Severe CNS involvement in a subset of long-term treated children with infantile-onset Pompe disease

INTRODUCTION

The standard of care for patients with infantile-onset Pompe disease (IOPD) is enzyme replacement therapy (ERT), which does not cross the blood brain barrier. While neuromuscular manifestations of IOPD are well-described, central nervous system (CNS) manifestations of this disorder are far less characterized. Here we describe severe CNS-related neurological manifestations including seizures and encephalopathy in six individuals with IOPD.

METHOD

We identified six children with IOPD who developed CNS manifestations such as seizures and/or encephalopathy. We studied their brain magnetic resonance imaging scans (MRIs) and graded the severity of white matter hyperintensities (WMHI) using the Fazekas scale scoring system as previously published. Longitudinal cognitive measures were available from 4/6 children.

RESULTS

All six IOPD patients (4 males/2 females) had been treated with ERT for 12-15 years. Seizures and/or encephalopathy were noted at a median age at onset of 11.9 years (range 9-15 years). All were noted to have extensive WMHI in the brain MRIs and very high Fazekas scores which preceded the onset of neurological symptoms. Longitudinal IQ scores from four of these children suggested developmental plateauing.

DISCUSSION

Among a subset of IOPD patients on long-term ERT, CNS manifestations including hyperreflexia, encephalopathy and seizures may become prominent, and there is likely an association between these symptoms and significant WMHI on MRI. Further study is needed to identify risk factors for CNS deterioration among children with IOPD and develop interventions to prevent neurological decline.

A homozygous MED11 C-terminal variant causes a lethal neurodegenerative disease

PURPOSE

The mediator (MED) multisubunit-complex modulates the activity of the transcriptional machinery, and genetic defects in different MED subunits (17, 20, 27) have been implicated in neurologic diseases. In this study, we identified a recurrent homozygous variant in MED11 (c.325C>T; p.Arg109Ter) in 7 affected individuals from 5 unrelated families.

METHODS

To investigate the genetic cause of the disease, exome or genome sequencing were performed in 5 unrelated families identified via different research networks and Matchmaker Exchange. Deep clinical and brain imaging evaluations were performed by clinical pediatric neurologists and neuroradiologists. The functional effect of the candidate variant on both MED11 RNA and protein was assessed using reverse transcriptase polymerase chain reaction and western blotting using fibroblast cell lines derived from 1 affected individual and controls and through computational approaches. Knockouts in zebrafish were generated using clustered regularly interspaced short palindromic repeats/Cas9.

RESULTS

The disease was characterized by microcephaly, profound neurodevelopmental impairment, exaggerated startle response, myoclonic seizures, progressive widespread neurodegeneration, and premature death. Functional studies on patient-derived fibroblasts did not show a loss of protein function but rather disruption of the C-terminal of MED11, likely impairing binding to other MED subunits. A zebrafish knockout model recapitulates key clinical phenotypes.

CONCLUSION

Loss of the C-terminal of MED subunit 11 may affect its binding efficiency to other MED subunits, thus implicating the MED-complex stability in brain development and neurodegeneration.

Combined SPINK1 mutations induce early-onset severe chronic pancreatitis in a child with severe obesity

Summary

The most frequent causes of pancreatitis classically have been known to be gallstones or alcohol. However, genetics can also play a key role in predisposing patients to both chronic and acute pancreatitis. The serine protease inhibitor Kazal type 1 (SPINK 1) gene is known to be strongly associated with pancreatitis. Patients with these underlying genetic mutations can have severe diseases with a high morbidity rate and frequent hospitalization. We report an Arab girl who presented with acute pancreatitis at the age of 7 years progressing to recurrent chronic pancreatitis over a few years. She had severe obesity from the age of 4 years and developed type 2 diabetes at the age of 12. She had a normal biliary system anatomy. Genetic analysis showed that she had combined heterozygous mutations in the SPINK1 gene (SPINK1, c.101A>G p.(Asn34Ser) and SPINK1, c.56-37T>C). Her parents were first-degree cousins, but neither had obesity. Mother was detected to have the same mutations. She had type 2 diabetes but never presented with pancreatitis. This case is the first to be reported from the Arab region with these combined mutations leading to recurrent chronic pancreatitis. It illustrates the importance of diagnosing the underlying genetic mutation in the absence of other known causes of pancreatitis. Considering the absence of pancreatitis history in the mother who did not have obesity but harboured the same mutations, we point out that severe obesity might be a triggering factor of pancreatitis in the presence of the mutations in SPINK1 gene in this child. While this is not an assumption from a single patient, we show that not all carriers of this mutation develop the disease even within the same family. Triggering factors like severe obesity might have a role in developing the disease.

