Early B-cell Factor 3-Related Genetic Disease Can Mimic Urofacial Syndrome

Urologic manifestations of hypotonia, ataxia, and delayed development syndrome (HADDS), a rare neurodevelopmental disorder

INTRODUCTION

Early B-cell factor 3 (EBF3) is a transcription factor involved in neuronal differentiation and maturation. Pathogenic variants are associated with hypotonia, ataxia, and delayed development syndrome (HADDS) (MIM#617330). Urologic manifestations are common and may have implications regarding long term renal function.

OBJECTIVE

To review all known patients with pathogenic variants of the EBF3 gene resulting in HADDS with urologic manifestations. We hypothesize a high rate of bladder dysfunction secondary to the EBF3 variant's impact on relaxation of the urinary sphincter leading to detrusor sphincter dyssynergia (DSD).

METHODS

The PubMed database was queried for publications of the EBF3 mutation between January 2017 and January 2023. Search terms were "EBF3 mutation OR HADDS AND urology OR phenotype". Retrospective analysis of HADDS patients cared for in our institution was performed. Demographic and clinical information was collected.

RESULTS

We identified 52 patients (33F:19M) through literature (28F:18M) and retrospective review (5F:1M). There was a high prevalence of genitourinary physical exam abnormalities, history of urinary tract infection, vesicoureteral reflux (VUR), and diagnosis of neurogenic bladder. Within the literature review cohort, 67% had a urologic diagnosis. Females were disproportionately affected with urologic manifestations. In our cohort, four of six children were diagnosed with VUR and severe voiding dysfunction consistent with neurogenic bladder (67%). These children were managed with a vesicostomy. Five children had bowel dysfunction requiring therapy. Urodynamics suggested a high prevalence of external sphincter dyssynergia. Less severe forms of DSD were felt to be implicated in the abnormal voiding parameters in children who presented later in life based on non-invasive flow studies.

DISCUSSION

There is significant variability in the phenotypic presentation of patients with HADDS. While EBF3 plays a clear role in neurodevelopment, it also impacts muscle development and may impact muscle relaxation. The location of the genetic variant may impact the degree of DSD, with more severe forms leading to earlier presentations. Initial work-up should include a renal ultrasound (RUS) and post void residual (PVR). Consideration can be given to obtaining a VCUG, DMSA scan or urodynamic studies. Yearly screening should be pursued with an RUS and PVR in those with an initial unremarkable work-up given the variable timing and severity of presentation.

CONCLUSION

Urologic manifestations of HADDS include high rates of bladder dysfunction secondary to DSD, vesicoureteral reflux, urinary tract infection, and cryptorchidism. These patients are at risk of renal deterioration if urinary abnormalities are not properly diagnosed and managed.

Further delineation of EBF3-related syndromic neurodevelopmental disorder in twelve Chinese patients

Neurodevelopmental disorders (NDDs) have heterogeneity in both clinical characteristics and genetic factors. EBF3 is a recently discovered gene associated with a syndromic form of NDDs characterized by hypotonia, ataxia and facial features. In this study, we report twelve unrelated individuals with EBF3 variants using next-generation sequencing. Five missense variants (four novel variants and one known variant) and seven copy number variations (CNVs) of EBF3 gene were identified. All of these patients exhibited developmental delay/intellectual disability. Ataxia was observed in 33% (6/9) of the patients, and abnormal muscle tone was observed in 55% (6/11) of the patients. Aberrant MRI reports were noted in 64% (7/11) of the patients. Four novel missense variants were all located in the DNA-binding domain. The pathogenicity of these variants was validated by in vitro experiments. We found that the subcellular protein localization of the R152C and F211L mutants was changed, and the distribution pattern of the R163G mutant was changed from even to granular. Luciferase assay results showed that the four EBF3 mutants' transcriptional activities were all significantly decreased (p < 0.01). Our study further expanded the gene mutation spectrum of EBF3-related NDD.

An Integrated Phenotypic and Genotypic Approach Reveals a High-Risk Subtype Association for EBF3 Missense Variants Affecting the Zinc Finger Domain

OBJECTIVE

Collier/Olf/EBF (COE) transcription factors have distinct expression patterns in the developing and mature nervous system. To date, a neurological disease association has been conclusively established for only the Early B-cell Factor-3 (EBF3) COE family member through the identification of heterozygous loss-of-function variants in individuals with autism spectrum/neurodevelopmental disorders (NDD). Here, we identify a symptom severity risk association with missense variants primarily disrupting the zinc finger domain (ZNF) in EBF3-related NDD.

