Biallelic variants in SLC4A10 encoding a sodium-dependent bicarbonate transporter lead to a neurodevelopmental disorder.

PURPOSE: SLC4A10 encodes a plasma membrane-bound transporter, which mediates Na+-dependent HCO3- import, thus mediating net acid extrusion. Slc4a10 knockout mice show collapsed brain ventricles, an increased seizure threshold, mild behavioral abnormalities, impaired vision, and deafness. METHODS: Utilizing exome/genome sequencing in families with undiagnosed neurodevelopmental disorders and international data sharing, 11 patients from 6 independent families with biallelic variants in SLC4A10 were identified. Clinico-radiological and dysmorphology assessments were conducted. A minigene assay, localization studies, intracellular pH recordings, and protein modeling were performed to study the possible functional consequences of the variant alleles. RESULTS: The families harbor 8 segregating ultra-rare biallelic SLC4A10 variants (7 missense and 1 splicing). Phenotypically, patients present with global developmental delay/intellectual disability and central hypotonia, accompanied by variable speech delay, microcephaly, cerebellar ataxia, facial dysmorphism, and infrequently, epilepsy. Neuroimaging features range from some non-specific to distinct neuroradiological findings, including slit ventricles and a peculiar form of bilateral curvilinear nodular heterotopia. In silico analyses showed 6 of 7 missense variants affect evolutionarily conserved residues. Functional analyses supported the pathogenicity of 4 of 7 missense variants. CONCLUSION: We provide evidence that pathogenic biallelic SLC4A10 variants can lead to neurodevelopmental disorders characterized by variable abnormalities of the central nervous system, including altered brain ventricles, thus resembling several features observed in knockout mice.

Functional insight into a neurodevelopmental disorder caused by missense variants in an RNA-binding protein, RBM10.

The RNA-binding motif protein 10, RBM10, is an RNA splicing regulator essential for development. Loss-of-function RBM10 variants are associated with TARP syndrome, a severe X-linked recessive condition in males. We report a 3-year-old male with a mild phenotype, consisting of cleft palate, hypotonia, developmental delay, and minor dysmorphisms, associated with a missense RBM10 variant, c.943T>C, p.Ser315Pro, affecting the RRM2 RNA-binding domain. His clinical features were similar to a previously reported case associated with a missense variant. The p.Ser315Pro mutant protein was expressed normally in the nucleus, but its expression level and protein stability were slightly reduced. Nuclear magnetic resonance spectroscopy showed that the structure and the RNA-binding ability of the RRM2 domain with the p.Ser315Pro were unaffected. However, it affects the alternative splicing regulations of downstream genes, NUMB and TNRC6A, and its splicing alteration patterns were variable depending on target transcripts. In summary, a novel germline missense RBM10 p.Ser315Pro variant that causes functional changes in the expression of its downstream genes results in a non-lethal phenotype associated with developmental delays. The functional alteration effects depend on the residues affected by missense variants. Our findings are expected to bring broader insights into the RBM10-associated genotype-phenotype relationships by delineating the molecular mechanism of RBM10 functions.

Consolidation of the clinical and genetic definition of a SOX4-related neurodevelopmental syndrome.

BACKGROUND: A neurodevelopmental syndrome was recently reported in four patients with SOX4 heterozygous missense variants in the high-mobility-group (HMG) DNA-binding domain. The present study aimed to consolidate clinical and genetic knowledge of this syndrome. METHODS: We newly identified 17 patients with SOX4 variants, predicted variant pathogenicity using in silico tests and in vitro functional assays and analysed the patients' phenotypes. RESULTS: All variants were novel, distinct and heterozygous. Seven HMG-domain missense and five stop-gain variants were classified as pathogenic or likely pathogenic variant (L/PV) as they precluded SOX4 transcriptional activity in vitro. Five HMG-domain and non-HMG-domain missense variants were classified as of uncertain significance (VUS) due to negative results from functional tests. When known, inheritance was de novo or from a mosaic unaffected or non-mosaic affected parent for patients with L/PV, and from a non-mosaic asymptomatic or affected parent for patients with VUS. All patients had neurodevelopmental, neurological and dysmorphic features, and at least one cardiovascular, ophthalmological, musculoskeletal or other somatic anomaly. Patients with L/PV were overall more affected than patients with VUS. They resembled patients with other neurodevelopmental diseases, including the SOX11-related and Coffin-Siris (CSS) syndromes, but lacked the most specific features of CSS. CONCLUSION: These findings consolidate evidence of a fairly non-specific neurodevelopmental syndrome due to SOX4 haploinsufficiency in neurogenesis and multiple other developmental processes.