Learning points

Acute recurrent pancreatitis and chronic pancreatitis are uncommon in children but might be underdiagnosed. Biliary tract anomalies and dyslipidaemias are known causative factors for pancreatitis, but pancreatitis can be seen in children with intact biliary system. Genetic diagnosis should be sought in children with pancreatitis in the absence of known underlying predisposing factors. SPINK1 mutations can predispose to an early-onset severe recurrent pancreatitis and acute pancreatitis.

PDZD8 Disruption Causes Cognitive Impairment in Humans, Mice, and Fruit Flies

BACKGROUND

The discovery of coding variants in genes that confer risk of intellectual disability (ID) is an important step toward understanding the pathophysiology of this common developmental disability.

METHODS

Homozygosity mapping, whole-exome sequencing, and cosegregation analyses were used to identify gene variants responsible for syndromic ID with autistic features in two independent consanguineous families from the Arabian Peninsula. For in vivo functional studies of the implicated gene's function in cognition, Drosophila melanogaster and mice with targeted interference of the orthologous gene were used. Behavioral, electrophysiological, and structural magnetic resonance imaging analyses were conducted for phenotypic testing.

RESULTS

Homozygous premature termination codons in PDZD8, encoding an endoplasmic reticulum-anchored lipid transfer protein, showed cosegregation with syndromic ID in both families. Drosophila melanogaster with knockdown of the PDZD8 ortholog exhibited impaired long-term courtship-based memory. Mice homozygous for a premature termination codon in Pdzd8 exhibited brain structural, hippocampal spatial memory, and synaptic plasticity deficits.

CONCLUSIONS

These data demonstrate the involvement of homozygous loss-of-function mutations in PDZD8 in a neurodevelopmental cognitive disorder. Model organisms with manipulation of the orthologous gene replicate aspects of the human phenotype and suggest plausible pathophysiological mechanisms centered on disrupted brain development and synaptic function. These findings are thus consistent with accruing evidence that synaptic defects are a common denominator of ID and other neurodevelopmental conditions.

Clinical, Biochemical, and Genetic Heterogeneity in Glutaric Aciduria Type II Patients

The variants of electron transfer flavoprotein (ETFA, ETFB) and ETF dehydrogenase (ETFDH) are the leading cause of glutaric aciduria type II (GA-II). In this study, we identified 13 patients harboring six variants of two genes associated with GA-II. Out of the six variants, four were missense, and two were frameshift mutations. A missense variant (ETFDH:p.Gln269His) was observed in a homozygous state in nine patients. Among nine patients, three had experienced metabolic crises with recurrent vomiting, abdominal pain, and nausea. In one patient with persistent metabolic acidosis, hypoglycemia, and a high anion gap, the ETFDH:p.Gly472Arg, and ETFB:p.Pro94Thrfs*8 variants were identified in a homozygous, and heterozygous state, respectively. A missense variant ETFDH:p.Ser442Leu was detected in a homozygous state in one patient with metabolic acidosis, hypoglycemia, hyperammonemia and liver dysfunction. The ETFDH:p.Arg41Leu, and ETFB:p.Ile346Phefs*19 variants were observed in a homozygous state in one patient each. Both these variants have not been reported so far. In silico approaches were used to evaluate the pathogenicity and structural changes linked with these six variants. Overall, the results indicate the importance of a newborn screening program and genetic investigations for patients with GA-II. Moreover, careful interpretation and correlation of variants of uncertain significance with clinical and biochemical findings are needed to confirm the pathogenicity of such variants.

Spectrum of neuro-genetic disorders in the United Arab Emirates national population

