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 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.

SPTSSA variants alter sphingolipid synthesis and cause a complex hereditary spastic paraplegia

Sphingolipids are a diverse family of lipids with critical structural and signalling functions in the mammalian nervous system, where they are abundant in myelin membranes. Serine palmitoyltransferase, the enzyme that catalyses the rate-limiting reaction of sphingolipid synthesis, is composed of multiple subunits including an activating subunit, SPTSSA. Sphingolipids are both essential and cytotoxic and their synthesis must therefore be tightly regulated. Key to the homeostatic regulation are the ORMDL proteins that are bound to serine palmitoyltransferase and mediate feedback inhibition of enzymatic activity when sphingolipid levels become excessive. Exome sequencing identified potential disease-causing variants in SPTSSA in three children presenting with a complex form of hereditary spastic paraplegia. The effect of these variants on the catalytic activity and homeostatic regulation of serine palmitoyltransferase was investigated in human embryonic kidney cells, patient fibroblasts and Drosophila. Our results showed that two different pathogenic variants in SPTSSA caused a hereditary spastic paraplegia resulting in progressive motor disturbance with variable sensorineural hearing loss and language/cognitive dysfunction in three individuals. The variants in SPTSSA impaired the negative regulation of serine palmitoyltransferase by ORMDLs leading to excessive sphingolipid synthesis based on biochemical studies and in vivo studies in Drosophila. These findings support the pathogenicity of the SPTSSA variants and point to excessive sphingolipid synthesis due to impaired homeostatic regulation of serine palmitoyltransferase as responsible for defects in early brain development and function.

Bi-allelic ATG4D variants are associated with a neurodevelopmental disorder characterized by speech and motor impairment

Autophagy regulates the degradation of damaged organelles and protein aggregates, and is critical for neuronal development, homeostasis, and maintenance, yet few neurodevelopmental disorders have been associated with pathogenic variants in genes encoding autophagy-related proteins. We report three individuals from two unrelated families with a neurodevelopmental disorder characterized by speech and motor impairment, and similar facial characteristics. Rare, conserved, bi-allelic variants were identified in ATG4D, encoding one of four ATG4 cysteine proteases important for autophagosome biogenesis, a hallmark of autophagy. Autophagosome biogenesis and induction of autophagy were intact in cells from affected individuals. However, studies evaluating the predominant substrate of ATG4D, GABARAPL1, demonstrated that three of the four ATG4D patient variants functionally impair ATG4D activity. GABARAPL1 is cleaved or "primed" by ATG4D and an in vitro GABARAPL1 priming assay revealed decreased priming activity for three of the four ATG4D variants. Furthermore, a rescue experiment performed in an ATG4 tetra knockout cell line, in which all four ATG4 isoforms were knocked out by gene editing, showed decreased GABARAPL1 priming activity for the two ATG4D missense variants located in the cysteine protease domain required for priming, suggesting that these variants impair the function of ATG4D. The clinical, bioinformatic, and functional data suggest that bi-allelic loss-of-function variants in ATG4D contribute to the pathogenesis of this syndromic neurodevelopmental disorder.

Continuing a search for a diagnosis: the impact of adolescence and family dynamics

The "diagnostic odyssey" describes the process those with undiagnosed conditions undergo to identify a diagnosis. Throughout this process, families of children with undiagnosed conditions have multiple opportunities to decide whether to continue or stop their search for a diagnosis and accept the lack of a diagnostic label. Previous studies identified factors motivating a family to begin searching, but there is limited information about the decision-making process in a prolonged search and how the affected child impacts a family's decision. This study aimed to understand how families of children with undiagnosed diseases decide whether to continue to pursue a diagnosis after standard clinical testing has failed. Parents who applied to the Undiagnosed Disease Network (UDN) at the National Institutes of Health (NIH) were recruited to participate in semi-structured interviews. The 2015 Supportive Care Needs model by Pelenstov, which defines critical needs in families with rare/undiagnosed diseases, provided a framework for interview guide development and transcript analysis (Pelentsov et al in Disabil Health J 8(4):475-491, 2015. https://doi.org/10.1016/J.DHJO.2015.03.009 ). A deductive, iterative coding approach was used to identify common unifying themes. Fourteen parents from 13 families were interviewed. The average child's age was 11 years (range 3-18) and an average 63% of their life had been spent searching for a diagnosis. Our analysis found that alignment or misalignment of parent and child needs impact the trajectory of the diagnostic search. When needs and desires align, reevaluation of a decision to pursue a diagnosis is limited. However, when there is conflict between parent and child desires, there is reevaluation, and often a pause, in the search. This tension is exacerbated when children are adolescents and attempting to balance their dependence on parents for medical care with a natural desire for independence. Our results provide novel insights into the roles of adolescents in the diagnostic odyssey. The tension between desired and realistic developmental outcomes for parents and adolescents impacts if, and how, the search for a diagnosis progresses.

