We reviewed medical records and included patients who met criteria for epilepsy. We phenotypically characterized patients with epilepsy-associated abnormalities on CMA. RESULTS: Of 973 patients who had CMA and ICD-9 codes for epilepsy or seizures, 805 patients satisfied criteria for epilepsy. We observed 437 copy number variants (CNVs) in 323 patients (1-4 per patient), including 185 (42%) deletions and 252 (58%) duplications. Forty (9%) were confirmed de novo, 186 (43%) were inherited, and parental data were unavailable for 211 (48%). Excluding full chromosome trisomies, CNV size ranged from 18kb to 142Mb, and 34% were >500kb. In at least 40 cases (5%), the epilepsy phenotype was explained by a CNV, including 29 patients with epilepsy-associated syndromes and 11 with likely disease-associated CNVs involving epilepsy genes or "hotspots." We observed numerous recurrent CNVs including 10 involving loss or gain of Xp22.31, a region described in patients with and without epilepsy. INTERPRETATION: Copy number abnormalities play an important role in patients with epilepsy. Because the diagnostic yield of CMA for epilepsy patients is similar to the yield in autism spectrum disorders and in prenatal diagnosis, for which published guidelines recommend testing with CMA, we recommend the implementation of CMA in the evaluation of unexplained epilepsy.

Progressive Postnatal Pansynostosis.

OBJECTIVE: To describe the subtle clinical features, genetic considerations, and management of progressive postnatal pansynostosis, a rare form of multisutural craniosynostosis that insidiously occurs after birth and causes inconspicuous cranial changes. Design, Participants, Setting : The study is a retrospective chart review of all patients diagnosed with progressive postnatal pansynostosis at a major craniofacial center between 2000 and 2009. Patients with kleebattschädel were excluded. RESULTS: Nineteen patients fit our inclusion criteria. Fifteen patients had a syndromic diagnosis: Crouzon syndrome (n = 8), Saethre-Chotzen syndrome (n = 5), and Pfeiffer syndrome (n = 2). With the exception of one patient with moderate turricephaly, all patients had a relatively normal head shape with cranial indices ranging from 0.72 to 0.93 (mean, 0.81). Patients were diagnosed at an average of 32.4 months; craniosynostosis was suspected based on declining percentile head circumference (n = 14), detection of an apical prominence (n = 12), papilledema (n = 7), and worsening exorbitism (n = 3). Nearly all patients had evidence of increased intracranial pressure. CONCLUSION: Progressive postnatal pansynostosis is insidious; diagnosis is typically delayed because the clinical signs are subtle and appear gradually. All infants or children with known or suspected craniosynostotic disorder and a normal head shape should be carefully monitored; computed tomography is indicated if there is any decrease in percentile head circumference or symptoms of intracranial pressure.

Heterozygous rare variants in NR2F2 cause a recognizable multiple congenital anomaly syndrome with developmental delays.

Nuclear receptor subfamily 2 group F member 2 (NR2F2 or COUP-TF2) encodes a transcription factor which is expressed at high levels during mammalian development. Rare heterozygous Mendelian variants in NR2F2 were initially identified in individuals with congenital heart disease (CHD), then subsequently in cohorts of congenital diaphragmatic hernia (CDH) and 46,XX ovotesticular disorders/differences of sexual development (DSD); however, the phenotypic spectrum associated with pathogenic variants in NR2F2 remains poorly characterized. Currently, less than 40 individuals with heterozygous pathogenic variants in NR2F2 have been reported. Here, we review the clinical and molecular details of 17 previously unreported individuals with rare heterozygous NR2F2 variants, the majority of which were de novo. Clinical features were variable, including intrauterine growth restriction (IUGR), CHD, CDH, genital anomalies, DSD, developmental delays, hypotonia, feeding difficulties, failure to thrive, congenital and acquired microcephaly, dysmorphic facial features, renal failure, hearing loss, strabismus, asplenia, and vascular malformations, thus expanding the phenotypic spectrum associated with NR2F2 variants. The variants seen were predicted loss of function, including a nonsense variant inherited from a mildly affected mosaic mother, missense and a large deletion including the NR2F2 gene. Our study presents evidence for rare, heterozygous NR2F2 variants causing a highly variable syndrome of congenital anomalies, commonly associated with heart defects, developmental delays/intellectual disability, dysmorphic features, feeding difficulties, hypotonia, and genital anomalies. Based on the new and previous cases, we provide clinical recommendations for evaluating individuals diagnosed with an NR2F2-associated disorder.