METHODS

A phenotypic assessment of 41 individuals was combined with a literature meta-analysis for a total of 83 individuals diagnosed with EBF3-related NDD. Quantitative diagnostic phenotypic and symptom severity scales were developed to compare EBF3 variant type and location to identify genotype-phenotype correlations. To stratify the effects of EBF3 variants disrupting either the DNA-binding domain (DBD) or the ZNF, we used in vivo fruit fly UAS-GAL4 expression and in vitro luciferase assays.

RESULTS

We show that patient symptom severity correlates with EBF3 missense variants perturbing the ZNF, which is a key protein domain required for stabilizing the interaction between EBF3 and the target DNA sequence. We found that ZNF-associated variants failed to restore viability in the fruit fly and impaired transcriptional activation. However, the recurrent variant EBF3 p.Arg209Trp in the DBD is capable of partially rescuing viability in the fly and preserved transcriptional activation.

INTERPRETATION

We describe a symptom severity risk association with ZNF perturbations and EBF3 loss-of-function in the largest reported cohort to date of EBF3-related NDD patients. This analysis should have potential predictive clinical value for newly identified patients with EBF3 gene variants. ANN NEUROL 2022;92:138-153.

Duplication/triplication mosaicism of EBF3 and expansion of the EBF3 neurodevelopmental disorder phenotype

Deleterious variants in the transcription factor early B-cell factor 3 (EBF3) are known to cause a neurodevelopmental disorder (EBF3-NDD). We report eleven individuals with EBF3 variants, including an individual with a duplication/triplication mosaicism of a region encompassing EBF3 and a phenotype consistent with EBF3-NDD, which may reflect the importance of EBF3 gene-dosage for neurodevelopment. The phenotype of individuals in this cohort was quite mild compared to the core phenotype of previously described individuals. Although ataxia tended to wane with age, we show that cognitive difficulties may increase, and we recommend that individuals with EBF3-NDD have systematic neuropsychological follow-up.

Envisioning treating genetically-defined urinary tract malformations with viral vector-mediated gene therapy

Human urinary tract malformations can cause dysfunctional voiding, urosepsis and kidney failure. Other affected individuals, with severe phenotypes on fetal ultrasound screening, undergo elective termination. Currently, there exist no specific treatments that target the primary biological disease mechanisms that generate these urinary tract malformations. Historically, the pathogenesis of human urinary tract malformations has been obscure. It is now established that some such individuals have defined monogenic causes for their disease. In health, the implicated genes are expressed in either differentiating urinary tract smooth muscle cells, urothelial cells or peripheral nerve cells supplying the bladder. The phenotypes arising from mutations of these genes include megabladder, congenital functional bladder outflow obstruction, and vesicoureteric reflux. We contend that these genetic and molecular insights can now inform the design of novel therapies involving viral vector-mediated gene transfer. Indeed, this technology is being used to treat individuals with early onset monogenic disease outside the urinary tract, such as spinal muscular atrophy. Moreover, it has been contended that human fetal gene therapy, which may be necessary to ameliorate developmental defects, could become a reality in the coming decades. We suggest that viral vector-mediated gene therapies should first be tested in existing mouse models with similar monogenic and anatomical aberrations as found in people with urinary tract malformations. Indeed, gene transfer protocols have been successfully pioneered in newborn and fetal mice to treat non-urinary tract diseases. If similar strategies were successful in animals with urinary tract malformations, this would pave the way for personalized and potentially curative treatments for people with urinary tract malformations.

Urofacial (ochoa) syndrome: A literature review

The Urofacial or Ochoa Syndrome (UFS or UFOS) is characterized by an inverted facial expression (those affected seem crying while smiling) associated with lower urinary tract dysfunction without evident obstructive or neurological cause. It is associated with autosomal recessive inheritance mutations in the HPSE2 gene, located at 10q23-q24, and the LRGI2 gene, located in 1p13.2; however, in up to 16% of patients, no associated mutations have been found. Recent evidence suggests that these genes are critical to an adequate neurological development to the lower urinary tract and that the origin of the disease seems to be due to peripheral neuropathy. There is clinical variability among patients with UFS and not all present the classic two components, and it has even been genetically confirmed in patients with a prior diagnosis of Hinman Syndrome or other bladder dysfunctions. Also, the presence of nocturnal lagophthalmos in these patients was recently described. Early recognition and timely diagnosis are critical to preventing complications such as urinary tract infections or chronic kidney disease. Next, the history of Urofacial Syndrome, the advances in its pathophysiology, and its clinical characteristics is reviewed.