Delineating the genotypic and phenotypic spectrum of HECW2-related neurodevelopmental disorders.

BACKGROUND: Variants in HECW2 have recently been reported to cause a neurodevelopmental disorder with hypotonia, seizures and impaired language; however, only six variants have been reported and the clinical characteristics have only broadly been defined. METHODS: Molecular and clinical data were collected from clinical and research cohorts. Massive parallel sequencing was performed and identified individuals with a HECW2-related neurodevelopmental disorder. RESULTS: We identified 13 novel missense variants in HECW2 in 22 unpublished cases, of which 18 were confirmed to have a de novo variant. In addition, we reviewed the genotypes and phenotypes of previously reported and new cases with HECW2 variants (n=35 cases). All variants identified are missense, and the majority of likely pathogenic and pathogenic variants are located in or near the C-terminal HECT domain (88.2%). We identified several clustered variants and four recurrent variants (p.(Arg1191Gln);p.(Asn1199Lys);p.(Phe1327Ser);p.(Arg1330Trp)). Two variants, (p.(Arg1191Gln);p.(Arg1330Trp)), accounted for 22.9% and 20% of cases, respectively. Clinical characterisation suggests complete penetrance for hypotonia with or without spasticity (100%), developmental delay/intellectual disability (100%) and developmental language disorder (100%). Other common features are behavioural problems (88.9%), vision problems (83.9%), motor coordination/movement (75%) and gastrointestinal issues (70%). Seizures were present in 61.3% of individuals. Genotype-phenotype analysis shows that HECT domain variants are more frequently associated with cortical visual impairment and gastrointestinal issues. Seizures were only observed in individuals with variants in or near the HECT domain. CONCLUSION: We provide a comprehensive review and expansion of the genotypic and phenotypic spectrum of HECW2 disorders, aiding future molecular and clinical diagnosis and management.

A 3'-truncating FTL mutation associated with hypoferritinemia without neuroferritinopathy.

Mutations in the gene for the ferritin light chain (FTL) often present with hypoferritinemia associated with progressive, late onset extrapyramidal dysfunction. However, it has been suggested that some FTL mutations may impact ferritin levels without any neurological manifestations. We report on a FTL mutation in a three generation family with autosomal dominant hypoferritinemia without neurodegeneration. The 4 year old proband was identified with longstanding history of hypoferritinemia without evidence of anemia. Brain MRI did not show any evidence of iron deposition. It was found that the patient's 19 month old sister, 30 year old mother and 58 year old maternal grandmother also had hypoferritinemia and normal iron levels. Over the next nine years, none of these persons had any evidence of neurological dysfunction, including movement disorders, gait disturbances, behavioral or psychiatric dysfunction. Whole exome sequencing revealed a heterozygous interstitial deletion of at least 5 kb within cytogenic band 19q13.33 involving exons 3 and 4 of FTL in all affected family members. This 3' FTL deletion is predicted to create a significantly truncated protein product. We conclude that haploinsufficiency of FTL may be associated with hypoferritinemia without neurological dysfunction.

A Case of 45,X/46,XY Mosaicism Presenting as Swyer Syndrome.