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.

A second cohort of CHD3 patients expands the molecular mechanisms known to cause Snijders Blok-Campeau syndrome

There has been one previous report of a cohort of patients with variants in Chromodomain Helicase DNA-binding 3 (CHD3), now recognized as Snijders Blok-Campeau syndrome. However, with only three previously-reported patients with variants outside the ATPase/helicase domain, it was unclear if variants outside of this domain caused a clinically similar phenotype. We have analyzed 24 new patients with CHD3 variants, including nine outside the ATPase/helicase domain. All patients were detected with unbiased molecular genetic methods. There is not a significant difference in the clinical or facial features of patients with variants in or outside this domain. These additional patients further expand the clinical and molecular data associated with CHD3 variants. Importantly we conclude that there is not a significant difference in the phenotypic features of patients with various molecular disruptions, including whole gene deletions and duplications, and missense variants outside the ATPase/helicase domain. This data will aid both clinical geneticists and molecular geneticists in the diagnosis of this emerging syndrome.

De novo EIF2AK1 and EIF2AK2 Variants Are Associated with Developmental Delay, Leukoencephalopathy, and Neurologic Decompensation

EIF2AK1 and EIF2AK2 encode members of the eukaryotic translation initiation factor 2 alpha kinase (EIF2AK) family that inhibits protein synthesis in response to physiologic stress conditions. EIF2AK2 is also involved in innate immune response and the regulation of signal transduction, apoptosis, cell proliferation, and differentiation. Despite these findings, human disorders associated with deleterious variants in EIF2AK1 and EIF2AK2 have not been reported. Here, we describe the identification of nine unrelated individuals with heterozygous de novo missense variants in EIF2AK1 (1/9) or EIF2AK2 (8/9). Features seen in these nine individuals include white matter alterations (9/9), developmental delay (9/9), impaired language (9/9), cognitive impairment (8/9), ataxia (6/9), dysarthria in probands with verbal ability (6/9), hypotonia (7/9), hypertonia (6/9), and involuntary movements (3/9). Individuals with EIF2AK2 variants also exhibit neurological regression in the setting of febrile illness or infection. We use mammalian cell lines and proband-derived fibroblasts to further confirm the pathogenicity of variants in these genes and found reduced kinase activity. EIF2AKs phosphorylate eukaryotic translation initiation factor 2 subunit 1 (EIF2S1, also known as EIF2α), which then inhibits EIF2B activity. Deleterious variants in genes encoding EIF2B proteins cause childhood ataxia with central nervous system hypomyelination/vanishing white matter (CACH/VWM), a leukodystrophy characterized by neurologic regression in the setting of febrile illness and other stressors. Our findings indicate that EIF2AK2 missense variants cause a neurodevelopmental syndrome that may share phenotypic and pathogenic mechanisms with CACH/VWM.

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.

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.

Health Supervision for Children With Neurofibromatosis Type 1

Neurofibromatosis type 1 (NF1) is a multisystem disorder that primarily involves the skin and peripheral nervous system. Its population prevalence is approximately 1 in 3000. The condition is usually recognized in early childhood, when pigmentary manifestations emerge. Although NF1 is associated with marked clinical variability, most children affected follow patterns of growth and development within the normal range. Some features of NF1 can be present at birth, but most manifestations emerge with age, necessitating periodic monitoring to address ongoing health and developmental needs and minimize the risk of serious medical complications. In this report, we provide a review of the clinical criteria needed to establish a diagnosis, the inheritance pattern of NF1, its major clinical and developmental manifestations, and guidelines for monitoring and providing intervention to maximize the health and quality of life of a child affected.