Magnetic resonance imaging for detection of brain abnormalities in fetuses with cleft lip and/or cleft palate.

OBJECTIVE: To determine the prevalence of brain abnormalities identified by prenatal imaging of fetuses with cleft lip with or without cleft palate (CL/P) or cleft palate only (CP) and to compare with postnatal imaging and neurologic evaluation. DESIGN: This was a retrospective review of radiologic images (magnetic resonance imaging [MRI] and sonography) of fetuses diagnosed with CL/P or CP at the Advanced Fetal Care Center at Children's Hospital Boston between 2002 and 2008. Images were reviewed for possible brain abnormalities by a pediatric radiologist who specializes in this field. Postnatal imaging was also assessed whenever available and correlated with clinical findings. SETTING: A large, tertiary-care, academic pediatric hospital. POPULATION: One hundred twenty-six fetuses and 105 corresponding infants. RESULTS: Brain abnormalities were found in 8 of 126 fetuses (6.3%) by prenatal MRI. The malformations were corpus callosal dysgenesis (n = 3), encephalocele (n = 1), hypoplasia of the cerebellar hemispheres or vermis (n = 3), and white matter neuronal migration anomaly (n = 1). An additional 2 patients were diagnosed with brain abnormalities postnatally that had not been detected on prenatal imaging. CONCLUSIONS: The possibility of brain anomalies should be assessed in a fetus found to have CL/P or CP by sonography and/or MRI. Central nervous system imaging and careful neurodevelopmental follow-up is indicated in these infants.

FOXE3 plays a significant role in autosomal recessive microphthalmia.

FOXE3 forkhead transcription factor is essential to lens development in vertebrates. The eyes of Foxe3/foxe3-deficient mice and zebrafish fail to develop normally. In humans, autosomal dominant and recessive mutations in FOXE3 have been associated with variable phenotypes including anterior segment anomalies, cataract, and microphthalmia. We undertook sequencing of FOXE3 in 116 probands with a spectrum of ocular defects ranging from anterior segment dysgenesis and cataract to anophthalmia/microphthalmia. Recessive mutations in FOXE3 were found in four of 26 probands affected with bilateral microphthalmia (15% of all bilateral microphthalmia and 100% of consanguineous families with this phenotype). FOXE3-positive microphthalmia was accompanied by aphakia and/or corneal defects; no other associated systemic anomalies were observed in FOXE3-positive families. The previously reported c.720C > A (p.C240X) nonsense mutation was identified in two additional families in our sample and therefore appears to be recurrent, now reported in three independent microphthalmia families of varied ethnic backgrounds. Several missense variants were identified at varying frequencies in patient and control groups with some apparently being race-specific, which underscores the importance of utilizing race/ethnicity-matched control populations in evaluating the relevance of genetic screening results. In conclusion, FOXE3 mutations represent an important cause of nonsyndromic autosomal recessive bilateral microphthalmia.

Deletions of NRXN1 (neurexin-1) predispose to a wide spectrum of developmental disorders.

Research has implicated mutations in the gene for neurexin-1 (NRXN1) in a variety of conditions including autism, schizophrenia, and nicotine dependence. To our knowledge, there have been no published reports describing the breadth of the phenotype associated with mutations in NRXN1. We present a medical record review of subjects with deletions involving exonic sequences of NRXN1. We ascertained cases from 3,540 individuals referred clinically for comparative genomic hybridization testing from March 2007 to January 2009. Twelve subjects were identified with exonic deletions. The phenotype of individuals with NRXN1 deletion is variable and includes autism spectrum disorders, mental retardation, language delays, and hypotonia. There was a statistically significant increase in NRXN1 deletion in our clinical sample compared to control populations described in the literature (P = 8.9 x 10(-7)). Three additional subjects with NRXN1 deletions and autism were identified through the Homozygosity Mapping Collaborative for Autism, and this deletion segregated with the phenotype. Our study indicates that deletions of NRXN1 predispose to a wide spectrum of developmental disorders.