BACKGROUND: Swyer syndrome is a difference of sex development that is typically associated with mutations in genes responsible for testicular development. It is speculated that some cases may result from cryptic 45,X/46,XY mosaicism leading to abnormal gonadal development. The presence or absence of a 45,X lineage is important for prognosis and management. CASE: We present a case of apparent Swyer syndrome associated with a 46,XY chromosomal complement in lymphocytes and 45,X/46,XY mosaicism on analysis of her noncancerous gonad. Gonadal histology was consistent with a 45,X phenotype. SUMMARY AND CONCLUSION: This case demonstrates the clinical variability in the presentation of 45,X/46,XY mosaicism and highlights the importance of thorough genetic testing that includes consideration of chromosomal mosaicism. We will discuss the implications of this diagnosis for management.

Recurrent De Novo NAHR Reciprocal Duplications in the ATAD3 Gene Cluster Cause a Neurogenetic Trait with Perturbed Cholesterol and Mitochondrial Metabolism.

Recent studies have identified both recessive and dominant forms of mitochondrial disease that result from ATAD3A variants. The recessive form includes subjects with biallelic deletions mediated by non-allelic homologous recombination. We report five unrelated neonates with a lethal metabolic disorder characterized by cardiomyopathy, corneal opacities, encephalopathy, hypotonia, and seizures in whom a monoallelic reciprocal duplication at the ATAD3 locus was identified. Analysis of the breakpoint junction fragment indicated that these 67 kb heterozygous duplications were likely mediated by non-allelic homologous recombination at regions of high sequence identity in ATAD3A exon 11 and ATAD3C exon 7. At the recombinant junction, the duplication allele produces a fusion gene derived from ATAD3A and ATAD3C, the protein product of which lacks key functional residues. Analysis of fibroblasts derived from two affected individuals shows that the fusion gene product is expressed and stable. These cells display perturbed cholesterol and mitochondrial DNA organization similar to that observed for individuals with severe ATAD3A deficiency. We hypothesize that the fusion protein acts through a dominant-negative mechanism to cause this fatal mitochondrial disorder. Our data delineate a molecular diagnosis for this disorder, extend the clinical spectrum associated with structural variation at the ATAD3 locus, and identify a third mutational mechanism for ATAD3 gene cluster variants. These results further affirm structural variant mutagenesis mechanisms in sporadic disease traits, emphasize the importance of copy number analysis in molecular genomic diagnosis, and highlight some of the challenges of detecting and interpreting clinically relevant rare gene rearrangements from next-generation sequencing data.

Psychiatric disease in an adolescent as a harbinger of cerebral X-linked adrenoleukodystrophy.

X-linked adrenoleukodystrophy (XALD) typically presents as a childhood cerebral demyelinating form, as an adult-onset adrenomyeloneuropathy or as adrenocortical insufficiency. Cerebral demyelination presenting in adolescence is unusual. We present an 17-year-old boy with adolescent-onset XALD initially manifesting with slowly progressive psychiatric symptoms. He was initially diagnosed with attention-deficit hyperactivity disorder and an acute psychosis. However, he was ultimately diagnosed with XALD based on his clinical course, neuroimaging findings and biochemical abnormalities. This case reiterates the atypical presentations of adolescent-onset cerebral XALD that may go unrecognised and misdiagnosed as a neurodevelopmental or psychiatric disease. Treatments for cerebral ALD are potentially life-saving, particularly when given early in the disease course.

A Case of Congenital Hypopituitarism Associated With a 1p31 Microdeletion: A Possible Role for LEPR and JAK1.

CONTEXT: Genetic defects affecting the expression and function of factors involved in pituitary development have been found to be associated with congenital hypopituitarism (CH). However, for most cases of CH, the etiology remains unknown. CASE DESCRIPTION: We present an unusual case of an infant with CH, associated with septo-optic dysplasia with an absent anterior pituitary and an ectopic posterior pituitary gland, resulting from a de novo 8.04-Mb interstitial deletion of chromosome 1p31.1-1p31.3. The deleted region includes several genes that might be involved in pituitary development, including LEPR and JAK1. CONCLUSIONS: Haploinsufficiency of LEPR and/or JAK1 might be associated with CH. This finding suggests a role for LEPR-mediated glycoprotein 130 signaling in human pituitary development.