Expanding the Spectrum of BAF-Related Disorders: De Novo Variants in SMARCC2 Cause a Syndrome with Intellectual Disability and Developmental Delay

SMARCC2 (BAF170) is one of the invariable core subunits of the ATP-dependent chromatin remodeling BAF (BRG1-associated factor) complex and plays a crucial role in embryogenesis and corticogenesis. Pathogenic variants in genes encoding other components of the BAF complex have been associated with intellectual disability syndromes. Despite its significant biological role, variants in SMARCC2 have not been directly associated with human disease previously. Using whole-exome sequencing and a web-based gene-matching program, we identified 15 individuals with variable degrees of neurodevelopmental delay and growth retardation harboring one of 13 heterozygous variants in SMARCC2, most of them novel and proven de novo. The clinical presentation overlaps with intellectual disability syndromes associated with other BAF subunits, such as Coffin-Siris and Nicolaides-Baraitser syndromes and includes prominent speech impairment, hypotonia, feeding difficulties, behavioral abnormalities, and dysmorphic features such as hypertrichosis, thick eyebrows, thin upper lip vermilion, and upturned nose. Nine out of the fifteen individuals harbor variants in the highly conserved SMARCC2 DNA-interacting domains (SANT and SWIRM) and present with a more severe phenotype. Two of these individuals present cardiac abnormalities. Transcriptomic analysis of fibroblasts from affected individuals highlights a group of differentially expressed genes with possible roles in regulation of neuronal development and function, namely H19, SCRG1, RELN, and CACNB4. Our findings suggest a novel SMARCC2-related syndrome that overlaps with neurodevelopmental disorders associated with variants in BAF-complex subunits.

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.

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.

Prenatal and Postnatal Genetic Testing: Why, How, and When?

There have been major advances in genetic testing especially over the last 10 years. We have advanced from looking at simple chromosomes under a microscope to more sophisticated analysis of the DNA makeup of chromosomes and from testing a single gene to sequencing almost all of our genetic material. Similarly, in the field of prenatal testing we have made great strides in screening and diagnostic testing in the hope of detecting significant abnormalities in the fetus while decreasing the risk to the pregnancy. In this article the major types of genetic screening and diagnostic testing, both prenatal and postnatal, will be reviewed. [Pediatr Ann. 2017;46(11):e423-e427.].

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.

A Syndromic Neurodevelopmental Disorder Caused by De Novo Variants in EBF3

Early B cell factor 3 (EBF3) is a member of the highly evolutionarily conserved Collier/Olf/EBF (COE) family of transcription factors. Prior studies on invertebrate and vertebrate animals have shown that EBF3 homologs are essential for survival and that loss-of-function mutations are associated with a range of nervous system developmental defects, including perturbation of neuronal development and migration. Interestingly, aristaless-related homeobox (ARX), a homeobox-containing transcription factor critical for the regulation of nervous system development, transcriptionally represses EBF3 expression. However, human neurodevelopmental disorders related to EBF3 have not been reported. Here, we describe three individuals who are affected by global developmental delay, intellectual disability, and expressive speech disorder and carry de novo variants in EBF3. Associated features seen in these individuals include congenital hypotonia, structural CNS malformations, ataxia, and genitourinary abnormalities. The de novo variants affect a single conserved residue in a zinc finger motif crucial for DNA binding and are deleterious in a fly model. Our findings indicate that mutations in EBF3 cause a genetic neurodevelopmental syndrome and suggest that loss of EBF3 function might mediate a subset of neurologic phenotypes shared by ARX-related disorders, including intellectual disability, abnormal genitalia, and structural CNS malformations.

