Case Report: A Case Report and Literature Review of 3p Deletion Syndrome

4-Phenylbutyrate restored GABA uptake, mitigated seizures in SLC6A1 and SLC6A11 microdeletions/3p- syndrome: From cellular models to human patients

BACKGROUND

Haploinsufficient deletions of GABA transporter 1 (GAT-1)- encoding SLC6A1, and GABA transporter 3 (GAT-3)-encoding SLC6A11 are implicated in epileptic syndromes. Despite their significance, the impact of these deletions has not been characterized. Our previous work on SLC6A1 missense mutations prompted a clinical trial for Ravicti (NCT04937062), a glycerol formulation of 4-phenylbutyrate (PBA), for treatment-resistant epilepsy. We observed phenotypic overlap between trial-eligible SLC6A1 mutation patients and 3p- syndrome patients carrying deletions of SLC6A1 and SLC6A11. This study characterizes the functional impact of these deletions and assesses the urgent question of whether 3p- syndrome patients could benefit from this treatment.

METHODS

Chromosomal microarray analysis identified a deletion affecting one allele of both SLC6A1 and SLC6A11 in two pediatric patients with 3p- syndrome. Clinical phenotyping included electroencephalogram (EEG) recordings and neurodevelopmental assessments. Functional characterization was conducted using 3H-labeled GABA uptake assays and Western blotting in HEK293T cells, comparing haploinsufficient and missense variant models.

RESULTS

The haploinsufficient GAT-1 and GAT-3 conditions demonstrated reduced GABA uptake and protein expression, comparable to known SLC6A1 missense variants. Post-treatment EEGs showed a moderate reduction in epileptiform discharges following PBA administration, and patients exhibited improved motor function. However, varying degrees of cognitive impairments persisted.

CONCLUSIONS

Haploinsufficiency of SLC6A1 and SLC6A11 contributes to the epileptic phenotypes observed in 3p- syndrome, marking this as the first study to biochemically characterize the functional impact of these deletions. Treatment with PBA may provide therapeutic benefits, particularly for addressing seizures and motor deficits, though further exploration of PBA's long-term effects in patients with 3p- syndrome is warranted.

First report of hypoplastic left heart syndrome in 3p- syndrome and review of candidate genes

OBJECTIVE

3p deletion syndrome is a rare monosomal disease that encompasses deletions throughout the short arm of chromosome 3. It is often in the distal region (3p25-pter), but variations in breakpoints and a complex clinical manifestation exist, with congenital heart defects being considered rare. We present the first case of hypoplastic left heart syndrome and minor dysmorphic features associated with 3p- syndrome. Furthermore, we aim to establish a gene-phenotype association.

CASE DESCRIPTION

The diagnosis was made by karyotyping, followed by a literature investigation and in silico bioinformatic analysis about the possible candidate genes associated with congenital heart defects or hypoplastic left heart syndrome in 3p- syndrome. All genes analyzed that could affect heart formation are located in the 3p25.3 region, adjacent to the deleted region in the newborn from our case (3p26). Taking into account the technical limitations of the karyotype and the strength of evidence from each gene evaluated and locus proximity, it is likely that an unidentified partial break in the CAV3 gene occurred.

COMMENTS

We identified an indirect relation between gene CAV3 and hypoplastic left heart syndrome due to its strong association with cardiomyopathies and isolated cardiac defects. Furthermore, the cytogenetic band from our case is new information for the delimitation of a critical cardiac region on 3p syndrome, a discussion that has been ongoing since 1986. Thus, we reinforce the importance of cytogenetic investigation in patients with hypoplastic hearts and dysmorphia, assisting in diagnosis, definition of prognosis, and genetic counseling for the family.

Predominantly unilateral laryngomalacia in infants with unilateral vocal fold paralysis

BACKGROUND

Neonatal unilateral vocal fold paralysis may arise iatrogenically, idiopathically, or in the context of an underlying neurologic disorder. Management is often supportive, focusing on diet modification to allow for safe oral feeding. We describe the clinical course of six infants with unilateral vocal fold paralysis who developed predominantly unilateral laryngomalacia ipsilateral to the affected vocal fold with associated severe respiratory symptoms and feeding difficulty.

METHODS

Retrospective review of six infants with unilateral vocal fold paralysis and predominantly unilateral laryngomalacia. Charts were reviewed for etiology of vocal fold paralysis, presenting symptoms, operative details, postoperative course, and outcomes for breathing and swallowing.

RESULTS

Etiology of vocal fold paralysis included cardiac surgery in four patients, intubation-related in one, and idiopathic in one. Presenting symptoms included increased work of breathing, stridor, feeding difficulty, respiratory failure requiring noninvasive respiratory support, and weak cry. All infants were on nasogastric tube feedings. Direct microlaryngoscopy with unilateral or predominantly unilateral (conservative contralateral aryepiglottic fold division) supraglottoplasty was performed. Stridor and work of breathing improved in all six patients within 1 week postoperatively. Oral feeding improved in three patients within 2 weeks. Three patients had persistent feeding impairment with improvement within one year.