Recent developments in fetal alcohol spectrum disorder.

PURPOSE OF REVIEW: To highlight research, publications, and medical advancements in fetal alcohol spectrum disorder (FASD) over the past 18 months. RECENT FINDINGS: Prevalence numbers have been updated, allowing for a more accurate account of the societal impact. Further work on diagnostic techniques and the underlying mechanisms will allow us to better understand the pathophysiology of FASD and could translate into treatments for the condition. Continued research on new treatments and interventions is needed to improve the affected individual's health care and quality of life. Measurable outcomes allow us to tangibly measure improvements for individuals and families affected by FASD. SUMMARY: The current review highlights recent publications from January 2018 to August 2019 showing continued medical advancement in improving the care for children and families affected by FASD.

Mitral valve prolapse in Marfan syndrome: an old topic revisited.

BACKGROUND: The echocardiographic features of mitral valve prolapse (MVP) in Marfan syndrome have been well described, and the incidence of MVP in Marfan syndrome is reported to be 40-80%. However, most of the original research was performed in the late 1980s and early 1990s, when the diagnostic criteria for MVP were less specific. Our goal was to investigate the characteristics of MVP associated with Marfan syndrome using currently accepted diagnostic criteria for MVP. METHODS: Between January 1990 and March 2004, 90 patients with definitive diagnosis of Marfan syndrome (based on standardized criteria with or without genetic testing) were referred to Massachusetts General Hospital for transthoracic echocardiography. Patients' gender, age, weight, height, and body surface area at initial examination were recorded. Mitral valve thickness and motion, the degree of mitral regurgitation and aortic regurgitation, and aortic dimensions were quantified blinded to patients' clinical information. RESULTS: There were 25 patients (28%) with MVP, among whom 80% had symmetrical bileaflet MVP. Patients with MVP had thicker mitral leaflets (5.0 +/- 1.0 mm vs. 1.8 +/- 0.5 mm, P < 0.001), more mitral regurgitation (using a scale of 1-4, 2.2 +/- 1.0 vs. 0.90 +/- 0.60, P < 0.0001), larger LVEDD, and larger dimensions of sinus of Valsalva, sinotubular junction, aortic arch, and descending aorta indexed to square root body surface area, when compared with those without MVP. When echocardiographic features of patients younger than 18 years of age and those of patients older than 18 were compared, adult Marfan patients had larger LA dimension (indexed to square root body surface area), larger sinotubular junction (indexed to square root body surface area), and more mitral regurgitation and aortic regurgitation. CONCLUSIONS: The prevalence of MVP in Marfan syndrome is lower than previously reported. The large majority of patients with MVP have bileaflet involvement, and those with MVP have significantly larger aortic root diameters, suggesting a diffuse disease process.

Cleft palate in Pfeiffer syndrome.

The frequency of associated cleft palate is known to be high in some fibroblast growth factor receptor 2 (FGFR2)-mediated craniosynostosis syndromes, such as Apert syndrome. However, there is little information on the frequency of palatal clefts in the FGFR2-mediated disorder, that is, Pfeiffer syndrome. The purpose of this study was to determine the frequency of palatal clefts in patients with Pfeiffer syndrome. The records of patients with Pfeiffer syndrome managed in our craniofacial unit were reviewed. Only patients with a confirmed diagnosis of Pfeiffer syndrome were included. Diagnostic criteria were as follows: characteristic mutations in FGFR1 or FGFR2 or, in the absence of genetic testing, clinical findings consistent with Pfeiffer syndrome as determined by a clinical geneticist or our most experienced surgeon (J.B.M.). Only 2 clefts were noted in 25 patients (8%), including 1 with a submucous cleft and 1 with an overt palatal cleft. Many patients (87%) were described as having a high-arched and narrow palate, and 1 had a low, broad palate. Nine patients were noted to have choanal atresia or stenosis. Clefting of the palate does occur in Pfeiffer syndrome but at a low frequency.