De Novo Truncating Variants in ASXL2 Are Associated with a Unique and Recognizable Clinical Phenotype

The ASXL genes (ASXL1, ASXL2, and ASXL3) participate in body patterning during embryogenesis and encode proteins involved in epigenetic regulation and assembly of transcription factors to specific genomic loci. Germline de novo truncating variants in ASXL1 and ASXL3 have been respectively implicated in causing Bohring-Opitz and Bainbridge-Ropers syndromes, which result in overlapping features of severe intellectual disability and dysmorphic features. ASXL2 has not yet been associated with a human Mendelian disorder. In this study, we performed whole-exome sequencing in six unrelated probands with developmental delay, macrocephaly, and dysmorphic features. All six had de novo truncating variants in ASXL2. A careful review enabled the recognition of a specific phenotype consisting of macrocephaly, prominent eyes, arched eyebrows, hypertelorism, a glabellar nevus flammeus, neonatal feeding difficulties, hypotonia, and developmental disabilities. Although overlapping features with Bohring-Opitz and Bainbridge-Ropers syndromes exist, features that distinguish the ASXL2-associated condition from ASXL1- and ASXL3-related disorders are macrocephaly, absence of growth retardation, and more variability in the degree of intellectual disabilities. We were also able to demonstrate with mRNA studies that these variants are likely to exert a dominant-negative effect, given that both alleles are expressed in blood and the mutated ASXL2 transcripts escape nonsense-mediated decay. In conclusion, de novo truncating variants in ASXL2 underlie a neurodevelopmental syndrome with a clinically recognizable phenotype. This report expands the germline disorders that are linked to the ASXL genes.

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.

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.

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.

Deletions in GRID2 lead to a recessive syndrome of cerebellar ataxia and tonic upgaze in humans

OBJECTIVE

To identify the genetic cause of a syndrome causing cerebellar ataxia and eye movement abnormalities.

METHODS

We identified 2 families with cerebellar ataxia, eye movement abnormalities, and global developmental delay. We performed genetic analyses including single nucleotide polymorphism genotyping, linkage analysis, array comparative genomic hybridization, quantitative PCR, and Sanger sequencing. We obtained eye movement recordings of mutant mice deficient for the ortholog of the identified candidate gene, and performed immunohistochemistry using human and mouse brain specimens.

RESULTS

All affected individuals had ataxia, eye movement abnormalities, most notably tonic upgaze, and delayed speech and cognitive development. Homozygosity mapping identified the disease locus on chromosome 4q. Within this region, a homozygous deletion of GRID2 exon 4 in the index family and compound heterozygous deletions involving GRID2 exon 2 in the second family were identified. Grid2-deficient mice showed larger spontaneous and random eye movements compared to wild-type mice. In developing mouse and human cerebella, GRID2 localized to the Purkinje cell dendritic spines. Brain MRI in 2 affected children showed progressive cerebellar atrophy, which was more severe than that of Grid2-deficient mice.

CONCLUSIONS

Biallelic deletions of GRID2 lead to a syndrome of cerebellar ataxia and tonic upgaze in humans. The phenotypic resemblance and similarity in protein expression pattern between humans and mice suggest a conserved role for GRID2 in the synapse organization between parallel fibers and Purkinje cells. However, the progressive and severe cerebellar atrophy seen in the affected individuals could indicate an evolutionarily unique role for GRID2 in the human cerebellum.

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 (CUP) 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 CUP 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 CUP or CP by sonography and/or MRI. Central nervous system imaging and careful neurodevelopmental follow-up is indicated in these infants.

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.

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.

Cytogenetic and array-CGH characterization of a complex de novo rearrangement involving duplication and deletion of 9p and clinical findings in a 4-month-old female

Approximately 15 patients with partial trisomy 9p involving de novo duplications have been previously described. Here, we present clinical, cytogenetic, FISH and aCGH findings in a patient with a de novo complex rearrangement in the short arm of chromosome 9 involving an inverted duplication at 9p24→p21.3 and a deletion at 9pter→p24.2. FISH probes generated from BACs selected from the UCSC genome browser were utilized to verify this rearrangement. It is likely that some previously described duplications of 9p may also be products of complex chromosomal aberrations. This report in which FISH and aCGH were used to more comprehensively characterize the genomic rearrangement in a patient with clinical manifestations of 9p duplication syndrome underscores the importance of further characterizing cytogenetically detected rearrangements.

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.

The frequency of palatal anomalies in Saethre-Chotzen syndrome

OBJECTIVE

Saethre-Chotzen Syndrome (SCS) is an autosomal dominant disorder with widespread phenotypic variability. Cardinal features include coronal synostosis, blepharoptosis, and limb abnormalities. Cleft palate can also occur, but there are few reports on its frequency. This study was undertaken to determine the prevalence of palatal anomalies in this population.