Clinical and molecular characterization of neuro-genetic disorders among UAE national patients seen in the Genetic Clinic at Tawam hospital over a period of 3 years. A retrospective chart review of all Emirati patients assessed by clinical geneticists due to neuro-genetic disorders including global developmental delay, ASD, ID, ADHD, and epilepsy in combination with abnormalities of other organ systems. Each patient had proper assessment including detailed history, three-generation family history, developmental history and detailed physical examination looking for other system involvement. Hearing test and ophthalmological examination were performed when needed. Magnetic resonance imaging (MRI) of the brain, echocardiogram, and renal ultrasound were pursued as indicated. Detailed psychological evaluation and psychometric assessment were done when indicated. The review was done for a period between January 2018 and December 2020. Genetic investigations included chromosome karyotype, FISH study, metabolic/biochemical tests, chromosome microarray, gene sequencing, targeted mutation testing, trio whole exome and trio genome sequencing. A total of 644 patients with developmental delay, ID, learning difficulty, ASD, ADHD, or NNDs, were seen in genetic clinic from January 2018 to December 2020. A total of 506 patients were included in this review, all completed the genetic evaluations during the study period. There were 398 (61.8%) males and 246 (38.2%) females, with a ratio of 1.6:1. Positive family history of NDD was documented in 132 families, while 115 families had negative history and family history was unknown/unclear in the remaining. Fifty seven (11.26% [57/506]) patients had positive microarray results. Hundred ninety seven (38.9% [197/506]) patients had positive molecular testing. Genetic disorders were found in 133 (67.5% [133/197]) and inborn errors of metabolism were found in 42 (21.3% [42/197]). Consanguinity was documented in 139 patients with positive molecular diagnoses (139/197, 70.5%). Sixty nine (35% [69/197]) patients had autosomal dominant disorders, majority were De Novo (84%). Ninety-five (48% [95/197]) patients had autosomal recessive diseases, 40 mutations involved inborn errors of metabolism and 50 mutations involved genetic disorders. Pathogenic variants causing both autosomal dominant and recessive disorders were found in 98 patients (49.7% [98/197]), likely pathogenic variants causing both autosomal dominant and recessive disorders were found in 66 patients (33.5% [66/197]). X-linked related disorders were found in 10 patients (5% [10/197]). Mitochondrial mutation was found in one patient. Novel mutations were found in 76 patients (76/197 i.e., 38.56%). Twenty two patients had variants of unknown significant. The remaining 252 studied patients (252/506 i.e., 49.8%), remained undiagnosed. This study shows that neuro-genetic disorders in the UAE are very heterogeneous at clinical and molecular levels. Using microarray, WES and WGS a diagnosis was reached in 50% of the patients while no diagnosis was reached in other half of the studied patients. It is possible that some mutations were missed by WGS and WES. However, it is also possible that many of disorders in UAE population are novel and the causative mutation is not yet discovered. More researches need to be done in this population to uncover the molecular basis of these disorders.

Hereditary orotic aciduria (HOA): A novel uridine-5-monophosphate synthase (UMPS) mutation

Hereditary orotic aciduria (HOA) is a very rare inborn error of pyrimidine metabolism. It results from a defect of the uridine-5-monophosphate synthase (UMPS) gene. To date, only about twenty patients have been described. We report a case of HOA with a novel variant in the UMPS gene. A 17-year-old Emirati girl was born to first-cousin parents. During the first year, she had recurrent, severe infections including disseminated varicella. After evaluation for immunodeficiency, an impression of immunodeficiency of unknown etiology was presumed. Frequent episodes of pancytopenia were also noted. Bone marrow biopsy showed trilineage megaloblastoid maturation with dysplastic changes that were refractory to hematinic therapy. Also, she was noted to have failure to thrive, developmental delay and epilepsy. She was referred to the Genetics clinic where whole-exome sequencing (WES) was done and showed a novel homozygous variant in the UMPS gene confirming a diagnosis of HOA. She was started on uridine triacetate after which she showed clinical, hematologic and biochemical improvement. Although extremely rare, hereditary orotic aciduria should be suspected in any child with megaloblastic bone marrow, immunodeficiency or when developmental delay and anemia coexist.

A novel missense heterozygous mutation in MAP3K1 gene causes 46, XY disorder of sex development: case report and literature review

Background

Disorders of sex development (DSD) can result from congenital defect in sex determining pathway. Mitogen‐activated protein kinase kinase kinase 1 (MAP3K1) is one of the commonest genes that has been identified to cause 46, XY DSD. It can present as complete or partial gonadal dysgenesis even within the same kindred. Few mutations in this gene have previously been identified in a high proportion of individuals with 46, XY gonadal dysgenesis.

Methods and Results

We report three siblings with same novel variant in MAP3K1 gene presenting with variable degrees of partial gonadal dysgenesis. Clinical and genetic assessments were performed for the three siblings, while endocrine evaluation was done for two of them. The identified mutation (p.Thr657Arg) was previously classified as a pathogenic variant, although apparently there are no reported humans with this mutation.