Preterm Delivery as a Unique Pathophysiologic State Characterized by Maternal Soluble FMS-Like Tyrosine Kinase 1 and Uterine Artery Resistance During Pregnancy: A Longitudinal Cohort Study.

BACKGROUND: Preterm delivery (PTD) may be characterized by altered interrelationships among angiogenic factors and measures of placental function. We analyzed the longitudinal relationship between maternal serum concentrations of soluble fms-like tyrosine kinase 1 (sFlt1), an important antiangiogenic factor, and uterine artery resistance in pregnancies resulting in preterm and term deliveries. METHODS: Data were collected in a longitudinal cohort study involving 278 women monitored at 6 to 10, 10 to 14, 16 to 20, 22 to 26, and 32 to 36 weeks of gestation. Concentrations of maternal serum sFlt1 were determined using solid-phase enzyme-linked immunosorbent assay, and uterine artery resistance indices (RI) were measured by Doppler velocimetry at each interval. Preterm delivery was defined as birth before 37-weeks completed gestation. Data analyses used multivariable repeated measures regression models. RESULTS: Uterine artery RI decreased across gestation. As pregnancy progressed, RI trajectories diverged for term and preterm deliveries; the mean RI was significantly higher in third trimester for pregnancies resulting in PTD ( P = .08). sFlt1 was stable through 21 3/7 weeks of gestation and then increased rapidly; women who delivered preterm had significantly higher sFlt1 levels in the third trimester ( P = .04). The relationship between uterine artery RI and sFlt1 from the prior visit was significantly different between the groups ( P < .0001). For term deliveries, higher sFlt1 concentrations were associated with a smaller RI at the subsequent visit (ß = -.08, 95% confidence interval [CI]: -0.14 to -0.02). For PTD, higher sFlt1 concentrations were associated with a larger uterine artery RI (ß = .14, 95% CI: 0.06 to 0.22). CONCLUSION: PTD is characterized by altered relationships between angiogenic factors and placental vascular blood flow starting in early pregnancy.

A Novel Kleefstra Syndrome-associated Variant That Affects the Conserved TPLX Motif within the Ankyrin Repeat of EHMT1 Leads to Abnormal Protein Folding.

Kleefstra syndrome (KS) (Mendelian Inheritance in Man (MIM) no. 610253), also known as 9q34 deletion syndrome, is an autosomal dominant disorder caused by haploinsufficiency of euchromatic histone methyltransferase-1 (EHMT1). The clinical phenotype of KS includes moderate to severe intellectual disability with absent speech, hypotonia, brachycephaly, congenital heart defects, and dysmorphic facial features with hypertelorism, synophrys, macroglossia, protruding tongue, and prognathism. Only a few cases of de novo missense mutations in EHMT1 giving rise to KS have been described. However, some EHMT1 variants have been described in individuals presenting with autism spectrum disorder or mild intellectual disability, suggesting that the phenotypic spectrum resulting from EHMT1 alterations may be quite broad. In this report, we describe two unrelated patients with complex medical histories consistent with KS in whom next generation sequencing identified the same novel c.2426C>T (p.P809L) missense variant in EHMT1 To examine the functional significance of this novel variant, we performed molecular dynamics simulations of the wild type and p.P809L variant, which predicted that the latter would have a propensity to misfold, leading to abnormal histone mark binding. Recombinant EHMT1 p.P809L was also studied using far UV circular dichroism spectroscopy and intrinsic protein fluorescence. These functional studies confirmed the model-based hypotheses and provided evidence for protein misfolding and aberrant target recognition as the underlying pathogenic mechanism for this novel KS-associated variant. This is the first report to suggest that missense variants in EHMT1 that lead to protein misfolding and disrupted histone mark binding can lead to KS.