DESIGN

We retrospectively reviewed the records of 51 patients with SCS seen at Children's Hospital Boston over the past 30 years. Palatal findings in our patients were compared with those in the literature. To illustrate the phenotypic variability in SCS, we describe an unusual infant who presented for evaluation of cleft palate and blepharoptosis. Her father had only blepharoptosis; this was the clue to the diagnosis, which was confirmed by finding a deletion in the TWIST gene.

RESULTS

In our patients, high-arched palate was noted in 43%, bifid uvula in 10%, and cleft palate in 6%. These figures differed slightly from the combined percentages in published reports: 24% with high-arched palate, 2% with bifid uvula, and 5% with cleft palate.

CONCLUSIONS

Palatal anomalies are relatively common in SCS. This entity should be considered in the differential diagnosis of a child with cleft palate, particularly in the presence of blepharoptosis, nasal deviation, and limb abnormalities in the patient or in family members.

Molecular studies of segmental aneusomy: FISHing for the atypical cry in del(5)(p15.3)

We report a newborn male with multiple congenital anomalies including growth retardation, hypotonia, dysmorphic facies, widely-spaced nipples, micropenis, cryptorchidism, optic nerve hypoplasia, heart disease, and a striking, high-pitched cry. Chromosome analysis revealed de novo partial trisomy 11q due to a der(5)t(5;11)(p15.3;q22). Fluorescence in situ hybridization (FISH) showed loss of the 5p telomere signal on the der(5) chromosome, indicating the infant has partial monosomy 5p in addition to partial trisomy 11q. Among cases involving trisomy 11q, an unusual cry has only been documented in the presence of a der(5)t(5p;11q). This apparent dependence of the abnormal cry on monosomy 5p suggested the same genetic mechanism that occurs in Cri du chat syndrome (CDCS) may be responsible for the atypical cry in der(5)t(5p;11q) individuals. Neither a commercial CDCS probe (LSI D5S23, D5S721) nor a series of BAC clones encompassing distal regions implicated in the CDCS-associated cat-cry were deleted in our patient. These results suggest a second cry-modifying locus maps telomeric to BAC RP11-94J21 in band 5p15.33. This locus may not only cause the abnormal cry in individuals with a der(5)t(5p;11q) but could also contribute to the phenotypic variability and discordant mapping studies observed for CDCS.

Knowledge of and Attitudes about Alzheimer Disease Genetics: Report of a Pilot Survey and Two Focus Groups

OBJECTIVES

In preparation for the development of an educational intervention on Alzheimer disease (AD) genetics, we undertook a pilot survey of knowledge in this area and attitudes toward genetic testing for AD among individuals with a family history of AD.

METHODS

For the pilot study, we administered a 30-min questionnaire to 57 unaffected individuals from a genetic linkage study. For the focus groups, we interviewed two groups of subjects, ages 44-70 years, with a family history of AD, one of 10 Caucasians and the other of 6 African-Americans.

RESULTS

The pilot study showed that there was limited knowledge of genetics overall and AD genetics in particular, considerable concern about personal risk, and little knowledge of or interest in genetic testing for the disease. The focus groups reinforced and fleshed out these impressions and highlighted the importance of caregiving experience in the attitudes toward personal risk for AD.

CONCLUSIONS

These results underscore the value of genetics education for this and other complex diseases and suggest specific foci for educational interventions.

Bupropion in pregnancy and the prevalence of congenital malformations

PURPOSE

Reports from the GlaxoSmithKline Bupropion Pregnancy Registry suggested an increase in cardiovascular defects following exposure to bupropion during pregnancy. We conducted a study of congenital malformations among infants born to women exposed to bupropion during their first trimester.

METHODS

The study used data from UnitedHealthcare between January 1995 and September 2004. We calculated the prevalence of all congenital malformations and cardiovascular malformations associated with bupropion exposure in the estimated first trimester (1213 infants), compared with (1) other antidepressant exposure in the first trimester (4743 infants) and (2) bupropion exposure outside the first trimester (1049 infants). Malformation cases were confirmed through medical record abstraction. We calculated adjusted odds ratios (AORs) using the GEE form of logistic regression.