Conclusion

This report adds to the genotype‐phenotype correlation, highlighting the clinical importance of considering MAP3K1 gene defects as part of the differential diagnosis for complete or partial gonadal dysgenesis especially with multiple affected family members.

We describe in detail the clinical phenotypes of three affected siblings, with same novel variant in MAP3K1 gene presenting with variable degrees of partial gonadal dysgenesis. In this report, we declare the identification of a new disease causing missense variant in MAP3K1 gene which was not apparently described in humans before. Our report adds to the genotype‐phenotype correlation, highlighting the clinical importance of considering MAP3K1 gene defects as part of the differential diagnosis for complete or partial gonadal dysgenesis especially with multiple affected family members.

De novo and inherited TCF20 pathogenic variants are associated with intellectual disability, dysmorphic features, hypotonia, and neurological impairments with similarities to Smith-Magenis syndrome

BACKGROUND

Neurodevelopmental disorders are genetically and phenotypically heterogeneous encompassing developmental delay (DD), intellectual disability (ID), autism spectrum disorders (ASDs), structural brain abnormalities, and neurological manifestations with variants in a large number of genes (hundreds) associated. To date, a few de novo mutations potentially disrupting TCF20 function in patients with ID, ASD, and hypotonia have been reported. TCF20 encodes a transcriptional co-regulator structurally related to RAI1, the dosage-sensitive gene responsible for Smith-Magenis syndrome (deletion/haploinsufficiency) and Potocki-Lupski syndrome (duplication/triplosensitivity).

METHODS

Genome-wide analyses by exome sequencing (ES) and chromosomal microarray analysis (CMA) identified individuals with heterozygous, likely damaging, loss-of-function alleles in TCF20. We implemented further molecular and clinical analyses to determine the inheritance of the pathogenic variant alleles and studied the spectrum of phenotypes.

RESULTS

We report 25 unique inactivating single nucleotide variants/indels (1 missense, 1 canonical splice-site variant, 18 frameshift, and 5 nonsense) and 4 deletions of TCF20. The pathogenic variants were detected in 32 patients and 4 affected parents from 31 unrelated families. Among cases with available parental samples, the variants were de novo in 20 instances and inherited from 4 symptomatic parents in 5, including in one set of monozygotic twins. Two pathogenic loss-of-function variants were recurrent in unrelated families. Patients presented with a phenotype characterized by developmental delay, intellectual disability, hypotonia, variable dysmorphic features, movement disorders, and sleep disturbances.

CONCLUSIONS

TCF20 pathogenic variants are associated with a novel syndrome manifesting clinical characteristics similar to those observed in Smith-Magenis syndrome. Together with previously described cases, the clinical entity of TCF20-associated neurodevelopmental disorders (TAND) emerges from a genotype-driven perspective.

Dysfunction of the Cerebral Glucose Transporter SLC45A1 in Individuals with Intellectual Disability and Epilepsy

Glucose transport across the blood brain barrier and into neural cells is critical for normal cerebral physiologic function. Dysfunction of the cerebral glucose transporter GLUT1 (encoded by SLC2A1) is known to result in epilepsy, intellectual disability (ID), and movement disorder. Using whole-exome sequencing, we identified rare homozygous missense variants (c.526C>T [p.Arg176Trp] and c.629C>T [p.Ala210Val]) in SLC45A1, encoding another cerebral glucose transporter, in two consanguineous multiplex families with moderate to severe ID, epilepsy, and variable neuropsychiatric features. The variants segregate with the phenotype in these families, affect well-conserved amino acids, and are predicted to be damaging by in silico programs. Intracellular glucose transport activity of the p.Arg176Trp and p.Ala210Val SLC45A1 variants, measured in transfected COS-7 cells, was approximately 50% (p = 0.013) and 33% (p = 0.008) lower, respectively, than that of intact SLC45A1. These results indicate that residues at positions 176 and 210 are critical for the glucose transport activity of SLC45A1. All together, our data strongly suggest that recessive mutations in SLC45A1 cause ID and epilepsy. SLC45A1 thus represents the second cerebral glucose transporter, in addition to GLUT1, to be involved in neurodevelopmental disability. Identification of additional individuals with mutations in SLC45A1 will allow better definition of the associated phenotypic spectrum and the exploration of potential targeted treatment options.