CONCLUSIONS

Predominantly unilateral laryngomalacia may arise in the context of unilateral vocal fold paralysis. Addressing the ipsilateral cuneiform collapse can improve breathing and feeding. This may be an under-described phenomenon and represents an additional reason to include the otolaryngologist early in the care of infants with suspected possible new unilateral vocal fold paralysis. Breathing and swallow can improve post-operatively, but feeding may remain limited by the vocal fold paralysis and any medical comorbidities. Ongoing follow-up and collaboration with speech-language pathology to optimize feeding are important.

Noninvasive single-cell-based prenatal genetic testing: A proof of concept clinical study

OBJECTIVE

To clinically assess a cell-based noninvasive prenatal genetic test using sequence-based copy number analysis of single trophoblasts from maternal blood.

METHODS

Blood was obtained from 401 (243 + 158) individuals (8-22 weeks) and shipped overnight. Red cells were lysed, and nucleated cells stained for cytokeratin (CK) and CD45 and enriched for positive CK staining. Automated scanning was used to identify and pick single CK+ /CD45- trophoblasts which were subjected to next-generation sequencing.

RESULTS

Blood was obtained from 243 pregnancies scheduled for CVS or amniocentesis. Luna results were normal for 160 singletons while 15 cases were abnormal (14 aneuploidy and one monozygotic twin with Williams syndrome deletion). The deletion was confirmed in both fetuses. Placental mosaicism occurred in 7 of 236 (3.0%) Luna cases and in 3 of 188 (1.6%) CVS cases (total 4.6%). No scorable trophoblasts were recovered in 32 of 236 usable samples. Additionally, 158 low-risk pregnancies not undergoing CVS/amniocentesis showed normal results in 133 cases. Seven had aneuploidy results, and there were three likely pathogenic deletions/duplications, including one15q11-q13 deletion.

CONCLUSION

Although the sample size is modest and statistically accurate measures of test performance are not possible, the Luna test detected aneuploidy and deletions/duplications based on concordance with CVS/amniocentesis.

CHL1 depletion affects dopamine receptor D2-dependent modulation of mouse behavior

Introduction

The dopaminergic system plays a key role in the appropriate functioning of the central nervous system, where it is essential for emotional balance, arousal, reward, and motor control. The cell adhesion molecule close homolog of L1 (CHL1) contributes to dopaminergic system development, and CHL1 and the dopamine receptor D2 (D2R) are associated with mental disorders like schizophrenia, addiction, autism spectrum disorder and depression.

Methods

Here, we investigated how the interplay between CHL1 and D2R affects the behavior of young adult male and female wild-type (CHL+/+) and CHL1-deficient (CHL1-/-) mice, when D2R agonist quinpirole and antagonist sulpiride are applied.

Results

Low doses of quinpirole (0.02 mg/kg body weight) induced hypolocomotion of CHL1+/+ and CHL1-/- males and females, but led to a delayed response in CHL1-/- mice. Sulpiride (1 mg/kg body weight) affected locomotion of CHL1-/- females and social interaction of CHL1+/+ females as well as social interactions of CHL1-/- and CHL1+/+ males. Quinpirole increased novelty-seeking behavior of CHL1-/- males compared to CHL1+/+ males. Vehicle-treated CHL1-/- males and females showed enhanced working memory and reduced stress-related behavior.

Discussion

We propose that CHL1 regulates D2R-dependent functions in vivo. Deficiency of CHL1 leads to abnormal locomotor activity and emotionality, and to sex-dependent behavioral differences.

Intellectual developmental disorder with dysmorphic facies and ptosis caused by copy number variation including the BRPF1 gene in Peruvian patient

Background

Intellectual developmental disorder with dysmorphic facies and ptosis (MIM #617333) is a very rare condition, characterized by more than 80% by language delay, intellectual disability, gross motor development delay, broad nasal bridge, hypertelorism, and hypotonia. This condition exhibits as autosomal dominant inheritance and is caused by a heterozygous variant in the BRPF1 gene. Additionally, the copy number variation in the terminal region of chromosome 3p (MIM #613792) has been shown to manifest in most patients as intellectual disability, motor delay, and hypotonia.

Case presentation

We present an 18-year-old male patient with facial dysmorphism, intellectual disability, ptosis, and congenital heart disease. Using chromosomal microarray analysis, a previously unreported 90 kb deletion involving seven genes was found.

Conclusion

When comparing our findings with 39 previous reports, we found that the common clinical features of this syndrome, such as gross motor delay, hypotonia, and congenital spinal cord abnormalities, were not observed in this patient. From the seven genes implicated in the deletion, only BRPF1 could be strongly correlated with the phenotype, according to its function and haploinsufficiency coefficients.

Porokeratotic eccrine ostial and dermal duct nevus associated with an 11 megabase 3p deletion

Porokeratotic eccrine ostial and dermal duct nevus (PEODDN) is a rare eccrine hamartoma; the etiology is incompletely understood. A patient presented with congenital, widespread PEODDN. Clinical assessment, histopathologic, cytogenetic, and molecular genetic investigations on affected cells were pursued. Histopathology confirmed PEODDN, and chromosomal microarray on affected tissues identified a mosaic 3p26.3p25.3 deletion in affected tissues. This 11Mb deletion encompasses 47 OMIM genes. We propose that this and other chromosomal deletions may be implicated in some cases of PEODDN, suggesting locus heterogeneity and underscoring the importance of incorporating cytogenetic and molecular investigations into the multidisciplinary care of individuals with suspected mosaic genetic skin disorders.