RESULTS

For all congenital malformations, the prevalence associated with bupropion first trimester was 23.1 per 1000 infants. The AORs were 0.95 (95%CI 0.62-1.45) and 1.00 (95%CI 0.57-1.73) in comparison to other antidepressants (prevalence 23.2 per 1000) and bupropion outside the first trimester (prevalence 21.9 per 1000), respectively. For cardiovascular malformations, the prevalence associated with bupropion first trimester was 10.7 per 1000 infants. The AORs were 0.97 (95%CI 0.52-1.80) and 1.07 (95%CI 0.48-2.40) in comparison to other antidepressants (prevalence 10.8 per 1000) and bupropion outside the first trimester (prevalence 9.5 per 1000), respectively.

CONCLUSIONS

Results do not support a hypothesis of a teratogenic effect of first trimester bupropion exposure. The prevalence of malformations associated with bupropion exposure in the first trimester was not increased relative to the comparison groups.

Patients with Ehlers Danlos syndrome and CRPS: a possible association?

Rare patients are left with chronic pain, vasodysregulation, and other symptoms that define complex regional pain syndrome (CRPS), after limb traumas. The predisposing factors are unknown. Genetic factors undoubtedly contribute, but have not yet been identified. We report four CRPS patients also diagnosed with the classical or hypermobility forms of Ehlers Danlos syndrome (EDS), inherited disorders of connective tissue. These patients had been diagnosed using standard diagnostic criteria for CRPS and for EDS. All had sustained joint injury; in three this had been surgically treated. The association of these two diagnoses leads us to hypothesize that EDS might contribute to the development of CRPS in one or more of the following ways: via stretch injury to nerves traversing hypermobile joints, increased fragility of nerve connective tissue, or nerve trauma from more frequent surgery. We review the clinical presentation of the different Ehlers Danlos syndromes and provide clinical criteria that can be used to screen CRPS patients for EDS for clinical or research purposes.

Molecular and clinical analyses of Greig cephalopolysyndactyly and Pallister-Hall syndromes: robust phenotype prediction from the type and position of GLI3 mutations

Mutations in the GLI3 zinc-finger transcription factor gene cause Greig cephalopolysyndactyly syndrome (GCPS) and Pallister-Hall syndrome (PHS), which are variable but distinct clinical entities. We hypothesized that GLI3 mutations that predict a truncated functional repressor protein cause PHS and that functional haploinsufficiency of GLI3 causes GCPS. To test these hypotheses, we screened patients with PHS and GCPS for GLI3 mutations. The patient group consisted of 135 individuals: 89 patients with GCPS and 46 patients with PHS. We detected 47 pathological mutations (among 60 probands); when these were combined with previously published mutations, two genotype-phenotype correlations were evident. First, GCPS was caused by many types of alterations, including translocations, large deletions, exonic deletions and duplications, small in-frame deletions, and missense, frameshift/nonsense, and splicing mutations. In contrast, PHS was caused only by frameshift/nonsense and splicing mutations. Second, among the frameshift/nonsense mutations, there was a clear genotype-phenotype correlation. Mutations in the first third of the gene (from open reading frame [ORF] nucleotides [nt] 1-1997) caused GCPS, and mutations in the second third of the gene (from ORF nt 1998-3481) caused primarily PHS. Surprisingly, there were 12 mutations in patients with GCPS in the 3' third of the gene (after ORF nt 3481), and no patients with PHS had mutations in this region. These results demonstrate a robust correlation of genotype and phenotype for GLI3 mutations and strongly support the hypothesis that these two allelic disorders have distinct modes of pathogenesis.

Successful long-term treatment of hepatic carnitine palmitoyltransferase I deficiency and a novel mutation

Individuals with carnitine palmitoyltransferase I (CPT-I) deficiency cannot metabolize long-chain fatty acids and can develop life-threatening hypoglycaemia. We present a boy with CPT-I deficiency maintained on a very low-fat diet with nighttime uncooked cornstarch feedings for 5(1/2) years with good success. He has had normal growth and no episodes of hypoglycaemia or adverse side-effects. We found that he was homozygous for a previously undescribed mutation, T314I, in the CPT1A protein.