Homozygous variants in pyrroline-5-carboxylate reductase 2 (PYCR2) in patients with progressive microcephaly and hypomyelinating leukodystrophy

Pyrroline-5-carboxylate reductase 2, encoded by PYCR2, is one of the three homologous enzymes that catalyze the last step of proline synthesis. Homozygous variants in PYCR2 have been reported in patients from multiple consanguineous families with hypomyelinating leukodystrophy 10 (HLD10) (MIM: 616420). Here, we report five additional patients from three families with homozygous nonsense or missense variants in PYCR2, identified through clinical exome sequencing. All patients presented with postnatally acquired microcephaly, moderate to profound global developmental delay, and failure to thrive. Brain MRI in these patients showed thin corpus callosum, delayed myelination, and generalized white-matter volume loss. Additional phenotypes that were less consistent among patients included seizures or seizure-like movements, spasticity and ataxic gait, recurrent vomiting, cortical blindness, dysmorphic features, joint contractures, and irritability. Exome sequencing identified homozygous variants in PYCR2 in the proband from each family: c.28C>T (p.(Glu10Ter)), c.796C>T (p.(Arg266Ter)), and c.577G>A (p.(Val193Met)). Subsequent targeted analyses demonstrated co-segregation of the disease with the variant in the family. Despite the metabolic role of PYCR2, routine serum metabolic test in these patients were normal. To further understand the disease etiology and functions of PYCR2, small molecule metabolomics profiling was performed in plasma from three severely affected patients. No significant changes were identified in proline biosynthesis pathway or related metabolites. Studying the clinical features and the metabolic profiles of the PYCR2-deficient patients provides a more comprehensive picture for this newly identified disorder and facilitates further research on the gene function and disease etiology. © 2016 Wiley Periodicals, Inc.

MIPEP recessive variants cause a syndrome of left ventricular non-compaction, hypotonia, and infantile death

BACKGROUND

Mitochondrial presequence proteases perform fundamental functions as they process about 70 % of all mitochondrial preproteins that are encoded in the nucleus and imported posttranslationally. The mitochondrial intermediate presequence protease MIP/Oct1, which carries out precursor processing, has not yet been established to have a role in human disease.

METHODS

Whole exome sequencing was performed on four unrelated probands with left ventricular non-compaction (LVNC), developmental delay (DD), seizures, and severe hypotonia. Proposed pathogenic variants were confirmed by Sanger sequencing or array comparative genomic hybridization. Functional analysis of the identified MIP variants was performed using the model organism Saccharomyces cerevisiae as the protein and its functions are highly conserved from yeast to human.

RESULTS

Biallelic single nucleotide variants (SNVs) or copy number variants (CNVs) in MIPEP, which encodes MIP, were present in all four probands, three of whom had infantile/childhood death. Two patients had compound heterozygous SNVs (p.L582R/p.L71Q and p.E602*/p.L306F) and one patient from a consanguineous family had a homozygous SNV (p.K343E). The fourth patient, identified through the GeneMatcher tool, a part of the Matchmaker Exchange Project, was found to have inherited a paternal SNV (p.H512D) and a maternal CNV (1.4-Mb deletion of 13q12.12) that includes MIPEP. All amino acids affected in the patients' missense variants are highly conserved from yeast to human and therefore S. cerevisiae was employed for functional analysis (for p.L71Q, p.L306F, and p.K343E). The mutations p.L339F (human p.L306F) and p.K376E (human p.K343E) resulted in a severe decrease of Oct1 protease activity and accumulation of non-processed Oct1 substrates and consequently impaired viability under respiratory growth conditions. The p.L83Q (human p.L71Q) failed to localize to the mitochondria.

CONCLUSIONS

Our findings reveal for the first time the role of the mitochondrial intermediate peptidase in human disease. Loss of MIP function results in a syndrome which consists of LVNC, DD, seizures, hypotonia, and cataracts. Our approach highlights the power of data exchange and the importance of an interrelationship between clinical and research efforts for disease gene discovery.

A new aneurysm wrapping material: polyglactin 910 + fibrin sealant

Aneurysms experimentally induced by using the silver nitrate coagulation method in 10 Wistar Albino rats are wrapped with Polyglactin 910 and Fibrin Sealant. 6 weeks later the rats are sacrificed and compared with the control group. In the group in which Polyglactin 910 and Fibrin Sealant were used as the wrapping material, non-specific inflammatory granulation tissue development around the aneurysms is observed. We suggest that a Polyglactin 910 and Fibrin Sealant combination can be used as a wrapping material in the treatment of aneurysms where clipping is not possible.