High Incidence of Noonan Syndrome Features Including Short Stature and Pulmonic Stenosis in Patients carrying NF1 Missense Mutations Affecting p.Arg1809: Genotype-Phenotype Correlation.

Neurofibromatosis type 1 (NF1) is one of the most frequent genetic disorders, affecting 1:3,000 worldwide. Identification of genotype-phenotype correlations is challenging because of the wide range clinical variability, the progressive nature of the disorder, and extreme diversity of the mutational spectrum. We report 136 individuals with a distinct phenotype carrying one of five different NF1 missense mutations affecting p.Arg1809. Patients presented with multiple café-au-lait macules (CALM) with or without freckling and Lisch nodules, but no externally visible plexiform neurofibromas or clear cutaneous neurofibromas were found. About 25% of the individuals had Noonan-like features. Pulmonic stenosis and short stature were significantly more prevalent compared with classic cohorts (P < 0.0001). Developmental delays and/or learning disabilities were reported in over 50% of patients. Melanocytes cultured from a CALM in a segmental NF1-patient showed two different somatic NF1 mutations, p.Arg1809Cys and a multi-exon deletion, providing genetic evidence that p.Arg1809Cys is a loss-of-function mutation in the melanocytes and causes a pigmentary phenotype. Constitutional missense mutations at p.Arg1809 affect 1.23% of unrelated NF1 probands in the UAB cohort, therefore this specific NF1 genotype-phenotype correlation will affect counseling and management of a significant number of patients.

Racial differences in IGF1 methylation and birth weight.

BACKGROUND: The birth weight of Black neonates in the United States is consistently smaller than that of their White counterparts. Epigenetic differences between the races may be involved in such disparities. The goal of these analyses was to model the role of IGF1 methylation in mediating the association between race and birth weight. Data was collected on a cohort of 87 live born infants. IGF1 methylation was measured in DNA isolated from the mononuclear fraction of umbilical cord blood collected after delivery. Quantitative, loci-specific methylation was assessed using the Infinium HumanMethylation27 BeadArray (Illumina Inc., San Diego, CA). Locus specific methylation of the IGF1 CpG site was validated on a subset of the original sample (N = 61) using pyrosequencing. Multiple linear regression was used to examine relationships between IGF1 methylation, race, and birth weight. A formal mediation analysis was then used to estimate the relationship of IGF1 methylation to race and birth weight. RESULTS: Black race was associated with a 7.45% decrease in gestational age-adjusted birth weight (aBW) (P = 0.04) and Black infants had significantly higher IGF1 methylation than non-Black infants (P < 0.05). A one standard deviation increase in IGF1 methylation was associated with a 3.32% decrease in aBW (P = 0.02). Including IGF1 methylation as a covariate, the effect of Black race on aBW was attenuated. A formal mediation analysis showed that the controlled direct effect of Black race on aBW was -6.26% (95% CI = -14.15, 1.06); the total effect of Black race on IGF1 methylation was -8.12% (95% CI = -16.08, -0.55); and the natural indirect effect of Black race on aBW through IGF1 methylation was -1.86% (95% CI = -5.22, 0.18). CONCLUSION: The results of the mediation analysis along with the multivariable regression analyses suggest that IGF1 methylation may partially mediate the relationship between Black race and aBW. Such epigenetic differences may be involved in racial disparities observed in perinatal outcomes.

Ornithine transcarbamylase deficiency presenting with acute reversible cortical blindness.

Acute focal neurologic deficits are a rare but known presentation of ornithine transcarbamylase deficiency, particularly in females. We describe here a 6-year-old girl with newly diagnosed ornithine transcarbamylase deficiency who presents with an episode of acute cortical blindness lasting for 72 hours in the absence of hyperammonemia. Her symptoms were associated with a subcortical low-intensity lesion with overlying cortical hyperintensity on fluid-attenuated inversion recovery magnetic resonance imaging (MRI) of the occipital lobes. Acute reversible vision loss with these MRI findings is an unusual finding in patients with ornithine transcarbamylase deficiency. Our findings suggest a role for oxidative stress and aberrant glutamine metabolism in the acute clinical features of ornithine transcarbamylase deficiency even in the absence of hyperammonemia.