Alcohol dehydrogenase 2 genotypes, maternal alcohol use, and infant outcome

OBJECTIVE

To determine whether different alleles of the ADH2 gene (ADH2-1, ADH2-2 and ADH2-3) with differing levels of enzymatic activity can alter the risk of fetal alcohol effects.

STUDY DESIGN

ADH2 genotypes were performed on 404 pregnant high-risk women and 139 infants as part of a larger study of alcohol use in pregnancy. Mothers were interviewed about alcohol use during pregnancy, and their infants were examined for alcohol-related features without knowledge of the exposure status.

RESULTS

The ADH2-1/3 genotype was more prevalent among black women (46%) than expected (33%); the rate among white women was low as expected (2%). More black women who reported high alcohol use during the pregnancy had the ADH2-1/3 genotype compared with those who reported no alcohol use (70% vs 44%). Sixty percent of the affected black infants had the ADH2-1/3 genotype compared with 29% of the unaffected infants (P <.045). The maternal genotype correlated with her chance of having an infant with alcohol-related physical features (odds ratio = 2.49). This association remained significant after accounting for confounders, such as smoking and maternal weight gain. Alcohol exposure was not significantly associated with infant outcome in black infants after accounting for genotype, smoking, and maternal weight gain, but this association could only be tested in 10 infants of mothers with high exposure.

CONCLUSION

Women with the ADH2-1/3 genotype may be at greater risk for having an affected infant, which may be the result of greater ingestion of alcohol.

Maternal antiepileptic drug use and effects on fetal development

Many pregnant women take antiepileptic medications, and concern has arisen about the risks this poses to the fetus. It has been debated whether the causative agent is the medication or the underlying maternal disorder. Review of the recent literature indicates that the effects seem to be from the medications themselves. The frequency of malformations is about two to three-fold above the background rate and is dose-related for some of the medications. There seem to be effects on birth weight, length, and head circumference caused by at least some of the medications. The risks are greater when more than one medication is used. Cognitive effects from the medications have been shown, although these effects are of lower magnitude than previously reported. More investigation needs to be done to determine the exact risks of each individual medication, especially the newer ones. Studies on underlying mechanisms indicate potential genetic susceptibility and altered developmental gene expression patterns.

Malformations reported in chorionic villus sampling exposed children: a review and analytic synthesis of the literature

PURPOSE

To determine whether the frequency of vascular disruption defects, other than limb defects, is increased in reports of chorionic villus sampling (CVS) exposed children compared with an unexposed population.

METHODS

Only studies that reported the total number of CVS-exposed pregnancies and details of pregnancy outcome, including all the malformations, were included. Twenty-five articles met these criteria.

RESULTS

The frequencies of gastroschisis, intestinal atresias, and clubfoot were significantly increased among the CVS-exposed infants as compared with the baseline unexposed population. The frequencies of other vascular disruption defects, including Poland sequence, amniotic band sequence, and cleft lip/cleft palate, were not increased.

CONCLUSION

CVS-exposed children have an increased frequency of intestinal atresia, gastroschisis, and clubfoot compared with the nonexposed population. The fact that an increased frequency of other defects attributed to vascular disruption was not found may be due to under-ascertainment, misclassification, or "lumping" of the defects identified in previous studies.

Under-recognition of prenatal alcohol effects in infants of known alcohol abusing women

Medical records of 124 women and their infants were analyzed for: (1) documentation of maternal alcohol and other substance abuse and (2) evaluation of exposed infants. These results were compared with the study interview and infant examination. More obstetric nurses documented the presence or absence of alcohol and substance abuse than did pediatricians. More women reported using alcohol in the study interview than documented in the medical records. There was slightly better documentation for cocaine use than for alcohol use in the medical records. One of the 19 infants with documentation of maternal alcohol use was noted to have possible alcohol-related features by the pediatrician, in contrast to 7 infants identified by the study examiner. In addition, 2 of these 19 infants were determined by the study examiner to have fetal alcohol syndrome; neither case was diagnosed by the pediatricians. Continued efforts at education regarding the importance of asking about prenatal alcohol exposure and the spectrum of fetal alcohol effects are needed for early diagnosis.