Maternal serum leptin during pregnancy and infant birth weight: the influence of maternal overweight and obesity.

OBJECTIVE: Few studies have examined whether the distinct metabolic patterns found in obese and nonobese pregnant women have different effects on the growing fetus. Our objective was to estimate the influence of longitudinal variation in maternal serum leptin levels on variation in infant birth weight in overweight/obese versus normal-weight women. DESIGN AND METHODS: In a prospective cohort of 286 gravidas, maternal weight and serum leptin levels at 6-10, 10-14, 16-20, 22-26, and 32-36 weeks gestation were measured. Effects of leptin levels on infant birth weight adjusted for gestational age at delivery (aBW) were analyzed using a linear regression model that accounted for the relationship of time-varying predictors to the log-transformed leptin concentrations. RESULTS: Different relationships of aBW to maternal serum leptin and its rate of change across pregnancy were exhibited by overweight/obese and normal-weight gravidas. For normal-weight women, aBW is not associated with either the magnitude of the logarithm of the leptin concentration or with its rate of change in either the first or second half of pregnancy. Conversely, for overweight/obese women, an increase in the rate of change in maternal serum leptin in the second half of pregnancy is significantly associated with a decrease in aBW. This effect is distinct from that of maternal weight. CONCLUSION: Differences in the effect of maternal serum leptin on fetal growth between overweight/ obese and normal-weight women suggest metabolic and physiologic heterogeneity between these groups. Such differences may be involved in the long-term physiologic effects of the obese intrauterine environment on the health of the offspring.

Infantile hypertrophic cardiomyopathy associated with a novel MYL3 mutation.

Mutations in genes encoding cardiac sarcomeric proteins are thought to be a very rare cause of hypertrophic cardiomyopathy (HCM) in infants and young children. We report on genetic and histopathological findings in a 3-month-old infant presenting with severe progressive HCM arising from a mutation in the gene encoding the essential light chain of myosin (MYL3). The patient was found to have a novel, paternally inherited pathogenic c.530 A>G mutation in exon 5 of the MYL3 gene. His father was asymptomatic. Although, MYL3 mutations have been previously associated with adult-onset HCM, it has not been seen in infantile forms. As such, this case adds to the emerging evidence demonstrating that familial disease associated with mutations in cardiac sarcomere protein genes may have an important role in infants and children with HCM. In addition, this case highlights the marked phenotypic heterogeneity associated with sarcomeric protein mutations both within and between families.

The influence of overweight and obesity on maternal soluble fms-like tyrosine kinase 1 and its relationship with leptin during pregnancy.

We studied obesity-related differences in the relation of maternal levels of leptin to levels of soluble fms-like tyrosine kinase 1 (sFlt1), an antiangiogenic protein that influences placentation and risk of adverse pregnancy outcomes. In a prospective cohort of 286 gravidas, we measured maternal serum levels of sFlt1 and leptin at 5 time points across pregnancy. Analyses stratified on prepregnancy body mass index (<25 vs ≥25) were done using mixed linear models. The mean leptin concentrations were significantly higher in overweight/obese compared to normal-weight women, while mean sFlt1 levels in second and third trimester were significantly higher in normal weight compared to overweight/obese women. The relationship between sFlt1 and leptin differed between the 2 strata. After controlling for maternal weight, a 1 ng/mL increase in leptin was associated with an 19.4 pg/mL increase in sFlt1 (P = .01) in normal-weight women, while leptin was not associated with sFlt1 (ß = 1.1, P = .75) in overweight/obese women. Such differences suggest that metabolic differences in overweight/obese women compared to their normal weight peers may differentially impact the physiologic changes during pregnancy.